ADE-56: Guard agentChatGetEventHistory IPC handler against null agentChatService in runtime-backed mode

apps/desktop/src/main/services/ipc/registerIpc.ts

@@ -5859,9 +5859,16 @@ export function registerIpc({
     _event,
     arg: { sessionId?: string; maxEvents?: number },
   ): Promise<AgentChatEventHistorySnapshot> => {
-    const ctx = ensureAgentChatContext();
+    const ctx = getCtx();
     const sessionId = typeof arg?.sessionId === "string" ? arg.sessionId.trim() : "";
     if (!sessionId) return { sessionId: "", events: [], truncated: false, sessionFound: false };
+    const service = ctx.agentChatService;
+    if (
+      !service ||
+      typeof (service as unknown as { getChatEventHistory?: unknown }).getChatEventHistory !== "function"
+    ) {
+      return { sessionId, events: [], truncated: false, sessionFound: false };
+    }
     // Only forward maxEvents when it is a finite positive number; the service
     // layer applies its own clamp but guarding here avoids ambiguous NaN/0
     // inputs from untrusted renderer IPC.
@@ -5870,7 +5877,7 @@ export function registerIpc({
       rawMaxEvents != null && Number.isFinite(rawMaxEvents) && rawMaxEvents > 0
         ? rawMaxEvents
         : undefined;
-    return ctx.agentChatService.getChatEventHistory(sessionId, maxEvents != null ? { maxEvents } : undefined);
+    return service.getChatEventHistory(sessionId, maxEvents != null ? { maxEvents } : undefined);
   });
 
   ipcMain.handle(IPC.agentChatReadTranscript, async (

apps/desktop/src/main/services/ipc/runtimeBridge.test.ts

@@ -892,6 +892,99 @@ describe("registerIpc sync bridge", () => {
     expect(listSessions).toHaveBeenCalledWith("lane-1", { includeAutomation: true });
   });
 
+  it("returns an empty chat event history when the agent chat service is unavailable", async () => {
+    registerIpc({
+      getCtx: () => ({
+        agentChatService: null,
+      }) as any,
+      getWindowSession: () => ({
+        windowId: 7,
+        project: { rootPath: "/repo", displayName: "Repo" } as any,
+        binding: localBinding("/repo"),
+      }),
+      switchProjectFromDialog: vi.fn(),
+      closeCurrentProject: vi.fn(),
+      closeProjectByPath: vi.fn(),
+      globalStatePath: "/tmp/ade-state.json",
+    });
+
+    await expect(
+      ipcHandlers.get(IPC.agentChatGetEventHistory)?.(
+        eventForSender(),
+        { sessionId: " chat-1 ", maxEvents: 10 },
+      ),
+    ).resolves.toEqual({
+      sessionId: "chat-1",
+      events: [],
+      truncated: false,
+      sessionFound: false,
+    });
+  });
+
+  it("returns an empty chat event history when the agent chat service lacks event history support", async () => {
+    registerIpc({
+      getCtx: () => ({
+        agentChatService: {},
+      }) as any,
+      getWindowSession: () => ({
+        windowId: 7,
+        project: { rootPath: "/repo", displayName: "Repo" } as any,
+        binding: localBinding("/repo"),
+      }),
+      switchProjectFromDialog: vi.fn(),
+      closeCurrentProject: vi.fn(),
+      closeProjectByPath: vi.fn(),
+      globalStatePath: "/tmp/ade-state.json",
+    });
+
+    await expect(
+      ipcHandlers.get(IPC.agentChatGetEventHistory)?.(
+        eventForSender(),
+        { sessionId: " chat-1 ", maxEvents: 10 },
+      ),
+    ).resolves.toEqual({
+      sessionId: "chat-1",
+      events: [],
+      truncated: false,
+      sessionFound: false,
+    });
+  });
+
+  it("forwards chat event history requests when the agent chat service is available", async () => {
+    const snapshot = {
+      sessionId: "chat-1",
+      events: [],
+      truncated: false,
+      sessionFound: true,
+    };
+    const getChatEventHistory = vi.fn(() => snapshot);
+    registerIpc({
+      getCtx: () => ({
+        agentChatService: {
+          getChatEventHistory,
+        },
+      }) as any,
+      getWindowSession: () => ({
+        windowId: 7,
+        project: { rootPath: "/repo", displayName: "Repo" } as any,
+        binding: localBinding("/repo"),
+      }),
+      switchProjectFromDialog: vi.fn(),
+      closeCurrentProject: vi.fn(),
+      closeProjectByPath: vi.fn(),
+      globalStatePath: "/tmp/ade-state.json",
+    });
+
+    await expect(
+      ipcHandlers.get(IPC.agentChatGetEventHistory)?.(
+        eventForSender(),
+        { sessionId: " chat-1 ", maxEvents: 25 },
+      ),
+    ).resolves.toBe(snapshot);
+
+    expect(getChatEventHistory).toHaveBeenCalledWith("chat-1", { maxEvents: 25 });
+  });
+
   it("disposes a live terminal runtime before deleting the session", async () => {
     const terminalSession = {
       id: "terminal-1",