feat(session): project the inherited-history boundary into the log

A plugin owning a standalone open/close bracket cannot tell a dead marker
from a live one: an unmatched `compact/start` reads identically whether the
previous writer died mid-compaction or a compaction is running now.
`Session.firstLiveSeq` already holds that answer exactly, but only in memory.

Append the log-only `session/inherited` event at that seq from the seeded
constructor — the single waist all six seeded-start paths pass through
(resume, configured startup on a persisted id, `sessions.fork()`, a subagent
fork child, `adopt()`'s live prefix, and a bare seeded `create`). Read it
through the new `isInheritedSeq(events, seq)`.

The constructor placement means persistence needs no changes: the marker is
already in `events` when a backend captures the creation seed, so it rides
the ordinary seed path with no load-time write. It also covers fork, where
the inherited bracket's owner may still be running — the case a
persistence-layer boundary could not reach.

Activity ordering excludes the boundary through `lastActivityTime()`, since
lazy resume makes browsing a pickup and the three call sites would otherwise
float every opened session to the top of a picker or list.

.agents/notes/rejected/architecture/2026-07-29-session-resumed-log-boundary.i18n.yaml

@@ -0,0 +1,6 @@
+# Bilingual-pair consistency record (docs/i18n/README.md): the git blob hash of each
+# 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/rejected/architecture/2026-07-29-session-resumed-log-boundary.md
+2026-07-29-session-resumed-log-boundary.md: 6dbe44cbd8354369e8ed56d8cc838e9771dbaa52
+2026-07-29-session-resumed-log-boundary.zh.md: f035773b896131ca87a70b58b19cfafb280601e4

.agents/notes/rejected/architecture/2026-07-29-session-resumed-log-boundary.md

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+# Agent Note: Record the resume process boundary in the session log
+
+Status: rejected — the boundary belongs at the seeded-`Session` constructor, which also covers fork and replay; superseded by [the inherited-history boundary](../../implemented/architecture/2026-07-30-session-inherited-log-boundary.md)
+
+English | [中文](2026-07-29-session-resumed-log-boundary.zh.md)
+
+## Problem
+
+A session's durable log gave no evidence that it had changed processes. `session/created`, `session/disposed`, and `session/flush` are cordis runtime signals rather than `SessionEventMap` members, and `agent/session-start` carries a `SessionStartSource` but is emit-only and never logged. Reading a stored log therefore gave no hint that anything had been resumed.
+
+That gap makes one class of question unanswerable. A plugin that owns a standalone open/close pair in the log — compaction's `compact/start` … `compact/end` is the only one today — must distinguish an unmatched opening marker left by a process that died mid-operation from one an operation is holding right now. Those two states are **byte-identical in stored history**. Without a boundary the owner has to choose between refusing forever (an unmatched marker wedges the operation permanently, and because automatic compaction failure is warn-and-continue the user-visible result is that compaction silently stops working until the context window overflows) and proceeding always (which defeats the point of holding a lock).
+
+The pressure to fix this is immediate: moving `compact/start` to its real time point, before summarization, widens the crash window from a few microseconds of synchronous appends to the length of a whole model call, so orphaned brackets go from rare to routine.
+
+## Proposal
+
+`@deepseek-ai/dsh-session-persistence` declares one log-only `session/resumed` with an empty payload and appends exactly one at the end of every cold load, in the same `commitRepair` batch as any crash-repair closers and positioned after them — so every event below the boundary was written by a writer that is no longer tracking this log. Ownership lands narrowly on `loadCore()`, the cold-load path reached by `load()` and by `adopt()`. `loadLiveSnapshot()` appends nothing, and the non-mutating `inspect()`/`readFrom()` reads never write one.
+
+The predicate a bracket owner evaluates is purely a function of the log: an unmatched opening marker with a `session/resumed` after it is stale, and one with no `session/resumed` after it is live.
+
+`time` is `Date.now()` floored at the log's greatest `time`, deliberately unlike the synthetic closers, which reuse the last real event's timestamp so repair output stays a deterministic function of stored history. The wall clock is not monotonic — an NTP step, a VM restore, or a log copied from a machine that was ahead can put it behind events already stored — so the floor keeps every cross-boundary duration non-negative. The floor is durable, because the clamped boundary is stored and joins the log's maximum: one future-dated event pins every later boundary in that log to the same instant until wall time passes it.
+
+**The predicate distinguishes process succession, not concurrent writers.** `load()`'s liveness guard is `ctx.sessions.get(id)`, which only sees sessions live in *this* runtime, and no backend takes a cross-process per-session lock. So process B cold-loading a session A currently owns writes a boundary after A's still-open bracket. A consumer that must tolerate concurrent writers still needs a liveness signal beyond the log.
+
+## Why this was rejected
+
+Two reasons, found while reviewing where the marker belonged.
+
+**It covers no fork.** `sessions.fork()` and a subagent fork child construct a seeded session without touching persistence, so neither gets a boundary. A forked child inherits its parent's prefix verbatim — including an open `compact/start` the parent is still holding — which is the one case where the inherited bracket's owner is demonstrably alive. The predicate was unavailable exactly where it was most needed.
+
+**Minting the marker at load made a read path a durable write.** Every consequence the review surfaced traced to that: a revision bump on every cold load, a `commitRepair` batch on a balanced log with nothing to repair, the durable time floor above, a load that fails against a read-only store, and a marked log after a resume the caller then cancelled. None of these are wrong given the placement; they are the placement's cost.
+
+The successor keeps the problem statement and the concurrent-writer scope limit unchanged, and moves the write to `Session`'s constructor — the single waist all six seeded-start paths pass through, fork included. Because the marker then rides the ordinary seed-persistence path, the whole durable-write surface above disappears.
+
+## Alternatives considered
+
+**Use `Session.firstLiveSeq` as the staleness predicate.** Dismissed here on the grounds that it is documented as deliberately not persisted, so the same stored log yields different answers in different processes and a read-only reader cannot evaluate it at all. That reasoning was sound about the field and wrong about the conclusion: the fix is to persist a projection of it rather than to compute the boundary somewhere else. This is the alternative that became the successor.
+
+**Declare the event in core (`dsh-session`).** Rejected here because "the constructor cannot distinguish resume from fork or replay." That is true and turned out not to matter — the distinction is not needed, since inherited history is dead history in all three cases.
+
+**Teach `interruptedTurnClosers` to close `compact/*`.** Rejected: `compact/*` is plugin-owned vocabulary and core must not know it. Core closes turn, step, and tool boundaries — the relations it owns. The successor keeps this rejection.
+
+**Lazy self-repair: the owner appends a synthetic closing marker when it finds an orphan.** A write inside a read-shaped check, and it needs an invariant exception for a numbered owner whose turn has already closed.
+
+**A merge-extensible repair-contributor registry in core.** The right shape once a second consumer exists; with one consumer today, `packages/AGENTS.md` says not to split a seam preemptively.
+
+**Write the boundary only when repair actually occurred.** Rejected: the predicate must hold for an orderly restart too, where there is nothing to repair. The successor keeps this rejection.
+
+## Related
+
+The cold-session `updatedAt` skew this proposal documented is scoped in [the last-activity-index Agent Note](../../proposed/architecture/2026-07-29-durable-last-activity-index.md). That defect predates this proposal and survives its rejection: it is caused by mtime counting every durable write, not by any one boundary.

.agents/notes/rejected/architecture/2026-07-29-session-resumed-log-boundary.zh.md

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+# Agent Note: 在会话日志中记录恢复的进程边界
+
+Status: rejected — 边界应当落在带种子 `Session` 的构造函数上，那里同时覆盖 fork 与回放；由[继承历史边界](../../implemented/architecture/2026-07-30-session-inherited-log-boundary.md)取代
+
+[English](2026-07-29-session-resumed-log-boundary.md) | 中文
+
+## Problem
+
+会话的持久日志此前无法证明它换过进程。`session/created`、`session/disposed` 和 `session/flush` 是 cordis 运行时信号，而不是 `SessionEventMap` 成员；`agent/session-start` 虽然携带 `SessionStartSource`，却只用于 emit，从不记录。因此，读取一份已存储日志得不到任何关于「曾经发生过恢复」的线索。
+
+这一空缺让一类问题无法回答。在日志中拥有独立开始／结束事件对的插件必须区分两种未匹配的起始标记：一种由某个在操作中途死亡的进程留下，另一种正被当前某项操作持有；今天符合这一形态的只有压缩的 `compact/start` … `compact/end`。这两种状态**在已存储历史中逐字节相同**。没有边界，所有方只能在两种做法之间选择：永远拒绝（一个未匹配的标记会永久卡住该操作，而自动压缩失败采取警告并继续的策略，因此用户可见的结果是压缩静默停止工作，直到上下文窗口溢出），或者始终继续（这让持有锁失去了意义）。
+
+修复它的压力是即刻的：把 `compact/start` 移到摘要生成之前这个真实的时间点，会把崩溃窗口从几微秒的同步追加扩大为一整次模型调用的时长，孤儿括号也就从罕见变为常态。
+
+## Proposal
+
+`@deepseek-ai/dsh-session-persistence` 声明唯一一个纯日志事件 `session/resumed`，其载荷为空，并在每次冷加载结束时恰好追加一条：与崩溃修复产生的 closers 同处一个 `commitRepair` 批次，且排在它们之后。因此，该边界之下的每个事件都是由一个不再追踪这份日志的写入方写下的。所有权狭窄地落在 `loadCore()`，也就是 `load()` 与 `adopt()` 到达的冷加载路径。`loadLiveSnapshot()` 不追加任何内容，非变更性的 `inspect()`／`readFrom()` 读取也从不写入。
+
+括号所有方求值的谓词纯粹是日志的函数：未匹配的起始标记之后有 `session/resumed` 的就是陈旧的，之后没有的就是存活的。
+
+`time` 取 `Date.now()` 并以日志的最大 `time` 为下限，刻意区别于合成 closers——后者复用最后一个真实事件的时间戳，以便修复输出始终是已存储历史的确定性函数。挂钟并非单调：一次 NTP 跳变、一次虚拟机恢复，或一份从走快的机器上拷来的日志，都可能让它落在已存储事件之后，因此这个下限让跨边界的时长都非负。该下限是持久的，因为被钳制的边界本身会被存储并加入日志的最大值：一个未来时间的事件会把该日志中之后的每个边界都钉在同一时刻，直到挂钟时间越过它。
+
+**该谓词区分的是进程接替，不是并发写入方。** `load()` 的存活性守卫是 `ctx.sessions.get(id)`，它只看到*本*运行时中存活的会话，而且没有任何后端会取跨进程的按会话锁。因此，进程 B 冷加载一个 A 当前拥有的会话时，会在 A 仍然开放的括号之后写入一个边界。必须容忍并发写入方的消费方仍然需要日志之外的存活信号。
+
+## 为什么被否决
+
+两个原因，都是在复审标记应当落在何处时发现的。
+
+**它完全覆盖不到 fork。** `sessions.fork()` 与子代理 fork 子会话在不触及持久化的情况下构造带种子会话，因此两者都拿不到边界。fork 子会话会逐字节继承父会话的前缀——包括父会话仍然持有的开放 `compact/start`——而这恰恰是继承括号的所有方明显还活着的唯一情形。谓词偏偏在最需要它的地方不可用。
+
+**在加载时铸造标记，把读取路径变成了持久写入。** 复审暴露出的每一项后果都源于此：每次冷加载都递增 revision、对一份无需修复的平衡日志也要走 `commitRepair`、上文那个持久时间下限、加载在只读存储上会失败，以及调用方随后取消的恢复也已留下标记。这些在该放置方式下都不算错，它们就是该放置方式的成本。
+
+取代方案保留问题陈述与并发写入方的适用范围限制不变，并把写入移到 `Session` 的构造函数——全部六条带种子启动路径（含 fork）必经的唯一收窄处。由于标记随后走普通的种子持久化路径，上述整个持久写入面就消失了。
+
+## Alternatives considered
+
+**用 `Session.firstLiveSeq` 作为陈旧性谓词。** 此处以「文档明确它有意不做持久化，因此同一份已存储日志在不同进程中会给出不同答案，而只读读取方根本无法对它求值」为理由否决。这个推理对字段本身是成立的，但结论错了：正确的修法是持久化它的一个投影，而不是把边界挪到别处去算。这条替代方案正是后来的取代方案。
+
+**在核心（`dsh-session`）中声明该事件。** 此处以「构造函数无法把恢复与 fork 或回放区分开」为理由否决。这句话是对的，但事实证明它无关紧要——并不需要这种区分，因为在这三种情形下继承历史都是死历史。
+
+**教 `interruptedTurnClosers` 关闭 `compact/*`。** 否决：`compact/*` 是插件所属词汇，核心不得知道它。核心只关闭轮次、步骤和工具边界，也就是它自己拥有的关系。取代方案保留这条否决。
+
+**惰性自修复：所有方发现孤儿时自行追加一条合成的关闭标记。** 这是在一次形似读取的检查中执行写入，而且需要为一个带轮次编号、其轮次却已经关闭的所有方开一个不变式例外。
+
+**在核心中建一个可合并扩展的修复贡献方注册表。** 一旦出现第二个消费方，这就是正确的形状；今天只有一个消费方，而 `packages/AGENTS.md` 要求不要预先拆分 seam。
+
+**仅在确实发生了修复时才写入边界。** 否决：该谓词对有序重启同样必须成立，而那时没有任何东西需要修复。取代方案保留这条否决。
+
+## 相关
+
+本提案记录过的冷会话 `updatedAt` 偏斜，范围界定在[最后活动索引 Agent Note](../../proposed/architecture/2026-07-29-durable-last-activity-index.md)。该缺陷早于本提案存在，并且在本提案被否决后依然存在：它的成因是 mtime 会计入每一次持久写入，而不是某一个边界。