fix: retire model selection ownership

ui/src/pages/chat/chat-command-executor.test.ts

@@ -28,6 +28,7 @@ function createSessionCapability(client: GatewayBrowserClient): SessionCapabilit
     create: async () => null,
     patch: (key: string, patch: SessionPatch, options: SessionPatchOptions = {}) =>
       request("sessions.patch", { key, agentId: options.agentId, ...patch }),
+    setModelOverride: () => undefined,
     delete: async () => false,
     deleteMany: async () => ({ deleted: [], errors: [], preservedWorktrees: [] }),
     reset: async () => true,
@@ -176,6 +177,7 @@ describe("executeSlashCommand directives", () => {
       expect.objectContaining({
         agentId: "work",
         deferModelOverride: true,
+        ownsModelOverride: expect.any(Function),
       }),
     );
     expect(setModelOverride).toHaveBeenCalledWith("global", "openai/gpt-5-mini");

ui/src/pages/chat/chat-command-executor.ts

@@ -316,6 +316,7 @@ async function executeModel(
       },
       {
         deferModelOverride: true,
+        ownsModelOverride: context.ownsModelOverride,
         reconcile: async (result) => {
           const resolvedModel = result.resolved?.model ?? requestedModel;
           let resolvedValue = resolvePreferredServerChatModelValue(

ui/src/pages/chat/chat-pane-context.ts

@@ -14,6 +14,7 @@ import { resolveSessionKey } from "../../lib/sessions/index.ts";
 import {
   buildAgentMainSessionKey,
   canonicalUiSessionKeyForPersistence,
+  isUiGlobalSessionKey,
   parseAgentSessionKey,
   resolveUiConfiguredMainKey,
   uiSessionEventMatches,
@@ -26,6 +27,7 @@ import { resolveAssistantAttachmentAuthToken } from "./chat-pane-state.ts";
 import { markQueuedChatSendsWaitingForReconnect } from "./chat-queue.ts";
 import { stopChatRealtimeTalk } from "./chat-realtime.ts";
 import { retryReconnectableQueuedChatSends } from "./chat-send-actions.ts";
+import { retireChatModelSelectionOwnership } from "./chat-session.ts";
 import {
   invalidateChatMetadataCache,
   refreshChatModelAuthStatus,
@@ -169,6 +171,7 @@ export abstract class ChatPaneContext extends ChatPaneLifecycle {
     }
     const previousMediaAuthToken = resolveAssistantAttachmentAuthToken(state);
     const wasConnected = state.connected;
+    const previousAssistantAgentId = state.assistantAgentId;
     const previousSidebarSessionKey = canonicalUiSessionKeyForPersistence(state, state.sessionKey);
     const connectionLifecycle = (this.gatewayConnectionLifecycle ??=
       createGatewayConnectionLifecycle({
@@ -216,6 +219,13 @@ export abstract class ChatPaneContext extends ChatPaneLifecycle {
       this.resetOlderMessagesViewport();
       state.chatLoading = false;
     }
+    if (
+      sourceChanged ||
+      (previousAssistantAgentId !== snapshot.assistantAgentId &&
+        isUiGlobalSessionKey(state.sessionKey))
+    ) {
+      retireChatModelSelectionOwnership(state);
+    }
     state.client = snapshot.client;
     state.connected = snapshot.phase === "connected";
     state.connectionEpoch = this.connectionGeneration;

ui/src/pages/chat/chat-pane-lifecycle.test.ts

@@ -920,6 +920,51 @@ describe("chat pane connection lifecycle", () => {
     expect(state.chatIsProgrammaticScroll).toBe(false);
   });
 
+  it("retires pending model selection state when the Gateway owner changes", () => {
+    const client = { request: vi.fn() } as unknown as GatewayBrowserClient;
+    const setModelOverride = vi.fn();
+    const sessions = { setModelOverride } as unknown as SessionCapability;
+    const { pane, state } = createTestChatPane({ client, sessions });
+    state.sessionKey = "global";
+    state.chatModelSwitchPromises = {
+      global: new Promise<boolean>(() => {}),
+    };
+
+    pane.applyGatewaySnapshot({
+      ...pane.context.gateway.snapshot,
+      client,
+      phase: "reconnecting",
+      hello: null,
+    });
+
+    expect(state.chatModelSwitchPromises).toEqual({});
+    expect(setModelOverride).toHaveBeenCalledWith("global", undefined);
+  });
+
+  it("retires pending global model selection state when the selected agent changes", () => {
+    const client = { request: vi.fn() } as unknown as GatewayBrowserClient;
+    const setModelOverride = vi.fn();
+    const sessions = { setModelOverride } as unknown as SessionCapability;
+    const { pane, state } = createTestChatPane({ client, sessions });
+    const snapshot = {
+      ...pane.context.gateway.snapshot,
+      client,
+      phase: "connected" as const,
+      assistantAgentId: "work",
+    };
+    pane.applyGatewaySnapshot(snapshot);
+    state.sessionKey = "global";
+    state.chatModelSwitchPromises = {
+      global: new Promise<boolean>(() => {}),
+    };
+    setModelOverride.mockClear();
+
+    pane.applyGatewaySnapshot({ ...snapshot, assistantAgentId: "main" });
+
+    expect(state.chatModelSwitchPromises).toEqual({});
+    expect(setModelOverride).toHaveBeenCalledWith("global", undefined);
+  });
+
   it("refreshes the transcript before secondary hydration after a same-client reconnect", () => {
     const request = vi.fn(() => new Promise<never>(() => {}));
     const client = {

ui/src/pages/chat/chat-session.ts

@@ -54,6 +54,25 @@ type ChatIdleSessionReconciliationHost = SessionScopeHost & {
   sessionsResult?: SessionsListResult | null;
 };
 
+export function retireChatModelSelectionOwnership(
+  host: Pick<
+    ChatModelSettingsHost,
+    "chatModelSwitchPromises" | "requestUpdate" | "sessionKey" | "sessions"
+  >,
+): void {
+  const hasPendingSwitch = Object.keys(host.chatModelSwitchPromises ?? {}).length > 0;
+  const hasModelOverride = Object.hasOwn(
+    host.sessions.state?.modelOverrides ?? {},
+    host.sessionKey,
+  );
+  if (!hasPendingSwitch && !hasModelOverride) {
+    return;
+  }
+  host.chatModelSwitchPromises = {};
+  host.sessions.setModelOverride(host.sessionKey, undefined);
+  host.requestUpdate?.();
+}
+
 function buildChatSessionListOptions(
   state: ChatSessionListHost,
   options: { offset?: number; append?: boolean; search?: string | null } = {},

ui/src/pages/chat/chat-state-page.ts

@@ -4,7 +4,10 @@ import { fetchAssistantIdentity } from "../../app/assistant-identity.ts";
 import type { ApplicationContext } from "../../app/context.ts";
 import { loadLocalUserIdentity, loadSettings, patchSettings } from "../../app/settings.ts";
 import { resolveSafeExternalUrl } from "../../lib/open-external-url.ts";
-import { canonicalUiSessionKeyForPersistence } from "../../lib/sessions/session-key.ts";
+import {
+  canonicalUiSessionKeyForPersistence,
+  isUiGlobalSessionKey,
+} from "../../lib/sessions/session-key.ts";
 import { resolveAgentIdForSession } from "./chat-avatar.ts";
 import { removeQueuedMessage } from "./chat-queue.ts";
 import { attachChatRealtimeActions, createInitialChatRealtimeState } from "./chat-realtime.ts";
@@ -14,6 +17,7 @@ import {
   steerQueuedChatMessage,
 } from "./chat-send-actions.ts";
 import { handleSendChat } from "./chat-send-submit.ts";
+import { retireChatModelSelectionOwnership } from "./chat-session.ts";
 import type { ChatPageHost } from "./chat-state-host.ts";
 import {
   handleChatDraftChange,
@@ -86,6 +90,12 @@ async function loadPageAssistantIdentity(
     ) {
       return;
     }
+    if (
+      state.assistantAgentId !== (identity.agentId ?? null) &&
+      isUiGlobalSessionKey(state.sessionKey)
+    ) {
+      retireChatModelSelectionOwnership(state);
+    }
     state.assistantName = identity.name;
     state.assistantAvatar = identity.avatar;
     state.assistantAvatarSource = identity.avatarSource ?? null;