Tianyi Cui
e68496fd79
The snapshot tier was built single-session: dsh-llm-replay served calls from one global positional cursor, and the harness harvested one session log. A subagent runs as a second agent with its own session, so a parent→child scenario could neither replay deterministically nor harvest the child's log. This resolves the TODO(subagent-snapshots) deferral from the subagent RFC. - Stamp the calling session id onto the model request: GenerateOptions.sessionId (typed Branded<'SessionId'> to avoid the dsh-llm↔dsh-session cycle), set by the agent loop from agent.session.id. Adapters ignore it; an llm/stream listener routes by it. - Key replay per session: dsh-llm-replay loads the parent log plus one per child (childFiles / $DSH_SNAPSHOT_CHILD_FILES), derives a script per recorded session, and binds each live (freshly-random) session to a recorded script by first-call order — parent first (earliest createdAt, first to stream). Keys by WHO calls, so it survives a future concurrent/backgrounded subagent; a global cursor would not. An unrecorded extra session fails loud. - Harvest every log: the harness collects all .jsonl across cwd buckets, ordered primary-first (top-level, then children by createdAt), and RunResult exposes the plural sessionLogs. The spec writes each back on record (session.jsonl + session.<n>.jsonl) and diffs each against its fixture on replay. - Wire the subagent seam + spawn + fork + tool into the acp-agent example (both cordis configs) and add two nested scenarios recorded against the real API: subagent-spawn (parent + 1 child) and subagent-multi (parent + 2 children, 3 sessions). Both replay keyless in the default gate. A new RFC documents the design (docs/rfc/implemented/testing/). Single-session replay is unchanged (a call with no sessionId is one anonymous primary session). TODO follow-up: a dedicated branded-ids package could own the SessionId brand and dissolve the cross-package cycle note; out of scope for this testing PR.
46 lines
4.5 KiB
Markdown
46 lines
4.5 KiB
Markdown
# @deepseek-ai/dsh-llm-replay
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A replay LLM plugin for keyless snapshot tests. It installs a single `llm/stream` waterfall listener that short-circuits the waterfall (never calls `next()`) and yields model streams reconstructed from a recorded **session JSONL** fixture — so a test can boot the real agent against a fixed model transcript with no API key.
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Its consumer is the ACP snapshot harness in `examples/acp-agent`, which loads this plugin (via `cordis.snapshot.yml`) in place of a real LLM adapter. The package exists so its derive/parse/replay logic falls under the per-file 100% coverage gate on `packages/*/src` (the same logic, while it lived under `examples/`, was outside the gate).
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## How the fixture works
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The fixture IS the persisted session log (`<scenario>/session.jsonl`). Its `assistant/chunk` events carry every `StreamChunk`, so grouping them by `(turn, step)` reconstructs each `stream()` call's chunk sequence (one model call per loop step). Recording is therefore "run the real agent once and harvest the `.jsonl`", done by the snapshot harness — this plugin does not record.
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Two failure modes are not reconstructable from `assistant/chunk` alone — a pure throw before any chunk (e.g. an HTTP 401, where the log holds only a `turn/end {error}` and no chunks) and a cancel/hang (timing, not chunk content). A scenario that needs those supplies an optional sidecar (`<scenario>/replay.override.json`: a `ReplayEntry[]`) that REPLACES the derived script.
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## Nested agents: per-session keying
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A scenario where a parent agent delegates to in-process subagents records more than one log: the parent (`session.jsonl`) plus one per child (`session.1.jsonl`, …). Each agent runs as its own `Session` on the same context, so replay must serve each one its own script.
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Replay keys every call by its calling session id (`GenerateOptions.sessionId`, stamped by the agent loop). Live session ids are freshly random each run and never equal the recorded ones, so a live session binds to a recorded script by **first-call order**: scripts are ordered by header `createdAt` (parent first — it streams before it can delegate), and the first live session to make any call claims the first script, the next new session the next, and so on. Each session then advances its own cursor. A call with no `sessionId` is one anonymous session bound to the primary script, so single-session scenarios behave exactly as before. More distinct live sessions than recorded scripts fails loud.
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## Config
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| Key | Type | Default | Notes |
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|---|---|---|---|
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| `file` | string | `$DSH_SNAPSHOT_FILE` | Path to the primary (parent) `session.jsonl` fixture. Required (config or env). |
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| `overrideFile` | string | `$DSH_SNAPSHOT_OVERRIDE` | Optional path to a `ReplayEntry[]` sidecar that replaces the PRIMARY session's derived script. |
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| `childFiles` | string[] | `$DSH_SNAPSHOT_CHILD_FILES` (path-delimited) | Recorded subagent child-session logs for a nested scenario; empty for a single-session scenario. |
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```yaml
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- id: llm-replay
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name: '@deepseek-ai/dsh-llm-replay'
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# file/overrideFile/childFiles default to $DSH_SNAPSHOT_FILE /
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# $DSH_SNAPSHOT_OVERRIDE / $DSH_SNAPSHOT_CHILD_FILES, set by the snapshot
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# harness per scenario.
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```
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## Exports
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- `installLlmReplay(ctx, config)` — install the `llm/stream` listener; returns the disposer (HMR safety). Use this in tests to drive replay without the Loader or env vars.
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- `loadSessionScripts(config)` — resolve the ordered `SessionScript[]` (primary + children) for a scenario, ready to bind to live sessions in first-call order.
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- `loadReplayScript(config)` — resolve the `ReplayEntry[]` for the PRIMARY session only (sidecar override if present, else derived from the JSONL; fail-loud if the fixture is missing).
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- `deriveReplayScript(events)` / `parseSessionLog(text)` / `parseSessionHeader(text)` — the pure helpers that turn a recorded session log into a script and read its header `id`/`createdAt`. A derived group must end in a `finish` chunk; a group without one is the fingerprint of a thrown `stream()` and must instead be expressed via an override sidecar.
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- Types `ReplayEntry` / `SessionScript` / `ReplayConfig` / `Config`.
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## Plugin export shape
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Named `name` / `inject` / `Config` / `apply`, with **no default export**: the cordis Loader's `unwrapExports` does `exports.default ?? exports`, so a stray default would collapse the module to the bare function and drop the `inject` namespace (see [docs/postmortem/0001](../../../docs/postmortem/0001-acp-default-export-drops-inject.md)).
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