docs(agent-loop): correct the owning cancellation note

The 2026-07-16 explicit-turn-cancellation note still described a frozen,
detached signal reason and a two-variant cause union. The README paragraph
added here points readers at that note as the owner of the signal
lifecycle, so the stale mechanism was load-bearing.

It now records why freezing the caller's cause is not an alternative:
undici assigns `stack` from strict-mode code, so a frozen reason makes
fetch reject with `TypeError: Cannot add property stack` in place of the
abort reason.

Also names `turn/end`'s declared `TurnEndCancelCause` in the README and
takes the reviewer's helper-doc wording.

.agents/notes/implemented/architecture/2026-07-16-explicit-turn-cancellation.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 .agents/notes/implemented/architecture/2026-07-16-explicit-turn-cancellation.md
-2026-07-16-explicit-turn-cancellation.md: 09631349226837d7f93112fe5e9c517f2fee099c
-2026-07-16-explicit-turn-cancellation.zh.md: baf039d49578895d53ffae4c6b88d29b3d1563b6
+2026-07-16-explicit-turn-cancellation.md: d59accf2dc3f894ffab226e5ddc9d2e746f4d93e
+2026-07-16-explicit-turn-cancellation.zh.md: 8fb0728eb2bbe8fa01dbefebe7e02aa8c836617a

.agents/notes/implemented/architecture/2026-07-16-explicit-turn-cancellation.md

@@ -12,7 +12,7 @@ The [initiating Agent scope decision](2026-07-15-agent-initiator-scope.md) inten
 
 ## Decision
 
-Agent owns the runtime-only `AgentCancelCause` union `{ kind: 'user' } | { kind: 'parent' }`; `agent.cancel()` defaults to `user`. TypeScript enforces that vocabulary at this typed same-process boundary, with no runtime validator, fallback, or special compatibility contract for untyped callers. An active `TurnCancellation` copies the typed discriminant into a fresh frozen signal reason; idle cancellation has no holder to mutate and does not arm later work.
+Agent owns the runtime-only `AgentCancelCause` union `{ kind: 'user' } | { kind: 'parent' } | { kind: 'hook'; reason: string } | { kind: 'disposed' }`, and `agent.cancel()` requires one. TypeScript enforces that vocabulary at this typed same-process boundary, with no runtime validator, fallback, or special compatibility contract for untyped callers. The holder aborts with the caller's own object rather than a detached copy, so a transport reaching that signal can extend it: Node's fetch assigns a `stack` onto the reason it receives. The loop therefore copies the declared fields where the cause becomes durable data. Freezing the cause at `cancel()` is not an alternative — undici performs that assignment from strict-mode code, so a frozen reason makes `fetch` reject with `TypeError: Cannot add property stack` in place of the abort reason. Idle cancellation has no holder to mutate and does not arm later work.
 
 An interrupted live turn ends with the coarse durable `{ kind: 'aborted' }` outcome. The terminal event records what happened to the turn, while the runtime signal identifies who requested cancellation; it does not duplicate `user` or `parent` into replay. Session seed/load rejects legacy aborted records with a reason or any other extra field, so replay cannot reintroduce caller-owned cancellation detail. The process-local `agent/cancel-requested` notification is not durable; a future audit requirement uses a separate durable control-request event so a request and its eventual outcome remain distinct. Durable events contain no stack, signal, error object, free-form cancellation text, or backend-private detail.
 
@@ -22,7 +22,7 @@ The driver keeps only a cause-less pre-run marker for queued work cancelled befo
 
 The explicit event signatures pass a single payload object: agent-scoped events carry `agent` and `signal` in the payload with `next` last, and the remaining APIs keep `signal` immediately before a waterfall's final `next`. `PreStepContext` and `RequestFailureContext` are retired, with their fields folded into the `agent/pre-step` and `agent/request-error` payloads ([payload-object events](../../archived/architecture/2026-08-06-agent-event-payload-objects.md)). Pre-step entry, request configuration, request-error recovery, model generation, tool execution, approval, turn stopping, and subagent or workflow requests all receive the current signal. Hook bridges must also supply `RunHookOptions.signal`, so a turn cancellation reaches the bash executor's provider-managed termination and join boundary; the [native-containment decision](2026-08-28-subprocess-native-containment.md) owns the supported local scope, Job, and fallback mechanics. `SystemPrompt.assemble()` carries `signal?: AbortSignal` in `AssembleContext` because that object is an explicit request value that can also represent signal-less assembly outside a turn. Listeners may cooperate with the signal but must not retain it to control another turn.
 
-`ctx.agents` continues to carry only the initiating Agent. Ambient Agent presence does not imply liveness, a current turn, or cancellation authority. The cause reader is private to the loop and states the machine-private slot invariant (only `cancel()` aborts a turn controller, always with a canonical frozen cause) instead of re-validating the reason structurally; no public helper reads a cause off an arbitrary signal. Concurrent Agents isolate both their initiator identities and their turn signals; a child driver shadows the parent initiator while its parent request signal still travels through the subagent seam.
+`ctx.agents` continues to carry only the initiating Agent. Ambient Agent presence does not imply liveness, a current turn, or cancellation authority. The cause reader is private to the loop and states the machine-private slot invariant (only `cancel()` aborts a turn controller, always with a typed cause) instead of re-validating the reason structurally; no public helper reads a cause off an arbitrary signal. Concurrent Agents isolate both their initiator identities and their turn signals; a child driver shadows the parent initiator while its parent request signal still travels through the subagent seam.
 
 Agent disposal requests the runtime-only `{ kind: 'disposed' }` interruption on the active holder. If cancellation already won the controller reason, the reason cannot be rewritten, so terminal classification first checks lifecycle state: disposed wins, then a supported `user` or `parent` cause becomes the coarse aborted outcome, and unrelated exceptions retain the existing error path. ACP cancellation maps to `user`; in-process spawn and fork propagation map to `parent`. Remote ACP subagents retain their existing wire protocol.
 
@@ -30,7 +30,7 @@ Cancellation remains cooperative. The loop checks interruption before and after
 
 ## Verification
 
-Contract tests verify the typed caller union, frozen detachment, default and first-wins behavior, the coarse Session JSON round trip and legacy-record rejection, ACP `user`, in-process subagent `parent`, and disposal precedence. Loop tests make cooperative listeners wait on the signal at pre-step, system-prompt assembly, request, model stream, request-error recovery, tool execution, and turn stopping; they assert one signal within a turn, a fresh signal across turns, and no cancellation authority during terminal publication or a blocked durability flush. A real hook bridge test cancels and reaps a blocked prompt hook before idle.
+Contract tests verify the typed caller union, field copying where the cause becomes durable data, default and first-wins behavior, the coarse Session JSON round trip and legacy-record rejection, ACP `user`, in-process subagent `parent`, and disposal precedence. Loop tests make cooperative listeners wait on the signal at pre-step, system-prompt assembly, request, model stream, request-error recovery, tool execution, and turn stopping; they assert one signal within a turn, a fresh signal across turns, and no cancellation authority during terminal publication or a blocked durability flush. A real hook bridge test cancels and reaps a blocked prompt hook before idle.
 
 Initiator-scope tests assert that every hook still observes the exact Agent and no ambient turn signal, concurrent Agents retain independent identities and signals, and a nested child driver shadows only identity. Race tests cover idle cancellation, pre-run cancellation, replacement submission from a `running` listener, repeated cancellation, and cancel-versus-dispose quiescence.
 

.agents/notes/implemented/architecture/2026-07-16-explicit-turn-cancellation.zh.md

@@ -12,7 +12,7 @@ Status: implemented
 
 ## 决策
 
-Agent 拥有仅用于运行时的 `AgentCancelCause` 联合类型 `{ kind: 'user' } | { kind: 'parent' }`；`agent.cancel()` 默认使用 `user`。TypeScript 在这个类型化的同进程边界中强制执行该词汇，不提供运行时校验器、后备行为，也不为无类型调用方提供特殊兼容性约定。活跃的 `TurnCancellation` 会把类型化判别字段复制为一个全新且已冻结的 signal 原因；空闲状态下没有可修改的持有者，也不会让后续工作预先进入取消状态。
+Agent 拥有仅用于运行时的 `AgentCancelCause` 联合类型 `{ kind: 'user' } | { kind: 'parent' } | { kind: 'hook'; reason: string } | { kind: 'disposed' }`，`agent.cancel()` 必须显式传入其一。TypeScript 在这个类型化的同进程边界中强制执行该词汇，不提供运行时校验器、后备行为，也不为无类型调用方提供特殊兼容性约定。持有者中止时携带的是调用方自己的那个对象，而非一份分离的拷贝，因此能接触到该 signal 的传输层可以向其添加属性：Node 的 fetch 会给它收到的 reason 赋一个 `stack`。所以循环在 cause 成为持久数据的那一步拷贝已声明字段。在 `cancel()` 处冻结 cause 并非可选方案——undici 是在严格模式代码中执行该赋值的，被冻结的 reason 会让 `fetch` 以 `TypeError: Cannot add property stack` 取代中止原因而拒绝。空闲状态下没有可修改的持有者，也不会让后续工作预先进入取消状态。
 
 正在运行的轮次被中断后，以粗粒度的持久化结果 `{ kind: 'aborted' }` 结束。终态事件记录轮次发生了什么，运行时 signal 标识谁请求了取消；回放不会重复保存 `user` 或 `parent`。会话 seed/load 会拒绝携带取消原因或任何其他额外字段的旧式中止记录，因此回放无法重新引入由调用方持有的取消细节。仅限进程内的 `agent/cancel-requested` 通知不会持久化；未来若有审计需求，应使用独立的持久化控制请求事件，让请求与最终结果保持为两项事实。持久化事件不包含调用栈、signal、错误对象、自由文本取消原因或后端私有细节。
 
@@ -22,7 +22,7 @@ AgentLoop 为每个待启动轮次私有地持有一个 `TurnCancellation`。它
 
 显式事件签名传递单个 payload 对象：agent 作用域事件在 payload 中携带 `agent` 和 `signal`，`next` 位于最后；其余 API 保持 `signal` 紧邻 waterfall（瀑布式事件）的最终 `next` 之前。`PreStepContext` 与 `RequestFailureContext` 已退役，其字段并入 `agent/pre-step` 与 `agent/request-error` 的 payload（[payload-object 事件](../../archived/architecture/2026-08-06-agent-event-payload-objects.md)）。进入 pre-step 时、请求配置、请求错误恢复、模型生成、工具执行、审批、轮次停止以及 subagent 或工作流请求都会收到当前 signal。钩子桥接器也必须提供 `RunHookOptions.signal`，使轮次取消能够到达 Bash 执行器由提供方管理的终止与等待边界；[原生 containment 决策](2026-08-28-subprocess-native-containment.zh.md)负责受支持本地路径上的 scope、Job 与 fallback 机制。`SystemPrompt.assemble()` 在 `AssembleContext` 中携带 `signal?: AbortSignal`，因为该对象是显式请求值，也可表示轮次之外不携带 signal 的组装。监听器可以配合该 signal 取消，但不得保留它来控制其他轮次。
 
-`ctx.agents` 仍只携带发起 Agent。环境中的 Agent 并不代表存活、当前轮次或取消权限。cause 读取器是 loop 私有的，它直接陈述机器私有的 slot 不变量（只有 `cancel()` 会中止轮次控制器，且总是携带规范的冻结 cause），而不是对 reason 做结构化再校验；不存在从任意 signal 读取 cause 的公开辅助函数。并发 Agent 会同时隔离各自的发起方身份和轮次 signal；子驱动会遮蔽父发起方，而父请求 signal 仍通过 subagent seam 传递。
+`ctx.agents` 仍只携带发起 Agent。环境中的 Agent 并不代表存活、当前轮次或取消权限。cause 读取器是 loop 私有的，它直接陈述机器私有的 slot 不变量（只有 `cancel()` 会中止轮次控制器，且总是携带类型化的 cause），而不是对 reason 做结构化再校验；不存在从任意 signal 读取 cause 的公开辅助函数。并发 Agent 会同时隔离各自的发起方身份和轮次 signal；子驱动会遮蔽父发起方，而父请求 signal 仍通过 subagent seam 传递。
 
 Agent dispose（资源释放）会在活跃持有者上请求仅用于运行时的 `{ kind: 'disposed' }` 中断。若取消已经先占用控制器的中断原因，该原因便无法改写，因此终态分类会先检查生命周期状态：资源释放结果优先，之后受支持的 `user` 或 `parent` 取消原因形成粗粒度的中止结果，其他异常保留现有错误路径。ACP（Agent Client Protocol）取消映射为 `user`；进程内 spawn 和 fork 的传播映射为 `parent`。远程 ACP subagent 保持现有协议。
 
@@ -30,7 +30,7 @@ Agent dispose（资源释放）会在活跃持有者上请求仅用于运行时
 
 ## 验证
 
-约定测试验证类型化调用方联合类型、冻结且与调用方分离、默认行为与首次请求优先行为、粗粒度的会话 JSON 往返与旧式记录拒绝、ACP `user`、进程内 subagent `parent` 以及 dispose 优先级。AgentLoop 测试让协作式监听器在 pre-step、系统提示词组装、请求、模型流、请求错误恢复、工具执行和轮次停止处等待 signal；并断言同一轮次使用一个 signal，不同轮次使用全新的 signal，终态发布期间和持久化刷新受阻期间不存在取消权限。真实钩子桥接器测试会在报告空闲状态前取消并回收受阻的提示词钩子。
+约定测试验证类型化调用方联合类型、在 cause 成为持久数据处拷贝字段、默认行为与首次请求优先行为、粗粒度的会话 JSON 往返与旧式记录拒绝、ACP `user`、进程内 subagent `parent` 以及 dispose 优先级。AgentLoop 测试让协作式监听器在 pre-step、系统提示词组装、请求、模型流、请求错误恢复、工具执行和轮次停止处等待 signal；并断言同一轮次使用一个 signal，不同轮次使用全新的 signal，终态发布期间和持久化刷新受阻期间不存在取消权限。真实钩子桥接器测试会在报告空闲状态前取消并回收受阻的提示词钩子。
 
 发起方作用域测试断言所有钩子仍观察到同一个 Agent 且没有环境中的轮次 signal，并发 Agent 保持独立的身份与 signal，嵌套子驱动只遮蔽身份。竞态测试覆盖空闲状态取消、运行前取消、从 `running` 监听器提交替代提示词、重复取消以及取消与 dispose 竞争下的完全停稳。
 

packages/core/agent-loop/README.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 packages/core/agent-loop/README.md
-README.md: bfe7944c75f7cab7565f966863f7d7118c61ed97
-README.zh.md: d44f6cd16e728491d97a3e00085f0225d52c5cdf
+README.md: f74182e468c8c844be71f762c6f0dd266cf799f3
+README.zh.md: e55d481dc61ae52b7d08ff09ffb0595ce085fd76

packages/core/agent-loop/README.md

@@ -122,7 +122,7 @@ Prompt admission uses the actual `prepareCall()` result, not the preceding `requ
 
 ### Failure and cancellation
 
-Cancellation records a fresh `AgentCancelCause` in `turn/end`, retaining the caller's `kind` and the hook's `reason` text. The live `AbortSignal.reason` remains the caller's object, which a transport may extend — Node's fetch assigns a `stack` onto it — so the copy keeps that trace out of the log and keeps the ending appendable.
+`turn/end` declares `TurnEndCancelCause`; cancellation records a fresh `AgentCancelCause` there, retaining the caller's `kind` and the hook's `reason` text. The live `AbortSignal.reason` remains the caller's object, which a transport may extend — Node's fetch assigns a `stack` onto it — so the copy keeps that trace out of the log and keeps the ending appendable.
 
 Final adapter selection, dispatch, and iteration failures arrive as terminal finishes and enter `agent/request-error`; a handling listener returns `{ kind: 'retry' }` without calling `next()`, while an unhandled failure is terminal. Middleware, result-processing, tool, and other extension failures remain thrown and close the turn directly — plugin failure ends the turn, not the loop. Undispatched model tool calls after cancellation receive synthetic `tool/call` plus `ABORTED_BEFORE_DISPATCH` result pairs. The [explicit-cancellation decision](../../../.agents/notes/implemented/architecture/2026-07-16-explicit-turn-cancellation.md) owns the signal lifecycle.
 

packages/core/agent-loop/README.zh.md

@@ -122,7 +122,7 @@ const handle = await ctx.agents.create({
 
 ### 失败与取消
 
-取消时，循环在 `turn/end` 中记录一份新的 `AgentCancelCause`，保留调用方的 `kind` 和 hook 的 `reason` 文本。实时 `AbortSignal.reason` 仍是调用方的那个对象，传输层可能向其添加属性——Node 的 fetch 会给它赋一个 `stack`——因此这份拷贝既让该调用栈不进入日志，也让结束事件保持可追加。
+`turn/end` 声明的类型是 `TurnEndCancelCause`；取消时，循环在其中记录一份新的 `AgentCancelCause`，保留调用方的 `kind` 和 hook 的 `reason` 文本。实时 `AbortSignal.reason` 仍是调用方的那个对象，传输层可能向其添加属性——Node 的 fetch 会给它赋一个 `stack`——因此这份拷贝既让该调用栈不进入日志，也让结束事件保持可追加。
 
 最终适配器选择、分发与迭代失败以终止结束的形式到达并进入 `agent/request-error`；处理该失败的监听器返回 `{ kind: 'retry' }` 且不调用 `next()`，未被处理的失败则是终态。Middleware、结果处理、工具及其他扩展失败仍会抛出并直接关闭轮次——插件失败结束的是轮次，不是循环。取消后未分发的模型工具调用会收到合成的 `tool/call` 加 `ABORTED_BEFORE_DISPATCH` 结果对。[显式取消决策](../../../.agents/notes/implemented/architecture/2026-07-16-explicit-turn-cancellation.zh.md)拥有信号生命周期。
 

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

@@ -69,10 +69,10 @@ function requestProposal(header: EpochHeader): LlmCallConfig {
 }
 
 /**
- * Read the cause {@link ReactLoopAgent.cancel} aborted a loop-owned signal
- * with, copying the fields `turn/end` records. The live reason stays the
- * caller's object, and Node's fetch assigns a `stack` onto it that
- * `Session.append` would either log or reject as data JSON cannot hold.
+ * Read the cause `cancel()` passed when aborting a loop-owned signal, copying
+ * only the fields `turn/end` records. The live reason stays the caller's
+ * object, and Node's fetch assigns a `stack` onto it that `Session.append`
+ * would either log or reject as data JSON cannot hold.
  * @param signal - a turn or maintenance signal this loop owns.
  * @returns the copied cause, or undefined while the signal is still live.
  */