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Merge refreshed docs/i18n-batch-core into docs/i18n-batch-cds-postmortem

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# Conflicts:
#	.agents/notes/README.i18n.yaml
#	.agents/notes/README.zh.md
#	docs/core-data-structures/bash.md
#	docs/core-data-structures/code-runtime.md
#	docs/core-data-structures/compaction.md
#	docs/core-data-structures/scope.md
#	docs/core-data-structures/session-query.md
#	docs/core-data-structures/user-interaction.md
#	docs/core-data-structures/web.md
#	docs/rfc/README.md
#	scripts/translation-pairing.manifest.json
#	scripts/type-equiv.manifest.json
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Tianyi Cui
2026-07-22 22:26:24 +08:00
parent f72db5ac7b 3fd5d5dc2b
commit 58a531ebf5
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docs/core-data-structures/persistence.md
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@@ -4,16 +4,34 @@ English | [中文](persistence.zh.md)
The **durability seam** for the event log. [session.md](session.md) describes the in-memory `Session` — the append-only `SessionEvent` log that is the source of truth. This page describes how that log is made durable: the abstract `SessionPersistence` service, its backends, the flush checkpoint, crash recovery, and the metadata header that travels alongside the log. The event vocabulary the log carries is enumerated, member by member, in the generated [persistence log event catalog](../persistence-catalog.md).
The seam is a textbook [capability seam](../rfc/implemented/architecture/2026-06-13-capability-seams.md): one abstract service ([dsh-session-persistence](../../packages/session-persistence/session-persistence), `ctx.sessionPersistence`) defining create/append/load/list over the existing `SessionEvent` — **no parallel persisted type** — and two interchangeable backends that pass the same `runPersistenceContract` suite. See the [session-persistence RFC](../rfc/implemented/architecture/2026-06-14-session-persistence.md).
The seam is a textbook [capability seam](../../.agents/notes/implemented/architecture/2026-06-13-capability-seams.md): one abstract service ([dsh-session-persistence](../../packages/session-persistence/session-persistence), `ctx.sessionPersistence`) defining locate/create/append/load/list over the existing `SessionEvent` — **no parallel persisted type** — and two interchangeable backends that pass the same `runPersistenceContract` suite. See the [session-persistence Agent Note](../../.agents/notes/implemented/architecture/2026-06-14-session-persistence.md).
## The flush checkpoint
`session/event` is a *synchronous* notification; persistence plugins buffer it (write-behind) and drain at the awaited `session/flush` checkpoint the loop fires at every turn end. Flush is `ctx.parallel` (awaited): a turn's events are durably committed before the next turn starts, and the turn boundary is the commit boundary. A rejecting flush is reported via `agent/error` and the logger — never as a session event (it would land past the commit boundary), so the backend keeps its buffered events for the next flush.
`session/event` is a *synchronous* notification; persistence plugins buffer it (write-behind) until `session/flush`. The loop awaits an ordinary turn's checkpoint before claiming the next queue item; synchronous idle `inject()` schedules its checkpoint without blocking `send()`, and disposal still drains it. A successful flush durably commits the closed turn as one unit; a rejecting flush is reported through `agent/error` and the logger — never as a session event past the closed turn — while the backend keeps its buffered events for the next flush.
## Crash recovery preserves an interrupted turn
A backend that reloads a log crashed mid-turn finds an open `turn/start` with no `turn/end`. It does **not** truncate — a single turn can be huge in a long-horizon task (many steps, large tool output), and those events were durably appended before the crash. Instead it closes the orphaned turn with a synthetic `turn/end { reason: { kind: 'interrupted' } }`, keeping the log balanced and the turn-enclosure invariant intact. `interrupted` is the one `TurnEndReason` no loop emits (see [session.md](session.md#why-a-turn-ended-turnendreasonmap)).
## `SessionLocation` — optional per-session artifact target
`SessionPersistence.locate(meta)` synchronously resolves a backend-owned independent artifact without reading, creating, or flushing it. JSONL returns its absolute target path; SQLite returns `undefined` because sessions share one database. A returned path can therefore name a file that does not yet exist or lacks the current unflushed turn; it is a location hint, not authorization or a freshness guarantee.
```ts type-equiv
/**
* A backend-resolved, per-session local artifact location. The path is an
* absolute target path and can name an artifact that has not materialized yet.
* Consumers must treat it as a location hint, never as an authorization token.
*/
interface SessionLocation {
/** Backend-specific artifact kind, for example `jsonl`. */
readonly kind: string
/** Absolute path to this session's backend-owned artifact. */
readonly path: string
}
```
## `SessionHeader` — metadata beside the log
Per-session metadata travels **separately** from the event log: format version, cwd, lineage, and the seed boundary are storage concerns, not conversation events, so they stay out of `SessionEventMap` and never reach `deriveMessages()`. The header is attached to a `Session` via `session.header`.
@@ -21,6 +39,9 @@ Per-session metadata travels **separately** from the event log: format version,
Source: [`packages/core/session/src/types.ts`](../../packages/core/session/src/types.ts)
```ts type-equiv
/**
* Immutable validated storage metadata, kept outside the conversation event log.
*/
interface SessionHeader {
/**
* On-disk format version, stamped from {@link SESSION_FORMAT_VERSION} when the
@@ -37,43 +58,42 @@ interface SessionHeader {
/** The session this one was forked from (seed lineage), if any. */
readonly parentSession?: SessionId
/**
* How many leading events were INHERITED via a seed rather than produced by
* this session — the seed boundary. Set when a fork seeds a child with a
* prefix of the parent's log (= the seeded prefix length); absent/0 means the
* session produced all its own events. Persisted so a reload reconstructs the
* boundary instead of re-deriving it from the full stored log, and so a replay
* harness can skip the inherited prefix when deriving the child's OWN script
* (the seeded events are the parent's, not this child's model calls).
* How many leading events were inherited through a seed. Persisting this
* boundary lets resume and replay distinguish parent history from child work.
*/
readonly seedLength?: number
/**
* Delegation depth: absent (zero) for a top-level session, parent depth + 1
* for a subagent child. Persisted so a recursion budget survives restart and
* resume — a runtime-only depth would reset a resumed child to top-level.
*/
readonly delegationDepth?: number
}
```
## `CreateSessionOptions` — seeding and metadata
Creating a `Session` through the store takes a `seed` (replay/fork an existing event log) and `meta` (the storage-level fields the store folds into a `SessionHeader`). The store fills in `version`/`id` and defaults `createdAt`; the caller supplies the validated absolute `cwd`, the `parentSession` lineage, the `seedLength` seed boundary, and — only when reconstructing a persisted session — the original `createdAt` to preserve it.
Creating a `Session` through the store takes a `seed` (replay/fork an existing event log) and `meta` (the storage-level fields the store folds into a `SessionHeader`). The store fills in `version`/`id` and defaults `createdAt`; the caller supplies the validated absolute `cwd`, the `parentSession` lineage, the `seedLength` seed boundary, the `delegationDepth`, and — only when reconstructing a persisted session — the original `createdAt` to preserve it.
```ts type-equiv
/**
* Options for creating a {@link Session} via the store. `seed` replays/forks
* an existing event log; `meta` carries the caller-supplied storage fields the
* store folds into a {@link SessionHeader}.
*/
interface CreateSessionOptions {
/** Events to seed the new session with (replay/fork). */
readonly seed?: readonly SessionEvent[]
/**
* Creation metadata. The store fills in `version`/`id` and defaults
* `createdAt` to now; the caller supplies the storage-level fields (validated
* absolute `cwd`, `parentSession` lineage, the seed boundary `seedLength`, and
* — when reconstructing a persisted session — the original `createdAt` to
* preserve it).
*
* `seedLength` is EXPLICIT, not inferred from `seed.length`: a reconstruction
* (resume/load) seeds the WHOLE stored log, so its `seed.length` is the full
* length, not the original boundary — the caller must pass the persisted
* boundary back. A fresh fork passes its actual seeded-prefix length.
* Storage metadata read once before publication. `seedLength` is explicit
* because a resumed seed contains the full stored log, not only its inherited prefix.
*/
readonly meta?: {
readonly cwd?: string
readonly parentSession?: SessionId
readonly createdAt?: number
readonly seedLength?: number
readonly delegationDepth?: number
}
}
```
@@ -82,9 +102,9 @@ Replay/fork is therefore `ctx.sessions.create(id, { seed: seedEvents })`; resumi
## The backends
Both implement the same abstract `SessionPersistence` (create/append/load/list over `SessionEvent`) and pass `runPersistenceContract`, proving the seam is genuinely backend-agnostic:
Both implement the same abstract `SessionPersistence` (locate/create/append/load/list over `SessionEvent`) and pass `runPersistenceContract`, proving the seam is genuinely backend-agnostic:
- **[dsh-session-persistence-jsonl](../../packages/session-persistence/session-persistence-jsonl)** — an append-only JSONL log per session with crash-safe atomic writes, the interrupted-turn crash recovery above, and a read/replay path.
- **[dsh-session-persistence-jsonl](../../packages/session-persistence/session-persistence-jsonl)** — an append-only logical JSONL log per session, stored as checksummed concatenated Zstandard frames by default or raw lines by configuration, with crash-safe atomic writes, interrupted-turn recovery, and a read/replay path.
- **[dsh-session-persistence-sqlite](../../packages/session-persistence/session-persistence-sqlite)** — `node:sqlite`, one row per `SessionEvent`. The row shape `(session_id, seq, type, time, data, source_event_seqs, surface_op)` maps 1:1 onto the event, including optional surface metadata, so there is no parallel persisted schema to keep in sync.
Multiple backends sharing one on-disk session coordinate writes through the [shared persistence write-coordinator](../rfc/implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md).
Multiple backends sharing one on-disk session coordinate writes through the [shared persistence write-coordinator](../../.agents/notes/implemented/architecture/2026-06-18-shared-persistence-write-coordinator.md).