fix(subagent): persist descriptor before admission

.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.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/feature/2026-07-21-continuable-background-subagents.md
-2026-07-21-continuable-background-subagents.md: fc1cd97dae2583f6d78ee1413561002b6391a0c9
-2026-07-21-continuable-background-subagents.zh.md: 31775d9c2b8bd6b2dc84b5e86d4dbc9d1bd8a1f5
+2026-07-21-continuable-background-subagents.md: 5bbc5fb0b605771b0e7c292412d13ec6e56571ba
+2026-07-21-continuable-background-subagents.zh.md: 1864f6d47fe95d9771bb73da72caee6bb415ce0f

.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.md

@@ -71,7 +71,7 @@ Human input uses the same control operation. The UI may display the child transc
 
 ### Durable child handle and cold resume
 
-The control service snapshots every descriptor input with the seam's `snapshotSubagentDescriptor()` (built on [`snapshotJsonValue`](../../../../packages/core/session/src/json.ts)) before Task creation, matching the detached lossless-JSON boundary already used by Agent messages. A child-scoped setup contribution — a one-shot `agent/pre-step` listener installed by the in-process driver — appends one model-hidden `subagent/descriptor` event after the initial child `turn/start` and before its first request; it carries no `surfaceOp`, remains outside model history, and reaches persistence with that turn's flush. The append-only log retains this non-surface event when compaction replaces surface history. A known child id is resumable only when loading that child session yields a supported descriptor in the child's own suffix (after `seedLength`, so a fork seed cannot leak an ancestor's descriptor) and its header identifies the caller as the direct parent.
+The control service snapshots every descriptor input with the seam's `snapshotSubagentDescriptor()` (built on [`snapshotJsonValue`](../../../../packages/core/session/src/json.ts)) before Task creation, matching the detached lossless-JSON boundary already used by Agent messages. A child-scoped setup contribution — a prepended one-shot `agent/prompt-submit` listener installed by the in-process driver — appends one model-hidden `subagent/descriptor` event before downstream prompt admission can block or throw. Allowed admission opens the initial child turn afterward; rejected admission leaves the descriptor as a pre-turn log-only fact, and the activation's final required checkpoint persists it. The event carries no `surfaceOp`, remains outside model history, and survives when compaction replaces surface history. A known child id is resumable only when loading that child session yields a supported descriptor in the child's own suffix (after `seedLength`, so a fork seed cannot leak an ancestor's descriptor) and its header identifies the caller as the direct parent.
 
 The versioned descriptor (`SUBAGENT_DESCRIPTOR_VERSION` in [descriptor.ts](../../../../packages/subagent/subagent/src/descriptor.ts)) contains the subagent provider name, resolved child `agentOptions.provider` and `agentOptions.model`, and optional `persona` and `toolFilter`. It does not snapshot the merge-extensible `AgentOptions` object: unrelated extension values cannot make continuation fail merely because they are not JSON. It deliberately omits `subagentDepth`; cold resume relies on the persisted header's `delegationDepth` rather than reconstructing depth from the descriptor. `outputSchema` belongs to one activation's result contract rather than durable child composition. The child header remains authoritative for the child id, `cwd`, `parentSession`, `seedLength`, and `delegationDepth`, while the persisted child transcript owns the fork seed and subsequent history. [`delegationDepthOf()`](../../../../packages/subagent/subagent/src/index.ts) takes the maximum of header and runtime values, so reconstructed runtime options may deepen the persisted value but never lower it and a resumed child cannot regain a top-level delegation budget.
 
@@ -109,7 +109,7 @@ Task records and active-run associations are process-local. Persistence makes th
 
 ## Testing
 
-- `packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts` pins the continuable durability boundary: an absent or detached flush listener and a permanent listener failure reject with `DURABILITY_FAILED`, a transient loop-checkpoint failure can succeed on the final confirmation, cancellation owns either final-checkpoint outcome, resume also confirms durability, and foreground runs remain best-effort. `packages/subagent/subagent/tests/continuation.spec.ts` drives the real stack (agent loop, JSONL persistence, spawn/fork providers, Task service, and `ctx.subagents`) keylessly: initial and resumed activations create fresh Tasks and dispose their runs before terminal; the descriptor event is turn-enclosed, model-hidden, versioned, and durable under the service-allocated child id; cancellation, steering, cold follow-up, authorization, ownership conflicts, and resume races retain the contracts described above.
+- `packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts` pins the continuable durability boundary: an absent or detached flush listener and a permanent listener failure reject with `DURABILITY_FAILED`, a transient loop-checkpoint failure can succeed on the final confirmation, cancellation owns either final-checkpoint outcome, resume also confirms durability, and foreground runs remain best-effort. `packages/subagent/subagent/tests/continuation.spec.ts` drives the real stack (agent loop, JSONL persistence, spawn/fork providers, Task service, and `ctx.subagents`) keylessly: initial and resumed activations create fresh Tasks and dispose their runs before terminal; the descriptor event is pre-turn, model-hidden, versioned, durable under the service-allocated child id, and survives blocked or throwing initial prompt admission; cancellation, steering, cold follow-up, authorization, ownership conflicts, and resume races retain the contracts described above.
 - `packages/subagent/tool-subagent-control/tests/tool-subagent-control.spec.ts` pins the `send_message` schema, coordinator attribution, both route renderings, the not-delivered failure, the no-agent rejection, and HMR disposal.
 - `packages/subagent/tool-subagent/tests/tool-subagent.spec.ts` covers the configured background route: continuable mode requires a resumable provider and returns both ids without requiring `send_message`, while one-shot mode keeps the plain Task acknowledgement even when the provider can resume.
 - `packages/sdk/helper/tests/project.spec.ts` pins the Task service and model-facing Task controls in generated spawn and fork compositions.

.agents/notes/implemented/feature/2026-07-21-continuable-background-subagents.zh.md

@@ -71,7 +71,7 @@ durable child Session
 
 ### 持久化 child handle 与从持久化存储恢复
 
-控制服务在创建 Task 前，通过 seam 的 `snapshotSubagentDescriptor()`（基于 [`snapshotJsonValue`](../../../../packages/core/session/src/json.ts) 构建）对每项描述符输入建立快照；这一边界与 Agent 消息现有的分离式无损 JSON 边界一致。作用于 child 作用域的 setup contribution——由进程内驱动安装的一次性 `agent/pre-step` 监听器——会在 child 初始 `turn/start` 之后、首次请求之前追加一个对模型隐藏的 `subagent/descriptor` 事件。该事件不携带 `surfaceOp`，不进入模型历史，并随该轮次的 flush 一并进入持久化存储。当压缩替换 surface 历史时，仅追加日志仍保留这个不属于 surface 的事件。只有在加载已知 child id 对应的 child 会话后，能在该 child 自身的后缀中（`seedLength` 之后，因此 fork seed 不会泄露祖先的描述符）得到受支持的描述符，且会话 header 将调用方标识为直接 parent 时，该 id 才可恢复。
+控制服务在创建 Task 前，通过 seam 的 `snapshotSubagentDescriptor()`（基于 [`snapshotJsonValue`](../../../../packages/core/session/src/json.ts) 构建）对每项描述符输入建立快照；这一边界与 Agent 消息现有的分离式无损 JSON 边界一致。作用于 child 作用域的 setup contribution——由进程内驱动前置安装的一次性 `agent/prompt-submit` 监听器——会在下游 prompt admission 能够阻止请求或抛出异常之前追加一个对模型隐藏的 `subagent/descriptor` 事件。admission 获准后才会开启 child 的初始轮次；admission 被拒绝时，描述符会作为轮次前的仅日志事实保留，并由该 activation 最终的必需检查点持久化。该事件不携带 `surfaceOp`，不进入模型历史，并在压缩替换 surface 历史时继续保留。只有在加载已知 child id 对应的 child 会话后，能在该 child 自身的后缀中（`seedLength` 之后，因此 fork seed 不会泄露祖先的描述符）得到受支持的描述符，且会话 header 将调用方标识为直接 parent 时，该 id 才可恢复。
 
 版本化描述符（[descriptor.ts](../../../../packages/subagent/subagent/src/descriptor.ts) 中的 `SUBAGENT_DESCRIPTOR_VERSION`）包含 subagent 提供方名称、已解析的 child `agentOptions.provider` 和 `agentOptions.model`，以及可选的 `persona` 与 `toolFilter`。它不会对可通过声明合并扩展的 `AgentOptions` 对象建立快照：与此无关的扩展值不会仅因无法表示为 JSON 而导致继续执行失败。描述符会特意省略 `subagentDepth`；从持久化存储恢复时，系统依赖持久化 header 中的 `delegationDepth`，而不根据描述符重建深度。`outputSchema` 属于单次激活的结果契约，不属于持久化 child 组合配置。child header 仍是 child id、`cwd`、`parentSession`、`seedLength` 和 `delegationDepth` 的权威信息，持久化 child transcript 则负责保存 fork seed 和后续历史。[`delegationDepthOf()`](../../../../packages/subagent/subagent/src/index.ts) 会在 header 值和运行时值中取最大值，因此重建后的运行时选项可以加深持久化值，但绝不能降低它，恢复后的 child 无法重新获得顶层委派预算。
 
@@ -109,7 +109,7 @@ Task 记录和活跃 run 关联都位于进程内。持久化使 child 会话可
 
 ## 测试
 
-- `packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts` 固定可继续执行的持久性边界：缺少 flush 监听器、flush 监听器已脱离或监听器持续失败时，均会以 `DURABILITY_FAILED` 拒绝；循环检查点的瞬时失败可在最终确认成功后继续完成，发生取消时最终检查点无论成功还是失败都由取消优先决定结果，resume 同样会确认持久性，而前台运行仍采用尽力而为策略。`packages/subagent/subagent/tests/continuation.spec.ts` 以无密钥方式驱动真实栈（agent loop、JSONL 持久化、spawn／fork 提供方、Task 服务和 `ctx.subagents`）：初始及恢复后的激活都会创建新 Task，并在进入终态前 dispose 各自的 run；描述符事件位于轮次内、对模型隐藏、带版本，并在服务分配的 child id 下持久化；取消、steering、cold follow-up、授权、所有权冲突与 resume 竞态保留上述契约。
+- `packages/subagent/subagent-inprocess/tests/subagent-inprocess.spec.ts` 固定可继续执行的持久性边界：缺少 flush 监听器、flush 监听器已脱离或监听器持续失败时，均会以 `DURABILITY_FAILED` 拒绝；循环检查点的瞬时失败可在最终确认成功后继续完成，发生取消时最终检查点无论成功还是失败都由取消优先决定结果，resume 同样会确认持久性，而前台运行仍采用尽力而为策略。`packages/subagent/subagent/tests/continuation.spec.ts` 以无密钥方式驱动真实栈（agent loop、JSONL 持久化、spawn／fork 提供方、Task 服务和 `ctx.subagents`）：初始及恢复后的激活都会创建新 Task，并在进入终态前 dispose 各自的 run；描述符事件位于轮次前、对模型隐藏、带版本、在服务分配的 child id 下持久化，并在初始 prompt admission 阻止请求或抛出异常时仍保留；取消、steering、cold follow-up、授权、所有权冲突与 resume 竞态保留上述契约。
 - `packages/subagent/tool-subagent-control/tests/tool-subagent-control.spec.ts` 固定 `send_message` 的 schema、coordinator 来源标记、两种路由渲染、未送达失败、无 agent 时的拒绝，以及 HMR（热模块替换）dispose。
 - `packages/subagent/tool-subagent/tests/tool-subagent.spec.ts` 覆盖配置的后台路由：可继续模式要求提供方可恢复，并在不要求 `send_message` 的情况下返回两个 id；即使提供方可以恢复，一次性模式仍保持普通的 Task 确认消息。
 - `packages/sdk/helper/tests/project.spec.ts` 固定生成的 spawn 与 fork 组合中的 Task 服务及面向模型的 Task 控制工具。