diff --git a/cmd/mesh-controller/template_test.go b/cmd/mesh-controller/template_test.go
new file mode 100644
index 00000000..60ca0e74
--- /dev/null
+++ b/cmd/mesh-controller/template_test.go
@@ -0,0 +1,177 @@
+package main
+
+import (
+	"bytes"
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"github.com/novox/mesh-controller/internal/catalogue"
+	snapshot "github.com/novox/mesh-controller/internal/facts"
+	"github.com/novox/mesh-controller/internal/inventory"
+)
+
+// A file's text kept as a template file in its module's repository (novox/hq ADR 0349 §2, design 57 package T1,
+// issue 654): `module check` and the merge gate read it from the tree beside the manifest, so a change to a
+// template alone is judged as a change to its module.
+
+const templatedNotifier = `{"module":"notifier","version":"1",
+  "build":{"artifacts":[{"name":"files","kind":"archive","from":"files"}]},
+  "resources":[{"id":"conf","type":"file","path":"/etc/notifier/notifier.conf","mode":"0644","template":"files/notifier.conf"}]}`
+
+// inlineNotifier is the same module as the mesh holds it: built, its text inline.
+const inlineNotifier = `{"module":"notifier","version":"1",
+  "resources":[{"id":"conf","type":"file","path":"/etc/notifier/notifier.conf","mode":"0644","content":"volume = 3\n"}]}`
+
+// aTemplatedModule writes a module's directory: its manifest and its files/.
+func aTemplatedModule(t *testing.T, dir, manifest string, files map[string]string) string {
+	t.Helper()
+	if err := os.MkdirAll(dir, 0o755); err != nil {
+		t.Fatal(err)
+	}
+	path := filepath.Join(dir, "module.json")
+	if err := os.WriteFile(path, []byte(manifest), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	for name, text := range files {
+		full := filepath.Join(dir, filepath.FromSlash(name))
+		if err := os.MkdirAll(filepath.Dir(full), 0o755); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(full, []byte(text), 0o644); err != nil {
+			t.Fatal(err)
+		}
+	}
+	return path
+}
+
+func TestModuleCheckReadsTemplatesFromTheTreeBesideTheManifest(t *testing.T) {
+	good := aTemplatedModule(t, t.TempDir(), templatedNotifier, map[string]string{"files/notifier.conf": "volume = 3\n"})
+	var out bytes.Buffer
+	if err := moduleCheck([]string{good}, &out); err != nil || !strings.Contains(out.String(), "notifier: ok") {
+		t.Fatalf("a module with its text in files/ was refused: %v\n%s", err, out.String())
+	}
+
+	// A change to the template alone, to text the controller refuses inline, is refused the same.
+	bad := aTemplatedModule(t, t.TempDir(), templatedNotifier,
+		map[string]string{"files/notifier.conf": "volume = 3\nstore = ${dir:nowhere}\n"})
+	out.Reset()
+	if err := moduleCheck([]string{bad}, &out); err == nil || !strings.Contains(out.String(), "nowhere") {
+		t.Fatalf("a template whose text is refused inline passed:\n%s", out.String())
+	}
+
+	// And a template the tree lacks, by name.
+	missing := aTemplatedModule(t, t.TempDir(), templatedNotifier, nil)
+	out.Reset()
+	if err := moduleCheck([]string{missing}, &out); err == nil || !strings.Contains(out.String(), "files/notifier.conf") {
+		t.Fatalf("a missing template was not refused by name:\n%s", out.String())
+	}
+}
+
+// templatedMesh is catalogueMesh with the notifier on the laptop, registered as built: its text inline.
+func templatedMesh(t *testing.T) (snapshot.Facts, map[string]string) {
+	t.Helper()
+	open := aMesh(t)
+	ctx := t.Context()
+	manifests := map[string]string{
+		"lemurs": `{"module":"lemurs","version":"1","capabilities":["systemd"],
+			"resources":[{"id":"service","type":"service","unit":"lemurs.service","state":"running","boot":"enabled"}]}`,
+		"notifier": inlineNotifier,
+	}
+	for name, raw := range manifests {
+		m, err := catalogue.ParseManifest([]byte(raw))
+		if err != nil {
+			t.Fatalf("%s: %v", name, err)
+		}
+		if err := open.inventory.RegisterModule(ctx, m, inventory.Source{Repository: "novox/mesh-catalog",
+			Path: "modules/" + name, BuiltFrom: "c0ffee"}); err != nil {
+			t.Fatal(err)
+		}
+		if _, err := assign(ctx, open, "laptop", name); err != nil {
+			t.Fatalf("assign %s: %v", name, err)
+		}
+	}
+	f, err := gatherFacts(ctx, open, "2.11.17")
+	if err != nil {
+		t.Fatal(err)
+	}
+	return f, manifests
+}
+
+// aTemplatedTree is the catalogue's checkout with the notifier's text in files/.
+func aTemplatedTree(t *testing.T, manifests map[string]string, text string, has bool) string {
+	t.Helper()
+	tree := aTree(t, withEdit(manifests, "notifier", ""))
+	files := map[string]string{}
+	if has {
+		files["files/notifier.conf"] = text
+	}
+	aTemplatedModule(t, filepath.Join(tree, "modules", "notifier"), templatedNotifier, files)
+	return tree
+}
+
+const notifierTemplate = "modules/notifier/files/notifier.conf"
+
+func TestTheMergeGateJudgesAChangeToATemplateAlone(t *testing.T) {
+	f, manifests := templatedMesh(t)
+
+	// The module moved to its template, the same text: nothing changes on any machine.
+	v := gateJudged(t, f, aTemplatedTree(t, manifests, "volume = 3\n", true), "modules/notifier/module.json",
+		notifierTemplate)
+	if v.Verdict == "fail" || v.Modules["notifier"] != "" {
+		t.Fatalf("the module moved to its template with the same text reads as a change (%v):\n%s", v.Modules, v.Report())
+	}
+
+	// The template alone changed: its module changed, and composes.
+	v = gateJudged(t, f, aTemplatedTree(t, manifests, "volume = 4\n", true), notifierTemplate)
+	if v.Verdict == "fail" || v.Modules["notifier"] != "changed" {
+		t.Fatalf("a change to the template alone is not a change to its module (%v):\n%s", v.Modules, v.Report())
+	}
+	if v.Width == nil || strings.Join(v.Width.Modules, ",") != "notifier" {
+		t.Fatalf("a change to the template rebuilds %+v, not its module", v.Width)
+	}
+
+	// The template alone changed to text the controller refuses: the pull request fails, naming the module.
+	v = gateJudged(t, f, aTemplatedTree(t, manifests, "store = ${dir:nowhere}\n", true), notifierTemplate)
+	if v.Verdict != "fail" || !strings.Contains(v.Report(), "notifier") {
+		t.Fatalf("a template the controller refuses passed the gate:\n%s", v.Report())
+	}
+
+	// And the template removed from the tree fails, naming it.
+	v = gateJudged(t, f, aTemplatedTree(t, manifests, "", false), notifierTemplate)
+	if v.Verdict != "fail" || !strings.Contains(v.Report(), "files/notifier.conf") {
+		t.Fatalf("a missing template passed the gate:\n%s", v.Report())
+	}
+}
+
+// What the gate composes for the module in its template form is what the mesh composes for it inline.
+func TestTheMergeGateResolvesATemplatedModuleToItsInlineTwin(t *testing.T) {
+	dir := t.TempDir()
+	path := aTemplatedModule(t, dir, templatedNotifier, map[string]string{"files/notifier.conf": "volume = 3\n"})
+	raw, err := os.ReadFile(path)
+	if err != nil {
+		t.Fatal(err)
+	}
+	m, err := catalogue.ParseManifest(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	m, err = catalogue.WithTemplatesFrom(m, dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	resolved, err := standInBuild(m)
+	if err != nil {
+		t.Fatal(err)
+	}
+	inline, err := catalogue.ParseManifest([]byte(inlineNotifier))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if builtAlike(resolved) != builtAlike(inline) {
+		got, _ := json.Marshal(resolved)
+		t.Fatalf("the templated module resolves to %s, not its inline twin", got)
+	}
+}
diff --git a/internal/catalogue/template_test.go b/internal/catalogue/template_test.go
new file mode 100644
index 00000000..85c81896
--- /dev/null
+++ b/internal/catalogue/template_test.go
@@ -0,0 +1,258 @@
+package catalogue
+
+import (
+	"encoding/json"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// A file resource may name a template file in its module's repository (novox/hq ADR 0349 §2, design 57 package
+// T1, issue 654): the build packs files/ into an archive, and resolving the build reads each template's text back
+// into content, so the mesh holds, composes and sends exactly what it would for the same text inline.
+
+// The two forms of one module: its text inline, and its text in files/.
+const (
+	inlineTwin = `{"module":"tidy","version":"1",
+  "build":{"artifacts":[{"name":"files","kind":"archive","from":"files"}]},
+  "resources":[
+    {"id":"conf","type":"directory","path":"${dir:conf}"},
+    {"id":"main","type":"file","path":"${dir:conf}/tidy.conf","mode":"0644","content":"` + mainText + `"},
+    {"id":"extra","type":"file","path":"${dir:conf}/extra.conf","content":"` + extraText + `"}]}`
+	templatedTwin = `{"module":"tidy","version":"1",
+  "build":{"artifacts":[{"name":"files","kind":"archive","from":"files"}]},
+  "resources":[
+    {"id":"conf","type":"directory","path":"${dir:conf}"},
+    {"id":"main","type":"file","path":"${dir:conf}/tidy.conf","mode":"0644","template":"files/tidy.conf"},
+    {"id":"extra","type":"file","path":"${dir:conf}/extra.conf","template":"files/deeper/extra.conf"}]}`
+	mainText  = `# tidy\nroot = ${dir:conf}\nquoted = \"yes\" é\n`
+	extraText = `one\ntwo\n`
+)
+
+// templateTexts is what a build reads back from the packed files/ archive: by path inside it.
+func templateTexts(t *testing.T) map[string]string {
+	t.Helper()
+	var m struct{ Main, Extra string }
+	if err := json.Unmarshal([]byte(`{"Main":"`+mainText+`","Extra":"`+extraText+`"}`), &m); err != nil {
+		t.Fatal(err)
+	}
+	return map[string]string{"tidy.conf": m.Main, "deeper/extra.conf": m.Extra, "unused.conf": "not named"}
+}
+
+func builtFiles(texts map[string]string) []Built {
+	return []Built{{Name: "files", Kind: ArtifactArchive,
+		Reference: ArtifactStoreScheme + "tidy/files/blobs/sha256:" + strings.Repeat("c", 64),
+		Digest:    "sha256:" + strings.Repeat("c", 64), Texts: texts}}
+}
+
+// held is a manifest as registration holds it: resolved with what was built, then read again strictly.
+func held(t *testing.T, raw string, built []Built) Manifest {
+	t.Helper()
+	m, err := ParseManifest([]byte(raw))
+	if err != nil {
+		t.Fatal(err)
+	}
+	resolved, err := m.Resolve(built)
+	if err != nil {
+		t.Fatal(err)
+	}
+	again, err := json.Marshal(resolved)
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := ParseManifest(again)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if problem := HeldTemplateProblem(out); problem != "" {
+		t.Fatal(problem)
+	}
+	return out
+}
+
+func composed(t *testing.T, m Manifest) string {
+	t.Helper()
+	got, err := Resolve(shelf(m), []string{m.Module}, workstation(), World{})
+	if err != nil {
+		t.Fatal(err)
+	}
+	out, err := json.Marshal(mustDeclare(t, got))
+	if err != nil {
+		t.Fatal(err)
+	}
+	return string(out)
+}
+
+func TestATemplatedModuleComposesByteIdenticallyToItsInlineTwin(t *testing.T) {
+	inline := composed(t, held(t, inlineTwin, builtFiles(nil)))
+	templated := composed(t, held(t, templatedTwin, builtFiles(templateTexts(t))))
+	if inline != templated {
+		t.Fatalf("the two forms compose differently:\ninline:    %s\ntemplated: %s", inline, templated)
+	}
+	if !strings.Contains(templated, "quoted = \\\"yes\\\"") || strings.Contains(templated, `"template"`) {
+		t.Fatalf("the composition does not carry the template's text as content: %s", templated)
+	}
+}
+
+// What `module check`, the merge gate and `module add` judge: the text read from the tree beside the manifest.
+func TestATemplatedModuleReadFromItsTreeComposesByteIdenticallyToItsInlineTwin(t *testing.T) {
+	dir := t.TempDir()
+	for name, text := range templateTexts(t) {
+		full := filepath.Join(dir, "files", filepath.FromSlash(name))
+		if err := os.MkdirAll(filepath.Dir(full), 0o755); err != nil {
+			t.Fatal(err)
+		}
+		if err := os.WriteFile(full, []byte(text), 0o644); err != nil {
+			t.Fatal(err)
+		}
+	}
+	m, err := ParseManifest([]byte(templatedTwin))
+	if err != nil {
+		t.Fatal(err)
+	}
+	filled, err := WithTemplatesFrom(m, dir)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if filled.Templated() {
+		t.Fatal("a manifest read from its tree still names a template")
+	}
+	resolved, err := filled.Resolve(builtFiles(nil))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if got, want := composed(t, resolved), composed(t, held(t, inlineTwin, builtFiles(nil))); got != want {
+		t.Fatalf("read from the tree, the module composes differently:\ninline:    %s\ntemplated: %s", want, got)
+	}
+}
+
+func TestAFileNamingBothATemplateAndContentIsRefused(t *testing.T) {
+	raw := strings.Replace(templatedTwin, `"template":"files/tidy.conf"`,
+		`"template":"files/tidy.conf","content":"x"`, 1)
+	_, err := ParseManifest([]byte(raw))
+	if err == nil || !strings.Contains(err.Error(), "main") || !strings.Contains(err.Error(), "never both") {
+		t.Fatalf("a file with both a template and content was not refused by name: %v", err)
+	}
+}
+
+func TestATemplateOutsideFilesIsRefusedByName(t *testing.T) {
+	for _, bad := range []string{"../tidy.conf", "/etc/tidy.conf", "files", "files/", "files/../tidy.conf",
+		"files/./tidy.conf", "other/tidy.conf", "tidy.conf", "files//tidy.conf", `files\\tidy.conf`} {
+		raw := strings.Replace(templatedTwin, `"files/tidy.conf"`, `"`+bad+`"`, 1)
+		_, err := ParseManifest([]byte(raw))
+		if err == nil || !strings.Contains(err.Error(), "main") || !strings.Contains(err.Error(), "not a file under files/") {
+			t.Errorf("the template %q was not refused by name: %v", bad, err)
+		}
+	}
+}
+
+func TestATemplateOnAResourceThatIsNotAFileIsRefused(t *testing.T) {
+	raw := strings.Replace(templatedTwin, `{"id":"conf","type":"directory","path":"${dir:conf}"}`,
+		`{"id":"conf","type":"directory","path":"${dir:conf}","template":"files/tidy.conf"}`, 1)
+	_, err := ParseManifest([]byte(raw))
+	if err == nil || !strings.Contains(err.Error(), "conf is a directory and names a template") {
+		t.Fatalf("a directory naming a template was not refused: %v", err)
+	}
+}
+
+func TestATemplatedModuleWhoseBuildPacksNoFilesIsRefused(t *testing.T) {
+	for _, build := range []string{
+		``,
+		`"build":{"artifacts":[{"name":"look","kind":"archive","from":"theme"}]},`,
+		`"build":{"artifacts":[{"name":"a","kind":"archive","from":"files"},{"name":"b","kind":"archive","from":"./files/"}]},`,
+	} {
+		raw := strings.Replace(templatedTwin,
+			`"build":{"artifacts":[{"name":"files","kind":"archive","from":"files"}]},`, build, 1)
+		_, err := ParseManifest([]byte(raw))
+		if err == nil || !strings.Contains(err.Error(), "files/") {
+			t.Errorf("a templated module with the build %q was not refused: %v", build, err)
+		}
+	}
+}
+
+func TestAMissingTemplateIsRefusedByName(t *testing.T) {
+	m, err := ParseManifest([]byte(templatedTwin))
+	if err != nil {
+		t.Fatal(err)
+	}
+	// In the tree beside the manifest.
+	dir := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(dir, "files"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "files", "tidy.conf"), []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	_, err = WithTemplatesFrom(m, dir)
+	if err == nil || !strings.Contains(err.Error(), "extra") || !strings.Contains(err.Error(), "files/deeper/extra.conf") {
+		t.Fatalf("a template missing from the tree was not refused by name: %v", err)
+	}
+	// And in what the build read back from its archive.
+	texts := templateTexts(t)
+	delete(texts, "deeper/extra.conf")
+	_, err = m.Resolve(builtFiles(texts))
+	if err == nil || !strings.Contains(err.Error(), "extra") || !strings.Contains(err.Error(), "files/deeper/extra.conf") {
+		t.Fatalf("a template missing from the archive was not refused by name: %v", err)
+	}
+}
+
+func TestATemplateThatIsASymlinkIsRefused(t *testing.T) {
+	m, err := ParseManifest([]byte(templatedTwin))
+	if err != nil {
+		t.Fatal(err)
+	}
+	dir := t.TempDir()
+	if err := os.MkdirAll(filepath.Join(dir, "files", "deeper"), 0o755); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "elsewhere"), []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "files", "tidy.conf"), []byte("x"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	if err := os.Symlink(filepath.Join(dir, "elsewhere"), filepath.Join(dir, "files", "deeper", "extra.conf")); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := WithTemplatesFrom(m, dir); err == nil || !strings.Contains(err.Error(), "not a plain file") {
+		t.Fatalf("a template that is a symlink was not refused: %v", err)
+	}
+}
+
+func TestAResolveWithoutTheArchivesTextIsRefused(t *testing.T) {
+	m, err := ParseManifest([]byte(templatedTwin))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if _, err := m.Resolve(builtFiles(nil)); err == nil || !strings.Contains(err.Error(), "files") {
+		t.Fatalf("a templated module resolved with no text read back from its archive: %v", err)
+	}
+}
+
+func TestATemplateThatIsNotUTF8IsRefused(t *testing.T) {
+	m, err := ParseManifest([]byte(templatedTwin))
+	if err != nil {
+		t.Fatal(err)
+	}
+	texts := templateTexts(t)
+	texts["tidy.conf"] = "\xff\xfe"
+	if _, err := m.Resolve(builtFiles(texts)); err == nil || !strings.Contains(err.Error(), "UTF-8") {
+		t.Fatalf("a template that is not UTF-8 was resolved: %v", err)
+	}
+}
+
+// What registration refuses: a manifest to be held that still names a template — one resolved by a builder that
+// predates templates would otherwise compose files with no text.
+func TestAManifestStillNamingATemplateIsNotHeld(t *testing.T) {
+	m, err := ParseManifest([]byte(templatedTwin))
+	if err != nil {
+		t.Fatal(err)
+	}
+	if problem := HeldTemplateProblem(m); !strings.Contains(problem, "main") || !strings.Contains(problem, "files/tidy.conf") {
+		t.Fatalf("a manifest naming a template would be held: %q", problem)
+	}
+	if problem := HeldTemplateProblem(held(t, inlineTwin, builtFiles(nil))); problem != "" {
+		t.Fatalf("an inline manifest is refused: %s", problem)
+	}
+}