Look at what a container mounts directly, accept a pre-upgrade label, and write the genesis secret without a newline

Review of the first cut found four things.

A directory mounted into a container is no longer looked inside, not even
for the files this host wrote there. The controller records every
provider's received and contributions file as a plain file under a mounted
directory, so folding those in would have recreated the route proxy — which
re-reads its routes live, by design — on every route change, and killed
every provisioner sidecar, which polls what it receives, mid-reconcile on
every grant. Whether a service reads a file under its directory once or
watches it is the service's; restart-on is how a module says "once", and it
stays the opt-in. Env-files and files mounted directly remain by content.

Genesis wrote the superuser secret as `value\n`; `secret accept` strips the
line ending by design, so the postgres module declared `value` — and with
a mounted file's content in the spec, phase three would have recreated the
store it meant to adopt in place, with the temporary control plane
connected to it. Genesis now writes the value alone. readCredentialFile
tolerated both endings already. Pinned with the bytes the genesis code
path writes, then the module's declaration of the same container: it must
reconcile.

A container carrying a label from before the host folded in what it reads
is accepted rather than recreated, when that label matches the spec as it
used to be computed: what it reads is recorded then, a change is caught
from that record from the next apply on, and the label is renewed at the
next genuine recreate. Recreating them all would have been a restart storm
across the mesh in declaration order, the store first. The trade-off is
stated in the code: a container already stale at upgrade time is not
caught, and could not have been either way.

The record of what a container read is looked up by its name when its
declared id has none — the bundle's `store` becomes `postgres.server` for
the same container — so a change on the day it is adopted still names the
file. The by-target lookup takes the most recently applied record, since
the bundle's record for the same target is never removed by the mesh's.

novox/hq 04-ISSUES/103

internal/apply/apply.go

@@ -1167,14 +1167,13 @@ type inputs struct {
 // — an env-file a predecessor left, the superuser secret genesis writes before any declaration
 // names it — is read, so the digest is the same one the host records when it later writes the
 // same bytes there, and adopting a running store in place stays a reconcile rather than a
-// recreate (bootstrap phase three). Empty when there is nothing readable there: the runtime
-// refuses an absent env-file itself, with a better message than this could give.
+// recreate (bootstrap phase three; genesis writes the value with no line ending for exactly this
+// reason). Empty when there is nothing readable there: the runtime refuses an absent env-file
+// itself, with a better message than this could give.
 func (in inputs) fileDigest(path string) string {
 	if in.known != nil {
-		for _, f := range in.known.FilesUnder(path) {
-			if f.Target == path {
-				return f.Wrote
-			}
+		if f, recorded := in.known.At(string(declaration.TypeFile), path); recorded {
+			return f.Wrote
 		}
 	}
 	info, err := os.Stat(path)
@@ -1193,12 +1192,16 @@ func (in inputs) fileDigest(path string) string {
 //
 //   - every env-file: the runtime reads it once, at create, and `docker restart` hands the
 //     container the same environment it had.
-//   - a file bind-mounted into it, by its content — and, for a directory bind-mounted into it,
-//     every file THIS HOST wrote at or beneath the source: the secrets, bindings and configs it
-//     put under the module's state directories. What else is in a mounted directory is the
-//     service's own data, which changes while it runs and is nothing to recreate it for.
+//   - a file bind-mounted into it, DIRECTLY, by its content: a secret, a credential file.
 //
-// A step is not here: a run-once or scheduled container reads its files when it runs, and
+// **A directory bind-mounted into it is not looked inside**, not even for the files this host
+// wrote there. What a service reads out of a mounted directory, and when, is the service's
+// business: the route proxy re-reads its routes file live and would be recreated on every route
+// change; a provisioner sidecar polls what it receives every few seconds and would be killed
+// mid-reconcile on every grant. A module whose container does read such a file once, at start,
+// says so with restart-on — that is what the field is for, and it stays the opt-in.
+//
+// A step is not here either: a run-once or scheduled container reads its files when it runs, and
 // runs fresh each time. Only a container that stays running holds what it read.
 func (in inputs) reads(r *declaration.Container) map[string]string {
 	if r.RunOnce || r.Schedule != "" {
@@ -1213,15 +1216,9 @@ func (in inputs) reads(r *declaration.Container) map[string]string {
 		if !strings.HasPrefix(src, "/") {
 			continue // a named volume: the runtime's, holding data
 		}
-		if in.known != nil {
-			for _, f := range in.known.FilesUnder(src) {
-				out[f.Target] = f.Wrote
-			}
-		}
-		if _, recorded := out[src]; !recorded {
-			if digest := in.fileDigest(src); digest != "" {
-				out[src] = digest
-			}
+		// fileDigest is empty for a directory, and for anything else that is not a regular file.
+		if digest := in.fileDigest(src); digest != "" {
+			out[src] = digest
 		}
 	}
 	if len(out) == 0 {
@@ -1399,18 +1396,42 @@ func applyContainer(ctx context.Context, r *declaration.Container, run Runner,
 	// already has.
 	reasons := restartedBy(r.RestartOn, changed)
 
+	// What this container was created reading, as last recorded. By its declared id first, and by
+	// its NAME when that id has no record: the bundle's `store` becomes the postgres module's
+	// `postgres.server`, the same container under a new id, and a file change on the day it is
+	// adopted is a real change with a real record — under the old id.
+	wasReading := previous.Reads
+	if previous.ID == "" && in.known != nil {
+		if byName, ok := in.known.At(string(declaration.TypeContainer), r.Name); ok {
+			wasReading = byName.Reads
+		}
+	}
+
 	// Which of the files it reads no longer hold what it was created reading. The spec label says
 	// only that SOMETHING moved; the record of what was read says what — and that is the line a
 	// person needs when a service went stale without a word (novox/hq 04-ISSUES/103).
 	var changedFiles []string
-	for _, path := range sortedKeys(previous.Reads) {
-		if now, still := reads[path]; still && now != previous.Reads[path] {
+	for _, path := range sortedKeys(wasReading) {
+		if now, still := reads[path]; still && now != wasReading[path] {
 			changedFiles = append(changedFiles, path)
 		}
 	}
 
+	// **A container labelled before the host folded in what it reads is accepted, not recreated.**
+	//
+	// Its label is the spec without the file lines. Recreating every such container on the first
+	// apply after the host upgraded would be a restart storm across the mesh in declaration order —
+	// the store first, under everything that uses it. So a label that matches the spec as it used
+	// to be computed is taken as current: what it reads is recorded now, and from the next apply
+	// on a changed file is caught by that record; the label itself is rewritten at the next
+	// genuine recreate. The trade-off, stated: a container that was ALREADY stale when the host
+	// upgraded — created against a file that has since changed — is not caught by this, and could
+	// not be by the alternative either, which recreates it without knowing whether it needed to.
+	legacy := len(reads) > 0 && before.Spec == containerSpecReading(r, in.declares, nil) &&
+		(wasReading == nil || sameReads(wasReading, reads))
+
 	switch {
-	case existed && before.Spec == want && before.Running && len(reasons) == 0:
+	case existed && (before.Spec == want || legacy) && before.Running && len(reasons) == 0:
 		out.Action = "unchanged"
 		return out, nil
 	case existed:
@@ -1478,10 +1499,6 @@ func applyContainer(ctx context.Context, r *declaration.Container, run Runner,
 			}
 		case len(reasons) > 0:
 			out.Detail = "recreated to pick up " + strings.Join(reasons, ", ")
-		case previous.Reads == nil && len(reads) > 0:
-			// A container made before this host kept what it read: whether the files it holds
-			// are the ones on disk cannot be known, so it is recreated once and from now on can.
-			out.Detail = "recreated: what it reads was not on record, so what it holds could not be checked"
 		default:
 			out.Detail = "replaced; a container's configuration is fixed when it is created"
 		}
@@ -1650,6 +1667,20 @@ func restartedBy(restartOn []string, changed map[string]bool) []string {
 	return which
 }
 
+// sameReads is whether two records of what a container reads name the same files holding the
+// same content — a file added, dropped or changed makes them differ.
+func sameReads(a, b map[string]string) bool {
+	if len(a) != len(b) {
+		return false
+	}
+	for path, digest := range a {
+		if b[path] != digest {
+			return false
+		}
+	}
+	return true
+}
+
 func sortedKeys(m map[string]string) []string {
 	keys := make([]string, 0, len(m))
 	for k := range m {

internal/apply/reads_test.go

@@ -132,24 +132,27 @@ func TestAContainerIsRecreatedWhenAMountedSecretChanged(t *testing.T) {
 	}
 }
 
-func TestWhatAServiceWritesInAMountedDirectoryIsNotPartOfWhatItIs(t *testing.T) {
-	// A bind-mounted directory is the service's data: it changes while the service runs, and
-	// recreating for it would restart a database for every row it wrote. What the HOST wrote
-	// under that directory — a config it rendered there — is another matter: the service read
-	// that once, at start.
+func TestAMountedDirectoryIsNotLookedInside(t *testing.T) {
+	// A bind-mounted directory is not part of what a container is — not the data the service
+	// grows in it, and not the files the host itself writes there either. Whether a service reads
+	// a file under its directory once at start or watches it live is the service's business: the
+	// route proxy re-reads its routes live, a provisioner sidecar polls what it receives every few
+	// seconds, and recreating either for a file the host rewrote would kill them for nothing. A
+	// module whose container does read such a file once says so with restart-on, which stays the
+	// opt-in.
 	dir := t.TempDir()
 	state := filepath.Join(dir, "state")
 	config := filepath.Join(state, "config.toml")
-	declare := func(level string) *declaration.Declaration {
+	declare := func(level, restartOn string) *declaration.Declaration {
 		return parseTrusted(t, `{"declaration":1,"resources":[
 		  {"id":"app.state","type":"directory","path":"`+state+`"},
 		  {"id":"app.config","type":"file","path":"`+config+`","content":"level = \"`+level+`\"\n"},
 		  {"id":"app.server","type":"container","name":"app","image":"`+pinned+`",
-		   "volumes":["`+state+`:/var/lib/app"]}
+		   "volumes":["`+state+`:/var/lib/app"]`+restartOn+`}
 		]}`)
 	}
 	m := &machine{containers: map[string]*fakeContainer{}}
-	_, known := applyCarried(t, declare("info"), store.State{}, m, nil)
+	_, known := applyCarried(t, declare("info", ""), store.State{}, m, nil)
 
 	// The service grows its data in the directory it was given.
 	if err := os.WriteFile(filepath.Join(state, "app.db"), []byte("rows"), 0o600); err != nil {
@@ -162,20 +165,112 @@ func TestWhatAServiceWritesInAMountedDirectoryIsNotPartOfWhatItIs(t *testing.T)
 		t.Fatal(err)
 	}
 	m.asked = nil
-	report, known := applyCarried(t, declare("info"), known, m, nil)
+	report, known := applyCarried(t, declare("info", ""), known, m, nil)
 	if m.did("docker rm") || m.did("docker run") || report.Changed() {
 		t.Errorf("a container was recreated for data its service wrote in a mounted directory: %v %+v",
 			m.asked, report.Outcomes)
 	}
 
-	// The host's own config under the same directory changes: that, the service read at start.
+	// The host rewrites its own file under the same directory: still not a reason. The container
+	// did not name it.
 	m.asked = nil
-	report, _ = applyCarried(t, declare("debug"), known, m, nil)
-	if !m.removed("app") || !m.did("docker run") {
-		t.Fatalf("a config the host wrote under a mounted directory changed and the container was not recreated: %v", m.asked)
+	report, known = applyCarried(t, declare("debug", ""), known, m, nil)
+	if m.did("docker rm") || m.did("docker run") {
+		t.Errorf("a container was recreated for a file under a mounted directory it did not name: %v", m.asked)
 	}
-	if o := outcomeOf(report, "app.server"); o.Detail != "recreated: "+config+" changed" {
-		t.Errorf("the recreate did not name the config: %+v", o)
+	if o := outcomeOf(report, "app.config"); o.Action != "updated" {
+		t.Fatalf("the config was not rewritten: %+v", o)
+	}
+
+	// Naming it is what makes it a reason, as before this change.
+	m.asked = nil
+	report, _ = applyCarried(t, declare("trace", `,"restart-on":["app.config"]`), known, m, nil)
+	if !m.removed("app") || !m.did("docker run") {
+		t.Fatalf("a container naming a rewritten file under its mount was not recreated: %v", m.asked)
+	}
+	if o := outcomeOf(report, "app.server"); !strings.Contains(o.Detail, "app.config") {
+		t.Errorf("the recreate did not name why: %+v", o)
+	}
+}
+
+func TestAContainerLabelledBeforeTheHostReadItsFilesIsAcceptedNotRecreated(t *testing.T) {
+	// The first apply after the host upgrades finds every container carrying a label computed
+	// without the file lines. Recreating them all would be a restart storm across the mesh in
+	// declaration order, the store first. A label that matches the spec as it used to be computed
+	// is accepted: what the container reads is recorded now, and from then on a change is caught.
+	dir := t.TempDir()
+	env := filepath.Join(dir, "forge.env")
+	declare := func(port string) *declaration.Declaration {
+		return parseTrusted(t, `{"declaration":1,"resources":[
+		  {"id":"forge.env","type":"file","path":"`+env+`","content":"DATABASE_PORT=`+port+`\n","mode":"0600"},
+		  {"id":"forge.server","type":"container","name":"forge","image":"`+pinned+`","env-file":["`+env+`"]}
+		]}`)
+	}
+	// The machine as the previous host left it: the file written and recorded, the container up
+	// under the label that host computed — the spec with nothing about the file's content.
+	if err := os.WriteFile(env, []byte("DATABASE_PORT=5432\n"), 0o600); err != nil {
+		t.Fatal(err)
+	}
+	d := declare("5432")
+	legacy := containerSpecReading(d.Resources[1].(*declaration.Container), nil, nil)
+	known := store.State{}
+	known.Record(store.Applied{ID: "forge.env", Type: "file", Origin: store.OriginCarried, Target: env,
+		Wrote: digestOf("DATABASE_PORT=5432\n")})
+	known.Record(store.Applied{ID: "forge.server", Type: "container", Origin: store.OriginCarried, Target: "forge"})
+	m := &machine{containers: map[string]*fakeContainer{"forge": {id: "made-by-host", running: true, spec: legacy}}}
+
+	report, known := applyCarried(t, d, known, m, nil)
+	if m.did("docker rm") || m.did("docker run") || report.Changed() {
+		t.Fatalf("a container labelled by the previous host was recreated on upgrade: %v %+v", m.asked, report.Outcomes)
+	}
+	if got, _ := known.Find("forge.server"); got.Reads[env] != digestOf("DATABASE_PORT=5432\n") {
+		t.Fatalf("what the accepted container reads was not recorded: %+v", got)
+	}
+	// Accepted stays accepted: the next pass with nothing moved is quiet too.
+	m.asked = nil
+	report, known = applyCarried(t, d, known, m, nil)
+	if m.did("docker rm") || m.did("docker run") || report.Changed() {
+		t.Fatalf("an accepted container was recreated on the pass after: %v", m.asked)
+	}
+
+	// And a change to the file is caught from the record, and the label is renewed.
+	m.asked = nil
+	report, _ = applyCarried(t, declare("5433"), known, m, nil)
+	if !m.removed("forge") || !m.did("docker run") {
+		t.Fatalf("an accepted container was not recreated when its env-file changed: %v", m.asked)
+	}
+	if o := outcomeOf(report, "forge.server"); o.Detail != "recreated: "+env+" changed" {
+		t.Errorf("the recreate did not name the file: %+v", o)
+	}
+	if m.containers["forge"].spec == legacy {
+		t.Error("the recreated container still carries the legacy label")
+	}
+}
+
+func TestAContainerAdoptedUnderANewIdStillSaysWhichFileChanged(t *testing.T) {
+	// The bundle's `store` becomes the postgres module's `postgres.server`: the same container by
+	// name, under a new id with no record of its own. A file change on that day is a real change,
+	// and the record of what it read is under the old id — by name, it is found.
+	dir := t.TempDir()
+	env := filepath.Join(dir, "store.env")
+	m := &machine{containers: map[string]*fakeContainer{}}
+	raised := parseTrusted(t, `{"declaration":1,"resources":[
+	  {"id":"env","type":"file","path":"`+env+`","content":"PORT=5432\n","mode":"0600"},
+	  {"id":"store","type":"container","name":"mesh-store","image":"`+pinned+`","env-file":["`+env+`"]}
+	]}`)
+	_, known := applyCarried(t, raised, store.State{}, m, nil)
+
+	adopted := parseTrusted(t, `{"declaration":1,"resources":[
+	  {"id":"postgres.env","type":"file","path":"`+env+`","content":"PORT=5433\n","mode":"0600"},
+	  {"id":"postgres.server","type":"container","name":"mesh-store","image":"`+pinned+`","env-file":["`+env+`"]}
+	]}`)
+	m.asked = nil
+	report, _, err := Apply(context.Background(), archHost(t), adopted, known, store.OriginDeclared, m.run, nil, nil)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if o := outcomeOf(report, "postgres.server"); o.Action != "updated" || o.Detail != "recreated: "+env+" changed" {
+		t.Errorf("a container adopted under a new id did not say which file changed: %+v", o)
 	}
 }
 

internal/bootstrap/adopt_in_place_test.go

@@ -0,0 +1,130 @@
+package bootstrap
+
+import (
+	"context"
+	"errors"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-host/internal/apply"
+	"github.com/novox/mesh-host/internal/declaration"
+	"github.com/novox/mesh-host/internal/store"
+)
+
+// Defends phase three's premise (phase3.go): the store genesis raised is adopted by the postgres
+// module IN PLACE — same name, same image, same spec — so the applier reconciles it and never
+// recreates the mesh's memory with the temporary control plane connected to it.
+//
+// The host folds a mounted file's content into the container's spec (novox/hq 04-ISSUES/103), so
+// this now depends on a byte: the superuser file genesis writes and mounts must be the same bytes
+// the module later declares. The module's value is what `secret accept` took — the operator's
+// file with its line ending removed and nothing else (mesh-control, asSupplied). Reproduced before
+// it was fixed: genesis wrote `value\n`, the module wrote `value`, and the store was recreated
+// during install.
+
+// labelled is a runtime that keeps the spec label the host gives a container and hands it back.
+type labelled struct {
+	spec    map[string]string
+	created []string
+	removed []string
+}
+
+func (l *labelled) run(_ context.Context, _ string, args ...string) (string, error) {
+	switch args[0] {
+	case "info":
+		return "27.0\n", nil
+	case "inspect":
+		spec, ok := l.spec[args[len(args)-1]]
+		if !ok {
+			return "", errors.New("no such container")
+		}
+		return "true\t" + spec + "\n", nil
+	case "rm":
+		l.removed = append(l.removed, args[len(args)-1])
+		delete(l.spec, args[len(args)-1])
+	case "run":
+		var name, spec string
+		for i, a := range args {
+			if a == "--name" {
+				name = args[i+1]
+			}
+			if a == "--label" && strings.HasPrefix(args[i+1], "mesh-host.spec=") {
+				spec = strings.TrimPrefix(args[i+1], "mesh-host.spec=")
+			}
+		}
+		l.spec[name] = spec
+		l.created = append(l.created, name)
+		return "made\n", nil
+	}
+	return "", nil
+}
+
+func TestTheStoreGenesisRaisedIsAdoptedInPlaceNotRecreated(t *testing.T) {
+	dir := t.TempDir()
+	secret := filepath.Join(dir, "superuser.secret")
+
+	// The bytes genesis really writes — the code path, not a fixture that agrees with it.
+	if _, made, err := keptOrMade(secret, false); err != nil || !made {
+		t.Fatalf("genesis did not make the superuser secret: made=%v err=%v", made, err)
+	}
+	onDisk, err := os.ReadFile(secret)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	image := "docker.io/library/postgres@sha256:" + strings.Repeat("ab", 32)
+	mounts := `"volumes":["mesh-store-data:/var/lib/postgresql/data","` + secret + `:` + storeSuperuserMount + `:ro"]`
+
+	// The foundation's store, as the produced bundle raises it (RewriteRoot): the file mounted,
+	// declared by nothing — genesis wrote it before there was a declaration to name it.
+	raise, err := declaration.ParseTrusted([]byte(`{"declaration":1,"resources":[
+	  {"id":"` + StoreID + `","type":"container","name":"mesh-store","image":"` + image + `",
+	   "env":{"POSTGRES_PASSWORD_FILE":"` + storeSuperuserMount + `"},` + mounts + `}
+	]}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	runtime := &labelled{spec: map[string]string{}}
+	_, known, err := apply.Apply(context.Background(), arch(t), raise, store.State{}, store.OriginCarried,
+		runtime.run, nil, nil)
+	if err != nil {
+		t.Fatalf("raising the foundation's store: %v", err)
+	}
+	if len(runtime.created) != 1 {
+		t.Fatalf("the store was not raised once: %v", runtime.created)
+	}
+
+	// The postgres module's declaration of the same store: the superuser file as `secret accept`
+	// took it in — its line ending removed and nothing else — then the same container.
+	accepted := strings.TrimRight(string(onDisk), "\r\n")
+	adopt, err := declaration.ParseTrusted([]byte(`{"declaration":1,"resources":[
+	  {"id":"postgres.superuser","type":"file","path":"` + secret + `","content":"` + accepted + `","mode":"0600"},
+	  {"id":"postgres.server","type":"container","name":"mesh-store","image":"` + image + `",
+	   "env":{"POSTGRES_PASSWORD_FILE":"` + storeSuperuserMount + `"},` + mounts + `}
+	]}`))
+	if err != nil {
+		t.Fatal(err)
+	}
+	runtime.created, runtime.removed = nil, nil
+	report, _, err := apply.Apply(context.Background(), arch(t), adopt, known, store.OriginDeclared,
+		runtime.run, nil, nil)
+	if err != nil {
+		t.Fatalf("adopting the store: %v", err)
+	}
+
+	if len(runtime.removed) > 0 || len(runtime.created) > 0 {
+		t.Fatalf("the module's declaration recreated the store genesis raised (removed %v, created %v): "+
+			"the file genesis mounted and the file the module declares are not the same bytes",
+			runtime.removed, runtime.created)
+	}
+	for _, o := range report.Outcomes {
+		if o.ID == "postgres.server" && o.Action != "unchanged" {
+			t.Errorf("the store was not adopted in place: %+v", o)
+		}
+		if o.ID == "postgres.superuser" && o.Action != "unchanged" {
+			t.Errorf("the module rewrote the superuser file genesis wrote: %+v", o)
+		}
+	}
+}

internal/bootstrap/rootsecrets.go

@@ -102,8 +102,16 @@ func keptOrMade(path string, dryRun bool) (value string, made bool, err error) {
 	}
 	// Written whole and renamed into place, at 0600, owned by whoever runs the installer — root,
 	// which is also who the host runs as when it later writes the sealed copy here.
+	//
+	// **The value alone, no line ending.** The module that adopts the store declares this same
+	// file, and what it declares is the value as `secret accept` took it — its line ending gone,
+	// by design. The host folds a mounted file's content into the container's spec (novox/hq
+	// 04-ISSUES/103), so a genesis that wrote `value\n` here would raise a store whose label
+	// digests one byte more than the module's file, and phase three would RECREATE the store it
+	// meant to adopt in place, with the temporary control plane connected to it. readCredentialFile
+	// tolerates either ending, so a file an earlier genesis wrote still reads.
 	tmp := path + ".genesis"
-	if err := os.WriteFile(tmp, []byte(value+"\n"), 0o600); err != nil {
+	if err := os.WriteFile(tmp, []byte(value), 0o600); err != nil {
 		return "", false, err
 	}
 	if err := os.Rename(tmp, path); err != nil {

internal/declaration/declaration.go

@@ -785,13 +785,14 @@ type Container struct {
 	// while every check passes because the file on disk is right. The host recreates the container
 	// when one of these resources changed this pass, even if the spec matches.
 	//
-	// What a running container reads at creation — its env-files, a file mounted into it, and the
-	// files the host wrote under a directory mounted into it — is part of its spec by content
-	// since novox/hq 04-ISSUES/103, and needs no naming here. RestartOn is for what the spec
-	// cannot see: a resource the container reflects without reading it directly, a step it
-	// consumes the result of. On a run-once step it means *run again*: a step that fetches a fact
-	// from a provider names the binding it reads, and is run again when the provider moved
-	// (novox/hq ADR 0099).
+	// What a running container reads at creation — its env-files, and a file mounted into it
+	// directly — is part of its spec by content since novox/hq 04-ISSUES/103, and needs no naming
+	// here. A directory mounted into it is NOT looked inside, not even for files the host wrote
+	// there: whether a service reads such a file once or watches it live is the service's, and
+	// RestartOn is how a module says "once, at start" — a config the host renders under the
+	// module's state directory, a step whose result it consumes. On a run-once step it means *run
+	// again*: a step that fetches a fact from a provider names the binding it reads, and is run
+	// again when the provider moved (novox/hq ADR 0099).
 	RestartOn []string `json:"restart-on,omitempty"`
 
 	// RunOnce marks a container the host runs to completion rather than leaves running: a step,

internal/store/store.go

@@ -18,7 +18,6 @@ import (
 	"os"
 	"path/filepath"
 	"sort"
-	"strings"
 	"time"
 )
 
@@ -181,24 +180,26 @@ func (s State) Recorded(kind, target string) bool {
 	return false
 }
 
-// FilesUnder returns every file this host has a record of writing at a path or beneath it, of any
-// origin and under any id, in path order.
+// At returns what this host has a record of putting at a target of this kind, under any id and of
+// any origin — Recorded, with the record.
 //
-// By path rather than by id because a container names what it reads by path: the id a file was
-// declared under may change — the bundle's, then a module's, for the same file — and the container
-// reading it does not care which.
-func (s State) FilesUnder(path string) []Applied {
-	var out []Applied
+// By target rather than by id because the id a thing was declared under may change while the thing
+// does not: the bundle's `store` becomes a module's `postgres.server` for the same container, and
+// the file that container reads is the same file under either id. Both ids may then hold a record
+// for the one target — the bundle's is never removed by the mesh's declaration — and the most
+// recently applied is the one that says what is there now.
+func (s State) At(kind, target string) (Applied, bool) {
+	var latest Applied
+	found := false
 	for _, r := range s.Resources {
-		if r.Type != "file" {
+		if r.Type != kind || r.Target != target {
 			continue
 		}
-		if r.Target == path || strings.HasPrefix(r.Target, strings.TrimSuffix(path, "/")+"/") {
-			out = append(out, r)
+		if !found || r.AppliedAt.After(latest.AppliedAt) {
+			latest, found = r, true
 		}
 	}
-	sort.Slice(out, func(i, j int) bool { return out[i].Target < out[j].Target })
-	return out
+	return latest, found
 }
 
 // HeldAt returns what is held under a resource id.