docs: document session preparation flow

2026-08-05 22:54:55 +08:00
parent deefceaf8a
commit e089ef92d8
26 changed files with 328 additions and 108 deletions
@@ -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/session-persistence/session-persistence-jsonl/README.md
-README.md: 7bf6ba2596fb0cf042a2318cfe01f65689131af5
-README.zh.md: afcf06af31ea0f9774d1d6f91310c3493e3eced2
+README.md: 55b802c57c27c771e0259451924501e5fb367911
+README.zh.md: a5e71f27990938576d5a77bf182dbd6919c047f1
@@ -26,6 +26,7 @@ The JSONL durable session-persistence backend — a concrete `SessionPersistence
 | `root` | `string` (required) | Root directory for all session files. **No default** — a `process.cwd()` default would scatter files as the process's cwd changes (bash calls, subprocesses). An existing root must be a readable directory; an absent root is created on first materialization. |
 | `packChunks` | `boolean` (default `true`) | Write eligible delta-chunk runs as packed rows (~60% smaller logical logs measured on a real coding session). Set `false` for one-event-per-line diagnostics; reading packed rows works regardless of this write-side switch. |
 | `compression` | `'zstd' \| 'none'` | Defaults to `'zstd'`; `'none'` retains newline-delimited UTF-8 text. |
+| `preparedSessionCacheSize` | positive integer (default `5`) | Maximum unpublished Sessions retained after cold history inspection for reuse by resume. |

 `locate(meta)` returns `{ kind: 'jsonl', path }` for the fixed transcript inside the resolved project/session directories. It performs no filesystem I/O: the target can be returned before the directory or file exists, and an existing file contains only the last flushed prefix.

@@ -41,7 +42,7 @@ A root belongs to one encoding. Startup discovery and targeted lookup reject the
 - **Lazy materialization.** `create(meta)` writes nothing; on the first `append`, the backend writes and `fsync`s the encoded header and first batch in a temporary file. POSIX publishes it without overwrite via a hard link and `fsync`s the parent directory. Windows publishes it without overwrite via `MoveFileExW(..., MOVEFILE_WRITE_THROUGH)` and creates missing directories through the same write-through pattern. A created-but-never-appended session leaves nothing on disk and is absent from `list`.
 - **Append-only.** Flushed events are never rewritten. Subsequent raw batches append lines; compressed batches append one frame. Both paths `fsync`, and a caught write or sync failure rolls the file back to its prior byte length.
 - **Crash recovery — preserve valid tail work.** `load` validates every complete compressed frame and scans their decompressed JSONL. If the last frame is structurally incomplete, the reader keeps its complete decoded records, truncates from that frame's start, and re-encodes those records with the synthetic tool, step, and turn closers required by the shared [persistence contract](../../../.agents/notes/implemented/architecture/2026-06-14-session-persistence.md). Raw mode truncates from its first incomplete line. A checksum/decompression failure in a complete frame, or a defect at or before the last committed `turn/end`, is corruption and rejects.
- **Non-mutating inspection.** `inspect()` returns the detached valid prefix without truncating an incomplete tail or closing an interrupted turn, and leaves the lightweight revision unchanged.
+- **Non-mutating inspection.** `inspect()` returns an immutable balanced logical view and may synthesize recovery closers in memory, without truncating an incomplete tail or changing the lightweight revision.
 - **Contiguous-seq.** `append` rejects a batch whose first `seq` does not continue the stored log, and rejects non-JSON-serializable `event.data` naming the offending event type.
 - **Lightweight revisions.** `listSnapshots(signal?)` identifies a log by its device, inode, size, and nanosecond timestamps, avoiding a full-log parse while changing after append, repair, replacement, or store changes. It forwards the exact signal through artifact discovery and checks cancellation around every `stat`; because filesystem `stat` is not interruptible, cancellation waits for the active call to settle, then rejects without starting another.

@@ -26,6 +26,7 @@ JSONL 持久会话存储后端：`SessionPersistence` 的一个具体实现（`d
 | `root` | `string`（必需） | 所有会话文件的根目录。**无默认值**：`process.cwd()` 默认值会随进程 cwd 变更（bash 调用、子进程）而分散文件。现有根必须是可读目录；缺失根在第一次实体化时创建。 |
 | `packChunks` | `boolean`（默认 `true`） | 将符合条件的 delta 分片连续段写为打包行（在真实编码会话上测得逻辑日志约小 60%）。设为 `false` 可用于每事件一行诊断；无论该写入侧开关如何，都能读取打包行。 |
 | `compression` | `'zstd' \| 'none'` | 默认 `'zstd'`；`'none'` 保留换行分隔 UTF-8 文本。 |
+| `preparedSessionCacheSize` | 正整数（默认 `5`） | 冷历史检查后保留、供恢复复用的未发布 Session 数量上限。 |

 `locate(meta)` 返回已解析项目/会话目录内固定 transcript 的 `{ kind: 'jsonl', path }`。它不执行文件系统 I/O：可以在目录或文件存在前返回目标，现有文件也只包含最近一次 flush 完成的前缀。

@@ -41,7 +42,7 @@ JSONL 持久会话存储后端：`SessionPersistence` 的一个具体实现（`d
 - **延迟实体化。**`create(meta)` 不写入；第一次 `append` 将编码 header 和第一批写入临时文件并执行 `fsync`。POSIX 通过硬链接无覆盖发布，并对父目录 `fsync`。Windows 通过 `MoveFileExW(..., MOVEFILE_WRITE_THROUGH)` 无覆盖发布，并通过同一 write-through pattern 创建缺失目录。已创建但从未 append 的会话不留下磁盘内容，不在 `list` 中。
 - **仅追加。** 已 flush 事件绝不重写。后续原始批次 append 行；压缩批次 append 一个 frame。两条路径都执行 `fsync`，并在捕获到写入或同步失败时回滚到之前字节长度。
 - **崩溃恢复：保留有效尾部工作。**`load` 验证每个完整压缩 frame，并扫描解压 JSONL。最后 frame 结构不完整时，读取器保留其完整解码记录，从 frame 开头截断，并使用共享[持久化契约](../../../.agents/notes/implemented/architecture/2026-06-14-session-persistence.md) 需要的合成工具、步骤和轮次 closer 重新编码这些记录。原始 mode 从第一个不完整行截断。完整 frame 中的 checksum/解压失败，或位于最后已提交的 `turn/end` 处或之前的缺陷属于损坏，会被拒绝。
- **非变更检查。**`inspect()` 返回脱离的有效前缀，不截断不完整尾部或关闭中断轮次，并保持轻量修订不变。
+- **非变更检查。**`inspect()` 返回不可变、平衡的逻辑视图，并可在内存中合成恢复 closer，但不会截断不完整尾部或更改轻量修订。
 - **连续 seq。**`append` 拒绝第一个 `seq` 不继续已存储日志的批次，并拒绝非 JSON 可序列化 `event.data`，同时命名违规事件类型。
 - **轻量修订。**`listSnapshots(signal?)` 使用 device、inode、size 和纳秒时间戳标识日志，避免解析完整日志；该标识会在 append、修复、替换或存储变更后改变。它通过产物发现转发精确信号，并在每个 `stat` 前后检查取消；由于文件系统 `stat` 不可中断，取消会等待活动调用完成，然后在不启动另一次调用的情况下拒绝。