diff --git a/internal/catalogue/config_test.go b/internal/catalogue/config_test.go
new file mode 100644
index 00000000..1c89bb4d
--- /dev/null
+++ b/internal/catalogue/config_test.go
@@ -0,0 +1,403 @@
+package catalogue
+
+import (
+	"bytes"
+	"encoding/json"
+	"strings"
+	"testing"
+)
+
+// A module declares its config (novox/hq ADR 0348 §1, §4, §5, §6, §8, §11; design 57 package K1, issue 660):
+// one registration refusal per rule of design 57's K1, the old names read as aliases, and a module rewritten
+// from settings to config composing byte-identically.
+
+// inConfigForm is a module in the config form that registers: every value typed, described, defaulted or
+// required, placed in a file or read at runtime, and its mergeable file naming its keys.
+func inConfigForm() map[string]any {
+	return map[string]any{
+		"module":  "notifier",
+		"version": "1",
+		"config": map[string]any{
+			"font-size": map[string]any{"type": "number", "description": "the notification's font size, in points",
+				"minimum": 6, "maximum": 40, "default": 10},
+			"width": map[string]any{"type": "number", "description": "the notification's width, in pixels",
+				"default": 250},
+			"position": map[string]any{"type": "string", "description": "the corner it shows in, a word",
+				"enum": []any{"top-right", "top-left"}, "default": "top-right"},
+			"theme": map[string]any{"type": "string", "description": "the colour theme, a lower-case name",
+				"pattern": "[a-z]+", "default": "dark"},
+			"history": map[string]any{"type": "number", "description": "how many notifications it keeps, a count",
+				"default": 20, "runtime": true},
+			"sender": map[string]any{"type": "string", "description": "the address it mails a digest from",
+				"required": true},
+		},
+		"resources": []any{
+			map[string]any{"id": "configuration", "type": "file", "path": "/x/notifierrc",
+				"content": "font = Inter ${config:font-size}\nwidth = ${config:width}\nfrom = ${config:sender}\n"},
+			map[string]any{"id": "rules", "type": "file", "path": "/x/rules.json", "merge": "json",
+				"takes-config": []any{"position", "theme"}, "content": "{\"position\": \"top-right\"}\n"},
+			map[string]any{"id": "notifier", "type": "service", "unit": "notifier.service",
+				"reload-on": []any{"configuration"}, "restart-on": []any{"rules"}},
+		},
+	}
+}
+
+// declaration is one value of inConfigForm's config, to change in place.
+func declaration(m map[string]any, key string) map[string]any {
+	return m["config"].(map[string]any)[key].(map[string]any)
+}
+
+func resourceOf(m map[string]any, id string) map[string]any {
+	for _, r := range m["resources"].([]any) {
+		if r.(map[string]any)["id"] == id {
+			return r.(map[string]any)
+		}
+	}
+	return nil
+}
+
+func parseRaw(t *testing.T, m map[string]any) (Manifest, error) {
+	t.Helper()
+	raw, err := json.Marshal(m)
+	if err != nil {
+		t.Fatal(err)
+	}
+	return ParseManifest(raw)
+}
+
+// refused is that the manifest is refused with every one of these words.
+func refused(t *testing.T, m map[string]any, words ...string) {
+	t.Helper()
+	_, err := parseRaw(t, m)
+	if err == nil {
+		t.Fatalf("registered; wanted a refusal saying %q", words)
+	}
+	for _, w := range words {
+		if !strings.Contains(err.Error(), w) {
+			t.Fatalf("refused without %q:\n%v", w, err)
+		}
+	}
+}
+
+func TestAModuleInTheConfigFormRegisters(t *testing.T) {
+	m, err := parseRaw(t, inConfigForm())
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !m.DeclaresConfig() {
+		t.Fatal("a module declaring config is not read as in the config form")
+	}
+	d := m.Settings["font-size"]
+	if d.Type != "number" || d.Description == "" || d.Minimum == nil || *d.Minimum != 6 || d.Default != float64(10) {
+		t.Fatalf("font-size read as %+v", d)
+	}
+	if s := m.Settings["sender"]; !s.Required || s.Default != nil {
+		t.Fatalf("sender read as %+v", s)
+	}
+}
+
+// Rule 1: a value without type or description.
+func TestConfigRefusesAValueWithoutTypeOrDescription(t *testing.T) {
+	m := inConfigForm()
+	delete(declaration(m, "width"), "type")
+	refused(t, m, `notifier's config value "width"`, "no type")
+	m = inConfigForm()
+	declaration(m, "width")["type"] = "colour"
+	refused(t, m, `"width"`, `type "colour"`)
+	m = inConfigForm()
+	delete(declaration(m, "width"), "description")
+	refused(t, m, `"width"`, "no description")
+}
+
+// Rule 2: a value with neither a default nor required.
+func TestConfigRefusesAValueWithNeitherDefaultNorRequired(t *testing.T) {
+	m := inConfigForm()
+	delete(declaration(m, "width"), "default")
+	refused(t, m, `"width"`, "neither a default nor required")
+	m = inConfigForm()
+	declaration(m, "sender")["default"] = "noreply@example.org"
+	refused(t, m, `"sender"`, "both a default and required")
+}
+
+// Rule 3: a default failing its validation.
+func TestConfigRefusesADefaultFailingItsValidation(t *testing.T) {
+	for _, c := range []struct {
+		key   string
+		value any
+		said  string
+	}{
+		{"font-size", 4, "below its minimum"},
+		{"font-size", 41, "above its maximum"},
+		{"font-size", "10", "not a number"},
+		{"position", "bottom", "not one of"},
+		{"theme", "Dark", "does not match"},
+	} {
+		m := inConfigForm()
+		declaration(m, c.key)["default"] = c.value
+		refused(t, m, `"`+c.key+`"`, c.said)
+	}
+}
+
+// Rule 4: an object or a list not trusted.
+func TestConfigRefusesAnObjectOrListNotTrusted(t *testing.T) {
+	for _, kind := range []string{"object", "list"} {
+		m := inConfigForm()
+		def := any(map[string]any{"a": 1})
+		if kind == "list" {
+			def = []any{"a"}
+		}
+		m["config"].(map[string]any)["rules"] = map[string]any{"type": kind, "description": "the rules, as " + kind,
+			"default": def, "runtime": true}
+		refused(t, m, `"rules"`, "is "+kind+" and not trusted")
+		m["config"].(map[string]any)["rules"].(map[string]any)["trusted"] = true
+		if _, err := parseRaw(t, m); err != nil {
+			t.Fatalf("a trusted %s is refused: %v", kind, err)
+		}
+	}
+}
+
+// withPredefined is the list of predefined keys as package K2 will give it, for the length of a test.
+func withPredefined(t *testing.T, keys map[string]PredefinedKey) {
+	t.Helper()
+	was := predefinedKeys
+	predefinedKeys = keys
+	t.Cleanup(func() { predefinedKeys = was })
+}
+
+// Rule 5: a predefined key not on the list, or of another type. Until the list is present (package K2), a value
+// naming one is refused saying so.
+func TestConfigRefusesAPredefinedKeyNotOnTheListOrOfAnotherType(t *testing.T) {
+	m := inConfigForm()
+	declaration(m, "font-size")["predefined"] = "font-size"
+	refused(t, m, `"font-size"`, "the list of predefined keys", "not yet present")
+
+	withPredefined(t, map[string]PredefinedKey{"font-size": {Type: "number"}, "accent": {Type: "string"}})
+	if _, err := parseRaw(t, m); err != nil {
+		t.Fatalf("a value falling back to a listed key of its type is refused: %v", err)
+	}
+	m = inConfigForm()
+	declaration(m, "font-size")["predefined"] = "font-scale"
+	refused(t, m, `"font-size"`, `"font-scale"`, "not on the list")
+	m = inConfigForm()
+	declaration(m, "font-size")["predefined"] = "accent"
+	refused(t, m, `"font-size"`, `"accent"`, "is a string")
+}
+
+// Rule 6: an untrusted value falling back to a trusted predefined key.
+func TestConfigRefusesAnUntrustedValueFallingBackToATrustedKey(t *testing.T) {
+	m := inConfigForm()
+	declaration(m, "theme")["predefined"] = "theme"
+	refused(t, m, `"theme"`, "not yet present")
+
+	withPredefined(t, map[string]PredefinedKey{"theme": {Type: "string", Trusted: true}})
+	refused(t, m, `"theme"`, "trusted", "is not")
+	declaration(m, "theme")["trusted"] = true
+	if _, err := parseRaw(t, m); err != nil {
+		t.Fatalf("a trusted value falling back to a trusted key is refused: %v", err)
+	}
+}
+
+// Rule 7: a value neither placed in a template nor read at runtime.
+func TestConfigRefusesAValueNeitherPlacedNorReadAtRuntime(t *testing.T) {
+	m := inConfigForm()
+	delete(declaration(m, "history"), "runtime")
+	refused(t, m, `"history"`, "${config:history}", `"runtime": true`)
+	// Taken by a mergeable file is placed.
+	m = inConfigForm()
+	if _, err := parseRaw(t, m); err != nil {
+		t.Fatal(err)
+	}
+}
+
+// Rule 8: a placeholder naming an undeclared value.
+func TestConfigRefusesAPlaceholderNamingAnUndeclaredValue(t *testing.T) {
+	m := inConfigForm()
+	resourceOf(m, "configuration")["content"] = "font = ${config:font-size}\nwidth = ${config:width}\n" +
+		"from = ${config:sender}\ncolour = ${config:colour}\n"
+	refused(t, m, "${config:colour}", "declares no such value")
+}
+
+// Rule 9: a reload-on or restart-on naming a file the module does not declare.
+func TestConfigRefusesAReloadOrRestartOnNamingAnUndeclaredFile(t *testing.T) {
+	m := inConfigForm()
+	resourceOf(m, "notifier")["reload-on"] = []any{"configuration", "dunstrc"}
+	refused(t, m, "reload-on", `"dunstrc"`, "declares no such")
+	m = inConfigForm()
+	resourceOf(m, "notifier")["restart-on"] = []any{"rule"}
+	refused(t, m, "restart-on", `"rule"`)
+	// Another module's file, and one the mesh makes for the module, are not the module's to declare.
+	m = inConfigForm()
+	resourceOf(m, "notifier")["restart-on"] = []any{"rules", "resolver.fact-zones", "secret-mail", "composed-jails"}
+	if _, err := parseRaw(t, m); err != nil {
+		t.Fatalf("refused: %v", err)
+	}
+}
+
+// Rule 10: a moved module's mergeable file not naming its keys under takes-config.
+func TestConfigRefusesAMergeableFileNotNamingItsKeys(t *testing.T) {
+	m := inConfigForm()
+	delete(resourceOf(m, "rules"), "takes-config")
+	// position and theme are then placed nowhere; say they are read at runtime so only the file's rule speaks.
+	declaration(m, "position")["runtime"] = true
+	declaration(m, "theme")["runtime"] = true
+	refused(t, m, "rules", "names no takes-config")
+}
+
+// Rule 11: a mesh word, puid or pgid in takes-config.
+func TestConfigRefusesAMeshWordOrAnAccountFactInTakesConfig(t *testing.T) {
+	for _, word := range []string{"ports", "expose", "reach", "endpoints", "places", "accesses", "networks", "puid", "pgid"} {
+		m := inConfigForm()
+		resourceOf(m, "rules")["takes-config"] = []any{"position", "theme", word}
+		refused(t, m, `"`+word+`"`, "takes-config")
+	}
+}
+
+// A module uses one form or the other, never both.
+func TestAManifestMixingTheConfigAndSettingsFormsIsRefused(t *testing.T) {
+	m := inConfigForm()
+	resourceOf(m, "configuration")["content"] = "font = ${config:font-size}\nwidth = ${setting:width}\nfrom = ${config:sender}\n"
+	refused(t, m, "mixes", "${setting:", "config")
+
+	m = inConfigForm()
+	delete(resourceOf(m, "rules"), "takes-config")
+	resourceOf(m, "rules")["takes-settings"] = []any{"position", "theme"}
+	refused(t, m, "mixes", "takes-settings")
+
+	m = inConfigForm()
+	m["settings"] = map[string]any{"colour": map[string]any{"kind": "preference", "default": "red", "why": "red"}}
+	refused(t, m, "mixes", "settings")
+}
+
+// The settings form keeps its own declaration; the config form's has no kind or why.
+func TestEachFormKeepsItsOwnDeclaration(t *testing.T) {
+	m := inConfigForm()
+	declaration(m, "width")["why"] = "fits a title"
+	refused(t, m, `"width"`, "why")
+
+	err := parsed(t, Manifest{Module: "notifier",
+		Settings: map[string]SettingDeclaration{"width": {Kind: KindPreference, Default: float64(250),
+			Why: "fits a title", Type: "number"}},
+		Resources: []map[string]any{{"id": "c", "type": "file", "path": "/x", "content": "${setting:width}"}}})
+	if err == nil || !strings.Contains(err.Error(), "under config") {
+		t.Fatalf("a typed value under settings: %v", err)
+	}
+}
+
+// What the mesh holds is what was written: a module in the config form is written back in it, and read again
+// the same.
+func TestAConfigManifestIsWrittenBackInItsOwnForm(t *testing.T) {
+	m, err := parseRaw(t, inConfigForm())
+	if err != nil {
+		t.Fatal(err)
+	}
+	raw, err := json.Marshal(m)
+	if err != nil {
+		t.Fatal(err)
+	}
+	for _, said := range []string{`"config":`, `${config:font-size}`, `"takes-config":`, `"required":true`} {
+		if !strings.Contains(string(raw), said) {
+			t.Fatalf("written back without %s: %s", said, raw)
+		}
+	}
+	for _, unsaid := range []string{`"settings":`, `${setting:`, `"takes-settings"`, `"kind"`, `"why"`, `"default":null`} {
+		if strings.Contains(string(raw), unsaid) {
+			t.Fatalf("written back with %s: %s", unsaid, raw)
+		}
+	}
+	again, err := ParseManifest(raw)
+	if err != nil {
+		t.Fatal(err)
+	}
+	twice, _ := json.Marshal(again)
+	if !bytes.Equal(raw, twice) {
+		t.Fatalf("read again it is written\n%s\nwhere it was\n%s", twice, raw)
+	}
+}
+
+// A module in the settings form is written back byte for byte as before.
+func TestASettingsManifestIsWrittenBackAsBefore(t *testing.T) {
+	d := SettingDeclaration{Kind: KindPreference, Default: float64(10), Why: "readable"}
+	raw, err := json.Marshal(d)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if string(raw) != `{"kind":"preference","default":10,"why":"readable"}` {
+		t.Fatalf("written as %s", raw)
+	}
+}
+
+// settingsDunst is the dunst module as it is written today; configDunst the same module rewritten from settings to
+// config.
+const settingsDunst = `{"module": "dunst", "version": "1",
+  "settings": {
+    "font-size": {"kind": "preference", "default": 10, "why": "10 points of Inter reads well on a screen of about 100 DPI"},
+    "width": {"kind": "preference", "default": 250, "why": "250 pixels fits a title of about forty characters at 10 points"}
+  },
+  "resources": [
+    {"id": "package", "type": "package", "package": "dunst"},
+    {"id": "configuration", "type": "file", "path": "/home/me/.config/dunst/dunstrc", "mode": "0644",
+     "content": "[global]\n    font = Inter ${setting:font-size}\n    width = ${setting:width}\n"},
+    {"id": "rules", "type": "file", "path": "/home/me/.config/dunst/rules.json", "merge": "json",
+     "takes-settings": [], "content": "{\"urgency\": \"low\"}\n"},
+    {"id": "notifier", "type": "service", "unit": "dunst.service", "reload-on": ["configuration"]}
+  ]}`
+
+const configDunst = `{"module": "dunst", "version": "1",
+  "config": {
+    "font-size": {"type": "number", "description": "the font size of a notification, in points", "minimum": 6,
+                  "maximum": 40, "default": 10},
+    "width": {"type": "number", "description": "the width of a notification, in pixels", "minimum": 100,
+              "default": 250}
+  },
+  "resources": [
+    {"id": "package", "type": "package", "package": "dunst"},
+    {"id": "configuration", "type": "file", "path": "/home/me/.config/dunst/dunstrc", "mode": "0644",
+     "content": "[global]\n    font = Inter ${config:font-size}\n    width = ${config:width}\n"},
+    {"id": "rules", "type": "file", "path": "/home/me/.config/dunst/rules.json", "merge": "json",
+     "takes-config": [], "content": "{\"urgency\": \"low\"}\n"},
+    {"id": "notifier", "type": "service", "unit": "dunst.service", "reload-on": ["configuration"]}
+  ]}`
+
+// ${config:<key>} fills exactly as ${setting:<key>} does: the module rewritten from settings to config composes
+// to the same bytes, with no layer, with the node's, and with the mesh's under the node's.
+func TestAModuleRewrittenFromSettingsToConfigComposesByteIdentically(t *testing.T) {
+	composed := func(manifest string, layers []Layer) []byte {
+		t.Helper()
+		m, err := ParseManifest([]byte(manifest))
+		if err != nil {
+			t.Fatal(err)
+		}
+		r := anAdoptedAnchor()
+		r.Modules = append(r.Modules, m)
+		with := anchorRendering(false)
+		if layers != nil {
+			with.Settings["dunst"] = layers
+		}
+		c, err := r.Compose(with)
+		if err != nil {
+			t.Fatal(err)
+		}
+		if why, left := c.LeftOut["dunst"]; left {
+			t.Fatalf("dunst was left out: %s", why)
+		}
+		raw, err := json.Marshal(c)
+		if err != nil {
+			t.Fatal(err)
+		}
+		return raw
+	}
+	for _, layers := range [][]Layer{
+		nil,
+		{{From: "anchor", Values: map[string]any{"font-size": float64(13)}}},
+		{{From: MeshWideLayer, Values: map[string]any{"width": float64(300)}},
+			{From: "anchor", Values: map[string]any{"font-size": float64(12), "width": float64(320)}}},
+	} {
+		was, is := composed(settingsDunst, layers), composed(configDunst, layers)
+		if !bytes.Equal(was, is) {
+			t.Fatalf("composed differently with %v:\nsettings: %s\nconfig:   %s", layers, was, is)
+		}
+		if !strings.Contains(string(is), "font = Inter 1") || strings.Contains(string(is), "${config:") {
+			t.Fatalf("not filled: %s", is)
+		}
+	}
+}