Pin the node-engine at its merge of the access grant, and capture it beside (hq ADR 0312, issue 537)

A path beginning with the same letters is another path, and a read-only mount
of a read-write access is still granted: the grant follows what mounts it.

cmd/mesh-controller/acts.go

@@ -4,7 +4,6 @@ import (
 	"context"
 	"fmt"
 	"github.com/novox/mesh-controller/internal/broker"
-	"io"
 	"slices"
 	"sort"
 	"strings"
@@ -55,9 +54,6 @@ func assignWith(ctx context.Context, open *stores, node string, opts assignOptio
 	if err := refusedMovingTheController(modules); err != nil {
 		return "", err
 	}
-	// Every line of the answer comes from the one resolution after the write (novox/hq issue 237):
-	// what the reads before it would say about a machine left out is not the answer's.
-	ctx = leftOutSaidBy(ctx, io.Discard)
 	// Held while it is recorded, so it cannot land between a converge's preview and its flip and
 	// be taken without ever having been previewed (novox/hq ADR 0100).
 	ctx, release, err := holdNodes(ctx, open, []string{node})
@@ -129,28 +125,22 @@ func assignWith(ctx context.Context, open *stores, node string, opts assignOptio
 	for _, line := range settled {
 		answer += "\n  " + line
 	}
+	// What this act changed about this node's unmet seat dependencies, and nothing else (novox/hq
+	// ADR 0207): a dependency of a module just assigned, or one this assignment met. The rest of the
+	// node's list, and every other node's, is `status`'s.
+	for _, line := range unheldChange(shelf, node, before, append(append([]string(nil), before...), added...)) {
+		answer += "\n  " + line
+	}
 	// Its bus credential, in the same act (novox/hq issue 203): an assignment pushed before its
 	// credential exists delivers a process that cannot authenticate and crash-loops until somebody
 	// runs a second verb and a second push. Issued here when the module speaks on the bus and has
 	// no credential yet; kept when it has one, so re-assigning rotates nothing.
-	var issued []string
 	for _, module := range added {
 		if line := issueOnAssign(ctx, open, node, module); line != "" {
-			issued = append(issued, line)
+			answer += "\n  " + line
 		}
 	}
-	// **The one resolution the rest of the answer is said from** (novox/hq issue 237), taken after
-	// the write: what this act changed about this node's unmet seat dependencies, and nothing else
-	// (novox/hq ADR 0207) — a dependency of a module just assigned, or one this assignment met; the
-	// rest of the node's list, and every other node's, is `status`'s — and whether the node resolves.
-	after := resolvedAfter(ctx, open, shelf, node)
-	for _, line := range unheldChangeTo(shelf, node, before, after.modules, after.unheld) {
-		answer += "\n  " + line
-	}
-	for _, line := range issued {
-		answer += "\n  " + line
-	}
-	plan, err := after.plan, after.err
+	plan, _, err := planFor(ctx, open, node)
 	if err != nil {
 		// Kept, and still refused. Both halves are the answer, and the rest of the mesh is still
 		// worth reporting: this machine's refusal is rarely the only consequence.
@@ -228,8 +218,6 @@ func unassign(ctx context.Context, open *stores, node string, modules ...string)
 	if len(modules) == 0 {
 		return "", fmt.Errorf("unassign %s names no module", node)
 	}
-	// One resolution after the write, as assign's answer (novox/hq issue 237).
-	ctx = leftOutSaidBy(ctx, io.Discard)
 	ctx, release, err := holdNodes(ctx, open, []string{node})
 	if err != nil {
 		return "", err
@@ -274,21 +262,14 @@ func unassign(ctx context.Context, open *stores, node string, modules ...string)
 	}
 	answer := fmt.Sprintf("%s no longer runs %s — run `push %s` to make it so",
 		node, strings.Join(modules, ", "), node)
-	after := resolvedAfter(ctx, open, shelf, node)
-	for _, line := range unheldChangeTo(shelf, node, assigned, after.modules, after.unheld) {
-		answer += "\n  " + line
+	var left []string
+	for _, a := range assigned {
+		if !slices.Contains(modules, a) {
+			left = append(left, a)
+		}
 	}
-	// Whether the node itself still resolves, from the same resolution: before, only the rest of the
-	// mesh's reads said it, on standard error and once per other machine.
-	if after.err != nil {
-		if unresolvable(after.err) {
-			answer += fmt.Sprintf("\n  but %s does not resolve now, so nothing will be sent to it:", node)
-		} else {
-			answer += fmt.Sprintf("\n  but whether %s still resolves could not be read:", node)
-		}
-		for _, line := range strings.Split(strings.TrimRight(after.err.Error(), "\n"), "\n") {
-			answer += "\n    " + strings.TrimSpace(line)
-		}
+	for _, line := range unheldChange(shelf, node, assigned, left) {
+		answer += "\n  " + line
 	}
 	// What it leaves behind that is irreplaceable is kept and retired, never removed (novox/hq ADR 0233).
 	for _, line := range keptOnUnassign(ctx, open.inventory, node, modules) {
@@ -297,39 +278,6 @@ func unassign(ctx context.Context, open *stores, node string, modules ...string)
 	return answer + blockedElsewhere(ctx, open, node), nil
 }
 
-// afterAct is the one resolution of a node an act's answer is said from, taken after its write
-// (novox/hq issue 237): the plan or why there is none, the modules it has on the node, and its unmet
-// seat dependencies.
-type afterAct struct {
-	plan    catalogue.Resolution
-	err     error
-	modules []string
-	unheld  []catalogue.Unheld
-}
-
-// resolvedAfter resolves the node as `plan` does, once, after the act's write. When the node resolves,
-// its modules and unmet seat dependencies are the resolution's — the closure, so a holder pulled in by
-// a requirement counts as `plan` counts it. When it does not, they are judged over the assignments read
-// after the write, which can only find more unmet than the closure would: a seat said held there is
-// held in the closure too.
-func resolvedAfter(ctx context.Context, open *stores, shelf map[string]catalogue.Manifest, node string) afterAct {
-	plan, _, err := planFor(ctx, open, node)
-	if err == nil {
-		out := afterAct{plan: plan, unheld: plan.Unheld}
-		for _, m := range plan.Modules {
-			out.modules = append(out.modules, m.Module)
-		}
-		return out
-	}
-	out := afterAct{err: err}
-	assigned, readErr := open.inventory.Assigned(ctx, node)
-	if readErr != nil {
-		return out
-	}
-	out.modules, out.unheld = assigned, unheldOver(shelf, node, assigned)
-	return out
-}
-
 // splitModules is a surface's one `module` field as the modules it names: several, comma-separated,
 // are one act (novox/hq ADR 0207), so the holders that depend on each other go on together from the
 // command API and the controller seat's verbs as they do from the command line.

cmd/mesh-controller/one_resolution_test.go

@@ -1,112 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"context"
-	"errors"
-	"strings"
-	"testing"
-
-	"github.com/novox/mesh-controller/internal/catalogue"
-)
-
-// novox/hq issue 237: every line of an act's answer comes from one resolution of the node taken after
-// its write, so the answer agrees with `plan` for the node right after.
-
-func aProviderAndItsConsumer(t *testing.T, open *stores) {
-	t.Helper()
-	register(t, open, catalogue.Manifest{Module: "db", Version: "1",
-		Provides: []catalogue.Offer{{Name: "rows", Scope: catalogue.ScopeNode}}})
-	register(t, open, catalogue.Manifest{Module: "app", Version: "1", Requires: []string{"rows"}})
-}
-
-// twoRivalsAndANote is a node that does not resolve — two modules claim one node seat there — and a
-// module beside them that changes nothing about it.
-func twoRivalsAndANote(t *testing.T, open *stores) {
-	t.Helper()
-	one, two := rivals()
-	register(t, open, one)
-	register(t, open, two)
-	register(t, open, catalogue.Manifest{Module: "notes", Version: "1"})
-}
-
-func TestAnUnassignThatLeavesItsNodeUnresolvedSaysSoOnceInItsAnswer(t *testing.T) {
-	open := aMesh(t)
-	ctx := t.Context()
-	twoRivalsAndANote(t, open)
-	// Straight into the store, as a node that came to this before the act.
-	for _, m := range []string{"rival-one", "rival-two", "notes"} {
-		if _, err := open.inventory.Assign(ctx, "laptop", m); err != nil {
-			t.Fatal(err)
-		}
-	}
-
-	said := answered(t, func() error { return assignCommand(ctx, "unassign", []string{"laptop", "notes"}) })
-
-	if _, _, err := planFor(ctx, open, "laptop"); err == nil || !unresolvable(err) {
-		t.Fatalf("laptop resolves with two claimants of one seat: %v", err)
-	}
-	if n := strings.Count(said, "laptop does not resolve now"); n != 1 {
-		t.Errorf("the answer says laptop does not resolve %d times, want once:\n%s", n, said)
-	}
-	if strings.Contains(said, "is left out of the rest of the mesh") {
-		t.Errorf("the answer carries a line from a read that is not its resolution:\n%s", said)
-	}
-}
-
-func TestAnUnassignThatLeavesItsNodeResolvedSaysNothingOfIt(t *testing.T) {
-	open := aMesh(t)
-	ctx := t.Context()
-	aProviderAndItsConsumer(t, open)
-	if _, err := assign(ctx, open, "laptop", "db", "app"); err != nil {
-		t.Fatal(err)
-	}
-	said, err := unassign(ctx, open, "laptop", "app")
-	if err != nil {
-		t.Fatal(err)
-	}
-	if _, _, err := planFor(ctx, open, "laptop"); err != nil {
-		t.Fatal(err)
-	}
-	if strings.Contains(said, "does not resolve") || strings.Contains(said, "could not be read") {
-		t.Errorf("a node that resolves is said not to:\n%s", said)
-	}
-}
-
-func TestAnAssignThatLeavesItsNodeUnresolvedSaysOnlyThePlansRefusal(t *testing.T) {
-	open := aMesh(t)
-	ctx := t.Context()
-	twoRivalsAndANote(t, open)
-	if _, err := assign(ctx, open, "laptop", "rival-one"); err != nil {
-		t.Fatal(err)
-	}
-	// Kept and not resolvable: a second claimant of the seat, which assignment keeps.
-	said, err := assign(ctx, open, "laptop", "rival-two")
-	if err == nil {
-		t.Fatalf("two claimants of one node seat resolved:\n%s", said)
-	}
-	_, _, planErr := planFor(ctx, open, "laptop")
-	if planErr == nil || planErr.Error() != err.Error() {
-		t.Errorf("the act's refusal is not the plan's right after:\nact:  %v\nplan: %v", err, planErr)
-	}
-	if strings.Contains(said, "now has") {
-		t.Errorf("the answer says a seat is now held on a node that does not resolve:\n%s", said)
-	}
-}
-
-// The other readers of the whole mesh still say a machine they leave out, on standard error (novox/hq
-// issue 188); an act sends it elsewhere.
-func TestAMachineLeftOutIsSaidWhereTheContextSays(t *testing.T) {
-	var buf bytes.Buffer
-	sayLeftOut(leftOutSaidBy(context.Background(), &buf), "laptop", errors.New("why"))
-	if buf.String() != "laptop is left out of the rest of the mesh: it does not resolve: why\n" {
-		t.Errorf("said %q", buf.String())
-	}
-	got := answered(t, func() error {
-		sayLeftOut(context.Background(), "laptop", errors.New("why"))
-		return nil
-	})
-	if !strings.Contains(got, "laptop is left out") {
-		t.Errorf("without an act's writer the line did not reach standard error: %q", got)
-	}
-}

cmd/mesh-controller/plan.go

@@ -292,7 +292,7 @@ func theRestOfTheMesh(ctx context.Context, inv *inventory.Inventory,
 		if err != nil {
 			// Said, not skipped: a machine dropped here offers nothing and holds nothing as far
 			// as every other machine's plan can tell (novox/hq issue 188).
-			sayLeftOut(ctx, o.node.Name, err)
+			fmt.Fprintf(os.Stderr, "%s is left out of the rest of the mesh: it does not resolve: %v\n", o.node.Name, err)
 			continue
 		}
 		firstHeld = append(firstHeld, got.Claims...)
@@ -337,7 +337,7 @@ func theRestOfTheMesh(ctx context.Context, inv *inventory.Inventory,
 			// resolved without its offers, and one that consumes them cannot resolve here by
 			// design — that is not the machine being dropped, it is the view being partial.
 			if exclude == "" {
-				sayLeftOut(ctx, o.node.Name, err)
+				fmt.Fprintf(os.Stderr, "%s is left out of the rest of the mesh: it does not resolve: %v\n", o.node.Name, err)
 			}
 			continue
 		}
@@ -347,35 +347,6 @@ func theRestOfTheMesh(ctx context.Context, inv *inventory.Inventory,
 	return world, nil
 }
 
-// leftOutKey carries where theRestOfTheMesh says a machine it leaves out, for an act that answers with
-// its own resolution instead (novox/hq issue 237).
-type leftOutKey struct{}
-
-// leftOutSaidBy is ctx with theRestOfTheMesh's "left out" lines written to w rather than to standard
-// error.
-//
-// **An act's answer is one resolution taken after its write** (novox/hq issue 237, decided 2026-10-11).
-// `assign` read the whole mesh once before its write — to record the seats held by derivation — and that
-// read said, on standard error, that the node did not resolve for lack of the seat the act was about to
-// give it. The controller seat's verb answers with both streams, so the stale line came last, after the
-// act's own "now has it held", and named as its remedy the assignment just made. An act gives io.Discard
-// here: what the node resolves to after the write is said by its own planFor, and every other machine
-// that does not resolve by blockedElsewhere, both read after the write.
-func leftOutSaidBy(ctx context.Context, w io.Writer) context.Context {
-	return context.WithValue(ctx, leftOutKey{}, w)
-}
-
-// sayLeftOut says that a machine is left out of the rest of the mesh, where ctx says to: standard
-// error unless an act said otherwise. Said, not skipped: a machine dropped there offers nothing and
-// holds nothing as far as every other machine's plan can tell (novox/hq issue 188).
-func sayLeftOut(ctx context.Context, node string, err error) {
-	w, ok := ctx.Value(leftOutKey{}).(io.Writer)
-	if !ok {
-		w = os.Stderr
-	}
-	fmt.Fprintf(w, "%s is left out of the rest of the mesh: it does not resolve: %v\n", node, err)
-}
-
 // declarationFor is everything a node would be sent.
 //
 // One place, because there were three and one of them was written before credentials existed and
@@ -947,9 +918,14 @@ func renderingFor(ctx context.Context, open *stores, node string,
 	if err != nil {
 		return catalogue.Rendering{}, inventory.Node{}, err
 	}
+	grantsGroups, err := engineGrantsGroups(ctx, inv, node)
+	if err != nil {
+		return catalogue.Rendering{}, inventory.Node{}, err
+	}
 	return catalogue.Rendering{
 		ReadsHealth:   readsHealth,
 		JudgesRoot:    judgesRoot,
+		GrantsGroups:  grantsGroups,
 		BusMembership: memberships[node],
 		Settings:      settings, Generators: gens, Grants: grants, Needed: needed, Foreseen: foreseen, Ports: ports,
 		Certificate: certificate, Authority: authority, Mesh: private, Names: names,
@@ -982,6 +958,16 @@ func engineJudgesRoot(ctx context.Context, inv *inventory.Inventory, node string
 	return had && stated.Contract >= link.RootContract, nil
 }
 
+// engineGrantsGroups says whether a machine's node-engine reads an access's `grant` (novox/hq ADR 0312), by its own
+// newest statement, for the same reason as engineReadsHealth: an older engine parses strictly.
+func engineGrantsGroups(ctx context.Context, inv *inventory.Inventory, node string) (bool, error) {
+	stated, had, err := inv.HealthOf(ctx, node)
+	if err != nil {
+		return false, err
+	}
+	return had && stated.Contract >= link.GrantContract, nil
+}
+
 // zonesInTheMesh is every zone a module in the mesh declares, where the mesh placed it (novox/hq ADR
 // 0199): the zone settled from that node's settings, the node's private address, the port the
 // answering listen is published on there.
@@ -1780,43 +1766,28 @@ func (l *unheldLogger) log(node string, unheld []catalogue.Unheld) {
 // which includes every one of a module just assigned — and each now met that was not. Nothing about
 // any other node, and nothing that was already true before the act.
 func unheldChange(shelf map[string]catalogue.Manifest, node string, before, after []string) []string {
-	return unheldChangeTo(shelf, node, before, after, unheldOver(shelf, node, after))
-}
-
-// unheldOver is the node's unmet seat dependencies judged over a set of module names alone.
-func unheldOver(shelf map[string]catalogue.Manifest, node string, names []string) []catalogue.Unheld {
-	var set []catalogue.Manifest
-	for _, n := range names {
-		if m, known := shelf[n]; known {
-			set = append(set, m)
+	judge := func(names []string) map[string]catalogue.Unheld {
+		var set []catalogue.Manifest
+		for _, n := range names {
+			if m, known := shelf[n]; known {
+				set = append(set, m)
+			}
 		}
+		out := map[string]catalogue.Unheld{}
+		for _, u := range catalogue.UnheldDependencies(shelf, node, set, nil) {
+			out[u.Module+" "+u.Seat] = u
+		}
+		return out
 	}
-	return catalogue.UnheldDependencies(shelf, node, set, nil)
-}
-
-// unheldChangeTo is unheldChange with the node's dependencies as they now stand given: `now` is what
-// the act's one resolution after its write says is unmet, and `after` the modules that resolution has
-// on the node (novox/hq issue 237). A line about how things stand after the act is never judged from
-// anything else, so it cannot disagree with `plan` for the node.
-func unheldChangeTo(shelf map[string]catalogue.Manifest, node string, before, after []string,
-	now []catalogue.Unheld) []string {
-	key := func(u catalogue.Unheld) string { return u.Module + " " + u.Seat }
-	was := map[string]catalogue.Unheld{}
-	for _, u := range unheldOver(shelf, node, before) {
-		was[key(u)] = u
-	}
-	is := map[string]catalogue.Unheld{}
-	for _, u := range now {
-		is[key(u)] = u
-	}
+	was, now := judge(before), judge(after)
 	var lines []string
-	for _, k := range sortedNames(is) {
+	for _, k := range sortedNames(now) {
 		if _, already := was[k]; !already {
-			lines = append(lines, "but "+is[k].String())
+			lines = append(lines, "but "+now[k].String())
 		}
 	}
 	for _, k := range sortedNames(was) {
-		if _, still := is[k]; still {
+		if _, still := now[k]; still {
 			continue
 		}
 		u := was[k]

cmd/mesh-controller/replay237_test.go

@@ -1,85 +0,0 @@
-package main
-
-import (
-	"bytes"
-	"io"
-	"os"
-	"strings"
-	"testing"
-
-	"github.com/novox/mesh-controller/internal/catalogue"
-)
-
-// TestReplay237 replays novox/hq issue 237 (2026-10-04): a workstation already ran a module that
-// depends on a node seat nothing there held, and the module holding that seat was assigned to it. The
-// answer said the seat was now held, and then that the workstation was left out of the rest of the mesh
-// for lack of it, naming as the remedy the assignment just made. `plan` for the node, right after,
-// resolved. The outcome asserted: every line of the answer, as the controller seat's verb gives it
-// (standard output, then standard error), agrees with `plan` for the node right after the act. Written
-// with only what the controller had before its fix — register, assign's command, planFor — so it is laid
-// over the commit before.
-func TestReplay237(t *testing.T) {
-	open := aMesh(t)
-	ctx := t.Context()
-	register(t, open, aContainer("web"))
-	register(t, open, catalogue.Manifest{Module: "docker", Version: "1",
-		Claims: []catalogue.Claim{{Name: catalogue.ContainerRuntimeSeat, Scope: catalogue.ScopeNode}}})
-	// Already on the node, from before the rule refused it: the node does not resolve until the
-	// holder comes.
-	if _, err := open.inventory.Assign(ctx, "laptop", "web"); err != nil {
-		t.Fatal(err)
-	}
-
-	said := answered(t, func() error { return assignCommand(ctx, "assign", []string{"laptop", "docker"}) })
-
-	if _, _, err := planFor(ctx, open, "laptop"); err != nil {
-		t.Fatalf("laptop does not resolve right after the act: %v\nthe answer was:\n%s", err, said)
-	}
-	if !strings.Contains(said, "web on laptop now has "+catalogue.ContainerRuntimeSeat+" held") {
-		t.Errorf("the answer does not say the seat is now held:\n%s", said)
-	}
-	for _, not := range []string{"laptop is left out", "does not resolve", "which nothing on laptop holds"} {
-		if strings.Contains(said, not) {
-			t.Errorf("the answer says %q, which `plan` right after contradicts:\n%s", not, said)
-		}
-	}
-}
-
-// answered is what a command says as the controller seat's verb answers it: standard output, then
-// standard error (answerOf).
-func answered(t *testing.T, f func() error) string {
-	t.Helper()
-	read := func(w **os.File) (func() string, error) {
-		old := *w
-		r, pw, err := os.Pipe()
-		if err != nil {
-			return nil, err
-		}
-		*w = pw
-		got := make(chan string)
-		go func() {
-			var buf bytes.Buffer
-			_, _ = io.Copy(&buf, r)
-			got <- buf.String()
-		}()
-		return func() string {
-			_ = pw.Close()
-			*w = old
-			return <-got
-		}, nil
-	}
-	stdout, err := read(&os.Stdout)
-	if err != nil {
-		t.Fatal(err)
-	}
-	stderr, err := read(&os.Stderr)
-	if err != nil {
-		t.Fatal(err)
-	}
-	runErr := f()
-	said := stdout() + stderr()
-	if runErr != nil {
-		t.Fatalf("%v\n%s", runErr, said)
-	}
-	return said
-}

go.mod

@@ -35,4 +35,4 @@ require (
 // committed. Every build (the build agent's `go build`, the Dockerfile) compiles from vendor/ and
 // fetches nothing; go refuses to build when vendor/ and this file disagree, so a pin moved without
 // `go mod vendor` fails loudly, at once, everywhere.
-replace github.com/novox/mesh-host => git.novox.be/novox/mesh-host v0.0.0-20261011092230-20d5af9b2d5f
+replace github.com/novox/mesh-host => git.novox.be/novox/mesh-host v0.0.0-20261012112256-3f7f797168d3

go.sum

@@ -1,5 +1,5 @@
-git.novox.be/novox/mesh-host v0.0.0-20261011092230-20d5af9b2d5f h1:8N5OW2mdTNIck2pe4EciTYX5NsrPsHrTLENGNIWYNTU=
-git.novox.be/novox/mesh-host v0.0.0-20261011092230-20d5af9b2d5f/go.mod h1:tcTK4LMs1d6JpZUwy3hSHMFG/MIuDr/XFs7/nbeaW/c=
+git.novox.be/novox/mesh-host v0.0.0-20261012112256-3f7f797168d3 h1:VpH8CesuBOo7k8GcXZq1eRUfbvUoktfmcUynI5N3IFQ=
+git.novox.be/novox/mesh-host v0.0.0-20261012112256-3f7f797168d3/go.mod h1:tcTK4LMs1d6JpZUwy3hSHMFG/MIuDr/XFs7/nbeaW/c=
 git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261010191001-33917f91ac3c h1:l5onJwoIeH8yE/PjVlEeoPyXBsHp2NQiWLllz2fwX7s=
 git.novox.be/novox/mesh-sdk/go v0.1.14-0.20261010191001-33917f91ac3c/go.mod h1:GFuZUElBZ9A++mxgIKo97aXXo+kV0uJ/UkbhQPPIbrY=
 github.com/antithesishq/antithesis-sdk-go v0.7.0-default-no-op h1:Z/MZK75wC/NSrkgqeNIa7jexam9uWzhLmFTSCPI/kn0=

internal/catalogue/declaration.go

@@ -246,6 +246,11 @@ type Rendering struct {
 	// statement's contract is link.RootContract or later). To an older, strict engine the field is not
 	// sent, and the account it names is not judged — which the self-check says, as not judged.
 	JudgesRoot bool
+
+	// GrantsGroups says this machine's node-engine reads an access's `grant` (novox/hq ADR 0312: its statement's
+	// contract is link.GrantContract or later). To an older, strict engine the field is not sent, nor the
+	// runtime's restarts on it, and a read-write access is reached as before: by whoever owns the path.
+	GrantsGroups bool
 }
 
 // RootField is a user resource's field saying the account must never become root without a person
@@ -543,6 +548,9 @@ func (r Resolution) compose(with Rendering, owner map[string]string,
 	}
 
 	var out []map[string]any
+	// The read-write accesses each module grants its tools' account, by module (novox/hq ADR 0312): the runtime
+	// that runs as that account is restarted on them.
+	grantedToTools := map[string][]string{}
 	for _, m := range r.Modules {
 		if with.Adopted && m.Filtering != nil {
 			// Nothing of a module that loads a filter, on an adopted node: its table would drop
@@ -1115,6 +1123,13 @@ func (r Resolution) compose(with Rendering, owner map[string]string,
 			out = append(out, copied)
 		}
 
+		// **A read-write access grants its path's group to what runs this module's code** (novox/hq ADR 0312):
+		// the containers composed above that mount it, and the account its tools run as. Only to an engine that
+		// reads the field.
+		if with.GrantsGroups {
+			grantedToTools[m.Module] = grantAccesses(out, owner, m.Module, r.toolsAccount(m, with))
+		}
+
 		// **What only the mesh knows, where this module asked for it.** The graph is the control
 		// plane's; making a name resolve is the module's software. Emitted as ordinary files under
 		// this module's name, so they are applied, reported and removed exactly as anything else
@@ -1141,6 +1156,12 @@ func (r Resolution) compose(with Rendering, owner map[string]string,
 		}
 		owner[fmt.Sprint(process["id"])] = RuntimeModule
 		out = append(out, process)
+		// Restarted when an access moved its account's groups, so its process holds them (novox/hq ADR 0312 §6).
+		for _, m := range r.Modules {
+			if m.RunsAs == "" {
+				restartOnGrants(process, grantedToTools[m.Module])
+			}
+		}
 		// And a runtime of its own for each module of its own account, after it (novox/hq ADR 0259 §8).
 		owns, err := r.ownRuntimes(with)
 		if err != nil {
@@ -1149,6 +1170,7 @@ func (r Resolution) compose(with Rendering, owner map[string]string,
 		for _, p := range owns {
 			id := fmt.Sprint(p["id"])
 			owner[id] = strings.TrimSuffix(id, "."+OwnRuntimeID())
+			restartOnGrants(p, grantedToTools[owner[id]])
 			out = append(out, p)
 		}
 		// What each module's bundles are given is read as the account the runtime runs as — not what a

internal/catalogue/grants.go

@@ -0,0 +1,134 @@
+package catalogue
+
+import (
+	"fmt"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+// A read-write access grants the path's own group to what runs the module's code (novox/hq ADR 0312, issue 537).
+//
+// **The controller says who; the node-engine reads which group.** Which group owns the operator's path is a fact
+// of the machine the controller cannot know, and the path is never changed (§2): so each read-write access
+// reaches a machine naming the identities its module's code runs as, and the node-engine reads the path's group
+// at apply and grants it to them. Two kinds of identity run a module's code here:
+//
+//   - each of its containers that mounts the path — the source of one of its volumes is the path, or below it —
+//     which gains the group as a supplementary group of its process and is recreated with it;
+//   - the account its tools run as, where it has a tools bundle the machine's runtime loads: the operator's
+//     account the runtime runs as, or the module's own account for a module served by a runtime of its own
+//     (ADR 0259 §8). That runtime names the access under its `restart-on`, so it is restarted when the access
+//     moved the account's groups, and its new process holds the group with no new login (§6).
+//
+// A read access grants nothing (§3): it is sent as before. A read-write access whose module runs nothing here is
+// sent an empty grant, so the node-engine still states it unhealthy while its group cannot write (§2).
+//
+// **Only to an engine that reads it.** An older node-engine parses strictly and refuses a whole declaration for a
+// field it does not know; the field and the restarts it brings are composed only where the engine's statement
+// says link.GrantContract or later (Rendering.GrantsGroups).
+
+// GrantField is an access's field naming who its path's group is granted to (novox/hq ADR 0312).
+const GrantField = "grant"
+
+// toolsAccount is the account module m's tools run as on this machine, or empty where they run nowhere as one:
+// no runtime here, no bundle it loads, a module left out of an adopted machine's declaration, or a runtime
+// running as root on a machine with no account.
+func (r Resolution) toolsAccount(m Manifest, with Rendering) string {
+	if !r.runtimeHere() || (with.Adopted && m.Filtering != nil) {
+		return ""
+	}
+	loads := false
+	for _, b := range m.Bundles {
+		if len(b.Loads) > 0 {
+			loads = true
+		}
+	}
+	if !loads {
+		return ""
+	}
+	if m.RunsAs != "" {
+		return m.RunsAs
+	}
+	return r.Account
+}
+
+// grantAccesses writes the grant of every read-write access of module, among the resources composed so far: the
+// module's containers that mount the access's path, and account when it is not empty. The ids of the accesses
+// that grant to account, for the runtime that runs as it to be restarted on.
+func grantAccesses(out []map[string]any, owner map[string]string, module, account string) []string {
+	var containers []map[string]any
+	for _, res := range out {
+		if res["type"] == "container" && owner[fmt.Sprint(res["id"])] == module {
+			containers = append(containers, res)
+		}
+	}
+	var toAccount []string
+	for _, res := range out {
+		if res["type"] != "access" || owner[fmt.Sprint(res["id"])] != module || res["mode"] != AccessReadWrite {
+			continue
+		}
+		path, _ := res["path"].(string)
+		grant := map[string]any{}
+		var mounting []any
+		for _, c := range containers {
+			if mounts(c, path) {
+				mounting = append(mounting, fmt.Sprint(c["id"]))
+			}
+		}
+		if len(mounting) > 0 {
+			grant["containers"] = mounting
+		}
+		if account != "" {
+			grant["account"] = account
+			toAccount = append(toAccount, fmt.Sprint(res["id"]))
+		}
+		res[GrantField] = grant
+	}
+	sort.Strings(toAccount)
+	return toAccount
+}
+
+// mounts says whether a container mounts path, or something below it, from the machine. A path that merely
+// begins with the same letters — /storage/media2 beside /storage/media — is another path. A read-only mount of a
+// read-write access still counts: the module declared the access read-write, the engine grants the group to what
+// mounts it, and a read-only mount only means that container chose not to write through it.
+func mounts(container map[string]any, path string) bool {
+	volumes, _ := container["volumes"].([]any)
+	path = filepath.Clean(path)
+	for _, v := range volumes {
+		s, ok := v.(string)
+		if !ok {
+			continue
+		}
+		source, _, _ := strings.Cut(s, ":")
+		if !strings.HasPrefix(source, "/") {
+			continue // a named volume: the runtime's, not the operator's path
+		}
+		source = filepath.Clean(source)
+		if source == path || strings.HasPrefix(source, path+"/") {
+			return true
+		}
+	}
+	return false
+}
+
+// restartOnGrants adds to a runtime process's restart-on the accesses that grant to the account it runs as, so it
+// is restarted to hold a group the account was put in or taken out of (novox/hq ADR 0312 §6).
+func restartOnGrants(process map[string]any, ids []string) {
+	if process == nil || len(ids) == 0 {
+		return
+	}
+	restarts, _ := process["restart-on"].([]any)
+	seen := map[string]bool{}
+	for _, id := range restarts {
+		seen[fmt.Sprint(id)] = true
+	}
+	for _, id := range ids {
+		if !seen[id] {
+			restarts = append(restarts, id)
+			seen[id] = true
+		}
+	}
+	process["restart-on"] = restarts
+}

internal/catalogue/grants_test.go

@@ -0,0 +1,174 @@
+package catalogue
+
+import (
+	"encoding/json"
+	"fmt"
+	"testing"
+
+	"github.com/novox/mesh-host/validate"
+)
+
+// Defends novox/hq ADR 0312 and issue 537 on the controller's side: each read-write access reaches the machine
+// naming who its path's group is granted to — the module's containers that mount it, and the account its tools
+// run as — and the tool runner is restarted on it; a read access grants nothing; and none of it is sent to a
+// node-engine older than the field, which would refuse the whole declaration.
+
+const anImage = "x@sha256:1111111111111111111111111111111111111111111111111111111111111111"
+
+// anImporter files into one library it writes and reads another: a container mounting both, a step mounting
+// neither, and tools served by the machine's runtime.
+func anImporter(t *testing.T) Manifest {
+	t.Helper()
+	m := aToolsModule(t, "importer", "tools/index.js")
+	m.Accesses = []Access{
+		{ID: "music", Path: "/storage/media/music", Mode: AccessReadWrite},
+		{ID: "movies", Path: "/storage/media/movies", Mode: AccessRead},
+	}
+	m.Resources = []map[string]any{
+		{"id": "app", "type": "container", "name": "importer", "image": anImage,
+			"volumes": []any{"${access:music}/incoming:/music", "${access:movies}:/movies:ro"}},
+		{"id": "sidecar", "type": "container", "name": "importer-sidecar", "image": anImage},
+	}
+	return m
+}
+
+func composeImporter(t *testing.T, r Resolution, with Rendering) map[string]map[string]any {
+	t.Helper()
+	with.Needed = map[string]map[string]string{RuntimeModule: {"broker": "sealed-credential"}}
+	with.ArtifactStore = "anchor.internal:5101"
+	out, err := r.Declaration(with)
+	if err != nil {
+		t.Fatal(err)
+	}
+	// What the node-engine this controller pins would make of it: nothing refused.
+	body, err := json.Marshal(map[string]any{"declaration": validate.Version, "resources": out})
+	if err != nil {
+		t.Fatal(err)
+	}
+	if problems := validate.Declaration(body); len(problems) > 0 {
+		t.Fatalf("composed into something the node-engine refuses: %v", problems)
+	}
+	return byID(out)
+}
+
+func TestAReadWriteAccessNamesTheContainersThatMountItAndTheToolsAccount(t *testing.T) {
+	r := Resolution{Node: "ace", Account: "jochen", Modules: []Manifest{anImporter(t), theRuntime(t)}}
+	got := composeImporter(t, r, Rendering{GrantsGroups: true})
+
+	music := got["importer."+AccessID("/storage/media/music")]
+	if music == nil {
+		t.Fatalf("no access resource for the library: %v", keysOf(got))
+	}
+	grant, _ := music[GrantField].(map[string]any)
+	if fmt.Sprint(grant["containers"]) != "[importer.app]" || grant["account"] != "jochen" {
+		t.Errorf("the read-write access grants %v; want the container that mounts it and the tools' account", grant)
+	}
+	// A read access grants nothing (§3).
+	if movies := got["importer."+AccessID("/storage/media/movies")]; movies[GrantField] != nil {
+		t.Errorf("a read access names a grant: %v", movies[GrantField])
+	}
+	// The tool runner is restarted when the access moved its account's groups (§6).
+	runtime := got[RuntimeModule+"."+RuntimeProcessID()]
+	found := false
+	for _, id := range runtime["restart-on"].([]any) {
+		if id == "importer."+AccessID("/storage/media/music") {
+			found = true
+		}
+	}
+	if !found {
+		t.Errorf("the tool runner is not restarted on the access that grants its account: %v", runtime["restart-on"])
+	}
+}
+
+func TestAModuleOfItsOwnAccountIsGrantedAsThatAccount(t *testing.T) {
+	m := anImporter(t)
+	m.RunsAs = "importer"
+	m.OwnSecrets = OwnSecrets{"broker": {Path: "/var/lib/mesh/importer/broker"}}
+	runtime := theRuntime(t)
+	runtime.Bundles[0].Binary = "node-tools"
+	r := Resolution{Node: "ace", Account: "jochen", Modules: []Manifest{m, runtime}}
+	with := Rendering{GrantsGroups: true}
+	with.Needed = map[string]map[string]string{RuntimeModule: {"broker": "sealed"}, "importer": {"broker": "sealed"}}
+	with.ArtifactStore = "anchor.internal:5101"
+	out, err := r.Declaration(with)
+	if err != nil {
+		t.Fatal(err)
+	}
+	got := byID(out)
+	grant, _ := got["importer."+AccessID("/storage/media/music")][GrantField].(map[string]any)
+	if grant["account"] != "importer" {
+		t.Errorf("the access grants %v; want the module's own account", grant)
+	}
+	own := got["importer."+OwnRuntimeID()]
+	if fmt.Sprint(own["restart-on"]) == "" || !restartsOnIt(own["restart-on"], "importer."+AccessID("/storage/media/music")) {
+		t.Errorf("the module's own runtime is not restarted on its access: %v", own["restart-on"])
+	}
+	if restartsOnIt(got[RuntimeModule+"."+RuntimeProcessID()]["restart-on"], "importer."+AccessID("/storage/media/music")) {
+		t.Error("the machine's runtime is restarted on an access of a module it does not serve")
+	}
+}
+
+func TestAModuleThatRunsNothingHereSendsAnEmptyGrant(t *testing.T) {
+	m := mod("spool", nil, nil, nil)
+	m.Accesses = []Access{{Path: "/storage/downloads", Mode: AccessReadWrite}}
+	out, err := Resolution{Node: "ace", Account: "jochen", Modules: []Manifest{m}}.Declaration(Rendering{GrantsGroups: true})
+	if err != nil {
+		t.Fatal(err)
+	}
+	grant, has := byID(out)["spool."+AccessID("/storage/downloads")][GrantField].(map[string]any)
+	if !has || len(grant) != 0 {
+		t.Errorf("a read-write access of a module running nothing here is sent %v (sent %v); want an empty grant, "+
+			"so its group is still judged", grant, has)
+	}
+}
+
+func TestNoGrantIsSentToAnEngineOlderThanTheField(t *testing.T) {
+	r := Resolution{Node: "ace", Account: "jochen", Modules: []Manifest{anImporter(t), theRuntime(t)}}
+	got := composeImporter(t, r, Rendering{})
+	for id, res := range got {
+		if _, has := res[GrantField]; has {
+			t.Errorf("%s names a grant to an engine that does not read it", id)
+		}
+	}
+	if restartsOnIt(got[RuntimeModule+"."+RuntimeProcessID()]["restart-on"], "importer."+AccessID("/storage/media/music")) {
+		t.Error("the tool runner is restarted on an access an older engine grants nothing for")
+	}
+}
+
+func restartsOnIt(list any, want string) bool {
+	items, _ := list.([]any)
+	for _, i := range items {
+		if fmt.Sprint(i) == want {
+			return true
+		}
+	}
+	return false
+}
+
+func keysOf(m map[string]map[string]any) []string {
+	var out []string
+	for k := range m {
+		out = append(out, k)
+	}
+	return out
+}
+
+// Only a container that mounts the access's path, or below it, is named: a path that begins with the same letters is
+// another path. A read-only mount of a read-write access is still named — the access is read-write, and the grant
+// follows what mounts it, not how.
+func TestOnlyAContainerMountingThePathIsNamedReadOnlyIncluded(t *testing.T) {
+	m := mod("library", nil, nil, nil)
+	m.Accesses = []Access{{ID: "media", Path: "/storage/media", Mode: AccessReadWrite}}
+	m.Resources = []map[string]any{
+		{"id": "beside", "type": "container", "name": "beside", "image": anImage, "volumes": []any{"/storage/media2:/x"}},
+		{"id": "reader", "type": "container", "name": "reader", "image": anImage, "volumes": []any{"${access:media}:/media:ro"}},
+	}
+	out, err := Resolution{Node: "ace", Modules: []Manifest{m}}.Declaration(Rendering{GrantsGroups: true})
+	if err != nil {
+		t.Fatal(err)
+	}
+	grant, _ := byID(out)["library."+AccessID("/storage/media")][GrantField].(map[string]any)
+	if fmt.Sprint(grant["containers"]) != "[library.reader]" {
+		t.Errorf("the access grants %v; want the read-only mount and not /storage/media2", grant)
+	}
+}

internal/link/protocol.go

@@ -436,6 +436,12 @@ const ReadinessContract = 2
 // parses strictly and would refuse the whole declaration for it.
 const RootContract = 3
 
+// GrantContract is the statement of an engine that also reads an access's `grant` (novox/hq ADR 0312): it grants a
+// read-write access's path group to the containers and the account the grant names, takes it back, and states the
+// access unhealthy while the group cannot write. Only to such an engine is the field sent: an older one parses
+// strictly and would refuse the whole declaration for it.
+const GrantContract = 4
+
 // ReasonRoot starts the reason of an account verdict that found a way to root (ADR 0266); the node-engine's
 // own words (mesh-host internal/accounts ReasonRoot).
 const ReasonRoot = "can become root without a person"
@@ -487,6 +493,11 @@ const KindAccount = "account"
 // ReasonUsedAsFound.
 const KindDirectory = "directory"
 
+// KindAccess is a read-write access that grants its path's group (novox/hq ADR 0312): healthy while the group may
+// write the path, unhealthy while it cannot — the operator's to decide, since the mesh changes nothing on the path
+// — or while the path is owned by a group that is never granted. The node-engine's own (mesh-host internal/link).
+const KindAccess = "access"
+
 // ReasonUsedAsFound starts the reason of a directory used as found.
 const ReasonUsedAsFound = "used as found:"
 

testdata/beside/CAPTURED

@@ -8,7 +8,7 @@ private addresses. That is acceptable while mesh-controller is private; if it ev
 a second place to clean besides the catalogue itself.
 
 mesh-catalog  b9de001833b1b61b297182b8e3bcdae1cbdeace9  modules/*/module.json, modules/nats/Dockerfile
-mesh-host     a76baa4b47f07a8b2bab065603414530bd02b53a  examples/foundation-first-node-nats.lock
+mesh-host     3f7f797168d33ec22241bdd6ef2c64de86eea914  examples/foundation-first-node-nats.lock
 mesh-sdk      33917f91ac3cc213b879b32f3c70e2aa70395f98  conformance/events/module-event.json
 
 To move them, from this repository's root, with the two repositories checked out beside it:

testdata/store-tests

@@ -22,7 +22,3 @@
 ./cmd/mesh-controller TestAWalkEndedByCancelOrClearIsSaidEnded
 ./cmd/mesh-controller TestAWalkRestartedByARebuildIsSaidStarted
 ./cmd/mesh-controller TestAWalkStoppedByHandAndRetriedEndsFailedWhenItFailsAgain
-./cmd/mesh-controller TestReplay237
-./cmd/mesh-controller TestAnUnassignThatLeavesItsNodeUnresolvedSaysSoOnceInItsAnswer
-./cmd/mesh-controller TestAnUnassignThatLeavesItsNodeResolvedSaysNothingOfIt
-./cmd/mesh-controller TestAnAssignThatLeavesItsNodeUnresolvedSaysOnlyThePlansRefusal

vendor/github.com/novox/mesh-host/internal/declaration/declaration.go

@@ -464,6 +464,35 @@ type Access struct {
 	Path string `json:"path"`
 	// Mode is how this module reaches the path: read or read-write. Absent narrows to read.
 	Mode string `json:"mode,omitempty"`
+
+	// Grant is who the path's own group is granted to, for a read-write access (novox/hq ADR 0312 §1): the
+	// identities the module's code runs as. The controller says who; the node-engine reads which group owns
+	// the path when it applies, because only the machine knows, and never changes the path (§2). Absent is a
+	// controller older than the grant, or an access that grants nothing — and a read access always is one (§3).
+	Grant *AccessGrant `json:"grant,omitempty"`
+}
+
+// AccessGrant is the identities a read-write access grants its path's group to (novox/hq ADR 0312 §1).
+type AccessGrant struct {
+	// Containers are the module's containers that mount the path, by id: each is created with the group as a
+	// supplementary group of its process, and recreated when the group moves (§6).
+	Containers []string `json:"containers,omitempty"`
+	// Account is the account that runs the module's tools: put in the group as an account group, as ADR 0252
+	// §1 puts one, and taken out again as §3 takes back (§5). Empty for a module whose code runs nowhere as
+	// an account.
+	Account string `json:"account,omitempty"`
+}
+
+// UnmarshalJSON reads a grant as strictly as a resource is read: a field the engine does not know is a
+// thing the controller believes it asked for, and is refused rather than ignored.
+func (g *AccessGrant) UnmarshalJSON(raw []byte) error {
+	type plain AccessGrant
+	var p plain
+	if err := strictDecode(raw, &p); err != nil {
+		return fmt.Errorf("a grant: %w", err)
+	}
+	*g = AccessGrant(p)
+	return nil
 }
 
 func (a *Access) Identity() string { return a.ID }
@@ -482,6 +511,24 @@ func (a *Access) validate(where string, _ bool) []string {
 		problems = append(problems, fmt.Sprintf(
 			"%s: an access is %q or %q, not %q", where, AccessRead, AccessReadWrite, a.Mode))
 	}
+	if a.Grant != nil && a.Mode != AccessReadWrite {
+		// A read access reads as any account may, and gains no group (novox/hq ADR 0312 §3).
+		problems = append(problems, where+": a read access grants nothing, and this one names a grant; "+
+			"only a read-write access grants its path's group (novox/hq ADR 0312 §3)")
+	}
+	if a.Grant != nil {
+		for _, id := range a.Grant.Containers {
+			if id == "" {
+				problems = append(problems, where+": a grant names a container with no id")
+			}
+		}
+		if a.Grant.Account != "" && !accountName.MatchString(a.Grant.Account) {
+			// Handed to id, usermod and gpasswd as an argument: a name starting with a dash would be read as an
+			// option by each of them.
+			problems = append(problems, fmt.Sprintf("%s: a grant's account is an account's name — letters, digits, "+
+				"dots, underscores and dashes, not starting with a dash — and %q is not one", where, a.Grant.Account))
+		}
+	}
 	return problems
 }
 
@@ -1668,6 +1715,7 @@ func parse(raw []byte, allowActions bool) (*Declaration, error) {
 		d.Resources = append(d.Resources, resource)
 	}
 	problems = append(problems, checkWhileStopped(d.Resources)...)
+	problems = append(problems, checkGrants(d.Resources)...)
 	problems = append(problems, checkAdoption(env.Adoption, d.Resources, allowActions)...)
 	problems = append(problems, checkReplaces(d.Resources)...)
 	if env.Adoption == nil {
@@ -1732,6 +1780,36 @@ func checkWhileStopped(resources []Resource) []string {
 	return problems
 }
 
+// accountName is what a grant's account may be: the portable account name the user tools take, optionally ending
+// in `$`, never starting with a dash.
+var accountName = regexp.MustCompile(`^[A-Za-z0-9_.][A-Za-z0-9_.-]*\$?$`)
+
+// checkGrants judges each access's grant against the whole declaration (novox/hq ADR 0312): a container it
+// names is a container of this declaration, as a maintenance window's are. A grant to a container the machine
+// is not told about would be a group given to nothing, said as granted.
+func checkGrants(resources []Resource) []string {
+	containers := map[string]bool{}
+	for _, r := range resources {
+		if r.Kind() == TypeContainer {
+			containers[r.Identity()] = true
+		}
+	}
+	var problems []string
+	for _, r := range resources {
+		a, ok := r.(*Access)
+		if !ok || a.Grant == nil {
+			continue
+		}
+		for _, id := range a.Grant.Containers {
+			if id != "" && !containers[id] {
+				problems = append(problems, fmt.Sprintf("resource %q: its grant names %q, and this declaration "+
+					"has no container by that id", a.ID, id))
+			}
+		}
+	}
+	return problems
+}
+
 func strictDecode(raw []byte, into any) error {
 	// DisallowUnknownFields is the whole point rather than strictness for its own sake: a
 	// field the host does not know is a thing the control plane believes it asked for.

vendor/modules.txt

@@ -78,7 +78,7 @@ github.com/nats-io/nkeys
 # github.com/nats-io/nuid v1.0.1
 ## explicit
 github.com/nats-io/nuid
-# github.com/novox/mesh-host v0.0.0 => git.novox.be/novox/mesh-host v0.0.0-20261011092230-20d5af9b2d5f
+# github.com/novox/mesh-host v0.0.0 => git.novox.be/novox/mesh-host v0.0.0-20261012112256-3f7f797168d3
 ## explicit; go 1.26.0
 github.com/novox/mesh-host/internal/declaration
 github.com/novox/mesh-host/rootsearch
@@ -135,4 +135,4 @@ golang.org/x/text/width
 # golang.org/x/time v0.15.0
 ## explicit; go 1.25.0
 golang.org/x/time/rate
-# github.com/novox/mesh-host => git.novox.be/novox/mesh-host v0.0.0-20261011092230-20d5af9b2d5f
+# github.com/novox/mesh-host => git.novox.be/novox/mesh-host v0.0.0-20261012112256-3f7f797168d3