diff --git a/packages/core/agent-loop/src/index.ts b/packages/core/agent-loop/src/index.ts
index c37cce6a1a..0b8879c2b7 100644
--- a/packages/core/agent-loop/src/index.ts
+++ b/packages/core/agent-loop/src/index.ts
@@ -120,7 +120,11 @@ export class AgentLoop extends Service implements AgentFactory {
                 this.ctx.logger.warn(`agent "${id}": config-driven resume of "${resumeSessionId}" failed: ${String(error)}`)
               })
           })
-          return () => void fiber.dispose()
+          // Return the EXACT child-fiber disposer. Cordis moves a returned
+          // effect into this labeled owner's teardown tree by function
+          // identity; a wrapper would leave the child as a concurrent sibling
+          // and could discard its async quiescence promise.
+          return fiber.dispose
         }, `agentLoop.resume(${id})`)
       } else {
         this.create(id, options, cwd === undefined ? {} : { cwd })
diff --git a/packages/core/agent-loop/tests/config-session-id.spec.ts b/packages/core/agent-loop/tests/config-session-id.spec.ts
index 97f04cbbca..07d6cd9e9b 100644
--- a/packages/core/agent-loop/tests/config-session-id.spec.ts
+++ b/packages/core/agent-loop/tests/config-session-id.spec.ts
@@ -24,6 +24,24 @@ function waitForIdle(ctx: Context, agent: ReactLoopAgent): Promise<void> {
 }
 
 describe('config-driven session id', () => {
+  it('identity-nests the deferred resume fiber under its labeled owner effect', async () => {
+    const ctx = new Context()
+    await ctx.plugin(LlmService)
+    await ctx.plugin(SessionStore)
+    await ctx.plugin(SystemPrompt)
+    await ctx.plugin(ToolRegistry)
+    await ctx.plugin(AgentRegistry)
+    const loopFiber = await ctx.plugin(AgentLoop, {
+      agents: [{ id: AgentId('main'), model: 'mock', resumeSessionId: SessionId('deferred') }],
+    })
+
+    const resumeEffect = loopFiber.getEffects().find(effect => effect.label === 'agentLoop.resume(main)')
+    expect(resumeEffect?.children.map(child => child.label)).toEqual(['ctx.plugin()'])
+    expect(loopFiber.getEffects().filter(effect => effect.label === 'ctx.plugin()')).toEqual([])
+
+    await loopFiber.dispose()
+  })
+
   it('config-driven create uses a fresh ${id}-session-<uuid> per run (restart-safe)', async () => {
     const root = await mkdtemp(join(tmpdir(), 'dsh-cfg-session-'))
     dirs.push(root)