diff --git a/apps/api/tests/module-ui-host-e2e.test.ts b/apps/api/tests/module-ui-host-e2e.test.ts
index 5e9a0ef..f73af62 100644
--- a/apps/api/tests/module-ui-host-e2e.test.ts
+++ b/apps/api/tests/module-ui-host-e2e.test.ts
@@ -479,7 +479,6 @@ describe("end to end: a discovered module's UI mounts in the Ekklesia host", ()
         "contributions",
         "display",
         "moduleId",
-        "navigation",
         "permissions",
         "principal",
         "realtime",
diff --git a/apps/api/tests/module-ui-routes.test.ts b/apps/api/tests/module-ui-routes.test.ts
index 2cd768f..bee6f08 100644
--- a/apps/api/tests/module-ui-routes.test.ts
+++ b/apps/api/tests/module-ui-routes.test.ts
@@ -953,7 +953,6 @@ describe("module UI artifact publication — the generic loader consumes what is
       contributions: NO_MODULE_UI_CONTRIBUTIONS,
       display: undefined,
       moduleId: "announcements",
-      navigation: undefined,
       permissions: { has: () => false },
       principal: { kind: "anonymous" as const },
       realtime: { subscribe: () => ({ close: () => undefined }) },
diff --git a/docs/architecture/decisions/0063-module-navigation-contract-manifest-v9.md b/docs/architecture/decisions/0063-module-navigation-contract-manifest-v9.md
index 3574ec2..55c1f0e 100644
--- a/docs/architecture/decisions/0063-module-navigation-contract-manifest-v9.md
+++ b/docs/architecture/decisions/0063-module-navigation-contract-manifest-v9.md
@@ -176,8 +176,14 @@ The shell parses both strictly.
 ### The module's navigation capability
 
 `ModuleUiHostContext.navigation` (`@ekklesia/module-ui-sdk`) is a narrow host capability, not a
-router. It is `undefined` where a host has no addressable pages: the display host, and a standalone
-host without routes.
+router, and an **optional** member (`navigation?: ModuleUiNavigation`). A host with addressable
+module pages (Ekklesia's Dashboard) supplies it. A host without them (the display host, and a
+standalone host without routes) omits it, and may also set it to `undefined`.
+
+The member is optional so that adding it breaks no one. Ekklesia's 0.x versioning makes patch
+releases compatible, and a context built before navigation existed must stay a complete, valid
+context that compiles unchanged. A `@ekklesia/module-ui-sdk` test holds exactly that, and fails if
+the member is ever made required.
 
 ```ts
 interface ModuleUiNavigation {
@@ -208,7 +214,7 @@ interface ModuleUiNavigation {
   rebuilt against the new SDK can already link to its Settings page.
 
 Adding a context member changes nothing about how an artifact is mounted, so the mount ABI stays at
-version 2. A module that uses `navigation` checks for it, exactly as it checks `display`.
+version 2. A module that uses `navigation` feature-detects it (`context.navigation?.navigate(…)`).
 
 ### Return-to-origin: one carrier, the `return` query parameter
 
@@ -262,8 +268,8 @@ parameter from it.
 - **Packages.** `@ekklesia/contracts` gains `module-navigation.ts`, the v8/v9 manifest union, and
   `moduleManifestNavigation`. `@ekklesia/module-ui-sdk` gains `navigation.ts` and
   `ModuleUiHostContext.navigation`. `@ekklesia/module-sdk` re-exports the navigation helpers and
-  types. All changes are additive for module code. A host that builds a context itself must now say
-  `navigation: undefined`.
+  types. Every change is additive at the source level as well as at run time: existing module code,
+  and an existing host that builds a context itself, compile and run unchanged.
 - **Core** publishes each module's navigation beside its name. The navigation response gains a
   `navigation` member per module.
 - **The shell** reads module routes at any depth, draws icons and pages, and supplies the
diff --git a/docs/module-development/README.md b/docs/module-development/README.md
index 8c707c3..ba41552 100644
--- a/docs/module-development/README.md
+++ b/docs/module-development/README.md
@@ -720,7 +720,8 @@ artifact is the role selection.
 
 ### What the host gives you
 
-`mount` receives exactly eight members, and nothing else is available:
+`mount` receives these members, and nothing else is available. `navigation` is optional: a host that
+has no addressable pages leaves it out, so feature-detect it.
 
 | Member | What it is |
 | --- | --- |
@@ -731,7 +732,7 @@ artifact is the role selection.
 | `realtime` | `subscribe(channel, handlers)` against **your own** module's live state — see [Realtime state](#realtime-state) |
 | `contributions` | Renderers other modules contributed to capabilities **you** provide — see [Browser contributions](#browser-contributions) |
 | `display` | Your display page's URL, or `undefined` when you publish none |
-| `navigation` | Where your module is, and how it moves between its own pages and to its Settings page — see [Module navigation](#module-navigation). `undefined` on the display host |
+| `navigation` | Where your module is, and how it moves between its own pages and to its Settings page — see [Module navigation](#module-navigation). Optional: absent on the display host |
 
 Module configuration, organization context, and diagnostics reporting are **not** in the contract.
 They need designs that do not exist, and a speculative field frozen into a public contract is harder
@@ -795,7 +796,7 @@ A refresh, a bookmark, and Back and Forward all land on the same route.
 never build a Dashboard URL yourself:
 
 ```tsx
-const { navigation } = context;            // undefined on the display host
+const { navigation } = context;            // optional: absent on the display host
 navigation?.location();                    // { path: "media/sermons/123", page: "media" }
 navigation?.subscribe(() => rerender());   // every move: yours, the sidebar's, Back and Forward
 navigation?.navigate("timelines");         // or { replace: true } to respell the current entry
diff --git a/packages/module-ui-host/tests/load-module-ui.test.ts b/packages/module-ui-host/tests/load-module-ui.test.ts
index f9a8375..ef9535f 100644
--- a/packages/module-ui-host/tests/load-module-ui.test.ts
+++ b/packages/module-ui-host/tests/load-module-ui.test.ts
@@ -54,7 +54,6 @@ function hostContext(requested: string[], moduleId = "announcements"): ModuleUiH
     contributions: NO_MODULE_UI_CONTRIBUTIONS,
     display: undefined,
     moduleId,
-    navigation: undefined,
     api: {
       async request(path) {
         requested.push(path);
diff --git a/packages/module-ui-host/tests/real-artifact.test.ts b/packages/module-ui-host/tests/real-artifact.test.ts
index 9adc8f7..0b1e391 100644
--- a/packages/module-ui-host/tests/real-artifact.test.ts
+++ b/packages/module-ui-host/tests/real-artifact.test.ts
@@ -35,7 +35,6 @@ function ekklesiaContext(requested: string[]): ModuleUiHostContext {
     contributions: NO_MODULE_UI_CONTRIBUTIONS,
     display: undefined,
     moduleId: "example",
-    navigation: undefined,
     api: {
       async request(pathname) {
         requested.push(`/api/v1/modules/example/${pathname.replace(/^\//u, "")}`);
@@ -54,7 +53,6 @@ function standaloneContext(requested: string[]): ModuleUiHostContext {
     contributions: NO_MODULE_UI_CONTRIBUTIONS,
     display: { url: "https://example.test/display" },
     moduleId: "example",
-    navigation: undefined,
     api: {
       async request(pathname) {
         requested.push(`https://example.test/api/${pathname.replace(/^\//u, "")}`);
diff --git a/packages/module-ui-sdk/src/host-context.ts b/packages/module-ui-sdk/src/host-context.ts
index 3762462..27f6c61 100644
--- a/packages/module-ui-sdk/src/host-context.ts
+++ b/packages/module-ui-sdk/src/host-context.ts
@@ -108,11 +108,13 @@ export interface ModuleUiHostContext {
    * Where this module is and how it moves between its own pages, and to its Settings page
    * (ADR 0063). See {@link ModuleUiNavigation}.
    *
-   * `undefined` where the host has no addressable pages for it — the full-viewport display host,
-   * which shows one screen, and any standalone host without routes. A module that offers
-   * navigation checks for it, exactly as it checks `display`.
+   * **Optional**, so adding it broke no existing host: a context built before navigation existed
+   * is still a complete context. A host with addressable module pages — Ekklesia's Dashboard —
+   * supplies it; a host without them — the full-viewport display host, which shows one screen, or a
+   * standalone host without routes — omits it (or sets it to `undefined`). A module feature-detects
+   * it: `context.navigation?.navigate("timelines")`.
    */
-  readonly navigation: ModuleUiNavigation | undefined;
+  readonly navigation?: ModuleUiNavigation | undefined;
 }
 
 export interface ModuleUiDisplayLocation {
diff --git a/packages/module-ui-sdk/tests/module-ui-contract.test.ts b/packages/module-ui-sdk/tests/module-ui-contract.test.ts
index 1451d4d..525a646 100644
--- a/packages/module-ui-sdk/tests/module-ui-contract.test.ts
+++ b/packages/module-ui-sdk/tests/module-ui-contract.test.ts
@@ -188,7 +188,6 @@ describe("the same module UI artifact hosted by two different hosts", () => {
         contributions: NO_MODULE_UI_CONTRIBUTIONS,
         display: undefined,
         moduleId,
-        navigation: undefined,
         api,
         principal: { kind: "anonymous" },
         permissions: { has: () => canPublish },
@@ -215,7 +214,6 @@ describe("the same module UI artifact hosted by two different hosts", () => {
         contributions: NO_MODULE_UI_CONTRIBUTIONS,
         display: { url: "https://announcements.example.org/display" },
         moduleId,
-        navigation: undefined,
         api,
         principal: { kind: "anonymous" },
         permissions: { has: () => canPublish },
diff --git a/packages/module-ui-sdk/tests/navigation.test.ts b/packages/module-ui-sdk/tests/navigation.test.ts
index 6ee4fce..6904837 100644
--- a/packages/module-ui-sdk/tests/navigation.test.ts
+++ b/packages/module-ui-sdk/tests/navigation.test.ts
@@ -3,6 +3,7 @@ import {
   type ModuleUiHostContext,
   type ModuleUiNavigation,
   ModuleUiNavigationError,
+  NO_MODULE_UI_CONTRIBUTIONS,
 } from "../src/index.js";
 
 /** The navigation capability's public surface (ADR 0063). Its behaviour is the host's: the
@@ -22,11 +23,26 @@ describe("module UI navigation contract", () => {
     }
   });
 
-  it("makes navigation a context member a host without pages leaves undefined", () => {
-    // A type-level contract: a context may say it has no navigation, as the display host does, and
-    // a module reads it through an optional check.
-    const describe = (context: Pick<ModuleUiHostContext, "navigation">): string =>
-      context.navigation?.location().path ?? "no navigation";
+  it("keeps a context built before navigation existed a complete, valid context", () => {
+    // Exactly the seven members every host supplied before ADR 0063, with no `navigation` member at
+    // all. This must keep compiling unchanged: `tsc` over this file is the compatibility proof, and
+    // `satisfies` makes the check exact rather than structural-by-accident.
+    const preNavigationContext = {
+      api: { request: async () => new Response(null, { status: 204 }) },
+      contributions: NO_MODULE_UI_CONTRIBUTIONS,
+      display: undefined,
+      moduleId: "announcements",
+      permissions: { has: () => false },
+      principal: { kind: "anonymous" },
+      realtime: { subscribe: () => ({ close: () => undefined }) },
+    } satisfies ModuleUiHostContext;
+    const asContext: ModuleUiHostContext = preNavigationContext;
+
+    expect("navigation" in asContext).toBe(false);
+    expect(asContext.navigation?.location().path).toBeUndefined();
+  });
+
+  it("lets a host supply navigation, omit it, or set it to undefined, and a module feature-detect it", () => {
     const navigation: ModuleUiNavigation = {
       link: () => ({ href: "/m/x", onClick: () => undefined }),
       location: () => ({ page: "x", path: "x" }),
@@ -34,7 +50,14 @@ describe("module UI navigation contract", () => {
       settings: undefined,
       subscribe: () => () => undefined,
     };
-    expect(describe({ navigation: undefined })).toBe("no navigation");
-    expect(describe({ navigation })).toBe("x");
+    const where = (context: Pick<ModuleUiHostContext, "navigation">): string =>
+      context.navigation?.location().path ?? "no navigation";
+
+    expect(where({ navigation })).toBe("x");
+    expect(where({})).toBe("no navigation");
+    expect(where({ navigation: undefined })).toBe("no navigation");
+    // Present, it must be the real capability — not any object.
+    // @ts-expect-error a navigation member must satisfy ModuleUiNavigation
+    expect(where({ navigation: { location: () => "x" } })).toBeDefined();
   });
 });
diff --git a/surfaces/shell/src/module-context.ts b/surfaces/shell/src/module-context.ts
index a904867..0431ae1 100644
--- a/surfaces/shell/src/module-context.ts
+++ b/surfaces/shell/src/module-context.ts
@@ -274,7 +274,7 @@ export interface CreateModuleUiContextOptions {
    * renderer without a real network. Production composition leaves it unset. */
   readonly importModule?: (url: string) => Promise<unknown>;
   /** The module's navigation capability (ADR 0063), from a host whose pages are addressable — the
-   * Dashboard. Omitted, the context carries `navigation: undefined`. */
+   * Dashboard. Omitted, the context omits the member, as it did before navigation existed. */
   readonly navigation?: ModuleUiNavigation;
 }
 
@@ -361,8 +361,8 @@ export function createModuleUiContext(options: CreateModuleUiContextOptions): Mo
     moduleId: options.descriptor.id,
     permissions: Object.freeze({ has: (permissionId: string) => granted.has(permissionId) }),
     // Only a host with addressable module pages supplies navigation (ADR 0063); the display host
-    // shows one screen and supplies none.
-    navigation: options.navigation,
+    // shows one screen and omits the member entirely, exactly as before navigation existed.
+    ...(options.navigation === undefined ? {} : { navigation: options.navigation }),
     principal: options.principal,
     realtime: createModuleRealtimeClient(options.config, options.descriptor),
   });
diff --git a/surfaces/shell/tests/display-app.test.tsx b/surfaces/shell/tests/display-app.test.tsx
index 24453cf..a289339 100644
--- a/surfaces/shell/tests/display-app.test.tsx
+++ b/surfaces/shell/tests/display-app.test.tsx
@@ -251,13 +251,12 @@ describe("display host — full-viewport boundary", () => {
       "contributions",
       "display",
       "moduleId",
-      "navigation",
       "permissions",
       "principal",
       "realtime",
     ]);
-    // A display is one screen with no pages: the display host offers no navigation (ADR 0063).
-    expect(seenContext?.navigation).toBeUndefined();
+    // A display is one screen with no pages: the display host omits navigation (ADR 0063).
+    expect(seenContext && "navigation" in seenContext).toBe(false);
     expect(seenContext?.principal).toEqual({ kind: "authenticated", userId: "user-1" });
     expect(isolatedText(query("display-module-container"))).toBe("permitted");
     expect(
diff --git a/surfaces/shell/tests/host-protocol.test.ts b/surfaces/shell/tests/host-protocol.test.ts
index a8271a5..65414bc 100644
--- a/surfaces/shell/tests/host-protocol.test.ts
+++ b/surfaces/shell/tests/host-protocol.test.ts
@@ -569,7 +569,7 @@ describe("module UI host context", () => {
     expect(context.display?.url).toBe("https://api.example.test/display/example");
   });
 
-  it("exposes exactly the eight contract members and the browser principal", () => {
+  it("exposes exactly the seven contract members and the browser principal", () => {
     const { implementation } = recordingFetch();
 
     const context = contextFor(implementation);
@@ -579,14 +579,14 @@ describe("module UI host context", () => {
       "contributions",
       "display",
       "moduleId",
-      "navigation",
       "permissions",
       "principal",
       "realtime",
     ]);
     expect(context.moduleId).toBe("example");
-    // Navigation comes only from a host with addressable pages (ADR 0063); this one supplies none.
-    expect(context.navigation).toBeUndefined();
+    // Navigation comes only from a host with addressable pages (ADR 0063). Without it the member is
+    // omitted, so the context is exactly the shape it was before navigation existed.
+    expect("navigation" in context).toBe(false);
     expect(context.principal).toEqual({ kind: "authenticated", userId: "user-1" });
   });
 
diff --git a/templates/module/tests/module-ui.test.ts b/templates/module/tests/module-ui.test.ts
index 1618e18..6dcc375 100644
--- a/templates/module/tests/module-ui.test.ts
+++ b/templates/module/tests/module-ui.test.ts
@@ -58,7 +58,6 @@ function recordingHost(options: {
     contributions: NO_MODULE_UI_CONTRIBUTIONS,
     display: undefined,
     moduleId: "example",
-    navigation: undefined,
     api,
     principal: { kind: "anonymous" },
     permissions: { has: () => options.canRead },