refactor: remove per-followup result attribution

packages/subagent/subagent-dsh-sdk/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/subagent/subagent-dsh-sdk/README.md
-README.md: e904ce3c09a1b44f8f5a0072b9ca85812898e74f
-README.zh.md: cec89ad9a65c68163fc136fe7b04cb135c57fb51
+README.md: 834c967354610e9ecbb76380f8ddbce988b51c8c
+README.zh.md: 4af03a6647da38adf8283d567b37a10203ad7c90

packages/subagent/subagent-dsh-sdk/README.md

@@ -10,13 +10,13 @@ The SDK provider runs each subagent as a complete DeepSeek Harness runtime in a
 
 The working directory resolves exactly like the ACP backend, through the seam's shared out-of-process helpers ([`dsh-subagent`](../subagent/README.md)): the configured `cwd` override when set (validated once at load), else the delegating parent session's cwd — never the server process's own cwd. The resolved path becomes the child process cwd and the workspace cwd of its SDK session.
 
-The returned run id is minted in the parent namespace; the child runtime's session id exists only inside the child process. After publication the provider runs one SDK turn and reads the child's answer from its session events: the last complete `assistant/message`, or the `text-delta` stream accumulated so far when the turn was cut short — a partial answer survives cancel and error paths.
+The returned run id is minted in the parent namespace; the child runtime's session id exists only inside the child process. After publication the provider owns one SDK activity and reads the child's answer from its session events: the last complete `assistant/message`, or the `text-delta` stream accumulated before the activity was cut short — a partial answer survives cancel and error paths.
 
 `dispose()` is idempotent: it settles the result locally as `aborted` (there is no wire-level prompt cancel), then closes the runtime — a bounded protocol `shutdown` request followed by the shared stdin-EOF → SIGTERM → SIGKILL ladder to actual exit.
 
 ## Stop-reason mapping
 
-The child reports its turn outcome as a structured `TurnEndReason` on `session.finished`; the provider maps it into the seam vocabulary. `completed` → `completed`, `max-tokens` → `max-tokens`, `aborted` → `aborted`; everything else — `error`, `interrupted`, `disposed`, a future variant, or a turn that never ran — maps to `error`, so an unclean stop is never reported as success. Transport-level failures after publication flatten to `stopReason: 'error'` through the `onError` diagnostic sink (wired to `ctx.logger.warn`); the seam contract forbids `result` rejecting.
+The SDK client returns an owned child activity rather than a prompt result. The provider reads the last durable `turn/end` inside that activity and maps it into the seam vocabulary: `completed` → `completed`, `max-tokens` → `max-tokens`, `aborted` → `aborted`; everything else — `error`, `interrupted`, `disposed`, a future variant, or an activity with no turn — maps to `error`, so an unclean stop is never reported as success. Transport-level failures after publication flatten to `stopReason: 'error'` through the `onError` diagnostic sink (wired to `ctx.logger.warn`); the seam contract forbids `result` rejecting.
 
 ## Capabilities and context
 

packages/subagent/subagent-dsh-sdk/README.zh.md

@@ -10,13 +10,13 @@ SDK 提供方会在全新的子进程中把每个 subagent 作为完整的 DeepS
 
 工作目录的解析与 ACP 后端完全一致，并使用 seam 共享的进程外辅助工具（[`dsh-subagent`](../subagent/README.md)）：设置了 `cwd` 覆盖值时使用该值（加载时校验一次），否则使用发起委派的父会话 cwd，绝不使用服务器进程自身的 cwd。解析出的路径同时成为子进程 cwd 和其 SDK 会话的工作区 cwd。
 
-返回的 run id 在父级命名空间中生成；子运行时的会话 id 只存在于子进程内部。发布后，提供方运行一个 SDK 轮次，并从子会话事件中读取答案：最后一条完整的 `assistant/message`，或轮次被截断时已累积的 `text-delta` 流；部分答案在取消和错误路径上都得以保留。
+返回的 run id 在父级命名空间中生成；子运行时的会话 id 只存在于子进程内部。发布后，提供方拥有一段 SDK 活动，并从子会话事件中读取答案：最后一条完整的 `assistant/message`，或该活动中断前已经累积的 `text-delta` 流；部分答案在取消和错误路径上都得以保留。
 
 `dispose()`（资源释放）是幂等的：先在本地把结果确定为 `aborted`（协议层面没有提示词取消机制），再关闭运行时，即先发出一次有界的协议 `shutdown` 请求，随后通过共享的 stdin-EOF → SIGTERM → SIGKILL 阶梯使进程实际退出。
 
 ## 停止原因映射
 
-子进程在 `session.finished` 上以结构化 `TurnEndReason` 报告轮次结果；提供方将其映射为 seam 词汇。`completed` → `completed`，`max-tokens` → `max-tokens`，`aborted` → `aborted`；其余情况，包括 `error`、`interrupted`、`disposed`、未来变体或根本未运行轮次，均映射为 `error`，因此非正常停止绝不会报告为成功。发布后的传输层失败会通过 `onError` 诊断接收器（连接到 `ctx.logger.warn`）压平为 `stopReason: 'error'`；seam 契约禁止 `result` 被拒绝。
+SDK 客户端返回自有子活动，而不是提示词结果。提供方读取该活动内最后一个持久 `turn/end`，并将其映射为 seam 词汇：`completed` → `completed`，`max-tokens` → `max-tokens`，`aborted` → `aborted`；其余情况，包括 `error`、`interrupted`、`disposed`、未来变体或不含轮次的活动，均映射为 `error`，因此非正常停止绝不会报告为成功。发布后的传输层失败会通过 `onError` 诊断接收器（连接到 `ctx.logger.warn`）压平为 `stopReason: 'error'`；seam 契约禁止 `result` 被拒绝。
 
 ## 能力与上下文
 

packages/subagent/subagent-dsh-sdk/src/run.ts

@@ -70,8 +70,8 @@ export const DEFAULT_SHUTDOWN_TIMEOUT_MS = 1_000
 
 /**
  * Map a child turn-end reason to a harness {@link SubagentStopReason}.
- * @param reason - the `session.finished` reason, or `undefined` when the
- * child settled without running a turn.
+ * @param reason - the owned child run's final durable turn reason, or
+ * `undefined` when it settled without running a turn.
  * @returns the harness equivalent; an absent or unknown reason maps to
  * `error`, so an unclean stop is never reported as `completed`.
  */
@@ -191,7 +191,10 @@ export async function startSdkRun(request: SubagentStartRequest, spec: SdkRunSpe
         cancelSettled.then(() => 'cancelled' as const),
       ])
       if (turn === 'cancelled') return { output: collectOutput(), stopReason: 'aborted' }
-      return { output: collectOutput(), stopReason: sdkStopReason(turn.reason) }
+      const lastEnd = turn.events.findLast(
+        (event): event is Extract<SessionEvent, { type: 'turn/end' }> => event.type === 'turn/end',
+      )
+      return { output: collectOutput(), stopReason: sdkStopReason(lastEnd?.data.reason) }
     },
     collectOutput,
     cancelled: () => flags.cancelled,

packages/subagent/subagent-inprocess/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/subagent/subagent-inprocess/README.md
-README.md: 980bc18de088c41dfe2f57a5ff0882a60892fc9f
-README.zh.md: 1ceb628371c3ae9cee6d8afa6bc1d95ba4cda8ae
+README.md: 67f0cf5dd1ecb18542af56953a0eaa40988aca0d
+README.zh.md: 58998ce06cd724d6a1f96f08ba31c5da30007b1b

packages/subagent/subagent-inprocess/README.md

@@ -14,10 +14,12 @@ The driver follows this sequence:
 2. Call `parent.ctx.agents.create` directly, passing the required request signal into the factory's creation transaction.
 3. During that transaction's unpublished setup window, install the requested persona, tool restriction, and structured-output runtime.
 4. Publish the child, retain the returned `AgentHandle`, and drive one task with `child.followup(prompt)` followed by `child.whenIdle()`.
-5. Read the child's own last assistant message and latest message-triggered turn reason, excluding any fork seed and later between-turn records.
+5. Read the child's own last assistant message and final durable turn reason from the complete owned child run, excluding any fork seed.
 
 The child gets the parent's working-directory/session lineage and inherits the parent provider, model, and output-token cap unless `request.agentOptions` overrides them. It gets a fresh flat registration scope: parent ownership does not import parent tool restrictions or establish an authority subset.
 
+This result boundary is valid because the provider owns an isolated child lifecycle from publication through quiescence. Steering submitted during that lifecycle belongs to the child run; the provider does not pretend the initial follow-up alone owns its output.
+
 When the optional sandbox-policy or approval service is composed, the driver snapshots the parent's explicit session override before child creation and appends a source-tagged event during unpublished setup, after any fork history and before session publication. It never copies deployment defaults or one-shot grants; later child switches still win. See the [policy-inheritance decision](../../../.agents/notes/implemented/feature/2026-07-25-subagent-policy-inheritance.md).
 
 ## Cancellation and ownership

packages/subagent/subagent-inprocess/README.zh.md

@@ -14,10 +14,12 @@
 2. 直接调用 `parent.ctx.agents.create`，把必需的请求信号传入工厂的创建事务。
 3. 在该事务未发布的设置窗口中，安装请求的 persona、工具限制和结构化输出运行时。
 4. 发布子 agent，保留返回的 `AgentHandle`，并通过先调用 `child.followup(prompt)`、再调用 `child.whenIdle()` 来驱动一项任务。
-5. 读取子 agent 自身最后一条 assistant 消息，以及由消息触发的最新轮次原因；排除任何 fork 初始内容和后续轮次间记录。
+5. 从完整的自有子运行中读取子 agent 自身最后一条 assistant 消息和最终持久轮次原因，并排除任何 fork 初始内容。
 
 子 agent 会获得父 agent 的工作目录／会话谱系；除非 `request.agentOptions` 覆盖，否则还会继承父 agent 的提供方、模型和输出 token 上限。它获得全新的扁平注册作用域：父级所有权不会导入父 agent 的工具限制，也不会建立权限子集。
 
+该结果边界成立，是因为提供方拥有从发布到完全停稳的隔离子 agent 生命周期。在该生命周期内提交的 steering（中途引导）属于子运行；提供方不会声称输出只归初始 follow-up 所有。
+
 当组合中挂载了可选的沙箱策略或审批服务时，驱动器会在创建子 agent 前对父级的显式会话覆盖项获取快照，并在未发布的设置阶段追加一条带来源标记的事件，使其位于所有 fork 历史之后、会话发布之前。它绝不复制部署默认值或一次性授权；子 agent 后续的切换仍然优先。参见[策略继承决策](../../../.agents/notes/implemented/feature/2026-07-25-subagent-policy-inheritance.md)。
 
 ## 取消与所有权