pi-proofline

Verifiable evidence for every pi agent run.

Every prompt you give pi becomes one JSON bundle: the exact provider payloads pi sent, the assistant messages it received, every tool execution — secrets redacted, sealed under a stable SHA-256 digest. Anyone can verify, diff, or sign the bundle with the proofline CLI. No trust in you, this extension, or pi required.

$ pi "fix the failing test"
  ...
  proofline: recorded .proofline/pi-run-20260812-134502-4c1f09a2.json (digest 59279513ca52)

$ uvx proofline verify .proofline/pi-run-20260812-134502-4c1f09a2.json
OK .proofline/pi-run-20260812-134502-4c1f09a2.json

How it works

            pi events                      capture                    evidence
 ┌─────────────────────────────┐   ┌────────────────────┐   ┌───────────────────────────┐
 │ before_provider_request ────┼──►│ request payload    │   │ .proofline/pi-run-*.json  │
 │ turn_end ───────────────────┼──►│ assistant message  ├──►│  · redacted               │
 │ tool_execution_start/end ───┼──►│ tool args, results │   │  · digest-sealed          │
 └─────────────────────────────┘   └────────────────────┘   │  · verifiable offline     │
                                                            └───────────────────────────┘

One run (prompt → agent settled) produces one bundle. The digest covers the evidence but not volatile fields (run_id, timestamps), so two runs with identical behavior share a digest — which is what makes bundles diffable and regression-testable.

Why

Publish sessions with proof. If you share coding sessions — for example with pi-share-hf — a bundle gives consumers what a session log cannot: tamper detection, machine-checked secret redaction, and an optional Ed25519 signature.

Attribute behavior changes. proofline diff a.json b.json compares runs semantically, ignoring IDs and timestamps. Swap models mid-project and keep evidence of what actually changed.

Audit what the agent did. The bundle records what went over the wire, captured at the provider boundary — not a reconstruction from session state.

Install

pi install git:github.com/Powfu-zwx/pi-proofline

The entire extension is one dependency-free TypeScript file: extensions/proofline.ts (650 lines). Reviewing it before installing takes about ten minutes, and you should.

Use

Recording is automatic. Bundles land in .proofline/ under the project directory.

Action	How
Check status	/proofline
Pause / resume	/proofline off · /proofline on
Change output directory	set PROOFLINE_DIR (absolute, or relative to the project)
Keep bundles out of git	add .proofline/ to .gitignore — or commit them as baselines

Verify, diff, and sign with the reference CLI — no pi required:

uvx proofline verify .proofline/pi-run-*.json
uvx proofline diff baseline.json current.json
uvx proofline keygen --out signing.key && uvx proofline sign bundle.json --key signing.key

Inside a bundle

Abridged from a real run (spec):

{
  "schema_version": "0.1",
  "actor":      { "type": "human+agent", "name": "admin", "version": "0.1.0" },
  "project":    { "name": "work", "revision": "4e7018d…", "dirty": null },
  "invocation": { "argv": ["node", "…/pi", "-p", "Say hello briefly"], "cwd": "…", "env_keys": ["PATH", "…"] },
  "steps": [
    {
      "step_id": "step-1",
      "kind": "model",
      "name": "mock/gpt-mock",
      "status": "ok",
      "input":  { "model": "gpt-mock", "messages": ["…exact provider payload…"], "tools": ["…"] },
      "output": { "role": "assistant", "content": ["…"], "usage": { "totalTokens": 17, "cost": { "total": 0 } } },
      "input_digest":  "b08bdb1d…",
      "output_digest": "ae31d466…",
      "metadata": { "http_status": 200, "turn_index": 0, "stop_reason": "stop" }
    }
  ],
  "redactions": ["/steps/0/input/messages/0/content"],
  "bundle_digest": "59279513ca52…"
}

Recorded — per model call: the full request payload, the finalized assistant message, usage and cost, HTTP status, stop reason. Per tool execution: name, arguments, result, error status. Per run: git revision and dirty state, working directory, environment variable names, session ID.

Never recorded — HTTP headers (API keys never enter the bundle), environment variable values, anything outside the run.

Redaction — pattern-based and best-effort, matching proofline's rules: secret-looking keys (api_key, token, authorization, …) and secret-looking values (OpenAI/GitHub/AWS/Slack key shapes, JWTs, bearer tokens, PEM headers) become [REDACTED], each listed as a JSON Pointer under redactions. proofline verify re-scans for leaks independently. Treat bundles as sensitive until reviewed, exactly as you would a session log.

Byte-level compatibility

A digest is only useful if an independent verifier recomputes the same bytes. That requires canonical JSON to agree across languages, and the disagreements are where implementations usually die:

• Key order — Python sorts by Unicode code point, JavaScript by UTF-16 unit; they disagree beyond the BMP.
• Float formatting — Python repr writes 3e-05 where JavaScript writes 0.00003.
• Surrogates — Python's encoder rejects what JavaScript strings happily carry.

This port resolves all three and proves it in CI: several hundred fuzzed vectors plus a complete bundle are generated in TypeScript on every push and verified with the released proofline package from PyPI. The e2e suite does the same against a real pi install.

Limitations

• Auxiliary LLM calls that bypass the turn lifecycle (compaction, summarization) appear as skipped steps: request preserved, response not captured.
• Aborted turns record whatever was captured before the abort.
• proofline replay is not wired up for pi runs; bundles are still verifiable and diffable evidence.

Development

npm install
npm run typecheck
npm test                       # unit tests — node --test, no build step
npm run emit-vectors           # write cross-language fixtures to out/
python tests/cross_verify.py   # requires: pip install proofline

End-to-end against a real pi install, no API key needed — run the mock provider, then point an isolated pi at it:

node tests/e2e/mock-provider.mjs &
export PI_CODING_AGENT_DIR=$(mktemp -d) PI_OFFLINE=1
cat > "$PI_CODING_AGENT_DIR/models.json" <<'EOF'
{ "providers": { "mock": { "baseUrl": "http://127.0.0.1:8377/v1", "api": "openai-completions",
  "apiKey": "dummy", "compat": { "supportsDeveloperRole": false, "supportsReasoningEffort": false },
  "models": [ { "id": "gpt-mock" } ] } } }
EOF
pi -p --no-session --provider mock --model gpt-mock -e ./extensions/proofline.ts "Say hello"
uvx proofline verify .proofline/pi-run-*.json

See also

• proofline — the protocol and reference implementation: verify, diff, replay, sign
• Run bundle spec — format and verification rules
• pi — the coding agent this extends

License

MIT