refactor(core): move background injection from UI to ExecutionLifecycleService

settleExecution now calls injectionService.addInjection() directly
when a backgrounded execution completes, removing the bridge useEffect
from AppContainer. The UI just wires the injection service once at init
via setInjectionService().

packages/core/src/services/executionLifecycleService.test.ts

@@ -10,6 +10,7 @@ import {
   type ExecutionHandle,
   type ExecutionResult,
 } from './executionLifecycleService.js';
+import { InjectionService } from '../config/injectionService.js';
 
 function createResult(
   overrides: Partial<ExecutionResult> = {},
@@ -628,5 +629,59 @@ describe('ExecutionLifecycleService', () => {
 
       ExecutionLifecycleService.offBackgroundComplete(listener);
     });
+
+    it('injects directly into InjectionService when wired via setInjectionService', async () => {
+      const injectionService = new InjectionService(() => true);
+      ExecutionLifecycleService.setInjectionService(injectionService);
+
+      const injectionListener = vi.fn();
+      injectionService.onInjection(injectionListener);
+
+      const handle = ExecutionLifecycleService.createExecution(
+        '',
+        undefined,
+        'remote_agent',
+        (output) => `[Completed] ${output}`,
+        undefined,
+        'inject',
+      );
+      const executionId = handle.pid!;
+
+      ExecutionLifecycleService.appendOutput(executionId, 'agent output');
+      ExecutionLifecycleService.background(executionId);
+      await handle.result;
+
+      ExecutionLifecycleService.completeExecution(executionId);
+
+      expect(injectionListener).toHaveBeenCalledWith(
+        '[Completed] agent output',
+        'background_completion',
+      );
+    });
+
+    it('does not inject into InjectionService for silent behavior', async () => {
+      const injectionService = new InjectionService(() => true);
+      ExecutionLifecycleService.setInjectionService(injectionService);
+
+      const injectionListener = vi.fn();
+      injectionService.onInjection(injectionListener);
+
+      const handle = ExecutionLifecycleService.createExecution(
+        '',
+        undefined,
+        'none',
+        () => 'should not inject',
+        undefined,
+        'silent',
+      );
+      const executionId = handle.pid!;
+
+      ExecutionLifecycleService.background(executionId);
+      await handle.result;
+
+      ExecutionLifecycleService.completeExecution(executionId);
+
+      expect(injectionListener).not.toHaveBeenCalled();
+    });
   });
 });

packages/core/src/services/executionLifecycleService.ts

@@ -155,6 +155,16 @@ const NON_PROCESS_EXECUTION_ID_START = 2_000_000_000;
 export class ExecutionLifecycleService {
   private static readonly EXIT_INFO_TTL_MS = 5 * 60 * 1000;
   private static nextExecutionId = NON_PROCESS_EXECUTION_ID_START;
+  private static injectionService: InjectionService | null = null;
+
+  /**
+   * Connects the lifecycle service to the injection service so that
+   * backgrounded executions are reinjected into the model conversation
+   * directly from the backend — no UI hop needed.
+   */
+  static setInjectionService(service: InjectionService): void {
+    this.injectionService = service;
+  }
 
   private static activeExecutions = new Map<number, ManagedExecutionState>();
   private static activeResolvers = new Map<
@@ -271,6 +281,7 @@ export class ExecutionLifecycleService {
     this.backgroundCompletionListeners.clear();
     this.injectionService = null;
     this.backgroundStartListeners.clear();
+    this.injectionService = null;
     this.nextExecutionId = NON_PROCESS_EXECUTION_ID_START;
   }
 
@@ -388,6 +399,15 @@ export class ExecutionLifecycleService {
         behavior !== 'silent' && execution.formatInjection
           ? execution.formatInjection(result.output, result.error)
           : null;
+
+      // Inject directly into the model conversation from the backend.
+      if (injectionText && this.injectionService) {
+        this.injectionService.addInjection(
+          injectionText,
+          'background_completion',
+        );
+      }
+
       const info: BackgroundCompletionInfo = {
         executionId,
         executionMethod: execution.executionMethod,