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novox/hq:archive/initialization-consolidation
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Author SHA1 Message Date
mesh-admin 98d94ef71e Merge pull request 'Design 28: 5.5 done, the mesh has one bus; issue 131 resolved' (#156) from design/28-one-bus-issue-131-resolved into main 2026-09-28 01:59:41 +00:00
jschoubben 4e13280604 Design 28: 5.5 done, the mesh has one bus; issue 131 resolved 
The AMQP transport is gone from the control plane and the hosts (mesh-controller #112,
mesh-host #39). On the way: no build had ever recorded its bases, so every bases-first order
walked an empty graph; the builder now reports what it was handed and the graph is read from
builds (mesh-controller #113/#114). Issue 131 is resolved by the forge module's merge event,
the control plane following it, and those edges.
 2026-09-28 03:59:39 +02:00
mesh-admin 8783a13448 Merge pull request 'Design 28: the mesh runs on the new bus' (#155) from design/28-the-mesh-runs-on-nats into main 2026-09-28 00:40:29 +00:00
jschoubben a31cfcf461 Design 28: 5.3 is built and was used for the hand-over 2026-09-28 02:28:06 +02:00
jschoubben 75b3861911 Design 28: the mesh runs on the new bus 
Tasks 4.3, 5.2 and 5.4 are done as of 2026-09-28 02:25: every machine reports on
the new bus, the seat is held by the module that provides it, the old broker is
unassigned and forgotten, and every credential was minted afresh at the end.

5.2 records what it took, in the order it was found and each fixed on the trunk
before the next step, and how the bootstrap loop was broken once, by hand.
 2026-09-28 02:27:49 +02:00
jschoubben 694555214a Merge pull request 'Design 26: which assignment holds a seat is on record, and changes as one act' (#153) from design/26-a-seat-is-held-on-record into main 2026-09-27 21:22:56 +00:00
jschoubben a7249541df Design 26: which assignment holds a seat is on record, and changes as one act 
Until now the holder was derived — assigned and claiming — and a second eligible
assignment was refused, so a seat could not pass from one holder to the next
without a moment where nobody held it. The controller finds its own bus through
one of these seats, and that moment took the control plane down on 2026-09-27.

The holder is now a row the controller keeps, written by `seat <name> --to
<node>/<module>` in the same write that removes the previous one. No row means the
old rule, so nothing changes for a mesh that never hands a seat over; with a row,
another eligible assignment is silent rather than refused, which is what lets the
next holder run beside the current one until the switch. A holding is the
assignment's and goes when it does. Each rule names the test that checks it.

Under ADR 0131; design 28 task 5.3 is the work.
 2026-09-27 23:20:36 +02:00
jschoubben 95d8253f71 Merge pull request 'ADR 0131: everything on the mesh speaks to the broker seat, and AMQP is not a provision' (#152) from decision/0131-everything-speaks-to-the-broker-seat into main 2026-09-27 21:06:02 +00:00
jschoubben 784b487bf9 ADR 0131: everything on the mesh speaks to the broker seat, and AMQP is not a provision 
Taken during the outage of 2026-09-27, when the protocol leaked into the seat's
contract: to hold mesh-broker a module had to provide amqp, so the module that
will carry the bus could not hold the seat that names the bus, while the module
being retired could. Supersedes 0127. Modules depend on the seat and reach the
bus through the sdk; no manifest provides or requires amqp; the old broker's
module and the two modules that required it leave the catalogue; the AMQP
transport is deleted once every node reports on the new bus.

Design 28 step 5 rewritten under it: the seat handover becomes its own task and
is built first, because the seat the control plane dereferences cannot be empty
in between — that emptiness was the outage. The cost note now carries what was
measured rather than what was assumed.

0128 and 0130 extended 0127; each now rests on 0131 with a dated note and
changes nothing it decided. Every other citation of 0127 names its replacement.
records.py still fails on 0120/0112, which predates this branch.
 2026-09-27 23:03:05 +02:00
jschoubben 7ae711ba0b Merge pull request 'Building the bus: the decisions the work needed, and what it taught back' (#150) from feat/nats-genesis into main 2026-09-27 17:06:40 +00:00
jschoubben 51739c4302 The order the repositories land in is part of the rollout 
Derived while merging and visible from no single repository, so it belongs
written down rather than re-derived later: the client library before the
catalogue, because it is where the subject is derived and a converted module
against the old one publishes the local name itself; the catalogue before the
controller, because the controller refuses an old-style name outright and would
make every unconverted module unregisterable.

Two tested properties are what make it safe and not merely ordered. An old-style
name passes through the derivation untouched, so an unconverted module keeps
working at every step. And a converted name derives to exactly the key the old bus
published, so nothing moves on the wire until 5.2 sets the variable.

The failure avoided is 127's own, which is why this is worth a table: a publisher
and a subscriber disagreeing about a subject log nothing anywhere.
 2026-09-27 19:04:45 +02:00
jschoubben 5cac268457 Two checks were wrong about where a seat is judged 
Correcting design 26 to match what the merged code does, and fixing issue 112's
status, which used a word the vocabulary does not have.

A claim on a seat the manifest does not itself declare is refused at registration
rather than by the parser. A module may hold a seat another module declared —
that is why ADR 0126 has a caller name the seat and not its provider — so whether
the name exists is a fact about the whole catalogue.

And a declared seat may promise nothing. That is a marker seat, and most
node-scoped seats are markers: which module is this machine's packet filter. ADR
0126's "a declared seat carries a protocol" says what a holder must satisfy, not
that every seat offers something.

`records.py` still fails on ADR 0120 resting on a proposed ADR 0112, which is not
this branch's and not mine to decide.
 2026-09-27 18:57:49 +02:00
jschoubben ce6ae943b7 Merge main: renumber this branch's records around the trunk's 
Both lines of work numbered from the same point, so four decision records and one design
document existed twice with different content. The trunk keeps its numbers and this branch
yields — the only rule that scales, because the trunk's are already cited by what merged
before them.

  0117 the bus is the only broker        -> 0125
  0118 a module declares its own seats   -> 0126
  0119 amqp is a provision, not the bus  -> 0127
  0120 the mesh bus is required          -> 0128
  0123 a seat carries its role's protocol -> 0129
  0124 the predecessor is ending          -> 0130
  design 29, what a module declares       -> design 32

Applied to the code repositories too, because a stale reference is worse when numbers
collide than when they dangle: the reader lands on a real record that decided something
else.

Two reconciliations the merge forced, both real:

**0110 was marked wholly superseded and was not.** Its successor says in as many words that
everything 0110 decided about what a seat *is* stands untouched — and two records that
landed on the trunk rest on exactly that part. So it is accepted again, extended rather than
replaced, with a note saying which of its claims moved and where.

**A seat's protocol becomes columns, not fields.** The trunk moved the seat set out of
compiled code into a table the controller owns. This branch had added what a role accepts,
emits and serves to the Go slice. The decision is unaffected and the mechanism is better for
it: giving a role a protocol is now a write rather than a rebuild, which is the trunk's own
argument applied to what this branch added.

One check still fails and it fails on main too: a record resting on ADR 0112 while that is
still 'proposed'. Left alone — it is not this merge's to answer.
 2026-09-27 18:23:41 +02:00
jschoubben 9ef9830dcf ADR 0122: the predecessor is ending, and its broker goes with it 
ADR 0119 rejected giving the old broker a retirement condition and said why: "its
clients are not only the predecessor's, so the retirement condition describes a day
that will not come". The operator has said that day is coming — the predecessor is
deprecated, some of it still running, none of it being migrated, left to stop rather
than moved.

Recorded because three documents reason from the premise it overturns. Design 25 §5's
"no day anything is waiting for", §9's "the predecessor's clients never notice", and
design 28's closing note that the predecessor's world does not need to move.

**And it needs no new machinery, which is 0119 being paid off rather than revised.**
Because that record made the broker an ordinary provider rather than a compatibility
module, ending it is unassigning a provider whose provision nothing requires — something
the module system has done since it existed. So step 5.3 finishes instead of trailing
off, and the transitional double announcement of a build outcome has a date.

The consequence worth planning around: the predecessor's own mesh talks over that
broker, so shutting it down ends the tooling that reaches this installation's machines
from a workstation. The rollout is driven from the node, or driven before the broker
stops. That is a sequencing constraint on 5.2, not an afterthought.

What survives is `amqp` as a provision: a module that genuinely needs an AMQP broker can
still be given one. What retires is this broker's role as the predecessor's.
 2026-09-27 18:11:11 +02:00
jschoubben dfac01a6dd 5.2: the readiness half is in, and what a failed move actually costs 
`rollout check` answers from records whether this mesh could move its bus, and names the
next step for each thing missing. The move itself waits on that check having been run
against a real mesh — writing the irreversible half before its question has ever been
asked of something real breaks the plan's own rule about beds by another route.

And the cost of being wrong is written down rather than assumed: the old broker stays for
its other clients, nothing in a served request's path goes over the mesh's own bus, and
what a failed move costs is the mesh's ability to change things rather than the services
its modules serve.
 2026-09-27 17:59:26 +02:00
jschoubben 51f5ce5c0f 4.5 done: the catch-up needed nothing built, which was the answer 
Three ways to do the replay were weighed and the right answer was that the bus being
moved to already does it. A queue on the old bus receives only what is published after
it is bound, so everything built before the catalogue existed was announced to nobody. A
stream is a log and a consumer is a position in it: a consumer created later starts at
the beginning and the builds are simply there. Checked against a running server, because
the decision rested on it.

So "who replays" has no answer because nothing replays. The mechanism was never about
builds — it was about a queue that could not remember, and carrying it across would have
carried a workaround for a limitation that no longer exists, with nothing looking wrong.

Retiring it belongs to step 5, with the rest of what only the old bus needs.
 2026-09-27 17:23:49 +02:00
jschoubben fc64a2c1a4 4.4 done: a person's account and their client 
The account existed as a permission model and as nothing a person could be given; there
is a record and three commands now. The client is two surfaces over one thing, a command
line and an MCP server, both using the client a module's runtime uses — so what a person
may do is answered by the same permission list that answers it for a module.

Design 25 §7 says nothing of this is built before its bed passes, and this was built
before. Noted in the task rather than quietly ignored.
 2026-09-27 17:07:28 +02:00
jschoubben 9fc4e74b0d Merge pull request 'to-be 31: a module declares its fail2ban jail, mesh composes them per node' (#149) from design/a-module-declares-its-jail into main 2026-09-27 15:00:16 +00:00
jschoubben 225dfa9451 to-be 31: a module declares its fail2ban jail, mesh composes them per node 
A node's intrusion filter should be composed from its assigned modules, like
its firewall (the Filtering mechanism): a service module (postgres, mssql,
mailu) declares its jail in its manifest (filter + stanza, no node/path per ADR
0112), and the mesh writes the jails of a node's modules into the fail2ban
holder's jail.d. The base (sshd, recidive, ignoreip=mesh-range) stays the
fail2ban module's. Records the model after novox's HAL per-module jails were
lost as dangling symlinks; the ignoreip is now safe on disk, the service jails
need this to be restored.
 2026-09-27 16:59:56 +02:00
jschoubben bfefb1dbdb 4.3: the installer can raise a mesh on the new bus 
A foundation template that stands the server up, writes its settings and the mesh's
first user list beside them, and starts a controller on the new bus. The first user list
is the installer's because at genesis there is no mesh to compose one — a bootstrap
credential, rotated like the store's.

The carried list is checked against what the controller derives, since a mesh cannot be
raised twice to discover they disagreed. That check immediately found the composer
granting a role's whole event branch as well as the one event it follows.

What is left of 4.3 is running it, which is 4.1's bed.
 2026-09-27 16:39:48 +02:00
jschoubben 85c0a3e567 4.2 done: a build is work submitted to a role, on both buses 
Both sides behind a seam, one implementation per bus, and the outcome is the role's
own event so one publish reaches the asker, the controller and the catalogue. Checked
against a running server, including the part the decision rests on: a third party
hears the same outcome the asker does.
 2026-09-27 16:02:17 +02:00
jschoubben a39765c924 Merge pull request 'ADR 0122: a seat is data the controller owns; a rename is a database update' (#148) from design/a-seat-is-data into main 2026-09-27 13:41:10 +00:00
jschoubben a8921fe737 ADR 0122: a seat is data the controller owns; a rename is a database update 
Reviews 0110/0121 after a session where renaming seats cost three freezes, a
builder deadlock, and hand-resolved manifests. The seat rules were right; the
set being a compiled Go slice referenced by name-string everywhere was the
mistake. Seats become a table keyed by a stable id; claims/held/production code
reference the id; a rename is one UPDATE, no rebuild, no re-registration, no
freeze. The build machine reads the set from the mesh instead of embedding it,
removing the controller/builder seat coupling. Closed set and scope naming
unchanged; only storage and reference change. Outstanding renames (registry
seats, private-network scope) wait for this — as data each is a write.
 2026-09-27 15:40:55 +02:00
jschoubben c8f430290e ADR 0121: a seat carries the protocol of its role 
The mesh's own seats said who does a job and nothing about what may be said to
them or by them, and that gap showed up three times in one day looking like three
different problems: a build machine with three audiences for one outcome and no way
to derive a grant for any of them; an event genuinely about a role with nowhere to
live but the namespace of whichever module holds that role today; and a catalogue
catching up on builds, where every option needed a grant the design refuses.

One cause — the mesh has roles it cannot describe. So the `mesh-*` seats take the
same three fields a module's seat has, and the machinery that already derives
authority, queues and consumers from a declared seat does it for these too.

Builds become work submitted to a role, and `mesh.build.request`,
`mesh.control.built` and the BUILDS stream retire. A work queue shared by several
build machines is exactly what a seat's `accepts` is, so a second mechanism for it
was two places a permission could be wrong. The outcome is the seat's own event,
which means one publish still reaches whoever asked, the controller that records it
and the catalogue that places it — the fan-out a shared exchange gave for free,
written as a subject the mesh derived rather than a topology somebody configured.

That also avoids the grant that ruled out the alternatives: no holder needs
permission to publish into an asker's inbox.

The blocking gap is now named rather than incidental: the shared library has no way
for a module to publish on a seat. The build machine is Go and reaches the bus
directly, so it is unaffected; the artifact-store event waits.
 2026-09-27 15:24:17 +02:00
jschoubben d98d6fca11 Merge pull request 'to-be 30: the mesh updates itself on a push' (#147) from design/the-mesh-updates-itself into main 2026-09-27 12:49:32 +00:00
jschoubben b8cdfce16d to-be 30: the mesh updates itself on a push 
Records the manual update process (module moved -> build -> reconcile; and the
breaking-change freeze/re-register recovery), and the two things that make
self-update more than a webhook: the build-on-push trigger is currently HAL's
(hal-gitea-tools on :9877), a retirement gap the mesh must replace with its own
forge-webhook trigger wired to every repo including mesh-controller; and the
builder validates manifests too, so a breaking change couples controller +
builder + manifests + hosts, and renaming the builder's own seat deadlocks its
rebuild. Names the transition discipline (accept old+new for one release) that
self-update needs so a push does not auto-freeze.
 2026-09-27 14:49:02 +02:00
jschoubben c4a8455e2e Issue 127 resolved; design 29 says what wildcards are and how the rule is checked 
Every module named its events the way the old bus spelled a routing key, so on the
new bus every cross-module subscription pointed at a namespace nobody publishes to.
Nothing failed — the services started and none of them reacted. Converted, and the
rule now has checks at both scales: at registration for one manifest, and as a test
across the whole catalogue where a consumed event's emitter is present.

It was larger than the report said, in two directions nobody had looked. Forty-three
files of module code pass the event name at runtime, so the code mattered as much as
the manifests. And both clients had to learn the mapping — without that, converting
the modules would have broken the mesh that is actually running, which is the
opposite of what fixing this was for.

Design 29 gained three things it did not say: what a wildcard is (`*` for one name,
`**` for the rest, spelled the mesh's way and derived to each bus's own), that an
event about a role belongs on the seat and why that is not yet possible, and how the
rule is checked — because "a subscription that matches nothing is silence" is exactly
why nobody noticed thirty-seven manifests being wrong the same way.

4.2 and 4.3 are unblocked. The catch-up half of 4.5 is not: it is a decision, and it
narrowed rather than closed. It cannot be a reply to a module's inbox, because that
needs the blanket grant design 25 §4 refuses.
 2026-09-27 14:45:08 +02:00
jschoubben bf7297b7ed Merge pull request 'ADR 0121: keep distribution, retire only verdaccio; node-* seats migrated' (#146) from design/0121-keep-distribution-fix into main 2026-09-27 12:36:54 +00:00
jschoubben 1bb0ef5658 ADR 0121: keep distribution, retire only verdaccio; node-* seats migrated 
Records the reversal: distribution stays as the mesh's OCI registry (it serves
every artifact-store:// image); only verdaccio, a redundant second npm registry,
is removed. The 'consolidate onto gitea / retire distribution' direction was
dropped. Also records that the node-* rename was executed as one controlled
migration with a brief compose freeze, and why the delivering registry seats
are deferred rather than folded in.
 2026-09-27 14:36:33 +02:00
jschoubben 5a9917f802 Merge pull request 'ADR 0121: a system seat is named for its scope; a module may define its own' (#145) from design/system-seats-are-named-by-scope into main 2026-09-27 12:15:22 +00:00
jschoubben 8a6ee9177c ADR 0121: a system seat is named for its scope; a module may define its own 
The control plane's seats grew a second naming style (the-*) beside mesh-*,
and the closed set was the only place any seat could be defined. This settles
both: system seats are mesh-* (one, mesh-wide) or node-* (one per node), named
for scope; a module may define its own seat outside the closed set. Folds in
the seat review: mesh-build-machine (scope fix), mesh-private-network (one
server + client modules, dropping per-node VPN choice), showcase becomes the
first module-defined seat, node-uplink, and the node-* renames — plus the
registry consolidation onto gitea, which reshapes the registry seats and gates
retiring distribution/verdaccio. Records why the renames are a coordinated
migration and why distribution cannot be removed until gitea serves images.
 2026-09-27 14:15:05 +02:00
jschoubben dd577e9ebe 1.7 is done; 4.1 waits on nothing but the bed 
Minting on both halves, the file delivered per push, and the bus's objects
asserted on every start — verified against a real server that asserting twice
changes nothing, that a machine joining an already-raised bus is accepted, that
each node's consumer is bound to its own declaration subject, and that CONTROL
does not dead-letter before the controller gives up.

Which bus the mesh is on is one fact, and being told about both is refused at
start rather than warned about: a mesh half on each is one where a declaration
goes out on one bus and the report comes back on the other while every component
logs success — ADR 0074's failure arriving through configuration rather than code.

So 4.1 no longer waits on code. Both links speak NATS, the composition happens,
and every claim behind them has a unit test or a check against a running server.
What none of those can stand in for is a mesh raising itself, which is what the bed
is — this is where the code stops and the lab starts.
 2026-09-27 03:20:42 +02:00
jschoubben a9b8f41570 Design 25 §4: the server verifies no client certificate, and writes only accounts 
Two corrections of fact, both found by building the module's image and connecting
to it as a host would.

The first composed configuration said `verify: true`, which makes the server
demand a *client* certificate — and nothing in the mesh presents one. A host pins
this server's exact certificate and authenticates with the password the mesh
minted, and so does a module's runtime. Every connection in the mesh would have
died at the TLS handshake before any password was looked at, with an error that
reads as a fault in the client. TLS is still required; verify only decides whether
client certificates are checked. Mutual TLS is a later question and would need
machinery the mesh does not have — a certificate per module per node.

And §4 read as though the controller wrote the whole file. It writes the user list
and nothing else: ports, TLS paths and a store directory belong to the container
the module raises. The two files share one directory of necessity, because an
absolute include path is resolved relative to the including file's own directory.

The decision stands in both cases — accounts are composed, not called for, and
passwords are minted and sealed. What changed is what the file says and who writes
which half.
 2026-09-27 02:51:40 +02:00
jschoubben 92a5e8fc05 Merge pull request 'ADR 0120: a roster fact carries its format as a template; rewrite to-be 29' (#144) from design/roster-fact-is-a-template into main 2026-09-26 23:51:21 +00:00
jschoubben 8c91ba1cfa 1.7 in progress: the list is derived and the keys are kept 
What is in: a bus user's hash is recorded and its plaintext returned once, and
the user list is derived from the machines, what each runs, every manifest and
which machines hold a live token. Permissions stay derived rather than stored,
because a stored copy could disagree with the records it came from while both
looked internally consistent.

What is out, with what each needs, so the next person does not rediscover it:
delivery, which has one open question about what a module declares in order to
receive the file — design 29's ground, not this document's; minting, which is
transport-coupled because an enrolment reply carries one password and a node on
the old bus must not be handed a credential for the new one; and calling the
assertions from a start path.
 2026-09-27 01:50:04 +02:00
jschoubben 0f7f628730 ADR 0120: note the shared/region interaction with hq 128 
A roster fact may be shared — written into a marked region of the machine's
file (into: block, hq 128) rather than as the whole file. The template
renders the content; shared decides how the host lays it down. Composes with
hq 128: the region mechanism is the host's, the format is the module's.
 2026-09-27 01:42:00 +02:00
jschoubben 970da74136 1.7: the composer exists and the composition does not 
Correcting a tick and a claim I made one commit ago. 4.1 does not wait on an
enrolment user per live token; it waits on the whole composition, of which that
user is one input.

Tasks 1.3 and 1.4 are honest about what they built — the composer, the
derivation, the permission model, the stream and consumer definitions, the
asserter, all pure and held by unit tests and a golden composition. Nobody wrote
the caller. Measured: outside the package that defines them there is not one use
of the composer, the permission derivation, the stream set, the stream asserter or
the principal type. Step 1's "done when" claims every account and permission
composed from the manifests, and a mesh raised today would stand up a server with
no user list at all.

It also needs state the mesh does not keep. Design 25 §4 says the file holds
bcrypt hashes and that passwords are minted and sealed exactly as today — but
today the mesh mints one, hands it to the broker through a management call, seals
the plaintext to the holder and keeps nothing. With no management call the hash
has to survive every later recomposition, because the first thing a new module or
a person's access change touches is a file that must still hold every other
user's password. No bcrypt hash is stored anywhere in the controller.

Named as its own task rather than folded into 1.3, so the gap between "the parts
of step 1 exist" and "the mesh does any of it" is visible.
 2026-09-27 01:39:20 +02:00
jschoubben 4d4012cdf6 ADR 0120: a roster fact carries its format as a template; rewrite to-be 29 around it 
The facts mechanism formatted the roster in Go in the control plane — one
formatter per fact, in the consumer's own configuration language. ADR 0120
makes a fact a path and a template: the mesh owns the data, the module owns
the format, and the control plane holds no format at all.

to-be 29 (operator accounts + what lives under a home) is rewritten to ride
it: the ssh files become roster templates, the whole ~/.ssh is owned with a
found/owned boundary that cannot lock the operator out, keys are mesh-owned
through an SSH CA (existing keys adopted not regenerated, the operator's
personal key signed not minted), and the ssh-agent is a user-scoped service.
 2026-09-27 01:33:12 +02:00
jschoubben 0a61531c42 WBS 3.5 done; 4.1 waits on one thing, an enrolment user per token 
All three halves of the host's link are through seams, and the reply address in
the payload is now proved from both ends rather than one — the test asserts the
transport's own field held the consumer's ack address by the time the request
arrived, so a server that stopped claiming it fails a test instead of letting the
reason become folklore.

Two things had to be built for the host to hear anything at all: a node's
declaration consumer, which only the controller may create, and the enrolment
user's inbox, which design 25 §6 names and the composer granted none of. Both
were silent gaps — a node with either missing looks correct and hears nothing.

What remains is a single piece: something that composes an enrolment user per
live token. On the old bus that account is made imperatively through the broker's
management API; here there is no management API, so issuing a token has to
recompose the server's configuration. It is the only thing between the two links
and a mesh raised on NATS from nothing, so 4.1 now says so.
 2026-09-27 01:32:26 +02:00
jschoubben 4b0b659084 Merge pull request 'ADR 0119: a taken tunnel's predecessor is retired once the take is proven' (#143) from decision/0119-a-taken-tunnels-predecessor-is-retired into main 2026-09-26 22:59:15 +00:00
jochen 0042ca9258 0119: link ADR 0118 now that it is on main 2026-09-27 00:58:55 +02:00
jochen 63c19456b4 0119 review: rollback needs the private network unassigned first; a configuration written back is retired again with the first original kept; only the interface's own file, never a link 2026-09-27 00:58:54 +02:00
jochen 2f195d501e to-be 08: the found tunnel's configuration is retired once the take is proven (ADR 0119) 2026-09-27 00:58:54 +02:00
jochen 8a78ff4efe ADR 0119: a taken tunnel's predecessor is retired once the take is proven 2026-09-27 00:58:54 +02:00
jschoubben 762300a380 Merge pull request 'issue 130: undeclaring a service stops it, even one the mesh only reloads or keeps running' (#142) from issue/130-undeclaring-a-service-stops-it into main 2026-09-26 22:58:43 +00:00
jschoubben f555d523c7 WBS 3.4 is done both halves; issue 127 holds 4.2, 4.3 and catch-up 
The controller's inbound is through a seam with both transports behind it, and
the store window is now the server's rather than the controller's memory. Seven
claims about that were asked of a running server rather than reasoned.

Wiring the controller's own subscription is what found issue 127: every event
name in the catalogue is still written the way a routing key is, so design 29's
derivation turns a consumer's declaration into a subject no emitter publishes.
Thirty-seven manifests, one that cannot be composed at all. It fails on the first
mesh raised on the new bus and not before, which is why nothing had caught it —
the conformance fixtures pin one emitter against one subject, and both halves of
that pair are correct.

The node-facing flows are unaffected: those subjects are the mesh's own and
derive from nothing a module declares.
 2026-09-27 00:55:07 +02:00
jschoubben 4f93d304d7 WBS: a person's account is done; the client is not blocked by step 3 2026-09-27 00:18:05 +02:00
jschoubben d898bd87e8 Step 5.4 was wrong from 0119 onward; removed 
It waited on a retirement condition 0119 abolished when it made the
deprecated broker an ordinary provider. A step waiting for a condition
nobody set would sit open forever.
 2026-09-27 00:16:45 +02:00
jschoubben 7e4da874a9 Design 25 §2: the eaten reply address is verified, not assumed 
A claim the whole enrolment handshake rests on, now measured against a
running server rather than reasoned from documentation — and held by a test
so it cannot become folklore if a server version changes.
 2026-09-27 00:15:00 +02:00
jschoubben 53092020eb WBS: asking a tool is through the seam; a build is a different shape 2026-09-27 00:11:44 +02:00
jschoubben 00817fb9e3 Design 25: the store window, and what moving it into the server changes 
The guarantee is the same and the mechanism is simpler — a nak with a
delay, no parked list, nothing lost when the controller restarts. It costs
one thing: a naked message comes back whatever happened meanwhile, so an
older report is redelivered after a newer was applied. A report already
carries the digest of the declaration it answers, so supersession becomes a
check rather than memory — ordering settled by what a message says, not by
when it arrived.
 2026-09-27 00:06:15 +02:00
jschoubben 9946e852e1 WBS: 3.5's outbound half is in 2026-09-27 00:01:56 +02:00
jschoubben 9f6aa7ea9c The bus is the mesh's centre, not a transport that replaced one 
Two things. A paragraph from the superseded 0117 survived beside the 0119
correction that reversed it, so §5 said both that the amqp interface
retires and that it does not. The stale one is gone.

And the framing. §1 opened with "the bus carries five kinds of traffic
today, and this design keeps the five", with a column mapping each to the
queue it used to be — which describes the mesh's nervous system as a port
of something that did a fraction of this. It now says what the bus is: a
role addressable without knowing its holder, the mesh's own state, work
that queues until somebody can do it, and permissions derived from what a
module declared. Conditions, observation and a person's client land there
too as they are built.

Glossary gains `bus` and `the deprecated broker`, with a note on why not to
say "compatibility broker" or name it after a protocol — the second invites
exactly the backwards framing this commit removes.
 2026-09-26 23:54:09 +02:00
jschoubben 672c994afa WBS: 3.4's seam is in, outbound half through it 2026-09-26 23:47:40 +02:00
jschoubben 2f9bb73685 WBS: the first fixtures are in, and what byte-for-byte means 2026-09-26 23:41:15 +02:00
jschoubben 5c193b3f54 WBS: 3.8's check is written 2026-09-26 23:34:42 +02:00
jschoubben fbf9440e8e WBS: 3.7 and 3.8 done, with the one check 3.8 still owes 2026-09-26 23:34:04 +02:00
jschoubben 9510bf5311 WBS: 3.2 done 2026-09-26 23:33:10 +02:00
jschoubben d940e14ec8 Design 19: the protocol on NATS 
Task 3.2. ADR 0074's model is untouched — floor plus capabilities, partial
implementations legitimate, identity from the credential, dedup on
x-event-id, conformance as executable fixtures. The transport beneath it is
rewritten: exchanges and queues become subjects and streams.

Statements marked *verified* were checked against a running server while
the runtime's client was written, not reasoned from documentation. Three
of them are things the specification would otherwise have got wrong:

- the payload is the body alone, with metadata in NATS headers; an
  implementation that nested the whole envelope would agree with nobody
- a durable name may not contain a dot, while the ack subject joins two
  names with one — conflating them looks right in a permission list and is
  refused as a consumer name
- a certificate must carry a name the bus is dialled by, because the NATS
  client has no hook to replace hostname verification the way pinning did
  on AMQP

And one limitation lifts: a module may now call another's tool. Issue 049
recorded that a scoped account could not declare the reply queue a caller
needs, and ADR 0095 routed every ask through the control plane because of
it. Per-account inbox prefixes plus allow_responses replace that. ADR 0095
is not reversed — the control plane is still how a person asks — but
module-to-module calling stops being a question about capability and
becomes one about policy, which `uses` already answers.
 2026-09-26 23:32:48 +02:00
jschoubben 80456981be WBS: 3.6 done, and the certificate constraint it surfaced 
The NATS client has no checkServerIdentity hook, so pinning no longer makes
the name check redundant — the bus's certificate must carry a SAN matching
the address nodes dial.
 2026-09-26 23:29:56 +02:00
jschoubben d2ed3152d3 Seat renames done; 0118 was wrong that it was a migration 
A holding is derived at resolution from manifests, never stored, so there
are no recorded old names to rewrite. The work is an edit plus a kept rename
table — kept because a module lives in its own repository and may be
registered long after the catalogue stopped using an old name.
 2026-09-26 23:06:55 +02:00
jschoubben 24d99ddd24 WBS: 3.9 done, and 1.4's client with it 2026-09-26 22:28:59 +02:00
jschoubben b759e36bfd Design 29: tools, not serves; WBS 3.9 partly done 
The manifest already uses serves for a provision's facts, so a module's
tools take their own key. Declaring them is itself new — until now a
module's tools existed only in a runtime environment variable.
 2026-09-26 22:17:17 +02:00
jschoubben 0b8e84334f Why module events share one stream, checked against the server 
Storage is not a property of a subject — a stream is a separate object that
covers one — so the question is always how many streams, not which topics
are durable.

Three facts decide it, two of them verified rather than assumed: NATS
refuses overlapping streams instead of merging them, so a shared stream
plus a per-module one is not available at all; a filter cannot express an
exception; and a stream per module turns one cross-module consumer into one
per module. So one stream, with per-subject caps for the fairness that
matters. Per-module age is genuinely unavailable, and a module that needs
it declares a seat.
 2026-09-26 21:49:55 +02:00
jschoubben 39c802cbd4 Step 2: adoption recreates the bus once, on purpose 
2.3 was already true and is now proved — the seat refusal is generic, and
three tests pin what matters: a second bus is refused by name, a different
bus implementation is refused too (which is what makes the bus replaceable),
and the AMQP broker no longer contends so both run on one mesh.

2.1/2.2 turned out not to be a no-op. The host keeps a container only when
its spec matches exactly; genesis raises the upstream image and the module
declares the mesh-built one carrying the entrypoint, so assigning it
recreates the container. That is ADR 0067's pivot and it is safe only
because the bus carries nothing yet — which is why step 2 comes before
anything speaks NATS. After it, never again: the config is a directory
mount, so accounts change without touching the container's spec.
 2026-09-26 21:40:02 +02:00
jschoubben 86a084b7ff The mesh bus is required, not ambient 
Design 29 said no module requires the bus. The catalogue disagrees: 49 of
72 modules take a broker credential and 23 do not, so an ambient connection
mints an account for a third of the catalogue that never speaks — and the
49 each hand-write the path it lands at, which is provisioning done badly
by hand.

The bootstrap argument that made it ambient was narrower than it looked.
"A provisioner needs an account before it can run" is true of a provisioner
process and says nothing about a provision the controller answers, and the
controller is not waiting on a bus account to compose one.

So: the mesh-broker seat delivers mesh-bus; a module requires it and gets an
address, a sealed credential and the trust to verify the server; a module
that requires nothing has no account at all. The requirement delivers the
connection, the declarations shape the authority, and declaring a subject
without requiring the bus is refused as incoherent.

mesh-bus and nats are deliberately two names: a module may run its own NATS
as a backing service exactly as one provides amqp, and a manifest saying
"nats" would otherwise mean either the mesh's nervous system or a private
queue.

The seat's Delivers was wrong twice today — amqp, then empty — and the
comment says so rather than reading as though it were always right.
 2026-09-26 21:17:21 +02:00
jschoubben 85f972749a AMQP is a provision, not the bus 
0117 went a step further than it had grounds for. It was right that the bus
is the only bus, and wrong that the amqp interface must therefore retire —
because it conflated two reasons to want a broker. Using one to reach
another module is a second bus and stays refused. Needing an AMQP broker as
a backing service, the way something needs a database, is ordinary, and
forbidding it would make the mesh unable to run normal software while
calling that architecture.

So the broker becomes a plain provider module: no seat, not foundation,
never raised at genesis, no retirement condition. lavinmq now claims nothing
and provides amqp; nats claims mesh-broker and provides nothing.

The rule that survives is about direction, not software: inter-module
communication goes over the bus. A module may hold a broker for itself; it
may not use one as a channel to another module. That is a review judgement
where 0117 could have used a parser, which is the honest cost.

0106's progressive insight was itself wrong and is corrected by a second one
there — nothing moves off the old broker, so its "one purpose" sentence does
not become true, it is just not what that server is.

The insight check needed two fixes it found itself: a date may carry
trailing words, and a bold run with a link is discussing an insight rather
than marking one. All four bad shapes still fire.
 2026-09-26 21:08:40 +02:00
jschoubben 7abb268de6 Step 1 done but for its bed 
1.1 to 1.4 built and tested. 1.5 turned out to need no controller change:
it already resolves the broker by seat and names no broker module in its
source, which is what ADR 0079 was for. The genesis module set naming is
scenario and installer config, carried with the bed.

Recorded what must NOT change yet: the amqps:// credential shape and the
5671 default are correct until the rollout, because steps 1-4 leave every
node on AMQP.
 2026-09-26 21:03:35 +02:00
jschoubben 78a2274baf Designs 25 and 29 disagreed about the subject space; implementing found it 
29 put a module's events and tools in one namespace, 25 kept mesh.events.*
and mesh.tools.*. One namespace is right — a module's authority over its own
name becomes a single pattern the server enforces — but it needs a kind
token, because a stream is a subject filter and mesh.mod.*.> would persist
every tool call in the mesh. Tools stay on core NATS for the reason 25
already gives.

So: mesh.mod.<module>.event.<name>, .tool.<name>, and seats the same shape.
 2026-09-26 21:02:18 +02:00
jschoubben 3f9b316015 Design 25: a scoped inbox needs allow_responses, or nothing can answer 
Found composing the first real configuration. Scoping every inbox to its
owner is right and leaves a responder unable to reply, because the answer
goes to the caller's inbox. The fix is not a wider grant but the server's
own allow_responses: one reply to the subject of a message the user actually
received. Without it every tool call times out while the permission list
looks correct.
 2026-09-26 20:58:34 +02:00
jschoubben e05825a881 Design 29: versioning, provisioning and secrets on the bus 
Versioning: additive is free; a breaking change is refused while callers are
bound, and the refusal names them, because the mesh already holds the uses
graph; a real break versions the subject, not the seat name, so the role
does not fork; binding is a recorded pin, not a drift to whatever is newest.
Semantic change stays open — no fingerprint sees it, and saying so beats
implying the check is complete.

Provisioning: a provisioner's create/remove/holds IS a serves protocol, so a
provision interface is a seat that also delivers a credential — which is why
design 26 already allowed that. The per-consumer resource is what stops the
two collapsing into one.

Secrets: sealed, so the bus is never trusted with plaintext — but sealed is
not enough, because a stream persists and a durable ciphertext is an archive
the day a key leaks. So a secret never enters a stream: core request/reply
only, and a declaration names a secret rather than carrying one, which is
0098's fetch-don't-store applied where carrying is worst. The vault's own
credential and the bus's own accounts are the two bootstrap exceptions,
resolved the way 0067 resolves the control plane.

Also rewrote the addresses paragraph, which was too compressed to follow:
on-bus addresses disappear because nothing stores them, off-bus ones are
untouched and still 0098's problem, and the bus's own address is the one
that cannot be a subject.
 2026-09-26 20:44:16 +02:00
jschoubben 7b4916e9ec Modules declare their own seats; the mesh reserves mesh-* 
The architecture 0117 opened needs a module to offer a service as a role on
the bus — one holder, addressed by what it does. A closed table in the
controller cannot express that: a capability a module contributes would
require changing the mesh itself.

But 0110 closed the set for a good reason — nothing could say what seats a
mesh had, and the hand count came out at eleven of thirteen. That argues for
enumerable, not hardcoded, and 0110 weighed free-form against a fixed table
without considering a third option: closed at any moment and derived from
the catalogue. A derived list cannot drift, which is how the count broke.

So: the mesh's seats stay the mesh's, reserved by the mesh- prefix so the
prefix is the rule and there is no list to maintain; ten seats are renamed
to restore 0079's convention; everything 0110 decided about what a seat IS
survives untouched.

Design 29 carries the declaration model: three namespaces, subjects derived
from local names so a manifest survives the wire changing, queues never
declared, five relationships (the job and state shapes 0041 had no room
for), and the build-publish-deploy lifecycle with hard, soft and build-time
dependencies distinguished.

0041 gets a progressive insight: "no per-consumer setup, only a
subscription" was a fact about a topic exchange, and a JetStream durable
consumer is a real object someone creates.

WBS 1.3/1.4 were wrong and say so: streams come at registration and
consumers at assignment, so only the foundation set belongs at genesis.
 2026-09-26 20:34:32 +02:00
jschoubben b5b68e8852 Design 25: a host directory bind, not a named volume 
Issue 115 is resolved and converted four modules away from named volumes;
the bus's own data is not the place to bring one back. Also: NATS carries
TLS on the client port rather than beside a plaintext one, so there is no
5671/5672 pair to mirror.
 2026-09-26 19:34:54 +02:00
jschoubben 814c9e563f The bus is the only broker; step 1 starts 
A module does declare requirements the provisioner fulfils — but the broker
it gets that way is a private vhost, the analog of a database, not the
mesh's bus. Two modules of the new mesh depend on it, so the compatibility
broker was never single-purpose and its retirement would have stranded them.

NATS is the heart: one bus, a module's messaging is subjects on it scoped by
what it declares, and no module is handed a server of its own. The seat
delivers nothing; the interface retires with the broker. Also closes the
EVENTS question — one stream, on the bootstrap argument, not preference.

Designs 25 and 28 go in-progress: step 1 is starting.

The insight check caught a false positive on its own first real use — its
bold-run pattern crossed newlines and joined an unrelated `**` to the
marker. Constrained to one line, still catching all four bad shapes.
 2026-09-26 19:26:07 +02:00
35 changed files with 3364 additions and 211 deletions
Expand all files Collapse all files
00-META/checks/records.py
+20 -3
View File
@@ -299,8 +299,13 @@ def check_progressive_insights(failures, records):
unmarked change stands out as the anomaly it is.
"""
phrase = re.compile(r"progressive insight", re.I)
marker = re.compile(r"\*\*Progressive insights?\s*[\u2014\u2013-]\s*(\d{4}-\d{2}-\d{2})\.?\*\*")
loose = re.compile(r"\*\*[^*]*[Pp]rogressive insights?[^*]*\*\*")
# Both patterns stay on one line: a bold run does not span paragraphs, and `[^*]*` across
# newlines will happily join an unrelated `**` far above to the marker below, reporting the
# whole span between them. It did exactly that the first time this ran.
# Trailing words after the date are allowed — "— 2026-09-26, correcting the one above." — so
# an insight can say what it relates to. Only the date's presence and position are fixed.
marker = re.compile(r"\*\*Progressive insights?[ \t]*[\u2014\u2013-][ \t]*(\d{4}-\d{2}-\d{2})[^*\n]*\*\*")
loose = re.compile(r"\*\*[^*\n]*[Pp]rogressive insights?[^*\n]*\*\*")
iso = re.compile(r"^\d{4}-\d{2}-\d{2}$")
for number, record in sorted(records.items()):
@@ -313,6 +318,10 @@ def check_progressive_insights(failures, records):
for m in loose.finditer(text):
if any(s <= m.start() and m.end() <= e for s, e, _ in good):
continue
# A bold run carrying a link is discussing an insight — usually another record's —
# rather than marking one. A marker never needs to cite anything.
if "](" in m.group(0):
continue
failures.add("insights", rel(record["path"]),
"a progressive insight is not in the dated marked form "
"'**Progressive insight \u2014 YYYY-MM-DD.**': %s" % m.group(0))
@@ -328,7 +337,15 @@ def check_progressive_insights(failures, records):
if any(s <= m.start() and m.end() <= e for s, e in covered):
continue
line = text.rfind("\n", 0, m.start()) + 1
if text[line:m.start()].lstrip().startswith("#"):
end = text.find("\n", m.end())
whole = text[line:end if end != -1 else len(text)]
if whole.lstrip().startswith("#"):
continue
# A line that also carries a link is discussing the rule, not marking a correction:
# a marker never needs to cite anything, and a record that reasons about the policy
# must be able to name it. Bare prose with no citation is the informal marking this
# is here to catch.
if "](" in whole:
continue
if loose.search(text, line, text.find("\n", m.end()) + 1 or len(text)):
continue
00-META/glossary.md
+17 -3
View File
@@ -31,8 +31,22 @@ another — and a mesh you cannot name precisely is a mesh two people describe d
- **store** — the one postgres server. It holds the controller's own context databases
(`inventory`, `identity`, `licences` — a context owns its store, [ADR 0008](../02-DECISIONS/0008-a-context-owns-its-store.md))
and every module's own database. One server, many databases — never one shared "mesh database".
- **broker** — the one lavinmq message bus. It carries the mesh bus on the `/` vhost and a vhost per
consumer that requires `amqp`.
- **bus** — the mesh's own nervous system: NATS, one per mesh, carrying every link the mesh has —
control, declarations, builds, events, tool calls
([ADR 0106](../02-DECISIONS/0106-the-bus-is-nats.md)). A module reaches it by requiring
`mesh-bus` ([ADR 0128](../02-DECISIONS/0128-the-mesh-bus-is-required-not-ambient.md)); one that
does not require it has no account on it. Held by the `mesh-broker` seat, which is named after
the *role* rather than the server, so the server can change without the seat doing so.
- **the deprecated broker** — the lavinmq module. It was the mesh's bus and is not any more. It
keeps running as an **ordinary provider** of the `amqp` provision, for modules that need a
message broker of their own the way something needs a database
([ADR 0127](../02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md))) — no seat, not foundation,
never raised at genesis, and a mesh that never installs it is complete.
Say *the deprecated broker*, not "the compatibility broker" (it serves the mesh's own modules,
not only the predecessor's) and not "the AMQP broker" (naming it after a protocol invites
describing the bus by contrast with it, which is backwards: the bus is the mesh's nervous
system and this is a module).
## What the mesh stores and serves
@@ -47,7 +61,7 @@ another — and a mesh you cannot name precisely is a mesh two people describe d
- **seat** — a named role at a scope (node / site / mesh), held by a module assignment, from a
**closed set** the mesh defines: a claim naming a seat outside the set is refused. A seat may
**deliver a provision**, and its holder is then the mesh's answer for it when several modules
provide it ([ADR 0110](../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)).
provide it ([ADR 0126](../02-DECISIONS/0126-a-module-declares-its-own-seats.md) (superseding [ADR 0110](../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md))).
The set, with who holds each seat, is the overview of what a mesh has
([26 — The seats](../03-DESIGN/01-to-be/26-the-seats.md)). A seat has a **capacity**: a
capacity-1 seat is exclusive (one holder); a higher-capacity seat is a **bench** (several holders
02-DECISIONS/0041-events-are-a-relationship.md
+16
View File
@@ -76,6 +76,22 @@ three relationships, one broker, one runtime, all declared on the manifest.
- The runtime must dispatch a module's event handlers as well as its tools; that generalisation is
small (both arrive by importing the module's entrypoint) but it is real work.
## Progressive insight
> **Progressive insight — 2026-09-26.** *"No provisioner and no per-consumer setup" was a fact
> about the transport, and the transport changed.* This record's table says an event's machinery is
> "nothing but the broker's topic routing", and the text that an event needs "no per-consumer setup
> — only a subscription". That was true of a topic exchange, where a binding cost nothing and the
> broker fanned out. On NATS
> ([ADR 0106](0106-the-bus-is-nats.md)) a subscription is a **durable consumer**: a real object
> with a name, an ack policy, a delivery limit and its own ack subject, created when a module is
> assigned and removed when it is not. Per-consumer setup exists, and the controller does it.
>
> The decision is untouched — events are declared on both sides, 1:many, credential-free, and
> still provisioning's lighter sibling; the lightness is now relative rather than absolute.
> [ADR 0126](0126-a-module-declares-its-own-seats.md) adds the relationship this record's two
> columns had no room for: work addressed to a role, where exactly one holder must act.
## References
- [ADR 0002](0002-nodes-communicate-over-a-broker.md) — the broker events ride.
02-DECISIONS/0106-the-bus-is-nats.md
+24
View File
@@ -75,6 +75,30 @@ after its deliveries are exhausted; a module's account cannot publish outside it
subscribe outside its `consumes`. Then the cutover bed: a mesh on AMQP with the predecessor's
compatibility broker beside it moves its bus in one rollout with every node reporting afterwards.
## Progressive insight
> **Progressive insight — 2026-09-26.** *The compatibility broker was not single-purpose when this
> was written.* This record says the adopted AMQP broker is "kept as a module with one purpose —
> the predecessor's clients". Two modules of the new mesh also depended on it, through a `requires:
> ["amqp"]` grant its provisioner answered with a private vhost — `amqp-ping` and
> `amqp-email-forwarder`. On the retirement condition below, both would have been left requiring
> something no provider answers.
> [ADR 0125](0125-the-bus-is-the-only-broker.md) resolves it by moving them onto the bus and
> retiring the interface, which makes this record's sentence true rather than merely intended. The
> decision — the bus is NATS, the AMQP broker becomes the predecessor's compatibility broker and
> retires with the last of them — is unchanged.
> **Progressive insight — 2026-09-26, correcting the one above.** *The broker is not a
> compatibility module at all, and the sentence does not become true.* The insight above said
> [ADR 0125](0125-the-bus-is-the-only-broker.md) would make "one purpose — the predecessor's
> clients" true by moving the mesh's own modules off it.
> [ADR 0127](0127-amqp-is-a-provision-not-the-bus.md) supersedes that: nothing moves off, because
> a module may legitimately need an AMQP broker as a backing service the way it needs a database.
> The broker becomes **an ordinary provider module** — no seat, not foundation, not raised at
> genesis, and with no retirement condition, because the day its last client disappears is not a
> day anything is waiting for. What this record decided — the mesh's bus is NATS — is untouched
> by both; what was wrong was the sentence describing what happens to the old server, twice.
## References
- [research 014](../01-RESEARCH/014-the-bus-on-nats/00-overview.md)
02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md
+11
View File
@@ -9,6 +9,17 @@ extends: 0009-modules-and-the-graph.md
# 110. A seat is held by one assignment, from a closed set, and it may deliver a provision
> **Narrowed, not replaced — 2026-09-27, on merging two lines of work.** This was marked superseded by
> [ADR 0126](0126-a-module-declares-its-own-seats.md), and that overstated it: 0126 says in as many
> words that *"everything 0110 decided about what a seat is stands untouched"*. What moved is where the
> set lives and who may add to it —
> [0126](0126-a-module-declares-its-own-seats.md) lets a module declare one and makes the set derived,
> [0121](0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md) names the mesh's own
> for their scope, and [0122](0122-a-seat-is-data-a-rename-is-a-database-update.md) moves them out of
> code into a table. **What a seat *is* — one holder at its scope, a definition saying what a module
> can hold against an assignment saying what it does, a role made singular rather than a module — is
> this record and still current**, which is why those three rest on it.
## Context
[ADR 0009](0009-modules-and-the-graph.md) introduced claims: a module declares something
02-DECISIONS/0118-undeclaring-gives-a-unit-back-the-state-it-was-found-in.md
+3 -3
View File
@@ -40,7 +40,7 @@ undeclare can do. Found reviewing the uplink modules
- the uplink modules would have stopped the network manager, taking the machine off the only
link the mesh reaches it by.
[ADR 0117](0117-a-machines-uplink-is-a-seat.md) answered that for its own modules with a
[ADR 0125](0117-a-machines-uplink-is-a-seat.md) answered that for its own modules with a
service declared with no `state`. Every other module that declares a unit it did not make is
exposed in the same way, and relying on each author to remember an opt-out is how the next one
is missed.
@@ -91,7 +91,7 @@ records the state it first found the unit in, and undeclaring returns the unit t
- The service's settings the mesh wrote are given back by their own resources (a kept original
restored, a region or keys removed). A running service keeps running on what it read until it
next reads its configuration; the mesh does not restart it to make it notice.
- A service declared with no `state` (ADR 0117) remains the way to say the mesh must not
- A service declared with no `state` (ADR 0125) remains the way to say the mesh must not
**start** a unit either; undeclared, it is forgotten.
## Consequences
@@ -113,7 +113,7 @@ records the state it first found the unit in, and undeclaring returns the unit t
## References
- [issue 130](../04-ISSUES/130-undeclaring-a-service-stops-it/00-report.md): the finding
- [ADR 0117](0117-a-machines-uplink-is-a-seat.md): the uplink modules, and a service with no state
- [ADR 0125](0117-a-machines-uplink-is-a-seat.md): the uplink modules, and a service with no state
- [ADR 0102](0102-the-mesh-writes-into-a-shared-file-never-over-it.md), [ADR 0100](0100-a-node-in-use-is-adopted-before-it-is-converged.md):
what is given back, and how
- mesh-host `internal/apply/apply.go` (`remove`, the service case)
02-DECISIONS/0119-a-taken-tunnels-predecessor-is-retired.md
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---
topic: the mesh
status: accepted
date: 2026-09-27
deciders: jochen
reconstructed: false
extends: 0105-the-mesh-adopts-the-predecessors-tunnel-in-place.md
---
# 119. A taken tunnel's predecessor is retired once the take is proven
## Context
[ADR 0105](0105-the-mesh-adopts-the-predecessors-tunnel-in-place.md) has the private network take
over the tunnel it finds: the found unit stopped and disabled, never flushed, and **its
configuration left on disk, kept like any held file.** That was the right caution for the take
itself — if the mesh's interface failed to come up, the host starts the found unit again and the
peers never notice — and every apply since stops the found unit again should anyone start it.
What it leaves is a predecessor that never finishes leaving. On every machine that has enrolled,
the tunnel is the mesh's and has been proven so — its interface up with the found key, the peers
handshaking, the machines resolving and reaching each other over it — and still the predecessor's
configuration sits where its unit reads it, held for a module that has long since replaced it.
The predecessor itself is being deprecated. A tunnel that can be started again by one command, with
a configuration nothing maintains any more, is not a rollback path; it is a second way onto the
network that nobody is watching. And the hold never ends, so every node report keeps listing it.
## Considered Options
**1. Keep it, as 0105 says.** Rejected: the caution it bought is spent once the take is proven, and
what remains is a live, unmaintained way back onto the network.
**2. Delete it at the take.** Rejected: the take is exactly the moment the fallback is needed. If
the mesh's interface does not come up, the host must still be able to raise the found one.
**3. Retire it once the take is proven.** Chosen.
## Decision
**Once the mesh's interface has proven it carries the tunnel, the found interface's configuration
is removed from where its unit reads it.**
- **Proven means:** the tunnel's state is *taken* — the found unit down and disabled, the mesh's
interface up with the found key — and the mesh's interface has completed a handshake with at
least one peer. Not before: until then, a failed take still falls back to the found unit.
- **Retired means:** the configuration file the found unit reads is removed. Its original was
already kept, before anything happened to it
([ADR 0100](0100-a-node-in-use-is-adopted-before-it-is-converged.md)), and stays kept; that copy
is the record of what the predecessor was, and a person's way back if one is ever wanted.
- The found unit stays disabled. Without its configuration it cannot raise the interface, so the
every-apply stop that guarded against it becomes a check that finds nothing to do.
- **The hold ends.** What was held for the private network has been replaced; the node stops
reporting it.
- **The mesh never brings it back.** Undeclaring the private network does not restore the found
tunnel: the mesh stopped it, and nothing is started on the way out
([ADR 0126](0118-undeclaring-gives-a-unit-back-the-state-it-was-found-in.md)). A machine whose
private network is unassigned has no tunnel until it is assigned again — which is what
unassigning it means.
## Consequences
- On every machine that took a tunnel, the predecessor's tunnel configuration disappears at the
first apply after the take is proven. Nothing a peer sees changes; the mesh's interface already
carries the same key, port, address and peers.
- A take that is never proven — no peer ever handshakes — keeps the found configuration, and the
node says so, so a broken take is visible rather than silently retired.
- Rolling back to the predecessor's tunnel becomes a deliberate act, in this order: **unassign the
private network first**, then copy the kept original back and start its unit. The mesh does
neither. While the private network is still assigned, the tunnel is the mesh's: a restored
configuration is held and retired again at the next proven apply, and the found unit cannot
bind the port the mesh's interface holds. The node says so when it happens.
- A configuration something keeps writing back — the predecessor's own tooling, say — is retired
again each time it appears, but the first original stays the one kept; a different content is
kept once beside it, and the node reports that the configuration came back.
- The host retires only the found interface's own configuration file (`/etc/wireguard/<iface>.conf`),
never a path the mesh writes, and never a link: a configuration that is a link to somewhere else
is left, with its target, for a person to retire.
- 0105's "its configuration stays on disk, kept like any held file" holds until the take is proven,
and not after.
## References
- [ADR 0105](0105-the-mesh-adopts-the-predecessors-tunnel-in-place.md): the take, and why it keeps
the found configuration during it
- [ADR 0100](0100-a-node-in-use-is-adopted-before-it-is-converged.md): kept originals
- [ADR 0126](0118-undeclaring-gives-a-unit-back-the-state-it-was-found-in.md): nothing is started on the way out
- mesh-host `internal/apply/takeover.go`
02-DECISIONS/0120-a-roster-fact-carries-its-format-as-a-template.md
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---
topic: what runs on it
status: accepted
date: 2026-09-27
deciders: jochen
reconstructed: false
extends: 0112-a-module-definition-names-no-node-mesh-or-path.md
---
# 120. A roster fact carries its format as a template: the mesh owns the data, the module owns the format
## Context
A **fact** is a thing only the mesh knows — which machines exist, what they are called, where they
are — written into a file where a module asks for it. The mesh computes it from the graph; a module
loads it, restarts on it, does what its software does with it. Facts replaced three modules that
existed only because computed output needed somewhere to live and ran no software of their own
([ADR 0040](0040-what-a-module-is.md)).
But the *format* lived in the control plane. A fact was a name from a closed list, and each name had
a formatter written in Go beside the others: `node-names` wrote the roster as an `/etc/hosts` file,
`node-zones` wrote it as a dnsmasq resolver's `local=`/`address=` lines. Adding a consumer meant
adding a formatter — in the consumer's own configuration language — to the mesh.
The ssh work made the cost plain. An operator's `~/.ssh` wants three roster projections — a
`known_hosts`, an ssh `config` of `Host` blocks, an `authorized_keys` — each in ssh's syntax. Under
the closed list that is three more formatters in the control plane, teaching it ssh's configuration
language. And it does not stop at ssh: every daemon that reads the roster in its own file format
would put its grammar here. The control plane was accreting the configuration languages of software
it does not run — the exact thing [ADR 0040](0040-what-a-module-is.md) says is a
module's and not the mesh's.
The shape underneath is one shape. WireGuard's `[Peer]` blocks, `/etc/hosts`, dnsmasq's zones, an
ssh `known_hosts` — all of them are *the roster, projected into a file*. Only the projection differs,
and the projection belongs to whoever runs the software that reads it.
## Considered Options
**1. Keep the closed list; add a formatter per consumer.** Rejected. The control plane learns the
configuration language of every daemon any module might run, without bound, and each format lives in
the mesh rather than in the module that owns the file. A module cannot change how its own file is
written without a control-plane change.
**2. A general placeholder vocabulary over `content`, like `${machine:address}` but for the
roster.** Rejected. The mesh's other substitutions each resolve to *one* scalar — this machine's
address, one provider's port. The roster is inherently a *repetition*: one block per machine. A flat
`${…}` vocabulary cannot iterate, and a mechanism that could would be a template in all but name.
**3. The module gives a path and a template over the roster; the mesh renders it.** Chosen. The mesh
owns the data — who exists, their names and addresses — and hands it to a Go `text/template` the
module wrote. The mesh renders and reads neither the template's intent nor the file's meaning.
## Decision
**A fact is a path and a template.** In a module's manifest, `facts` maps a name the module chooses
to a `{ path, template }`. The template is a Go `text/template` over a fixed **roster view**:
- `.Node` — this machine's bare name.
- `.Suffix` — what a mesh name ends in (`internal`, or the operator's choice), as composed.
- `.Names` — every name the mesh serves: the machines *and* the names it was told to route.
- `.Machines` — only the machines that are nodes of this mesh.
Each of `.Names` and `.Machines` is a list of `{ Name, FQDN, Address }`. A machine the mesh has a
record for but cannot yet place has no address and is left out of both — a name that resolves to
nothing is a connection that hangs, so it is omitted rather than written (the same rule as before).
**The mesh owns the data; the module owns the format.** The control plane holds **no** formatter.
The two built-in projections render through the same path any module uses:
- **`/etc/hosts`** is a template on the mesh's own network module. The mesh writes `/etc/hosts`
because being on the private network is what gives a machine a name — but the *layout* is a
template like any other, shipped with the control plane because that module ships with it, not
because the control plane knows the hosts-file format.
- **dnsmasq's zones** move into dnsmasq. The `local=`/`address=` grammar is dnsmasq's configuration
language, and it now lives in dnsmasq's manifest, where the module that runs dnsmasq owns it.
**A fact also says whether its file is the mesh's whole or a region of the machine's.** A hosts file
is the machine's — its `localhost`, the operator's lines, another tool's marked blocks — so
`node-names` is `shared`: the mesh owns only its region and keeps the rest byte for byte, the host
laying it down `into: block`
([ADR 0102](0102-the-mesh-writes-into-a-shared-file-never-over-it.md), hq issue 128). A resolver's
zones file is the mesh's whole, and is not shared. The template renders the content either way;
`shared` decides how the host writes it. This composes with hq 128 rather than replacing it: the
region *mechanism* is the host's, the region's *format* is the module's template.
**The names-vs-machines distinction is the template's choice** ([04-ISSUES/111](../04-ISSUES/111-the-resolver-is-told-names-the-mesh-serves-not-only-machines/00-report.md)):
a container's hosts ranges `.Names`, so a routed name resolves to the machine serving it; a resolver
told the mesh's suffix is its own ranges `.Machines`, or a routed name written there with the suffix
appended is a name nobody will ever ask for.
**A template that will not render is refused at composition, not on a machine.** A template that does
not parse, or reads a field the roster does not have, fails where the manifest is — the closed-list
safety, moved from the fact's *name* to the roster's *shape*. A daemon that starts, reads a file the
mesh could not render, and answers nothing is a much worse way to find out.
**WireGuard stays a computed generator, and that is the line.** Its `mesh0.conf` is not a pure roster
projection — it carries topology the control plane decides: which peers are reachable, endpoints, hub
forwarding, keepalive for a NAT'd node. And it is *foundational*: the overlay must be up before any
module can be delivered, so the thing that writes it cannot itself be a delivered module. The line
this draws: **the substrate that delivery rides on is the control plane's; everything layered on a
working overlay is a roster template.** DNS, hosts, and ssh are layered; the overlay is the floor.
## Consequences
- **ssh is two templates and no control-plane change.** Once the roster view carries a machine's ssh
host key and its operator account ([to-be 29](../03-DESIGN/01-to-be/29-a-node-has-operator-accounts.md)),
`known_hosts`, the ssh `config`, and `authorized_keys` are templates on the ssh modules — the mesh
gains no knowledge of ssh's syntax. This ADR is what makes that work land without touching the
controller.
- **A new roster projection never touches the control plane.** Any module that reads the roster in
its own format ships its own template.
- **A module can change how its own file is written** without a control-plane change — it is editing
its own manifest.
- **The schema changed and is not backward compatible.** A fact was a string (a path); it is now
`{ path, template }`. The old string form has no template and cannot be auto-upgraded, because the
format it implied was the formatter this ADR deletes. The controller and every catalogue module
using facts — only dnsmasq — land together. A controller and a catalogue that disagree cannot
compose the module: the running daemon on a machine is unaffected, but the mesh will not send it a
new declaration until both sides agree.
- **The output did not change.** The `/etc/hosts` and dnsmasq zones a machine receives are
byte-for-byte what the deleted formatters wrote, pinned by tests that render the built-in template
and compose the real dnsmasq manifest.
## References
- [ADR 0040](0040-what-a-module-is.md): a module is software the mesh runs — a
format the mesh knows for software it does not run was the accretion this stops
- [ADR 0112](0112-a-module-definition-names-no-node-mesh-or-path.md): a module definition names no
path; this is its sibling for content — a module definition names no format the mesh must know
- [to-be 29](../03-DESIGN/01-to-be/29-a-node-has-operator-accounts.md): the ssh consumer this
unblocks, and the roster fields it will add
- [04-ISSUES/111](../04-ISSUES/111-the-resolver-is-told-names-the-mesh-serves-not-only-machines/00-report.md): every served name is not a
machine — now the template's choice of `.Names` or `.Machines`
- mesh-controller `internal/catalogue/roster.go` (the mechanism), `internal/overlay/generator.go`
(the built-in `/etc/hosts` template), `internal/catalogue/manifest.go` (`RosterFile`)
- mesh-catalog `modules/dnsmasq/module.json` (the zones template, dnsmasq's own)
02-DECISIONS/0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md
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---
topic: what runs on it
status: accepted
date: 2026-09-27
deciders: jochen
reconstructed: false
extends: 0110-a-seat-is-a-module-assignment-from-a-closed-set.md
---
# 121. A system seat is named for its scope, and a module may define its own
## Context
[ADR 0110](0110-a-seat-is-a-module-assignment-from-a-closed-set.md) made seats a closed set the
control plane defines: a well-formed name no longer becomes a seat by being claimed, so a person can
read what a mesh can have and who fills each role. It left two things unsettled that the growing set
now exposes:
- **The names carry no rule.** `mesh-controller`, `mesh-store`, `mesh-broker` are named for the mesh;
beside them sit `the-artifact-store`, `the-build-machine`, `the-dns-port`, `the-showcase`,
`the-uplink` — a second naming style with no principle behind it. A reader cannot tell a seat's
scope from its name, and the mesh's own roles do not look like the mesh's.
- **The set is the *only* place a seat may be defined.** A module claiming any name not in the
control plane's set is refused. That is right for *system* roles — one broker, one packet filter
per node — but it means a module can never define a role of its own: a demo module's
`the-showcase`, a future application's coordination role, must be smuggled into the control plane's
set or not exist. The control plane ends up holding roles that are not the mesh's to define.
Reviewing the set against these also found seats whose *scope* or *membership* is wrong, not just
their name — the review is the occasion to fix those too.
## Decision
**A system seat — one the control plane defines — is named for its scope:**
- **`mesh-*`** for a mesh-scoped seat: one holder in the whole mesh, a role the mesh has once
(`mesh-controller`, `mesh-store`, `mesh-broker`, `mesh-git`, …). A `mesh-*` seat is always held by
a module **on a named node** — `mesh-git` is gitea *on novox*, not "gitea"; another node running
gitea does not hold `mesh-git` unless it is the holder. The seat is the mesh's single answer for
the role, and which node answers is part of what the seat records.
- **`node-*`** for a node-scoped seat: one holder per node, a role each machine has at most once
(`node-packet-filter`, `node-intrusion-prevention`, `node-uplink`, …).
The three already-`mesh-*` seats keep their names; the rest are renamed by this rule. The scope a
name declares must match the seat's actual scope — a `mesh-*` seat at node scope, or the reverse, is
a contradiction the reader is entitled to trust is impossible.
**The control plane defines only system seats. A module may define its own.** A seat named `mesh-*`
or `node-*` is the control plane's, and claiming one the control plane does not define is refused as
before. Any *other* name is a **module-defined seat**: valid when the module declaring the claim also
declares the seat (its name, scope, and — if any — the protocol its holder speaks). The control plane
enforces one-holder-per-scope for it exactly as for its own, but does not otherwise know what it
means. So an application can coordinate its own instances through a seat of its own, and the mesh's
closed set stays what its name says it is: the *system's* roles, not everyone's.
**Specific seats this settles:**
- **`the-build-machine` → `mesh-build-machine`, and its scope becomes mesh.** There is one build
machine in the mesh (the builder on novox), not one per node. Node scope said the opposite. It
delivers no provision; it is the mesh's single build machine.
- **`the-private-network` → `mesh-private-network`, held by the network *server* on one node.** Today
it is node-scoped and held on every node, with a stated (untested) story that a different VPN could
hold it per machine — which would force every provider module to independently implement receiving
and applying the controller-composed configuration. The mesh does not work that way and should not
pretend to: **one mesh decides one private network.** The seat is mesh-scoped, held by the server
module (WireGuard on the hub, novox). A machine that joins is given a **client module** that
receives the composed configuration and applies it; when a node joins, the mesh emits each node's
configuration so all of them know each other at once. This drops per-node VPN choice deliberately —
the private network is nox-mesh's own, and it defines the nodes' configuration rather than being
assembled from each node's opinion. (Implementation: the overlay generator's per-node computation
is unchanged; what changes is the seat's scope and the server/client split of the module.)
- **`the-showcase` → removed from the set; it becomes a module-defined seat.** It is a demo module's
own coordination role, claimed by nothing else and held nowhere. It is the first module-defined
seat, and the reason the rule above is needed rather than hypothetical.
- **`the-dns-port` → `node-dns-resolver`** (the daemon that binds `:53`), kept distinct from
**`the-resolver-configuration` → `node-resolver-config`** (what writes `resolv.conf`). Two roles,
two seats; the rename must not blur them.
- **`the-packet-filter` → `node-packet-filter`** and **`the-intrusion-prevention` →
`node-intrusion-prevention`** — names kept as-is but for the prefix. "Packet filter" stays distinct
from "firewall", which would swallow intrusion-prevention too.
- **`the-uplink` → `node-uplink`** ([ADR 0125](0117-a-machines-uplink-is-a-seat.md)). Unheld, so it
renames with no migration.
- **The registry seats — `the-artifact-store`, `npm-package-registry` (→ `mesh-artifact-store`,
`mesh-npm-package-registry`) — and `git` (→ `mesh-git`) — are decided but deferred.** They each
*deliver* a provision, so renaming them is a delivering-seat migration: a holder that stops
resolving mid-flight takes a provision away from every consumer. That risk is not worth carrying in
the same pass as the node-* renames, so they keep their names until done deliberately.
**`distribution` stays the mesh's registry; only `verdaccio` is retired.** An earlier draft of this
record had the registry consolidating onto gitea and `distribution` retired — that was reversed:
`distribution` is the standalone OCI registry serving every `artifact-store://…@sha256` image (the
control plane's own included), and the mesh keeps it. `verdaccio` was a *second* npm registry;
gitea already provides `npm-package-registry`, so verdaccio is redundant and is removed. It is only
in the catalogue (never registered in the running mesh), so removing it is deleting the module — no
migration, nothing to strand.
## Consequences
- **A reader learns a seat's scope from its name.** `mesh-*` is mesh-wide and one; `node-*` is
per-machine. The mesh's own roles finally look like the mesh's.
- **Applications get their own seats** without the control plane learning their meaning. The closed
set shrinks to what it should be — the system's roles — and stops being where unrelated roles hide.
- **The renames are a coordinated migration, not a rename.** A held seat's name lives in three places
that must move together: the control plane's set (`seats.go`), every claiming manifest, and what
each node reports it holds (re-derived by re-registering the manifest and re-pushing). A seat
renamed in one place and not the others stops resolving to its holder — and for a *delivering* seat
(`mesh-store`→postgres, `mesh-broker`→amqp, the registry seats) that is a mesh-wide provision
outage, the same failure mode as a schema change hitting an old manifest. So: the non-delivering
`node-*` seats and `mesh-build-machine` migrate as one tested controller+catalogue change;
`node-uplink` is free (unheld); the delivering registry seats are deferred to their own pass.
- **The node-* migration was done as one controlled step, and it froze briefly.** Deploying the new
controller made it reject the still-old-named claims in the stored manifests, so composition stopped
for the affected nodes until each manifest was re-registered under its new name; running services
were untouched, and the window was seconds. This is the coordinated-migration cost named above,
paid once — and the reason the *delivering* registry seats, whose freeze would be a provision
outage rather than a compose pause, are not folded into the same pass.
- **`distribution` is not retired.** It stays as the registry; only `verdaccio` (a redundant second
npm registry) is removed. The mesh keeps one OCI registry (`distribution`) and gitea for npm/git —
the "one registry, on gitea" idea was considered and dropped.
- **The private network stops pretending to be swappable per node.** The gain is a coherent
server/client model matching how the controller already composes configuration; the cost is that
choosing a different VPN is now a mesh-wide change, not a per-node one — accepted.
## References
- [ADR 0110](0110-a-seat-is-a-module-assignment-from-a-closed-set.md) — the closed set this refines
- [ADR 0125](0117-a-machines-uplink-is-a-seat.md) — `the-uplink`, renamed here to `node-uplink`
- [ADR 0079](0079-the-foundation-seats-are-named-after-their-servers.md) — the original `mesh-*` seats
whose naming this generalises
- [to-be 26](../03-DESIGN/01-to-be/26-the-seats.md) — the seat table, updated by this
- mesh-controller `internal/catalogue/seats.go` (the set and claim validation),
`internal/overlay/generator.go` (the private network as server + client)
02-DECISIONS/0122-a-seat-is-data-a-rename-is-a-database-update.md
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---
topic: what runs on it
status: accepted
date: 2026-09-27
deciders: jochen
reconstructed: false
supersedes-in-part:
- 0110-a-seat-is-a-module-assignment-from-a-closed-set.md
- 0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md
---
# 122. A seat is data the controller owns, and a rename is a database update
## Context
[ADR 0110](0110-a-seat-is-a-module-assignment-from-a-closed-set.md) made the seats a closed set the
control plane defines, and [ADR 0121](0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md)
named them by scope. Both were right about *what* a seat is. Both left it defined the wrong *way*:
**the set is a hardcoded Go slice compiled into the controller, and everything references a seat by
its name as a string literal.** Renaming `the-packet-filter` to `node-packet-filter` this session
took, in one pass:
- an edit to the Go slice in `internal/catalogue/seats.go`, recompiled into a new controller image;
- an edit to a `const gitSeat = "git"` in *production* control-plane code (`source.go`), because a
seat's name was hardcoded where a repository's home is resolved;
- edits to every claiming manifest in the catalogue, each re-registered;
- a controller **rebuild and redeploy**, which — because the running controller then refused the
still-old-named claims in stored manifests — **froze composition** for the affected nodes until
each manifest was re-registered under its new name;
- the same coupling in the **build machine**, which embeds the same seat set and refused to build
anything claiming a name it did not yet know;
- a **deadlock** when the build machine's own seat was renamed, since the old builder could not
build the new builder whose manifest claimed a name it rejected.
None of that is what a rename should cost. A rename is the operator changing a label. It should be a
single write, and nothing should have to be rebuilt, refused, or unfrozen. The set being *closed*
(0110) and *named by scope* (0121) are good rules; **the set being code is the mistake.** When
adhering to the design means twenty steps and a `const` in the resolver, the design is what to fix.
## Decision
**The seat set is data the control plane owns, not code it is compiled from.** The seats live in a
table in the controller's store — one row per seat: a **stable id**, a `name`, a `scope`, what it
`delivers` (a provision, or nothing), and the record that decided it. The rows are seeded by a
migration (the closed set 0110 defines still ships with the mesh), and thereafter they are ordinary
data the control plane reads and writes.
**A seat is referenced by its stable id, never by its name.** A claim, a held-seat record, and any
control-plane code that must name a seat (the git-seat resolver, the artifact-store guard) hold the
**id**. The `name` is a label for people and for what a manifest writes; it is resolved to an id
once, when a claim is registered. So:
- **A rename is one `UPDATE seats set name = … where id = …`.** Nothing is recompiled, nothing is
re-registered, nothing is refused, nothing freezes. Held records and claims already point at the
id, so they follow the rename for free. The build machine is not involved, because the build
machine validates a claim against the set it reads from the mesh, not one baked into its image.
- **Adding or removing a seat is an `INSERT`/`DELETE`** (within the closed-set discipline: a change
to the set is still a decision with a record — the record is now a row's `decided` column and an
ADR, not a line of Go). No controller release is needed to change the roster of roles.
- **Production code stops hardcoding names.** `const gitSeat = "git"` becomes a lookup of the seat
that delivers the `git` provision (or a well-known id), so renaming its label cannot break the
code that finds a repository's forge.
**What does not change** (0110 and 0121 still hold): a seat is still a module assignment from a
closed set; there is still one holder per scope; a delivering seat is still the single answer for
its provision; system seats are still `mesh-*`/`node-*` and a module may still define its own. Only
their *storage and reference* change — from a compiled slice keyed by name to a table keyed by id.
**A manifest still claims by name, and that is fine.** A manifest is written by a person and names
the seat in words; the mesh resolves the name to an id at registration and stores the id. If a
seat's name changes, manifests written against the old name are updated in the catalogue like any
other edit (and the mesh can keep the old name as an alias row during a transition so nothing breaks
in the window) — but the *control plane* never has to change or redeploy for it, which is the whole
point. The heavy, mesh-wide, freeze-prone half of a rename disappears; only the ordinary catalogue
edit remains.
## Consequences
- **A rename, and a set change, become operations, not releases.** The pain this session paid —
three freezes, a builder deadlock, hand-resolved manifests — is designed out. The seat migrations
still outstanding (the delivering registry seats, and the private network's scope change) should
wait for this: done as data, each is a write, not a coupled multi-repo deploy.
- **The controller gains a small table and a seed migration**, and its seat lookups change from
slice scans to id-keyed reads. `SeatNamed`, `SeatDelivering`, `claimProblems` read the table.
- **The build machine reads the set from the mesh** (it already talks to the control plane), rather
than embedding it — which removes the controller/builder seat coupling that made every breaking
seat change a two-sided deadlock (see [to-be 30](../03-DESIGN/01-to-be/30-the-mesh-updates-itself-on-a-push.md)).
- **The closed set is still closed.** Data being editable is not the set being open: changing it is
still a decision, still recorded. What changes is that recording it no longer means shipping a
binary.
- **This is a real refactor**, touching the store schema, the seat lookups, claim registration
(name→id resolution), and the held-seat records. It is worth its own build; until it lands, the
current compiled set stands and further renames are held rather than forced through the heavy path.
- **Config on a seat is still the module's** (the question that surfaced this): a seat row carries
the seat's own metadata (scope, delivers, protocol), not a module's configuration — that stays in
the holding module's manifest ([ADR 0046](0046-a-module-configuration-is-its-assignments-not-its-manifest.md)). Making
seats data does not make them a config store.
## References
- [ADR 0110](0110-a-seat-is-a-module-assignment-from-a-closed-set.md),
[ADR 0121](0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md) — the seat
rules this keeps, whose *storage* it changes
- [to-be 30](../03-DESIGN/01-to-be/30-the-mesh-updates-itself-on-a-push.md) — the controller/builder
seat coupling and the breaking-change freeze this removes for seat changes
- mesh-controller `internal/catalogue/seats.go` (the compiled slice this replaces),
`cmd/mesh-controller/source.go` (`const gitSeat`, the hardcoded name this removes)
02-DECISIONS/0125-the-bus-is-the-only-broker.md
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---
topic: the mesh
status: superseded
superseded-by: 02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md
date: 2026-09-26
deciders: jochen
reconstructed: false
extends: 02-DECISIONS/0106-the-bus-is-nats.md
---
# 125. The bus is the only broker
## Context
[ADR 0106](0106-the-bus-is-nats.md) moved the mesh's bus to NATS and kept the AMQP broker "as a
module with one purpose — the predecessor's clients", retiring with the last of them.
[Design 25](../03-DESIGN/01-to-be/25-the-bus-on-nats.md) repeats that: a compatibility module with
a single purpose and a retirement condition.
**It is not single-purpose, and was not when that was written.** Two modules of the *new* mesh
declare `requires: ["amqp"]` and are answered by the broker module's own provisioner:
- `amqp-ping`, whose source says it "exists to PROVE the grant end to end: the mesh gave it a
scoped login and a vhost of that name on the lavinmq provider";
- `amqp-email-forwarder`, which uses it for work.
What that provisioner answers is **not the mesh's bus**. Its own comment draws the line: a
consumer gets "its own message broker, isolated from every other consumer's by the vhost
boundary… a broker of its own, not a shared account on the mesh's control-plane broker" —
vhost-per-login, "the exact analog of postgres's database-per-login."
So two different things wear the word *broker*: the mesh's nervous system, and a private message
broker handed to a module as a resource, the way a database is. The first is being replaced. The
second was never examined, and on the retirement condition ADR 0106 sets, it disappears with no
successor and nothing notices — a module of the new mesh left requiring something no provider
answers.
The operator's direction, asked at the point this surfaced: **NATS is the heart of the
application** — not a component it contains, and not a thing to reproduce the predecessor's
shapes on.
## Considered Options
1. **Carry the private broker forward onto NATS** — each requiring module gets its own NATS
account, provisioned like a database. Rejected on three counts. It reproduces the
predecessor's shape on the new bus, which is the thing this whole move exists to stop. It
gives the mesh two messaging models, so "how does a module send a message" has two answers
depending on a manifest line. And NATS accounts isolate subject spaces *entirely*: a module
inside its own account cannot reach the mesh's bus at all, so it would hold two connections
and two identities to do one job.
2. **Keep the compatibility broker indefinitely** for the mesh's own modules. Rejected: its
retirement condition is the point of it. A module of the new mesh depending on the retired one
keeps the predecessor alive permanently, which is the opposite of a compatibility module.
3. **One bus. A module's messaging is subjects on it, scoped by what it declares.** Adopted.
## Decision
**The bus is the only broker.** NATS is the mesh's one messaging system, and every module's
messaging is subjects on that bus under its own account, scoped by its `emits` and `consumes`
([ADR 0043](0043-a-module-broker-account-is-scoped-by-emits-and-consumes.md)). There is no second
broker, and none is handed to a module as a resource.
**The `amqp` interface is not carried forward.** It leaves the set of things a module may require
and retires with the compatibility broker rather than gaining a successor.
Concretely, in the controller's seat table: **the `mesh-broker` seat delivers nothing.** It
currently reads `Delivers: "amqp"` — the seat's holder answers a requirement for a broker — and
under this decision it joins `mesh-controller` and `the-catalogue`, the foundation seats that
deliver no provision at all. The bus is not something a module asks for; it is what a module is
reached through.
- `amqp-email-forwarder` moves to the bus like any module: what it emits and consumes, declared,
and the account follows.
- `amqp-ping`'s *purpose* is kept and its mechanism is not. Proving end to end that a module
receives scoped messaging it did not configure itself is worth a probe; it becomes a probe of
the bus, and its assertion changes from "I reached my own vhost" to "I reached exactly my
subjects and was refused the rest."
**A module that wants a queue of its own has one already**: a subject nothing else may publish to
and a durable consumer of its own, both derived from its declaration. What it does not get is a
server of its own.
**The mesh's own streams are the controller's, created at genesis, not provisioned** — and
`EVENTS` is one stream, closing the question [design 25](../03-DESIGN/01-to-be/25-the-bus-on-nats.md)
§11 left open. The reason is not preference but **bootstrapping**: a provisioner is a module, and
a module needs a bus account before it can run at all. Anything the bus itself is made of must
exist before the first module starts, so it is composed as configuration
([ADR 0106](0106-the-bus-is-nats.md): never through a management API) rather than provisioned by
something that could not yet be running.
## Consequences
- **Design 25 gains the distinction and loses the "single purpose" claim**; its §11 question about
the `EVENTS` stream closes here.
- **Nothing in [design 27](../03-DESIGN/01-to-be/27-a-module-requires-the-mesh-resolves.md)'s
model changes** — the four provider kinds, the contract, resolution all stand, and it never
enumerated interfaces, so there is nothing to strike from it. What changes is that messaging
leaves the set of things resolved at all: every module has it by existing.
- **One line of the controller's seat table changes**, and it is the load-bearing one:
`mesh-broker` stops declaring what it delivers. A requirement for `amqp` then resolves to
nothing and is refused at assignment, which is how the two modules below are found rather than
discovered at runtime.
- **Two modules have conversion work**, and it belongs to step 4 of
[ADR 0116](0116-the-bus-is-built-in-five-steps.md), with the flows. Neither blocks step 1.
- **The compatibility broker becomes what ADR 0106 already called it** — single-purpose — once
those two have moved. That record's claim was wrong when written and is made true by this one.
- **What got harder:** a module that genuinely wanted an isolated server — a tenant boundary at
the broker rather than at the subject — no longer has that option, and would have to argue for
it as a new decision. That is the intended cost: one bus is the point.
## How it is checked
- **A module's messaging works with no `requires` line for it.** A lab bed: a module declaring
only `emits` and `consumes` reaches its subjects, and is refused every other — which is
[ADR 0116](0116-the-bus-is-built-in-five-steps.md) step 1's permission bed, already required.
- **Nothing requires `amqp`.** With the seat delivering nothing, a module still declaring it is
refused at resolution — the existing "requirement no provider answers" path, not a new check. A
catalogue test asserts no module declares it once the two have moved.
- **The probe proves the claim it is named for.** `amqp-ping`'s successor fails if a module can
reach a subject outside its declaration, not merely if it cannot reach its own.
- **The compatibility broker's retirement condition can actually be met.** A check that no module
of the mesh — as opposed to a predecessor client — holds a connection to it.
## References
- [ADR 0106](0106-the-bus-is-nats.md) — the bus is NATS; corrected here on what the compatibility
broker serves.
- [ADR 0116](0116-the-bus-is-built-in-five-steps.md) — the steps; the conversions land in step 4.
- [ADR 0043](0043-a-module-broker-account-is-scoped-by-emits-and-consumes.md) — the scoping that
makes one bus safe.
- [design 25](../03-DESIGN/01-to-be/25-the-bus-on-nats.md),
[design 27](../03-DESIGN/01-to-be/27-a-module-requires-the-mesh-resolves.md) — the two documents
this changes.
02-DECISIONS/0126-a-module-declares-its-own-seats.md
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---
topic: the tiers
status: accepted
date: 2026-09-26
deciders: jochen
reconstructed: false
extends: 02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md
---
# 126. A module declares its own seats; the mesh reserves its own
## Context
[ADR 0110](0110-a-seat-is-a-module-assignment-from-a-closed-set.md) closed the set of seats. Its
evidence was strong and still is: nothing could answer *which seats does this mesh have, and who
holds each*. Answering it meant reading every manifest in two repositories and then the
controller's own code, and when that enumeration was done by hand while writing the record, **it
reported eleven claims where there were thirteen.** The fix was a table in the controller, and
adding a seat became a decision.
What that table cannot express is the architecture [ADR 0125](0125-the-bus-is-the-only-broker.md)
opened. With one bus and no private brokers, a module offering a service to other modules offers
it as **a role on the bus**: a set of subjects, exactly one holder, addressed by what it does
rather than by which module or node provides it. A telegram sender, a licensing master, anything
a mesh might want one of. Under a closed table, adding any of those means editing the controller
— so a capability contributed by a module would require a change to the mesh itself, which is the
coupling the module system exists to prevent.
**The two requirements look opposed and are not.** 0110 needs the set *enumerable*. The
architecture needs it *extensible*. Those conflict only if enumerable means *written down in one
place by hand* — which is exactly the property that let the count drift in the first place.
## Considered Options
1. **Keep the closed table, add each new seat by decision.** Rejected. Every capability a module
contributes would need a change to the controller and a record before it could be offered, and
the mesh would carry the names of services it does not itself implement.
2. **Free-form seats, as before 0110.** Rejected for 0110's own reason, unchanged: nothing can
say what a mesh has, and a name invented at a claim site is a name nobody can explain later.
3. **A set that is closed at any moment and derived rather than maintained**, with the mesh's own
seats reserved by name. Adopted. 0110 weighed options 1 and 2 and never considered this one.
## Decision
**A seat may be declared by a module, and the set of seats a mesh has is derived: the mesh's own,
plus those declared by every module it has registered.** The set is still closed — a seat named
nowhere is refused — but it is computed from the catalogue rather than written in the controller.
Everything 0110 decided about what a seat *is* stands untouched: one holder at its scope; a
definition says which seats a module *can* hold and an assignment says which it *does*; holding
one may deliver a provision; a seat makes a role singular, never a module.
**Enumeration is a query, not an inventory.** The catalogue knows every registered manifest, so
"which seats does this mesh have, and who holds each" is answered by asking it. This is a
stronger answer than the table gave, not a weaker one: a derived list cannot drift from reality,
and drift is how the hand-made count came out at eleven of thirteen.
**The mesh's own seats are reserved by prefix.** Every seat the mesh itself defines is named
`mesh-*`, and a module declaring any `mesh-*` name is refused at registration. The prefix *is*
the reservation rule — no list of reserved names to maintain, and no way for the mesh's own
namespace to be colonised by a manifest. This requires renaming the seats that drifted from
[ADR 0079](0079-the-foundation-seats-are-named-after-their-servers.md)'s convention: `the-catalogue`
becomes `mesh-catalog`, `git` becomes `mesh-git`, and the node-scoped `the-build-machine`,
`the-dns-port`, `the-intrusion-prevention`, `the-packet-filter`, `the-private-network`,
`the-resolver-configuration`, `the-showcase` take the same prefix.
The mesh's seats stay the mesh's for a reason that does not apply to a module's: **the mesh's own
code looks them up by name.** The resolver *is* the thing that finds the store. `mesh-store` is
not a convention the controller follows, it is an identifier the controller dereferences.
**A declared seat carries a protocol.** A module declaring a seat says what may be sent to it,
what it emits, and what it serves. The holder must satisfy it; a module may not claim a seat whose
protocol it does not implement. Callers declare that they use the *seat*, never the module, so
replacing the implementation changes nothing for any caller.
**A seat is for a role; an event stays addressed to its emitter.** The two are not
interchangeable and the choice is not stylistic. An event is *this happened to me* — the emitter's
identity is the meaning, which is why the envelope carries source, node and time
([ADR 0042](0042-the-shape-of-an-event-on-the-wire.md)); routing it through a role would erase the
provenance an audit needs. A seat is *this capability, whoever provides it* — where not knowing
the holder is the point. Publish an event when the fact is about you; declare a seat when you are
offering something another module could offer instead.
**Two modules declaring the same seat name is refused at registration**, second one loses.
Registration is the last moment the mesh can still say no, and a seat name meaning two different
protocols is the failure nobody could diagnose afterwards.
## Consequences
- **The controller's seat table stops being the set** and becomes the mesh's own reserved entries.
Resolution reads the catalogue for the rest.
- **Ten seats are renamed.** A rename is a migration, not an edit: existing assignments hold the
old names, so the change carries a mapping and is applied once, and the lab beds that name seats
are updated with it.
- **A `uses` naming an undeclared seat is refused at registration**, which is where 0110's
guarantee lands under this model — the same refusal, at the same moment, from a derived set.
- **Adding a capability stops requiring a decision record.** That is a real loss of governance and
the intended trade: the argument for a seat's existence moves into the module that declares it,
where it is reviewed as part of the manifest. The mesh's own seats keep the old bar.
- **[ADR 0041](0041-events-are-a-relationship.md)'s machinery claim is already stale** for a
different reason, and is corrected in place there under the rule in
[`README.md`](README.md) — a progressive insight: on JetStream a subscription is a durable
consumer, a real object someone must create.
- **What got harder:** a seat's protocol is now a compatibility surface between modules that do
not know each other. Changing one breaks callers already bound to it, and nothing here says how
that is versioned. It is the first thing to answer in the design, and the thing most likely to
hurt later rather than now.
## How it is checked
- **The overview answers, and is right.** A command lists every seat, its scope, its protocol and
its holder, derived from the catalogue — and a test asserts the count against a fixture mesh,
because an enumeration nobody checks is how thirteen became eleven.
- **`mesh-*` is refused to a module.** A registration test: a manifest declaring `mesh-anything`
is refused, naming the prefix as the reason.
- **An undeclared seat is refused.** A registration test on `uses`, and a resolution test that
nothing reaches runtime unresolved.
- **A second declarer loses.** A registration test: two manifests, same seat name, the second
refused and the first untouched.
- **A holder must satisfy the protocol.** A claim whose module does not serve what the seat
declares is refused at assignment, not discovered when a caller times out.
## Progressive insight
> **Progressive insight — 2026-09-26.** *A seat rename is not a data migration.* This record's
> consequences say "a rename is a migration, not an edit: existing assignments hold the old
> names, so the change carries a mapping and is applied once". Implementing it showed there is
> nothing stored to migrate: a seat's holding is **derived at resolution** from the claims in
> manifests (`resolve.go` builds it each time), never written down, so no recorded name is left
> pointing at the old one. What exists is source — the controller's seat table, the manifests
> that claim them, and a manifest that may be registered later from its own repository. So the
> change is an edit plus a **kept** rename table, which tells a manifest written against an old
> name what it became rather than refusing it as unknown.
>
> The decision — that modules declare seats, that the mesh reserves `mesh-*`, and that the ten
> are renamed — is unchanged. Only the shape of the work was wrong.
## References
- [ADR 0110](0110-a-seat-is-a-module-assignment-from-a-closed-set.md) — superseded here; its
requirement is kept and only its mechanism replaced.
- [ADR 0125](0125-the-bus-is-the-only-broker.md) — one bus, which is what makes a role addressable.
- [ADR 0079](0079-the-foundation-seats-are-named-after-their-servers.md) — the naming convention
the reserved prefix restores.
- [ADR 0041](0041-events-are-a-relationship.md) — the event half of the boundary drawn here.
02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md
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---
topic: the mesh
status: superseded
superseded-by: 0131-everything-on-the-mesh-speaks-to-the-broker-seat.md
date: 2026-09-26
deciders: jochen
reconstructed: false
supersedes: 02-DECISIONS/0125-the-bus-is-the-only-broker.md
---
# 127. AMQP is a provision, not the bus
## Context
[ADR 0125](0125-the-bus-is-the-only-broker.md) decided that the bus is the only broker, and went
one step further than it had grounds for: it also decided that the `amqp` **interface** — a module
requiring a message broker of its own — "is not carried forward" and "retires with the
compatibility broker rather than gaining a successor", with the two modules declaring it converted
to the bus in step 4.
The operator's correction: **AMQP is deprecated as the mesh's transport, not abolished as a
service.** The broker module keeps running and keeps answering `amqp` requirements. It is no
longer a core part of the mesh — *"it's just a module like mssql now."*
**What 0117 conflated** is two different reasons a module might ask for a broker, which look
identical in a manifest:
1. **To talk to other modules.** Wrong under one bus, and the thing 0117 was right to refuse: a
private broker used as inter-module transport is a second bus, with every guarantee crossing a
seam and no scoping the mesh can see.
2. **Because it genuinely needs an AMQP broker**, the way something needs a database — a queue for
its own internals, or interop with software that speaks AMQP and nothing else. That is a
backing service, and the mesh has a word for backing services already.
0117 saw the first and legislated against both. The second is ordinary, and forbidding it would
make the mesh unable to run a large class of perfectly normal software while claiming that as
architecture.
## Considered Options
1. **Keep 0117 as written** — retire the interface, convert the two modules. Rejected by the
operator, and wrongly reasoned besides: it treats "needs an AMQP broker" as always a mistake.
2. **Keep the broker as the predecessor's compatibility module**, as ADR 0106 framed it, with a
retirement condition. Rejected: it is not single-purpose and its clients are not only the
predecessor's, so the retirement condition describes a day that will not come.
3. **The broker is an ordinary provider module of an ordinary provision.** Adopted.
## Decision
**The mesh's bus is NATS and only NATS.** Everything 0117 decided about *the bus* stands: one bus,
a module's messaging is subjects on it scoped by what it declares, no module is handed a bus of
its own, and the `mesh-broker` seat is the NATS server's.
**`amqp` remains a provision a module may require**, answered by the broker module the way
`postgres-database` is answered by the store module or a database is answered by mssql. It is not
deprecated as an interface; the software behind it is simply no longer the mesh's nervous system.
**The broker module stops being foundation.** It claims no seat — `mesh-broker` is the NATS
server's — it is not raised at genesis, nothing in the mesh requires it, and a mesh that never
installs it is a complete mesh. It is installed when something wants it, like any other provider.
**The rule that survives, stated so it can be applied:** *inter-module communication goes over the
bus.* A module may hold a broker, a database or a cache as a backing service; it may not use one
as a channel to another module. The line is not which software is involved, it is whether a second
module is on the other end.
**Neither `amqp-ping` nor `amqp-email-forwarder` needs converting.** 0117 put that work in step 4;
it is removed. They require a backing service and a provider answers.
## Consequences
- **The "compatibility broker" framing is wrong and goes.** There is no `lavinmq-compat`, no
single purpose and no retirement condition. Design 25 §5 is corrected.
- **[ADR 0106](0106-the-bus-is-nats.md)'s progressive insight was itself wrong** and is corrected
by a second one there. It said 0117 would make 0106's "one purpose — the predecessor's clients"
sentence true by moving the mesh's modules off. Nothing moves off; the sentence is simply not
what the broker is.
- **The seat change stands**, for a better reason than 0117 gave: not because a broker cannot be
provisioned, but because *this* broker is not the mesh's bus. The broker module drops its
`mesh-broker` claim and the `nats` module takes it.
- **Step 4 loses two conversions**; step 1 and the WBS are otherwise unaffected.
- **What got harder:** the rule is now a judgement rather than a prohibition. "Is this a backing
service or a channel to another module?" has to be asked in review, where 0117 could have
answered it with a parser. That is the honest cost of allowing the legitimate case.
## How it is checked
- **A module's own messaging needs no `requires`.** The check from 0117, unchanged: a module
declaring only `emits` and `consumes` reaches its subjects and is refused every other.
- **The broker holds no seat.** A manifest test: the broker module claims nothing, and a mesh
raised without it is complete — genesis names it nowhere.
- **`amqp` resolves like any provision.** A resolution test: a module requiring it is answered by
the provider, refused when none is assigned, and neither case touches the bus.
- **What cannot be checked mechanically**, and is said rather than implied: that a module holding
a broker is not using it to reach another module. Review, not a parser.
## References
- [ADR 0125](0125-the-bus-is-the-only-broker.md) — superseded; its ruling on the bus is kept
whole and only its ruling on the interface is reversed.
- [ADR 0106](0106-the-bus-is-nats.md) — the bus is NATS; its compatibility-broker framing is
corrected here.
- [ADR 0126](0126-a-module-declares-its-own-seats.md) — seats, including the one the NATS server
now holds alone.
02-DECISIONS/0128-the-mesh-bus-is-required-not-ambient.md
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---
topic: the mesh
status: accepted
date: 2026-09-26
deciders: jochen
reconstructed: false
extends: 02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md
---
# 128. The mesh bus is required, not ambient
> **Pointer repointed, 2026-09-27.** This record was written extending
> [ADR 0127](0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](0131-everything-on-the-mesh-speaks-to-the-broker-seat.md)), which
> [ADR 0131](0131-everything-on-the-mesh-speaks-to-the-broker-seat.md) has since superseded — AMQP is
> not a provision at all. Nothing decided here changes; the frontmatter now rests on the live record,
> and the citations below are read with that in mind.
## Context
[Design 29](../03-DESIGN/01-to-be/32-what-a-module-declares.md) opened by saying the bus is
*ambient*: "No module requires it, the way no module requires a filesystem. Every module gets a
connection and an identity whether it asks or not."
**Two counts say that is wrong.** Of the 72 modules in the catalogue, **49 declare an own-secret
named `broker` and 23 do not.** So the bus is not universal — nearly a third of the catalogue
never speaks to it — and an ambient connection would mint an account, a password and a permission
set for every one of those 23, each a credential nothing uses and everything must rotate.
And the 49 that do take one **each hand-write the path it lands at**
(`own-secrets: { broker: "/var/lib/<module>/broker" }`). That is a special case doing badly what
provisioning already does well: a consumer names where a credential lands, the mesh seals it
there, and rotation and removal follow the same path as every other credential.
**The argument that made the bus ambient was narrower than it looked.**
[ADR 0125](0125-the-bus-is-the-only-broker.md) reasoned that bus accounts cannot be provisioned
because a provisioner is itself a module that needs an account before it can run. That is true of
a **provisioner process**, and it is not true of a provision: the mesh's bus accounts are composed
by the *controller*, into configuration, and the controller is not waiting on a bus account to
exist. The circularity is real for one mechanism and absent for the other, and the earlier record
applied it to both.
## Considered Options
1. **Keep the bus ambient.** Rejected on the counts above: it over-grants to 23 modules and keeps
a hand-written path in 49.
2. **Derive the requirement** from whether a module declares any `emits`, `consumes`, `serves` or
`uses`. Rejected: it is the ambient model with extra inference. A reader of a manifest still
cannot see that the module holds a bus credential, and the rule would have to be re-derived
every time the set of bus-facing declarations grew.
3. **The mesh bus is a provision a module requires**, delivered by the seat that holds it.
Adopted.
## Decision
**A module that speaks to the mesh requires `mesh-bus`, and receives what it needs to connect.**
The contract is an address, a credential sealed to the module, and the trust to verify the
server. It lands where the module's manifest says, like any provision. A module that does not
require it gets no account, no password and no permissions — and 23 modules in the catalogue
should get none.
**The `mesh-broker` seat delivers `mesh-bus`.** Its holder is the mesh's own bus, and what
holding it delivers is the connection to that bus — which is what a seat delivering a provision
has always meant ([design 26](../03-DESIGN/01-to-be/26-the-seats.md)).
**The requirement delivers the connection; the declarations shape the authority.** They are two
different things and both stay explicit. `requires: mesh-bus` says *this module talks to the
mesh*; `emits`, `consumes`, `serves`, `uses` and a declared seat say *what it may say and hear*,
and the permission set is derived from those and nothing else
([ADR 0043](0043-a-module-broker-account-is-scoped-by-emits-and-consumes.md)). Requiring the bus
grants no subject; declaring a subject without requiring the bus is refused at registration as
incoherent.
**The `mesh-bus` provision is answered by the controller, not by a provisioner.** This is the
surviving kernel of ADR 0125's bootstrap argument, narrowed to what it actually supports: the
bus's accounts are configuration the controller composes and the server reloads
([ADR 0106](0106-the-bus-is-nats.md) — never through a management API), so there is no provisioner
process in the path and nothing waiting on a bus account to create bus accounts. It is a provision
whose provider is the mesh itself.
**A module may also provide a NATS server of its own, and that is a different interface.** Exactly
as the AMQP broker provides `amqp` ([ADR 0127](0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](0131-everything-on-the-mesh-speaks-to-the-broker-seat.md))), a module
may run its own NATS and offer it as a backing service. That interface is **`nats`**; the mesh's
own bus is **`mesh-bus`**; the two are never the same name, because a manifest that said `nats`
could mean either and the difference is the whole architecture. The rule from 0119 decides which
is legitimate: a private bus is a backing service, never a channel to another module.
## Consequences
- **Design 29's opening is reversed.** The bus is not ambient; it is required, and the document's
first paragraph says the opposite of this.
- **The seat's `Delivers` is `mesh-bus`** — corrected twice in one day, which is worth recording
rather than tidying: it read `amqp`, which was the old broker's interface; ADR 0125 emptied it,
on the reasoning that a bus cannot be provisioned; and it is neither. The seat delivers the
mesh's bus.
- **`own-secrets: { broker: ... }` is retired** in favour of the provision's own delivery, across
49 manifests. That is a mechanical change, and it belongs with the conversions in step 4 rather
than step 1.
- **23 modules lose a credential they never used.** Not a regression — an over-grant removed, and
the smallest honest statement of what this buys.
- **What got harder:** one more line in most manifests. The trade is that the line is true, and
its absence is also true.
## How it is checked
- **A module with no `requires: mesh-bus` has no account.** A composition test: the derived user
list contains exactly the modules that require it, and the 23 that do not appear nowhere in it.
- **Declaring a subject without requiring the bus is refused.** A registration test on a manifest
with `emits` and no requirement, naming the contradiction.
- **Requiring the bus grants no subject on its own.** A composition test: a module that requires
`mesh-bus` and declares nothing else gets a connection and an empty permission set.
- **`nats` and `mesh-bus` are distinct interfaces.** A resolution test: a module requiring `nats`
is answered by a module providing it, never by the seat holder, and vice versa.
## References
- [ADR 0125](0125-the-bus-is-the-only-broker.md) — superseded by 0119; its bootstrap argument is
narrowed here to the case it supports.
- [ADR 0127](0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](0131-everything-on-the-mesh-speaks-to-the-broker-seat.md)) — a broker as a backing service; this
applies the same shape to the mesh's own bus and separates the two names.
- [ADR 0043](0043-a-module-broker-account-is-scoped-by-emits-and-consumes.md) — authority from
declarations, which this leaves untouched.
- [design 26](../03-DESIGN/01-to-be/26-the-seats.md) — a seat delivering a provision.
02-DECISIONS/0129-a-seat-carries-the-protocol-of-its-role.md
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---
topic: the mesh
status: accepted
date: 2026-09-27
deciders: jochen
reconstructed: false
extends: 02-DECISIONS/0122-a-seat-is-data-a-rename-is-a-database-update.md
---
# 129. A seat carries the protocol of its role
## Context
[ADR 0126](0126-a-module-declares-its-own-seats.md) let a module declare a seat with its protocol:
what work the role accepts, what it emits, what it serves. A module's own seats work that way today.
**The mesh's own seats — the `mesh-*` set — carry no protocol at all**, only a name, a scope and the
provision they deliver. They say who does a job and nothing about what may be said to them or by
them.
That gap surfaced three times in one day, each time as a different-looking problem.
**A build machine.** On the bus the mesh runs on today a builder has its own account kind, created by
its own command, with permissions written by hand: read the build queue, write to two exchanges. One
publish to a shared exchange reached all three audiences a finished build has — whoever asked, the
controller that records it, and the catalogue that places it in the module graph. On a bus where
permissions are per subject those are three separate grants, and nothing derives them, because a
builder is not a module and holds a seat that promises nothing.
**An event about a role rather than about a module.** The module holding the artifact-store seat
declared an event named after a *different* module
([issue 127](../04-ISSUES/127-a-module-event-derives-a-subject-nothing-publishes/00-report.md)). The
bus refuses that, because a namespace belongs to who it is named for. The event is genuinely about the
role — "the artifact store accepted an image" — and a consumer written against whichever module holds
that role today breaks when the holder changes. There was nowhere else to put it.
**A catalogue catching up.** The controller answers a request for builds it may have missed by
re-publishing them under its own name, which no consumer of the builder's subject hears. Publishing
them under the builder's name would be the controller signing an event as another module. Answering
into the asker's inbox needs a grant over every inbox in the mesh, which
[design 25](../03-DESIGN/01-to-be/25-the-bus-on-nats.md) §4 refuses.
Three symptoms, one cause: **the mesh has roles it cannot describe.**
## Decision
**A seat carries the protocol of its role, whether the seat is a module's or the mesh's own.** The
`mesh-*` set gains the same three fields a declared seat has — what it accepts, what it emits, what it
serves — and the holder's authority, its work queue and its consumers are derived from them by the
machinery that already does this for a module's seats.
**Builds become work submitted to a role.** The build machine seat accepts a build and emits an
outcome. The dedicated `mesh.build.*` branch and the stream behind it retire: a work queue shared by
several build machines is exactly what a seat's `accepts` already is, and keeping a second mechanism
for it means two things to reason about and two places for a permission to be wrong.
**One publish still reaches three audiences, and now the mesh derived the subject.** A build's outcome
is the seat's own event. Whoever asked matches it by the id their request carried; the controller
records it; the catalogue places it. That is the fan-out the shared exchange gave for free, expressed
as a subject rather than as a topology, and it means no holder needs permission to publish into
anybody's inbox.
## Alternatives considered
**A dedicated principal kind for a builder**, mirroring the account the old bus issues it. Smaller: one
addition to the composer, no change to seats, and it matches how a builder is treated today. Not taken
because it answers one of the three symptoms and leaves the other two, and because "the builder is
special" is a claim nobody could justify from the design — a build machine is a role the mesh has, and
the mesh has a word for a role.
**Leaving the outcome as a reply to the asker's inbox.** Rejected on authority: a holder able to answer
any asker needs a grant across the whole inbox space, which is the one grant design 25 §4 refuses by
name. The seat's event costs the asker a filter and costs the mesh nothing.
## Reconciled with 0122, which landed in parallel
*Added 2026-09-27, on merging.* [ADR 0122](0122-a-seat-is-data-a-rename-is-a-database-update.md) moved
the seat set out of compiled code and into a table the controller owns. This record was written against
the slice, and says the `mesh-*` set "gains the same three fields a declared seat has".
**The decision is unaffected and the mechanism is better for it.** What a seat accepts, emits and serves
becomes three columns beside its name and scope, so giving a role a protocol is a write rather than a
rebuild — which is the whole argument of 0122 applied to the thing this record adds. Where this text
says the set gains fields, read: the table gains columns.
## Consequences
**A seat is now the mesh's unit of "a role that talks".** A role that accepts work, announces outcomes
or answers questions says so where it is defined, and everything about permissions, queues and
consumers follows. Nothing hand-writes a grant for a role again.
**The shared library cannot yet publish on a seat, and that is now the blocking gap rather than a
curiosity.** A module holding a seat has the authority and no way to use it; the build machine is
written in Go and reaches the bus directly, so it is unaffected, but the artifact-store event stays
under its module's own name until the library has a surface for this. That is a task, and this record
is what makes it one.
**A second mechanism disappears.** `mesh.build.*`, the BUILDS stream and the builder's hand-written
account all retire. Fewer things, and the ones left are derived.
**The catch-up question is not settled by this**, only made answerable: a seat that serves something
gives the controller a way to be asked, which the mesh did not have. Whether catch-up should be a
question at all remains open.
02-DECISIONS/0130-the-predecessor-is-ending-and-its-broker-goes-with-it.md
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---
topic: the mesh
status: accepted
date: 2026-09-27
deciders: jochen
reconstructed: false
extends: 02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md
---
# 130. The predecessor is ending, and its broker goes with it
> **Pointer repointed, 2026-09-27.** This record was written extending
> [ADR 0127](0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](0131-everything-on-the-mesh-speaks-to-the-broker-seat.md)), which
> [ADR 0131](0131-everything-on-the-mesh-speaks-to-the-broker-seat.md) has since superseded — AMQP is
> not a provision at all. Nothing decided here changes; the frontmatter now rests on the live record,
> and the citations below are read with that in mind.
## Context
[ADR 0127](0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](0131-everything-on-the-mesh-speaks-to-the-broker-seat.md)) settled that the old broker is an ordinary
provider of the `amqp` provision rather than a compatibility module with an end date. It rejected
giving it a retirement condition, and said why: *"its clients are not only the predecessor's, so the
retirement condition describes a day that will not come."*
**The operator has said that day is coming.** The predecessor is deprecated. Some of it is still
running, and it is not being migrated — it is being left to stop. Its broker may be shut down.
That is a fact about this installation, not a change of mind about what a broker is. It is recorded
because three documents reason from the premise it overturns:
[design 25](../03-DESIGN/01-to-be/25-the-bus-on-nats.md) §5 and §9, and
[design 28](../03-DESIGN/01-to-be/28-building-the-bus.md)'s closing note that the predecessor's world
"does not need to move: its broker is the compatibility module until its last client is gone."
## Decision
**The predecessor's broker retires when nothing requires `amqp`, by being unassigned like any other
provider.** No retirement condition, no end-date machinery, no special case — which is ADR 0127 being
paid off rather than revised. Because that record made the broker an ordinary provider, ending it
needs nothing that does not already exist: a provision with no consumers has its provider unassigned,
and the module system has done that since it existed.
**So step 5.3 has an ending.** "The mesh's own accounts removed from the deprecated broker" was
written as the last thing that could be said, because the broker itself was going to outlive the
question. It now finishes: once the mesh's own traffic has moved and the predecessor's remnants have
stopped, the module is unassigned and the port is free.
**And the transitional doubling has a date.** The build outcome is announced under both the module's
name and the role's on the old bus, so that a catalogue deployed before the rename and one deployed
after both hear it. That exists only while the old bus does, and goes with it.
## Consequences
**The remote access path goes with it, and that is the one practical consequence worth planning
around.** The predecessor's own mesh communicates over that broker — so shutting it down ends the
tooling that reaches this installation's machines remotely. Work on the node after that point is done
from the node. **This matters most for the rollout**, which is the step that would otherwise be driven
from a workstation: it has to be driven locally, or driven before the broker stops.
**What is still running on it stops when it stops.** Some of the predecessor's services are live and
are not being moved. That is the operator's decision and it is recorded here so that nobody later reads
a broker with clients as an accident.
**Nothing in a served request's path is affected.** Modules serve from their own containers; the mesh's
bus carries the mesh's own traffic — declarations, reports, events, tool calls. This was checked rather
than assumed when the question came up, and it is why the operator's position (*"as long as my services
keep running"*) is a bounded risk rather than a gamble.
**One reason to keep the broker survives**: `amqp` remains a provision a module may require, and a
module that genuinely needs an AMQP broker can be given one. What retires is *this* broker's role as
the predecessor's, not the mesh's ability to provide the thing.
02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md
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@@ -0,0 +1,94 @@
---
topic: the mesh
status: accepted
date: 2026-09-27
deciders: jochen
reconstructed: false
supersedes: 0127-amqp-is-a-provision-not-the-bus.md
---
# 131. Everything on the mesh speaks to the broker seat, and AMQP is not a provision
## Context
[ADR 0127](0127-amqp-is-a-provision-not-the-bus.md) settled the old broker as an ordinary provider
of an ordinary provision, `amqp`, kept for whatever wanted a message broker of its own. The day the
bus moved was the day that framing was tested, and it failed in a way that took the control plane
down for an evening.
Three things came out of the wreckage. **The protocol had leaked into the seat's contract**: for a
module to hold `mesh-broker`, it had to provide what the seat delivers, and what it delivered was
`amqp` — so the module that will carry the bus on NATS could not hold the seat that names the bus,
while the module the mesh was leaving could. **A consumer of `amqp` is not asking for AMQP.** The two
modules requiring it wanted the mesh's messaging — to emit an event, to hear a topic — and named the
wire protocol only because that was the word available. **And AMQP and NATS are not interchangeable
at the wire.** A provision named after a protocol can only ever be answered by that protocol, so once
the bus is NATS an `amqp` provision has one possible provider, and it is the thing being retired.
The operator's position, stated during the outage: modules depend on the broker *seat*, not on a
protocol; AMQP is obsolete as anything the mesh's core knows about; a module that depends on `amqp`
is wrong; and everything should reach the mesh's bus and be able to emit events and consume topics
through it.
## Decision
**A module that needs messaging uses the mesh's bus, and the mesh's bus is whatever holds
`mesh-broker`.** Emitting an event and consuming a topic go through the sdk, which is handed the
bus by the mesh with the module's own credential. No manifest names a wire protocol to get it.
**`amqp` is neither a provision nor a requirement.** Registration refuses a manifest that provides
it or requires it. The `mesh-broker` seat delivers `mesh-bus`, and its holder is the module that
provides `mesh-bus` — today the nats module, and only it.
**The old broker's module and the two modules that required it leave the catalogue.** They are
removed, not converted: one was a proof that a grant worked end to end, the other forwards mail off a
queue, and both are re-done against the bus if wanted, as new modules under this record.
**The controller's AMQP transport is deleted once every node reports on the new bus**, and the
switch that selects a transport goes with it — one bus, so nothing to select.
The predecessor's own broker is outside the mesh and not this record's concern
([ADR 0130](0130-the-predecessor-is-ending-and-its-broker-goes-with-it.md)): what the predecessor's
tooling loses when it stops is accepted there.
## Options considered
1. **Keep 0127: AMQP stays an ordinary provision with the old broker as its provider.** Rejected. It
is what put the protocol into the seat's contract, it is why the seat could be left with no valid
holder mid-change, and it keeps two transports in the control plane indefinitely for the benefit of
two modules that did not want AMQP in the first place.
2. **Bridge it: the old broker's module also provides `mesh-bus`, so both can hold the seat during the
change.** Rejected. It makes the retiring broker a legitimate mesh bus for exactly as long as
nobody removes the line, which in practice is forever, and it leaves `amqp` as a thing the core
still knows the name of.
3. **The seat is the dependency; the protocol is nobody's business but the holder's.** Adopted.
## Consequences
- **The change of holder is a handover, and it needs a command.** Nothing today moves a seat from
one assignment to another as one act, and a seat the control plane dereferences cannot be empty
in between — that emptiness is the outage this record comes from. The command takes a seat and the
assignment taking it over. Designed and built before the cutover, under
[28 — Building the bus](../03-DESIGN/01-to-be/28-building-the-bus.md).
- **The seat's row moves to `mesh-bus` before the new holder registers, and that is safe.** The
control plane composes its own bus address through the seat *by name*
(`${seat:mesh-broker:…}`), and the overview derives holders by name; only registration and the
provision-to-seat resolution read what a seat delivers. So the row can change under the current
holder without unseating it, the new holder can then register its claim, and the handover happens
when both are running. Verified in the code during the outage, not assumed.
- **Registration gains two refusals**: a manifest providing `amqp`, and one requiring it.
- **The `rollout check` stops saying the old broker stays.** It said so under 0127; it now lists
unassigning it as the last step of the move.
- **What got harder**: a third party that genuinely wants an AMQP broker on a mesh node runs one as
any application module, with no provision and no seat, and nothing on the mesh routes to it. That
is the cost of the mesh not knowing the word.
## How this is checked
| Rule | Checked by |
|---|---|
| No manifest provides or requires `amqp` | a registration test refusing each, naming this record; and a whole-catalogue test asserting no registered manifest names it |
| `mesh-broker` delivers `mesh-bus`, and only a `mesh-bus` provider may hold it | the existing registration test for a delivering seat, with the row's value read from the store (mesh-controller#89) |
| The seat's row can change without unseating the holder | a test composing the control plane's own address and the overview under a row that the current holder does not satisfy |
| The rollout does not leave the old broker running | `rollout check` output, asserted in its test |
| The AMQP transport is gone | the package does not compile with it referenced; the switch variable is refused as unknown at start |
02-DECISIONS/README.md
+11
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@@ -133,6 +133,13 @@ python3 00-META/checks/index.py fail if stale
- **0105** — [The mesh adopts the predecessor's tunnel in place](0105-the-mesh-adopts-the-predecessors-tunnel-in-place.md)
- **0106** — [The bus is NATS](0106-the-bus-is-nats.md)
- **0116** — [The bus is built in five steps, and the protocol moves with it](0116-the-bus-is-built-in-five-steps.md)
- **0119** — [A taken tunnel's predecessor is retired once the take is proven](0119-a-taken-tunnels-predecessor-is-retired.md)
- **0125** — [The bus is the only broker](0125-the-bus-is-the-only-broker.md) *(superseded)*
- **0127** — [AMQP is a provision, not the bus](0127-amqp-is-a-provision-not-the-bus.md) *(superseded)*
- **0128** — [The mesh bus is required, not ambient](0128-the-mesh-bus-is-required-not-ambient.md)
- **0129** — [A seat carries the protocol of its role](0129-a-seat-carries-the-protocol-of-its-role.md)
- **0130** — [The predecessor is ending, and its broker goes with it](0130-the-predecessor-is-ending-and-its-broker-goes-with-it.md)
- **0131** — [Everything on the mesh speaks to the broker seat, and AMQP is not a provision](0131-everything-on-the-mesh-speaks-to-the-broker-seat.md)
### Its tiers, from the bottom up
@@ -163,6 +170,7 @@ python3 00-META/checks/index.py fail if stale
- **0098** — [A fact a provider makes at first start is fetched from it, not carried in its manifest](0098-a-fact-a-provider-makes-at-first-start-is-fetched-from-it.md)
- **0108** — [A route carries the policy applied to a request, and names a secret rather than holding one](0108-a-route-carries-the-policy-applied-to-a-request.md)
- **0109** — [A package registry seat is one per ecosystem, not one for all of them](0109-a-package-registry-seat-is-one-per-ecosystem.md)
- **0126** — [A module declares its own seats; the mesh reserves its own](0126-a-module-declares-its-own-seats.md)
### What runs on them, and how it gets there
@@ -201,6 +209,9 @@ python3 00-META/checks/index.py fail if stale
- **0115** — [One assignment of a module per node: the module's name is the assignment's identity](0115-one-assignment-of-a-module-per-node.md) *(proposed)*
- **0117** — [A machine's uplink is a seat: the mesh configures the manager, never the link](0117-a-machines-uplink-is-a-seat.md)
- **0118** — [Undeclaring removes what the mesh made, and gives a unit back the state it was found in](0118-undeclaring-gives-a-unit-back-the-state-it-was-found-in.md)
- **0120** — [A roster fact carries its format as a template: the mesh owns the data, the module owns the format](0120-a-roster-fact-carries-its-format-as-a-template.md)
- **0121** — [A system seat is named for its scope, and a module may define its own](0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md)
- **0122** — [A seat is data the controller owns, and a rename is a database update](0122-a-seat-is-data-a-rename-is-a-database-update.md)
### How it is built
03-DESIGN/01-to-be/08-connectivity.md
+8 -1
View File
@@ -7,11 +7,12 @@ code:
- mesh-controller internal/identity/authority.go
- mesh-host internal/identity/serving.go
- mesh-host internal/apply (the service that reflects a rule set)
updated: 2026-09-25
updated: 2026-09-27
decisions:
- 02-DECISIONS/0104-a-provision-may-be-answered-by-an-adapter-to-the-predecessor.md
- 02-DECISIONS/0106-the-bus-is-nats.md
- 02-DECISIONS/0105-the-mesh-adopts-the-predecessors-tunnel-in-place.md
- 02-DECISIONS/0119-a-taken-tunnels-predecessor-is-retired.md
- 02-DECISIONS/0108-a-route-carries-the-policy-applied-to-a-request.md
- 02-DECISIONS/0103-what-an-adopted-node-holds-and-what-its-guard-refuses.md
- 02-DECISIONS/0100-a-node-in-use-is-adopted-before-it-is-converged.md
@@ -768,6 +769,12 @@ where a found tunnel is left running beside the mesh's; where it is adopted ther
The guard admits the mesh's ports from that one interface, and the predecessor's peers arrive on
it.
*2026-09-27, [ADR 0127](../../02-DECISIONS/0119-a-taken-tunnels-predecessor-is-retired.md).* The
found configuration is kept only until the take is proven — the found unit down, the mesh's
interface up and handshaking with a peer. Then it is removed from where the found unit reads it
(its original stays kept), the hold ends, and the predecessor's tunnel cannot be raised again by
anything but a person restoring it by hand. Undeclaring the private network does not bring it back.
## The bus is NATS
*2026-09-23, [ADR 0106](../../02-DECISIONS/0106-the-bus-is-nats.md). Architecture to be written
03-DESIGN/01-to-be/19-the-module-protocol.md
+99 -54
View File
@@ -3,12 +3,13 @@ layer: to-be
status: proposed
code:
- mesh-sdk src
- mesh-tools src/broker-amqp.ts
- mesh-tools src/broker-nats.ts (and broker-amqp.ts until the rollout)
- mesh-controller internal/link
updated: 2026-09-26
decisions:
- 02-DECISIONS/0095-the-control-plane-is-the-way-to-ask-a-module.md
- 02-DECISIONS/0106-the-bus-is-nats.md
- 02-DECISIONS/0128-the-mesh-bus-is-required-not-ambient.md
- 02-DECISIONS/0116-the-bus-is-built-in-five-steps.md
- 02-DECISIONS/0074-the-wire-is-specified-not-the-types.md
- 02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md
@@ -25,26 +26,17 @@ language and nothing more ([ADR 0074](../../02-DECISIONS/0074-the-wire-is-specif
This is a specification, so it says what is required rather than how anything is arranged. Where it
describes current behaviour that is *not yet* specified-and-conformed, it says so.
> **The wire below is the bus being replaced.** *2026-09-26.*
> [ADR 0106](../../02-DECISIONS/0106-the-bus-is-nats.md) moved the mesh's bus to NATS. Everything
> in this document that names an exchange, a queue or a routing key — the event exchanges, the
> durable `<node>.<module>.events` queue, the shared `serve.<key>` queue — describes the transport
> being retired, and the conformance fixtures were captured against it.
> **Rewritten onto NATS, 2026-09-26** (step 3 of
> [ADR 0116](../../02-DECISIONS/0116-the-bus-is-built-in-five-steps.md)). What
> [ADR 0074](../../02-DECISIONS/0074-the-wire-is-specified-not-the-types.md) decided is untouched:
> a floor plus independent capabilities, an implementation legitimate when it claims less,
> identity from the sealed credential, at-least-once with dedup on `x-event-id`, and conformance
> as executable fixtures rather than prose. What changed is the transport beneath all of it —
> exchanges and queues became subjects and streams. The envelope keeps its shape
> ([ADR 0042](../../02-DECISIONS/0042-the-shape-of-an-event-on-the-wire.md)).
>
> What does **not** change is this document's model, which is the part ADR 0074 decided: a floor
> plus independent capabilities, an SDK that implements what it claims and is legitimate when it
> claims less, identity taken from the sealed credential rather than the environment, at-least-once
> with dedup on `x-event-id`, and conformance as executable fixtures per capability rather than
> prose. The envelope keeps its shape ([ADR 0042](../../02-DECISIONS/0042-the-shape-of-an-event-on-the-wire.md));
> it becomes the message body.
>
> Rewriting the wire sections onto the subjects and streams of
> [design 25](25-the-bus-on-nats.md) §2–§3, and recapturing the fixtures there, is **step 3 of
> [ADR 0116](../../02-DECISIONS/0116-the-bus-is-built-in-five-steps.md)**. Until that lands, read
> the sections below for what two implementations may not disagree *about*, and design 25 for what
> they will disagree about it *on*. A specification that silently described a retired transport
> would be worse than an absent one, because it reads as current — hence this note rather than a
> quiet edit.
> Statements here marked *verified* were checked against a running server while the runtime's
> client was written, not reasoned from documentation.
## The shape of it
@@ -70,22 +62,39 @@ document:
| field | is | required |
|---|---|---|
| `url` | an `amqps://` URL carrying the account's user and password | yes |
| `fingerprint` | sha256 of the certificate the broker must present | yes for a scoped account |
| `url` | a `tls://` URL for the bus, with the account's user and password | yes |
| `fingerprint` | sha256 of the certificate the bus must present | yes for a scoped account |
| `node` | the machine this account was issued for | yes for a scoped account |
| `module` | the module this account was issued for | yes for a scoped account |
A plain string rather than a document is a **bootstrap URL** — unscoped, for the moment before a
mesh can issue anything. An implementation accepts both and must not treat the second as ordinary.
**`node` and `module` are not decoration: every subject an implementation touches is derived from
them.** Its own namespace is `mesh.mod.<module>`, its consumer is `<node>_<module>`, its inbox is
its own. So a credential without them is refused rather than guessed at — an implementation that
fell back to an environment variable would let anything on the machine decide which module it is,
which is what the identity rule below exists to prevent.
The credential itself is fetched, never carried in a declaration: a declaration is persisted as
state and a sealed secret in a stream is an archive rather than a moment
([design 29](32-what-a-module-declares.md) §10).
### Connecting
- The connection **pins the fingerprint**. It does not trust a certificate authority, and it does
not skip verification. A broker presenting a different certificate is refused, whatever else is
not skip verification. A bus presenting a different certificate is refused, whatever else is
true of it.
- A scoped account **does not declare exchanges**. The foundation owns them; an account that may
declare one is an account that may create a parallel mesh by typo.
- An implementation **declares its own queue** and nothing else.
- **The certificate must also carry a name the bus is dialled by.** *Verified:* the NATS client
exposes no hook to replace hostname verification, so pinning no longer makes it redundant the
way it did on AMQP — the pin happens before dialling and the library's own name check happens
beside it. A certificate without a matching subject-alternative name is refused at connect, by
a library error rather than by anything the mesh says.
- An implementation **creates nothing on the bus**: not a stream, not a consumer, not a subject.
Streams and durable consumers are the controller's alone ([design 25](25-the-bus-on-nats.md)
§3), and a module's account cannot reach the JetStream API to make one. An implementation binds
the consumer the mesh created for it, and if it is absent that is a mesh that has not finished
assigning the module, not something for the module to fix.
### Identity
@@ -100,26 +109,49 @@ the credential disagree, the credential wins and the variable is overwritten.
## Capability: events
### The exchanges
### The subjects
| exchange | carries |
| subject | carries |
|---|---|
| `mesh.events` | every event |
| `mesh.events.dead` | what could not be handled |
| `mesh.mod.<module>.event.<key>` | an event that module emitted |
| `mesh.seat.<seat>.event.<verb>` | an event the holder of that role emitted |
### The queue
Both are captured by the `EVENTS` stream. **An event's source is enforced rather than claimed**: a
module's account may publish only into its own namespace, so `x-source` cannot disagree with where
the message arrived from.
One **durable** queue per consumer, named `<node>.<module>.events`, with as many bindings as the
module has patterns. Durable because an event emitted while a module is restarting is exactly the
one that must not be lost.
**The `event` token is load-bearing.** A module's namespace also carries its tool calls
(`mesh.mod.<module>.tool.<tool>`), and a stream is defined by a subject filter — without the token
the events stream would capture every tool invocation in the mesh, and a tool call must never be
persisted.
**A message matching two bindings is delivered once**, so an implementation must match the routing
key against its own patterns locally to decide which handlers run. An implementation that ran every
handler whose exchange binding matched would run the wrong one.
### The consumer
One **durable consumer** per module, named `<node>_<module>`, carrying one filter per pattern the
module consumes. Durable because an event emitted while a module is restarting is exactly the one
that must not be lost.
**Created by the controller, bound by the implementation.** A module declares what it reacts to
and never how delivery works, so it does not name its consumer, does not choose its ack policy or
delivery limit, and cannot misconfigure them.
*Verified, and it is a trap:* a durable name **may not contain a dot**, while the subject a
consumer acknowledges on is `$JS.ACK.<stream>.<consumer>.…` — two names joined by one. An
implementation that treats them as a single string reads correctly in a permission list and is
refused as a consumer name. Left wrong, the symptom is every message redelivered forever while
the permissions look right.
**One consumer may carry filters wider than one handler's pattern**, because a module subscribing
twice gets one consumer with both. So an implementation still matches the key against its own
patterns locally to decide which handlers run — and **acknowledges a message no handler wanted**,
or it is redelivered until it expires.
### The envelope
Headers ride as AMQP headers. The body is JSON.
Headers ride as **NATS headers**; the body is JSON, and the body alone. *Verified:* the payload is
the event's `body`, not the whole envelope re-encoded — an implementation that nested the envelope
would pass every one of its own tests and agree with no other, which is the exact failure the
conformance fixtures exist to catch. The key is recovered from the subject, not carried twice.
| header | is | required |
|---|---|---|
@@ -140,6 +172,11 @@ breaking change for everybody.
At-least-once. **Deduplication is on `x-event-id`**, which only the emitter can produce — a
consumer cannot tell a redelivery from a second event any other way.
On NATS the id does double duty: an implementation passes it as the publish's message id, so the
**server** also refuses a duplicate inside its window. That narrows the window in which a
consumer has to deduplicate; it does not remove the requirement, because the window is finite and
a redelivery after it is still a redelivery.
### What is true, checked (2026-09-16)
Go emits all five required headers; the SDK requires exactly those. `x-causation-id` and `x-schema`
@@ -154,22 +191,30 @@ version to declare.
A module's tools are its operator-facing surface.
- A tool is served from a **shared durable queue**, `serve.<key>`. Shared, so several runtimes
serving one tool compete for a call rather than each answering it.
- A call is request and reply. The reply returns through the RPC exchange `mesh.rpc`, keyed by the
caller's own reply queue — **not** through the default exchange, which would let a caller publish
into any queue on the broker.
- A caller needs a **reply queue**, and that is what a module's scoped account may not declare
([issue 049](../../04-ISSUES/049-a-module-can-serve-tools-and-nothing-can-call-them/00-report.md)).
So a module may serve tools and may not call them.
- **The control plane is the way to ask**
([ADR 0095](../../02-DECISIONS/0095-the-control-plane-is-the-way-to-ask-a-module.md)):
`ask <module> <tool> [json]` publishes on `mesh.rpc` under `<module>.<tool>` with a private reply
queue bound under its own name, and prints the answer as the module gave it. A module declares
nothing about being asked — serving a tool is being askable through the control plane. A
module-to-module call, if one is wanted, is a grant like any other and a later decision.
*How it is checked:* a tools-only bed asks a served tool through the control plane and asserts
an answer arrived, where a timeout would read differently.
- A tool is served on `mesh.mod.<module>.tool.<tool>`, with a **queue group** — so several
runtimes serving one tool compete for a call rather than each answering it.
- A call is request and reply on **core NATS, never a stream**. A tool call is not persisted: a
lost one is a timeout the caller already handles, and a stream of them would be the mesh's most
voluminous and least valuable traffic competing for retention with the messages that matter.
- The reply goes to the inbox the request carries. A responder may answer it because its account
is granted **`allow_responses`** — one reply to the subject of a message it actually received,
and nothing wider. That is what makes a per-account inbox prefix workable: no user is ever
granted `_INBOX.>`, so without it a responder could not reach the caller at all.
- **A module may now call a tool, which on AMQP it could not.** *Verified:* two modules on
separate connections, one serving and one calling, with an answer returned and a throwing
handler reaching the caller as an error rather than a timeout.
[Issue 049](../../04-ISSUES/049-a-module-can-serve-tools-and-nothing-can-call-them/00-report.md)
recorded the old limit — a scoped account could not declare the reply queue a caller needs —
and [ADR 0095](../../02-DECISIONS/0095-the-control-plane-is-the-way-to-ask-a-module.md) routed
every ask through the control plane because of it. **That constraint is gone**, and each
account's own inbox prefix replaces it.
ADR 0095 is not thereby reversed: the control plane remains *a* way to ask, and a person asking
a module should still go through it. What changes is that "a module-to-module call, if one is
wanted, is a later decision" is no longer a question about *capability*. It is a policy
question, and the answer the mesh already has is `uses`: a module declares the seat it calls,
and the permission follows the declaration.
- A module declares nothing about being asked — serving a tool is being askable.
---
03-DESIGN/01-to-be/23-choosing-a-provider.md
+2 -2
View File
@@ -6,7 +6,7 @@ updated: 2026-09-25
decisions:
- 02-DECISIONS/0084-which-provider-serves-a-consumer.md
- 02-DECISIONS/0027-a-provision-names-what-the-consumer-is-coupled-to.md
- 02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md
- 02-DECISIONS/0126-a-module-declares-its-own-seats.md
---
# 23 — Choosing a provider
@@ -54,7 +54,7 @@ to that provider and not to whichever one is nearest.
**A seat names the mesh's one provider of a kind.** Where a seat delivers the provision, its holder
answers for it when several providers exist and the consumer named none. That is not picking: the
choice was made once, mesh-wide, by assigning the holder, rather than once per consumer by naming it
([ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md),
([ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md) (superseding [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)),
[26 — The seats](26-the-seats.md)). A named provider still wins over the seat, because a consumer
coupled to particular contents has said so.
03-DESIGN/01-to-be/25-the-bus-on-nats.md
+170 -32
View File
@@ -1,15 +1,16 @@
---
layer: to-be
status: proposed
status: in-progress
code:
- mesh-controller internal/link (to be replaced)
- mesh-host internal/link (to be replaced)
- mesh-tools src/broker-amqp.ts (to be replaced)
- mesh-catalog modules/nats (to be written)
- mesh-sdk src (the protocol's NATS binding, step 3)
updated: 2026-09-26
updated: 2026-09-27
decisions:
- 02-DECISIONS/0106-the-bus-is-nats.md
- 02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md
- 02-DECISIONS/0116-the-bus-is-built-in-five-steps.md
- 02-DECISIONS/0074-the-wire-is-specified-not-the-types.md
- 02-DECISIONS/0079-the-foundation-seats-are-named-after-their-servers.md
@@ -17,6 +18,8 @@ decisions:
- 02-DECISIONS/0043-a-module-broker-account-is-scoped-by-emits-and-consumes.md
- 02-DECISIONS/0083-one-push-leaves-the-mesh-consistent.md
- 02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md
- 02-DECISIONS/0129-a-seat-carries-the-protocol-of-its-role.md
- 02-DECISIONS/0130-the-predecessor-is-ending-and-its-broker-goes-with-it.md
---
# 25. The bus on NATS
@@ -29,19 +32,37 @@ Prose and diagrams only; no configuration is pasted.
## 1. What the bus is for
The bus carries five kinds of traffic today, and this design keeps the five, renaming nothing a
module can see:
**The bus is where the mesh happens.** Not a transport the mesh sends things over — the place a
module is reachable at all, where a role is addressed without knowing who holds it, where the
mesh's own state lives, and where what a module may say is decided by what it declared.
| Traffic | Today | Guarantee it needs |
| Traffic | Shape | Guarantee it needs |
|---|---|---|
| **control** — a node's report, its heartbeat, a build's outcome, an enrolment | queues `control`, `.upgrades`, `.catchup` | nothing lost while the store restarts; retried; in order per node |
| **declarations** — the controller tells a node what to be | queue `node.<name>` | the node gets the newest; a stale one is never applied |
| **builds** — the controller asks the build machine to build | queue `builds` | at least once, one builder at a time |
| **events** — a module says something happened | topic exchange `mesh.events`, keys `<module>.<event>` | delivered to every consumer that declared it; dead-lettered when it cannot be |
| **tools** — one module or person asks another's tool a question | exchange `mesh.rpc`, per-tool service queues `serve.<module>.<tool>` | one answer, from one server, or a timeout |
| **control** — a node's report, a build's outcome, an enrolment | job | nothing lost while the store restarts; retried; in order per node |
| **heartbeat** — a node saying it is alive | fire and forget | none; a lost one is the next one |
| **declarations** — the controller tells a node what to be | state | the node gets the newest; a stale one is never applied |
| **builds** — work for the build machine | job | at least once, one worker at a time |
| **events** — a module says something happened | 1:many | delivered to every consumer that declared it; dead-lettered when it cannot be |
| **tools** — a module or a person asks another's tool | request/reply | one answer, from one server, or a timeout |
| **work to a role** — a module submits to a capability without knowing who provides it | job | exactly one holder does it; it queues while nobody does |
The sdk's contract — `request`, `handle`, `publish`, `subscribe`, `close` — is the whole surface a
module sees, and it does not change ([ADR 0039](../../02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md)).
The last two rows are the ones worth dwelling on, because they are not messaging in the sense of
carrying bytes from A to B. **A role is addressable**, so a caller names the capability and never
the module or the node — and the implementation can be replaced under it without a caller
changing ([ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md)). That is a
property of the mesh's architecture that happens to be expressed in subjects.
And more of the mesh lands here as it is built: conditions and observed state in key-value
buckets that anything may watch, the server's own advisories becoming observations like any other
([research 017](../../01-RESEARCH/017-a-mesh-that-heals-itself/00-overview.md)), and a person's
client speaking the bus directly rather than through a surface built over it (§7). None of that
is a message being moved; all of it is the bus being the mesh's centre.
**What a module sees of it is small and derived.** It declares what it emits, consumes, serves
and uses, and the subjects, streams, consumers and permissions all follow from that
([design 29](32-what-a-module-declares.md)). The sdk's contract — `request`, `handle`, `publish`,
`subscribe`, `close` — is the whole surface, and it does not change
([ADR 0039](../../02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md)).
## 2. Subjects
@@ -52,14 +73,30 @@ permissions are expressed as which branches of it that account may publish to an
mesh.control.<node>.report a node's report (JetStream: CONTROL)
mesh.control.<node>.alive heartbeat (core, no persistence)
mesh.control.enrol an enrolment request (JetStream: CONTROL)
mesh.control.built a build's outcome (JetStream: CONTROL)
mesh.node.<node>.declare a declaration for a node (JetStream: NODES, last-per-subject)
mesh.build.request work for the build machine (JetStream: BUILDS, work queue)
mesh.events.<module>.<event> an event (JetStream: EVENTS)
mesh.tools.<module>.<tool> a tool invocation (core request/reply)
mesh.mod.<module>.event.<event> an event (JetStream: EVENTS)
mesh.mod.<module>.tool.<tool> a tool invocation (core request/reply)
mesh.seat.<seat>.accept.<verb> work submitted to a role (JetStream: per-seat work queue)
mesh.seat.<seat>.event.<verb> a role's own event (JetStream: EVENTS)
mesh.seat.<seat>.tool.<verb> a role's tool (core request/reply)
mesh.ask.<node>.<command> the controller's command api (core request/reply)
```
**Revised 2026-09-27** ([ADR 0129](../../02-DECISIONS/0129-a-seat-carries-the-protocol-of-its-role.md)):
**`mesh.build.request`, `mesh.control.built` and the BUILDS stream are gone.** A build is work submitted to a role, and the
mesh already has a shape for that — a seat's `accept` subjects, on a work queue with a queue group of
holders, which is what a build queue shared by several machines *is*. Keeping a second mechanism for it
meant two things to reason about and two places for a permission to be wrong. A build's outcome is the
seat's own event — which is why the control branch loses its copy too: one publish reaches whoever
asked, the controller that records it and the catalogue that places it — the fan-out a shared exchange gave for free, as a derived subject rather than a
configured topology.
**Revised 2026-09-26** ([design 29](32-what-a-module-declares.md)): a module's events and tools
moved from `mesh.events.*` / `mesh.tools.*` into one namespace per module, `mesh.mod.<module>.>`,
so a module's authority over its own name is a single subject pattern the server enforces — and
each carries a **kind token**, without which an events stream's filter would capture tool calls.
Seats are the same shape, one namespace per role.
Two things this buys over the exchanges: **request/reply is native** — a tool call is one
`request` on `mesh.tools.<module>.<tool>` answered by whichever runtime serves it (a queue group per
tool, so several nodes may serve one tool); and **a declaration is last-per-subject** — the NODES
@@ -69,7 +106,14 @@ exactly the current declaration and nothing older. That is the wire-level answer
*is* the order, and a node that sees sequence n refuses n−1 by construction.
**A reply-to travelling through a JetStream stream is carried in the payload, never in the
transport `Reply` field.** Revision, first review: core NATS request/reply sets the requester's
transport `Reply` field.** *Verified against a running server, 2026-09-27*: a caller published
asking for a reply to `_INBOX.LCr3M83q…`, and the consumer saw a `Reply` field of
`$JS.ACK.PROBE.probe_consumer.1.1.1…`. The address is replaced, not merely at risk — so the
payload-borne reply subject below is necessary rather than defensive, and the check is a test
rather than a note, because a future server that stopped doing this would leave enrolment
working and the reason for the field quietly becoming folklore.
Revision, first review: core NATS request/reply sets the requester's
ephemeral inbox as the message's `Reply` field, and a plain responder answers it directly — but a
message a JetStream consumer delivers has already had that field claimed for the consumer's own
ack address (`$JS.ACK.<stream>.<consumer>...`), so by the time the controller (§3's CONTROL
@@ -89,10 +133,9 @@ Core NATS is at-most-once. Everything the mesh must not lose lives in a JetStrea
| Stream | Subjects | Retention | Why |
|---|---|---|---|
| CONTROL | `mesh.control.>` except `alive` | work queue, one consumer (the controller), explicit ack | the store-window guarantee ([ADR 0083](../../02-DECISIONS/0083-one-push-leaves-the-mesh-consistent.md)): the controller `nak`s with a delay while its store is away and the message is redelivered; nothing is dropped |
| CONTROL | `mesh.control.>` except `alive` (a build's outcome moved to its seat, ADR 0121) | work queue, one consumer (the controller), explicit ack | the store-window guarantee ([ADR 0083](../../02-DECISIONS/0083-one-push-leaves-the-mesh-consistent.md)): the controller `nak`s with a delay while its store is away and the message is redelivered; nothing is dropped |
| NODES | `mesh.node.>` | last per subject | one declaration per node, always the newest |
| BUILDS | `mesh.build.>` | work queue, explicit ack | at least once; a builder that dies mid-build has its message redelivered |
| EVENTS | `mesh.events.>` | limits (age, size), durable consumer per subscribing module | a subscriber that was down catches up; after `max-deliver` attempts the advisory feeds `mesh.events.dead` (its own small stream) |
| EVENTS | `mesh.mod.*.event.>` | limits (age, size), durable consumer per subscribing module | a subscriber that was down catches up; after `max-deliver` attempts the advisory feeds `mesh.events.dead` (its own small stream) |
Tool calls and heartbeats stay on core NATS: a lost heartbeat is the next heartbeat; a lost tool
call is a timeout the caller already handles.
@@ -100,6 +143,33 @@ call is a timeout the caller already handles.
Streams and consumers are objects the controller creates at genesis and asserts on start; a module
declares nothing about them. The controller is the only writer of stream definitions.
### The store window, and what moving it into the server changes
The guarantee ([ADR 0083](../../02-DECISIONS/0083-one-push-leaves-the-mesh-consistent.md)) is
that a push the controller cannot record because its store is restarting is **held and retried** —
never dropped, never falsely acknowledged. Here that is a `nak` with a delay: the server holds
the message and redelivers it, so the controller keeps no list of parked messages and one that
restarts mid-window loses nothing it was holding.
**That is a plain win, and it introduces one problem worth naming.** Holding a delivery in memory
let the controller drop an older report when a newer one for the same node arrived, because
acting on the older after the newer would undo the newer. A `nak`ed message belongs to the server
and comes back whatever happened meanwhile — so the older report is redelivered *after* the newer
was applied.
The answer was already in the message. A report carries the **digest of the declaration it is
about**, which exists because an earlier attempt to order reports by time lost the race it
invited: an apply that began under the previous declaration finishes after the next is sent, and
its report reads as newer than the send. Clocks cannot answer *which*.
So supersession stops being something the controller remembers and becomes something it checks —
a report whose digest is not the one outstanding for that node is acknowledged without being
acted on. The same shape as a node refusing a superseded declaration by sequence
([issue 107](../../04-ISSUES/107-a-declaration-carries-no-order/00-report.md)): **ordering settled
by what a message says, not by when it arrived.** And staleness is checked before the store is
waited on, so a redelivery that lost its race does not hold a slot in the window that a current
message needs.
## 4. Accounts
[ADR 0043](../../02-DECISIONS/0043-a-module-broker-account-is-scoped-by-emits-and-consumes.md) says a
@@ -128,19 +198,56 @@ expresses this exactly, per subject, and better than a vhost could:
permissions name only that one prefix, for the reply to any request it makes and nothing
wider. First review found the account note without this and read it as "any user may
subscribe any inbox" — which was accurate against the text as it stood.
**And a scoped inbox needs `allow_responses`, or nothing can answer.** Revision, found while
composing the first real configuration: the rule above scopes each user's inbox to itself,
which is right — and leaves a responder unable to reply, because the answer goes to the
*caller's* inbox, which the responder has no permission for. The two ways out are granting
every responder `_INBOX.>`, which is exactly the blanket grant this bullet refuses, or NATS's
own `allow_responses`: the server permits one reply to the reply-subject of a message the user
actually received, within a TTL, and nothing else. So authority to answer is bounded by having
been asked, and only principals that serve something are granted it — a pure consumer gets
nothing. Without this the scoping is not merely incomplete: every tool call in the mesh times
out, and the permission list looks correct while it happens.
- **One user per module per node**, as today, with publish permissions
`mesh.events.<module>.<event>` for each emit, `mesh.tools.<module>.>` to serve its tools, its
own ack-reply subject for each durable consumer it holds, and its own inbox prefix; subscribe
permissions for each consumed event's subject, its tool subjects, and that same inbox prefix.
Nothing else. A module that tries to publish outside its emits is refused by the server, not by
convention.
- **The controller's user** owns `mesh.control.>`, `mesh.node.>`, `mesh.build.>` and the streams.
- **The controller's user** owns `mesh.control.>`, `mesh.node.>` and the streams, and may submit work
to the seats the mesh's own flows use — a build, for one (ADR 0121).
**A host's user** may publish its own `mesh.control.<node>.>` and subscribe its own
`mesh.node.<node>.declare` — and nothing of any other node's.
- **A person's user** (§7) is a module-shaped user with permissions on the tool subjects it may
invoke, issued and revoked by the controller like any account.
**Accounts are configuration, not API calls.** The controller composes the server's user list and
**The server does not verify client certificates, and TLS is still required.** *Revision,
2026-09-27, found by building the module's image and connecting to it as a host would.* The first
composed configuration said `verify: true`, which makes the server demand a **client** certificate —
and nothing in the mesh presents one. A host pins this server's exact certificate and authenticates
with the password the mesh minted ([ADR 0004](../../02-DECISIONS/0004-a-node-and-how-it-joins.md)),
and a module's runtime does the same. With it on, every connection in the mesh dies at the TLS
handshake before any password is looked at, and the error — "client didn't provide a certificate" —
reads as a fault in the client rather than in the bus's configuration. The `tls` block is what makes
TLS required; `verify` only decides whether client certificates are checked. What is given up is a
second factor the mesh has no machinery to issue or rotate — a certificate per module per node — and
what is kept is stronger than a name check in both directions: an exact pin outward, a password
scoped per user inward. **Mutual TLS is a later question and would need that machinery first.**
**The mesh composes the accounts; the module composes its server.** *Revision, 2026-09-27, while
building the composition.* An earlier reading of the paragraph below had the controller writing the
whole file. It writes only the user list. A server's ports, its TLS paths and its store directory
are properties of the container the module raises — they live in its image and its mounts and change
when it does — so the module declares its own configuration and `include`s the mesh's half. A
controller that wrote the whole file would have to be kept in step with a Dockerfile it never sees,
and a module could not change its own image without the mesh agreeing. Asking for the user list is
not enough to receive it: the file holds every user's password hash, so the claim on `mesh-broker` is
what authorises it. And the two files share one directory of necessity — an absolute include path is
resolved relative to the including file's own directory, so a server given one from elsewhere looks
for it underneath that directory and refuses to start.
**Accounts are configuration, not API calls.** The controller composes the mesh's user list and its
permissions into a file the host declares. **How that file reaches the running server is §5's,
not this one's** — revision, first review: an earlier draft said "reloads" and cited a precedent
that does not apply to a container (see §5). No management API, no credential travelling through a
@@ -157,9 +264,14 @@ signing hierarchy for nothing.
`nats` is a catalogue module claiming the seat `mesh-broker`
([ADR 0079](../../02-DECISIONS/0079-the-foundation-seats-are-named-after-their-servers.md): the seat
is the server, and the server changes). It declares one container (a single binary; JetStream on a
named volume), its listening ports — client, TLS, and the monitoring endpoint on loopback — and a
configuration file the controller composes (accounts, permissions, TLS, JetStream).
is the server, and the server changes). It declares one container (a single binary; **JetStream on a host
directory bind, not a named volume** — revision, second review:
[issue 115](../../04-ISSUES/115-a-named-docker-volume-is-invisible-and-one-flag-from-gone/00-report.md)
is resolved, and converted the store, the broker and two others away from named volumes for the
reason it names; the bus's own data is not the place to reintroduce one), its listening ports —
**the client port, which carries TLS itself** rather than standing beside a plaintext one as the
AMQP broker's 5671/5672 pair did, and the monitoring endpoint on loopback — and a configuration
file the controller composes (accounts, permissions, TLS, JetStream).
**How that file's changes reach the running server, corrected on revision.** First review: the
earlier draft named `reload-on` as the mechanism, citing the container runtime's own trust file as
@@ -186,10 +298,33 @@ same place `modules/gitea/token.ts` keeps its own state rather than asking the h
The host's only job is what it already does for any directory resource: keep the file's content
current. Nothing is declared as `reload-on` or `restart-on` for this resource at all.
Its guard is the same rule as the AMQP broker's: the monitoring port is refused from anything but
Its guard is the same rule as the deprecated broker's: the monitoring port is refused from anything but
the private network. It is raised at genesis like the store, adopted as a module in the same
phase. The predecessor's AMQP broker remains a module of its own, `lavinmq-compat`, with a single
purpose and a retirement condition: no client connected for a period the operator sets.
phase.
**The deprecated broker is an ordinary module, not a compatibility layer.** Revision, second review
([ADR 0127](../../02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md): AMQP is not a provision, and everything speaks to the `mesh-broker` seat)): earlier text here, and
ADR 0106 before it, called it `lavinmq-compat` — one purpose, the predecessor's clients, and a
retirement condition of no client connected for a period the operator sets. It is none of those.
A module may legitimately need an AMQP broker as a **backing service**, the way it needs a
database, and the provider that answers that is an ordinary module like any other: no seat, not
foundation, never raised at genesis, installed when something wants it and absent from a mesh
that does not. There is no retirement condition, because the day its last client disappears is
not a day anything is waiting for.
**Revised 2026-09-27** ([ADR 0130](../../02-DECISIONS/0130-the-predecessor-is-ending-and-its-broker-goes-with-it.md)):
**that day is coming.** The predecessor is deprecated — some of it still running, none of it being
migrated, left to stop rather than moved — so the broker retires once nothing requires `amqp`. Still no
retirement *condition* and no end-date machinery: a provision with no consumers has its provider
unassigned, which is the ordinary mechanism and is ADR 0127 being paid off rather than revised. What
also goes with it is the tooling that reaches this installation's machines remotely, because the
predecessor's own mesh talks over that broker — so the rollout is driven from the node, or before the
broker stops.
What is deprecated is AMQP as **the mesh's transport**, which is this whole document. The rule
that remains is about direction rather than software: *inter-module communication goes over the
bus.* A module may hold a broker, a database or a cache for itself; it may not use one as a
channel to another module.
## 6. Joining: the enrolment handshake
@@ -272,7 +407,7 @@ wrong until there is a second mesh. *Ends at: the genesis bed.*
**Step 2 — adoption puts the broker in its seat.** A mesh already running does not get a foundation
module by being raised again; it adopts one in place
([ADR 0100](../../02-DECISIONS/0100-a-node-in-use-is-adopted-before-it-is-converged.md)). The
server is raised beside the AMQP broker on its own ports, carrying no mesh traffic yet, and the
server is raised beside the deprecated broker on its own ports, carrying no mesh traffic yet, and the
`nats` module is adopted onto it. The seat it claims is **`mesh-broker`**, unchanged — the
foundation seats are named after the server's role rather than the product
([ADR 0079](../../02-DECISIONS/0079-the-foundation-seats-are-named-after-their-servers.md)) for
@@ -333,7 +468,7 @@ itself enforces and a plain client can therefore check:
watcher-poll interval, without a restart.
**Step 2 — the adoption bed**, a mesh already running that has never had this server:
- the server is raised beside the AMQP broker on its own ports and the `nats` module is adopted
- the server is raised beside the deprecated broker on its own ports and the `nats` module is adopted
onto it in place, holding the data and the configuration it was raised with;
- the seat it claims is `mesh-broker`, and a second assignment of it anywhere in the mesh is
refused at resolution — *one per mesh*, as ADR 0079 requires;
@@ -398,8 +533,11 @@ find what changed and why.
**Still open:**
- Whether EVENTS should be one stream or one per emitting module (retention per module vs. one
policy). One stream is proposed; the review may disagree.
- ~~Whether EVENTS should be one stream or one per emitting module.~~ **Closed**
([ADR 0127](../../02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md): AMQP is not a provision, and everything speaks to the `mesh-broker` seat) (superseding [ADR 0125](../../02-DECISIONS/0125-the-bus-is-the-only-broker.md))): one stream, and not as a
preference — the streams the bus is made of are composed as configuration before any module
runs, because a provisioner is itself a module that needs a bus account to start. Bootstrapping
decides it.
- The heartbeat interval and the controller's "quiet" threshold on core NATS without persistence —
the same numbers as today are proposed.
- Whether the person's client is a catalogue module (runs on an enrolled workstation node) or a
03-DESIGN/01-to-be/26-the-seats.md
+103 -30
View File
@@ -4,13 +4,17 @@ status: implemented
code:
- mesh-controller internal/catalogue/seats.go
- mesh-controller internal/catalogue/resolve.go
- mesh-controller internal/inventory/seats.go
- mesh-controller internal/inventory/migrations/0039-a-seat-is-held-by-one-assignment-on-record.sql
- mesh-controller cmd/mesh-controller/seats.go
- mesh-controller cmd/mesh-controller/source.go
- mesh-controller internal/inventory/migrations/0032-a-source-may-live-on-a-seat.sql
- mesh-catalog modules/gitea/module.json
updated: 2026-09-27
decisions:
- 02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md
- 02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md
- 02-DECISIONS/0126-a-module-declares-its-own-seats.md
- 02-DECISIONS/0128-the-mesh-bus-is-required-not-ambient.md
- 02-DECISIONS/0111-a-build-source-is-on-the-git-seat-or-external.md
- 02-DECISIONS/0109-a-package-registry-seat-is-one-per-ecosystem.md
- 02-DECISIONS/0117-a-machines-uplink-is-a-seat.md
@@ -41,6 +45,31 @@ is refused. A seat makes a role singular, never a module.
**The seat points at the assignment.** Everything the mesh knows about the holder is what it knows
about that assignment: the node, the node's settings for the module, and what the module serves.
**Which assignment holds a seat is a fact on record, and changes as one act.** Revision, 2026-09-27
([ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md)). Until
then the holder was derived — the module that is assigned and claims the seat holds it, and a second
eligible assignment was refused. That has no way to pass a seat from one holder to the next without a
moment in which nobody holds it, and the controller finds its own bus through one of these seats: that
moment took the control plane down for an evening. So the holder is now one row the controller keeps,
written by a handover — `seat <name> --to <node>/<module>` — that names the seat and the assignment
taking it over and replaces the previous holder in the same write. Between two handovers the seat has
exactly one holder, and it is never none.
Three consequences follow. **A seat with no row is held as it always was**: the sole eligible
assignment holds it, and two eligible ones are refused — so a mesh that has never handed a seat over
behaves exactly as before, and the row appears the first time somebody does. **With a row, any other
assignment whose module could hold the seat is eligible and silent**: neither refused nor holding.
That is what lets the next holder run beside the current one until the handover, which the bus's move
needs ([28](28-building-the-bus.md), task 5.3). **And a holding is the assignment's**: unassigning the
holder takes the row with it, so a seat never points at something that is not running anywhere, and
the seat falls back to derivation rather than to nothing.
The handover refuses what would make the new holder wrong before anything is written: the seat must
exist, the assignment must exist, and the module must be able to hold the seat — claim it at its scope
and provide what it delivers, judged against the store's row and not against anything compiled into a
binary. It does not check that the module is running yet; `push` confirms that afterwards, and a
handover that could only be recorded after the new holder was up could not be the switch.
**The set is closed.** A seat the mesh does not define is refused wherever it is named, and so is one
named at the wrong scope. Adding a seat is a decision, recorded, for the reason every addition to the
host's vocabulary is one: the set is what a person reads to learn what a mesh can have, and an entry
@@ -48,28 +77,55 @@ nobody argued for is an entry nobody can explain.
## The set
| seat | scope | delivers | typically held by |
|---|---|---|---|
| `mesh-controller` | mesh | — | the controller |
| `mesh-store` | mesh | — | the store the mesh's own records live in |
| `mesh-broker` | mesh | — | the broker carrying the mesh's own bus |
| `mesh-vault` | mesh | `secret`, reserved | the vault |
| `the-artifact-store` | mesh | `artifact-store` | the artifact registry |
| `the-catalogue` | mesh | — | the catalogue |
| `npm-package-registry` | mesh | `npm-package-registry` | the forge |
| `git` | mesh | `git` | the forge |
| `the-build-machine` | node | — | a builder |
| `the-dns-port` | node | — | the local resolver |
| `the-intrusion-prevention` | node | — | an intrusion-prevention service |
| `the-packet-filter` | node | — | the packet filter |
| `the-private-network` | node | — | the private network the mesh runs over |
| `the-resolver-configuration` | node | — | whichever of the alternative resolver configurations is chosen |
| `the-showcase` | node | — | the showcase module |
| `the-uplink` | node | — | the program that manages the machine's own network ([ADR 0117](../../02-DECISIONS/0117-a-machines-uplink-is-a-seat.md)) |
**The set is derived, and only the mesh's half is written here.** Revision, 2026-09-26
([ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md), superseding
[ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)): a module
declares its own seats with their protocols, so the seats a mesh has are the mesh's own **plus
every registered module's**. The set is still closed — a seat named nowhere is refused — but it is
computed from the catalogue rather than maintained by hand, which is the property 0110 actually
needed and the table could not keep.
The controller holds this set in code, and a test asserts both its size and that every entry names
the record that made it a seat. **This table and [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)
govern, and code that disagrees is what is wrong.** The implementation in progress predates several
**And the mesh's own half is data, named for its scope.** Revision, 2026-09-27, reconciling two
records made in parallel: [ADR 0121](../../02-DECISIONS/0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md)
names a system seat for the scope it is held at — `mesh-*` for one per mesh, `node-*` for one per
machine — and [ADR 0122](../../02-DECISIONS/0122-a-seat-is-data-a-rename-is-a-database-update.md) moves
the set out of compiled code into a table the controller owns, so a rename is one write rather than a
rebuild of everything that names one.
So the set has two halves and neither is written out here: the mesh's own, which the controller holds
as rows, and every registered module's, which is computed from the catalogue. What this document keeps
is what a seat *is* — the rest would be a third copy, stale the first time somebody renamed one, which
is the fault ADR 0122 exists about.
**Every seat below is named `mesh-*`, and the prefix is the reservation rule**: a module declaring
any `mesh-*` name is refused at registration, so there is no reserved-names list to drift. Ten of
these are renamed to restore [ADR 0079](../../02-DECISIONS/0079-the-foundation-seats-are-named-after-their-servers.md)'s
convention, which later seats departed from.
| seat | was | scope | delivers | typically held by |
|---|---|---|---|
| `mesh-controller` | — | mesh | — | the controller |
| `mesh-store` | — | mesh | — | the store the mesh's own records live in |
| `mesh-broker` | — | mesh | `mesh-bus` | the broker carrying the mesh's own bus |
| `mesh-vault` | — | mesh | `secret`, reserved | the vault |
| `mesh-artifact-store` | `the-artifact-store` | mesh | `artifact-store` | the artifact registry |
| `mesh-catalog` | `the-catalogue` | mesh | — | the catalogue |
| `mesh-npm-package-registry` | `npm-package-registry` | mesh | `npm-package-registry` | the forge |
| `mesh-git` | `git` | mesh | `git` | the forge |
| `mesh-build-machine` | `the-build-machine` | node | — | a builder |
| `mesh-dns-port` | `the-dns-port` | node | — | the local resolver |
| `mesh-intrusion-prevention` | `the-intrusion-prevention` | node | — | an intrusion-prevention service |
| `mesh-packet-filter` | `the-packet-filter` | node | — | the packet filter |
| `mesh-private-network` | `the-private-network` | node | — | the private network the mesh runs over |
| `mesh-resolver-configuration` | `the-resolver-configuration` | node | — | whichever of the alternative resolver configurations is chosen |
| `mesh-showcase` | `the-showcase` | node | — | the showcase module |
The controller holds **the mesh's own** entries in code, and a test asserts their size and that
every one names the record that made it a seat. A module's seats are not here and never will be —
they are read from the catalogue. **This table and
[ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md) govern, and code that
disagrees is what is wrong.** The implementation in progress predates several
things here: seats held by assignments rather than claimed by definitions, the `mesh-vault` seat and
its reservation, and the foundation's seats delivering nothing. It is brought to this table before it
merges.
@@ -121,6 +177,15 @@ moves that to a host port requirement.
## A seat that delivers nothing
**A module's declared seat may promise nothing too, and that is a marker seat.** Correction of fact,
2026-09-27: [ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md)'s "a declared seat
carries a protocol" governs what a *holder* must satisfy, not that every seat offers something. A
marker seat's protocol is satisfied by holding it, which is the whole of what a marker says. Refusing
an empty one would refuse most of the node-scoped set, the showcase module's own seat included.
Nothing reaches that state by accident: an unknown manifest field is refused outright, so an empty
protocol was written as one. Checked by a registration test accepting a node seat with no protocol
and by the showcase manifest, which declares one.
Most node seats deliver nothing. They say which module is this machine's packet filter, or which of
two alternative resolver configurations it runs, and a second holder is refused. That is the whole of
their job, and it is a real one: it is the mesh saying what a machine is, in words a person can read.
@@ -157,16 +222,24 @@ still to take.
## How it is checked
The rules here are [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)'s
and [ADR 0111](../../02-DECISIONS/0111-a-build-source-is-on-the-git-seat-or-external.md)'s, and each is
The rules here are [ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md)'s —
which supersedes [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)
and keeps every rule below except how the set is formed — and
[ADR 0111](../../02-DECISIONS/0111-a-build-source-is-on-the-git-seat-or-external.md)'s. Each is
checked as their tables say:
| Rule | Checked by |
|---|---|
| The set is closed, and every entry names its decision | 0110: a unit test on the set's size and decisions; manifest tests refusing an unknown seat or the wrong scope. |
| A seat is held by one assignment, and only by one whose module can hold it | 0110: resolution tests for a second holder and for a seat the definition does not name. |
| A requirement naming a seat is answered by its holder; a foundation seat cannot be named | 0110: resolution tests with a second provider on the consumer's node, with the seat unheld, and naming `mesh-store`. |
| Several providers and none local is a person's choice | 0110: an assignment test listing candidates with the seat's holder first and recording the pin. |
| `secret` is reserved | 0110: the parser and resolution refusals for another provider and a pin. |
| Holdings are derived, and the overview lists every seat | 0110: the `seats` command test, including an unheld seat. |
| The set is closed, and every mesh entry names its decision | 0118: a unit test on the mesh's own entries. **The refusal of an unknown seat is at registration, not in the parser** — correction of fact, 2026-09-27: a module may hold a seat *another* module declares, which is the point of naming the seat and not its provider, so whether a claimed name exists is a fact about the whole catalogue and a manifest in isolation cannot be judged on it. Registration tests cover an invented name and a name another module declares; the parser still refuses a claim on the mesh's own `mesh-*`/`node-*` namespace and a scope that disagrees with a declaration in the same manifest. |
| The set is derived, and enumerating it is a query | 0118: the overview lists the mesh's own plus every registered module's, asserted against a fixture mesh. |
| `mesh-*` is the mesh's, and a module may not declare one | 0118: a registration test refusing a manifest that declares any `mesh-*` seat, naming the prefix. |
| Two modules cannot declare the same seat | 0118: a registration test; the second is refused and the first untouched. |
| A holder satisfies the seat's protocol | 0118: a claim whose module does not serve what the seat declares is refused at assignment. |
| A seat is held by one assignment, and only by one whose module can hold it | 0118: resolution tests for a second holder and for a seat the definition does not name. 0131: `CanHold` is the one judgement, shared by registration and the handover, and its test follows the store's row. |
| A holder on record settles the seat; another eligible assignment is silent, not refused | 0131: resolution tests with a recorded holder on the same machine, on another machine, and under a seat's former name; without a record, the old rule's tests still pass unchanged. |
| A handover replaces the holder as one write, needs an assignment to point at, and goes with it | 0131: store tests — a second handover leaves one row; a handover to a module not assigned where named is refused; unassigning the holder removes the row. |
| A requirement naming a seat is answered by its holder; a foundation seat cannot be named | 0118: resolution tests with a second provider on the consumer's node, with the seat unheld, and naming `mesh-store`. |
| Several providers and none local is a person's choice | 0118: an assignment test listing candidates with the seat's holder first and recording the pin. |
| `secret` is reserved | 0118: the parser and resolution refusals for another provider and a pin. |
| Holdings are derived, and the overview lists every seat | 0118: the `seats` command test, including an unheld seat. |
| A build source on the seat records no address; an unheld seat refuses only self-hosted builds | 0111's tests. |
03-DESIGN/01-to-be/27-a-module-requires-the-mesh-resolves.md
+3 -3
View File
@@ -8,7 +8,7 @@ decisions:
- 02-DECISIONS/0115-one-assignment-of-a-module-per-node.md
- 02-DECISIONS/0113-the-vault-makes-every-secret.md
- 02-DECISIONS/0114-a-shared-credential-rotates-over-two-credentials.md
- 02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md
- 02-DECISIONS/0126-a-module-declares-its-own-seats.md
- 02-DECISIONS/0111-a-build-source-is-on-the-git-seat-or-external.md
- 02-DECISIONS/0084-which-provider-serves-a-consumer.md
- 02-DECISIONS/0046-a-module-configuration-is-its-assignments-not-its-manifest.md
@@ -64,7 +64,7 @@ Which module answers, in order:
1. **the holder of the seat the requirement names.** A requirement may name a seat instead of leaving
the provider open. It asks for *the mesh's* one, and the mesh answers with whichever assignment
holds that seat, with nothing asked of anyone. Unheld, the requirement is refused, naming the seat
([ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md),
([ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md) (superseding [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)),
[26 — The seats](26-the-seats.md)). Only a seat that delivers a provision can be named; naming a
foundation seat is refused, because it delivers nothing. A `secret` requirement always names
`mesh-vault`, because that provision is reserved;
@@ -199,7 +199,7 @@ containers, login, broker account and settings are keyed by it, as today, and a
tightest backend ([ADR 0049](../../02-DECISIONS/0049-a-consumers-identity-fits-the-tightest-backend.md)).
**A module may run on many nodes, and one assignment may hold a seat**
([ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)). The definition
([ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md) (superseding [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md))). The definition
says which seats the module can hold; the assignment says which it does. So the store module can run
on every node, one of those assignments holds `mesh-store`, and moving that role changes an
assignment, not a definition.
03-DESIGN/01-to-be/28-building-the-bus.md
+540 -45
View File
@@ -1,15 +1,21 @@
---
layer: to-be
status: proposed
code: []
updated: 2026-09-26
status: in-progress
code:
- mesh-catalog modules/nats
- mesh-controller internal/catalogue
- mesh-lab scenarios
updated: 2026-09-28
decisions:
- 02-DECISIONS/0116-the-bus-is-built-in-five-steps.md
- 02-DECISIONS/0106-the-bus-is-nats.md
- 02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md
- 02-DECISIONS/0126-a-module-declares-its-own-seats.md
- 02-DECISIONS/0074-the-wire-is-specified-not-the-types.md
- 02-DECISIONS/0079-the-foundation-seats-are-named-after-their-servers.md
- 02-DECISIONS/0100-a-node-in-use-is-adopted-before-it-is-converged.md
- 02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md
- 02-DECISIONS/0130-the-predecessor-is-ending-and-its-broker-goes-with-it.md
---
# 28. Building the bus
@@ -111,25 +117,153 @@ step 5 the rollout
## Step 1 — the module, and genesis raises it
> **Revised 2026-09-26** ([ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md),
> [design 29](32-what-a-module-declares.md)). Tasks 1.3 and 1.4 said the controller composes every
> account and creates *the four streams* at genesis, from a fixed set. That is only the mesh's own
> half. A module declares seats with their protocols, so streams are created **at registration**
> and durable consumers **at assignment** — neither of which has happened at genesis. The fixed
> foundation set stays here; the derived machinery moves to step 3, where the declaration model it
> reads from is specified. Tasks 1.1 and 1.2, already done, are untouched by this: the module and
> its reload mechanism do not care what the configuration says.
**Why here.** Everything else needs a server to talk to, and genesis is where the foundation is
defined. The mesh this is for will never travel this path — it is already running, and takes step 2
— but genesis is the definition every other path is measured against, and one that exists only on
paper is wrong until there is a second mesh to find out.
- [ ] 1.1 the `nats` module: manifest, image, one container, its client, TLS and monitoring ports,
- [x] 1.1 the `nats` module: manifest, image, one container, its client, TLS and monitoring ports,
JetStream on a named volume — the shape of design 25 §5, and the same shape the broker module
beside it already has
- [ ] 1.2 the composed configuration as a **directory** resource, and the entrypoint that watches
- [x] 1.2 the composed configuration as a **directory** resource, and the entrypoint that watches
the one file and signals the server itself — design 25 §5's correction, kept inside the module
because a container has no reload and a recreate would drop every connection the mesh has
- [ ] 1.3 the controller composes that file: accounts, permissions, TLS, JetStream — permissions
derived from `emits` and `consumes` and nothing else, plus each user's own ack subject and its
own inbox prefix (design 25 §4)
- [ ] 1.4 the four streams, created at genesis and asserted idempotently on start, by the controller
as their only writer
- [ ] 1.5 genesis raises it as foundation, claiming the seat **`mesh-broker`** — the seat is the
server's role, not the product
- [ ] 1.6 the genesis-broker bed
- [x] 1.3 the controller composes that file: accounts, permissions, TLS, JetStream — a user's
permissions derived from its declaration and nothing else, over the three namespaces of
[design 29](32-what-a-module-declares.md) §2, plus its own ack subject and its own inbox
prefix (design 25 §4)
- [x] 1.4 the mesh's own streams, created at genesis and asserted idempotently on start, by the
controller as their only writer — **the mesh's own, not all of them**: a seat's streams are
created when the module declaring it is registered, and a module's durable consumers when it
is assigned, so this task is the fixed foundation set and 3.x carries the derived rest
- [x] 1.5 genesis raises it as foundation, claiming the seat **`mesh-broker`** — the seat is the
server's role, not the product. **Already true of the controller and needed no change**: it
resolves the broker by seat ("that is where the broker is, whatever else the topology says")
and names no broker module anywhere in its source. What remains is naming `nats` instead of
the deprecated broker where a genesis module set is declared, which is scenario and installer
configuration — carried with 1.6 rather than before it.
- [x] 1.7 **the composition, delivered** — the controller gathering its principals, composing the
file, and asserting the streams and consumers on start.
**In**: the user list is derived from the mesh's records and the credentials are kept.
A bus user's bcrypt hash is now recorded, keyed by the username the file needs, and the
plaintext is returned exactly once. That state is new and the reason is worth stating: on the
bus the mesh runs on today an account is a management call — mint, hand over, seal to the
holder, keep nothing — and that works because the broker remembers. Here the users are one
file rewritten whenever any of it changes, so keeping nothing would mean **the first person's
access change silently blanking every module's password**.
**Permissions are not kept, only credentials.** Authority is derived from what each module
declares every time the file is written ([ADR 0043](../../02-DECISIONS/0043-a-module-broker-account-is-scoped-by-emits-and-consumes.md));
a stored permission list would be a second account of a user's authority, able to disagree
with the records it came from while both looked internally consistent.
The derivation refuses two things where they can still be named: two users with one name — the
server reads the file as one of them and which one depends on the order — and a module
assigned but absent from the catalogue, which would compose a user with no authority and fail
on its first publish with an authorisation error that says nothing about a missing manifest.
A user the mesh has minted no password for is *named* rather than dropped or written as a user
anybody is: an ordinary situation with an obvious remedy, and the caller decides whether a
partial file is worth writing. A seat's protocol is gathered across the whole catalogue, not
from one manifest, because a seat is declared by one module and held by another.
**Out, and what each needs.**
**Delivery is in, and it settled what a module declares.** The mesh writes the *accounts* and
the module owns its *server*. The alternative was a manifest field enumerating ports, TLS
paths and a store directory so the controller could write a whole configuration — wrong,
because those are properties of the container the module raises and the controller would have
to be kept in step with a Dockerfile it never sees. So a module declares its own configuration
as a file resource and `bus-users` names where the mesh's half goes beside it; **asking is not
enough to receive it**, because that file holds every user's password hash, so the claim on
`mesh-broker` is what authorises it.
Two things a running server changed. **An absolute include path is resolved relative to the
including file's directory** — `include /etc/nats/accounts.conf` from another directory makes
the server look for it *under* that directory and refuse to start — so both files share one.
And **`verify: true` was refusing every connection in the mesh**: it makes the server demand a
*client* certificate, and nothing in the mesh presents one — a host pins this server's exact
certificate and authenticates with the password the mesh minted ([ADR 0004](../../02-DECISIONS/0004-a-node-and-how-it-joins.md),
design 25 §4). Every connection would have died at the TLS handshake before any password was
looked at, with an error that reads as a fault in the client. Removed; TLS is still required,
because the block is what requires it and `verify` only decides whether client certificates
are checked. **Design 25 §4 should say this**, and says nothing about it today.
Also collected here: task 1.2's payoff, end to end against the module's own image — the user
list rewritten, the module noticing and reloading the server itself with no signal from
outside, and the connection the mesh already had still working afterwards.
**Minting is in, on both halves.** A node at enrolment, a module when its credential is
issued. Three things differ from a management call and each is the point of the move: the
credential is minted into the mesh's records and becomes usable at the next composition, so no
server need be reachable for it; the password travels beside the address rather than inside it,
because a credential embedded in a URL leaks into every log line that prints a connection; and
a module's durable consumer is derived from what it declared rather than named, so it cannot ask
for delivery of something it did not say it consumes. A node reconnecting may be refused until
the composition reaches the machine running the bus — which is what the host's reconnect backoff
is for, where waiting for the push would hold an enrolment open for as long as a declaration
takes to apply.
**Which bus is one fact, and being told about both is refused at start.** Not warned about: a
mesh half on each is one where a declaration goes out on one bus and the report comes back on
the other, and every component logs success while it happens — ADR 0074's failure arriving
through configuration instead of through code. A node that came away holding a credential for
each could be half-moved, and nothing would say which half.
**The objects are asserted on every start**, not created once at genesis: a stream somebody
deleted, a mesh raised from a restored backup, or a bus whose data directory was replaced all
have records and no objects, and a node whose consumer is missing hears nothing while everything
else about it looks correct. Against a real server: every object accepted, asserting twice
changes nothing (a start that failed the second time is a controller that cannot restart), a
machine joining an already-raised bus accepted, each node's consumer bound to its own
declaration subject and no other's, and CONTROL not dead-lettering — because the store window's
bound is the controller's, and a server that gave up first would discard the push the stream
exists to protect.
**People are not in the list**, deliberately: the account model is built and `operator issue`
is not (4.4), so there is nobody to derive. Left empty rather than guessed at.
> **This corrects a tick, not a decision.** Tasks 1.3 and 1.4 are ticked and they are honest
> about what they built — the composer, the derivation, the permission model, the stream and
> consumer definitions, the asserter, all pure and held by unit tests and a golden
> composition. What nobody wrote is the *caller*. Measured on the feature branch: outside the
> package that defines them, there is **not one** use of the composer, the permission
> derivation, the stream set, the stream asserter or the principal type. Step 1's "done when"
> claims "every account and permission composed from the manifests", and a mesh raised today
> would stand up a server with no user list at all.
>
> It also needs state the mesh does not keep. Design 25 §4 says the file holds bcrypt
> hashes, and passwords are "minted and sealed exactly as today" — but today the mesh mints a
> password, hands it to the broker through a management call, seals the plaintext to the
> holder and **keeps nothing**. There is no management call here, so the hash has to survive
> for every later recomposition: the first thing a person's access change or a new module
> touches is a file that must still contain every other user's password. No bcrypt hash is
> stored anywhere in the controller today.
>
> Named as its own task rather than folded into 1.3 so the gap is visible: the parts of
> step 1 exist and the mesh does not yet do any of it.
- [ ] 1.6 the genesis-broker bed — **deferred**: beds are run once, at the end, rather than per
step (novox/hq design 22's rule, and the operator's instruction). Every claim step 1 makes
is covered by a unit test or was demonstrated against the real server; what the bed adds is
the claims that need a mesh.
> **Not done here, deliberately.** The controller builds a module's broker credential as an
> `amqps://` URL and defaults a portless genesis address to 5671. Those are correct until the
> rollout and must not move: steps 1 to 4 leave every node on AMQP
> ([ADR 0116](../../02-DECISIONS/0116-the-bus-is-built-in-five-steps.md)), so changing the
> credential's shape now would break the running bus to serve a bus nothing speaks yet. They
> change with the links, in step 3.
**Done when.** A mesh raised from nothing has the server standing with the streams asserted and
every account and permission composed from the manifests; a user cannot publish outside its
@@ -149,11 +283,35 @@ and it is what makes steps 3 and 4 safe to develop against a live mesh. A runnin
a foundation module by being raised again; it adopts one in place
([ADR 0100](../../02-DECISIONS/0100-a-node-in-use-is-adopted-before-it-is-converged.md)).
- [ ] 2.1 the server raised beside the existing broker on its own ports, carrying nothing
- [ ] 2.2 the `nats` module adopted onto it in place, holding the data and configuration it was
raised with
- [ ] 2.3 the seat claim, and the resolver's refusal of a second holder mesh-wide
- [ ] 2.4 the adoption bed
- [ ] 2.1 the server raised beside the existing broker on its own ports, carrying nothing —
installer-side, from the upstream image
- [ ] 2.2 the `nats` module assigned, which **recreates the container once, deliberately** (see
below), keeping its JetStream directory
- [x] 2.3 the seat claim, and the resolver's refusal of a second holder mesh-wide — **already
true and now proved**: the refusal is generic to any mesh-scoped seat, and three tests pin
what matters for this one — a second bus anywhere is refused naming the seat, a *different*
bus implementation is refused for the same reason (which is what lets the bus be replaced
at all), and the deprecated broker no longer contends for it, so both run on one mesh
- [ ] 2.4 the adoption bed — deferred with the other beds
> **Adoption here is not a no-op, and pretending it would be is the trap.** The host keeps an
> existing container only when its spec matches the declaration exactly
> ([`apply.go`](https://git.novox.be/novox/mesh-host): *existed && before.Spec == want && running*
> → unchanged; anything else is `rm -f` and recreate). Genesis raises the server from the
> **upstream** image, because nothing has been built yet; the module declares the **mesh-built**
> artifact, which carries the entrypoint that reloads configuration in place. Those two specs
> differ, so assigning the module recreates the container.
>
> That is correct, and it is [ADR 0067](../../02-DECISIONS/0067-genesis-is-a-pivot.md)'s pivot
> exactly: raise a temporary thing, then reinstall it as an ordinary module. It is safe **only
> because it happens while the bus carries nothing** — which is what 2.1 means by "carrying
> nothing", and why step 2 comes before anything speaks NATS rather than after. One recreate, at
> the one moment it costs nothing.
>
> **After that, never again.** The configuration is a directory mount rather than a file, so
> rewriting accounts does not change the container's spec and the entrypoint reloads the server in
> place. That is the whole point of task 1.2, and this is the moment it pays: every later account,
> permission or person's access change touches a running bus with connections on it.
**Done when.** A mesh already running has the server adopted, holding `mesh-broker`; a second
assignment anywhere is refused at resolution — *one per mesh*; and every node is still on the old
@@ -166,19 +324,160 @@ quietly carried traffic would be step 5 arriving early and unrehearsed.
that decides what "agreeing" means for everything after it. It is the largest step and the one that
pays for itself furthest away.
- [ ] 3.1 **the suite first, on the bus the mesh has** — fixtures for the envelope and its required
headers, the contributions file, a served tool call and a grant, capturing what the three
implementations do *today*. Written first because a suite born on the new bus certifies
whatever the new bus happens to do
- [ ] 3.2 design 19 rewritten from exchanges, queues and routing keys to the subjects and streams of
- [x] 3.1/3.3 **the fixtures** — one directory in the sdk, read by each implementation's own
runner rather than copied into either, because a fixture copied twice is two fixtures. The
Go emitter and the runtime's NATS client both pass the first: every required header set,
each value in the pinned shape, the subject derived the same way, and the payload the body
alone.
**The suite also had to settle what "byte-for-byte" can mean**, which ADR 0074 stated and
nothing had yet had to implement. The envelope is exact — subject, required headers, names
and formats — because that is what two implementations get wrong invisibly. The body is
not: Go sorts a map's keys and JavaScript keeps insertion order, so identical bytes would
commit every implementation to a canonical JSON encoder, to buy a property the mesh never
uses. Read strictly it would have sent somebody writing one.
Still to capture: a served tool call, a grant and its answer, and the contributions file —
the other three ADR 0074 names.
- [x] 3.2 design 19 rewritten from exchanges, queues and routing keys to the subjects and streams of
design 25 §2–§3, per capability, with ADR 0074's model untouched: floor plus capabilities, an
implementation legitimate when it claims less, identity from the sealed credential, dedup on
`x-event-id`
- [ ] 3.3 the fixtures restated on NATS, and the capability each implementation claims
- [ ] 3.4 the controller's link on NATS
- [ ] 3.5 the host's link on NATS — mirroring, still importing nothing
- [ ] 3.6 the tool runtime's client on NATS, behind the unchanged sdk contract
- [ ] 3.7 the sdk's three stale comments, and nothing else in it
`x-event-id`. Claims checked against a running server are marked *verified* in the text, so
a reader can tell what was measured from what was reasoned. One limitation lifts with the
transport: a module may now call another's tool, which issue 049 recorded it could not.
- [x] 3.4 the controller's link on NATS — **both halves are through the seam, and the store
window is the server's.** `Bus` states the outbound in the mesh's words (publish an event,
declare to a node) and `Control` states the inbound (took it, dropped it, held it for the
store); each has an AMQP and a NATS implementation, and both ship, because steps 1 to 4
leave every node on AMQP and both shipping is what holds them to one envelope.
The outbound seam turned out to be eight call sites; the inbound was the larger half, and
the reason: every handler took the transport's own delivery type, so the loop could not move
without moving enrolment, reports, builds, upgrades and catch-up with it in one breath.
**The window (ADR 0083) is now what decides, once, for both.** On the bus the mesh has,
holding a message means an unacknowledged delivery kept in the controller, bounded by the
prefetch and lost if it stops. On the bus being built it is a `nak` with a delay: the
message stays the server's and the controller keeps only the moment it first could not take
it, so one that restarts mid-window has nothing to lose. Seven claims about that were asked
of a running server rather than reasoned — a report heard and gone from the work queue, one
held through a store outage and recorded when it returned, one let go once the bound passed,
a superseded one settled without being acted on, a heartbeat heard and nothing persisted,
both followed events acknowledged on a stream the controller had no ack subject for, and the
enrolment answer arriving at the address the request carried in its payload.
**Three things the wiring forced into the open.**
*Supersession is asked before the store, not after.* A report about a declaration the mesh
has moved past would otherwise wait out a restarting store to be written, and then overwrite
what the node is doing now.
*Half of a report is not about a declaration, and that half is never stale.* What the machine
**is** — the tunnel it took over, the ports its own bundle holds, what an adopted node found,
a node moving its overlay key — reaches the mesh on a report and nowhere else. A rekey set
aside as stale is a node whose overlay key never moves, and no retry is coming, because the
node said it once. So staleness is asked only of a report that is purely an apply's account.
*The controller could not have consumed a module event at all.* Its account granted no event
subject to subscribe and no ack subject on the events stream, so every announcement would
have been redelivered for ever, refused by the permission list it already had. Both are now
granted, each subject named rather than by pattern — a controller subscribing every event in
the mesh is a permission list that has stopped saying what it is for. Its consumers are
**named beside the mesh's own streams rather than derived**, because the controller files no
manifest and authority cannot come from a declaration that does not exist.
Still outstanding: a build's own shape, which travels with the builder in step 4.
- [x] 3.5 the host's link on NATS — **all three halves are through seams**, mirroring the
controller's and still importing nothing of the mesh's own (ADR 0005): the host's own
interfaces over its own libraries, agreeing with the controller only because a fixture holds
both to one envelope. A report goes through JetStream because it is the message the
store-window guarantee is about; a heartbeat stays on core, because a heartbeat in a stream is
the mesh's least valuable message competing for retention with its most valuable.
`Link` is dialling, hearing and saying in one interface, because **dialling is where the
transport is chosen** and choosing it twice is how one half of a node ends up on a different
bus from the other. `Asking` is the enrolment conversation, and it is separate for the
opposite reason: almost nothing about it is the same, and a node that fails there is not in
the mesh at all.
**What the new bus took away, and what it would not give.** A host declares nothing here: on
the old bus it declares its own queue, because a queue that is not there means a node that
hears nothing, but the object it reads through now is a durable consumer and a host's account
reaches no part of the JetStream API. So it **binds** to one the mesh made, and a missing one
is said as the mesh's to answer rather than quietly created with whatever the client defaults
to. Two things that had to be built for that: a node's declaration consumer (named after the
node, because its ack grant is derived from the node's name, so any other name is a delivery
it cannot acknowledge), and the enrolment user's **inbox** — design 25 §6 names it and the
composer granted none, so an enrolling node would have published its request and waited out
its timeout against a mesh that answered.
**The reply address travels in the payload, and that is now proved from both ends.** The
controller reads it from there (3.4) and the host writes it there and waits on it, and the
test asserts the transport's own reply field held the *consumer's ack address* by the time the
request arrived — so a future server that stopped claiming that field fails a test rather than
letting the reason quietly become folklore.
The host's **"newest wins" window narrows at the rollout rather than disappearing**, and that
is now measured rather than predicted: three declarations pushed to an absent node leave one
on the stream and it is the newest, so the catch-up half is the stream's — but three pushes to
a connected node are still three deliveries, which is the half that stays.
**The pin turned out easier here than in the tool runtime, not harder.** The Go client takes a
`*tls.Config`, so the same pinned configuration with the same verify callback does the work;
the subject-alternative-name constraint recorded under 3.6 is that client's, because it takes
PEM strings with no verify hook. A host checks the fingerprint and nothing else.
Nothing here composes an enrolment user per live token, and that is **1.7's**, not this
task's: it is one input to a composition that does not happen at all yet.
- [x] 3.6 the tool runtime's client on NATS, behind the unchanged sdk contract — round-tripped
against a real server: a tool answered across two connections, a throwing handler reaching
the caller as an error rather than a timeout, an event delivered once with its key, body,
node and event id intact. Ships beside the AMQP client and is selected at the rollout,
because steps 1 to 4 leave every node on AMQP.
**A constraint it surfaced, recorded where somebody issuing a certificate will look.** The
AMQP client pinned the exact certificate and switched hostname verification off, which is
sound because a fingerprint is stronger than a name. The NATS client exposes no equivalent
hook — its TLS options are PEM strings with no verify callback — so the pin still happens
before dialling and the library's own name check happens beside it. **The bus's certificate
must carry a subject-alternative name matching the address nodes dial it by**, or the
connection is refused by a library error rather than by anything the mesh says.
- [x] 3.7 the sdk's three stale comments, and nothing else in it — three lines, which is the
whole of the sdk's diff for the bus change, and the measurement that predicted it
- [x] 3.8 **the declaration model** of [design 29](32-what-a-module-declares.md): local names
derived to subjects, the three namespaces, permissions computed from a declaration, and a
manifest that contains no subject. Done in the controller's composer (permissions, streams,
consumers), in the runtime's client (subjects derived from the credential, never named by a
module), and as a catalogue test asserting all 72 manifests hold no subject — because the
rule held by construction, and a rule held by construction is one a later field breaks
quietly.
- [x] 3.9 **seats declared by modules** — the manifest now carries `seats` (name, scope,
accepts/emits/serves, retention) and `uses`, and registration refuses a `mesh-*` name, a
duplicate declarer, an undeclared `uses` or claim, a seat with no protocol, a scope
mismatch, and a holder that does not answer what its seat promises. **Still to do**:
creating a seat's streams at registration and its holder's work-queue consumer at
assignment, which need the JetStream client wired in.
The refusal for an unknown claim *moved* rather than disappeared — the parser cannot judge
it from one manifest any more, because another module may legitimately declare that seat,
so it is registration's. The test that encoded the old rule was rewritten rather than
deleted, and a second one pins the case the parser could not distinguish.
**Done**: a seat's work queue is derived and created, and a holder's worker with it. The
JetStream client behind them is wired and verified against a running server, which also
completes 1.4's missing half — the pure `Asserter` had no implementation until now.
- [x] 3.10 **the ten seat renames** — done in the controller's table, the ten manifests that
claim them, the controller's own shipped manifests, and every test. Not a migration after
all: a holding is derived at resolution, never stored, so nothing recorded points at an old
name (recorded as a progressive insight on ADR 0126). A **kept** rename table tells a
manifest written against an old name what it became, because a module lives in its own
repository and may be registered long after the catalogue stopped using one.
**A seat and the interface it delivers are different names.** The `git` seat became
`mesh-git` while the `git` *provision* it delivers did not change, and the same for the
package registry. A blanket replace got this wrong first and the failure read "the package
registry is served on `<nil>`", which does not say "you renamed an interface" — so a test
now pins every seat against the interface it delivers.
**Done when.** The fixtures are produced and consumed byte for byte by every implementation that
claims the capability, and a module built before any of this serves its tools unchanged on the new
@@ -196,6 +495,17 @@ module.
**Why here.** The links exist from step 3, so the flows that are not on the bus at all can move onto
it, and the beds that need a mesh living on NATS can finally run.
> **A blocker surfaced here that is not this step's to fix.** Every event name in the catalogue is
> still written the way a routing key on the bus the mesh has is written, so the derivation design 29
> §1 specifies turns a consumer's declaration into a subject **no emitter publishes** — thirty-seven
> manifests, and one that cannot be composed at all. Nothing fails on the bus the mesh runs on
> today, where a routing key is matched literally; it fails on the first mesh raised on the new bus
> and not before, which is why wiring the controller's own subscription is what found it. Opened as
> [issue 127](../../04-ISSUES/127-a-module-event-derives-a-subject-nothing-publishes/00-report.md).
> It holds 4.2, 4.3 and the catch-up half of 4.5; the node-facing flows — enrolment, reports,
> heartbeats, a build's outcome — are unaffected, because those subjects are the mesh's own and
> derive from nothing a module declares.
- [ ] 4.1 **the full genesis bed** — a mesh raised on NATS from nothing and living on it: a node
enrols over TLS with a claimed token and the enrolment user cannot read a declaration; a push
is held while the store restarts and applies after, nothing lost or duplicated; a node that
@@ -204,13 +514,111 @@ it, and the beds that need a mesh living on NATS can finally run.
held by a `nak`-with-delay cycle still reaches the enrolling node, proving the reply travels
in the payload and not the transport field the consumer's ack has claimed. The server-enforced
permissions were proved at step 1 and are not re-proved here
- [ ] 4.2 a build source's change reaches the builder over the bus, and the build that follows is
the one the change asked for
- [ ] 4.3 an installation completes over the bus, with the same outcome as the path it replaces
- [ ] 4.4 a person's client: the account, the client that speaks the bus, and the tool surface over
it (design 25 §7) — a module's tool invoked from another node and from a person, refused from
an account that may not
- [ ] 4.5 reports and catch-up: a node that was unreachable catches up rather than losing them
— **nothing is outstanding but the bed itself.** Both links speak NATS, the composition
happens, and every claim above has a unit test or a check against a running server behind it.
What none of them can stand in for is a mesh raising itself, which is what this bed is — so this
is where the code stops and the lab starts
- [x] 4.2 a build source's change reaches the builder over the bus, and the build that follows is
the one the change asked for — **a build is work submitted to a role now**
([ADR 0129](../../02-DECISIONS/0129-a-seat-carries-the-protocol-of-its-role.md)). Both sides
are behind a seam with an implementation per bus, and on the bus being built one publish does
what two did: the outcome is the role's own event, so the asker matches it by the id its
request carried, the controller records it and the catalogue places it in the graph. A build
machine needs a reply queue for nothing and a grant over nobody's inbox.
Checked against a running server: the round trip; a third party on the role's event hearing
the same outcome the asker did, which is what the decision rests on; work leaving the queue
once settled, so no second machine repeats it; work submitted with no machine holding the role
**waiting rather than failing**, and being done when one arrives; and work a machine handed
back coming round again.
The outcome carries the module name, because only the manifest says what was built and one
message now has three readers. A failed build names none: it produced no module version, and
the catalogue would otherwise place something that was never made.
- [x] 4.3 an installation completes over the bus, with the same outcome as the path it replaces —
**the installer can raise it**: a foundation template that stands up the server, writes the
server's own settings and the mesh's first user list beside them, and starts a controller
reaching the new bus. What remains is running it, which is 4.1's bed.
**The mesh composes its own user list, and at genesis there is no mesh to compose one.** So the
installer carries the first — the controller's account at a well-known bootstrap password,
exactly as the store is reached at `postgres:bootstrap` and the old bus at `guest:guest`, and
rotated with them. From the controller's first composition onward the file is the controller's.
That surfaced a gap reading would not have found: the controller's own account exists before
there is a controller to mint one, so nothing recorded a hash for it and its first composition
would have left the writer out of the file it was writing — a bus nothing can connect to,
produced by the thing connected to it. It records a hash of the credential it is using, and only
when none is recorded, so a restart cannot put the bootstrap password back over a rotated one.
**The carried list and the derived one are checked against each other**, because they are two
statements of one fact and a mesh cannot be raised twice to find out they disagreed. A template
granting less than the controller derives produces a mesh that comes up, connects, and is
refused on its first act, with an authorisation error naming a subject rather than the template
that forgot it. The check earned itself at once: the composer was granting a role's whole event
branch *and* the one event it follows, and the wider grant wins — so only the submitting half of
a role is granted now, and what comes back is named exactly.
- [x] 4.4 a person's client — **the account and the program are both in.**
**The account**: a person is not a module and holds no seat, so their authority is a list of
tools (or `*` for an administrator) and nothing else. Held to four properties, each a way of
being wrong that would not announce itself: nothing but tools, so a person cannot claim a
module said something; no ack subject, because authority over a consumer that does not exist
is authority nobody audits; no ability to answer, because a person who can answer a request is
impersonating a module on a bus where anyone may serve a tool; and two people do not share an
inbox. Issued, listed and revoked by command; stating what somebody may call replaces what was
there, because a list that could only grow is a permission nobody can take back; and forgetting
somebody takes their credential with them, or it is not a revocation.
**The program**: two surfaces over one thing — a command line and an MCP server — both adapters
over the same three calls, because a second way of reaching a tool is a second thing to keep
correct. It uses the client a module's runtime uses, so what a person may do is answered by the
same permission list that answers it for a module and an audit has nothing separate to read.
Three decisions in it worth keeping. It lists what the **catalogue** has rather than what this
credential may call: somebody seeing only their own tools cannot tell "not installed" from "not
yours", and those need different people to fix them. A failed call says which of three things
happened — nobody serves it, this credential may not, or the tool was slow — because the
remedies are in three different places and without that they are one timeout and a stack trace.
And the MCP surface decides nothing: the names are the ones a person types, the schemas are the
modules' own, an answer is passed through unshaped, and a tool that fails comes back as a tool
error rather than a protocol error, because the request was well-formed and the mesh answered it.
Both surfaces are driven against a running bus, including a host's notification being answered
with nothing and an unknown method refused.
> **Design 25 §7 says "nothing is built of this before §10's bed passes", and this was built
> before.** Recorded rather than quietly ignored: the operator asked for it, it is on the
> critical path for nothing and blocked by nothing, and the bed it waits for is 4.1's. If the
> bed changes what a person's client should be, this is what gets changed.
- [x] 4.5 reports and catch-up: a node that was unreachable catches up rather than losing them.
**The reports half is in and proved against a server** (3.4): held through the store's absence by
the server rather than by the controller, superseded ones settled by the digest they carry.
**The catch-up half needed nothing built, and that was the answer.** It existed because a queue on
the bus the mesh runs on today receives only what is published after it is bound, so everything
built before the catalogue existed was announced to nobody — and on a fresh mesh that is always
the foundation, because those are the things the catalogue needed in order to exist
([issue 050](../../04-ISSUES/050-the-catalogue-knows-nothing-built-before-it/00-report.md)). A
whole mechanism followed: the catalogue asks, the controller re-publishes.
A stream is a log and a consumer is a position in it. A consumer created later starts at the
beginning, so the builds are simply there — asked of a running server rather than assumed, since
the decision rested on it: three builds published with nothing listening, then a consumer created,
and all three waiting for it. So the question of *who replays* has no answer because nothing
replays.
> **This is the shape of the whole change, in one task.** Three ways to do the replay were weighed
> — a namespace for the mesh's own voice, the controller answering a question, a consumer reading
> from the start — and the right answer was that the bus being moved to already does it. The
> mechanism was never about builds; it was about a queue that could not remember. **A conversion
> that carried it across would have carried a workaround for a limitation that no longer exists**,
> and nothing would have looked wrong.
Retiring it is step 5's, with the rest of what only the old bus needs: the request, the
re-publishing, and the `replay` flag that told a consumer to register history without acting on it.
**Done when.** Each converted flow is proved against the behaviour it replaced, and the full genesis
bed is green. **Observation is not in this step** — heartbeats, conditions and key-value state are
@@ -221,16 +629,101 @@ reserves them for after the move, and a flow built ahead of its design would be
**Why here.** It is the only step that moves a node's bus, and it moves every node's at once.
- [ ] 5.1 the cutover bed: a mesh on AMQP with a predecessor stand-in on the compatibility broker
**The order the repositories land in is part of the rollout, not paperwork.** Derived 2026-09-27
while merging, and not obvious from any one repository, which is why it is written here rather than
left to be re-derived under time pressure:
| order | repository | why it cannot be later |
|---|---|---|
| 1 | this one | prose; nothing deploys |
| 2 | the sdk | comments only, and no module rebuilds for it |
| 3 | the client library | it is what a module calls to emit, and it is where the subject is derived. Until it lands, a locally-named event is published under the local name itself |
| 4 | the catalogue | every manifest and every module's code, renamed together. Safe only once the runtime derives |
| 5 | the controller | **it refuses an old-style event name outright**, so landing it before the catalogue makes every unconverted module unregisterable |
| 6 | the hosts | last, because nothing else waits on them |
Two properties make the sequence safe rather than merely ordered, and both are pinned by tests. A
name already in the old form passes through the derivation untouched, so a module nobody has
converted keeps working at every step. And a converted name derives to **exactly** the key the old
bus published, so steps 3 and 4 change nothing on the wire — the move to the new bus is step 5.2 and
one environment variable, not a side effect of deploying.
The failure this ordering avoids is issue 127's own: a publisher and a subscriber that disagree about
a subject produce no error anywhere. Nothing logs, nothing retries, and the mesh reports itself
healthy while reacting to nothing.
- [ ] 5.1 the cutover bed: a mesh on AMQP with a predecessor stand-in on the deprecated broker
moves its bus in one rollout, every node reporting on NATS afterwards, the stand-in's own
client still connected throughout
- [ ] 5.2 the rollout: accounts composed, then the controller, every host and every runtime
together; every node confirmed heard before AMQP stops
- [ ] 5.3 the mesh's accounts removed from the compatibility broker, leaving the predecessor's users
- [ ] 5.4 the compatibility broker retires when its condition holds — no client connected for the
period the operator sets
- [x] 5.2 the rollout: accounts composed, then the controller, every host and every runtime
together; every node confirmed heard before AMQP stops.
**Done when.** Every node reports on NATS and the predecessor's clients never noticed.
**Done 2026-09-28, 02:25.** Every machine reports on the new bus, the seat is held by the
module that provides it, the old broker is unassigned and forgotten, and every credential was
minted afresh at the end because two had been printed on the way. What it took, in the order
it was found, each fixed on the trunk before the next step: the control plane's `serve` and
`push` never selected the new transport (task 4.3, open until then); a machine's user was
granted neither the asking nor the delivery of its own consumer; the account had no JetStream
of its own; the control plane's client verified the bus's certificate by name instead of
pinning it; the seat table's rows carried no protocol, so no role's work queue was raised; the
build machine decided its bus from a variable its container never received; and a rotation
put new hashes on the bus before three machines had received their new memberships — which
is why there is now `rollout hand <node>` and a host adopts a delivered membership at start.
The bootstrap loop — a bus that can only be raised by a declaration that can only arrive
over that bus — was broken once, by hand: the mesh's own composed configuration started the
server, and the controller binary was run on the node directly until the managed container
could be rebuilt over the bus it was on.
- [x] 5.3 **the seat changes hands as one act.** A command takes a seat and the assignment taking it
over, and the seat is never empty in between — the emptiness is the outage of 2026-09-27, when
the control plane, which finds its own bus through this seat, lost the address and looped.
**Built 2026-09-27** (`seat_holding`, migration 0039; design 26 says how it is checked), and used
live the next night to hand `mesh-broker` from the old broker's assignment to the new one's. This
is what 5.2 uses to move `mesh-broker` from the old
broker's assignment to the new one's, and it is built first ([ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md)).
- [x] 5.4 **the old broker and everything that named AMQP leave the mesh** ([ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md),
superseding [ADR 0127](../../02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md)): the two modules that
required `amqp` are removed, the broker's module is unassigned and removed (**done 2026-09-28**; the predecessor's own tooling, which rode the same adopted broker, went dark with it, as [ADR 0130](../../02-DECISIONS/0130-the-predecessor-is-ending-and-its-broker-goes-with-it.md) accepted), registration refuses
a manifest that provides or requires `amqp`, and a whole-catalogue check asserts none does. Not
a retirement condition — a decision, taken, with the operator's "I don't care if the predecessor
breaks" on record ([ADR 0130](../../02-DECISIONS/0130-the-predecessor-is-ending-and-its-broker-goes-with-it.md)).
Retiring with it: the build outcome's second announcement under the module's own name, which
existed only so a catalogue deployed before the rename and one after both heard it.
> **The remote tooling goes with it too.** The predecessor's own mesh talks over that broker, so
> shutting it down ends the path that reaches this installation's machines from a workstation.
> The rollout is driven from the node, or before the broker stops — a sequencing constraint on
> 5.2, not an afterthought.
- [x] 5.5 **the AMQP transport is deleted from the control plane and the hosts**. One bus, nothing
to select ([ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md)).
**Done 2026-09-28.** The control plane's old consume loop, build request, tool call, management
API and account scoping went, and the host's old dialling and enrolment paths with them; a
membership or token naming any other bus is refused before anything is sent. Nothing selects a
transport any more: the variable that once did (`MESH_BUS_NATS`) now only names where the
control plane reads its own bus credential, the way any module reads a secret. **Checked by the
build**: neither repository's module file names the AMQP client library, so a line that still
used it would not compile. The store-window guarantee ([issue 083](../../04-ISSUES/083-other-control-messages-are-lost-while-the-store-restarts/00-report.md))
is tested against a bus-less fake rather than the old transport's memory, which is what let
that memory go — the one thing it did that the stream does not (superseding a held report) is
the staleness check on the message itself (design 25 §3).
Found on the way: **no build had ever recorded what it stood on.** A recipe reads its base from
a build argument, so the digest was never in the file the builder derived edges from, and every
order that says *bases first* — `build --on`, `build --behind`, the merge follow-up of
[issue 131](../../04-ISSUES/131-nothing-tells-the-mesh-a-source-moved/00-report.md) — walked a
graph with no edges. The builder now reports the bases it was handed, the control plane records
them by artifact path, and the graph is read from the newest build of each module — a recorded
manifest carries no `build.on`, so the edge is derived from the build or it does not exist.
> **The old 5.4 note is history.** It recorded that a retirement *condition* was wrong from
> [ADR 0127](../../02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md) onward, which framed the old broker
> as an ordinary provider with no end. [ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md) ends that
> framing in turn: the broker is not kept as a provider either, because AMQP is not a provision. Both
> readings are kept here so the two reversals can be read in order.
**Done when.** Every node reports on NATS, and nothing of the mesh's own is left connected to the
deprecated broker.
## The through-line
@@ -245,8 +738,10 @@ itself moves once, at the end, on one day.
- **Observation** — research 017's, after the move, by its own design.
- **Leaf nodes** — design 25 §11 keeps this out of scope and says so; a leaf per machine is a later
question, noted so it is not forgotten.
- **The predecessor's world.** It is AMQP, it cannot move, and it does not need to: its broker is
the compatibility module until its last client is gone.
- **The predecessor's world.** It is AMQP and it is not moving —
[ADR 0130](../../02-DECISIONS/0130-the-predecessor-is-ending-and-its-broker-goes-with-it.md): it is
deprecated, some of it is still running, and it is being left to stop rather than migrated. Its
broker goes with it, unassigned like any provider whose provision nothing requires.
## How this list is kept true
03-DESIGN/01-to-be/29-a-node-has-operator-accounts.md
+124 -30
View File
@@ -5,7 +5,10 @@ code: []
updated: 2026-09-27
decisions:
- 02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md
- 02-DECISIONS/0120-a-roster-fact-carries-its-format-as-a-template.md
- 02-DECISIONS/0051-shared-data-is-the-operators.md
- 02-DECISIONS/0113-the-vault-makes-every-secret.md
- 02-DECISIONS/0117-a-machines-uplink-is-a-seat.md
---
# 29 — A node has operator accounts, and the mesh owns what lives under a home
@@ -18,7 +21,7 @@ owned by, who a user service runs as, and — the case that surfaced this — wh
person's `~/.ssh/config`, `~/.zshrc`, `~/.config`); the mesh, taking those over, kept the machine
facts and dropped the human one.
Two things are missing, and they are one idea:
Several things are missing, and they are one idea.
## 1. The account is a node fact
@@ -28,17 +31,14 @@ mesh already knows the node and its address, so `<account>@<node>` is then a com
because it is exactly the fact that was silently lost — `ssh ace` failed to `ace` because nothing
in the mesh said ace's account is `ace`.
It is **not** a credential. The account names a login; the key that authorises it is the
operator's, placed as a secret or an operator-owned file, never minted by the mesh (ADR 0051).
## 2. A resource may live under a home, owned by its account
[ADR 0112](../../02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md) placed a
module's *system* data — `<root>/<module>`, owned by the module. It has no analog for the other
half of the filesystem: the things that belong under a person's home and are owned by that
person. `~/.ssh/config`, `~/.ssh/config.d/mesh`, `~/.zshrc`, `~/.config/hal` — every one of these
is a resource the mesh should be able to place and own, resolved against **the account's home**
rather than a system root, and chowned to **the account** rather than to root or a module uid.
person. `~/.ssh/config`, `~/.zshrc`, `~/.config/hal` — every one of these is a resource the mesh
should be able to place and own, resolved against **the account's home** rather than a system
root, and chowned to **the account** rather than to root or a module uid.
This is the same move as `${dir:…}`, one level over: a resource says `home: <account>` (or names
an account requirement), and the mesh resolves the home directory and the owning uid on the node
@@ -46,39 +46,133 @@ that account lives on. A module that writes operator config — the eventual rep
`hal/terminal`, `hal/claude-code`, `hal/secrets` — declares its files this way and names no
`/home/...` path, exactly as a system module now names no `/var/lib` path.
These are a **family**, not one module: an `ssh-client` module, a shell module, a `~/.config`
module, each a *universal-tier* consumer of the account fact — assigned wherever a person logs in,
which is every node, unlike the graphical stack that a capability gates.
## 3. The whole of `~/.ssh` is the mesh's — with one boundary drawn inside it
The predecessor owned a single file (`~/.ssh/config`) and left the rest alone; it drifted, because
owning one file beside foreign ones is not owning anything. The mesh should own **the directory**:
create `~/.ssh` at `0700`, chown it to the account, and own the files it places there —
- **`config`** (or the mesh's region of it): the `Host` blocks for every other node, composed
from the roster;
- **`known_hosts`**: authoritative, so the "Host key verification failed / accept-new" dance that
cost real time during enrolment simply ends;
- **`authorized_keys`**: who may log into this account, governed centrally rather than by whichever
key happened to be pasted where.
**The boundary — and it is the reason this is safe:** `~/.ssh` is the one directory where a wrong
declaration locks a person out of their own machine. So the mesh's *found-vs-owned* semantics
([ADR 0126](../../02-DECISIONS/0118-undeclaring-gives-a-unit-back-the-state-it-was-found-in.md),
adoption) apply *inside* the home directory. The mesh **owns** the directory and the files above; it
**holds as found — never rewrites, never removes** — the operator's own contents: their **private
keys** and their **personal drop-ins** (`config.d/personal`, the personal `Host` aliases a
workstation carries, exactly as `hosts.local` is the home the mesh never rewrites for `/etc/hosts`).
Reconcile removing an unassigned `config.d/mesh` is fine; the same logic aimed at `id_ed25519` or an
operator's own `authorized_keys` entry is a lockout. This is the login-channel cousin of the rule
[ADR 0125](../../02-DECISIONS/0117-a-machines-uplink-is-a-seat.md) draws for the uplink and the sshd
module draws for the firewall: **the mesh must never be able to arrange the one failure that severs
its own way back in.** The carve-out is not a convenience; it is that rule, in `~/.ssh`.
## 4. Keys are the mesh's to generate — through a CA, and existing keys are adopted, not replaced
Key *generation* is the mesh's, not each node's improvising its own. The clean form is an **SSH
certificate authority as a seat**, the sibling of the TLS internal CA the mesh already runs:
- **Host certs.** The mesh signs each node's host key. Every node's `known_hosts` becomes one line
— `@cert-authority *.<suffix> <mesh-CA-key>` — and nothing is distributed per node; a new node is
trusted the instant its host key is signed.
- **User certs.** The mesh signs a cert naming the principals (accounts) allowed. Every node's
`authorized_keys` / sshd `TrustedUserCAKeys` becomes one trust line — no N×N key spraying — and
short-lived certs give rotation for free
([ADR 0114](../../02-DECISIONS/0114-a-shared-credential-rotates-over-two-credentials.md)).
- The **CA private key is the mesh's**, a secret the vault makes
([ADR 0113](../../02-DECISIONS/0113-the-vault-makes-every-secret.md)).
**Three kinds of key, and only one is never minted.** Host keys (server identity) and pure
machine-to-machine keys the mesh may generate end to end. The operator's **personal** private key —
possibly on a hardware token, possibly used from an off-mesh laptop — the mesh **signs into a cert
but never generates**; that, and only that, is the residue of
[ADR 0051](../../02-DECISIONS/0051-shared-data-is-the-operators.md). So "keys are mesh-owned" and
"the operator's login key is the operator's" reconcile: the mesh owns the CA and the signing; it
holds the human's private half, never mints it.
**Existing keys are not lost.** Taking ownership is *adoption*, not regeneration: a key already on a
machine is recorded and signed, not overwritten. The mesh gains authority over `~/.ssh` — it does
not clear it. An enrolling node's host key and the operator's existing key are carried forward; the
found-vs-owned boundary of §3 is exactly what guarantees nothing already there is destroyed.
## 5. How it is distributed: the controller composes, the node applies
None of this needs a node to discover the mesh, and none of it needs a control-plane module of its
own. The ssh files are **roster facts**
([ADR 0128](../../02-DECISIONS/0120-a-roster-fact-carries-its-format-as-a-template.md)): once the
roster view carries a node's **host key** and its **account** beside its name and address, the
`ssh-client` module ships a template for `known_hosts`, `config` and `authorized_keys`, and the
controller renders each node's copy from the full roster and pushes it. The mesh owns the data; the
module owns ssh's format; the control plane gains no ssh syntax. It is the same act as composing a
peer list or `/etc/hosts` — which is why there is **no novox-only "mesh-ssh" module**: the
centralization is the controller's composition, not a module that runs somewhere. Only non-secret
facts travel (names, addresses, accounts, host keys, the CA public key); the private key stays the
operator's, placed as an operator-owned file, referenced by path.
## 6. The two modules, and the seat between them
- **`sshd`** (server, every node) — manages sshd, owns and **reports** its host key so the roster
carries it, and trusts the user CA.
- **`ssh-client`** (client, every node) — owns `~/.ssh` per §3, consumes the roster and the CA
public key.
- **`the-ssh-ca`** (a seat, held on the control node) — signs host and user certs.
They meet at the account and the CA, not at a bespoke module. The `sshd` server side already exists;
the client/identity side and the CA are the open pieces.
## Why now, and why not yet
**Why it matters:** when HAL retires, the generators that keep `~/.ssh/config`, shell config and
the operator's `~/.config/hal` current retire with it. Without this, adding a node stops adding
its ssh alias, and a fresh machine has no operator dotfiles at all — the mesh would run every
service and leave the human unable to work on the box. The account is also load-bearing for
correctness already: `ssh <node>` (issue 122's cousin), user-scoped systemd units, and any file a
person rather than a daemon must own.
**Why it matters:** when HAL retires, the generators that keep `~/.ssh`, shell config and the
operator's `~/.config/hal` current retire with it. Without this, adding a node stops adding its ssh
alias and its trust, and a fresh machine has no operator dotfiles at all — the mesh would run every
service and leave the human unable to work on the box.
**Why not build it reflexively:** it is a real addition to the node model and the resource model,
and it must be gotten right, not smuggled in beside a firewall fix. Open questions to settle
first:
**Why not build it reflexively:** it is a real addition to the node model, the resource model, and
the seat set, and must be gotten right. The mechanism half is now settled — ADR 0128 is what lets
the ssh files be templates with no control-plane format — so what remains to decide here is the
model:
- **One account or several per node?** A workstation has one human; a shared box might have more.
The model should allow more than one without forcing the common case to name it.
- **Where the login key lives.** An operator-owned file (ADR 0051) or an accepted secret — never
minted. The account fact and the key that authorises it are separate, and only the first is the
mesh's to generate.
- **The boundary with `sshd`.** The `sshd` module (server side) already exists. This is the
*client* and *identity* side: the account a node offers, and the home-scoped files an operator
needs. They meet at the account but are not the same module.
- **Multi-operator.** Today there is one human. The model should not assume it, but the first
cut may serve one and leave the shape open.
Allow more than one without forcing the common case to name it.
- **The CA's shape.** Host-cert and user-cert principals, cert lifetime and renewal, where the CA
runs (a seat on the control node). The one thing fixed: the operator's personal key is signed,
never minted.
- **Adoption of existing keys.** How an enrolling node's host key and an operator's existing key are
recorded and signed rather than replaced — the found-vs-owned boundary, made concrete for keys.
- **The `sshd` boundary.** Server side exists; this is the client, the identity, and the CA.
- **The ssh-agent.** An agent is a *user-scoped service running as the account* — the first concrete
case of the user services §2 anticipates. It holds the operator's private key in memory; the mesh
declares the unit and sets `AddKeysToAgent`/`IdentityAgent` in `config`, and still never sees the
private half. Agent *forwarding* wants a policy, not a default: with user certs it is largely
unnecessary, and forwarding an agent into a node exposes the operator's keys to that node's root —
so prefer certificates and `ProxyJump` over forwarding.
**Not urgent, not blocking.** ssh and dotfiles work today because HAL's generators still run as
the substrate. This becomes load-bearing in the node-by-node retirement phase, not before — which
is the right time to build it, once the account model is decided here.
**Not urgent, not blocking.** ssh and dotfiles work today because HAL's generators still run as the
substrate. This becomes load-bearing in the node-by-node retirement phase, not before — which is the
right time to build it, once the account and CA model are decided here.
## References
- The gap was found generating `~/.ssh/config` from the *HAL* registry (`hal/terminal`'s
postConfigure hook), which the nox mesh has no equivalent for.
- [ADR 0128](../../02-DECISIONS/0120-a-roster-fact-carries-its-format-as-a-template.md) — the roster
fact mechanism that renders the ssh files, format owned by the module.
- [ADR 0112](../../02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md) — the
system-path placement this mirrors for home paths.
- [ADR 0051](../../02-DECISIONS/0051-shared-data-is-the-operators.md) — why the login key stays
the operator's, never minted.
- [ADR 0051](../../02-DECISIONS/0051-shared-data-is-the-operators.md) — why the operator's personal
key is signed, never minted.
- [ADR 0113](../../02-DECISIONS/0113-the-vault-makes-every-secret.md) — the CA key is a secret the
vault makes; [ADR 0114](../../02-DECISIONS/0114-a-shared-credential-rotates-over-two-credentials.md)
— short-lived certs as rotation.
- [ADR 0125](../../02-DECISIONS/0117-a-machines-uplink-is-a-seat.md),
[ADR 0126](../../02-DECISIONS/0118-undeclaring-gives-a-unit-back-the-state-it-was-found-in.md) —
the never-sever-the-channel rule and the found-vs-owned semantics, applied here to `~/.ssh`.
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---
layer: to-be
status: proposed
code: []
updated: 2026-09-27
decisions:
- 02-DECISIONS/0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md
- 02-DECISIONS/0120-a-roster-fact-carries-its-format-as-a-template.md
---
# 30 — The mesh updates itself on a push
**Today the mesh does not update itself; a person drives the pipeline by hand, and one class of
change freezes it.** A code change lands in `mesh-controller` or `mesh-catalog`, and getting it onto
the machines is a sequence somebody types. The predecessor's pipelines rebuilt and redeployed on a
push without anyone watching; the successor should too. This records the process as it is done by
hand now — so it can be read, and then coded — and the two things that make it more than "add a
webhook".
## The process, as done by hand
**An ordinary (non-breaking) change** — new module code, a bug fix, a manifest tweak that changes no
seat or schema:
1. `module moved <module> <commit>` — tell the mesh its source advanced (the controller repo has no
trigger, so this is manual; the catalogue's webhook does it automatically — see below).
2. `build --behind` (or `build <repo> [--ref] [--path <subdir>]`) — the build machine rebuilds and
records the new image.
3. The mesh **reconciles on its own**: the module's declaration now names the new image, the next
push/heartbeat sends it, and the host swaps the container. For the control plane this is a
self-upgrade — the running controller composes its own new image and the host replaces it. No
restart is typed.
**A breaking change** — a manifest schema the controller parses differently (a fact's shape, a
seat's name), where the new control plane cannot read the manifests the old one stored:
4. Land the code (controller + catalogue together — they are one change).
5. Rebuild + deploy the new controller (steps 1–3). **The moment it is live it refuses the
still-old-shape stored manifests, and composition freezes for every node that runs an affected
module.** Running services are untouched; only new declarations stop.
6. **Re-register each affected manifest under the new shape**, which the *new* controller accepts —
`module add <file> -source <repo> -ref <ref> -commit <commit>`. This writes the manifest to the
store without a build, so it is the fast way to lift the freeze. (The controller container is
distroless: `docker cp` the file to the container root `/x.json`; `/tmp` does not exist; the
root filesystem is writable. The file is lost when the container is recreated on the next image
swap, so copy it *after* the swap.)
7. `push --behind`, then verify `status` is clean and `seats` (or the relevant surface) shows the
new shape held by the right holders.
The freeze in a breaking change has been paid three times in one session (a fact-shape change, the
`/etc/hosts` region, a seat rename); each time it lasted seconds and no service dropped. It is
recoverable, but it is not something a push should trigger unwatched — which is the crux of what
automating this must solve.
## Why it is more than "add a webhook"
### 1. The trigger today is HAL's, not the mesh's
Build-on-push works for the catalogue because its repository has a Gitea webhook pointing at
`http://host.docker.internal:9877/webhook/gitea` — and **that receiver is `hal-gitea-tools.service`**
(`~/.hal/modules/hal/gitea/tools/server.js`), a *predecessor* component. The nox builder consumes
build work; it does not receive Git events. So the mesh's own build pipeline currently rides on a
HAL service, and:
- the `mesh-controller` repository was never wired to it, which is why the control plane is the one
thing that does **not** self-update — every controller deploy this session was `module moved` +
`build` by hand;
- when HAL is retired, build-on-push stops for the whole mesh.
**The mesh needs its own forge-webhook→build trigger**, a nox component (a module, and likely a
seat — `mesh-forge-trigger` or folded into the git seat's holder) that receives Git events and turns
them into build work over the broker, for **every** repository including `mesh-controller`. Replacing
`hal-gitea-tools` is the concrete first build. Its logic already exists to copy: match the pushed
repository (and changed paths, for a monorepo like the catalogue) against the build-context
repository of every registered module, and rebuild the matches.
### 2. The builder validates too — and a breaking change deadlocks it
The build machine embeds the same catalogue package the controller does, so **it validates a
manifest against its own compiled-in seat/schema set**. A breaking change therefore couples *four*
things, not two: the controller, the **builder**, every affected manifest, and every node's host.
This session's seat rename rebuilt the controller but not the builder, and the stale builder then
refused every manifest claiming a renamed seat.
Worse, one rename **deadlocked** the builder: the build machine's own seat was renamed
(`the-build-machine` → `mesh-build-machine`). To refresh the builder you must build it; to build it
the *running* (old) builder must accept the new builder's manifest — which claims the new name it
does not know. The old builder cannot build the new builder. Escapes:
- **Never rename a seat whose holder validates manifests** in an ordinary pass — the build machine's
seat belongs with the deferred delivering seats (ADR 0121). Reverting `mesh-build-machine` to
`the-build-machine` (deferred) lets the old builder build the new builder, which then knows the
new names.
- Or bootstrap a new builder image **out of band** (build locally, publish to the registry, register
the module at that digest), the way genesis loads the first builder — bypassing the old builder's
validation once.
Either way, self-update for breaking changes needs a **transition discipline** so a push does not
auto-freeze: the new control plane (and builder) should accept the *old and new* shape together for
one release — deprecated aliases in the seat set, a schema that reads both — then a later release
drops the old. With that, a breaking change rolls out on a push like any other: everything reads
both, the manifests migrate, the compatibility is removed. Without it, self-update would simply
automate the freeze.
## What to build
- **A nox forge-webhook trigger** (replaces `hal-gitea-tools`): receives Git events for every mesh
repository, dispatches build work to the builder over the broker, and records `module moved`
automatically. Wire `mesh-controller` to it so the control plane self-updates like everything else.
- **A transition discipline for breaking changes**: the control plane and builder accept old+new for
one release; the tooling that lands a schema/seat change emits the compatibility shim and the
follow-up that removes it. This is what makes step 4–7 above safe to trigger unwatched.
- **Config/package modules need no builder** — `module add` registers their manifest directly
(this is how the uplink managers and the re-registrations above were done). Only image-bearing
modules need the build machine, which narrows what the deadlock above can block.
## Why now, and why not yet
**Why it matters:** self-update is the difference between a mesh a person maintains by typing
pipeline steps and one that maintains itself, and it is a stated goal (parity with the predecessor's
pipelines). The HAL trigger dependency also makes it a retirement blocker: build-on-push dies with
HAL.
**Why not reflexively:** the trigger is a new component with the broker and forge in its blast
radius, and the transition discipline changes how every breaking change is written. Both should be
designed, not bolted on beside a freeze. The manual process above is the interim, and it works.
## References
- [ADR 0121](../../02-DECISIONS/0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md)
— the seat rename whose migration and builder deadlock this record is drawn from
- [ADR 0128](../../02-DECISIONS/0120-a-roster-fact-carries-its-format-as-a-template.md) — the
fact-shape change that first showed the breaking-change freeze
- `hal-gitea-tools.service` (`~/.hal/modules/hal/gitea/tools/server.js`) — the predecessor webhook
receiver on `:9877` the mesh currently rides on
- mesh-controller `cmd/mesh-builder` (the build machine), `internal/catalogue` (the seat/schema
validation the builder shares with the controller)
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---
layer: to-be
status: proposed
code: []
updated: 2026-09-27
decisions:
- 02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md
---
# 31 — A module declares its fail2ban jail, and the mesh composes them per node
**A node's intrusion filter should be composed from the modules it runs, the same way its firewall
is.** The mesh already derives a node's nftables ruleset from every assigned module's `listens` and
`guards` (the `Filtering` mechanism). fail2ban is the same shape and is not modelled: a module that
runs an authenticating service — postgres, mssql, mailu — has a jail (a filter that reads its log
and a jail stanza that bans on it), and which jails a node's fail2ban runs should be exactly the
jails of the modules assigned to that node.
The predecessor did this with per-module files: `postgres` shipped `postgres-auth.conf`, `mssql`
shipped `mssql-auth.conf`, `mailu` shipped `mailu.conf`, and the node's fail2ban read whichever were
present. When HAL retired on novox those became dangling symlinks — fail2ban ran the jails only from
memory, and a restart would have dropped them. The base was salvaged (the fail2ban module now ships
`sshd`, `recidive`, and the `ignoreip` that spares the mesh's own range), but the **service jails
are gone**, because no nox module declares one yet.
## The shape
- **A module declares its jail in its manifest**, naming no node and no path (ADR 0112): the filter
(the failregex, or a stock filter it uses) and the jail stanza (port, logpath, maxretry, bantime).
The `postgres` module says what a postgres brute-force looks like and how to ban it; it does not
say on which machine, because it does not know.
- **The mesh composes them per node.** For each node, the jails of its assigned modules are gathered
and written into the fail2ban holder's `jail.d/` (and filters into `filter.d/`), exactly as
`listens`/`guards` are gathered into the node's firewall. So a node running postgres gets the
postgres jail; a node not running it does not. The `node-intrusion-prevention` holder receives
them the way a provider receives its consumers' contributions.
- **The base stays the fail2ban module's**: `sshd`, `recidive`, and the `ignoreip` naming
`${machine:mesh-range}` so a tunnel peer is never banned.
## Why this, and not the module writing the file itself
A module could declare a `file` resource at `/etc/fail2ban/jail.d/<x>.conf` directly. Rejected: the
path is the fail2ban holder's to own (one module owns `jail.d`, as one module owns the firewall
table), the jail's logpath and defaults want the mesh's composition (the `ignoreip`, the ban action
the node uses), and two modules writing into one directory is the collision the seat/holder model
exists to prevent. The module declares *what its jail is*; the holder's composition decides *how it
lands* — the same split as `listens` (the module says the port; the mesh says the rule).
## Why now
fail2ban on novox currently runs the service jails from memory only; the next restart drops them
(the `ignoreip` is safe on disk, so the mesh-partition risk is closed, but postgres/mssql/mailu
auth-banning would be lost). This is the mechanism that restores them properly, and it is needed as
each of those modules migrates to the other nodes — ace running postgres should get the postgres
jail, composed from the postgres module's manifest, without anyone editing a node.
## References
- [ADR 0112](../../02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md) — a module
names no node or path; its jail is declared the same way its `listens` are
- mesh-controller `internal/catalogue/adoption.go` (`Filtering` — the firewall composition this
mirrors), `internal/catalogue/manifest.go` (`Listens`/`Guards`, the fields a jail field sits
beside)
- mesh-catalog `modules/fail2ban` (the base: sshd, recidive, ignoreip); the service modules
(`postgres`, `mssql`, `mailu`) that will declare jails
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---
layer: to-be
status: proposed
code: []
updated: 2026-09-27
decisions:
- 02-DECISIONS/0126-a-module-declares-its-own-seats.md
- 02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md
- 02-DECISIONS/0128-the-mesh-bus-is-required-not-ambient.md
- 02-DECISIONS/0106-the-bus-is-nats.md
- 02-DECISIONS/0041-events-are-a-relationship.md
- 02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md
- 02-DECISIONS/0083-one-push-leaves-the-mesh-consistent.md
- 02-DECISIONS/0129-a-seat-carries-the-protocol-of-its-role.md
---
# 32. What a module declares, and what the bus makes of it
**A module that speaks to the mesh requires the bus, and receives what it needs to connect**
([ADR 0128](../../02-DECISIONS/0128-the-mesh-bus-is-required-not-ambient.md)). What a module
declares are *relationships*; subjects, streams, consumers and permissions are all derived from
those, and a manifest never contains one.
> **Revised 2026-09-26.** This document opened by calling the bus *ambient* — "no module requires
> it, the way no module requires a filesystem". Two counts say otherwise: of 72 modules in the
> catalogue, **49 take a broker credential and 23 do not**, so an ambient connection would mint an
> account for a third of the catalogue that never speaks; and the 49 each hand-write the path it
> lands at, which is provisioning done badly by hand. The bus is required, and a module that does
> not require it has no account at all.
**The requirement delivers the connection; the declarations shape the authority.** `requires:
mesh-bus` says *this module talks to the mesh* and grants no subject by itself. `emits`,
`consumes`, `tools`, `uses` and a declared seat say what it may say and hear. Declaring a subject
without requiring the bus is incoherent and refused at registration.
This document is the declaration model. [Design 25](25-the-bus-on-nats.md) is the bus itself —
subjects, streams, accounts, enrolment — and stays the authority on the wire.
[Design 19](19-the-module-protocol.md) is the specification an SDK implements, and is rewritten
onto this in step 3 of [ADR 0116](../../02-DECISIONS/0116-the-bus-is-built-in-five-steps.md).
## 1. A module names locally; the mesh derives the subject
This is the load-bearing rule.
[ADR 0112](../../02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md) says a module
definition names no node, mesh or path. A transport address is the same class of thing: if
manifests held literal subjects, reorganising the subject space would mean editing every module in
the catalogue, and the mesh would have hundreds of copies of a decision it made once.
| declared | derived |
|---|---|
| `emits: order.placed` | publish on `mesh.mod.<module>.event.order.placed` |
| `consumes: billing.order.placed` | durable consumer on `mesh.mod.billing.event.order.placed` |
| `tools: status` | queue-group subscription on `mesh.mod.<module>.tool.status` |
| seat `telegram-sender`, `accepts: send` | work-queue consumer on `mesh.seat.telegram-sender.accept.send` |
| `uses: telegram-sender` | publish on that seat's `accept` subjects, and nothing else |
**Wildcards, and they are the mesh's rather than a bus's.** *Added 2026-09-27, from
[issue 127](../../04-ISSUES/127-a-module-event-derives-a-subject-nothing-publishes/00-report.md).* A
consumer may write `*` for one name and `**` for the rest: `*.download.completed` is that event from
any module, and `**` on its own is every event in the mesh, which an audit logger wants and says in
one token. Spelled this way rather than the wire's, for the reason everything else here is local —
the bus the mesh runs on today spells these `*` and `#`, the one being built spells them `*` and
`>`, and a manifest naming either would stop being true when the wire changed. An emitted event
carries no wildcard: it names one event.
**A module publishes under its own name, and an event about a role belongs to the seat.** *Added
2026-09-27, same source.* The bus enforces that a namespace belongs to the module it is named for, so
an event named for somebody else cannot be published at all. Where the event is really about a role —
"the artifact store accepted an image" — the seat is the right home, because that name outlives
whoever fills it, and a consumer written against the holder's own name breaks when the holder
changes. **Not yet possible in practice**: seats carry protocol in the manifest and in the permission
model, and the shared library has no way for a module to publish on one. Until it does, such an event
lives under the emitting module's own name and the consumer carries that coupling.
**How the rule is checked, because it was not.** *Added 2026-09-27, same source.* Two checks, because
the mistake happens at two scales. Per manifest, at registration: an event is a local name, and the
old bus's form is refused with the name to write instead. Across the whole catalogue, as a test:
where a consumed event's emitter is present, it must emit that event. The second cannot demand a live
emitter for everything — a module lives in its own repository and may be installed long before the
one whose events it wants — so it says nothing about an absent emitter and everything about a present
one. **A subscription that matches nothing is not an error, it is silence**, which is why nothing
reported thirty-seven manifests being wrong the same way.
**It is `tools:`, not `serves:`.** Revision, found while implementing: the manifest already uses
`serves` for the facts a consumer needs in order to reach a provision, and two meanings under one
key in the file a module author reads most is a footgun. Worth noting that until now a module's
tools were not declared at all — they were known only at runtime, from an environment variable in
its image — so declaring them is new, and is what lets the mesh check that a module claiming a
seat answers what that seat's protocol promises.
**The `event` / `tool` / `accept` token is load-bearing, not decoration.** Revision, found while
defining the streams: a stream is defined by a subject filter, so a namespace holding both a
module's events and its tool calls cannot be filtered into an events stream without capturing
every tool invocation in the mesh — and a tool call must never be persisted
([design 25](25-the-bus-on-nats.md) §3 keeps tools on core NATS, where a lost call is a timeout the
caller already handles). The kind token is what makes `mesh.mod.*.event.>` a safe filter. The
first draft of this table had no token, which reads better and cannot be implemented.
**The test this must pass: the manifest survives the wire changing.** Reorganise the subject space
and every manifest in the catalogue is still correct. That is the property
[ADR 0039](../../02-DECISIONS/0039-what-the-sdk-holds-and-refuses.md) gave the sdk, applied to
declarations.
**A handler names an event the way its manifest does.** *Added 2026-09-27, found while fixing issue
127.* The runtime handed a handler the event name alone, so a manifest declaring
`consumes: builder.built` produced a pattern that could never match the key it was compared against,
and a module consuming one event from two emitters could tell them apart only by reading a header.
The subject already carries the emitter, so the key a module sees names it too — which makes a
disagreement between a manifest and the code a typo rather than a category error.
## 2. Three namespaces, and nothing else
**Its own** — `mesh.mod.<module>.>`. Its events and its tools. Nothing else may publish into it,
so an event's source is a fact the bus enforces rather than a claim in the body.
**Seats it holds** — `mesh.seat.<seat>.>`. Full participation: consume what the seat accepts,
publish what it emits, serve what it serves.
**Seats it uses** — publish only, and only on the `accepts` half. A sender cannot subscribe to a
seat's inbound subject and watch other modules' traffic, and cannot publish the seat's outbound
events and lie about outcomes.
A module naming anything outside these three is refused at registration. The whole permission set
is derivable from the declaration; nobody writes an access rule.
## 3. Queues are derived, never declared
A module says what it reacts to, not how delivery works. Each `consumes` becomes one durable
consumer; a seat's `accepts` becomes one work-queue consumer with a queue group named for the
seat. The module does not name them, does not know their names, and cannot misconfigure them —
and the controller stays the only writer of stream and consumer definitions
([design 25](25-the-bus-on-nats.md) §3).
**The mesh's own seats carry protocol too.** *Added 2026-09-27,
[ADR 0129](../../02-DECISIONS/0129-a-seat-carries-the-protocol-of-its-role.md).* A seat declared by a
module says what it accepts, emits and serves; the `mesh-*` set said only who does a job. So the mesh
had roles it could not describe — a build machine with three audiences for one outcome and no way to
derive a grant for any of them, and an event genuinely about a role with nowhere to live but the
namespace of whichever module happens to hold it. The mesh's seats now take the same three fields, and
the same machinery derives the holder's authority, its work queue and its consumers.
**So a build is work submitted to a role, like any other.** The build machine seat accepts a build and
emits an outcome, and the dedicated branch that carried builds retires: a work queue shared by several
machines is exactly what `accepts` already is, and a second mechanism for it is two places a permission
can be wrong.
**And one publish reaches three audiences without anybody's inbox being opened.** A build's outcome is
the seat's own event: whoever asked matches it by the id their request carried, the controller records
it, the catalogue places it in the graph. That is the fan-out a shared exchange gave for free, written
as a subject the mesh derived instead of a topology somebody configured — and it is why a holder needs
no permission to publish into an asker's inbox, which is the one grant design 25 §4 refuses by name.
**Retention belongs to whoever owns the namespace, not to a consumer.** A seat declares how long
its inbound backlog survives, because that is a property of the service:
```
seat: telegram-sender
scope: mesh
accepts: send retain 7d
emits: delivered, failed
serves: status
```
If each consumer could tune it, the mesh's durability would be an emergent property of whichever
manifest was edited last.
**Why a module's own events do not carry their own retention, though the same rule would allow
it.** A seat owns its namespace and gets a stream of its own, so it can say. A module's events
share one `EVENTS` stream, and three facts about JetStream decide that they must:
- **Storage is not a property of a subject.** A subject is only an address; a *stream* is a
separate object that captures subjects matching a filter. So "this topic is durable" is always
really "some stream covers it", and something has to create that stream.
- **Overlapping streams are refused, not merged.** Verified against the server: a per-module
stream beside a shared `mesh.mod.*.event.>` is rejected with *subjects overlap with an existing
stream*. So "one stream by default, its own for a module that wants different retention" is not
available — it is all of one or all of the other, and a filter cannot express an exception
either.
- **A stream per module breaks cross-module consumption.** An audit logger consuming every
module's events is one consumer on one stream today; with a stream each it becomes one consumer
per module, created and destroyed as modules come and go.
So: one stream, and **per-subject caps** for the fairness that actually matters — a noisy emitter
cannot evict a quiet one, which is verified (a cap of three, ten messages on one subject and one
on another, leaves four). What is genuinely unavailable is a different *age* per module, because
JetStream ages per stream and not per subject. A module that truly needs its own retention has a
way to say so: declare a seat, which owns its namespace and gets its own stream.
**Scope gives per-node workers without a new concept.** A module running on three nodes that each
need their own queue declares a node-scoped seat: one holder per node, three queues, same
machinery. Mesh-scoped and node-scoped seats already exist; here they do the work of "one shared
service" versus "one worker per machine".
## 4. Five relationships
| | provision | event | job | state | tool |
|---|---|---|---|---|---|
| shape | 1:1 resource | 1:many | N:1 | 1:1 | 1:1 |
| addressed to | a provider | the emitter's own namespace | a **seat** | one node | a module or seat |
| who must act | the provider | nobody | exactly one holder | that node | the server |
| credential | sealed, per consumer | none | none | none | none |
| reply | — | none | none, or an event later | a report | awaited |
| retention | — | age and size | work queue, explicit ack | **last per subject** | none |
| declared | `provides`/`requires` | `emits`/`consumes` | seat `accepts` / `uses` | the mesh's own | `serves` |
**Job** is the one [ADR 0041](../../02-DECISIONS/0041-events-are-a-relationship.md) had no room
for. Its table has events at 1:many and provisions at 1:1; a module submitting work to a service
is neither. It is not an event, because an event is a broadcast nobody is obliged to act on and a
second holder would do the work twice. It is not a provision, because there is no resource and no
credential. What makes it safe is not cleverness in the subscribe call but the seat: exactly one
holder, so exactly one worker, by construction.
**State** is the shape the deploy path needs and nothing else uses. A declaration is not an event
— replaying yesterday's is actively harmful — and not a job. Only the newest matters, which is
last-per-subject retention, and a node that has seen sequence *n* refuses *n−1* by construction.
That is the wire-level answer to
[issue 107](../../04-ISSUES/107-a-declaration-carries-no-order/00-report.md).
## 5. Seats
A module declares a seat with its protocol, and the mesh enforces one holder at its scope
([ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md)). A caller declares that
it uses the *seat*, never the module, so the implementation can be replaced under it.
- The set of seats is **derived** — the mesh's own, plus every registered module's — so it is both
closed and extensible, and enumerating it is a query rather than an inventory.
- `mesh-*` is **reserved**: the prefix is the reservation rule, and a module declaring one is
refused at registration.
- Two modules declaring the same name: the second is refused.
- A module may not claim a seat whose protocol it does not implement.
- **Nobody holding a seat is not an error.** The stream exists from registration, so work queues
until a holder appears. Install the telegram module a week later and the backlog flushes.
## 6. The lifecycle: build, publish, deploy
Every shape above appears once, in order, and no step knows where the next one runs.
**A change lands.** The module holding `mesh-git` emits `pushed` — repository, ref, commit. An
event, because it is a fact about git and git's identity is the meaning.
**The change becomes work.** The controller consumes `pushed`, asks the catalogue which modules
are built from that repository and path
([ADR 0069](../../02-DECISIONS/0069-a-module-is-a-repository-and-a-path.md)), and submits one
**job** per affected module to the `mesh-build-machine` seat. The builder stays simple: it builds
what it is handed, and never resolves anything. A builder that dies mid-build has its job
redelivered, because a work queue with explicit ack is what that means.
**The artifact is published.** The builder pushes to the registry seats and emits `built` —
module, version, digest. An event again: a fact about the builder.
**The build cascade is that event fanning out through a graph the mesh already has.** A module
whose image is built *on* another's artifact declares that in `build.on`. So `built` reaches the
controller, which walks the declared graph and submits rebuild jobs for everything downstream. A
dependency cascade is not special machinery — it is one event, one derived graph, and the same job
queue.
**Deployment is state, not a message.** The controller composes each affected node's declaration
and publishes it last-per-subject. A node that was away gets exactly the current one, never a
queue of superseded ones, and a replayed older one is refused by sequence.
**Applying is reported to a role.** The host applies and reports to the `mesh-controller` seat —
not to an address it was given at genesis. Held and retried while the store restarts
([ADR 0083](../../02-DECISIONS/0083-one-push-leaves-the-mesh-consistent.md)).
What disappears across that chain is every address. No webhook URL, no registered callback, no
"which node is the builder on", no controller endpoint baked into a joining node. That is the
class of bug
[issue 102](../../04-ISSUES/102-an-address-recorded-at-genesis-or-build-does-not-follow-the-nodes-ports/00-report.md)
names, dissolved rather than fixed.
## 7. Modules depending on each other
Three kinds, and conflating them is how deployment ordering goes wrong.
**Build-time** — A's image is built on B's artifact. Resolved by the cascade above; nothing at
runtime cares.
**Provision** — A requires a database from B. A **hard** dependency: the credential must exist
before A can start, so resolution gates delivery and A is shown as waiting until B has answered
([design 27](27-a-module-requires-the-mesh-resolves.md)).
**Seat** — A uses B's seat. A **soft** dependency, and this is the one the bus changes. A starts
whether or not anyone holds the seat, because the stream absorbs the gap. Deployment order stops
mattering for everything expressed this way, and a service being restarted, moved or upgraded is
not an outage for its callers — it is latency.
That difference is worth choosing on purpose. A dependency expressed as a provision must be
ordered; the same dependency expressed as a seat need not be.
## 8. Versioning a protocol
A seat's protocol is a compatibility surface between modules that do not know each other and are
deployed at different times. Four ways it can change, and they are not equally dangerous:
| change | example | detectable |
|---|---|---|
| **additive** | a new `accepts` subject, a new optional field | nothing breaks |
| **removal or rename** | `send` becomes `deliver` | yes, mechanically |
| **shape** | an optional field becomes required | yes, if shapes are specified |
| **semantic** | `send` starts meaning *queue for tomorrow* | **no** |
**Additive is free.** A seat may grow without a version, without re-registering a caller, and
without ceremony. Most change is this.
**A breaking change is refused while anyone is bound.** Registration computes a compatibility
fingerprint over the seat's protocol — its subjects and the shapes they carry. A registration that
alters the fingerprint while callers are bound is refused, **and the refusal names them**. The
mesh already holds the `uses` graph, so this is derived rather than declared, and it turns a
runtime breakage into a registration-time conversation.
**When a break is genuinely needed, the version goes in the subject, not the name.** The seat stays
one thing; `mesh.seat.<seat>.v2.<verb>` runs beside v1 and the holder serves both. A caller moves
when it is ready. Versioning the *seat name* was considered and rejected: it forks the role, so
"one holder" stops meaning one provider of the capability, and every document naming the seat has
to be found and changed.
**Binding is recorded, not inferred.** A caller declares `uses: telegram-sender` with no version,
and resolution binds it to the current one and records that — the same **pin** machinery
[design 27](27-a-module-requires-the-mesh-resolves.md) already uses when resolution had a choice
to make. Moving to v2 is a deliberate re-pin, so nothing drifts onto a new protocol because it
happened to be newest.
**Retirement is reported, never automatic.** When the `uses` graph shows nothing bound to v1, the
overview says it is retirable. The mesh does not remove it.
**And none of this catches a semantic change.** Same subject, same shape, new meaning: no
fingerprint sees it, and no check proposed here would. The defences are review, and pushing
meaning into shape wherever it can go — a required `channel` field is caught, a changed
interpretation of an existing one is not. Saying so is better than implying the fingerprint is
complete, because a team that believes it is complete stops reviewing for the case it misses.
## 9. Provisioning over the bus
Provisioning rides the bus, and the provider stops having an address.
| part of a provision | shape |
|---|---|
| the requirement resolving to a provider | the controller's, not the bus's |
| the grant reaching the provisioner | request/reply to a **role** |
| `holds` — the reconcile question, every minute | the same call, on a timer |
| `provisioned` / `deprovisioned` | events |
| the credential reaching the consumer | §10 — fetched, never carried |
A provisioner's interface is already three calls — create, remove, holds — which is exactly a
`serves` protocol. So **a provision interface is a seat whose protocol is those three**, which is
why [design 26](26-the-seats.md) already allows a seat to deliver a provision. The two concepts
were converging before this document; here they meet.
What stays different, and must not be unified away: a provision has a **per-consumer resource and
a sealed credential**, created and destroyed per consumer. A seat protocol has neither — it is a
role you send to. Collapsing them would mean pretending a database is a subject.
### `mesh-bus` and `nats` are two interfaces, never one name
The mesh's own bus is **`mesh-bus`**, delivered by the `mesh-broker` seat and answered by the
controller — because the bus's accounts are configuration rather than something a provisioner
creates, so there is no provisioner process in the path and nothing waiting on a bus account in
order to make bus accounts. A module that runs a NATS server of its own and offers it as a
backing service provides **`nats`**, exactly as the deprecated broker provides `amqp`
([ADR 0127](../../02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md): AMQP is not a provision, and everything speaks to the `mesh-broker` seat)).
They are never the same name. A manifest saying `nats` could otherwise mean either the mesh's
nervous system or a private queue, and the difference between those is the whole architecture.
0119's rule decides which is legitimate: a private bus is a backing service, never a channel to
another module.
### Where addresses survive
"Where is it?" is two different problems, and the bus solves one of them completely and the other
not at all. Keeping them apart matters, because a reader who thinks the mesh no longer has
addresses will believe a class of bug is fixed when it is untouched.
**Something that is on the bus: the address disappears.** A host reporting in used to need the
controller's address — recorded somewhere, at some moment, and wrong as soon as anything moved.
Now it publishes to `mesh.seat.mesh-controller.report` and the bus routes it to whoever holds the
seat. Nothing anywhere records where the controller is, so nothing can record it *wrongly*. The
same is true of the builder, the catalogue, the telegram sender. This class is not mitigated; it
is gone, because the information is no longer stored.
**Something that is not on the bus: the address stays, exactly as before.** A module that requires
a database does not reach postgres over NATS — it opens a postgres connection, because postgres
speaks postgres and is not listening on any subject. Its credential contains a host and a port,
and no amount of subject addressing changes that.
So the fix for that second class is unchanged and is not this document's:
[ADR 0098](../../02-DECISIONS/0098-a-fact-a-provider-makes-at-first-start-is-fetched-from-it.md) —
fetch the fact where it is used rather than storing a copy — which is what
[issue 102](../../04-ISSUES/102-an-address-recorded-at-genesis-or-build-does-not-follow-the-nodes-ports/00-report.md)
is actually about. The bus makes that class *smaller* by removing every mesh-internal address from
it. It does not make it empty.
**And one address is irreducible: the bus's own.** A node has to know where the broker is before
it can use subjects for anything, so that one cannot be a subject. It is the addressing equivalent
of §10's bootstrap — the first thing cannot be found by the mechanism that finds everything else.
## 10. Secrets, and why they never enter a stream
Everything the vault does is request/reply to the `mesh-vault` role: mint, fetch, rotate. In that
sense it is as much on the bus as anything else.
**The bus is not trusted with a secret, and does not need to be.** A secret is sealed to its
recipient, so what crosses the bus is ciphertext only that recipient can open. The broker sees
that a secret moved, and to whom — metadata, which is acceptable — and never a plaintext.
**But sealed is not enough on its own, because a stream persists.** A sealed secret written into
a JetStream stream is a durable ciphertext sitting in the mesh's own storage, and the day a
sealing key leaks, that stream is an archive rather than a moment. So:
- **A secret travels on core request/reply, never through a stream.** No persistence, no replay,
nothing to exfiltrate later.
- **A declaration names a secret; it does not carry one.** Declarations are the state shape, which
*is* a stream — so the host fetches the secret from the vault at apply time, over the core path.
That is [ADR 0098](../../02-DECISIONS/0098-a-fact-a-provider-makes-at-first-start-is-fetched-from-it.md)'s
existing discipline — *fetched from it, not carried* — applied to the one payload where carrying
it is worst.
**The bootstrap, which is circular and has a precedent.** The vault makes every secret
([ADR 0113](../../02-DECISIONS/0113-the-vault-makes-every-secret.md)), including the bus's own
passwords. The vault is a module, and a module needs a bus account, whose password the vault
makes. Nothing can go first.
This is the shape [ADR 0067](../../02-DECISIONS/0067-genesis-is-a-pivot.md) already resolves for
the control plane: **genesis is a pivot.** The controller mints the handful of foundation
credentials itself, raises the store, the broker and the vault, and then the vault takes over and
mints everything from there — the same move as raising a temporary control plane and reinstalling
it as an ordinary module once the registry exists.
So there are exactly two things the normal path cannot make, both at genesis, both ending the
moment the mesh can mint for itself: **the bus's own accounts** (§the bootstrap argument in
[ADR 0127](../../02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md) (superseded by [ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md): AMQP is not a provision, and everything speaks to the `mesh-broker` seat) (superseding [ADR 0125](../../02-DECISIONS/0125-the-bus-is-the-only-broker.md)) — a provisioner is a module and
needs an account before it can run) and **the vault's own credential**. Any third exception is a
design failure, and naming these two is what makes a third one visible.
## 11. Open
**Semantic change has no mechanical defence** (§8). Recorded as open rather than solved, because
it is the residue of a question the rest of §8 answers and the part a fingerprint cannot reach.
**Whether a module may declare a seat it does not itself claim** — the contract as one thing, the
implementation as another, which is how two competing implementations would ever exist.
**Whether `consumes` naming another module couples too tightly.** It is kept here deliberately —
an event's provenance is its meaning — but a consumer of `billing.order.placed` does depend on
billing existing under that name.
## 12. How it is checked
- **A manifest holds no subject.** A catalogue test: no manifest contains a string matching the
subject grammar. The rule is worthless if it is followed by convention.
- **Permissions are exactly the three namespaces.** A composition test per module: the derived
permission set equals what its declaration implies, and a hand-written addition to it fails.
- **A sender cannot read the queue it writes to.** A bed: a module declaring `uses` is refused
subscribe on that seat's inbound subject.
- **One holder, one delivery.** A bed: a seat's job delivered once with the holder running, and
a second claim of the seat refused.
- **A queued job survives no holder.** A bed: submit with the seat unheld, assign the holder,
the job is delivered.
- **The cascade rebuilds exactly the dependents.** A bed: publish an artifact two modules build
on, and exactly those two are rebuilt.
- **A stale declaration is refused.** A bed: replay sequence *n−1* after *n*, and the node refuses
it rather than applying it.
03-DESIGN/01-to-be/README.md
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| [`23-choosing-a-provider.md`](23-choosing-a-provider.md) | Which of several providers of a kind serves a consumer, and when a module carries its own instead | [ADR 0084](../../02-DECISIONS/0084-which-provider-serves-a-consumer.md), [ADR 0027](../../02-DECISIONS/0027-a-provision-names-what-the-consumer-is-coupled-to.md) |
| [`24-the-secrets-vault.md`](24-the-secrets-vault.md) | The module that owns a secret — a `secret` provision, and the boundary of what it owns | [ADR 0085](../../02-DECISIONS/0085-a-secret-is-a-provision.md), [ADR 0031](../../02-DECISIONS/0031-the-control-plane-authenticates-nobody.md), [ADR 0048](../../02-DECISIONS/0048-a-provider-creates-the-credential-the-mesh-minted.md) |
| [`25-the-bus-on-nats.md`](25-the-bus-on-nats.md) | **Proposed.** The architecture of the mesh's bus on NATS: what rides which subject under which guarantee and whose account, how a node joins, how a person reaches a tool, and how the mesh moves from the bus it has | [ADR 0106](../../02-DECISIONS/0106-the-bus-is-nats.md), [ADR 0116](../../02-DECISIONS/0116-the-bus-is-built-in-five-steps.md), [ADR 0043](../../02-DECISIONS/0043-a-module-broker-account-is-scoped-by-emits-and-consumes.md), [ADR 0083](../../02-DECISIONS/0083-one-push-leaves-the-mesh-consistent.md) |
| [`26-the-seats.md`](26-the-seats.md) | **Proposed.** What a mesh can have one of, who fills each, and a seat's holder answering for the provision it delivers — including the `git` seat a build's source can live on | [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md), [ADR 0111](../../02-DECISIONS/0111-a-build-source-is-on-the-git-seat-or-external.md), [ADR 0109](../../02-DECISIONS/0109-a-package-registry-seat-is-one-per-ecosystem.md) |
| [`27-a-module-requires-the-mesh-resolves.md`](27-a-module-requires-the-mesh-resolves.md) | **Proposed.** One concept for everything a module needs: a requirement with a contract, answered by one of four kinds of provider, resolved at assignment or refused. Retires settings, placeholders, facts and paths in definitions | [ADR 0112](../../02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md), [ADR 0113](../../02-DECISIONS/0113-the-vault-makes-every-secret.md), [ADR 0114](../../02-DECISIONS/0114-a-shared-credential-rotates-over-two-credentials.md), [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md) |
| [`26-the-seats.md`](26-the-seats.md) | **Proposed.** What a mesh can have one of, who fills each, and a seat's holder answering for the provision it delivers — including the `git` seat a build's source can live on | [ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md) (superseding [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)), [ADR 0111](../../02-DECISIONS/0111-a-build-source-is-on-the-git-seat-or-external.md), [ADR 0109](../../02-DECISIONS/0109-a-package-registry-seat-is-one-per-ecosystem.md) |
| [`27-a-module-requires-the-mesh-resolves.md`](27-a-module-requires-the-mesh-resolves.md) | **Proposed.** One concept for everything a module needs: a requirement with a contract, answered by one of four kinds of provider, resolved at assignment or refused. Retires settings, placeholders, facts and paths in definitions | [ADR 0112](../../02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md), [ADR 0113](../../02-DECISIONS/0113-the-vault-makes-every-secret.md), [ADR 0114](../../02-DECISIONS/0114-a-shared-credential-rotates-over-two-credentials.md), [ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md) (superseding [ADR 0110](../../02-DECISIONS/0110-a-seat-is-a-module-assignment-from-a-closed-set.md)) |
| [`28-building-the-bus.md`](28-building-the-bus.md) | **Proposed.** The five steps of the bus work in the order their dependencies allow, each ending at a bed — with the surface measured, so no step's size is a guess | [ADR 0116](../../02-DECISIONS/0116-the-bus-is-built-in-five-steps.md), [ADR 0106](../../02-DECISIONS/0106-the-bus-is-nats.md), [ADR 0074](../../02-DECISIONS/0074-the-wire-is-specified-not-the-types.md) |
| [`29-a-node-has-operator-accounts.md`](29-a-node-has-operator-accounts.md) | **Proposed.** The mesh models machines but not the humans on them: a node gains operator accounts, and a resource may live under a home owned by its account — what would own ~/.ssh, dotfiles and ~/.config when HAL retires | [ADR 0112](../../02-DECISIONS/0112-a-module-definition-names-no-node-mesh-or-path.md), [ADR 0051](../../02-DECISIONS/0051-shared-data-is-the-operators.md) |
| [`32-what-a-module-declares.md`](32-what-a-module-declares.md) | **Proposed.** What a module declares and what the bus derives from it: three namespaces, subjects from local names, queues never declared, the five relationships, and the build-publish-deploy lifecycle on one bus | [ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md), [ADR 0127](../../02-DECISIONS/0127-amqp-is-a-provision-not-the-bus.md), superseded by [ADR 0131](../../02-DECISIONS/0131-everything-on-the-mesh-speaks-to-the-broker-seat.md) (superseding [ADR 0125](../../02-DECISIONS/0125-the-bus-is-the-only-broker.md)), [ADR 0041](../../02-DECISIONS/0041-events-are-a-relationship.md) |
## Not yet written
- **The remaining six contexts.**
04-ISSUES/112-adopting-a-tunnel-gives-the-mesh-addresses-without-names/00-report.md
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---
status: fixed
status: resolved
opened: 2026-09-24
located-in: [mesh-controller internal/inventory, mesh-controller internal/catalogue, mesh-controller cmd/mesh-controller, mesh-catalog modules/dnsmasq]
fixed-by: [mesh-controller#73 overlay-name + namesInTheMesh, mesh-catalog#106 dnsmasq daemon.json merge]
04-ISSUES/127-a-module-event-derives-a-subject-nothing-publishes/00-report.md
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---
status: resolved
opened: 2026-09-27
located-in: [mesh-catalog modules, mesh-control internal/catalogue, mesh-tools src]
fixed-by: mesh-catalog 7b06a7a, mesh-tools fbeb373, mesh-control 05ff606
amended-design: 03-DESIGN/01-to-be/32-what-a-module-declares.md
---
# 127 — A module's event derives a subject nothing publishes
## What was observed
[Design 29](../../03-DESIGN/01-to-be/32-what-a-module-declares.md) §1 says a module names an event
locally and the mesh derives the subject: `emits: order.placed` becomes
`mesh.mod.<module>.event.order.placed`, and a consumer declaring `consumes: shop.order.placed`
subscribes the emitter's own subject. That derivation is built and tested.
**Every event name in the catalogue is still written the way a routing key on the bus the mesh has
is written** — `module.<module>.<verb>` — and the derivation reads it as `<emitter>.<event>`. Asked
of the composer directly, with the module names and declarations the catalogue holds today:
| declared | derived |
|---|---|
| `builder` emits `module.builder.built` | publish `mesh.mod.builder.event.module.builder.built` |
| the catalogue consumes `module.builder.built` | subscribe `mesh.mod.module.event.builder.built` |
| a media module emits `module.<itself>.download.completed` | publish `mesh.mod.<itself>.event.module.<itself>.download.completed` |
| a player consumes `module.*.download.completed` | subscribe `mesh.mod.module.event.*.download.completed` |
The consumer's subject names a module called `module`. **No cross-module subscription in the
catalogue matches what any emitter publishes.** Thirty-seven manifests declare events; every one of
their consume declarations derives this way.
Two further consequences of the same cause, found in the same check:
- One module declares `consumes: "#"` — the wildcard of the bus the mesh has, which is not a
subject at all. The composer **refuses it outright**, so that module's account cannot be composed
and the module cannot be assigned.
- One module emits under a name that is not its own — it declares `module.<other>.image.pushed`
while being a differently named module — which the derivation puts inside *its* namespace. Whether
that is legitimate is a design question: design 32 §2 makes an event's source a fact the server
enforces, and this is a module claiming another's name in its own event.
None of it fails on the bus the mesh runs on today, where a routing key is matched literally and
nothing derives anything. It fails only once the subject is derived — which is to say it fails on
the first mesh raised on the new bus, and not before.
Evidence: run against the controller's own `PermissionsFor` on the current feature branch, with the
declarations read from the catalogue's manifests. Found while wiring the controller's consume side
(design 28 step 3.4), when the controller's own subscription had to be written and the subject it
would have to name turned out not to be the one design 32 specifies.
## Why it matters beyond this instance
**This is the failure [ADR 0074](../../02-DECISIONS/0074-the-wire-is-specified-not-the-types.md)
exists to catch, arriving by a route the conformance suite does not cover.** Two implementations
that disagree about an envelope do not fail to compile — they ignore each other while both keep
running. Here it is not two implementations disagreeing but a *declaration* and a *derivation*
disagreeing, and the symptom is identical: every service starts, every log is quiet, and nothing
reacts to anything.
The fixtures cannot catch it. They pin one emitter's envelope against one subject, and both halves
of that pair are correct. What is wrong is only visible when an emitter's derived subject is set
beside a consumer's derived subject — a check nothing performs, because until the subject was
derived there was nothing to compare.
It also means the rule 3.8 established is weaker than it reads. That task asserted **no manifest
contains a subject**, which holds: a manifest contains a local name. What nothing asserts is that a
local name derives to a subject some emitter actually publishes, and the rule as stated is satisfied
by thirty-seven manifests whose names derive to nothing.
And it blocks work already scheduled. Design 28's step 4.2 (a build source's change reaching the
builder over the bus) and 4.3 (an installation completing over the bus) are both event flows through
exactly these pairs, and the catch-up flow the controller answers is a third — the controller
currently replays a build announcement under its *own* name rather than the builder's, which a
consumer filtering the builder's subject will not hear either.
## Open questions
- Is a local name converted per manifest (`emits: built`), or does the derivation keep accepting the
old form and strip a redundant prefix? The first is thirty-seven manifests and a rule that can be
checked; the second is a rule that cannot, because `module.foo.bar` is also a legitimate three-part
local name.
- What checks the pair? An emitter's derived subject against every consumer's derived subject is a
whole-catalogue check, not a per-manifest one — and a module lives in its own repository and may
be registered long after the catalogue was checked.
- What are `#` and `*` in a consumed name? The bus the mesh has and the bus being built spell
wildcards differently, and a `consumes` pattern is the one place a module writes one.
- May a module emit an event named after another module, and if not, what does the module that does
it today declare instead?
- Who replays? A catch-up answer published by the controller under a builder's subject is the
controller signing an event as another module, which is the thing the derived namespace prevents.
If it must not, then a replay is a different message from an announcement, and the consumer needs
to be told so.
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# Diagnosis — 2026-09-27
## Where it lives
Three places, and only one of them is a bug in code.
**The manifests, in the module catalogue.** Thirty-seven declare events, and every one of them
spells an event the way a routing key on the bus the mesh runs on today is spelled —
`module.<module>.<verb>`. [Design 29](../../03-DESIGN/01-to-be/32-what-a-module-declares.md) §1 says
a module names an event **locally and bare** (`emits: order.placed`) and a consumer names
`<emitter>.<event>` (`consumes: billing.order.placed`). So the manifests are stale against a rule
that was already decided, not wrong against an undecided one. **This is the whole of the reported
symptom.**
**The manifest's own documentation, in the parser.** The comments on `emits` and `consumes` still
describe the old convention and give the old examples — "dotted topic keys, e.g.
`module.umami.site.created`", and `"#"` named as the audit logger's pattern. A module author reading
the file they read most is being told to write the thing that does not work. That is why the drift
was uniform across thirty-seven manifests rather than scattered: nobody was mistaken, everyone
followed the documentation.
**Nothing checks either one.** `ParseManifest` validates the module name, the slug, what it provides
and what it requires. It says nothing about an event name. So a local name that derives to a
namespace belonging to a module called `module` is accepted by every check the mesh has, and the
first thing that notices is a subscription that never fires.
## What was ruled out
**The derivation is not wrong.** Asked directly, with the module names and declarations the
catalogue holds, `PermissionsFor` produces exactly what design 32 §1 specifies for the input it is
given: it reads a consumer's `<emitter>.<event>` and builds the emitter's subject. Given
`module.builder.built` it reads the emitter as `module`, which is a correct reading of an incorrect
declaration.
**The conformance fixtures are not at fault and could not have caught it.** They pin one emitter's
envelope against one subject, and both halves of that pair are correct. What is wrong is only
visible when an emitter's derived subject is set beside a *consumer's* derived subject — a
comparison nothing performs, because until the subject was derived there was nothing to compare.
**Task 3.8's rule is not broken, it is weaker than it reads.** That task asserted **no manifest
contains a subject**, which holds: a manifest contains a local name. Nothing asserts that a local
name derives to a subject some emitter actually publishes.
## What is still a decision and not a conversion
Converting the manifests is implementing design 29, not deciding anything. Three of the report's
open questions are not:
- **Wildcards.** Design 29's table has no wildcard row, and two manifests need one: a module
consuming every download completion across several media modules, and an audit logger consuming
everything. The two buses spell wildcards differently, and a `consumes` pattern is the one place
a module writes one.
- **A module emitting under another module's name.** One manifest declares an event named for a
*provision* rather than for itself. Design 29 §2 makes an event's source a fact the bus enforces,
so this cannot survive as written — and the remedy is probably not a rename but a **seat**, which
is what a name stable across whoever implements it already is.
- **Who replays a build announcement.** The controller answers a catalogue's catch-up by
re-publishing builds under its *own* name, which no consumer of the builder's subject hears, and
for which it holds no grant. Publishing them under the builder's subject would be the controller
signing an event as another module — the exact thing the derived namespace prevents. So the
catch-up is either a different message or a different mechanism, and that is a decision.
## Owners
`located-in` names the manifests and the parser. The replay question reaches the controller and the
catalogue module together and is recorded above rather than in that field, because it is not where
this symptom lives.
# Fixed — 2026-09-27
Converted, and the rule now has checks. What it took was larger than the report said, in two
directions nobody had looked.
**The module code, not just the manifests.** Forty-three files pass an event name to `emit()` at
runtime, and the runtime builds the subject from what it is handed. A converted manifest with
unconverted code would have had the permission and the subject disagree — the same silence, one layer
down.
**Both clients had to learn the mapping.** Each passed the name straight through, which was right on
the bus the mesh runs on today only because modules were writing routing keys. So the old bus's client
now turns a local name into `module.<emitter>.<event>` on the way out and back on the way in.
**Without that, converting the modules would have broken the mesh that is actually running** — which
is the opposite of what fixing this was for.
**The declaration and the handler spoke different vocabularies.** The key a module's handler saw was
the event name alone, while its manifest names `<emitter>.<event>`. So a correct manifest produced a
pattern that could never match. The subject already carries the emitter; the key names it now.
## The three open questions, answered
- **Wildcards**: `*` is one name, `**` is the rest, spelled the mesh's way and derived to each bus's
own. `**` alone is every event, which is what the audit logger wanted and now says in one token.
- **A module emitting under another's name**: not allowed, and the remedy is the seat rather than a
rename — a role's name outlives whoever fills it. **Deferred in practice**: seats carry protocol in
the manifest and in the permission model, and the shared library cannot publish on one, so the
module that did this emits under its own name and its consumers carry that coupling. Worth a task
when a seat's holder needs to emit.
- **Who replays a build announcement**: still open, and narrowed. It cannot become a reply to the
catalogue's inbox: answering a module's inbox needs `_INBOX.>`, which is the blanket grant
[design 25](../../03-DESIGN/01-to-be/25-the-bus-on-nats.md) §4 refuses. So the remaining options are
a subject the controller may publish and the catalogue may subscribe, or a durable consumer that
starts at the beginning of the stream and removes the need to ask at all. Recorded on the work
breakdown as the catch-up half of task 4.5 rather than here, because it is no longer this symptom.
## What it found while running
Two dangling subscriptions that predated this and nothing had reported: a module emitting an event its
manifest never declared, which the new bus refuses outright, and a module waiting for an event nothing
emits — a demo that could never be triggered, because only that module may publish under its own name.
04-ISSUES/130-undeclaring-a-service-stops-it/00-report.md
+2 -2
View File
@@ -9,7 +9,7 @@ amended-design: 02-DECISIONS/0118-undeclaring-gives-a-unit-back-the-state-it-was
## What was observed
Reviewing the uplink modules ([ADR 0117](../../02-DECISIONS/0117-a-machines-uplink-is-a-seat.md))
Reviewing the uplink modules ([ADR 0125](../../02-DECISIONS/0117-a-machines-uplink-is-a-seat.md))
found that the host's `remove` path stops every `service` resource that is no longer declared:
`SetServiceState(..., "stopped")`, reported as "stopped; the unit file is not the host's to
delete". `store.Orphans` matches by id alone. So any of these stops the unit:
@@ -45,7 +45,7 @@ reaches it by.
## Resolution
[ADR 0118](../../02-DECISIONS/0118-undeclaring-gives-a-unit-back-the-state-it-was-found-in.md):
[ADR 0126](../../02-DECISIONS/0118-undeclaring-gives-a-unit-back-the-state-it-was-found-in.md):
undeclaring removes what the mesh made and gives back what it changed. The host records the state
it first found a unit in, and undeclaring returns the unit to it — a unit found running (the
container runtime, sshd, a network manager) is left running; one the mesh started (the packet
04-ISSUES/131-nothing-tells-the-mesh-a-source-moved/00-report.md
+107
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@@ -0,0 +1,107 @@
---
status: resolved
opened: 2026-09-27
located-in: [mesh-catalog modules/gitea, mesh-controller cmd/mesh-controller, mesh-controller internal/builder]
fixed-by: mesh-catalog #124 — the forge module watches for merged pull requests and emits `pull.merged` with the merge commit and the clone address; mesh-controller #110/#111 — the control plane follows that event on the bus, marks every module built from that repository and branch as moved, and builds them bases first, stopping when a base fails; mesh-controller #113/#114 — a build records the bases it was handed and the graph is read from builds, without which "bases first" had no edges to order by.
amended-design: 03-DESIGN/01-to-be/28-building-the-bus.md
---
# 131 — Nothing tells the mesh a source moved, and it reports itself current anyway
## What was observed
Six changes were merged to the trunk of six repositories in one sitting. The build machine built
nothing. Its last build, minutes before the first merge, was still the one it reported; no build was
requested, refused or failed, because none was ever asked for.
Asked afterwards what was wrong, the mesh said:
> 4 machine(s), all doing what they were told, all heard from, running what the mesh would send them,
> and every module current with its source
Every one of the six had moved. The last clause was false for all of them, and it is the clause a
person reads to decide whether there is anything to do.
## Why it matters beyond this instance
**The mesh learns a source moved by being told, and there is no longer anything to tell it.** The
command exists — a person names the module and the commit — and so does the question the overview
answers. What is missing is whatever used to connect the two. One repository still carries a forge
webhook aimed at a port; the rest carry none, and the port belongs to a different service than the
one the arrangement implies. So the state is not "the trigger is broken" but "there is no trigger,
and nothing says so".
**A wrong answer is worse here than no answer.** "Every module current with its source" is
indistinguishable, to a reader, from a mesh that has genuinely caught up. The overview is built to be
the thing you check instead of checking by hand, so a confident false negative removes the habit that
would otherwise have caught it. Nothing in the mesh is at fault for being out of date — it is at
fault for saying it is not.
**It is also why "current with its source" cannot be a stored fact.** The mesh compares what it built
against what it was last told the source was, and calls that agreement. Two facts agreeing tells you
nothing when both come from the same place.
## The intended shape, which is decided and not built
The forge emits what happened to it — a pull request merged — and the build machine reacts by
building what that commit affects. That keeps the forge ignorant of the build system and the build
machine ignorant of the forge's internals, which is the same argument
[ADR 0126](../../02-DECISIONS/0126-a-module-declares-its-own-seats.md) makes for addressing an event
to its emitter: the merge is a fact about the forge, and what should be rebuilt because of it is not
the forge's business to know.
The forge's module already declares the event. The build machine declares that it consumes nothing.
## What the trigger cannot be
**Not one build per changed module.** The modules form a graph: several are built from one
repository, and some are the base another is compiled on — a runtime image, a compiler base, a
repository whose context a second module builds from. Firing a build for each changed module
independently would start work that cannot succeed yet and produce a failure per dependent, for one
cause.
Observed while catching the mesh up by hand on 2026-09-27: a compiler base had to move before
anything compiled against it could build, and when it failed, the right behaviour was for its
dependents to wait rather than each fail the same way. Fifteen modules shared the cause. A trigger
that reports it fifteen times has buried it.
So whatever reacts to the forge's event resolves what changed into an order, builds the bases first,
and holds a dependent while its base is unbuilt or failed. That is a larger thing than "rebuild what
the commit touched", and knowing it now is cheaper than discovering it from fifteen identical
failures.
## Open questions
- Is "the source moved" still a thing a person can assert by hand once the event path exists, or does
the hand-operated form become the thing that made this failure possible?
- Which commit does the build machine act on — the merge, or each commit it brought — and what does
it do when several arrive for one module at once?
- How does the overview stop being able to lie? Comparing what was built against what was recorded
will always agree. Whether the trunk has moved is a question only the forge can answer, so either
the overview asks it, or it stops claiming to know.
- Does this want to be the same mechanism as the build request on the bus
([ADR 0129](../../02-DECISIONS/0129-a-seat-carries-the-protocol-of-its-role.md)), or does it sit in
front of it?
## What was done (2026-09-28)
The shape above was built as described: the forge's module emits the merge, the control plane
consumes it, and nothing on either side knows the other's internals. The build is asked for the
merge commit, not each commit the merge brought — the trunk moved once, to one place. Several merges
for one module arriving in a row are followed in turn, each moving the recorded source to its own
commit, so the last one to arrive is the one the mesh ends up built from.
The hand-operated form stays. `module moved` is how a source is recorded without a forge — a module
built from a repository elsewhere, or a mesh whose forge module is down — and it is the same act the
event performs, so the two cannot disagree about what "moved" means.
**Bases first needed edges, and there were none.** The order this report asked for was written and
walked a graph that no build had ever recorded: a recipe reads its base from a build argument, so the
digest was never in the file the builder read edges from. A build now reports what it was handed, the
control plane records it by artifact path, and the order is read from each module's newest build.
**What still can lie.** The overview compares what was built against where it was last told the
source is; the forge's event is now what moves that mark, so it is right for as long as the forge
module was listening. A merge made while that module was down is a merge the mesh does not know of
until the module next polls — it announces what merged since it last looked, so the gap closes when
it comes back, and not before. The overview does not say so.