refactor agent pre-step inbox lifecycle

packages/core/session/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/session/README.md
-README.md: d2eb35108b7eba9963e62a1c0d2a8868c7b7a821
-README.zh.md: 85507abf55e82485268055f99f759b75f8cc5f01
+README.md: 2928cd22d7ecafdca951c3b9aca1fb0bdc2567dd
+README.zh.md: 209219e98b7dab7f3f142ccb0069f5a7eb654124

packages/core/session/README.md

@@ -65,7 +65,7 @@ Providers stream token-sized deltas, so a raw log stores hundreds of `assistant/
 
 `request/header` records a full canonical snapshot of the non-history request envelope with reason `initial`, `resume`, or `change`. Its optional `adapterDefaults` map marks effective `reasoningEffort` or `maxTokens` values materialized by exact-model resolution, allowing the next request proposal to distinguish them from explicit conversation settings. `foldRequestHeader()` selects the latest snapshot; legacy delta events and the removed `fallback` reason are rejected. See the [reconstructable-requests Agent Note](../../../.agents/notes/implemented/architecture/2026-07-05-reconstructable-requests.md).
 
-A `user/message` stores the complete `UserMessage` directly, including the identity created before routing or prompt admission. It renders its `content` verbatim whether it is a direct human prompt, a synthetic injection, or an admitted goal round; its typed `source` is the only channel that tells them apart and carries any domain-specific durable facts. `assistant/message`, `tool/result`, and `steering/message` likewise store complete message values. Turn execution remains enclosed by `turn/start` and `turn/end`, while an idle injection may append and flush a `user/message` between turns without running the model.
+A `user/message` stores the complete `UserMessage` directly, including the identity created before inbox routing or step entry. It renders its `content` verbatim whether it is a direct human prompt, a synthetic injection, or an entered goal round; its typed `source` is the only channel that tells them apart and carries any domain-specific durable facts. `assistant/message`, `tool/result`, and `steering/message` likewise store complete message values. Turn execution remains enclosed by `turn/start` and `turn/end`; `agent.inject()` queues input until a later pre-step claims it and returns it in an enter decision.
 
 `tool/result` persists one identified user-role tool-result message, optional internal failure identity, and optional presentation metadata. A tool's successful canonical `value` and human-readable canonical failure message remain execution-local; rendered error content is the replay-authoritative message.
 
@@ -75,7 +75,7 @@ The append-only log's event types, enumerated member by member — payloads, sur
 
 Merge-extensible via `SessionEventMap` — a plugin declaration-merges its own types (the compaction seam's `compact/*`, bounded recovery's non-surface `llm/retry`, the hook bridges' `hook/*`); merged members appear in the same catalog. A plugin owns the relational invariant for its merged events, including whether a log-only event may appear between turns. A producer that requires durability appends through `Session` and then awaits `ctx.sessions.flush(session)` without fabricating an execution turn.
 
-Also defines `TurnEndReasonMap`, the merge-extensible `kind`-tagged sum type for turn endings. `turn/start` carries only the turn number; the following admitted `user/message` batch records its input, while `llm/retry` records request recovery.
+Also defines `TurnEndReasonMap`, the merge-extensible `kind`-tagged sum type for turn endings. `turn/start` carries only the turn number; the following entered `user/message` batch records its input, while `llm/retry` records request recovery.
 
 An interrupted live turn ends with `{ kind: 'aborted', reason: AgentCancelCause }`, preserving the typed cancellation cause in the durable transcript. A turn failure carries `{ kind: 'error', error }`; crash recovery alone synthesizes `{ kind: 'interrupted' }`.
 

packages/core/session/README.zh.md

@@ -65,7 +65,7 @@
 
 `request/header` 记录非历史请求封装的完整规范快照，其原因为 `initial`、`resume` 或 `change`。其可选 `adapterDefaults` 映射会标记由精确模型解析填入的生效 `reasoningEffort` 或 `maxTokens` 值，使下一次请求提议能够将它们与显式对话设置区分开。`foldRequestHeader()` 选择最新快照；旧版增量事件和已移除的 `fallback` 原因会被拒绝。详见[可重建请求 Agent Note](../../../.agents/notes/implemented/architecture/2026-07-05-reconstructable-requests.md)。
 
-`user/message` 会直接存储完整的 `UserMessage`，其中包括路由或提示词准入前创建的标识。无论它是直接人类提示词、合成注入，还是已准入的 Goal Round，都会原样呈现其 `content`；带类型的 `source` 是区分三者的唯一通道，并携带各领域专有的持久事实。`assistant/message`、`tool/result` 和 steering（中途引导）对应的 `steering/message` 也会存储完整的消息值。轮次执行仍由 `turn/start` 与 `turn/end` 包围，而空闲注入可以在轮次之间追加并刷新一条 `user/message`，无需运行模型。
+`user/message` 会直接存储完整的 `UserMessage`，其中包括路由或 pre-step 领取前创建的标识。无论它是直接人类提示词、合成注入，还是进入步骤的 Goal Round，都会原样呈现其 `content`；带类型的 `source` 是区分三者的唯一通道，并携带各领域专有的持久事实。`assistant/message`、`tool/result` 和 steering（中途引导）对应的 `steering/message` 也会存储完整的消息值。轮次执行仍由 `turn/start` 与 `turn/end` 包围；`agent.inject()` 会把输入排队，直到某次 pre-step 返回 enter 并在轮次内记录它。
 
 `tool/result` 持久保存一条带标识、user-role 的工具结果消息，以及可选内部失败标识和可选呈现元数据。工具成功时的规范 `value` 和便于人类阅读的规范失败消息只存在于执行本地；渲染后的错误内容是回放权威消息。
 
@@ -75,7 +75,7 @@
 
 `SessionEventMap` 可通过合并扩展：插件使用声明合并添加自身类型（压缩 seam 的 `compact/*`、有界恢复的非 surface `llm/retry`、hook（钩子）桥接层的 `hook/*`）；合并成员会出现在同一目录中。插件拥有其合并事件的关系不变量，包括是否允许纯日志事件出现在轮次之间。需要持久性的生产方通过 `Session` 追加，再等待 `ctx.sessions.flush(session)`，无需虚构一个执行轮次。
 
-此包还定义 `TurnEndReasonMap`，即用于轮次结束、可合并扩展且以 `kind` 为标签的和类型。`turn/start` 只携带轮次编号；之后已准入的 `user/message` 批次记录其输入，`llm/retry` 则记录请求恢复。
+此包还定义 `TurnEndReasonMap`，即用于轮次结束、可合并扩展且以 `kind` 为标签的和类型。`turn/start` 只携带轮次编号；之后进入步骤的 `user/message` 批次记录其输入，`llm/retry` 则记录请求恢复。
 
 被中断的实时轮次以 `{ kind: 'aborted', reason: AgentCancelCause }` 结束，在持久 transcript（文本记录）中保留类型化取消原因。轮次失败携带 `{ kind: 'error', error }`；只有崩溃恢复会合成 `{ kind: 'interrupted' }`。
 

packages/core/session/src/types.ts

@@ -167,9 +167,9 @@ export type RequestHeaderReason = 'initial' | 'resume' | 'change'
  */
 export interface SessionEventMap {
   /**
-   * Opens turn `turn`. Every turn begins when the loop admits queued input;
-   * the following identified `user/message` event or batch records the
-   * admitted input.
+   * Opens turn `turn`. Every turn begins after the loop claims queued input
+   * and accepts the pre-step result; the following identified `user/message`
+   * event or batch records the messages entering the step.
    */
   'turn/start': { turn: number }
   /**
@@ -187,9 +187,8 @@ export interface SessionEventMap {
    * A user-role message on the model-visible surface: a direct human prompt
    * (the queued message claimed for this turn), a synthetic `agent.inject()`
    * context (file-change notices, subdir AGENTS.md, skill content, cron
-   * notifications, …), or an admitted goal continuation round. All three
-   * project their `content` verbatim; `source` tells them apart. An idle
-   * injection may append this event between turns without running the model.
+   * notifications, …), or an entered goal continuation round. All three
+   * project their `content` verbatim; `source` tells them apart.
    */
   'user/message': UserMessage
   /** Raw stream chunk — token-level replay fidelity. */