diff --git a/packages/provider-muse/src/server/adapter.test.ts b/packages/provider-muse/src/server/adapter.test.ts
index 847c2b4551c59..cc84894ac6ef9 100644
--- a/packages/provider-muse/src/server/adapter.test.ts
+++ b/packages/provider-muse/src/server/adapter.test.ts
@@ -850,16 +850,33 @@ describe("MuseAdapterV2", () => {
       }).pipe(Effect.provide(testLayer)),
   );
 
-  it.effect(
-    "closes a newly opened host when native session registration returns another identity",
-    () =>
+  it.effect.each([
+    {
+      reason: "another identity",
+      method: "session/start",
+      sessionId: "unexpected-session",
+      initialNativeThreadId: undefined,
+      history: { items: [] },
+    },
+    {
+      reason: "an unavailable projection",
+      method: "session/resume",
+      sessionId: "saved-session",
+      initialNativeThreadId: "saved-session",
+      history: { items: null, mode: "none", noneReason: "projectionUnavailable" },
+    },
+  ])(
+    "closes a newly opened host when native session registration returns $reason",
+    ({ method, sessionId, initialNativeThreadId, history }) =>
       Effect.gen(function* () {
         const fake = yield* makeFakeMuse();
-        fake.queueResponse("session/start", {
-          session: { sessionId: "unexpected-session", modelId: MODEL, activeTurnId: null },
-          history: { items: [] },
+        fake.queueResponse(method, {
+          session: { sessionId, modelId: MODEL, activeTurnId: null },
+          history,
         });
-        const result = yield* makeHarness(fake).pipe(Effect.exit);
+        const result = yield* makeHarness(fake, INSTANCE_ID, initialNativeThreadId).pipe(
+          Effect.exit,
+        );
         assert.strictEqual(result._tag, "Failure");
         yield* Effect.promise(() => fake.host.exited);
         assert.strictEqual(fake.closeCount(), 1);
@@ -1441,6 +1458,11 @@ describe("MuseAdapterV2", () => {
         text: "Previous answer",
       };
       fake.setHistory([nativeItem]);
+      fake.queueResponse("session/resume", {
+        session: { sessionId: "saved-session", modelId: MODEL, activeTurnId: null },
+        viewCursor: "",
+        history: { items: null, mode: "none", noneReason: "excluded" },
+      });
       const harness = yield* makeHarness(fake, INSTANCE_ID, "saved-session");
       const resumed = yield* fake.takeCall("session/resume");
       assert.strictEqual(resumed.params.sessionId, "saved-session");
diff --git a/packages/provider-muse/src/server/adapter.ts b/packages/provider-muse/src/server/adapter.ts
index b29f8d51947bf..fd1526a428c6e 100644
--- a/packages/provider-muse/src/server/adapter.ts
+++ b/packages/provider-muse/src/server/adapter.ts
@@ -1879,6 +1879,10 @@ export const makeMuseAdapterV2 = Effect.fn("makeMuseAdapterV2")(function* (
           );
           if (result.session.sessionId !== nativeSessionId)
             return yield* protocolError("Muse returned a different session identity");
+          if (result.history?.noneReason === "projectionUnavailable")
+            return yield* protocolError(
+              "Muse cannot stream this session because its live view is unavailable",
+            );
           if (requestedId)
             yield* request("session/setApprovalMode", {
               mode: museApprovalMode(args.runtimePolicy.runtimeMode),
diff --git a/packages/provider-muse/src/server/protocol.ts b/packages/provider-muse/src/server/protocol.ts
index 9c3e7c40d957b..0c1fdad7db3b2 100644
--- a/packages/provider-muse/src/server/protocol.ts
+++ b/packages/provider-muse/src/server/protocol.ts
@@ -70,6 +70,7 @@ export const MuseSessionResult = Schema.Struct({
   history: Schema.optional(
     Schema.Struct({
       items: Schema.NullOr(Schema.Array(MuseItem)),
+      noneReason: Schema.optional(Schema.String),
       snapshot: Schema.optional(
         Schema.NullOr(
           Schema.Struct({