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.

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).

How the fixture works

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.

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.

Config

Key	Type	Default	Notes
`file`	string	`$DSH_SNAPSHOT_FILE`	Path to the per-scenario `session.jsonl` fixture. Required (config or env).
`overrideFile`	string	`$DSH_SNAPSHOT_OVERRIDE`	Optional path to a `ReplayEntry[]` sidecar that replaces the derived script.

- id: llm-replay
  name: '@deepseek-ai/dsh-llm-replay'
  # file/overrideFile default to $DSH_SNAPSHOT_FILE / $DSH_SNAPSHOT_OVERRIDE,
  # set by the snapshot harness per scenario.

Exports

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.
loadReplayScript(config) — resolve the ReplayEntry[] for a scenario (sidecar override if present, else derived from the JSONL; fail-loud if the fixture is missing).
deriveReplayScript(events) / parseSessionLog(text) — the pure helpers that turn a recorded session log into a script. 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.
Types ReplayEntry / ReplayConfig / Config.

Plugin export shape

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).