PaperClipAI/packages/paperclip-runner/docs/tutorials/phase-02-local-runner.md

Phase 2: Run the Local Runner and Fake Harness

What this phase is

Phase 2 is a local live-run path. A TypeScript mock core starts a Rust runner. The Rust runner starts a scripted fake harness. The processes use JSON lines over stdio.

What this phase proves

This phase proves that a native session can run from start to finish without Paperclip, a network provider, or a real model. It proves cleanup, request resolution, interruption, bounded logs, one terminal result, and live/replay parity.

Prerequisites

• Node.js 20 or newer
• pnpm 9 or newer
• a stable Rust toolchain with cargo
• a Chromium-compatible browser

Run every command from the repository root on the PAP-16679-paperclip-runner branch. Install the package dependencies and browser:

pnpm install --filter @paperclipai/paperclip-runner --lockfile=false --ignore-scripts --dev
pnpm --filter @paperclipai/paperclip-runner exec playwright install chromium

On a minimal Linux host, install the browser libraries too:

pnpm --filter @paperclipai/paperclip-runner exec playwright install-deps chromium

playwright install-deps requires root. On a Debian or Ubuntu host where root is unavailable, use the package's rootless verification command instead. It downloads the required browser-library packages into a user-owned cache, extracts them without installing system packages, and scopes LD_LIBRARY_PATH to the verification process:

pnpm --filter @paperclipai/paperclip-runner verify:rootless

1. Run the package verification path

pnpm --filter @paperclipai/paperclip-runner verify

Expected: Rust, TypeScript, protocol, boundary, documentation, and browser checks pass. The final Phase 2 line reports one terminal event and a successful semantic result.

2. Run the happy path in the CLI

pnpm --filter @paperclipai/paperclip-runner trace:phase2 -- --scenario happy-path --quiet

Expected summary facts:

• eventCount is 19;
• terminalCount is 1;
• semanticResult is done;
• harness and runner exit codes are 0.

Capture the live trace as a validated replay fixture:

pnpm --filter @paperclipai/paperclip-runner record:phase2

The command writes packages/paperclip-runner/knowledge/evidence/phase-02-happy-path.json.

3. Run the scripted control flows

pnpm --filter @paperclipai/paperclip-runner trace:phase2 -- --scenario permission-input --quiet
pnpm --filter @paperclipai/paperclip-runner trace:phase2 -- --scenario interrupted --quiet
pnpm --filter @paperclipai/paperclip-runner trace:phase2 -- --scenario error --quiet
pnpm --filter @paperclipai/paperclip-runner trace:phase2 -- --scenario duplicate-terminal --quiet
pnpm --filter @paperclipai/paperclip-runner trace:phase2 -- --scenario happy-path --duplicate-turn-command --quiet

Expected:

• permission and input finish with done;
• interruption exits the harness with 130 and reports yielded;
• scripted error exits the harness with 7 and reports yielded;
• duplicate terminal still reports terminalCount: 1;
• duplicate turn command does not start a second turn.

4. Use the live browser

Start the package-local server:

pnpm --filter @paperclipai/paperclip-runner browser:dev --host 127.0.0.1 --port 4179

Open http://127.0.0.1:4179, then follow these steps:

1. Keep Happy path selected and choose Start local run.
2. Confirm the terminal badge says succeeded.
3. Confirm Harness process exit is 0 and Semantic result is done.
4. Confirm Live and replay reducer output says Match.
5. Select Permission and input, start the run, and choose Allow.
6. Enter a trace name and choose Send input. Confirm the run completes. Each interactive request remains open for five minutes. If it expires, the page reports that the run finished and asks you to start a new run.
7. Select Interruption, start the run, and choose Interrupt turn when the button becomes active.
8. Confirm the terminal badge says cancelled, the semantic result says yielded, and the timeline contains one run.terminal event.
9. Switch to Static replay and confirm the Phase 1 fixture path still works.

Stop Vite with Ctrl+C.

The browser regression suite writes its temporary screenshots under the ignored packages/paperclip-runner/test-results/ directory. It never rewrites the committed evidence images linked below.

5. Inspect the evidence

• Complete live run
• Permission request
• Interrupted run
• Exact verification record
• Engineering journal

What this proves

• the Rust runner owns and cleans the fake-harness process group;
• the fake driver emits deterministic live events and requests;
• logs are bounded;
• process exit and semantic result stay separate;
• duplicate commands and terminal proposals do not repeat effects;
• every browser event passes the Phase 1 validator and reducer;
• replay after completion produces the same final snapshot.

Phase 3 must not begin until the Phase 2 human checkpoint is accepted.