ADR 0175: the found front end is uninstalled once a machine is converged; design 08 note

Another session's 0169 landed first. The collision check from issue 155
covered issue folders only; it covers decision records now, and would have
refused this.

00-META/checks/cycle.py

@@ -131,6 +131,22 @@ def main():
         else:
             seen[number] = name
 
+    # And decision records, which 155's fix left out: on 2026-10-02 two ADRs numbered 0169 landed
+    # on main from two sessions within the hour, and every check passed.
+    seen_records = {}
+    for path in sorted(glob.glob(os.path.join(ROOT, "02-DECISIONS", "[0-9]*.md"))):
+        name = os.path.basename(path)
+        number = name.split("-", 1)[0]
+        if not number.isdigit():
+            continue
+        if number in seen_records:
+            bad(os.path.join("02-DECISIONS", name),
+                "is numbered %s, and so is %s -- a record's number is how it is cited. Take the next "
+                "free number across main AND every open pull request; the branch that lands last "
+                "renumbers" % (number, seen_records[number]))
+        else:
+            seen_records[number] = name
+
     for path in sorted(glob.glob(os.path.join(ROOT, "04-ISSUES", "*", "00-report.md"))):
         front = frontmatter(path)
         if front is None:

02-DECISIONS/0168-a-converged-machine-is-filtered-by-the-mesh-alone.md

@@ -113,6 +113,22 @@ That is a difference a take shows, not a fault, and is decided when it bites.
 | `node show` lists filters with owners; `status` names a converged machine something else filters and is not well; the preview lists filters and fates | controller tests over a fixture report |
 | Live | the home server's record names the predecessor's chain in the runtime's user chain as *other*; `status` names the machine; after the operator removes the chain, the next report drops it and `status` is well |
 
+## Built and proven live, 2026-10-02
+
+> **Progressive insight — 2026-10-02.** The decision stands; these are the facts of its building.
+
+Built in mesh-host 67 (every refusing table and legacy chain classified with an owner, reported with
+every apply; the found firewall retired on every converged apply, *found inactive* kept apart from
+*disabled by the mesh*, a skipped step said) and mesh-controller 211 (kept per node, shown on `node
+show`, named by `status` and not well, previewed with fates). The live row was read at 10:10Z: the home
+server's record named the predecessor's chain in the legacy filter's user chain as *other*, beside two
+chains a retired front end left in the IPv6 legacy filter; the control node's record named the same two
+leftovers; the laptop and the workstation read *the mesh alone*; `status` named both machines. The five
+rule sets were removed at 12:46Z through the packet filter seat's `remove` verb
+([ADR 0170](0170-the-firewall-seat-serves-its-verbs.md)), and the next report read *the mesh alone* on
+all four machines. The control node's record still says the mesh retired its front end, which issue 143
+records as a hand's work: the host trusts its record, and from this build on the distinction is kept.
+
 ## References
 
 - [ADR 0100](0100-a-node-in-use-is-adopted-before-it-is-converged.md), [ADR 0103](0103-what-an-adopted-node-holds-and-what-its-guard-refuses.md), [ADR 0140](0140-the-filter-constrains-what-arrives-from-outside.md), [ADR 0102](0102-the-mesh-writes-into-a-shared-file-never-over-it.md), [ADR 0163](0163-taking-a-module-over-is-a-comparison.md)

02-DECISIONS/0170-the-firewall-seat-serves-its-verbs.md

@@ -7,7 +7,7 @@ reconstructed: false
 extends: 02-DECISIONS/0168-a-converged-machine-is-filtered-by-the-mesh-alone.md
 ---
 
-# 169. The firewall seat serves its verbs, and a foreign rule set is removed through one of them
+# 170. The firewall seat serves its verbs, and a foreign rule set is removed through one of them
 
 ## Context
 
@@ -78,6 +78,25 @@ how the act reaches the machine, recorded on the bus like every other, instead o
 | A container's capabilities reach the runtime and its spec; an unknown name is refused | host tests |
 | Live | `node-packet-filter.remove@<node>` on the home server and the control node; `node show` reads *the mesh alone* on both; `status` is well |
 
+## Built and proven live, 2026-10-02
+
+> **Progressive insight — 2026-10-02.** The decision stands; these are the facts of its building.
+> Written as 0169 for three hours and renumbered to 0170: another record took 0169 on main first,
+> and the check that refuses a shared number covered issues only (now records too).
+
+Built in mesh-host 68 (`capabilities` on a container), mesh-controller 212 (the seat's three verbs)
+and 213 (the filter file a module names under `filtering.into` counts as declared for a mount — the
+module's first build was refused without it), mesh-catalog 216 (the nftables module's runtime and
+verbs) and mesh-tools 27 (the console lists a node-scoped seat's verbs with their scope and carries the
+machine; before it, the verbs were live on four machines and unreachable from the console —
+[issue 199](../04-ISSUES/199-a-node-scoped-seats-verb-could-not-be-called-through-the-console/00-report.md)).
+Each machine's holder was issued its bus account with `mesh-controller.issue`, the broker node pushed
+first. At 12:46Z the five rule sets ADR 0168 had named were removed through
+`node-packet-filter.remove`, three on the home server and two on the control node, each answering
+with the commands it ran; the next report read *the mesh alone* on all four machines and `status`
+listed nothing under `filtered`. The live row is read. What it cost on the way is
+[issue 200](../04-ISSUES/200-the-controllers-answer-to-the-console-is-refused-by-the-bus/00-report.md).
+
 ## References
 
 - [ADR 0168](0168-a-converged-machine-is-filtered-by-the-mesh-alone.md), [ADR 0154](0154-the-meshs-own-verbs-are-the-controller-seats-tools.md), [ADR 0159](0159-a-tool-call-names-the-machine-and-a-holder-serves-its-seats-verbs.md), [ADR 0121](0121-a-system-seat-is-named-for-its-scope-and-modules-define-their-own.md)

02-DECISIONS/0175-the-found-front-end-is-uninstalled-once-a-machine-is-converged.md

@@ -0,0 +1,66 @@
+---
+topic: the mesh
+status: accepted
+date: 2026-10-02
+deciders: jochen
+reconstructed: false
+extends: 02-DECISIONS/0168-a-converged-machine-is-filtered-by-the-mesh-alone.md
+---
+
+# 175. The found front end is uninstalled once a machine is converged
+
+## Context
+
+[ADR 0100](0100-a-node-in-use-is-adopted-before-it-is-converged.md) retires the firewall a machine
+was found with by disabling it, never flushing it, and keeps its configuration on disk so that
+returning the node to adopted can enable it again. [ADR 0168](0168-a-converged-machine-is-filtered-by-the-mesh-alone.md)
+made the host keep it retired and say so. Both machines of this mesh that had a front end have been
+converged for days; neither is going back. What remained of the front end on each — its package,
+its unit enabled for boot on one, its empty chains still wired into the kernel's hooks, a chain of
+its container integration still dropping traffic on the IPv6 path until the day before this record
+— was not a rollback path. It was software nobody runs, left where a reader finds it and asks
+whether the machine has two firewalls.
+
+The operator asked on 2026-10-02 that it be disabled and uninstalled. Disabled it already was. For
+uninstalled, the host had no word: a package could be declared present and not absent.
+
+## Decision
+
+**1. A package may be declared absent.** `absent: true` on a package resource has the host remove
+the package when it is installed and leave alone a machine that never had it, through the machine's
+own package manager, dependencies untouched. A declaration that stops saying a package is absent
+installs nothing: there is nothing to undo.
+
+**2. The module that holds the packet filter seat declares the front end it replaced absent**, after
+its own filter is loaded, so the mesh's table is in force before the front end's package goes. On a
+converged machine the front end is therefore gone, not merely off; on an adopted machine nothing of
+this runs, because the filter module is assigned by the flip and not before.
+
+**3. Returning such a machine to adopted enables nothing.** A machine with no firewall needs no
+openings ([ADR 0100](0100-a-node-in-use-is-adopted-before-it-is-converged.md)); the host records the
+front end as *removed*, says so once, and asks nothing of a command that is not there. What
+ADR 0100 kept on disk for a return is kept only as far as the package manager keeps a changed
+configuration file; the rollback path it described is given up on purpose.
+
+## Consequences
+
+- The host's vocabulary grows by `absent` on a package; an older host refuses a declaration
+  carrying it, so the host rolls before the module.
+- The nftables module's declaration gains one resource; on the two machines of this mesh that were
+  found with ufw, the next push removes it.
+- `node show` reads *found firewall: ufw, removed* on those machines from then on.
+- ADR 0100's sentence about a return to adopted restoring the found firewall holds only while the
+  front end is installed, which after this record it is not on a converged machine.
+
+## How this is checked
+
+| Rule | Checked by |
+|---|---|
+| An absent package is removed when present, left when not, and read back | host tests over a fake package manager |
+| An uninstalled front end is recorded as removed and nothing is asked of it | a host test with ufw missing on a converged apply |
+| Live | the two machines report ufw gone: `pacman -Q ufw` has no answer, `node show` says removed, `status` is well |
+
+## References
+
+- [ADR 0100](0100-a-node-in-use-is-adopted-before-it-is-converged.md), [ADR 0168](0168-a-converged-machine-is-filtered-by-the-mesh-alone.md), [ADR 0170](0170-the-firewall-seat-serves-its-verbs.md)
+- [Design 08 — Connectivity](../03-DESIGN/01-to-be/08-connectivity.md)

02-DECISIONS/README.md

@@ -180,8 +180,9 @@ python3 00-META/checks/index.py            fail if stale
 - **0167** — [A membership carries what its module receives, and who the mesh is](0167-a-membership-carries-what-its-module-receives-and-who-the-mesh-is.md)
 - **0168** — [A converged machine is filtered by the mesh alone, and the host says what else refuses](0168-a-converged-machine-is-filtered-by-the-mesh-alone.md)
 - **0169** — [A machine joins through the tunnel, and the bus is never public](0169-a-machine-joins-through-the-tunnel-and-the-bus-is-never-public.md)
-- **0169** — [The firewall seat serves its verbs, and a foreign rule set is removed through one of them](0169-the-firewall-seat-serves-its-verbs.md)
+- **0170** — [The firewall seat serves its verbs, and a foreign rule set is removed through one of them](0170-the-firewall-seat-serves-its-verbs.md)
 - **0172** — [The lab is a module, and runs a bed when the mesh asks](0172-the-lab-is-a-module-and-runs-a-bed-when-the-mesh-asks.md)
+- **0175** — [The found front end is uninstalled once a machine is converged](0175-the-found-front-end-is-uninstalled-once-a-machine-is-converged.md)
 
 ### Its tiers, from the bottom up
 

03-DESIGN/01-to-be/08-connectivity.md

@@ -9,7 +9,8 @@ code:
   - mesh-host internal/apply (the service that reflects a rule set)
 updated: 2026-10-02
 decisions:
-  - 02-DECISIONS/0169-the-firewall-seat-serves-its-verbs.md
+  - 02-DECISIONS/0175-the-found-front-end-is-uninstalled-once-a-machine-is-converged.md
+  - 02-DECISIONS/0170-the-firewall-seat-serves-its-verbs.md
   - 02-DECISIONS/0169-a-machine-joins-through-the-tunnel-and-the-bus-is-never-public.md
   - 02-DECISIONS/0168-a-converged-machine-is-filtered-by-the-mesh-alone.md
   - 02-DECISIONS/0167-a-membership-carries-what-its-module-receives-and-who-the-mesh-is.md
@@ -767,11 +768,16 @@ tests over a fixture report check the recording, the preview's fates, the status
 predicate. Live: the home server's record names the predecessor's chain as *other* and `status`
 names the machine until the chain is removed by hand.
 
-*2026-10-02, [ADR 0169](../../02-DECISIONS/0169-the-firewall-seat-serves-its-verbs.md):* removing what
+*2026-10-02, [ADR 0170](../../02-DECISIONS/0170-the-firewall-seat-serves-its-verbs.md):* removing what
 the host reports as *other* is reached through the packet filter seat's `remove` verb, an operator's act
 by name on the bus; the seat also serves `rules` and `reload`, and its holder's runtime declares the
 `NET_ADMIN` capability on the machine's network. See design 33.
 
+*2026-10-02, [ADR 0175](../../02-DECISIONS/0175-the-found-front-end-is-uninstalled-once-a-machine-is-converged.md):*
+once a machine is converged, the front end it was found with is uninstalled, not merely disabled — the
+packet filter's holder declares its package absent after the mesh's filter is loaded, and a return to
+adopted then enables nothing. The rollback path ADR 0100 kept on disk is given up on purpose.
+
 ## 5 — Certificates
 
 **Two authorities, kept separate on purpose.**

03-DESIGN/01-to-be/33-the-tools-the-mesh-answers.md

@@ -4,7 +4,7 @@ status: implemented
 code: [mesh-controller, mesh-tools]
 updated: 2026-10-02
 decisions:
-  - 02-DECISIONS/0169-the-firewall-seat-serves-its-verbs.md
+  - 02-DECISIONS/0170-the-firewall-seat-serves-its-verbs.md
   - 02-DECISIONS/0160-the-mesh-issues-an-assignments-subjects-and-a-runtime-serves-what-it-is-issued.md
   - 02-DECISIONS/0159-a-tool-call-names-the-machine-and-a-holder-serves-its-seats-verbs.md
   - 02-DECISIONS/0154-the-meshs-own-verbs-are-the-controller-seats-tools.md
@@ -172,7 +172,7 @@ seats' schemas beyond the names their manifests already list.
 
 ## The firewall seat's verbs, 2026-10-02
 
-[ADR 0169](../../02-DECISIONS/0169-the-firewall-seat-serves-its-verbs.md). The first node-scoped seat
+[ADR 0170](../../02-DECISIONS/0170-the-firewall-seat-serves-its-verbs.md). The first node-scoped seat
 to carry verbs: `node-packet-filter` serves `rules` (the filter as the machine enforces it, nftables
 and legacy), `reload` (the mesh's own filter from its file) and `remove` (one rule set the mesh did
 not write, named as the host reports it under ADR 0168; refusing the mesh's tables, the runtime's

04-ISSUES/199-a-node-scoped-seats-verb-could-not-be-called-through-the-console/00-report.md

@@ -11,7 +11,7 @@ amended-design:
 ## What was observed
 
 2026-10-02, the first time a node-scoped seat declared verbs
-([ADR 0169](../../02-DECISIONS/0169-the-firewall-seat-serves-its-verbs.md)). The packet filter's
+([ADR 0170](../../02-DECISIONS/0170-the-firewall-seat-serves-its-verbs.md)). The packet filter's
 holder on every machine served `rules`, `reload` and `remove` on the seat's per-machine subjects, and
 the bus admitted them. The console answered every call with *nothing serves
 node-packet-filter.rules@<machine>*.