fix(core,cli): drain background notifications outside the subagent's ALS frame

packages/cli/src/ui/hooks/useGeminiStream.test.tsx

@@ -33,6 +33,8 @@ import {
   SendMessageType,
   ToolErrorType,
   ToolConfirmationOutcome,
+  getRuntimeContentGenerator,
+  runWithRuntimeContentGenerator,
 } from '@qwen-code/qwen-code-core';
 import type { Part, PartListUnion } from '@google/genai';
 import type { UseHistoryManagerReturn } from './useHistoryManager.js';
@@ -6435,6 +6437,50 @@ describe('useGeminiStream', () => {
           mockSendMessageStream.mock.calls[0][3].modelOverride,
         ).toBeUndefined();
       });
+
+      // Regression for #7156: progress setState calls issued from inside a
+      // background subagent's AsyncLocalStorage frame can batch with the
+      // notification trigger into one React commit, so the drain effect
+      // executes on a stack that still carries the subagent's frame. The
+      // drained turn — and every async continuation it starts — then
+      // resolves Config.getModel() to the subagent's runtime view and the
+      // main session switches onto the subagent's model. The drain effect
+      // must therefore run via runOutsideAgentContext. This test drives the
+      // notification callback from inside an agent frame (bypassing the
+      // producer-side guard in BackgroundTaskRegistry.emitNotification) and
+      // fails if the consumer-side wrapping is removed.
+      it('drains a notification outside a background agent ALS frame', async () => {
+        renderTestHook();
+        const callback = mockBackgroundShellRegistry.setNotificationCallback
+          .mock.calls[0][0] as (displayText: string, modelText: string) => void;
+
+        let capturedRuntimeView: unknown = 'unset';
+        mockSendMessageStream.mockImplementationOnce(() => {
+          capturedRuntimeView = getRuntimeContentGenerator();
+          return (async function* () {})();
+        });
+
+        const subagentView = {
+          contentGenerator: {},
+          contentGeneratorConfig: { model: 'small-default' },
+        } as never;
+        // The whole act() flush runs inside the agent frame, mirroring the
+        // contaminated React commit from the issue.
+        await runWithRuntimeContentGenerator(subagentView, async () => {
+          await act(async () => {
+            callback(
+              'Background shell "npm test" completed.',
+              '<task-notification>completed</task-notification>',
+            );
+          });
+        });
+
+        await waitFor(() => expect(mockSendMessageStream).toHaveBeenCalled());
+        expect(mockSendMessageStream.mock.calls[0][3]).toMatchObject({
+          type: SendMessageType.Notification,
+        });
+        expect(capturedRuntimeView).toBeUndefined();
+      });
     });
   });
 

packages/cli/src/ui/hooks/useGeminiStream.ts

@@ -13,6 +13,7 @@ import {
   useLayoutEffect,
 } from 'react';
 import {
+  runOutsideAgentContext,
   type Config,
   type EditorType,
   type GeminiClient,
@@ -3760,45 +3761,59 @@ export const useGeminiStream = (
       !isSubmittingQueryRef.current &&
       notificationQueueRef.current.length > 0
     ) {
-      const queue = notificationQueueRef.current;
-      const targetType = queue[0]!.sendMessageType;
-
-      // Cron prompts must run as individual turns — each needs its own
-      // slash/shell/@ preprocessing and approval cycle. Only batch
-      // Notification items (which pass through without preprocessing).
-      if (targetType === SendMessageType.Cron) {
-        const item = queue.shift()!;
-        addItem(
-          { type: 'notification' as const, text: item.displayText },
-          Date.now(),
-        );
-        submitQuery(item.modelText, item.sendMessageType, undefined, {
-          notificationDisplayText: item.displayText,
-          onDelivered: item.onDelivered,
-          onDeliveryFailed: item.onDeliveryFailed,
-        });
-        return;
-      }
+      // Consumer-side guard for #7156: this effect can run on a render pass
+      // that React batched together with progress setState calls issued from
+      // INSIDE a subagent's AsyncLocalStorage frame, in which case the whole
+      // synchronous effect stack — and every async continuation submitQuery
+      // starts — inherits the subagent's runtime view, and the notification
+      // turn resolves Config.getModel() to the SUBAGENT's model. Exiting the
+      // frame here guarantees the drained turn always runs on the main
+      // session's configuration, regardless of which producer's setState
+      // triggered the commit.
+      runOutsideAgentContext(() => {
+        const queue = notificationQueueRef.current;
+        const targetType = queue[0]!.sendMessageType;
+
+        // Cron prompts must run as individual turns — each needs its own
+        // slash/shell/@ preprocessing and approval cycle. Only batch
+        // Notification items (which pass through without preprocessing).
+        if (targetType === SendMessageType.Cron) {
+          const item = queue.shift()!;
+          addItem(
+            { type: 'notification' as const, text: item.displayText },
+            Date.now(),
+          );
+          submitQuery(item.modelText, item.sendMessageType, undefined, {
+            notificationDisplayText: item.displayText,
+            onDelivered: item.onDelivered,
+            onDeliveryFailed: item.onDeliveryFailed,
+          });
+          return;
+        }
 
-      // Drain contiguous leading Notification items into one batch.
-      let splitIdx = 0;
-      while (
-        splitIdx < queue.length &&
-        queue[splitIdx]!.sendMessageType === targetType
-      ) {
-        splitIdx++;
-      }
-      const batch = queue.splice(0, splitIdx);
+        // Drain contiguous leading Notification items into one batch.
+        let splitIdx = 0;
+        while (
+          splitIdx < queue.length &&
+          queue[splitIdx]!.sendMessageType === targetType
+        ) {
+          splitIdx++;
+        }
+        const batch = queue.splice(0, splitIdx);
 
-      const now = Date.now();
-      for (const item of batch) {
-        addItem({ type: 'notification' as const, text: item.displayText }, now);
-      }
+        const now = Date.now();
+        for (const item of batch) {
+          addItem(
+            { type: 'notification' as const, text: item.displayText },
+            now,
+          );
+        }
 
-      const combinedModelText = batch.map((e) => e.modelText).join('\n\n');
-      const combinedDisplayText = batch.map((e) => e.displayText).join('; ');
-      submitQuery(combinedModelText, targetType, undefined, {
-        notificationDisplayText: combinedDisplayText,
+        const combinedModelText = batch.map((e) => e.modelText).join('\n\n');
+        const combinedDisplayText = batch.map((e) => e.displayText).join('; ');
+        submitQuery(combinedModelText, targetType, undefined, {
+          notificationDisplayText: combinedDisplayText,
+        });
       });
     }
   }, [streamingState, submitQuery, notificationTrigger, addItem]);

packages/core/src/agents/background-tasks.test.ts

@@ -16,6 +16,12 @@ import {
   type BackgroundApproval,
   type BackgroundTaskEntry,
 } from './background-tasks.js';
+import {
+  getCurrentAgentId,
+  getRuntimeContentGenerator,
+  runWithAgentContext,
+  runWithRuntimeContentGenerator,
+} from './runtime/agent-context.js';
 import * as transcript from './agent-transcript.js';
 import { AgentEventEmitter, AgentEventType } from './runtime/agent-events.js';
 import { ToolConfirmationOutcome } from '../tools/tools.js';
@@ -52,6 +58,56 @@ function makeRegistration(
   };
 }
 
+describe('notification emission and agent context (#7156)', () => {
+  // A background agent's terminal transition fires inside its own
+  // AsyncLocalStorage frame, and ALS context follows every async
+  // continuation the notification callback starts (React state updates,
+  // the drain effect, the next conversation turn). The callback must
+  // therefore run with NO agent frame, or Config.getModel() resolves to
+  // the subagent's model for the notification turn and the main session's
+  // history can overflow the smaller context window.
+  it('invokes the notification callback outside the agent ALS frame', async () => {
+    const registry = new BackgroundTaskRegistry();
+    const seen: Array<{
+      agentId: string | null;
+      runtimeView: unknown;
+    }> = [];
+    registry.setNotificationCallback(() => {
+      seen.push({
+        agentId: getCurrentAgentId(),
+        runtimeView: getRuntimeContentGenerator(),
+      });
+    });
+
+    registry.register({
+      agentId: 'bg-1',
+      description: 'bg agent',
+      status: 'running',
+      startTime: Date.now(),
+      abortController: new AbortController(),
+      isBackgrounded: true,
+      outputFile: '/tmp/bg.jsonl',
+    });
+
+    const fakeView = {
+      contentGenerator: {} as never,
+      contentGeneratorConfig: { model: 'subagent-model' } as never,
+    };
+    await runWithAgentContext('bg-1', () =>
+      runWithRuntimeContentGenerator(fakeView, async () => {
+        // Sanity: we ARE inside the subagent frame here.
+        expect(getCurrentAgentId()).toBe('bg-1');
+        expect(getRuntimeContentGenerator()).toBe(fakeView);
+        registry.complete('bg-1', 'done');
+      }),
+    );
+
+    expect(seen).toHaveLength(1);
+    expect(seen[0]!.agentId).toBeNull();
+    expect(seen[0]!.runtimeView).toBeUndefined();
+  });
+});
+
 describe('BackgroundTaskRegistry', () => {
   let registry: BackgroundTaskRegistry;
 

packages/core/src/agents/background-tasks.ts

@@ -26,6 +26,7 @@ import { createDebugLogger } from '../utils/debugLogger.js';
 import { parsePositiveIntegerEnv } from '../utils/env.js';
 import { escapeXml } from '../utils/xml.js';
 import { patchAgentMeta } from './agent-transcript.js';
+import { runOutsideAgentContext } from './runtime/agent-context.js';
 import {
   AgentEventType,
   type AgentApprovalRequestEvent,
@@ -1428,7 +1429,18 @@ export class BackgroundTaskRegistry {
     };
 
     try {
-      this.notificationCallback(displayLine, xmlParts.join('\n'), meta);
+      // The terminal transition (complete/fail/cancel) that reaches this
+      // point runs inside the finished agent's AsyncLocalStorage frame, and
+      // ALS context follows every async continuation the callback starts —
+      // including the React state update that drains the notification into
+      // a new conversation turn. Without exiting the frame here, that turn
+      // resolves Config.getModel() to the SUBAGENT's model and the main
+      // session's history can overflow its smaller context window (#7156).
+      // A notification is main-session-owned, so emit it with no agent
+      // frame at all.
+      runOutsideAgentContext(() =>
+        this.notificationCallback!(displayLine, xmlParts.join('\n'), meta),
+      );
     } catch (error) {
       debugLogger.error('Failed to emit background notification:', error);
     }

packages/core/src/agents/runtime/agent-context.ts

@@ -98,6 +98,23 @@ export function getRuntimeContentGenerator():
   return storage.getStore()?.runtimeView;
 }
 
+/**
+ * Runs `fn` with NO agent frame on the async-local stack, so
+ * `Config.getModel()` / `getContentGeneratorConfig()` resolve to the main
+ * session's configuration and `getCurrentAgentId()` returns null.
+ *
+ * AsyncLocalStorage context propagates through every async continuation
+ * started inside `fn` — React state updates, queued microtasks, timers —
+ * which is exactly how a background agent's runtime view leaked into the
+ * notification drain and switched the main session onto the subagent's
+ * model (#7156). Wrap main-session-owned work that can be triggered from
+ * inside an agent frame (notification emission, completion bookkeeping)
+ * with this helper.
+ */
+export function runOutsideAgentContext<T>(fn: () => T): T {
+  return storage.exit(fn);
+}
+
 /**
  * True when there is no active agent frame — i.e. we are in the top-level
  * user session, not inside a sub-agent. The canonical "top-level only"

packages/core/src/index.ts

@@ -62,6 +62,7 @@ export {
   getRuntimeContentGenerator,
   runWithRuntimeContentGenerator,
   type RuntimeContentGeneratorView,
+  runOutsideAgentContext,
 } from './agents/runtime/agent-context.js';
 export * from './core/reasoning-effort.js';
 export * from './core/coreToolScheduler.js';