fix(cloud-agent): propagate taskRunId through codex loadSession (#1720)

## Problem

`newSession` and `unstable_resumeSession` both carry `_meta.taskRunId` / `taskId` into `sessionState` and emit `_posthog/sdk_session` on cloud runs. `loadSession` dropped them on the floor. Re-attaching a desktop client to an existing cloud codex session therefore silenced `TURN_COMPLETE` and `USAGE_UPDATE` on subsequent prompts (both gated on `sessionState.taskRunId`), and the adapter→session mapping was never published.

## Changes

In `CodexAcpAgent.loadSession`, propagate `taskRunId` / `taskId` into sessionState and fire `_posthog/sdk_session` when `taskRunId` is present, matching the other session-creation paths.

## How did you test this?

- Two new unit tests: `taskRunId` is propagated and `SDK_SESSION` fires when present; no extNotification is emitted when `taskRunId` is absent.
- Full `@posthog/agent` suite green.

Author: tatoalo

packages/agent/src/adapters/codex/codex-agent.test.ts

@@ -107,6 +107,48 @@ describe("CodexAcpAgent", () => {
     ).toBe("read-only");
   });
 
+  it("propagates taskRunId and fires SDK_SESSION when loading a cloud session", async () => {
+    const { agent, client } = createAgent();
+    mockCodexConnection.loadSession.mockResolvedValue({
+      modes: { currentModeId: "auto", availableModes: [] },
+      configOptions: [],
+    } satisfies Partial<LoadSessionResponse>);
+
+    await agent.loadSession({
+      sessionId: "session-1",
+      cwd: process.cwd(),
+      _meta: { taskRunId: "run-1", taskId: "task-1" },
+    } as never);
+
+    expect(
+      (agent as unknown as { sessionState: { taskRunId?: string } })
+        .sessionState.taskRunId,
+    ).toBe("run-1");
+    expect(client.extNotification).toHaveBeenCalledWith(
+      "_posthog/sdk_session",
+      {
+        taskRunId: "run-1",
+        sessionId: "session-1",
+        adapter: "codex",
+      },
+    );
+  });
+
+  it("does not emit SDK_SESSION on loadSession when taskRunId is absent", async () => {
+    const { agent, client } = createAgent();
+    mockCodexConnection.loadSession.mockResolvedValue({
+      modes: { currentModeId: "auto", availableModes: [] },
+      configOptions: [],
+    } satisfies Partial<LoadSessionResponse>);
+
+    await agent.loadSession({
+      sessionId: "session-1",
+      cwd: process.cwd(),
+    } as never);
+
+    expect(client.extNotification).not.toHaveBeenCalled();
+  });
+
   it("preserves the live session mode when loading an existing session", async () => {
     const { agent } = createAgent();
     mockCodexConnection.loadSession.mockResolvedValue({

packages/agent/src/adapters/codex/codex-agent.ts

@@ -267,13 +267,27 @@ export class CodexAcpAgent extends BaseAcpAgent {
       meta?.permissionMode,
     );
 
+    // Carry taskRunId/taskId across load so prompt() still emits cloud
+    // notifications (TURN_COMPLETE, USAGE_UPDATE) after a reload. newSession
+    // and unstable_resumeSession both do this; loadSession historically did
+    // not, which silently broke task-completion tracking on re-attach.
     this.sessionState = createSessionState(params.sessionId, params.cwd, {
+      taskRunId: meta?.taskRunId,
+      taskId: meta?.taskId ?? meta?.persistence?.taskId,
       modeId: response.modes?.currentModeId ?? "auto",
       permissionMode: currentPermissionMode,
     });
     this.sessionId = params.sessionId;
     this.sessionState.configOptions = response.configOptions ?? [];
 
+    if (meta?.taskRunId) {
+      await this.client.extNotification(POSTHOG_NOTIFICATIONS.SDK_SESSION, {
+        taskRunId: meta.taskRunId,
+        sessionId: params.sessionId,
+        adapter: "codex",
+      });
+    }
+
     return response;
   }