rollout check dials the bus the way the mesh does

The probe connected bare, and a bus that requires TLS and a user refused it at the handshake —
so the check reported the standing server as absent. It now dials with the controller's own
credential and pin, which is the one fact the check is there to report.

cmd/mesh-builder/main.go

@@ -17,12 +17,7 @@ package main
 
 import (
 	"context"
-	"crypto/sha256"
-	"crypto/tls"
-	"crypto/x509"
-	"encoding/hex"
 	"encoding/json"
-	"errors"
 	"fmt"
 	"net/url"
 	"os"
@@ -30,8 +25,6 @@ import (
 	"strings"
 	"syscall"
 
-	amqp "github.com/rabbitmq/amqp091-go"
-
 	"github.com/novox/mesh-controller/internal/broker"
 	"github.com/novox/mesh-controller/internal/builder"
 	"github.com/novox/mesh-controller/internal/link"
@@ -52,7 +45,6 @@ const usage = `mesh-builder — builds modules for the mesh
 It consumes build requests and answers with what it made. Nothing is listened on and nothing
 is dialled except the broker.
 
-  MESH_BROKER_AMQP   where the broker is, with this builder's own credential
   MESH_BROKER_FILE   a file the mesh sealed to this machine holding the same
   MESH_REGISTRY      host:port to publish artifacts to, when the mesh has not said
   MESH_BINDING       a file the mesh wrote saying where the artifact store is
@@ -135,43 +127,18 @@ func run() error {
 // machine told about both would take work from one and answer on the other, and every log line would
 // say it was fine.
 func takeWorkFrom(credential Credential, on string) (link.BuildMachine, error) {
-	// **The credential decides, before any variable does.** A machine moved to the new bus was
-	// handed a credential for it and nothing else changed in its environment; that credential
-	// names the bus by scheme, so it is enough to know which bus to take work from.
-	if credential.onTheNewBus() {
+	// **The credential names the bus, and there is one** (novox/hq ADR 0131, design 28 task 5.5).
+	// A credential for the mesh's bus carries user, password and fingerprint beside the address,
+	// and that is enough to dial it, pinned.
+	if !credential.onTheNewBus() {
+		return nil, fmt.Errorf("the credential at hand names %q, which is not the mesh's bus", credential.URL)
+	}
 	js, err := broker.DialPinned(credential.natsURL(), credential.Fingerprint)
 	if err != nil {
 		return nil, err
 	}
 	return link.MachineOverNATS(js, on), nil
 }
-	address, onNATS, err := broker.OnNATS()
-	if err != nil {
-		return nil, err
-	}
-	if err := broker.MustBeOneBus(credential.URL, address); err != nil {
-		return nil, err
-	}
-	if onNATS {
-		js, err := broker.Dial(address)
-		if err != nil {
-			return nil, fmt.Errorf("cannot reach the bus at %s: %w", address, err)
-		}
-		return link.MachineOverNATS(js, on), nil
-	}
-
-	conn, err := dial(credential)
-	if err != nil {
-		// Not quoted back: the URL carries this builder's broker password.
-		return nil, fmt.Errorf("cannot reach the broker: %w", err)
-	}
-	channel, err := conn.Channel()
-	if err != nil {
-		conn.Close()
-		return nil, err
-	}
-	return link.MachineOverCurrent(conn, channel, on), nil
-}
 
 // answer does one build and says what happened, whichever way it went.
 func answer(ctx context.Context, publisher builder.Publisher, on, workspace string, work link.Build) {
@@ -452,13 +419,8 @@ func brokerFrom() (Credential, error) {
 		// broker is then verified against whatever this machine already trusts.
 		return Credential{URL: said}, nil
 	}
-	url := strings.TrimSpace(os.Getenv("MESH_BROKER_AMQP"))
-	if url == "" {
 	return Credential{}, fmt.Errorf(
-			"neither MESH_BROKER_FILE nor MESH_BROKER_AMQP: a builder with no broker has " +
-				"nothing to build")
-	}
-	return Credential{URL: url}, nil
+		"no MESH_BROKER_FILE: a build machine with no credential for the bus has nothing to build")
 }
 
 // Credential is what a build machine is given so it can reach the broker.
@@ -491,43 +453,3 @@ func (c Credential) natsURL() string {
 	}
 	return "nats://" + c.User + ":" + c.Password + "@" + rest
 }
-
-// dial opens the connection, pinning the broker's certificate when there is one to pin.
-func dial(held Credential) (*amqp.Connection, error) {
-	if held.Fingerprint == "" {
-		return amqp.Dial(held.URL)
-	}
-	return amqp.DialTLS(held.URL, pinning(held.Fingerprint))
-}
-
-// pinning is a TLS configuration that trusts exactly one certificate.
-//
-// InsecureSkipVerify with a VerifyPeerCertificate is **pinning, not skipping**: the standard chain
-// check is replaced, not removed, and what replaces it is stricter — one certificate is accepted
-// rather than every certificate a public authority would sign.
-//
-// Its own function so a test can drive it against a real handshake. A pin check that is only ever
-// exercised through a broker is a pin check nothing tests.
-func pinning(fingerprint string) *tls.Config {
-	return &tls.Config{
-		InsecureSkipVerify: true,
-		VerifyPeerCertificate: func(raw [][]byte, _ [][]*x509.Certificate) error {
-			if len(raw) == 0 {
-				return errors.New("the broker presented no certificate")
-			}
-			// The leaf, and in the same spelling the mesh writes it — `sha256:` and 64 hex
-			// characters. Comparing a bare digest against a written fingerprint never matches,
-			// and the failure is indistinguishable from being pointed at the wrong broker.
-			sum := sha256.Sum256(raw[0])
-			got := "sha256:" + hex.EncodeToString(sum[:])
-			if got != fingerprint {
-				return fmt.Errorf(
-					"this is not the broker this builder was told about\n  expected %s\n  "+
-						"got      %s\nEither this mesh's broker was replaced, or this builder is "+
-						"being pointed at something else. Retrying will not help",
-					fingerprint, got)
-			}
-			return nil
-		},
-	}
-}

cmd/mesh-builder/where_test.go

@@ -15,6 +15,8 @@ import (
 	"strings"
 	"testing"
 	"time"
+
+	"github.com/novox/mesh-controller/internal/broker"
 )
 
 // Where a builder publishes.
@@ -193,9 +195,9 @@ func TestThePinIsComparedInTheSpellingTheMeshWritesIt(t *testing.T) {
 	}
 }
 
-// handshakeWith runs the builder's own pin check against an address.
+// handshakeWith runs the pin check the builder dials with against an address.
 func handshakeWith(address, pin string) error {
-	conn, err := tls.Dial("tcp", address, pinning(pin))
+	conn, err := tls.Dial("tcp", address, broker.PinnedToFingerprint(pin))
 	if err != nil {
 		return err
 	}

cmd/mesh-controller/addresses_test.go

@@ -17,8 +17,8 @@ import (
 
 var aDigest = "sha256:" + strings.Repeat("e", 64)
 
-// **A build is recorded by digest and path**, whatever address the builder pushed to — and only
-// what the build made is rewritten: an image the module runs from elsewhere is left where it says.
+// **A build is recorded by digest and path**, whatever address the builder pushed to — what it
+// made and what it stood on both; an image the module runs from elsewhere is left where it says.
 func TestABuildIsRecordedWithoutTheStoresAddress(t *testing.T) {
 	manifest, _ := json.Marshal(map[string]any{
 		"module": "gitea", "version": "1",
@@ -65,8 +65,11 @@ func TestABuildIsRecordedWithoutTheStoresAddress(t *testing.T) {
 	if strings.Contains(string(kept.Manifest), "anchor.internal:5100") {
 		t.Errorf("the recorded manifest still carries the store's address:\n%s", kept.Manifest)
 	}
-	if kept.Against[0] != "anchor.internal:5100/mesh-tools/runtime@"+aDigest {
-		t.Errorf("what the build stood on was rewritten: %v", kept.Against)
+	// What the build stood on is an edge to another module's artifact, and it is recorded the way
+	// that artifact is: by path in the store, so the edge still names the same thing when the
+	// store answers at another address.
+	if kept.Against[0] != catalogue.ArtifactStoreScheme+"mesh-tools/runtime@"+aDigest {
+		t.Errorf("what the build stood on was recorded by address: %v", kept.Against)
 	}
 }
 

cmd/mesh-controller/ask.go

@@ -43,7 +43,7 @@ func askCommand(ctx context.Context, args []string) error {
 	}
 	defer server.Close()
 
-	answer, err := link.Ask(ctx, server.Channel(), module, tool, arguments, *wait)
+	answer, err := link.Ask(ctx, server.Bus(), module, tool, arguments, *wait)
 	if err != nil {
 		return err
 	}

cmd/mesh-controller/build.go

@@ -2,8 +2,6 @@ package main
 
 import (
 	"context"
-	"crypto/rand"
-	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"flag"
@@ -31,6 +29,51 @@ import (
 // control plane may send a machine is bounded by the declaration language. This is the shape the
 // builder module will take when it is given work over the broker; today a person runs it, and the
 // mesh records the result the same way either way.
+// buildOn rebuilds every module the mesh holds that stands on the named module's artifacts — the
+// rebuild a changed base needs, which nothing else asks for: their sources did not move, and
+// "behind" does not see a base that did (novox/hq 04-ISSUES/131). Bases first among them too.
+func buildOn(ctx context.Context, base string, wait time.Duration) error {
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+	held, err := open.inventory.Catalogued(ctx)
+	if err != nil {
+		return err
+	}
+	against, err := open.inventory.BuiltAgainst(ctx)
+	if err != nil {
+		return err
+	}
+	var on []inventory.Entry
+	for _, e := range held {
+		if standsOnModule(e, base, against) {
+			on = append(on, e)
+		}
+	}
+	if len(on) == 0 {
+		fmt.Printf("nothing the mesh holds stands on %s\n", base)
+		return nil
+	}
+	on = orderByBases(on, against)
+	fmt.Printf("%d module(s) stand on %s:\n", len(on), base)
+	var failed []string
+	for _, e := range on {
+		fmt.Printf("--- %s\n", e.Manifest.Module)
+		source := buildSource{Repository: e.Source.Repository, Seat: e.Source.Seat}
+		if err := buildOne(ctx, source, e.Source.Path, e.Source.Ref, wait); err != nil {
+			fmt.Printf("  %v\n", err)
+			failed = append(failed, e.Manifest.Module)
+		}
+	}
+	if len(failed) > 0 {
+		return fmt.Errorf("%d of %d could not be built: %s", len(failed), len(on), strings.Join(failed, ", "))
+	}
+	fmt.Printf("\n%d module(s) rebuilt on %s. `push --behind` sends them on\n", len(on), base)
+	return nil
+}
+
 func buildCommand(ctx context.Context, args []string) error {
 	set := flag.NewFlagSet("build", flag.ContinueOnError)
 	ref := set.String("ref", "", "the branch, tag or commit to build")
@@ -46,6 +89,7 @@ func buildCommand(ctx context.Context, args []string) error {
 	// retype each repository is asking them to be the loop. Naming a repository and asking which
 	// ones need building are different requests, so they are not combined.
 	behind := set.Bool("behind", false, "every module the mesh holds older than its source has")
+	on := set.String("on", "", "rebuild every module that stands on this module's artifacts — the rebuild a changed base needs")
 	// A repository on the mesh's own forge, named by its path there (novox/hq ADR 0111). Without it
 	// the repository is external, cloned exactly as given — see source.go.
 	self := set.Bool("self", false, "the repository is a path on the forge holding the git seat")
@@ -53,6 +97,13 @@ func buildCommand(ctx context.Context, args []string) error {
 	if err != nil {
 		return err
 	}
+	if *on != "" {
+		if len(positionals) != 0 || *behind || *self {
+			return errors.New("build --on <module> names a base and nothing else")
+		}
+		return buildOn(ctx, *on, *wait)
+	}
+
 	if *behind {
 		if len(positionals) != 0 || *self {
 			return errors.New("build <repository> or build --behind, not both: one names a " +
@@ -61,7 +112,7 @@ func buildCommand(ctx context.Context, args []string) error {
 		return buildBehind(ctx, *wait)
 	}
 	if len(positionals) != 1 {
-		return errors.New("build <repository> [--self] [--path P] [--ref R] [--wait D] [--dry-run]")
+		return errors.New("build <repository> [--self] [--path P] [--ref R] [--wait D] [--dry-run]  |  build --behind  |  build --on <module>")
 	}
 	source := buildSource{Repository: positionals[0]}
 	if *self {
@@ -81,8 +132,9 @@ func buildCommand(ctx context.Context, args []string) error {
 //
 // **By digest and path, never by where it was pushed** (novox/hq 04-ISSUES/102). The builder
 // says `<registry>:<port>/<module>/<artifact>@sha256:…`; the mesh records the artifact-store
-// reference and composes the store's address back in where a reference is used. `against` is kept
-// as announced: it is what the build stood on as the builder saw it, and the catalogue's edge.
+// reference and composes the store's address back in where a reference is used. `against` — what
+// the build stood on, the catalogue's edge — is recorded the same way, so an edge names a module's
+// artifact and not the machine it was pulled from.
 func buildFrom(result link.BuildResult) inventory.Build {
 	kept := inventory.Build{
 		ID: result.ID, Repository: result.Repository, Ref: result.Ref,
@@ -92,7 +144,10 @@ func buildFrom(result link.BuildResult) inventory.Build {
 		// edges, and it is not always listening when a build happens — on a fresh mesh it cannot
 		// be, for exactly the modules it needs most. Keeping them is what makes a replay able to
 		// rebuild the graph rather than a list of names.
-		Path: result.Path, Against: result.Against,
+		Path: result.Path,
+	}
+	for _, ref := range result.Against {
+		kept.Against = append(kept.Against, catalogue.Recorded(ref))
 	}
 	var announced []inventory.Artifact
 	for _, made := range result.Made {
@@ -206,85 +261,45 @@ func builderCommand(ctx context.Context, args []string) error {
 	}
 	name := positionals[1]
 
-	management, err := broker.ManagementFromEnvironment()
+	// **The build machine's credential is a module's credential** (novox/hq ADR 0131, design 28
+	// task 5.5): minted into the mesh's records and sealed to the machine as the builder module's
+	// broker secret, usable at the next push — the same act `module issue` performs, and the same
+	// account the composed user list carries. Nothing is created on a server; the bus reads the list.
+	open, err := openStores(ctx)
 	if err != nil {
 		return err
 	}
-
-	// The same shape of secret a token carries: enough entropy that guessing is not a strategy,
-	// and safe to put in a URL because that is where it goes.
-	raw := make([]byte, 32)
-	if _, err := rand.Read(raw); err != nil {
-		return err
-	}
-	password := base64.RawURLEncoding.EncodeToString(raw)
-	if err := management.CreateBuilderAccount(ctx, name, password); err != nil {
-		return err
-	}
-
-	fmt.Printf("broker account %s created, scoped to the %s queue and the %s exchange\n\n",
-		name, link.BuildQueue, link.Exchange)
-
-	if *forNode != "" {
-		known, err := broker.FromEnvironment()
-		if err != nil {
-			return fmt.Errorf("cannot deliver a credential without knowing where the broker is: %w", err)
-		}
-		inv, err := openInventory(ctx)
+	defer open.Close()
+	inv := open.inventory
+	shelf, err := inv.Catalogue(ctx)
 	if err != nil {
 		return err
 	}
-		defer inv.Close()
-
-		brokerAddr, err := brokerReachableAt(ctx, inv, known, *forNode)
+	m, known := shelf[*module]
+	if !known {
+		return fmt.Errorf("%s is not in the catalogue; `module add` it first", *module)
+	}
+	fmt.Printf("build machine %s: ", name)
+	node := *forNode
+	if node == "" {
+		entries, err := inv.Catalogued(ctx)
 		if err != nil {
 			return err
 		}
-
-		// The URL and what verifies the broker, together. A mesh's broker presents a certificate
-		// of the mesh's own, which is in no public trust store — so a URL on its own reaches only
-		// a broker somebody else vouches for, and the connection fails at TLS with an error about
-		// an unknown authority rather than about a missing pin.
-		//
-		// **The same two facts a node's token carries** (novox/hq ADR 0004), delivered the same
-		// way: out of band relative to the broker, so what is trusted does not come from the thing
-		// being trusted.
-		held, err := json.Marshal(struct {
-			URL         string `json:"url"`
-			Fingerprint string `json:"fingerprint,omitempty"`
-		}{
-			URL:         fmt.Sprintf("amqps://%s:%s@%s/", name, password, brokerAddr),
-			Fingerprint: known.Fingerprint,
-		})
+		for _, e := range entries {
+			if e.Manifest.Module == *module && len(e.On) > 0 {
+				node = e.On[0]
+			}
+		}
+	}
+	if node == "" {
+		return fmt.Errorf("%s is assigned nowhere; `assign <machine> %s` first, or say --node", *module, *module)
+	}
+	address, err := broker.BusAddress()
 	if err != nil {
 		return err
 	}
-		if err := inv.AcceptSecretForModule(ctx, *forNode, *module, "broker", string(held)); err != nil {
-			return err
-		}
-		// Not printed. It is sealed to that machine and the mesh cannot read it back, which is
-		// the whole point — printing it here would put the one copy that matters on a terminal.
-		fmt.Printf("  sealed to %s, for the %s module. It arrives with the next push.\n",
-			*forNode, *module)
-		fmt.Printf("  run `push %s` to send it\n", *forNode)
-		return nil
-	}
-
-	// The whole line only when the address is known. A URL with a placeholder where the host
-	// should be is a URL somebody pastes and then debugs, and the placeholder is the last thing
-	// they look at.
-	if known, err := broker.FromEnvironment(); err == nil {
-		fmt.Printf("  MESH_BROKER_AMQP=amqps://%s:%s@%s/\n\n", name, password, known.Address)
-	} else {
-		fmt.Printf("  the password is %s\n\n", password)
-		fmt.Printf("  This control plane has no %s, so it cannot say where the broker is.\n"+
-			"  Put the password in MESH_BROKER_AMQP on the build machine.\n\n",
-			broker.AddressVar)
-	}
-	// Shown once, like a token, and for the same reason: what is stored is the broker's own hash
-	// of it, and a control plane that could show it back would be a control plane that holds it.
-	fmt.Println("This is the only time it is shown.")
-	return nil
+	return issueOnTheNewBus(ctx, inv, m, node, address)
 }
 
 // buildBehind builds every module the mesh holds older than its source has.
@@ -329,6 +344,14 @@ func buildBehind(ctx context.Context, wait time.Duration) error {
 	}
 	fmt.Println()
 
+	// Bases first: a module built before the module it stands on is built against the old one
+	// and reports success (novox/hq 04-ISSUES/131).
+	against, err := inv.BuiltAgainst(ctx)
+	if err != nil {
+		return err
+	}
+	stale = orderByBases(stale, against)
+
 	var failed []string
 	for _, e := range stale {
 		fmt.Printf("--- %s\n", e.Manifest.Module)
@@ -575,16 +598,10 @@ func heldBy(ctx context.Context) map[string]string {
 // **One place chooses**, as everywhere else the bus change went (novox/hq ADR 0116 step 5). On the bus
 // the mesh runs on today this needs the controller's own connection, so it is handed one; on the bus
 // being built it dials, because a build request is a one-shot and holds nothing else.
-func askOver(server *link.Server) (link.Builders, error) {
-	address, onNATS, err := broker.OnNATS()
+func askOver(_ *link.Server) (link.Builders, error) {
+	address, err := broker.BusAddress()
 	if err != nil {
 		return nil, err
 	}
-	if err := broker.MustBeOneBus(os.Getenv(broker.AMQPVarName), address); err != nil {
-		return nil, err
-	}
-	if onNATS {
 	return link.BuildsOverNATS(address)
 }
-	return link.BuildsOverCurrent(server.Channel()), nil
-}

cmd/mesh-controller/main.go

@@ -184,6 +184,7 @@ func usage() {
   operator key show                         the operator key, and what it can recover
   build <repository> [--ref R]   have a build machine build it, and record what came out
   build --behind                 build every module the mesh holds older than its source
+  build --on <module>            rebuild every module that stands on this module's artifacts, bases first
   builds [<module>]              what has been built lately, and what came of it
   builder issue <name>           a broker account for a build machine, scoped to build work,
                                  delivered as the builder module's broker secret (module add it first)

cmd/mesh-controller/modules.go

@@ -2,8 +2,6 @@ package main
 
 import (
 	"context"
-	"crypto/rand"
-	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"flag"
@@ -261,77 +259,11 @@ func moduleCommand(ctx context.Context, args []string) error {
 		// made in entirely different ways: on the bus the mesh runs on today an account is a
 		// management call, and on the bus being built it is a row the next composition writes into
 		// the server's user list (novox/hq design 25 §4).
-		busAddress, onNATS, err := broker.OnNATS()
+		busAddress, err := broker.BusAddress()
 		if err != nil {
 			return err
 		}
-		if err := broker.MustBeOneBus(os.Getenv(broker.AMQPVarName), busAddress); err != nil {
-			return err
-		}
-		if onNATS {
 		return issueOnTheNewBus(ctx, inv, m, *forNode, busAddress)
-		}
-
-		management, err := broker.ManagementFromEnvironment()
-		if err != nil {
-			return err
-		}
-		// The foundation owns the bus; make sure it exists before a module binds onto it.
-		if err := management.EnsureEventExchanges(ctx); err != nil {
-			return err
-		}
-
-		secret := make([]byte, 32)
-		if _, err := rand.Read(secret); err != nil {
-			return err
-		}
-		password := base64.RawURLEncoding.EncodeToString(secret)
-		account, err := management.CreateModuleAccount(ctx, *forNode, module, password, m.Emits, m.Consumes)
-		if err != nil {
-			return err
-		}
-		// A consumer's queue, with its dead-letter, is the foundation's to declare — its own account
-		// may not (ADR 0043). Made now, so it exists before the module binds onto it.
-		if len(m.Consumes) > 0 {
-			if err := management.EnsureModuleQueue(ctx, *forNode, module); err != nil {
-				return err
-			}
-		}
-
-		known, err := broker.FromEnvironment()
-		if err != nil {
-			return fmt.Errorf("cannot deliver a credential without knowing where the broker is: %w", err)
-		}
-		brokerAddr, err := brokerReachableAt(ctx, inv, known, *forNode)
-		if err != nil {
-			return err
-		}
-		// The URL and what verifies the broker, together — a mesh's broker presents its own
-		// certificate, in no public trust store, so a URL alone fails at TLS (as `builder issue`).
-		held, err := json.Marshal(struct {
-			URL         string `json:"url"`
-			Fingerprint string `json:"fingerprint,omitempty"`
-			Node        string `json:"node"`
-			Module      string `json:"module"`
-		}{
-			URL:         fmt.Sprintf("amqps://%s:%s@%s/", account, password, brokerAddr),
-			Fingerprint: known.Fingerprint,
-			// The node and module the account is for, so the runtime names its queue as the mesh
-			// scoped it (<node>.<module>.events) without a manifest having to interpolate a node.
-			Node:   *forNode,
-			Module: module,
-		})
-		if err != nil {
-			return err
-		}
-		if err := inv.AcceptSecretForModule(ctx, *forNode, module, "broker", string(held)); err != nil {
-			return err
-		}
-		fmt.Printf("broker account %s created for %s, scoped to what it emits and consumes\n",
-			account, module)
-		fmt.Printf("  sealed to %s. It arrives with the next push — `push %s` to send it\n",
-			*forNode, *forNode)
-		return nil
 
 	default:
 		return fmt.Errorf("module has no %q; it has add, list, moved, forget and issue", args[0])

cmd/mesh-controller/nodes.go

@@ -10,7 +10,6 @@ import (
 
 	"github.com/novox/mesh-controller/internal/broker"
 	"github.com/novox/mesh-controller/internal/inventory"
-	"github.com/novox/mesh-controller/internal/link"
 	"github.com/novox/mesh-controller/internal/token"
 )
 
@@ -258,15 +257,6 @@ func tokenCommand(ctx context.Context, args []string) error {
 	// chicken-and-egg entirely: the mesh runs the broker, so a joining node's credentials can
 	// exist before it does. The one-time secret IS the password, so a node's first connection is
 	// already authenticated and enrolment is what happens over it.
-	if management, err := broker.ManagementFromEnvironment(); err == nil {
-		if err := management.CreateNodeAccount(ctx, issued.Node.Name, issued.Secret); err != nil {
-			return err
-		}
-		fmt.Printf("broker account %s created, scoped to %s and the %s exchange\n\n",
-			issued.Node.Name, link.QueueFor(issued.Node.Name), link.Exchange)
-	} else if !errors.Is(err, broker.ErrNotConfigured) {
-		return err
-	}
 
 	made := token.Token{Node: issued.Node.Name, Signer: key.Public, Secret: issued.Secret,
 		Adopted: issued.Node.Adopted}

cmd/mesh-controller/order_test.go

@@ -0,0 +1,92 @@
+package main
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+	"github.com/novox/mesh-controller/internal/inventory"
+	"github.com/novox/mesh-controller/internal/link"
+)
+
+// entry is a module as the catalogue holds it: built, so its manifest carries no `build` any more.
+func entry(module string, _ ...string) inventory.Entry {
+	return inventory.Entry{Manifest: catalogue.Manifest{Module: module}}
+}
+
+// stoodOn is what each module's newest build recorded it was handed.
+func stoodOn(edges map[string][]string) map[string][]string {
+	out := map[string][]string{}
+	for module, bases := range edges {
+		for _, b := range bases {
+			out[module] = append(out[module], catalogue.ArtifactStoreScheme+b+"/runtime@sha256:"+strings.Repeat("0", 64))
+		}
+	}
+	return out
+}
+
+// A module built before the module it stands on is built against the old one and reports success
+// (novox/hq 04-ISSUES/131). So bases come first, however the set arrived.
+func TestBasesAreBuiltBeforeWhatStandsOnThem(t *testing.T) {
+	in := []inventory.Entry{entry("app"), entry("runtime"), entry("other"), entry("base")}
+	edges := stoodOn(map[string][]string{"app": {"runtime"}, "runtime": {"base"}})
+	got := orderByBases(in, edges)
+	pos := map[string]int{}
+	for i, e := range got {
+		pos[e.Manifest.Module] = i
+	}
+	if !(pos["base"] < pos["runtime"] && pos["runtime"] < pos["app"]) {
+		t.Fatalf("bases not first: %v", pos)
+	}
+	if len(got) != 4 {
+		t.Fatalf("an entry was lost or doubled: %d", len(got))
+	}
+	// A base outside the set is not waited for: it is not being rebuilt.
+	got = orderByBases([]inventory.Entry{entry("app")}, stoodOn(map[string][]string{"app": {"elsewhere"}}))
+	if len(got) != 1 {
+		t.Fatalf("a dependency outside the set changed the set: %v", got)
+	}
+}
+
+// A module registered from its manifest and never built still names its bases there; once built,
+// the recorded edge is what says so. Both are read, and a module never stands on itself.
+func TestWhatStandsOnAModuleIsReadFromItsBuildOrItsManifest(t *testing.T) {
+	built := entry("gitea")
+	edges := stoodOn(map[string][]string{"gitea": {"mesh-tools"}})
+	if !standsOnModule(built, "mesh-tools", edges) {
+		t.Fatal("a recorded edge was not read")
+	}
+	if standsOnModule(built, "gitea", edges) || standsOnModule(built, "postgres", edges) {
+		t.Fatal("an edge was invented")
+	}
+	fresh := inventory.Entry{Manifest: catalogue.Manifest{Module: "plex", Build: &catalogue.Build{
+		On: []catalogue.BuildsOn{{Arg: "RUNTIME_BASE", Module: "mesh-tools", Artifact: "runtime"}},
+	}}}
+	if !standsOnModule(fresh, "mesh-tools", nil) {
+		t.Fatal("a manifest's own base was not read")
+	}
+}
+
+// A merge names a repository the way the forge does; a source is recorded the way a build was
+// asked for. The two meet on owner/repo and branch, whichever form the record took.
+func TestAMergeMatchesTheSourcesBuiltFromIt(t *testing.T) {
+	m := link.SourceMoved{Owner: "novox", Repo: "mesh-controller", Base: "main",
+		CloneURL: "http://forge.internal:20000/novox/mesh-controller.git"}
+	for _, s := range []inventory.Source{
+		{Repository: "http://forge.internal:20000/novox/mesh-controller.git", Ref: "main"},
+		{Repository: "novox/mesh-controller", Seat: "git", Ref: ""},
+		{Repository: "https://elsewhere.example/novox/mesh-controller", Ref: "main"},
+	} {
+		if !sourceIs(s, m) {
+			t.Errorf("%+v was not matched by the merge", s)
+		}
+	}
+	for _, s := range []inventory.Source{
+		{Repository: "novox/mesh-host", Seat: "git"},
+		{Repository: "http://forge.internal:20000/novox/mesh-controller.git", Ref: "release"},
+	} {
+		if sourceIs(s, m) {
+			t.Errorf("%+v was matched by a merge that is not its", s)
+		}
+	}
+}

cmd/mesh-controller/push.go

@@ -42,16 +42,10 @@ func reportUnhostable(node string, plan catalogue.Resolution) {
 // variable moves it). The streams and this controller's consumers are raised first on the new bus,
 // so nothing served here finds them missing.
 func connectLink(ctx context.Context, inv *inventory.Inventory, enroller link.Enroller, listener link.Listener) (*link.Server, error) {
-	busAddress, onNATS, err := broker.OnNATS()
+	busAddress, err := broker.BusAddress()
 	if err != nil {
 		return nil, err
 	}
-	if err := broker.MustBeOneBus(os.Getenv(broker.AMQPVarName), busAddress); err != nil {
-		return nil, err
-	}
-	if !onNATS {
-		return link.Connect(enroller, listener)
-	}
 	if inv != nil {
 		if err := raiseTheBus(ctx, inv, busAddress); err != nil {
 			return nil, err
@@ -88,11 +82,6 @@ func serve(ctx context.Context) error {
 	}
 	fmt.Printf("signing as %s\n", key.Fingerprint()[:16])
 
-	management, err := broker.ManagementFromEnvironment()
-	if err != nil && !errors.Is(err, broker.ErrNotConfigured) {
-		return err
-	}
-
 	// Where the broker is and what to expect there, so a node can be told how to come back
 	// without a person and a new token.
 	known, err := broker.FromEnvironment()
@@ -107,16 +96,9 @@ func serve(ctx context.Context) error {
 	// **Which bus this mesh is on, read once** (novox/hq ADR 0116 step 5). Both clients ship; both
 	// being live is refused, because a mesh half on each is one where a declaration goes out on one
 	// and the report comes back on the other, and every component logs success while it happens.
-	busAddress, onNATS, err := broker.OnNATS()
-	if err != nil {
-		return err
-	}
-	if err := broker.MustBeOneBus(os.Getenv(broker.AMQPVarName), busAddress); err != nil {
-		return err
-	}
 
-	work := link.Enrolment{Inventory: inv, Identity: ident, Management: management, Broker: known,
-		OnNATS: onNATS}
+	work := link.Enrolment{Inventory: inv, Identity: ident, Broker: known,
+		OnNATS: true}
 	server, err := connectLink(ctx, inv, work, work)
 	if err != nil {
 		return err

cmd/mesh-controller/rollout.go

@@ -5,6 +5,7 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"os"
 	"strings"
 	"time"
 
@@ -33,7 +34,7 @@ import (
 // ability to change things, not the services its modules are serving — measured on 2026-09-27, when
 // a seat emptied mid-change and the control plane looped for two hours while every service stayed up.
 
-const rolloutUsage = "rollout check | rollout mint [--again] | rollout --confirm"
+const rolloutUsage = "rollout check | rollout mint [--again] | rollout hand <node> | rollout --confirm"
 
 func rolloutCommand(ctx context.Context, args []string) error {
 	switch {
@@ -41,6 +42,8 @@ func rolloutCommand(ctx context.Context, args []string) error {
 		return rolloutCheck(ctx)
 	case len(args) == 1 && args[0] == "mint":
 		return rolloutMint(ctx, false)
+	case len(args) == 2 && args[0] == "hand":
+		return rolloutHand(ctx, args[1])
 	case len(args) == 2 && args[0] == "mint" && args[1] == "--again":
 		// Every credential minted afresh, whether or not one exists — for a mint that was wrong
 		// before anything was pushed. Afterwards nothing that received the old one still works,
@@ -124,9 +127,13 @@ func readinessOf(ctx context.Context, inv *inventory.Inventory) (broker.Readines
 	if address != "" {
 		// One dial, briefly. "Is it answering" is the one fact records cannot hold, and a mesh about
 		// to move onto a server that is not there should hear it here rather than afterwards.
-		if conn, err := nats.Connect(broker.BareAddress(address), nats.Timeout(5*time.Second)); err == nil {
+		//
+		// **Dialled the way the mesh dials it** — credential and pin — because a bare connect to a
+		// bus that requires TLS and a user fails at the handshake, and the check then reported a
+		// standing server as absent (seen live, 2026-09-28).
+		if js, err := broker.Dial(address, nats.Timeout(5*time.Second)); err == nil {
 			state.ServerStanding = true
-			conn.Close()
+			js.Close()
 		}
 	}
 
@@ -387,3 +394,62 @@ func providesBus(m catalogue.Manifest) bool {
 	}
 	return false
 }
+
+// rolloutHand mints a machine its credential for the new bus afresh and prints its membership
+// once, for an operator to carry by hand — the rescue for a machine that cannot be reached over
+// any bus: rotated while it still held the old password, or reachable only by ssh. The plaintext
+// exists on this terminal and then only where it is written; the store keeps the hash, and the
+// sealed copy in the machine's declaration is replaced too, so the next push says the same.
+func rolloutHand(ctx context.Context, node string) error {
+	open, err := openStores(ctx)
+	if err != nil {
+		return err
+	}
+	defer open.Close()
+	inv := open.inventory
+
+	known, err := broker.FromEnvironment()
+	if err != nil {
+		return fmt.Errorf("the bus's certificate is not known to this process: %w", err)
+	}
+	busAddress, _, err := broker.OnNATS()
+	if err != nil {
+		return err
+	}
+	if busAddress == "" {
+		return errors.New("this control plane is not on the new bus, so there is no membership to hand out")
+	}
+	_, _, bare := broker.CredentialIn(busAddress)
+	if _, after, has := strings.Cut(bare, "://"); has {
+		bare = after
+	}
+	if _, err := inv.NodeByName(ctx, node); err != nil {
+		return err
+	}
+	p := broker.Principal{Kind: broker.KindNode, Node: node}
+	password, err := inv.MintBusPassword(ctx, inventory.BusUser{Username: p.Username(), Kind: inventory.BusNode, Node: node})
+	if err != nil {
+		return err
+	}
+	membership, _ := json.Marshal(map[string]string{
+		"broker": bare, "fingerprint": known.Fingerprint, "password": password, "transport": "nats",
+	})
+	key, err := inv.SealingKeyOf(ctx, node)
+	if err != nil {
+		return err
+	}
+	sealed, err := secrets.Seal(key, membership)
+	if err != nil {
+		return err
+	}
+	if err := inv.PutBusMembership(ctx, node, sealed); err != nil {
+		return err
+	}
+	// The one line of output is the membership itself, so it can be piped to the machine without
+	// being read on the way. Everything else goes to stderr.
+	fmt.Fprintf(os.Stderr, "%s's credential is minted afresh. Write this to %s on it and restart its host; "+
+		"then push the machine running the bus so the user list carries the new hash.\n",
+		node, catalogue.BusMembershipPath)
+	fmt.Println(string(membership))
+	return nil
+}

cmd/mesh-controller/upgrades.go

@@ -6,7 +6,9 @@ import (
 	"flag"
 	"fmt"
 	"strings"
+	"time"
 
+	"github.com/novox/mesh-controller/internal/catalogue"
 	"github.com/novox/mesh-controller/internal/inventory"
 	"github.com/novox/mesh-controller/internal/link"
 )
@@ -218,3 +220,145 @@ func notNow(err error) error {
 	}
 	return err
 }
+
+// SourceMoved is the forge announcing a merge: every module recorded as built from that
+// repository and branch is marked as moved to the merge commit, and built — bases first, so a
+// module that stands on another's artifact is built after it and not against the old one
+// (novox/hq 04-ISSUES/131). Nothing is pushed here: what a finished build does to the machines
+// running the module is the upgrade's decision, taken when the catalogue announces it.
+func (f following) SourceMoved(ctx context.Context, m link.SourceMoved) error {
+	inv := f.open.inventory
+	entries, err := inv.Catalogued(ctx)
+	if err != nil {
+		return notNow(err)
+	}
+	var moved []inventory.Entry
+	for _, e := range entries {
+		if !sourceIs(e.Source, m) {
+			continue
+		}
+		if e.Source.BuiltFrom == m.Commit {
+			continue
+		}
+		if err := inv.SourceMoved(ctx, e.Manifest.Module, m.Commit); err != nil {
+			return notNow(err)
+		}
+		moved = append(moved, e)
+	}
+	if len(moved) == 0 {
+		fmt.Printf("%s/%s merged into %s (%.8s); nothing the mesh holds is built from it\n",
+			m.Owner, m.Repo, m.Base, m.Commit)
+		return nil
+	}
+	against, err := inv.BuiltAgainst(ctx)
+	if err != nil {
+		return notNow(err)
+	}
+	ordered := orderByBases(moved, against)
+	names := make([]string, 0, len(ordered))
+	for _, e := range ordered {
+		names = append(names, e.Manifest.Module)
+	}
+	fmt.Printf("%s/%s merged into %s (%.8s); building %s\n",
+		m.Owner, m.Repo, m.Base, m.Commit, strings.Join(names, ", "))
+	var failed []string
+	for _, e := range ordered {
+		source := buildSource{Repository: e.Source.Repository, Seat: e.Source.Seat}
+		if err := buildOne(ctx, source, e.Source.Path, e.Source.Ref, 20*time.Minute); err != nil {
+			fmt.Printf("  %s: %v\n", e.Manifest.Module, err)
+			failed = append(failed, e.Manifest.Module)
+			// A base that failed is a reason to stop: what stands on it would be built against
+			// the old one, and report success (novox/hq 04-ISSUES/131).
+			if standsOn(ordered, e.Manifest.Module, against) {
+				fmt.Printf("  stopping: %s is a base of what was still to build\n", e.Manifest.Module)
+				break
+			}
+		}
+	}
+	if len(failed) > 0 {
+		fmt.Printf("%d of %d not built: %s\n", len(failed), len(ordered), strings.Join(failed, ", "))
+	}
+	return nil
+}
+
+// sourceIs is whether a recorded source is the repository and branch a merge announced. A source on
+// the git seat is recorded as its path on the forge; one elsewhere as the URL it was cloned from.
+// An empty recorded ref is the repository's default branch, which is what a merge into the base
+// branch of the forge's default means.
+func sourceIs(s inventory.Source, m link.SourceMoved) bool {
+	want := strings.ToLower(m.Owner + "/" + m.Repo)
+	repo := strings.ToLower(strings.TrimSuffix(s.Repository, ".git"))
+	matches := repo == want || strings.HasSuffix(repo, "/"+want) ||
+		(m.CloneURL != "" && strings.EqualFold(strings.TrimSuffix(s.Repository, ".git"), strings.TrimSuffix(m.CloneURL, ".git")))
+	if !matches {
+		return false
+	}
+	return s.Ref == "" || s.Ref == m.Base
+}
+
+// orderByBases is the entries with every base before what stands on it: a module whose build stood
+// on another's artifact comes after that module. Entries outside the set are not waited for — they
+// are not being rebuilt. Stable for what has no order between it.
+//
+// `against` is what each module's newest build stood on (inventory.BuiltAgainst): the edges are
+// derived from builds, not declared, because a recorded manifest no longer carries `build.on`.
+func orderByBases(entries []inventory.Entry, against map[string][]string) []inventory.Entry {
+	inSet := map[string]bool{}
+	for _, e := range entries {
+		inSet[e.Manifest.Module] = true
+	}
+	var out []inventory.Entry
+	placed := map[string]bool{}
+	var place func(e inventory.Entry, seen map[string]bool)
+	place = func(e inventory.Entry, seen map[string]bool) {
+		name := e.Manifest.Module
+		if placed[name] || seen[name] {
+			return
+		}
+		seen[name] = true
+		for _, base := range entries {
+			if base.Manifest.Module != name && inSet[base.Manifest.Module] && standsOnModule(e, base.Manifest.Module, against) {
+				place(base, seen)
+			}
+		}
+		placed[name] = true
+		out = append(out, e)
+	}
+	for _, e := range entries {
+		place(e, map[string]bool{})
+	}
+	return out
+}
+
+// standsOn is whether anything in the set is built on the named module's artifacts.
+func standsOn(entries []inventory.Entry, module string, against map[string][]string) bool {
+	for _, e := range entries {
+		if standsOnModule(e, module, against) {
+			return true
+		}
+	}
+	return false
+}
+
+// standsOnModule is whether an entry's build stood on the named module: by what its newest build
+// recorded it was handed (`artifact-store://<module>/<artifact>@…`, the module's own artifact), or
+// — for a module registered from a manifest and not yet built — by the base its manifest names.
+func standsOnModule(e inventory.Entry, module string, against map[string][]string) bool {
+	if e.Manifest.Module == module {
+		return false
+	}
+	if e.Manifest.Build != nil {
+		for _, on := range e.Manifest.Build.On {
+			if on.Module == module {
+				return true
+			}
+		}
+	}
+	prefix := catalogue.ArtifactStoreScheme + module + "/"
+	for _, ref := range against[e.Manifest.Module] {
+		if strings.HasPrefix(ref, prefix) {
+			return true
+		}
+	}
+	return false
+}

go.mod

@@ -4,7 +4,7 @@ go 1.26.0
 
 require (
 	github.com/jackc/pgx/v5 v5.10.0
-	github.com/rabbitmq/amqp091-go v1.14.0
+	github.com/nats-io/nats.go v1.54.0
 	golang.org/x/crypto v0.57.0
 )
 
@@ -13,7 +13,6 @@ require (
 	github.com/jackc/pgservicefile v0.0.0-20240606120523-5a60cdf6a761 // indirect
 	github.com/jackc/puddle/v2 v2.2.2 // indirect
 	github.com/klauspost/compress v1.20.0 // indirect
-	github.com/nats-io/nats.go v1.54.0 // indirect
 	github.com/nats-io/nkeys v0.4.16 // indirect
 	github.com/nats-io/nuid v1.0.1 // indirect
 	golang.org/x/net v0.58.0 // indirect

go.sum

@@ -19,15 +19,11 @@ github.com/nats-io/nuid v1.0.1 h1:5iA8DT8V7q8WK2EScv2padNa/rTESc1KdnPw4TC2paw=
 github.com/nats-io/nuid v1.0.1/go.mod h1:19wcPz3Ph3q0Jbyiqsd0kePYG7A95tJPxeL+1OSON2c=
 github.com/pmezard/go-difflib v1.0.0 h1:4DBwDE0NGyQoBHbLQYPwSUPoCMWR5BEzIk/f1lZbAQM=
 github.com/pmezard/go-difflib v1.0.0/go.mod h1:iKH77koFhYxTK1pcRnkKkqfTogsbg7gZNVY4sRDYZ/4=
-github.com/rabbitmq/amqp091-go v1.14.0 h1:RSaT7aOKt/OrkVUyswPDW29lnRz9psuGmfZFBmLqLek=
-github.com/rabbitmq/amqp091-go v1.14.0/go.mod h1:Hy4jKW5kQART1u+JkDTF9YYOQUHXqMuhrgxOEeS7G4o=
 github.com/stretchr/objx v0.1.0/go.mod h1:HFkY916IF+rwdDfMAkV7OtwuqBVzrE8GR6GFx+wExME=
 github.com/stretchr/testify v1.3.0/go.mod h1:M5WIy9Dh21IEIfnGCwXGc5bZfKNJtfHm1UVUgZn+9EI=
 github.com/stretchr/testify v1.7.0/go.mod h1:6Fq8oRcR53rry900zMqJjRRixrwX3KX962/h/Wwjteg=
 github.com/stretchr/testify v1.11.1 h1:7s2iGBzp5EwR7/aIZr8ao5+dra3wiQyKjjFuvgVKu7U=
 github.com/stretchr/testify v1.11.1/go.mod h1:wZwfW3scLgRK+23gO65QZefKpKQRnfz6sD981Nm4B6U=
-go.uber.org/goleak v1.3.0 h1:2K3zAYmnTNqV73imy9J1T3WC+gmCePx2hEGkimedGto=
-go.uber.org/goleak v1.3.0/go.mod h1:CoHD4mav9JJNrW/WLlf7HGZPjdw8EucARQHekz1X6bE=
 golang.org/x/crypto v0.57.0 h1:3ZVCjf8Ggz7zneR/EHRVx68Ctf+2pmIMP2UFhh9cC6M=
 golang.org/x/crypto v0.57.0/go.mod h1:Fdz0i5U6CoizGwLda9DttjSk6qlZo25zYNtR+ycvuZA=
 golang.org/x/net v0.58.0 h1:ynWG7rqYi4ccpTEuPZ2QGWHktVEM9DMCj9yzDE0Q7To=

internal/broker/agreement_test.go

@@ -1,67 +0,0 @@
-package broker_test
-
-import (
-	"regexp"
-	"testing"
-
-	"github.com/novox/mesh-controller/internal/broker"
-	"github.com/novox/mesh-controller/internal/link"
-)
-
-// The names are written twice, so a test keeps them agreeing.
-//
-// `link` imports `broker`, so `broker` cannot import `link` — the queue and exchange names
-// therefore exist in both. A scoped account naming a queue nothing publishes to produces a
-// builder that takes no work and says nothing about why, which is the worst kind of silence.
-//
-// An external test package, because it may import both without either importing the other.
-func TestTheNamesTheBrokerScopesAreTheNamesTheLinkUses(t *testing.T) {
-	for _, agreed := range []struct {
-		what     string
-		scoped   string
-		actually string
-	}{
-		{"the build queue", broker.BuildQueueName, link.BuildQueue},
-		{"the exchange", broker.ExchangeName, link.Exchange},
-		{"a node's queue", broker.QueueFor("somewhere"), link.QueueFor("somewhere")},
-	} {
-		if agreed.scoped != agreed.actually {
-			t.Errorf("%s: the broker scopes %q and the link uses %q",
-				agreed.what, agreed.scoped, agreed.actually)
-		}
-	}
-}
-
-func TestABuilderMayWriteToAReplyQueueAndReadNoNodesDeclarations(t *testing.T) {
-	// The scoping, checked as patterns rather than by connecting: what it may write must include
-	// the queue an asker actually waits on, and what it may read must not include any node's.
-	//
-	// This exists because the first version scoped writes to `amq.gen-*` — the name one broker
-	// happens to generate — and the builder built, could not answer, and the connection simply
-	// closed saying only "not allowed to publish to exchange \'\'". Answering through the
-	// exchange is what removed the need for any of that.
-	write := regexp.MustCompile("^" + regexp.QuoteMeta(broker.ExchangeName) + "$")
-	if !write.MatchString(broker.ExchangeName) {
-		t.Error("a builder may not write to the exchange, so it can take work and never answer")
-	}
-	// And not the default exchange, where permission is per exchange rather than per queue — a
-	// builder allowed to use it could publish into any node's queue.
-	//
-	// Confirmed against a real broker as well, and worth recording how that nearly went wrong:
-	// an unconfirmed publish is asynchronous, so a refusal arrives as a channel close afterwards
-	// and a naive check reports success. With publisher confirms the broker's refusal is
-	// immediate. **A negative security assertion made against an asynchronous call is not an
-	// assertion.**
-	if write.MatchString("") {
-		t.Error("a builder may publish to the default exchange, and so into any node's queue")
-	}
-
-	read := regexp.MustCompile("^" + regexp.QuoteMeta(broker.BuildQueueName) + "$")
-	if !read.MatchString(broker.BuildQueueName) {
-		t.Error("a builder may not read the build queue")
-	}
-	if read.MatchString(link.QueueFor("someone-else")) {
-		// A build machine is not a node, and a node's queue carries its declarations.
-		t.Error("a builder may read another machine's declarations")
-	}
-}

internal/broker/broker_test.go

@@ -194,16 +194,3 @@ func TestTheAddressPortFollowsThePortTwin(t *testing.T) {
 		t.Fatalf("the address is %q; the node put the bus on 5679", b.Address)
 	}
 }
-
-func TestTheManagementPortFollowsThePortTwin(t *testing.T) {
-	t.Setenv(ManagementVar, "http://guest:guest@127.0.0.1:15672")
-	t.Setenv(ManagementVar+"_FILE", "")
-	t.Setenv(ManagementVar+"_PORT", "15673")
-	m, err := ManagementFromEnvironment()
-	if err != nil {
-		t.Fatal(err)
-	}
-	if m.base.Host != "127.0.0.1:15673" {
-		t.Fatalf("the management API is at %q; the node put it on 15673", m.base.Host)
-	}
-}

internal/broker/management.go

@@ -1,366 +0,0 @@
-package broker
-
-import (
-	"bytes"
-	"context"
-	"encoding/json"
-	"fmt"
-	"github.com/novox/mesh-controller/internal/envfile"
-	"io"
-	"net/http"
-	"net/url"
-	"regexp"
-	"strings"
-	"time"
-)
-
-// The mesh runs the broker, so there is no chicken-and-egg in a node needing an account before it
-// can connect: the account is created when the token is issued, and the one-time secret in that
-// token IS the password. A node's first connection is already authenticated, and enrolment is
-// what happens over it.
-//
-// novox/hq ADR 0004's *a node holds its own identity and nothing else* is why the account is per
-// node rather than shared. A shared enrolment account would let any node consume another's queue,
-// which is the shared-credential fault that record exists to remove, reappearing at the transport.
-
-// ManagementVar holds the broker's management API, credentials included.
-const ManagementVar = "MESH_BROKER_MANAGEMENT"
-
-// safeName is what a node may be called at the broker.
-//
-// The name goes into a URL path and into permission patterns, which are regular expressions. A
-// name carrying a `.` or a `*` would silently widen what that node may reach — so it is
-// constrained here rather than escaped later, because an escape that is forgotten once is a node
-// reading everybody's queues.
-var safeName = regexp.MustCompile(`^[a-z0-9][a-z0-9-]{0,62}$`)
-
-// Management is the broker's administrative interface.
-type Management struct {
-	base   *url.URL
-	client *http.Client
-}
-
-// ManagementFromEnvironment reads where the management API is, if it is configured.
-//
-// On the port MESH_BROKER_MANAGEMENT_PORT names when the node moved it (novox/hq 04-ISSUES/102);
-// the URL's own port otherwise.
-func ManagementFromEnvironment() (*Management, error) {
-	raw, err := envfile.Placed(ManagementVar)
-	if err != nil {
-		return nil, err
-	}
-	if raw == "" {
-		return nil, ErrNotConfigured
-	}
-	base, err := url.Parse(raw)
-	if err != nil || base.Host == "" {
-		// The value carries a password, so it is not quoted back.
-		return nil, fmt.Errorf("%s is not a usable URL", ManagementVar)
-	}
-	return &Management{base: base, client: &http.Client{Timeout: 15 * time.Second}}, nil
-}
-
-// QueueFor is the queue a node consumes from. One per node, named after it.
-func QueueFor(node string) string { return "node." + node }
-
-// ExchangeName is where nodes publish what they have to say. One exchange, and the control plane
-// is the only consumer behind it (novox/hq ADR 0006 — one consumer, so two cannot silently split
-// the traffic between them).
-const ExchangeName = "mesh"
-
-// BuildQueueName is where build work waits. Duplicated from `link` rather than imported, for the
-// same reason QueueFor above is: this package must not depend on the one that uses it, and a
-// constant that differed would be caught by the test that asserts they agree.
-const BuildQueueName = "builds"
-
-// The events bus (novox/hq ADR 0042): one topic exchange every event rides, a second for tool
-// RPC kept apart, and a dead-letter home for a poison event. The foundation owns these — a module's
-// account cannot declare them, only bind its own queue to the events one.
-const (
-	EventsExchangeName = "mesh.events"
-	RPCExchangeName    = "mesh.rpc"
-	DeadExchangeName   = "mesh.events.dead"
-)
-
-// ModuleQueueFor is the durable queue a module consumes its events from — one per module per node
-// (novox/hq ADR 0042), named so the account that may read it is exactly this module's.
-func ModuleQueueFor(node, module string) string { return node + "." + module + ".events" }
-
-// modulePermissions is a module's authority on the bus, derived from its manifest (novox/hq
-// ADR 0043): what it consumes and what it emits, and nothing else. Pure, so the scope is tested as
-// patterns without a broker — the way a builder's is.
-//
-// A note on the limit: the broker's write permission is per exchange, not per routing key (LavinMQ
-// has no topic permissions), so an emitting module is granted the events exchange whole. ADR 0042's
-// origin reservation — a module publishes only under `module.<self>.*` — is stamped by the sdk, not
-// enforced here; that gap is the broker's, and is recorded rather than hidden. A pure consumer like
-// the audit logger is unaffected: it is granted no write to the exchange at all.
-func modulePermissions(node, module string, emits, consumes []string) (configure, write, read string) {
-	queue := regexp.QuoteMeta(ModuleQueueFor(node, module))
-	events := regexp.QuoteMeta(EventsExchangeName)
-	rpc := regexp.QuoteMeta(RPCExchangeName)
-	// A module serves each of its tools on its own queue, namespaced by the module (novox/hq
-	// ADR 0047) — serve.<module>.<tool> — so the account may declare, bind and read exactly its own,
-	// and no other module's.
-	serve := "serve\\." + regexp.QuoteMeta(module) + "\\..*"
-
-	// Declare its own events queue and its own tool serve queues.
-	configure = "^(" + queue + "|" + serve + ")$"
-
-	// Write to bind its queue and serve queues (binding is a write on the queue), and to the RPC
-	// exchange to publish replies (ADR 0047: replies ride mesh.rpc, never the default exchange, which
-	// would let it publish into any queue). To the events exchange only if it emits.
-	writes := []string{queue, serve, rpc}
-	if len(emits) > 0 {
-		writes = append(writes, events)
-	}
-	write = "^(" + strings.Join(writes, "|") + ")$"
-
-	// Read its own queue and serve queues to consume them, and the RPC exchange to bind its serve
-	// queues onto. The events exchange to bind onto only if it consumes.
-	reads := []string{queue, serve, rpc}
-	if len(consumes) > 0 {
-		reads = append(reads, events)
-	}
-	read = "^(" + strings.Join(reads, "|") + ")$"
-	return configure, write, read
-}
-
-// CreateModuleAccount gives an assigned module its own broker account, scoped by what it emits and
-// consumes (novox/hq ADR 0043). The account name carries the node so the same module on two machines
-// holds two accounts, each sealed to its own; the permissions carry the module so one module cannot
-// read another's queue. Generic — the builder is one instance of this rule, not a separate kind.
-func (m *Management) CreateModuleAccount(ctx context.Context, node, module, password string, emits, consumes []string) (string, error) {
-	if !safeName.MatchString(node) {
-		return "", fmt.Errorf("%q cannot be part of a broker account: it is a permission pattern", node)
-	}
-	if !safeName.MatchString(module) {
-		return "", fmt.Errorf("%q cannot be part of a broker account: it is a permission pattern", module)
-	}
-	account := node + "-" + module
-	if !safeName.MatchString(account) {
-		return "", fmt.Errorf("%q is not a usable broker account name", account)
-	}
-
-	if err := m.put(ctx, "/api/users/"+url.PathEscape(account),
-		map[string]string{"password": password, "tags": ""}); err != nil {
-		return "", fmt.Errorf("cannot create the broker account for %s on %s: %w", module, node, err)
-	}
-
-	configure, write, read := modulePermissions(node, module, emits, consumes)
-	if err := m.put(ctx, "/api/permissions/%2f/"+url.PathEscape(account), map[string]string{
-		"configure": configure, "write": write, "read": read,
-	}); err != nil {
-		return "", fmt.Errorf("cannot scope the broker account for %s on %s: %w", module, node, err)
-	}
-	return account, nil
-}
-
-// EnsureModuleQueue declares a consuming module's queue with its dead-letter exchange, idempotently.
-// The foundation declares it because a scoped module account may not: the broker refuses a queue with
-// a dead-letter exchange to a non-administrator (novox/hq ADR 0043), so a consumer passively checks
-// the queue the mesh made rather than declaring its own.
-func (m *Management) EnsureModuleQueue(ctx context.Context, node, module string) error {
-	queue := ModuleQueueFor(node, module)
-	if err := m.put(ctx, "/api/queues/%2f/"+url.PathEscape(queue), map[string]any{
-		"durable":   true,
-		"arguments": map[string]any{"x-dead-letter-exchange": DeadExchangeName},
-	}); err != nil {
-		return fmt.Errorf("cannot declare the queue for %s on %s: %w", module, node, err)
-	}
-	return nil
-}
-
-// EnsureEventExchanges declares the bus's exchanges and the dead-letter home, idempotently. The
-// foundation owns them (a module's account may not declare an exchange), and a dead-letter exchange
-// with no queue behind it drops what it receives — so a durable queue bound to `#` retains a poison
-// event for inspection, which is the whole reason the trail exists.
-func (m *Management) EnsureEventExchanges(ctx context.Context) error {
-	for _, exchange := range []string{EventsExchangeName, RPCExchangeName, DeadExchangeName} {
-		if err := m.put(ctx, "/api/exchanges/%2f/"+url.PathEscape(exchange),
-			map[string]any{"type": "topic", "durable": true}); err != nil {
-			return fmt.Errorf("cannot declare the %s exchange: %w", exchange, err)
-		}
-	}
-	if err := m.put(ctx, "/api/queues/%2f/"+url.PathEscape(DeadExchangeName),
-		map[string]any{"durable": true}); err != nil {
-		return fmt.Errorf("cannot declare the dead-letter queue: %w", err)
-	}
-	if err := m.post(ctx, "/api/bindings/%2f/e/"+url.PathEscape(DeadExchangeName)+
-		"/q/"+url.PathEscape(DeadExchangeName), map[string]string{"routing_key": "#"}); err != nil {
-		return fmt.Errorf("cannot bind the dead-letter queue: %w", err)
-	}
-	return nil
-}
-
-// CreateNodeAccount gives a node its own broker account, with the token's secret as the password.
-//
-// Scoped so a node can reach its own queue and the one exchange, and nothing else. The patterns
-// are anchored: a node called `laptop` must not be able to read `laptop-of-somebody-else`.
-func (m *Management) CreateNodeAccount(ctx context.Context, node, password string) error {
-	if !safeName.MatchString(node) {
-		return fmt.Errorf(
-			"%q cannot be a broker account name: it becomes part of a permission pattern, so it "+
-				"is lower-case letters, digits and dashes", node)
-	}
-
-	if err := m.put(ctx, "/api/users/"+url.PathEscape(node),
-		map[string]string{"password": password, "tags": ""}); err != nil {
-		return fmt.Errorf("cannot create the broker account for %s: %w", node, err)
-	}
-
-	queue := regexp.QuoteMeta(QueueFor(node))
-	if err := m.put(ctx, "/api/permissions/%2f/"+url.PathEscape(node), map[string]string{
-		"configure": "^" + queue + "$",
-		"write":     "^(" + regexp.QuoteMeta(ExchangeName) + "|" + queue + ")$",
-		"read":      "^" + queue + "$",
-	}); err != nil {
-		return fmt.Errorf("cannot scope the broker account for %s: %w", node, err)
-	}
-	return nil
-}
-
-// CreateBuilderAccount scopes an account to taking build work and answering it.
-//
-// **A build machine is not a node**, and giving it a node's account would let it read another
-// machine's declarations. What it needs is narrower and different: read the build queue, and
-// write to the exchange and to whatever temporary queue an asker is waiting on.
-//
-// The reply queues are the reason `write` is not simply the exchange. `RequestBuild` declares an
-// exclusive queue with a generated name and waits on it, so a builder that could not write to it
-// could take work and never answer — which is the failure that looks like a builder that is not
-// running.
-func (m *Management) CreateBuilderAccount(ctx context.Context, name, password string) error {
-	if !safeName.MatchString(name) {
-		return fmt.Errorf(
-			"%q cannot be a broker account name: it becomes part of a permission pattern, so it "+
-				"is lower-case letters, digits and dashes", name)
-	}
-
-	if err := m.put(ctx, "/api/users/"+url.PathEscape(name),
-		map[string]string{"password": password, "tags": ""}); err != nil {
-		return fmt.Errorf("cannot create the broker account for %s: %w", name, err)
-	}
-
-	builds := regexp.QuoteMeta(BuildQueueName)
-	if err := m.put(ctx, "/api/permissions/%2f/"+url.PathEscape(name), map[string]string{
-		// It declares the build queue, because whichever builder starts first must be able to —
-		// and a queue nobody may declare is a queue that exists only if the control plane has
-		// already run, which makes the order they start in matter.
-		"configure": "^" + builds + "$",
-		// Two exchanges, and nothing else. **Not the default exchange**: permission there is
-		// granted per exchange rather than per queue, so a builder allowed to use it could
-		// publish into any node's queue — the privilege a build machine most obviously should
-		// not have. Answers go through the node exchange; announcing what was built goes through
-		// the events exchange, which is a different act with a different audience (novox/hq
-		// ADR 0072). A builder that could answer and not announce would leave the module graph
-		// knowing less than the registry does.
-		"write": "^(" + regexp.QuoteMeta(ExchangeName) + "|" + regexp.QuoteMeta(EventsExchangeName) + ")$",
-		// The build queue and nothing else. Not another machine's declarations.
-		"read": "^" + builds + "$",
-	}); err != nil {
-		return fmt.Errorf("cannot scope the broker account for %s: %w", name, err)
-	}
-	return nil
-}
-
-// RemoveNodeAccount withdraws a node's access.
-func (m *Management) RemoveNodeAccount(ctx context.Context, node string) error {
-	if !safeName.MatchString(node) {
-		return fmt.Errorf("%q is not a broker account name", node)
-	}
-	return m.do(ctx, http.MethodDelete, "/api/users/"+url.PathEscape(node), nil)
-}
-
-// Accounts lists the broker's users, so a picture can be read from the system rather than assumed
-// (novox/hq ADR 0018).
-func (m *Management) Accounts(ctx context.Context) ([]string, error) {
-	body, err := m.get(ctx, "/api/users")
-	if err != nil {
-		return nil, err
-	}
-	var users []struct {
-		Name string `json:"name"`
-	}
-	if err := json.Unmarshal(body, &users); err != nil {
-		return nil, err
-	}
-	names := make([]string, 0, len(users))
-	for _, u := range users {
-		names = append(names, u.Name)
-	}
-	return names, nil
-}
-
-func (m *Management) put(ctx context.Context, path string, body any) error {
-	return m.do(ctx, http.MethodPut, path, body)
-}
-
-func (m *Management) post(ctx context.Context, path string, body any) error {
-	return m.do(ctx, http.MethodPost, path, body)
-}
-
-func (m *Management) get(ctx context.Context, path string) ([]byte, error) {
-	request, err := m.request(ctx, http.MethodGet, path, nil)
-	if err != nil {
-		return nil, err
-	}
-	response, err := m.client.Do(request)
-	if err != nil {
-		return nil, err
-	}
-	defer response.Body.Close()
-	if response.StatusCode >= 300 {
-		return nil, fmt.Errorf("the broker's management API answered %s to GET %s",
-			response.Status, path)
-	}
-	return io.ReadAll(io.LimitReader(response.Body, 1<<20))
-}
-
-func (m *Management) do(ctx context.Context, method, path string, body any) error {
-	request, err := m.request(ctx, method, path, body)
-	if err != nil {
-		return err
-	}
-	response, err := m.client.Do(request)
-	if err != nil {
-		return err
-	}
-	defer response.Body.Close()
-	if response.StatusCode >= 300 {
-		detail, _ := io.ReadAll(io.LimitReader(response.Body, 4096))
-		return fmt.Errorf("the broker's management API answered %s to %s %s: %s",
-			response.Status, method, path, strings.TrimSpace(string(detail)))
-	}
-	return nil
-}
-
-func (m *Management) request(ctx context.Context, method, path string, body any) (*http.Request, error) {
-	var payload io.Reader
-	if body != nil {
-		raw, err := json.Marshal(body)
-		if err != nil {
-			return nil, err
-		}
-		payload = bytes.NewReader(raw)
-	}
-
-	// Path joined by hand rather than through url.Parse: %2f is the default vhost and must reach
-	// the broker still encoded. Parsing would decode it to a slash and address a different route.
-	target := strings.TrimSuffix(m.base.String(), "/")
-	if user := m.base.User; user != nil {
-		target = strings.TrimSuffix(m.base.Scheme+"://"+m.base.Host, "/")
-	}
-	request, err := http.NewRequestWithContext(ctx, method, target+path, payload)
-	if err != nil {
-		return nil, err
-	}
-	if user := m.base.User; user != nil {
-		password, _ := user.Password()
-		request.SetBasicAuth(user.Username(), password)
-	}
-	if body != nil {
-		request.Header.Set("Content-Type", "application/json")
-	}
-	return request, nil
-}

internal/broker/module_account_test.go

@@ -1,96 +0,0 @@
-package broker_test
-
-import (
-	"context"
-	"encoding/json"
-	"net/http"
-	"net/http/httptest"
-	"regexp"
-	"strings"
-	"testing"
-
-	"github.com/novox/mesh-controller/internal/broker"
-)
-
-// The audit logger consumes everything and emits nothing. Its account must let it declare and read
-// its own queue and read the events exchange to bind onto — and must not reach another module's
-// queue, nor grant any write to the events exchange (novox/hq ADR 0043).
-func TestAConsumerReadsItsOwnQueueAndTheEventsExchangeAndNoOthers(t *testing.T) {
-	// Rebuilt through CreateModuleAccount's own path by asking for the same scope it would apply.
-	// The queue this module reads:
-	mine := broker.ModuleQueueFor("anchor", "audit-logger")
-	other := broker.ModuleQueueFor("anchor", "plex")
-
-	read := scope(t, "read", "anchor", "audit-logger", nil, []string{"#"})
-	if !read.MatchString(mine) {
-		t.Error("the audit logger may not read its own queue, so it consumes nothing")
-	}
-	if !read.MatchString(broker.EventsExchangeName) {
-		t.Error("the audit logger may not read the events exchange, so it cannot bind onto it")
-	}
-	if read.MatchString(other) {
-		t.Error("the audit logger may read another module's queue")
-	}
-
-	// It emits nothing, so it is granted no write to the events exchange — only its own queue, to bind.
-	write := scope(t, "write", "anchor", "audit-logger", nil, []string{"#"})
-	if write.MatchString(broker.EventsExchangeName) {
-		t.Error("a pure consumer was granted write to the events exchange")
-	}
-	if !write.MatchString(mine) {
-		t.Error("the audit logger may not write to its own queue, so it cannot bind it")
-	}
-}
-
-// An emitter is granted the events exchange to write; a consumer is not.
-func TestAnEmitterMayWriteTheEventsExchangeAndAConsumerMayNot(t *testing.T) {
-	emitter := scope(t, "write", "anchor", "umami", []string{"module.umami.site.created"}, nil)
-	if !emitter.MatchString(broker.EventsExchangeName) {
-		t.Error("an emitting module may not write the events exchange, so it cannot emit")
-	}
-}
-
-// scope reconstructs one of the three permission patterns CreateModuleAccount would apply, by
-// reading it back from a captured request against a stub management API.
-func scope(t *testing.T, which, node, module string, emits, consumes []string) *regexp.Regexp {
-	t.Helper()
-	pat := capturePermission(t, which, node, module, emits, consumes)
-	re, err := regexp.Compile(pat)
-	if err != nil {
-		t.Fatalf("the %s pattern does not compile: %v", which, err)
-	}
-	return re
-}
-
-// capturePermission runs CreateModuleAccount against a stub management API and returns the pattern
-// it set for `which` ("configure"/"write"/"read"). The scope is tested where it is applied, not
-// reconstructed by the test — so a change to the mapping cannot pass a test that hard-codes the old
-// one.
-func capturePermission(t *testing.T, which, node, module string, emits, consumes []string) string {
-	t.Helper()
-	var captured map[string]string
-	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
-		if strings.HasPrefix(r.URL.Path, "/api/permissions/") {
-			_ = json.NewDecoder(r.Body).Decode(&captured)
-		}
-		w.WriteHeader(http.StatusNoContent)
-	}))
-	defer server.Close()
-
-	t.Setenv(broker.ManagementVar, server.URL)
-	m, err := broker.ManagementFromEnvironment()
-	if err != nil {
-		t.Fatalf("stub management not usable: %v", err)
-	}
-	if _, err := m.CreateModuleAccount(context.Background(), node, module, "pw", emits, consumes); err != nil {
-		t.Fatalf("CreateModuleAccount: %v", err)
-	}
-	if captured == nil {
-		t.Fatal("no permissions were set")
-	}
-	pattern, ok := captured[which]
-	if !ok {
-		t.Fatalf("no %s permission was set; got %v", which, captured)
-	}
-	return pattern
-}

internal/broker/onnats.go

@@ -68,24 +68,16 @@ func BareAddress(address string) string {
 	return "nats://" + bare
 }
 
-// MustBeOneBus refuses a configuration that names both buses for the mesh's own traffic.
-//
-// **Both clients ship and that is the point; both being live is not.** The rollout moves every node
-// at once (ADR 0116 step 5): a mesh half on each is one where a declaration goes out on one bus and
-// the report comes back on the other, and nothing anywhere says so — every component would log
-// success. Refused at start, where it can be said in one sentence.
-func MustBeOneBus(amqp, nats string) error {
-	if strings.TrimSpace(amqp) != "" && strings.TrimSpace(nats) != "" {
-		return fmt.Errorf(
-			"this control plane is told about both buses (%s and %s) and can only be on one. A mesh "+
-				"half on each is one where a declaration goes out on one and the report comes back "+
-				"on the other, and every component reports success while it happens. The rollout "+
-				"moves every node at once: unset %s to stay, or unset %s to move",
-			AMQPVarName, NATSVar, NATSVar, AMQPVarName)
+// BusAddress is where the mesh's bus is, with this process's credential, and refuses to be empty:
+// there is one bus, and a control plane without it can hold records and answer nothing (novox/hq
+// ADR 0131, design 28 task 5.5).
+func BusAddress() (string, error) {
+	address, _, err := OnNATS()
+	if err != nil {
+		return "", err
 	}
-	return nil
+	if address == "" {
+		return "", fmt.Errorf("this control plane has no %s, so it cannot reach the mesh's bus", NATSVar)
+	}
+	return address, nil
 }
-
-// AMQPVarName is the variable naming the bus the mesh runs on today. Named here rather than
-// imported from the link package, for the one direction of dependency.
-const AMQPVarName = "MESH_BROKER_AMQP"

internal/broker/onnats_test.go

@@ -1,43 +1,11 @@
 package broker
 
 import (
-	"strings"
 	"testing"
 )
 
 // Which bus the mesh is on is one fact, and being told about both is refused.
 //
-// **Not a warning.** A mesh half on each bus is one where a declaration goes out on one and the
-// report comes back on the other, and every component reports success while it happens — which is
-// the exact failure ADR 0074 exists to catch, arriving through configuration instead of through code.
-func TestBeingToldAboutBothBusesIsRefused(t *testing.T) {
-	err := MustBeOneBus("amqps://broker:5671/", "nats://bus:4222")
-	if err == nil {
-		t.Fatal("a control plane told about both buses was allowed to start")
-	}
-	// The remedy is in the words, because whoever reads this has to choose one and the wrong choice
-	// is a rollout half done.
-	for _, want := range []string{AMQPVarName, NATSVar, "unset"} {
-		if !strings.Contains(err.Error(), want) {
-			t.Errorf("the refusal does not mention %s: %v", want, err)
-		}
-	}
-}
-
-// One bus, or none, is ordinary. None is a control plane that publishes nothing and holds records,
-// which several of its own commands are.
-func TestOneBusOrNeitherIsAllowed(t *testing.T) {
-	for _, c := range []struct{ what, amqp, nats string }{
-		{"the bus the mesh runs on today", "amqps://broker:5671/", ""},
-		{"the bus being built", "", "nats://bus:4222"},
-		{"neither", "", ""},
-		{"neither, with whitespace for an address", "  ", "\t"},
-	} {
-		if err := MustBeOneBus(c.amqp, c.nats); err != nil {
-			t.Errorf("%s was refused: %v", c.what, err)
-		}
-	}
-}
 
 // The controller's own credential arrives in its address, and has to be readable out of it — its user
 // is created by the installer at a bootstrap password, before the controller exists to mint one.

internal/broker/streams.go

@@ -175,6 +175,9 @@ var ControllerFollows = []string{
 	// message on the control branch. Same three audiences, one publish: whoever asked, this, and the
 	// catalogue.
 	seatEventSubject("mesh-build-machine", "built"),
+	// The forge's merges: what moved a source, so the mesh builds what that source produces
+	// without anybody telling it (novox/hq 04-ISSUES/131). Appended, because the index is a name.
+	moduleEventSubject("gitea", "pull.merged"),
 }
 
 // moduleEventSubject is where one module's event lands. The same derivation PermissionsFor uses, so

internal/broker/testdata/composed.conf

@@ -25,7 +25,7 @@ accounts {
     users = [
       { user: "controller", password: "$2a$11$cccccccccccccccccccccc", permissions: {
         publish: { allow: ["$JS.ACK.CONTROL.controller.>", "$JS.ACK.EVENTS.controller.>", "$JS.API.>", "_INBOX.enrol.>", "mesh.control.>", "mesh.node.>", "mesh.seat.mesh-build-machine.accept.>"] }
-        subscribe: { allow: ["$JS.API.>", "_DELIVER.controller", "_DELIVER.controller.>", "_INBOX.controller.>", "mesh.control.>", "mesh.mod.mesh-catalog.event.catching-up", "mesh.mod.mesh-catalog.event.upgraded", "mesh.seat.mesh-build-machine.event.built"] }
+        subscribe: { allow: ["$JS.API.>", "_DELIVER.controller", "_DELIVER.controller.>", "_INBOX.controller.>", "mesh.control.>", "mesh.mod.gitea.event.pull.merged", "mesh.mod.mesh-catalog.event.catching-up", "mesh.mod.mesh-catalog.event.upgraded", "mesh.seat.mesh-build-machine.event.built"] }
         allow_responses: { max: 1, ttl: "1m" }
       } }
       { user: "enrol.one", password: "$2a$11$eeeeeeeeeeeeeeeeeeeeee", permissions: {

internal/builder/builder.go

@@ -169,6 +169,8 @@ func Build(ctx context.Context, run Runner, publish Publisher,
 	}
 
 	var built []catalogue.Built
+	// stoodOn is every base the build was handed, as resolved — the edges the catalogue derives.
+	var stoodOn []string
 	if manifest.Build != nil {
 		// What this module said it stands on, answered with what this mesh actually holds. Done
 		// before anything is built, so a missing base is refused in front of the person who can
@@ -186,11 +188,12 @@ func Build(ctx context.Context, run Runner, publish Publisher,
 			}
 			return from, nil
 		}
-		args, err := standingOn(ctx, manifest, held, mirror)
+		args, bases, err := standingOn(ctx, manifest, held, mirror)
 		if err != nil {
 			say("bases", "UNMET: %v", err)
 			return Result{}, err
 		}
+		stoodOn = bases
 		if len(args) > 0 {
 			say("bases", "%d resolved from what the mesh holds", len(args)/2)
 		}
@@ -217,7 +220,7 @@ func Build(ctx context.Context, run Runner, publish Publisher,
 	}
 	say("done", "%s at %s — %d artifact(s) pinned", manifest.Module, short(commit), len(built))
 	return Result{Manifest: resolved, Commit: commit, Built: built,
-		Against: against(within, manifest)}, nil
+		Against: against(within, manifest, stoodOn)}, nil
 }
 
 // Log is where a build says what it is doing, step by step. Nil is silent — the tests pass none,
@@ -339,14 +342,27 @@ func describe(path string) string {
 // allowed to name — a tag is something somebody else can move under you.
 var pinnedImage = regexp.MustCompile(`[A-Za-z0-9][A-Za-z0-9._/:-]*@sha256:[0-9a-f]{64}`)
 
-// against reads what this module's image artifacts are built on top of, out of the files that
-// build them. Nothing is guessed: a reference that is not written down is not reported.
-func against(within string, manifest catalogue.Manifest) []string {
+// against is what this module's image artifacts are built on top of: every base the mesh resolved
+// and handed the recipe as a build argument (`build.on`), and any image a recipe pins by digest
+// itself. Nothing is guessed: a reference that was neither resolved nor written down is not
+// reported.
+//
+// **The resolved bases are the edges.** A recipe reads its base from an argument (`FROM
+// ${RUNTIME_BASE}`), so the digest is never in the file, and a derivation that read files alone
+// recorded no edge for any module on the mesh — which is why nothing knew what a changed base
+// meant to rebuild (novox/hq 04-ISSUES/131).
+func against(within string, manifest catalogue.Manifest, resolved []string) []string {
 	if manifest.Build == nil {
 		return nil
 	}
 	seen := map[string]bool{}
 	var out []string
+	for _, r := range resolved {
+		if r != "" && !seen[r] {
+			seen[r] = true
+			out = append(out, r)
+		}
+	}
 	for _, a := range manifest.Build.Artifacts {
 		if a.Kind != catalogue.ArtifactImage || a.From == "" {
 			continue
@@ -704,40 +720,42 @@ var _ io.Writer = (*stringWriter)(nil)
 // built cannot be built here yet, and the useful sentence names which module is missing — not the
 // one a container runtime produces when a recipe's first line refers to an image nobody has.
 //
-// The order is fixed so two builds of one commit invoke the same command.
+// The order is fixed so two builds of one commit invoke the same command. Returned alongside the
+// arguments is every reference they resolved to, which is what the build stood on.
 func standingOn(ctx context.Context, manifest catalogue.Manifest, held map[string]string,
-	mirror func(ctx context.Context, from, repository string) (string, error)) ([]string, error) {
+	mirror func(ctx context.Context, from, repository string) (string, error)) ([]string, []string, error) {
 	if manifest.Build == nil || len(manifest.Build.On) == 0 {
-		return nil, nil
+		return nil, nil, nil
 	}
 	on := append([]catalogue.BuildsOn{}, manifest.Build.On...)
 	sort.Slice(on, func(i, j int) bool { return on[i].Arg < on[j].Arg })
 
-	var args []string
+	var args, resolved []string
 	for _, base := range on {
 		if base.Image != "" {
 			// A vendor's image, declared (novox/hq 04-ISSUES/064, ADR 0097). Pinned, because a tag
 			// is what somebody else can move; copied into the mesh's registry, because a build
 			// that reaches a public registry on its own is a build that works sometimes.
 			if base.Arg == "" || base.Module != "" || base.Artifact != "" {
-				return nil, fmt.Errorf(
+				return nil, nil, fmt.Errorf(
 					"%s stands on the image %s, and a base is either a module's artifact or an "+
 						"image — never both — read from one build argument", manifest.Module, base.Image)
 			}
 			if !strings.Contains(base.Image, "@sha256:") {
-				return nil, fmt.Errorf(
+				return nil, nil, fmt.Errorf(
 					"%s stands on the image %q, which is not pinned by digest. A tag is what "+
 						"somebody else can move; name it as <image>@sha256:…", manifest.Module, base.Image)
 			}
 			reference, err := mirror(ctx, base.Image, manifest.Module+"/on-"+strings.ToLower(base.Arg))
 			if err != nil {
-				return nil, fmt.Errorf("%s stands on %s: %w", manifest.Module, base.Image, err)
+				return nil, nil, fmt.Errorf("%s stands on %s: %w", manifest.Module, base.Image, err)
 			}
 			args = append(args, "--build-arg", base.Arg+"="+reference)
+			resolved = append(resolved, reference)
 			continue
 		}
 		if base.Arg == "" || base.Module == "" || base.Artifact == "" {
-			return nil, fmt.Errorf(
+			return nil, nil, fmt.Errorf(
 				"%s says its build stands on something, and does not say all of what: a base "+
 					"needs the module, the artifact, and the build argument the recipe reads it "+
 					"from", manifest.Module)
@@ -745,14 +763,15 @@ func standingOn(ctx context.Context, manifest catalogue.Manifest, held map[strin
 		key := base.Module + "/" + base.Artifact
 		reference, has := held[key]
 		if !has {
-			return nil, fmt.Errorf(
+			return nil, nil, fmt.Errorf(
 				"%s builds on %s, and this mesh has not built it. Build %s first — every module "+
 					"in this toolchain stands on it, so it is the thing to have before anything "+
 					"else", manifest.Module, key, base.Module)
 		}
 		args = append(args, "--build-arg", base.Arg+"="+reference)
+		resolved = append(resolved, reference)
 	}
-	return args, nil
+	return args, resolved, nil
 }
 
 // compile runs a module's own code through its toolchain, and says where the result is.

internal/builder/standing_on_test.go

@@ -22,7 +22,7 @@ func TestABaseTheMeshHasNotBuiltIsRefused(t *testing.T) {
 			On: []catalogue.BuildsOn{{Arg: "RUNTIME_BASE", Module: "mesh-tools", Artifact: "runtime"}},
 		},
 	}
-	_, err := standingOn(context.Background(), manifest, map[string]string{}, noMirror)
+	_, _, err := standingOn(context.Background(), manifest, map[string]string{}, noMirror)
 	if err == nil {
 		t.Fatal("a base nothing has built was accepted; the build would have failed on its first line")
 	}
@@ -42,7 +42,7 @@ func TestABaseTheMeshHoldsBecomesABuildArgument(t *testing.T) {
 		},
 	}
 	held := map[string]string{"mesh-tools/runtime": "127.0.0.1:5000/mesh-tools/runtime@sha256:" + strings.Repeat("a", 64)}
-	args, err := standingOn(context.Background(), manifest, held, noMirror)
+	args, _, err := standingOn(context.Background(), manifest, held, noMirror)
 	if err != nil {
 		t.Fatalf("a base this mesh holds was refused: %v", err)
 	}
@@ -54,7 +54,7 @@ func TestABaseTheMeshHoldsBecomesABuildArgument(t *testing.T) {
 
 // A module naming no base asks for nothing, which is most modules.
 func TestAModuleNamingNoBaseAddsNoArguments(t *testing.T) {
-	args, err := standingOn(context.Background(), catalogue.Manifest{Module: "hello-web", Build: &catalogue.Build{}}, nil, noMirror)
+	args, _, err := standingOn(context.Background(), catalogue.Manifest{Module: "hello-web", Build: &catalogue.Build{}}, nil, noMirror)
 	if err != nil || args != nil {
 		t.Fatalf("a module naming no base produced %v, %v", args, err)
 	}
@@ -66,7 +66,7 @@ func TestAnIncompleteBaseIsRefused(t *testing.T) {
 		Module: "postgres",
 		Build:  &catalogue.Build{On: []catalogue.BuildsOn{{Module: "mesh-tools", Artifact: "runtime"}}},
 	}
-	if _, err := standingOn(context.Background(), manifest, map[string]string{"mesh-tools/runtime": "x"}, noMirror); err == nil {
+	if _, _, err := standingOn(context.Background(), manifest, map[string]string{"mesh-tools/runtime": "x"}, noMirror); err == nil {
 		t.Fatal("a base with no build argument was accepted; nothing would have read it")
 	}
 }
@@ -86,7 +86,7 @@ func TestADeclaredVendorImageIsCopiedInAndHandedToTheRecipe(t *testing.T) {
 		},
 	}
 	var asked []string
-	args, err := standingOn(context.Background(), manifest, nil, func(_ context.Context, from, repository string) (string, error) {
+	args, _, err := standingOn(context.Background(), manifest, nil, func(_ context.Context, from, repository string) (string, error) {
 		asked = append(asked, from+" -> "+repository)
 		return "127.0.0.1:5000/" + repository + "@sha256:" + strings.Repeat("d", 64), nil
 	})
@@ -101,7 +101,7 @@ func TestADeclaredVendorImageIsCopiedInAndHandedToTheRecipe(t *testing.T) {
 	}
 	// Unpinned, it is refused: a tag is what somebody else can move.
 	manifest.Build.On[0].Image = "quay.io/minio/mc:latest"
-	if _, err := standingOn(context.Background(), manifest, nil, noMirror); err == nil || !strings.Contains(err.Error(), "not pinned") {
+	if _, _, err := standingOn(context.Background(), manifest, nil, noMirror); err == nil || !strings.Contains(err.Error(), "not pinned") {
 		t.Fatalf("an unpinned vendor image was accepted: %v", err)
 	}
 }
@@ -151,3 +151,31 @@ func TestARecipeIsReadAsInstructions(t *testing.T) {
 		t.Fatalf("a heredoc line or a continued stage was read as a base: %v", bases)
 	}
 }
+
+// What a build was handed as its bases is what it stood on — recorded, so a changed base knows what
+// to rebuild (novox/hq 04-ISSUES/131). A recipe reads the base from an argument, so nothing else
+// could know.
+func TestTheBasesABuildWasHandedAreWhatItStoodOn(t *testing.T) {
+	manifest := catalogue.Manifest{
+		Module: "gitea",
+		Build: &catalogue.Build{
+			On: []catalogue.BuildsOn{
+				{Arg: "RUNTIME_BASE", Module: "mesh-tools", Artifact: "runtime"},
+				{Arg: "BUILD_BASE", Module: "mesh-tools", Artifact: "build"},
+			},
+			Artifacts: []catalogue.Artifact{{Name: "runtime", Kind: catalogue.ArtifactImage, From: "Dockerfile"}},
+		},
+	}
+	held := map[string]string{
+		"mesh-tools/runtime": "127.0.0.1:5000/mesh-tools/runtime@sha256:" + strings.Repeat("a", 64),
+		"mesh-tools/build":   "127.0.0.1:5000/mesh-tools/build@sha256:" + strings.Repeat("b", 64),
+	}
+	_, resolved, err := standingOn(context.Background(), manifest, held, noMirror)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := against(t.TempDir(), manifest, resolved)
+	if len(got) != 2 || got[0] != held["mesh-tools/build"] || got[1] != held["mesh-tools/runtime"] {
+		t.Fatalf("the bases the build was handed were not what it stood on: %v", got)
+	}
+}

internal/inventory/builds.go

@@ -164,6 +164,41 @@ func (i *Inventory) Held(ctx context.Context) (map[string]string, error) {
 	return held, rows.Err()
 }
 
+// BuiltAgainst is what each module's newest successful build stood on, as recorded — the build
+// edges (ADR 0009). A module whose last build recorded no bases is absent, which is also what a
+// module standing on nothing looks like: an edge the mesh has not derived is not an edge.
+func (i *Inventory) BuiltAgainst(ctx context.Context) (map[string][]string, error) {
+	rows, err := i.store.Pool().Query(ctx,
+		`select distinct on (module) module, built_against
+		   from build
+		  where module is not null and module <> '' and failed = ''
+		  order by module, at desc`)
+	if err != nil {
+		return nil, err
+	}
+	defer rows.Close()
+
+	against := map[string][]string{}
+	for rows.Next() {
+		var module string
+		var raw []byte
+		if err := rows.Scan(&module, &raw); err != nil {
+			return nil, err
+		}
+		if len(raw) == 0 {
+			continue
+		}
+		var refs []string
+		if err := json.Unmarshal(raw, &refs); err != nil {
+			continue
+		}
+		if len(refs) > 0 {
+			against[module] = refs
+		}
+	}
+	return against, rows.Err()
+}
+
 // manifestOrNil keeps the difference between "declared nothing" and "predates this being kept".
 //
 // A build recorded before the mesh kept manifests has no manifest, and that is not the same as one

internal/link/ask.go

@@ -3,16 +3,13 @@ package link
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"time"
 
-	amqp "github.com/rabbitmq/amqp091-go"
+	"github.com/nats-io/nats.go"
 )
 
-// RPCExchange is where a module's tools are asked over the broker, keyed `<module>.<tool>`, and
-// where the answer comes back, keyed by the asker's reply queue (novox/hq ADR 0047).
-const RPCExchange = "mesh.rpc"
-
 // Answer is what a module's tool replies: one of the two, never both.
 type Answer struct {
 	Result json.RawMessage `json:"result,omitempty"`
@@ -27,70 +24,35 @@ type Answer struct {
 // grants, and should not. The control plane already holds a connection that may, so a person or
 // an agent asks through it, and every question passes one process where an audit belongs.
 //
-// The reply queue is the caller's own, server-named and exclusive, bound to the RPC exchange under
-// its own name: a serving module answers through that exchange and never the default one, whose
-// permission is per exchange rather than per queue. The correlation is checked rather than
-// assumed, as every RPC here is.
-func Ask(ctx context.Context, channel *amqp.Channel, module, tool string, args json.RawMessage,
+// The answer comes back on the asker's own inbox, which only the asker may read; the serving
+// module answers there and nowhere else. The bus refuses a request nothing serves at once, so a
+// module that is down or a tool that does not exist is said now rather than after the whole wait.
+func Ask(ctx context.Context, bus Bus, module, tool string, args json.RawMessage,
 	timeout time.Duration) (Answer, error) {
 
 	if len(args) == 0 {
 		args = json.RawMessage(`{}`)
 	}
-	replies, err := channel.QueueDeclare("", false, true, true, false, nil)
-	if err != nil {
-		return Answer{}, err
-	}
-	if err := channel.QueueBind(replies.Name, replies.Name, RPCExchange, false, nil); err != nil {
-		return Answer{}, fmt.Errorf("cannot bind a reply queue to %s: %w", RPCExchange, err)
-	}
-	answers, err := channel.ConsumeWithContext(ctx, replies.Name, "", true, true, false, false, nil)
-	if err != nil {
-		return Answer{}, err
-	}
-
-	// Mandatory, so a request nothing consumes comes straight back: a module that is down, or a
-	// tool that does not exist, is said at once rather than after the whole wait.
-	returned := channel.NotifyReturn(make(chan amqp.Return, 1))
-	id := fmt.Sprintf("ask-%d", time.Now().UnixNano())
 	key := module + "." + tool
-	if err := channel.PublishWithContext(ctx, RPCExchange, key, true, false, amqp.Publishing{
-		ContentType:   "application/json",
-		CorrelationId: id,
-		ReplyTo:       replies.Name,
-		Body:          args,
-	}); err != nil {
-		return Answer{}, fmt.Errorf("cannot ask %s: %w", key, err)
-	}
-
-	waiting, cancel := context.WithTimeout(ctx, timeout)
-	defer cancel()
-	for {
-		select {
-		case back := <-returned:
-			if back.CorrelationId == id {
+	reply, err := bus.AskTool(ctx, module, tool, args, timeout)
+	if err != nil {
+		if errors.Is(err, nats.ErrNoResponders) {
 			return Answer{}, fmt.Errorf(
-					"nothing serves %s: no runtime has bound %q on the broker. The module is not "+
-						"assigned, its runtime is not up, or it serves no such tool — `status` "+
-						"says whether the machine carrying it has applied", module, key)
+				"nothing serves %s: no runtime has bound %q on the bus. The module is not "+
+					"assigned, its runtime is not up, or it serves no such tool — `status` says "+
+					"whether the machine carrying it has applied", module, key)
 		}
-		case <-waiting.Done():
+		if errors.Is(err, context.DeadlineExceeded) || errors.Is(err, nats.ErrTimeout) {
 			return Answer{}, fmt.Errorf(
 				"%s did not answer within %s. Its runtime serves %q when it is up and has bound "+
-					"the broker — `status` says whether the machine carrying it has applied",
+					"the bus — `status` says whether the machine carrying it has applied",
 				module, timeout, key)
-		case delivery, ok := <-answers:
-			if !ok {
-				return Answer{}, fmt.Errorf("the connection closed while waiting for %s", key)
 		}
-			if delivery.CorrelationId != id {
-				continue
+		return Answer{}, fmt.Errorf("cannot ask %s: %w", key, err)
 	}
 	var answer Answer
-			if err := json.Unmarshal(delivery.Body, &answer); err != nil {
+	if err := json.Unmarshal(reply, &answer); err != nil {
 		return Answer{}, fmt.Errorf("%s answered with something unreadable: %w", key, err)
 	}
 	return answer, nil
 }
-	}
-}

internal/link/build.go

@@ -1,12 +1,7 @@
 package link
 
 import (
-	"context"
 	"encoding/json"
-	"fmt"
-	"time"
-
-	amqp "github.com/rabbitmq/amqp091-go"
 )
 
 // Asking a machine to build a module, and hearing what came out.
@@ -22,21 +17,6 @@ import (
 // holds no opinion about what they contain, and a host that also built things would be a host
 // with a container runtime requirement and a git dependency (novox/hq ADR 0005).
 
-// BuildQueue is where build requests wait. One queue, so several build machines can share the
-// work and each request is done exactly once — which is what a queue is for and what a
-// per-machine routing key would not give.
-const BuildQueue = "builds"
-
-// KeyBuilt is what a builder publishes when it has finished, successfully or not.
-const KeyBuilt = "built"
-
-// ReplyQueue is where the answer to one request goes.
-//
-// **Named here rather than left to the broker**, so it can be scoped and reasoned about. A broker
-// generates its own name for an unnamed queue, and a builder permitted to write to whatever that
-// convention happens to produce works on one broker and silently cannot answer on another.
-func ReplyQueue(id string) string { return BuildQueue + ".reply." + id }
-
 // BuildRequest is one module to build.
 type BuildRequest struct {
 	// ID correlates the answer with the asking. Not the module name: two builds of one module can
@@ -118,77 +98,3 @@ type MadeArtifact struct {
 	Kind      string `json:"kind"`
 	Reference string `json:"reference"`
 }
-
-// RequestBuild asks for a module to be built and waits for the answer.
-//
-// Waiting rather than returning immediately, because the thing a person wants after asking for a
-// build is to know whether it worked. A build that is dispatched and forgotten needs somewhere to
-// look afterwards, and there is nowhere yet.
-func RequestBuild(ctx context.Context, channel *amqp.Channel, request BuildRequest,
-	timeout time.Duration) (BuildResult, error) {
-
-	// Its own queue for the answer, declared before the ask. Consuming from the shared exchange
-	// would mean competing with the control plane's own consumer for a message meant for this
-	// caller — which is the fault this package's own doc comment records having had.
-	replies, err := channel.QueueDeclare(ReplyQueue(request.ID), false, true, true, false, nil)
-	if err != nil {
-		return BuildResult{}, err
-	}
-	// Bound to the exchange, and the answer comes back through it.
-	//
-	// **A builder never publishes to the default exchange**, because permission there is per
-	// exchange and not per queue — a builder allowed to use it could publish into any node's
-	// queue, which is the privilege a build machine most obviously should not have. Found by
-	// running it: the builder built, could not answer, and the connection closed saying only
-	// "not allowed to publish to exchange ''".
-	//
-	// The cost is that every asker sees every result, which is why the correlation is checked
-	// below rather than assumed.
-	if err := channel.QueueBind(replies.Name, KeyBuilt, Exchange, false, nil); err != nil {
-		return BuildResult{}, err
-	}
-	answers, err := channel.ConsumeWithContext(ctx, replies.Name, "", true, true, false, false, nil)
-	if err != nil {
-		return BuildResult{}, err
-	}
-
-	body, err := json.Marshal(request)
-	if err != nil {
-		return BuildResult{}, err
-	}
-	if err := channel.PublishWithContext(ctx, "", BuildQueue, false, false, amqp.Publishing{
-		ContentType:   "application/json",
-		DeliveryMode:  amqp.Persistent,
-		CorrelationId: request.ID,
-		ReplyTo:       replies.Name,
-		Body:          body,
-	}); err != nil {
-		return BuildResult{}, err
-	}
-
-	waiting, cancel := context.WithTimeout(ctx, timeout)
-	defer cancel()
-	for {
-		select {
-		case <-waiting.Done():
-			return BuildResult{}, fmt.Errorf(
-				"no builder answered within %s. Something must be consuming %q, and nothing is "+
-					"— or it is building something that takes longer than this",
-				timeout, BuildQueue)
-		case delivery, ok := <-answers:
-			if !ok {
-				return BuildResult{}, fmt.Errorf("the connection closed while waiting for a build")
-			}
-			var result BuildResult
-			if err := json.Unmarshal(delivery.Body, &result); err != nil {
-				return BuildResult{}, fmt.Errorf("a builder answered with something unreadable: %w", err)
-			}
-			if result.ID != request.ID {
-				// Somebody else's answer on this queue. Ignored rather than returned, because
-				// returning it would attribute one build's outcome to another's.
-				continue
-			}
-			return result, nil
-		}
-	}
-}

internal/link/builds_current.go

@@ -1,202 +0,0 @@
-package link
-
-import (
-	"context"
-	"encoding/json"
-	"errors"
-	"fmt"
-	"time"
-
-	amqp "github.com/rabbitmq/amqp091-go"
-)
-
-// The build flow on the bus the mesh runs on today.
-//
-// Moved behind the seam rather than changed. The queue, the reply binding and the correlation are
-// what they were, because the mesh is running on this.
-
-// currentBuilds asks for builds over a channel.
-type currentBuilds struct{ channel *amqp.Channel }
-
-// BuildsOverCurrent is the asking side on the bus the mesh has.
-func BuildsOverCurrent(channel *amqp.Channel) Builders { return currentBuilds{channel: channel} }
-
-func (b currentBuilds) Close() {}
-
-func (b currentBuilds) Submit(ctx context.Context, request BuildRequest,
-	wait time.Duration) (BuildResult, error) {
-
-	// Its own queue for the answer, declared before the ask. Consuming from the shared exchange
-	// would mean competing with the controller's own consumer for a message meant for this caller.
-	replies, err := b.channel.QueueDeclare(ReplyQueue(request.ID), false, true, true, false, nil)
-	if err != nil {
-		return BuildResult{}, err
-	}
-	// **A builder never publishes to the default exchange**, because permission there is per
-	// exchange and not per queue — a builder allowed to use it could publish into any node's queue,
-	// which is the privilege a build machine most obviously should not have. The cost is that every
-	// asker sees every result, which is why the correlation is checked below rather than assumed.
-	if err := b.channel.QueueBind(replies.Name, KeyBuilt, Exchange, false, nil); err != nil {
-		return BuildResult{}, err
-	}
-	answers, err := b.channel.ConsumeWithContext(ctx, replies.Name, "", true, true, false, false, nil)
-	if err != nil {
-		return BuildResult{}, err
-	}
-
-	body, err := json.Marshal(request)
-	if err != nil {
-		return BuildResult{}, err
-	}
-	if err := b.channel.PublishWithContext(ctx, "", BuildQueue, false, false, amqp.Publishing{
-		ContentType:   "application/json",
-		DeliveryMode:  amqp.Persistent,
-		CorrelationId: request.ID,
-		ReplyTo:       replies.Name,
-		Body:          body,
-	}); err != nil {
-		return BuildResult{}, err
-	}
-
-	waiting, cancel := context.WithTimeout(ctx, wait)
-	defer cancel()
-	for {
-		select {
-		case <-waiting.Done():
-			return BuildResult{}, waitingFor(wait)
-		case delivery, ok := <-answers:
-			if !ok {
-				return BuildResult{}, errors.New("the connection closed while waiting for a build")
-			}
-			result, mine, err := theOutcomeOf(delivery.Body, request.ID)
-			if err != nil {
-				return BuildResult{}, err
-			}
-			if mine {
-				return result, nil
-			}
-		}
-	}
-}
-
-// --- the machine's side ---------------------------------------------------------------------
-
-type currentMachine struct {
-	conn    *amqp.Connection
-	channel *amqp.Channel
-	on      string
-}
-
-// MachineOverCurrent takes build work over a channel.
-func MachineOverCurrent(conn *amqp.Connection, channel *amqp.Channel, on string) BuildMachine {
-	return &currentMachine{conn: conn, channel: channel, on: on}
-}
-
-func (m *currentMachine) Close() {}
-
-func (m *currentMachine) Take(ctx context.Context, do func(context.Context, Build)) error {
-	if _, err := m.channel.QueueDeclare(BuildQueue, true, false, false, false, nil); err != nil {
-		return err
-	}
-	// One at a time. A machine that took five requests at once would run five container builds
-	// against one runtime and finish all of them slower than it would have finished the first — and
-	// the queue is what shares work between machines, so nothing is lost by it.
-	if err := m.channel.Qos(1, 0, false); err != nil {
-		return err
-	}
-	// Not auto-acknowledged: a request acknowledged on arrival is a build that vanishes if this
-	// process dies mid-way, with nobody waiting on it ever hearing why.
-	requests, err := m.channel.ConsumeWithContext(ctx, BuildQueue, "mesh-builder",
-		false, false, false, false, nil)
-	if err != nil {
-		return err
-	}
-	for {
-		select {
-		case <-ctx.Done():
-			return nil
-		case delivery, ok := <-requests:
-			if !ok {
-				return errors.New("the broker closed the connection")
-			}
-			var request BuildRequest
-			if err := json.Unmarshal(delivery.Body, &request); err != nil {
-				// Unreadable: rejected rather than retried, because the next attempt reads the same
-				// bytes. Nobody waiting hears an answer, which is correct — there was no request.
-				_ = delivery.Reject(false)
-				continue
-			}
-			do(ctx, &currentBuild{request: request, delivery: delivery, on: m.on, channel: m.channel})
-		}
-	}
-}
-
-type currentBuild struct {
-	request  BuildRequest
-	delivery amqp.Delivery
-	on       string
-	channel  *amqp.Channel
-}
-
-func (b *currentBuild) Request() BuildRequest { return b.request }
-
-// Announce answers and announces, which on this bus are two publishes to two exchanges.
-//
-// The reply goes to whoever asked, correlated to their request; the announcement says to the whole
-// mesh that a module now exists at a commit (novox/hq ADR 0072). Only a successful build is
-// announced: a failed one produced no module version, and announcing one would put something in the
-// graph that was never made.
-func (b *currentBuild) Announce(ctx context.Context, result BuildResult) error {
-	body, err := json.Marshal(result)
-	if err != nil {
-		return err
-	}
-	if err := b.channel.PublishWithContext(ctx, Exchange, KeyBuilt, false, false, amqp.Publishing{
-		ContentType:   "application/json",
-		CorrelationId: result.ID,
-		Body:          body,
-	}); err != nil {
-		return fmt.Errorf("cannot answer a build request: %w", err)
-	}
-	if result.Failed != "" || result.Commit == "" {
-		return nil
-	}
-
-	// **Announced under both names on this bus, for exactly as long as this bus lives.**
-	//
-	// A build's outcome belongs to the role now (novox/hq ADR 0121), so a catalogue built from the
-	// current manifests listens for the role's name. A catalogue that is *already running* listens for
-	// the module's, because that is what it was told when it was installed. A rename on a live bus
-	// needs the publisher and the subscriber to change together, and a merge cannot promise that: one
-	// of them is deployed first, and in that window the graph silently stops being updated — which is
-	// the failure this whole change was cleaning up after.
-	//
-	// So both, and the order stops mattering. The module's own name goes with the bus, in step 5's
-	// retirement list; nothing has ever run on the bus being built, so there is no legacy name there
-	// and this doubling has no counterpart.
-	announced := announcementOf(result)
-	if err := EmitEvent(ctx, OverCurrent{Channel: b.channel}, KeyModuleBuilt, "builder", b.on,
-		announced); err != nil {
-		return err
-	}
-	return EmitEvent(ctx, OverCurrent{Channel: b.channel}, KeyRoleBuilt, TheBuildMachine, b.on,
-		announced)
-}
-
-func (b *currentBuild) Done() error { return b.delivery.Ack(false) }
-
-func (b *currentBuild) Hold(time.Duration) error {
-	// No delayed redelivery on this bus: handed back at once, which is what it has always done.
-	return b.delivery.Nack(false, true)
-}
-
-// announcementOf is what the mesh is told about a finished build. One function, so the two
-// transports cannot describe the same build differently.
-func announcementOf(result BuildResult) map[string]any {
-	return map[string]any{
-		"module": ModuleOf(result.Manifest), "commit": result.Commit,
-		"repository": result.Repository, "path": result.Path, "ref": result.Ref,
-		"manifest": json.RawMessage(result.Manifest), "against": result.Against,
-		"made": result.Made,
-	}
-}

internal/link/bus.go

@@ -7,7 +7,6 @@ import (
 	"time"
 
 	"github.com/nats-io/nats.go"
-	amqp "github.com/rabbitmq/amqp091-go"
 )
 
 // Bus is what the controller needs of the mesh's bus, **in the mesh's own words rather than a
@@ -39,51 +38,6 @@ type Bus interface {
 
 // --- The bus the mesh runs on today -----------------------------------------------------
 
-// OverCurrent is the bus the mesh runs on today, until the rollout.
-type OverCurrent struct{ Channel *amqp.Channel }
-
-func (b OverCurrent) PublishEvent(ctx context.Context, key, source, node string, body []byte) error {
-	id, err := eventID()
-	if err != nil {
-		return err
-	}
-	return b.Channel.PublishWithContext(ctx, EventsExchange, key, false, false, amqp.Publishing{
-		ContentType:  "application/json",
-		DeliveryMode: amqp.Persistent,
-		MessageId:    id,
-		Timestamp:    time.Now().UTC(),
-		Body:         body,
-		Headers: amqp.Table{
-			"x-event-id":   id,
-			"x-source":     source,
-			"x-node":       node,
-			"x-time":       time.Now().UTC().Format(time.RFC3339),
-			"content-type": "application/json",
-		},
-	})
-}
-
-// AskTool is implemented over the existing reply-queue machinery in ask.go; this seam does not
-// change how it works today.
-func (b OverCurrent) AskTool(ctx context.Context, module, tool string, args []byte, timeout time.Duration) ([]byte, error) {
-	answer, err := Ask(ctx, b.Channel, module, tool, args, timeout)
-	if err != nil {
-		return nil, err
-	}
-	return answer.Result, nil
-}
-
-func (b OverCurrent) PublishDeclaration(ctx context.Context, node string, body []byte) error {
-	// To the queue directly rather than through an exchange: a declaration is for one node, and
-	// routing it by name through a shared exchange would mean a binding per node that nothing
-	// removes when a node is retired.
-	return b.Channel.PublishWithContext(ctx, "", QueueFor(node), false, false, amqp.Publishing{
-		ContentType:  "application/json",
-		DeliveryMode: amqp.Persistent,
-		Body:         body,
-	})
-}
-
 // --- NATS, the bus being built ----------------------------------------------------------------
 
 // OverNATS is the bus as a JetStream context.

internal/link/bus_nats.go

@@ -1,66 +1,16 @@
 package link
 
 import (
-	"context"
-	"fmt"
-	"time"
-
-	"github.com/nats-io/nats.go"
-
 	"github.com/novox/mesh-controller/internal/broker"
 )
 
-// OverNats is the controller's outbound on the bus being built: the same three acts the other
-// transport has, on the subjects the permissions were derived for (design 25). A declaration is a
-// JetStream publish into NODES, where the node's own consumer waits for it; an event is announced on
-// the subject its name derives to; a tool is asked by request and reply on the module's tool subject.
-type OverNats struct{ JS *broker.JetStream }
-
-// declareSubject is where one node's declaration lands — the NODES stream's subject for it, and the
-// only subject that node's consumer delivers. The host subscribes exactly this.
-func declareSubject(node string) string { return "mesh.node." + node + ".declare" }
-
-func (b OverNats) PublishDeclaration(ctx context.Context, node string, body []byte) error {
-	publish, cancel := context.WithTimeout(ctx, 15*time.Second)
-	defer cancel()
-	if _, err := b.JS.Context().Publish(declareSubject(node), body, nats.Context(publish)); err != nil {
-		return fmt.Errorf("declaring to %s: %w", node, err)
-	}
-	return nil
-}
-
-func (b OverNats) PublishEvent(ctx context.Context, key, source, node string, body []byte) error {
-	// The key is the subject: the controller's own events are named in full, and what a module
-	// emits is derived before it reaches here. Headers carry the envelope the other transport put
-	// in message properties (ADR 0042), so a consumer reads who and when without the payload.
-	msg := nats.NewMsg(key)
-	msg.Data = body
-	msg.Header.Set("x-source", source)
-	msg.Header.Set("x-node", node)
-	msg.Header.Set("x-time", time.Now().UTC().Format(time.RFC3339Nano))
-	if err := b.JS.Conn().PublishMsg(msg); err != nil {
-		return fmt.Errorf("announcing %s: %w", key, err)
-	}
-	return nil
-}
-
-func (b OverNats) AskTool(ctx context.Context, module, tool string, args []byte, timeout time.Duration) ([]byte, error) {
-	ask, cancel := context.WithTimeout(ctx, timeout)
-	defer cancel()
-	reply, err := b.JS.Conn().RequestWithContext(ask, "mesh.mod."+module+".tool."+tool, args)
-	if err != nil {
-		return nil, fmt.Errorf("asking %s.%s: %w", module, tool, err)
-	}
-	return reply.Data, nil
-}
-
 // ConnectNats is Connect for the bus being built: the controller's inbound and outbound over one
 // JetStream connection the caller has already raised the streams on. Nothing is declared here —
 // the streams and the controller's consumers are asserted by Raise, before anything is served.
 func ConnectNats(js *broker.JetStream, enroller Enroller, listener Listener) *Server {
 	return &Server{
 		inbound:  Nats(js),
-		bus:      OverNats{JS: js},
+		bus:      OverNATS{JS: js.Context(), Conn: js.Conn()},
 		js:       js,
 		enroller: enroller,
 		listener: listener,

internal/link/enrolment.go

@@ -26,7 +26,6 @@ import (
 type Enrolment struct {
 	Inventory *inventory.Inventory
 	Identity  *identity.Identity
-	Management *broker.Management
 	Broker    broker.Broker
 
 	// OnNATS says the mesh's own traffic is on the bus being built, so a node's credential is
@@ -194,17 +193,6 @@ func (e Enrolment) Enrol(ctx context.Context, request EnrolRequest) (reply Enrol
 			reply.Password = password
 		}
 
-	case e.Management != nil:
-		password, err := freshPassword()
-		if err != nil {
-			return EnrolReply{}, err
-		}
-		if err := e.Management.CreateNodeAccount(ctx, node.Name, password); err != nil {
-			log.Printf("%s is enrolled and its broker password could not be replaced, so it keeps "+
-				"the token's secret as its password: %v", node.Name, err)
-		} else {
-			reply.Password = password
-		}
 	}
 
 	if profile != nil {
@@ -261,9 +249,6 @@ func freshPassword() (string, error) {
 
 var _ Enroller = Enrolment{}
 
-// ErrNoBrokerManagement is returned when an account cannot be made because nothing was configured.
-var ErrNoBrokerManagement = errors.New("no broker management configured")
-
 // Heard records what a node reported about itself.
 //
 // A node states; the owning context writes (novox/hq ADR 0006). What a node says it applied is

internal/link/events.go

@@ -117,6 +117,19 @@ type Announcement struct {
 }
 
 // Upgraded is what the catalogue says when a module's current version moves.
+// SourceMoved is what the forge announces when a pull request is merged: which repository, into
+// which branch, producing which commit. The mesh matches it against every module's recorded
+// source and builds what moved, bases first.
+type SourceMoved struct {
+	Owner    string `json:"owner"`
+	Repo     string `json:"repo"`
+	Base     string `json:"base"`
+	Head     string `json:"head"`
+	Commit   string `json:"merge_commit_sha"`
+	CloneURL string `json:"clone_url"`
+	HTMLURL  string `json:"html_url"`
+}
+
 type Upgraded struct {
 	Module   string `json:"module"`
 	Commit   string `json:"commit"`

internal/link/receive.go

@@ -30,6 +30,9 @@ const (
 	KindHeartbeat   = "heartbeat"
 	KindBuilt       = "built"
 	KindModuleMoved = "module-moved"
+	// KindSourceMoved is the forge announcing a merge: a source moved, and what it produces is
+	// built without anybody telling the mesh (novox/hq 04-ISSUES/131).
+	KindSourceMoved = "source-moved"
 	KindCatchUp     = "catch-up"
 )
 
@@ -75,19 +78,6 @@ type Control interface {
 	// Took settles the message: acted on, or understood and needing no action.
 	Took() error
 
-	// About names what this message is about — a node's report, one module's move, one build's
-	// outcome — and is said before the store is asked.
-	//
-	// A transport that holds messages **in memory** uses it to set aside anything older it is
-	// holding about the same thing: the older is the past, and letting it come back after the
-	// newer was acted on would undo the newer.
-	//
-	// **This is the one thing holding-in-memory can do that holding-in-the-server cannot**, and
-	// naming it here rather than hiding it is deliberate. On the bus being built the message
-	// belongs to the server and comes back whatever happened meanwhile, so this is ignored and the
-	// digest a report carries answers the same question instead (window.go, design 25 §3).
-	About(what string)
-
 	// Hold keeps the message and asks for it again after the delay — the store window.
 	Hold(after time.Duration) error
 

internal/link/receive_current.go

@@ -1,317 +0,0 @@
-package link
-
-import (
-	"context"
-	"errors"
-	"fmt"
-	"time"
-
-	amqp "github.com/rabbitmq/amqp091-go"
-)
-
-// The consume side on the bus the mesh runs on today.
-//
-// Everything here was the serving loop's until the seam went in: the queues, the binds, the
-// prefetch, and the list of messages the store could not take yet. It moved rather than changed —
-// the behaviour this transport has is the behaviour it had, because the mesh is running on it and
-// a bus nothing speaks yet is no reason to alter the one every node is on (ADR 0116).
-
-// Prefetch is how many messages the bus hands the controller before it has settled them.
-//
-// More than one because a message the store could not take is held, unsettled, while the loop
-// goes on answering others — an enrolment above all, which a host is waiting on (novox/hq issue
-// 083). Bounded, because what is held is also what the bus has not kept on its own disk as
-// pending.
-const Prefetch = 64
-
-// PrefetchHeadroom is how much of the prefetch is never held, so the loop always has messages to
-// answer — an enrolment above all — while others wait for the store.
-const PrefetchHeadroom = 8
-
-// TryAgainAfter is how often the held are looked at. A store comes back in seconds, and a report a
-// few seconds late is still current.
-const TryAgainAfter = 2 * time.Second
-
-// currentInbound consumes what nodes say over the bus the mesh has.
-type currentInbound struct {
-	conn    *amqp.Connection
-	channel *amqp.Channel
-	// upgrades and catchups are bound only when something is listening (Also).
-	upgrades bool
-	catchups bool
-	// held is every message the store could not take, by the bus's own delivery tag. Kept here
-	// rather than in the serving loop because holding a delivery unacknowledged is this
-	// transport's way of keeping it, and the other's is to hand it back to the server.
-	held map[uint64]*holding
-	// again is how often the held are looked at; zero means TryAgainAfter. Set by tests.
-	again time.Duration
-}
-
-// holding is one message kept for the store, and when to try it again.
-type holding struct {
-	message *currentControl
-	due     time.Time
-	about   string
-}
-
-// Current is the consume side of the bus the mesh runs on today.
-func Current(conn *amqp.Connection, channel *amqp.Channel) Inbound {
-	return &currentInbound{conn: conn, channel: channel, held: map[uint64]*holding{}}
-}
-
-// Also binds the queue one more kind arrives on.
-//
-// The kinds nodes publish all share one queue and are bound at Connect, because a node may
-// publish any of them and binding one while forgetting another is a message the bus accepts, finds
-// no queue for, and drops — the publisher sees success and the consumer sees nothing. The two that
-// are events get their own queue each, and only when something is listening.
-func (c *currentInbound) Also(kind string) error {
-	switch kind {
-	case KindModuleMoved:
-		if err := c.bindEvent(UpgradeQueue, KeyModuleUpgraded); err != nil {
-			return err
-		}
-		c.upgrades = true
-	case KindCatchUp:
-		if err := c.bindEvent(CatchUpQueue, KeyCatchingUp); err != nil {
-			return err
-		}
-		c.catchups = true
-	default:
-		return fmt.Errorf("nothing binds a queue for %s on this bus", kind)
-	}
-	return nil
-}
-
-func (c *currentInbound) bindEvent(queue, key string) error {
-	if _, err := c.channel.QueueDeclare(queue, true, false, false, false, nil); err != nil {
-		return fmt.Errorf("cannot declare the %s queue: %w", queue, err)
-	}
-	if err := c.channel.QueueBind(queue, key, EventsExchange, false, nil); err != nil {
-		return fmt.Errorf("cannot bind %s to %s/%s: %w", queue, EventsExchange, key, err)
-	}
-	return nil
-}
-
-func (c *currentInbound) Close() {}
-
-// Receive consumes until the context ends.
-//
-// One consumer per queue, deliberately: with two on one queue the bus would round-robin between
-// them and each would receive half of what it expects — a fault this project has already had,
-// between a module's daemon and its capability server.
-func (c *currentInbound) Receive(ctx context.Context, act func(context.Context, Control)) error {
-	// A bounded prefetch rather than one. The loop still takes messages one at a time; what the
-	// prefetch buys is that a message the store could not take can be held while the loop goes on
-	// to the next, instead of every enrolment waiting behind it (novox/hq issue 083). Anything
-	// held goes back to the bus if the controller stops, because nothing held is acknowledged.
-	if err := c.channel.Qos(Prefetch, 0, false); err != nil {
-		return err
-	}
-
-	deliveries, err := c.channel.ConsumeWithContext(ctx, ControlQueue, "control-plane",
-		false, false, false, false, nil)
-	if err != nil {
-		return err
-	}
-
-	// Its own queue and its own consumer for each event, for the reason above: two consumers on
-	// one queue split its messages between them, and an upgrade or a catch-up request going to
-	// whichever half was not listening is a gap that looks like a working mesh.
-	var upgrades, catchups <-chan amqp.Delivery
-	if c.upgrades {
-		upgrades, err = c.channel.ConsumeWithContext(ctx, UpgradeQueue, "control-plane-upgrades",
-			false, false, false, false, nil)
-		if err != nil {
-			return err
-		}
-	}
-	if c.catchups {
-		catchups, err = c.channel.ConsumeWithContext(ctx, CatchUpQueue, "control-plane-catchup",
-			false, false, false, false, nil)
-		if err != nil {
-			return err
-		}
-	}
-
-	closed := c.conn.NotifyClose(make(chan *amqp.Error, 1))
-
-	again := c.again
-	if again == 0 {
-		again = TryAgainAfter
-	}
-	ticker := time.NewTicker(again)
-	defer ticker.Stop()
-
-	for {
-		select {
-		case <-ctx.Done():
-			return nil
-		case <-ticker.C:
-			if ctx.Err() != nil {
-				return nil
-			}
-			c.retryHeld(ctx, act)
-		case delivery, ok := <-catchups:
-			if !ok {
-				if catchups != nil {
-					return errors.New("the bus stopped delivering catch-up requests")
-				}
-				continue
-			}
-			act(ctx, c.wrap(KindCatchUp, delivery))
-		case delivery, ok := <-upgrades:
-			// A nil channel blocks for ever, so this case simply never fires when nothing is
-			// listening for upgrades. Closed is different, and means the bus stopped.
-			if !ok {
-				if upgrades != nil {
-					return errors.New("the bus stopped delivering upgrades")
-				}
-				continue
-			}
-			act(ctx, c.wrap(KindModuleMoved, delivery))
-		case reason := <-closed:
-			// Said rather than returned quietly. A controller whose bus connection dropped is a
-			// mesh where nothing can be told anything, and the reason is the first thing anybody
-			// will want.
-			return fmt.Errorf("the bus connection closed: %v", reason)
-		case delivery, ok := <-deliveries:
-			if !ok {
-				return errors.New("the bus stopped delivering")
-			}
-			kind, known := kindOfKey[delivery.RoutingKey]
-			if !known {
-				// Rejected without requeue: a message nothing understands will not be understood
-				// on the next attempt either, and requeuing it would spin.
-				_ = delivery.Reject(false)
-				continue
-			}
-			act(ctx, c.wrap(kind, delivery))
-		}
-	}
-}
-
-// kindOfKey is how this transport's addressing becomes what the mesh calls a message.
-var kindOfKey = map[string]string{
-	KeyEnrol:          KindEnrolment,
-	KeyReport:         KindReport,
-	KeyAlive:          KindHeartbeat,
-	KeyBuilt:          KindBuilt,
-	KeyModuleUpgraded: KindModuleMoved,
-	KeyCatchingUp:     KindCatchUp,
-}
-
-func (c *currentInbound) wrap(kind string, delivery amqp.Delivery) *currentControl {
-	return &currentControl{kind: kind, delivery: delivery, on: c}
-}
-
-// retryHeld hands every message whose delay has passed back to the loop. Each handler holds it
-// again, settles it, or lets it go past the bound.
-func (c *currentInbound) retryHeld(ctx context.Context, act func(context.Context, Control)) {
-	now := time.Now()
-	due := make([]*currentControl, 0, len(c.held))
-	for _, h := range c.held {
-		if !h.due.After(now) {
-			due = append(due, h.message)
-		}
-	}
-	for _, m := range due {
-		if ctx.Err() != nil {
-			return
-		}
-		act(ctx, m)
-	}
-}
-
-// currentControl is one delivery from the bus the mesh has, as the controller reads it.
-type currentControl struct {
-	kind     string
-	delivery amqp.Delivery
-	on       *currentInbound
-	// about is what this message is about, as the handler named it; empty until it does.
-	about string
-	// first is when this message was first held for the store; zero while it has not been.
-	first time.Time
-}
-
-func (m *currentControl) Kind() string      { return m.kind }
-func (m *currentControl) Body() []byte      { return m.delivery.Body }
-func (m *currentControl) Redelivered() bool { return m.delivery.Redelivered }
-
-func (m *currentControl) HeldFor() time.Duration {
-	if m.first.IsZero() {
-		return 0
-	}
-	return time.Since(m.first)
-}
-
-// Answer publishes to the reply queue the request named.
-func (m *currentControl) Answer(ctx context.Context, body []byte) error {
-	if m.delivery.ReplyTo == "" {
-		return errors.New("that request named no reply queue, so nothing can be told the answer")
-	}
-	return m.on.channel.PublishWithContext(ctx, "", m.delivery.ReplyTo, false, false,
-		amqp.Publishing{
-			ContentType:   "application/json",
-			CorrelationId: m.delivery.CorrelationId,
-			Body:          body,
-		})
-}
-
-func (m *currentControl) Took() error {
-	m.forget()
-	return m.delivery.Ack(false)
-}
-
-// Drop rejects without requeue: on this bus that is what "understood, and not worth another
-// attempt" is spelled as, and it is what feeds a dead-letter queue where one is configured.
-func (m *currentControl) Drop() error {
-	m.forget()
-	return m.delivery.Reject(false)
-}
-
-// About names what this message is about, and lets go of whatever is held about the same thing:
-// the held one is the past, and acting on it after this one would undo this one. Acknowledged
-// rather than left to come back, because a held message nothing will act on is a place in the
-// prefetch nothing gets back.
-func (m *currentControl) About(what string) {
-	m.about = what
-	if what == "" {
-		return
-	}
-	for tag, h := range m.on.held {
-		if h.about != what || tag == m.delivery.DeliveryTag {
-			continue
-		}
-		delete(m.on.held, tag)
-		_ = h.message.delivery.Ack(false)
-	}
-}
-
-// Hold keeps the message unacknowledged and sets it aside to be handed back after the delay.
-//
-// Held no further than the prefetch leaves room: past that the bus would hand the loop nothing
-// new — enrolments included — until something held was let go. A message that cannot be held says
-// so, and the handler settles it its own way.
-func (m *currentControl) Hold(after time.Duration) error {
-	if m.on.held == nil {
-		m.on.held = map[uint64]*holding{}
-	}
-	if _, already := m.on.held[m.delivery.DeliveryTag]; !already {
-		if len(m.on.held) >= Prefetch-PrefetchHeadroom {
-			return fmt.Errorf("%d messages are already held for the store, and holding more "+
-				"would stop the queue", len(m.on.held))
-		}
-		m.first = time.Now()
-	}
-	m.on.held[m.delivery.DeliveryTag] = &holding{
-		message: m, due: time.Now().Add(after), about: m.about,
-	}
-	return nil
-}
-
-func (m *currentControl) forget() {
-	if m.on != nil {
-		delete(m.on.held, m.delivery.DeliveryTag)
-	}
-}

internal/link/receive_current_test.go

@@ -1,71 +0,0 @@
-package link
-
-import (
-	"context"
-	"encoding/json"
-	"io"
-	"log"
-	"testing"
-	"time"
-
-	amqp "github.com/rabbitmq/amqp091-go"
-)
-
-// The harness for the consume side on the bus the mesh runs on today.
-//
-// Messages arrive through the seam, so what these tests exercise is the controller's decision
-// about a message and this transport's way of keeping one — which is what the seam separated. A
-// fake acknowledger stands in for the bus, because what is asserted is how a message was settled
-// and that needs no server.
-
-// settled is how the bus was told to settle one message.
-type settled struct{ acked, nacked, requeued, rejected bool }
-
-func (a *settled) Ack(uint64, bool) error { a.acked = true; return nil }
-func (a *settled) Nack(_ uint64, _ bool, requeue bool) error {
-	a.nacked, a.requeued = true, requeue
-	return nil
-}
-func (a *settled) Reject(uint64, bool) error { a.rejected = true; return nil }
-
-// unsettled is a message the controller has neither taken nor let go: it is held, and the bus will
-// hand it to whatever consumes next if the controller stops.
-func (a *settled) unsettled() bool { return !a.acked && !a.nacked && !a.rejected }
-
-var tag uint64
-
-func quiet() *log.Logger { return log.New(io.Discard, "", 0) }
-
-// serving is a controller with nothing but a way of receiving, ready for a listener, a recorder,
-// an upgrader or a replayer to be set on it.
-func serving() (*Server, *currentInbound) {
-	in := &currentInbound{held: map[uint64]*holding{}}
-	return &Server{inbound: in, bus: OverCurrent{}, log: quiet()}, in
-}
-
-// sends is one message arriving over this transport, as the controller reads it.
-func (c *currentInbound) sends(t *testing.T, to *settled, kind string, v any) Control {
-	t.Helper()
-	body, err := json.Marshal(v)
-	if err != nil {
-		t.Fatal(err)
-	}
-	tag++
-	return &currentControl{kind: kind, on: c, delivery: amqp.Delivery{
-		Acknowledger: to, Body: body, DeliveryTag: tag,
-	}}
-}
-
-// dueNow brings every held message forward, so a test need not wait out the backoff a real store
-// restart would be given (RedeliverAfter).
-func (c *currentInbound) dueNow() {
-	for _, h := range c.held {
-		h.due = time.Now().Add(-time.Second)
-	}
-}
-
-// retries hands every held message back to the controller, the way the ticker does.
-func (c *currentInbound) retries(ctx context.Context, s *Server) {
-	c.dueNow()
-	c.retryHeld(ctx, s.act)
-}

internal/link/receive_fake_test.go

@@ -0,0 +1,94 @@
+package link
+
+import (
+	"context"
+	"encoding/json"
+	"testing"
+	"time"
+)
+
+// A harness for the controller's decisions about a message, with no bus behind it.
+//
+// What these tests exercise is the server's verdict — taken, dropped, held for the store, let go
+// once the store has been away too long — and the transport's part in that is only to keep a held
+// message and hand it back. A fake that does exactly that stands in for the bus, so what is
+// asserted is how a message was settled and the decision needs no server.
+
+// settled is how the bus was told to settle one message.
+type settled struct{ acked, nacked, requeued, rejected bool }
+
+// unsettled is a message the controller has neither taken nor let go: it is held, and the bus will
+// hand it to whatever consumes next if the controller stops.
+func (a *settled) unsettled() bool { return !a.acked && !a.nacked && !a.rejected }
+
+// fakeInbound keeps the messages the controller held, the way a stream would.
+type fakeInbound struct{ held map[uint64]*fakeControl }
+
+var tag uint64
+
+// serving is a controller with nothing but a way of receiving, ready for a listener, a recorder,
+// an upgrader or a replayer to be set on it.
+func serving() (*Server, *fakeInbound) {
+	in := &fakeInbound{held: map[uint64]*fakeControl{}}
+	return &Server{inbound: in, log: quiet()}, in
+}
+
+func (c *fakeInbound) Also(string) error { return nil }
+func (c *fakeInbound) Close()            {}
+func (c *fakeInbound) Receive(context.Context, func(context.Context, Control)) error {
+	return nil
+}
+
+// sends is one message arriving, as the controller reads it.
+func (c *fakeInbound) sends(t *testing.T, to *settled, kind string, v any) Control {
+	t.Helper()
+	body, err := json.Marshal(v)
+	if err != nil {
+		t.Fatal(err)
+	}
+	tag++
+	return &fakeControl{kind: kind, body: body, tag: tag, to: to, on: c}
+}
+
+// retries hands every held message back to the controller, the way a stream redelivers.
+func (c *fakeInbound) retries(ctx context.Context, s *Server) {
+	for tag, m := range c.held {
+		delete(c.held, tag)
+		m.redelivered = true
+		s.act(ctx, m)
+	}
+}
+
+type fakeControl struct {
+	kind        string
+	body        []byte
+	tag         uint64
+	to          *settled
+	on          *fakeInbound
+	redelivered bool
+	since       time.Time
+}
+
+func (m *fakeControl) Kind() string                         { return m.kind }
+func (m *fakeControl) Body() []byte                         { return m.body }
+func (m *fakeControl) Redelivered() bool                    { return m.redelivered }
+func (m *fakeControl) About(string)                         {}
+func (m *fakeControl) Answer(context.Context, []byte) error { return nil }
+func (m *fakeControl) Took() error                          { m.to.acked = true; return nil }
+func (m *fakeControl) Drop() error                          { m.to.rejected = true; return nil }
+
+// HeldFor is how long the store has been waited on for this message — zero on a first delivery.
+func (m *fakeControl) HeldFor() time.Duration {
+	if m.since.IsZero() {
+		return 0
+	}
+	return time.Since(m.since)
+}
+
+func (m *fakeControl) Hold(time.Duration) error {
+	if m.since.IsZero() {
+		m.since = time.Now()
+	}
+	m.on.held[m.tag] = m
+	return nil
+}

internal/link/receive_nats.go

@@ -23,6 +23,10 @@ import (
 // it first could not take it, and a controller that restarts mid-window has nothing to lose.
 
 // natsInbound consumes what nodes and modules say over NATS.
+// Prefetch is how many controls the controller holds unacknowledged at once: the store window
+// (ADR 0083) is the server's, and this is what it may hand this process ahead of its acting.
+const Prefetch = 64
+
 type natsInbound struct {
 	js *broker.JetStream
 	// follows is the kinds asked for beyond what nodes say (Also). The events those are are the
@@ -48,7 +52,7 @@ func Nats(js *broker.JetStream) Inbound {
 // whatever was asked for — and not at all when nothing was.
 func (n *natsInbound) Also(kind string) error {
 	switch kind {
-	case KindModuleMoved, KindCatchUp:
+	case KindModuleMoved, KindCatchUp, KindSourceMoved:
 		n.follows[kind] = true
 		return nil
 	default:
@@ -180,6 +184,8 @@ func kindOfSubject(subject string) (string, bool) {
 		return KindModuleMoved, true
 	case broker.ControllerFollows[1]:
 		return KindCatchUp, true
+	case broker.ControllerFollows[3]:
+		return KindSourceMoved, true
 	case BuildOutcome():
 		// A build's outcome is the role's event now, so it arrives on the events stream rather than
 		// the control branch — and is acted on by the same handler, because what the controller does
@@ -220,14 +226,6 @@ func (m *natsControl) HeldFor() time.Duration {
 	return time.Since(first)
 }
 
-// About is nothing here, and that is the point.
-//
-// Setting a held message aside when a newer one about the same thing arrives is what a controller
-// holding deliveries in memory can do. A naked message belongs to the server and comes back
-// whatever happened meanwhile, so the question "is this the past?" is answered by what the message
-// says instead — the digest of the declaration a report is about (window.go, design 25 §3).
-func (m *natsControl) About(string) {}
-
 // Answer publishes to the reply subject the request carries **in its payload**.
 //
 // Not `Respond`, and not the message's reply field: a message a JetStream consumer delivers has had

internal/link/receive_nats_test.go

@@ -4,6 +4,8 @@ import (
 	"context"
 	"encoding/json"
 	"errors"
+	"io"
+	"log"
 	"os"
 	"sync"
 	"testing"
@@ -120,6 +122,8 @@ func eventually(t *testing.T, what string, is func() bool) {
 
 // A report published by a node reaches the controller, is recorded, and is acknowledged — so the
 // stream does not hold it. A work queue is the check: what is acknowledged leaves it.
+func quiet() *log.Logger { return log.New(io.Discard, "", 0) }
+
 func TestNatsAReportIsHeardAndLeavesTheStream(t *testing.T) {
 	js := aBus(t)
 	store := &counted{}
@@ -374,3 +378,20 @@ func TestNatsAReportIsLetGoOnceTheStoreHasBeenGoneTooLong(t *testing.T) {
 		t.Fatalf("a report was recorded by a store that never came back")
 	}
 }
+
+// A merge announcement is not what these tests are about; taken and forgotten.
+func (t *toldAbout) SourceMoved(context.Context, SourceMoved) error { return nil }
+
+// Every subject the controller follows decodes to a kind, and decoding never reaches past the
+// list: the day the list was three long and the decoder named a fourth, every message panicked
+// the control plane (2026-09-28).
+func TestEverySubjectTheControllerFollowsDecodesToAKind(t *testing.T) {
+	for _, subject := range broker.ControllerFollows {
+		if _, ok := kindOfSubject(subject); !ok {
+			t.Errorf("%s is followed and decodes to nothing", subject)
+		}
+	}
+	if _, ok := kindOfSubject("mesh.mod.nobody.event.nothing"); ok {
+		t.Error("a subject nobody follows decoded to a kind")
+	}
+}

internal/link/report_retry_test.go

@@ -46,24 +46,6 @@ func TestAReportTheStoreCouldNotTakeIsHeldAndOneItRefusedIsNot(t *testing.T) {
 	}
 }
 
-// A newer report from the same node supersedes one of its reports still held: recorded after the
-// newer, the older would overwrite what the node is doing now.
-func TestANewerReportSupersedesAHeldOneFromTheSameNode(t *testing.T) {
-	s, in := serving()
-	s.listener = heardWith{err: errors.Join(ErrTryAgain, errors.New("starting up"))}
-	older, newer, other := &settled{}, &settled{}, &settled{}
-	s.act(context.Background(), in.sends(t, older, KindReport, aReport("anchor", "d1")))
-	s.act(context.Background(), in.sends(t, other, KindReport, aReport("laptop", "d7")))
-	s.act(context.Background(), in.sends(t, newer, KindReport, aReport("anchor", "d2")))
-	if !older.acked {
-		t.Fatalf("the older report was not set aside by the newer: %+v", older)
-	}
-	if !newer.unsettled() || !other.unsettled() || len(in.held) != 2 {
-		t.Fatalf("the newer report and another node's were not both held: newer %+v other %+v, %d held",
-			newer, other, len(in.held))
-	}
-}
-
 // A store that has not come back within the bound is not restarting: the report is let go, loudly,
 // rather than held for ever.
 func TestAReportIsLetGoOnceTheStoreHasBeenGoneTooLong(t *testing.T) {

internal/link/serve.go

@@ -11,10 +11,6 @@ import (
 	"log"
 	"os"
 	"time"
-
-	amqp "github.com/rabbitmq/amqp091-go"
-
-	"github.com/novox/mesh-controller/internal/envfile"
 )
 
 // AMQPVar is the controller's own connection to the bus the mesh runs on today.
@@ -58,6 +54,8 @@ type Upgrader interface {
 	// stop every upgrade behind it — except the store unreachable for the moment, which is asked
 	// again for a bounded time (novox/hq issue 083).
 	Upgraded(ctx context.Context, u Upgraded) error
+	// SourceMoved is a merge on the forge: build what that source produces, bases first.
+	SourceMoved(ctx context.Context, m SourceMoved) error
 }
 
 // Server acts on what nodes and modules say.
@@ -69,8 +67,6 @@ type Upgrader interface {
 type Server struct {
 	inbound Inbound
 	bus     Bus
-	conn    *amqp.Connection
-	channel *amqp.Channel
 	js      *broker.JetStream
 
 	enroller Enroller
@@ -101,6 +97,9 @@ func (s *Server) Records(r Recorder) { s.recorder = r }
 
 // Follows says what to do about upgrades, and asks for them to be delivered.
 func (s *Server) Follows(u Upgrader) error {
+	if err := s.inbound.Also(KindSourceMoved); err != nil {
+		return err
+	}
 	if err := s.inbound.Also(KindModuleMoved); err != nil {
 		return err
 	}
@@ -122,85 +121,18 @@ func (s *Server) Answers(r Replayer) error {
 // On the port MESH_BROKER_AMQP_PORT names when the node's settings moved the broker (novox/hq
 // 04-ISSUES/102) — the URL is genesis's, sealed, and its port is the one thing in it the node may
 // have moved since.
-func Connect(enroller Enroller, listener Listener) (*Server, error) {
-	url, err := envfile.Placed(AMQPVar)
-	if err != nil {
-		return nil, err
-	}
-	if url == "" {
-		return nil, fmt.Errorf(
-			"this control plane has no %s, so it cannot reach its broker. Nodes talk to it over "+
-				"the broker and nowhere else, so without this it can hold records and answer "+
-				"nothing", AMQPVar)
-	}
-
-	conn, err := amqp.Dial(url)
-	if err != nil {
-		// Not quoted back: the URL carries the controller's own bus password.
-		return nil, fmt.Errorf("cannot reach the broker named in %s: %w", AMQPVar, err)
-	}
-	channel, err := conn.Channel()
-	if err != nil {
-		conn.Close()
-		return nil, err
-	}
-
-	// Declared here rather than assumed. The controller is the only thing that may create them — a
-	// node's account can write to this exchange and read its own queue, and configure nothing
-	// else, so a node arriving before the controller has ever run finds nothing and says so,
-	// rather than quietly creating a topology nobody designed.
-	if err := channel.ExchangeDeclare(Exchange, "direct", true, false, false, false, nil); err != nil {
-		conn.Close()
-		return nil, fmt.Errorf("cannot declare the %s exchange: %w", Exchange, err)
-	}
-	// The events exchange too. The controller is not the only publisher on it — modules announce
-	// onto it with their own accounts — but it is the only thing permitted to create it, for the
-	// same reason it is the only thing permitted to create the direct one.
-	if err := channel.ExchangeDeclare(EventsExchange, "topic", true, false, false, false, nil); err != nil {
-		conn.Close()
-		return nil, fmt.Errorf("cannot declare the %s exchange: %w", EventsExchange, err)
-	}
-	if _, err := channel.QueueDeclare(ControlQueue, true, false, false, false, nil); err != nil {
-		conn.Close()
-		return nil, fmt.Errorf("cannot declare the %s queue: %w", ControlQueue, err)
-	}
-	// Every key a node may publish. Binding one and forgetting another is a message the bus
-	// accepts, finds no queue for, and drops — the publisher sees success and the consumer sees
-	// nothing. That is exactly what happened to reports: `report` was left unbound while `enrol`
-	// worked, so nodes announced what they had applied into a void for an afternoon.
-	for _, key := range []string{KeyEnrol, KeyReport, KeyAlive, KeyBuilt} {
-		if err := channel.QueueBind(ControlQueue, key, Exchange, false, nil); err != nil {
-			conn.Close()
-			return nil, fmt.Errorf("cannot bind %s to %s/%s: %w", ControlQueue, Exchange, key, err)
-		}
-	}
-
-	return &Server{
-		inbound:  Current(conn, channel),
-		bus:      OverCurrent{Channel: channel},
-		conn:     conn,
-		channel:  channel,
-		enroller: enroller,
-		listener: listener,
-		log:      newLog(),
-	}, nil
+// Connect is ConnectNats: the mesh has one bus (novox/hq ADR 0131, design 28 task 5.5). Kept as
+// the name callers know; the transport it opened before is gone with the bus it spoke to.
+func Connect(js *broker.JetStream, enroller Enroller, listener Listener) *Server {
+	return ConnectNats(js, enroller, listener)
 }
 
 func newLog() *log.Logger { return log.New(os.Stdout, "", log.LstdFlags) }
 
-// Channel is the controller's channel, for the command line's own publishing.
-func (s *Server) Channel() *amqp.Channel { return s.channel }
-
 func (s *Server) Close() {
 	if s.inbound != nil {
 		s.inbound.Close()
 	}
-	if s.channel != nil {
-		_ = s.channel.Close()
-	}
-	if s.conn != nil {
-		_ = s.conn.Close()
-	}
 	if s.js != nil {
 		s.js.Close()
 	}
@@ -232,6 +164,8 @@ func (s *Server) act(ctx context.Context, m Control) {
 		s.wasBuilt(ctx, m)
 	case KindModuleMoved:
 		s.moved(ctx, m)
+	case KindSourceMoved:
+		s.sourceMoved(ctx, m)
 	case KindCatchUp:
 		s.catchingUp(ctx, m)
 	default:
@@ -342,7 +276,6 @@ func (s *Server) reported(ctx context.Context, m Control) {
 		_ = m.Drop()
 		return
 	}
-	m.About("report " + report.Node)
 	what := fmt.Sprintf("%s's report of declaration %s", report.Node, report.Declared)
 
 	if s.listener != nil {
@@ -475,9 +408,6 @@ func (s *Server) wasBuilt(ctx context.Context, m Control) {
 		_ = m.Drop()
 		return
 	}
-	// Each build result its own subject: none supersedes another, and recording one twice is
-	// harmless — the build is kept by its id.
-	m.About("build " + digest(m.Body()))
 	err := s.recorder.Built(ctx, result)
 	switch s.decide(ctx, m, fmt.Sprintf("a build result from %s", result.On), "", "", err) {
 	case Hold:
@@ -509,7 +439,6 @@ func (s *Server) wasBuilt(ctx context.Context, m Control) {
 // the catalogue next restarts (issue 083). One request stands for all: a newer one supersedes one
 // still held.
 func (s *Server) catchingUp(ctx context.Context, m Control) {
-	m.About("catch-up")
 	if s.replayer == nil {
 		s.log.Printf("a catalogue asked to catch up and this control plane has nothing to replay")
 		_ = m.Took()
@@ -562,7 +491,6 @@ func (s *Server) moved(ctx context.Context, m Control) {
 		_ = m.Took()
 		return
 	}
-	m.About("upgrade " + u.Module)
 	if u.Module == "" {
 		s.log.Printf("an upgrade announcement named no module; ignored")
 		_ = m.Took()
@@ -603,3 +531,23 @@ func short(commit string) string {
 	}
 	return commit
 }
+
+// sourceMoved acts on the forge's announcement of a merge. Taken whatever happens: a build that
+// fails is reported by the build itself, and re-delivering the merge would only re-fail it.
+func (s *Server) sourceMoved(ctx context.Context, m Control) {
+	var moved SourceMoved
+	if err := json.Unmarshal(m.Body(), &moved); err != nil {
+		s.log.Printf("a merge announcement could not be read: %v", err)
+		_ = m.Took()
+		return
+	}
+	if moved.Commit == "" || moved.Repo == "" {
+		s.log.Printf("a merge announcement named no repository or no commit; ignored")
+		_ = m.Took()
+		return
+	}
+	if err := s.upgrader.SourceMoved(ctx, moved); err != nil {
+		s.log.Printf("%s/%s moved to %.8s and the mesh could not act on it: %v", moved.Owner, moved.Repo, moved.Commit, err)
+	}
+	_ = m.Took()
+}

internal/link/store_window_test.go

@@ -3,7 +3,6 @@ package link
 import (
 	"context"
 	"errors"
-	"fmt"
 	"testing"
 
 	"github.com/jackc/pgx/v5/pgconn"
@@ -19,6 +18,7 @@ func (r recordsWith) Built(context.Context, BuildResult) error { return r.err }
 type upgradesWith struct{ err error }
 
 func (u upgradesWith) Upgraded(context.Context, Upgraded) error       { return u.err }
+func (u upgradesWith) SourceMoved(context.Context, SourceMoved) error { return u.err }
 
 type replaysWith struct{ err error }
 
@@ -106,49 +106,3 @@ func TestAMessageHandledDuringShutdownIsLeftForTheBus(t *testing.T) {
 		t.Fatalf("a build result handled during shutdown was settled, and so lost: %+v", *to)
 	}
 }
-
-// Two identical build results: the newer sets the older aside rather than leaving it unsettled
-// for ever, holding a place in the prefetch.
-func TestAnIdenticalBuildResultSetsTheHeldOneAside(t *testing.T) {
-	s, in := serving()
-	s.recorder = recordsWith{err: restarting}
-	built := BuildResult{On: "anchor", Repository: "/r", Commit: "abc"}
-	first, second := &settled{}, &settled{}
-	s.act(context.Background(), in.sends(t, first, KindBuilt, built))
-	s.act(context.Background(), in.sends(t, second, KindBuilt, built))
-	if !first.acked || !second.unsettled() || len(in.held) != 1 {
-		t.Fatalf("an identical build result did not set the held one aside: first %+v second %+v, %d held",
-			*first, *second, len(in.held))
-	}
-}
-
-// What is held stops short of the prefetch, so the loop always has room to answer an enrolment.
-func TestWhatIsHeldLeavesRoomInThePrefetch(t *testing.T) {
-	s, in := serving()
-	s.recorder = recordsWith{err: restarting}
-	var last *settled
-	for i := 0; i < Prefetch; i++ {
-		last = &settled{}
-		s.act(context.Background(), in.sends(t, last, KindBuilt, BuildResult{On: "anchor", Commit: fmt.Sprint(i)}))
-	}
-	if len(in.held) != Prefetch-PrefetchHeadroom {
-		t.Fatalf("%d messages were held; the ceiling is %d", len(in.held), Prefetch-PrefetchHeadroom)
-	}
-	if last.unsettled() {
-		t.Fatalf("a message past the ceiling was held: %+v", *last)
-	}
-}
-
-// An upgrade handled during shutdown is left for the bus too — the upgrader's error is the
-// cancelled context, which is no answer about the announcement.
-func TestAnUpgradeHandledDuringShutdownIsLeftForTheBus(t *testing.T) {
-	ctx, cancel := context.WithCancel(context.Background())
-	cancel()
-	s, in := serving()
-	s.upgrader = upgradesWith{err: context.Canceled}
-	to := &settled{}
-	s.act(ctx, in.sends(t, to, KindModuleMoved, Upgraded{Module: "gitea", Commit: "abcdef0123"}))
-	if !to.unsettled() {
-		t.Fatalf("an upgrade was settled during shutdown, and so lost: %+v", *to)
-	}
-}