pi2

An implementation of Harness² on Pi Durable.

You give pi2 a task and a workspace. pi2 does the task and proposes changes to the harness. It tests each change on a new copy of the workspace. Then it keeps the best result and records lessons for the next tasks. pi2 does not change the model weights.

Quick start

You must have Node.js 22.19 or newer.

npm ci --ignore-scripts
npm run build

export OPENAI_API_KEY=...
npm start -- "Write fizzbuzz.mjs. It prints FizzBuzz for the numbers 1 to 100."

pi2 works in a copy of this repository and writes no files here. pi2 uses the first model that has credentials. To use a different model, set PI2_MODEL or --model provider/model.

Usage

pi2 "task" [--cwd DIR] [--model provider/model] [--improver-model provider/model]
           [--thinking LEVEL] [--harness PATH] [--k N] [--mode parallel|sequential]
           [--workers N] [--domain NAME] [--state-dir DIR] [--timeout SECONDS]
pi2 --resume RUN_DIR [--workers N] [--timeout SECONDS]

To see the default values, run pi2 --help.

pi2 keeps its state in ~/.pi2/. pi2 does not apply results to your original workspace. To continue a run that stopped, use --resume.

--harness accepts a Markdown system prompt or a directory:

systemprompt.md
guardrails.md
LongTermMEMORY.md
tool_descriptions/tool_guidance.md
sub_agents/<name>/AGENT.md
skills/<name>/SKILL.md
scripts/<name>.mjs
plugin/<name>.mjs

WARNING: Plugins and scripts run as local code with your permissions. pi2 is not a sandbox.

Development

npm test

The tests use a local deterministic model. They do not need credentials.

License

pi2 is adapted from Google's Harness² (Apache-2.0). The Pi packages are dependencies with the MIT license.