Say an act's answer from one resolution after its write (issue 237)

assign read the whole mesh before its write, to record the seats held by
derivation, and that read printed on standard error that the node did not
resolve for lack of the seat the act was about to give it. The seat verb
answers with both streams, so the stale line came last and named the
assignment just made as its remedy.

The reads inside an act no longer print 'left out' lines; the node's
unmet seat dependencies and whether it resolves come from one planFor
taken after the write, and every other machine from blockedElsewhere.
unassign now says when its node does not resolve, from the same
resolution.

cmd/mesh-controller/acts.go

@@ -4,6 +4,7 @@ import (
 	"context"
 	"fmt"
 	"github.com/novox/mesh-controller/internal/broker"
+	"io"
 	"slices"
 	"sort"
 	"strings"
@@ -54,6 +55,9 @@ 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})
@@ -125,22 +129,28 @@ 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 != "" {
-			answer += "\n  " + line
+			issued = append(issued, line)
 		}
 	}
-	plan, _, err := planFor(ctx, open, node)
+	// **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
 	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.
@@ -218,6 +228,8 @@ 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
@@ -262,15 +274,22 @@ 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)
-	var left []string
-	for _, a := range assigned {
-		if !slices.Contains(modules, a) {
-			left = append(left, a)
-		}
-	}
-	for _, line := range unheldChange(shelf, node, assigned, left) {
+	after := resolvedAfter(ctx, open, shelf, node)
+	for _, line := range unheldChangeTo(shelf, node, assigned, after.modules, after.unheld) {
 		answer += "\n  " + line
 	}
+	// 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)
+		}
+	}
 	// 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) {
 		answer += "\n  " + line
@@ -278,6 +297,39 @@ 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

@@ -0,0 +1,112 @@
+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).
-			fmt.Fprintf(os.Stderr, "%s is left out of the rest of the mesh: it does not resolve: %v\n", o.node.Name, err)
+			sayLeftOut(ctx, 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 == "" {
-				fmt.Fprintf(os.Stderr, "%s is left out of the rest of the mesh: it does not resolve: %v\n", o.node.Name, err)
+				sayLeftOut(ctx, o.node.Name, err)
 			}
 			continue
 		}
@@ -347,6 +347,35 @@ 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
@@ -1751,28 +1780,43 @@ 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 {
-	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)
-			}
+	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)
 		}
-		out := map[string]catalogue.Unheld{}
-		for _, u := range catalogue.UnheldDependencies(shelf, node, set, nil) {
-			out[u.Module+" "+u.Seat] = u
-		}
-		return out
 	}
-	was, now := judge(before), judge(after)
+	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
+	}
 	var lines []string
-	for _, k := range sortedNames(now) {
+	for _, k := range sortedNames(is) {
 		if _, already := was[k]; !already {
-			lines = append(lines, "but "+now[k].String())
+			lines = append(lines, "but "+is[k].String())
 		}
 	}
 	for _, k := range sortedNames(was) {
-		if _, still := now[k]; still {
+		if _, still := is[k]; still {
 			continue
 		}
 		u := was[k]

cmd/mesh-controller/replay237_test.go

@@ -0,0 +1,85 @@
+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
+}