deepseek-harness/docs/acp/snapshot-replay.md

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# ACP Snapshot Replay

Maintenance mode: curated Mermaid sequence based on the snapshot test harness.

This graph explains what a snapshot scenario proves: recorded real-model session logs are replayed keylessly, ACP stdout is normalized and diffed, and scenario workspaces preserve tool side effects that the UI stream alone cannot prove.

```mermaid
sequenceDiagram
  participant Recorder as Real API recording
  participant Fixture as snapshot fixture
  participant Workspace
  participant Replay as llm-replay adapter
  participant ACP as acp-agent subprocess
  participant Golden as stdout golden
  Recorder->>Fixture: session.jsonl + workspace inputs
  Fixture->>Workspace: seed files and hook configs
  Fixture->>Replay: recorded StreamChunk script
  Replay->>ACP: deterministic <code>llm/stream</code> chunks
  ACP->>Workspace: bash, fs, and hook side effects
  ACP->>Golden: normalized sessionUpdate stream
  Golden-->>ACP: diff must be empty
```

The fs and hook snapshot matrix is valuable because it proves world state, hook decisions, and failed tool-card rendering, not just that replay returns text.