review fix: preserve idle waiter quiescence

.agents/notes/implemented/simplification/2026-07-17-one-send-one-turn.i18n.yaml

@@ -2,5 +2,5 @@
 # side as of the last confirmed-consistent state. Both languages carry equal authority;
 # after editing either side, bring the other along and re-record with:
 #   pnpm run verify-translation-pairing --write
-2026-07-17-one-send-one-turn.md: 9534574e767d319427b6750b87ac391ed593164d
-2026-07-17-one-send-one-turn.zh.md: e3cd3c9f6c8951b1f1124a139286ba5e6f3b7fbd
+2026-07-17-one-send-one-turn.md: 852a2f24d33d88933568fe1d1d937e10003202df
+2026-07-17-one-send-one-turn.zh.md: f40086ee202bf74e4207081a402737d86e9dfa87

.agents/notes/implemented/simplification/2026-07-17-one-send-one-turn.md

@@ -8,13 +8,13 @@ English | [中文](2026-07-17-one-send-one-turn.zh.md)
 
 An ordinary `Agent.send()` payload is one complete caller message. Opportunistically draining every waiting payload into one turn would make adjacent calls share a boundary according to driver timing: calls from one synchronous stack, neighboring microtasks, event listeners, and model callbacks could be grouped differently even though callers used the same API.
 
-An ordinary turn owns prompt admission, `turn/start`, `turn/end`, and the durability checkpoint. Combining messages would let a later ordinary message join an earlier message's model request instead of observing the earlier ordinary turn's closed result in the same session log, while mixed allowed and blocked prompts would require lifecycle states no caller explicitly requested.
+An ordinary turn contains prompt admission, `turn/start`, `turn/end`, and the durability checkpoint. Combining messages would let a later ordinary message join an earlier message's model request instead of observing the earlier ordinary turn's closed result in the same session log, while mixed allowed and blocked prompts would require lifecycle states no caller explicitly requested.
 
 `steer()` already expresses joining the active turn, while `inject()` records model-facing context without acting as an ordinary message. Implicit ordinary-send batching would make `send()` overlap both explicit operations instead of preserving a single meaning.
 
 ## Decision
 
-Each successful `send()` synchronously validates agent state, snapshots and freezes content, appends one independent FIFO item, and publishes `agent/queued`. The loop dequeues at most one ordinary item for each turn start. If two ordinary items are both claimed, the second ordinary turn starts only after the first ordinary turn ends and its durability checkpoint settles; broad cancellation, disposal, or a pre-start failure can discard an unstarted item without creating an empty turn.
+Each successful `send()` synchronously validates agent state, snapshots and freezes content, appends one independent FIFO item, and publishes `agent/queued`. The loop dequeues at most one ordinary item for each turn start. If two ordinary items both reach turn processing, the second ordinary turn starts only after the first ordinary turn ends and its durability checkpoint settles; broad cancellation, disposal, or a pre-start failure can discard an unstarted item without creating an empty turn.
 
 Prompt admission decides one message. An allowed prompt becomes that turn's `user/message`; a blocked prompt appends one durable `prompt/blocked` and ends that one-message turn as `rejected`. There are no mixed-batch or all-blocked-batch branches.
 
@@ -34,6 +34,6 @@ Running `steer()` appends to the active turn's steering FIFO. Idle `steer()` del
 
 ## Consequences
 
-Ordinary turn boundaries are deterministic, and a claimed FIFO successor observes the preceding claimed ordinary turn's closed session result after that turn's checkpoint settles; settlement does not mean a failed flush became durable. Several queued items can still run under one global `running` interval, and broad cancellation can discard the entire unstarted tail, so status and quiescence remain agent-wide observations rather than per-message results.
+Ordinary turn boundaries are deterministic, and a FIFO successor that reaches turn processing observes the preceding completed ordinary turn's closed session result after that turn's checkpoint settles; settlement does not mean a failed flush became durable. Several queued items can still run under one global `running` interval, and broad cancellation can discard the entire unstarted tail, so status and quiescence remain agent-wide observations rather than per-message results.
 
 Workloads that relied on coincidental ordinary-send batching make more model requests, incur more checkpoints, and may take longer to drain; FIFO queues may grow under sustained producers. Ordinary-send batching can return only through an explicit measured contract.

.agents/notes/implemented/simplification/2026-07-17-one-send-one-turn.zh.md

@@ -8,13 +8,13 @@ Status: implemented
 
 每次普通 `Agent.send()` 接受的载荷都是一条完整的调用方消息。如果机会式地把所有待处理载荷放入同一个轮次，相邻调用是否共享边界就会取决于驱动器的运行时机：即使调用方使用相同 API，来自同一个同步调用栈、相邻微任务、事件监听器和模型回调的调用也可能产生不同分组。
 
-普通轮次拥有提示词准入、`turn/start`、`turn/end` 和持久性检查点。合并消息会让后一条普通消息加入前一条普通消息的模型请求，无法观察同一会话日志中前一个已关闭普通轮次的结果；获准与被阻止提示词的混合还会引入调用方从未显式请求的生命周期状态。
+普通轮次包含提示词准入、`turn/start`、`turn/end` 和持久性检查点。合并消息会让后一条普通消息加入前一条普通消息的模型请求，无法观察同一会话日志中前一个已关闭普通轮次的结果；获准与被阻止提示词的混合还会引入调用方从未显式请求的生命周期状态。
 
-`steer()` 已经用于表达加入当前轮次，`inject()` 则记录面向模型的上下文而不充当普通消息。普通 `send()` 的隐式批处理会让 `send()` 与这两种显式操作产生语义重叠，无法保持单一含义。
+`steer()` 已经用于表达加入当前轮次，`inject()` 则记录面向模型的上下文而不充当普通消息。普通 send 的隐式批处理会让 `send()` 与这两种显式操作产生语义重叠，无法保持单一含义。
 
 ## 决策
 
-每次成功的 `send()` 都会同步校验 agent（智能体）状态、创建并冻结内容快照、追加一个独立的 FIFO 队列项，然后发布 `agent/queued`。agent loop（智能体循环）在每个轮次开始时最多取出一个普通队列项。如果两个普通队列项最终都被认领，第二个普通轮次只能在第一个普通轮次结束且其持久性检查点处理结束后开始；广义取消、dispose（资源释放）或启动前失败可以丢弃尚未启动的队列项，而不创建空轮次。
+每次成功的 `send()` 都会同步校验 agent（智能体）状态、创建并冻结内容快照、追加一个独立的 FIFO 队列项，然后发布 `agent/queued`。agent loop（智能体循环）在每个轮次开始时最多取出一个普通队列项。如果两个普通队列项最终都进入轮次处理，第二个普通轮次只能在第一个普通轮次结束且其持久性检查点处理结束后开始；广义取消、dispose（资源释放）或启动前失败可以丢弃尚未启动的队列项，而不创建空轮次。
 
 提示词准入只处理一条消息。获准提示词成为该轮次的 `user/message`；被阻止提示词追加一条持久的 `prompt/blocked`，并让这个单消息轮次以 `rejected` 结束。实现中没有混合批次或全阻止批次分支。
 
@@ -22,11 +22,11 @@ Status: implemented
 
 ## 曾考虑的替代方案
 
-**为吞吐量保留普通 `send()` 的机会式批处理。** 当消息进入队列的速度超过驱动器的处理速度时，合并排队的普通提示词可以减少模型调用，但会让轮次边界取决于调度，并让后一条普通消息在前一个普通轮次关闭且其检查点处理结束之前就运行。额外模型调用的代价低于显式生命周期语义的价值；未来的任何普通 `send()` 批处理功能都必须提供调用方可见的显式契约，并由测量结果证明其必要性。
+**为吞吐量保留普通 send 的机会式批处理。** 当消息进入队列的速度超过驱动器的处理速度时，合并排队的普通提示词可以减少模型调用，但会让轮次边界取决于调度，并让后一条普通消息在前一个普通轮次关闭且其检查点处理结束之前就运行。额外模型调用的代价低于显式生命周期语义的价值；未来的任何普通 send 批处理功能都必须提供调用方可见的显式契约，并由测量结果证明其必要性。
 
 ## 验证
 
-- 单元与性质覆盖固定了同一调用栈、相邻微任务、不同来源和重入 `send()` 的行为：每个轮次只有一条消息，并按 FIFO 排序。
+- 单元与性质覆盖固定了同一调用栈、相邻微任务、不同来源和重入 send 的行为：每个轮次只有一条消息，并按 FIFO 排序。
 - 真实组合测试会通过 stdio 构建产物同时写入两行，并观察两个模型请求和两个轮次边界。
 - 延迟第一个普通轮次的持久化刷新可以证明下一个排队的普通轮次不能在检查点处理结束前开始，且其请求能看到前一条助手结果；刷新即使失败，下一个普通轮次也要等它结束后才会开始。
 - 提示词否决、监听器失败、广义取消、dispose 和 `turn/start` 提交前失败都会保持已记录轮次边界平衡，不会合并消息或让仍应处理的排队工作滞留。
@@ -34,6 +34,6 @@ Status: implemented
 
 ## 后果
 
-普通轮次边界是确定的；前一个已认领普通消息的轮次完成检查点处理后，被认领的 FIFO 后继项会观察该轮次在会话中已关闭的结果；检查点处理结束不表示失败的持久化刷新已经成功。多个排队项仍可在同一个全局 `running` 区间内执行，广义取消也可以丢弃整个未启动队尾，因此状态和静止性仍是面向整个 agent 的观察，而不是逐消息结果。
+普通轮次边界是确定的；FIFO 后继项进入轮次处理时，会观察前一个已完成普通轮次在会话中已关闭的结果；检查点处理结束不表示失败的持久化刷新已经成功。多个排队项仍可在同一个全局 `running` 区间内执行，广义取消也可以丢弃整个未启动队尾，因此状态和静止性仍是面向整个 agent 的观察，而不是逐消息结果。
 
-依赖普通 `send()` 偶然批处理的工作负载会产生更多模型请求和检查点，队列清空时间也可能延长；持续有消息进入时，FIFO 队列还可能增长。只有建立显式且经过测量的契约后，才能重新引入普通 `send()` 批处理。
+依赖普通 send 偶然批处理的工作负载会产生更多模型请求和检查点，队列清空时间也可能延长；持续有消息进入时，FIFO 队列还可能增长。只有建立显式且经过测量的契约后，才能重新引入普通 send 批处理。

packages/core/agent-loop/src/agent.ts

@@ -398,7 +398,7 @@ export class ReactLoopAgent implements Agent {
       cancelReason: () => this.cancelReason,
       clearCancel: () => { this.cancelRequested = false },
       withToolBatch: run => this.withToolBatch(run),
-      // Already-idle pre-start cancellation still must settle queued-work waiters.
+      // Pre-start cancellation settles queued-work waiters before publishing idle.
       settleIdle: () => { this.settleIdleWaiters() },
     }))
   }

packages/core/agent-loop/src/loop.ts

@@ -91,7 +91,7 @@ export interface LoopHandle {
   cancelReason(): string
   /** Clear the cancel marker (called once per iteration after the turn returns). */
   clearCancel(): void
-  /** Settle idle waiters when pre-running cancellation finds the status already idle. */
+  /** Settle idle waiters before pre-running cancellation publishes idle. */
   settleIdle(): void
   /** Run an active tool-call batch, accepting post-tool context into the FIFO drained before settlement. */
   readonly withToolBatch: <T>(run: (acceptContext: (context: HookContext) => void) => Promise<T>) => Promise<T>
@@ -118,6 +118,17 @@ export async function runLoop(ctx: Context, handle: LoopHandle): Promise<void> {
   const events = agentEvents(ctx, agent)
 
   while (!handle.isDisposed()) {
+    // An idle listener can enqueue and cancel replacement work before the next
+    // wait is installed. Consume that empty marker before parking the driver.
+    if (handle.isCancelled()) {
+      handle.clearCancel()
+      if (!handle.inbox.hasQueued) {
+        handle.settleIdle()
+        handle.setStatus('idle')
+        continue
+      }
+    }
+
     await handle.inbox.waitForQueued(handle.disposed)
     if (handle.isDisposed()) break
 
@@ -126,10 +137,10 @@ export async function runLoop(ctx: Context, handle: LoopHandle): Promise<void> {
     if (handle.isCancelled()) {
       handle.clearCancel()
       if (!handle.inbox.hasQueued) {
-        // setStatus settles running→idle; the explicit settle covers the
-        // already-idle pre-start path where that transition is deduplicated.
-        handle.setStatus('idle')
+        // Settle before publishing idle: the already-idle path has no status
+        // transition, while an idle listener can register waiters for new work.
         handle.settleIdle()
+        handle.setStatus('idle')
         continue
       }
     }

packages/core/agent-loop/tests/cancel.spec.ts

@@ -194,6 +194,82 @@ describe('Agent.cancel()', () => {
     expect(userTexts(agent)).toEqual(['first', 'idle steer'])
   })
 
+  it('an idle-listener replacement keeps whenIdle pending until the replacement turn finishes', async () => {
+    const adapter = new MockAdapter([textResponse('first reply'), textResponse('replacement reply')])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create(SessionId('between-turn-idle-listener'), { provider: 'mock', model: 'mock' })
+
+    let rejectFirstFlush = true
+    ctx.on('session/flush', (session) => {
+      if (session !== agent.session || !rejectFirstFlush) return
+      rejectFirstFlush = false
+      throw new Error('first flush failed')
+    })
+
+    ctx.on('agent/error', (subject, _turn, _step, error) => {
+      if (subject !== agent || error.message !== 'first flush failed') return
+      queueMicrotask(() => {
+        queueMicrotask(() => { agent.cancel('between turns') })
+      })
+    })
+
+    const replacementRegistered = Promise.withResolvers<undefined>()
+    let replacementObservation: Promise<{ status: string; requests: number; turns: number }> | undefined
+    ctx.on('agent/status', (subject, status) => {
+      if (subject !== agent || status !== 'idle' || replacementObservation !== undefined) return
+      send(agent, 'replacement')
+      replacementObservation = agent.whenIdle().then(() => ({
+        status: agent.status,
+        requests: adapter.requests.length,
+        turns: agent.session.events.filter(event => event.type === 'turn/start').length,
+      }))
+      replacementRegistered.resolve(undefined)
+    })
+
+    send(agent, 'first')
+    send(agent, 'cancelled tail')
+    await replacementRegistered.promise
+    if (replacementObservation === undefined) throw new Error('idle listener did not register replacement work')
+
+    await expect(replacementObservation).resolves.toEqual({ status: 'idle', requests: 2, turns: 2 })
+    expect(userTexts(agent)).toEqual(['first', 'replacement'])
+  })
+
+  it('idle-listener cancellation settles its waiter without cancelling later work', async () => {
+    const adapter = new MockAdapter([textResponse('first reply'), textResponse('later reply')])
+    const ctx = await harness(adapter)
+    const agent = ctx.agentLoop.create(SessionId('idle-listener-cancel'), { provider: 'mock', model: 'mock' })
+
+    const replacementRegistered = Promise.withResolvers<undefined>()
+    let replacementObservation: Promise<{ status: string; requests: number; turns: number }> | undefined
+    ctx.on('agent/status', (subject, status) => {
+      if (subject !== agent || status !== 'idle' || replacementObservation !== undefined) return
+      send(agent, 'cancelled replacement')
+      replacementObservation = agent.whenIdle().then(() => ({
+        status: agent.status,
+        requests: adapter.requests.length,
+        turns: agent.session.events.filter(event => event.type === 'turn/start').length,
+      }))
+      agent.cancel('idle listener')
+      replacementRegistered.resolve(undefined)
+    })
+
+    send(agent, 'first')
+    await replacementRegistered.promise
+    if (replacementObservation === undefined) throw new Error('idle listener did not register replacement work')
+
+    await expect(Promise.race([
+      replacementObservation,
+      new Promise((_resolve, reject) => setTimeout(() => { reject(new Error('whenIdle hung after idle-listener cancel')) }, 1000)),
+    ])).resolves.toEqual({ status: 'idle', requests: 1, turns: 1 })
+
+    const idle = waitForIdle(ctx, agent)
+    send(agent, 'later')
+    await idle
+    expect(adapter.requests).toHaveLength(2)
+    expect(userTexts(agent)).toEqual(['first', 'later'])
+  })
+
   it('cancel() mid-step aborts the active turn and drops every queued tail item', async () => {
     const adapter = new MockAdapter(['hang'])
     const ctx = await harness(adapter)

packages/core/agent-loop/tests/interception.spec.ts

@@ -241,7 +241,7 @@ describe('agent/prompt-submit', () => {
     send(agent, 'second')
     await idle
     expect(errors.map(e => e.message)).toEqual(['prompt hook broke'])
-    // The failed prompt owns one balanced error turn; the adjacent prompt owns
+    // The failed prompt forms one balanced error turn; the adjacent prompt forms
     // the following normal turn without an intermediate idle transition.
     const log = events(agent)
     expect(log.filter(e => e.type === 'turn/start')).toHaveLength(2)

packages/core/agent-loop/tests/properties.spec.ts

@@ -120,7 +120,7 @@ describe('agent loop scheduling properties', () => {
 
           // No message lost: every send appears as a user/message, in order.
           expect(userMessageTexts(agent)).toEqual(texts)
-          // This failure-free fixture claims every item into an independent turn.
+          // This failure-free fixture maps every item to an independent turn.
           expect(turnNumbers(agent)).toEqual(texts.map((_, i) => i + 1))
           expect(turnEndNumbers(agent)).toEqual(texts.map((_, i) => i + 1))
           expect(userMessageCountsByTurn(agent)).toEqual(texts.map(() => 1))
@@ -178,7 +178,7 @@ describe('agent loop scheduling properties', () => {
 
           // No message is lost or reordered, regardless of driver timing.
           expect(userMessageTexts(agent)).toEqual(steps.map(s => s.text))
-          // Every item is claimed and therefore owns one FIFO-ordered turn.
+          // Every item forms one FIFO-ordered turn containing only that message.
           const turns = turnNumbers(agent)
           expect(turns).toEqual(steps.map((_, i) => i + 1))
           expect(turnEndNumbers(agent)).toEqual(turns)