pi-green-loop

Keep the build green. An autonomous test / lint / typecheck / build feedback loop for AI coding agents. After code changes, pi-green-loop runs your project's checks and — when something is red — hands a parsed failure summary back to the agent so it fixes it, looping until green.

Built to just work and stay fast:

• Polyglot detection — Node (package.json), Python (pyproject.toml), Go (go.mod), Rust (Cargo.toml), and Makefile, out of the box. No config required.
• Affected-test scoping — runs only the tests impacted by the files that changed (vitest / jest / pytest / go), so the loop stays fast on big suites.
• Parsed failures — feeds the agent a compact list of failing test names, not a raw dump.
• Reliable loop — debounced, capped, stops when it stops improving, and skips runs when nothing changed.

One core engine, four ways to run it:

Surface	How
CLI	npx pi-green-loop check · pi-green-loop fix · pi-green-loop watch
MCP server	npx pi-green-loop mcp (use from Claude, Cursor, any MCP client)
Claude / Cursor skill	drop skills/pi-green-loop into your skills dir
pi extension	import piGreenLoop from "pi-green-loop/pi" — closed loop on the pi event bus

The core engine is dependency-free (Node built-ins only); the CLI, MCP server, and pi extension all sit on top of it.

Install into pi

pi install git:github.com/vaibhav-patel/pi-green-loop   # extension (agent_end loop + /green) and skill
# once published to npm:
pi install npm:pi-green-loop

import … from "pi-green-loop/pi" is for embedding in your own SDK app — pi users should pi install instead.

Quick start

npm install
npm run build

# what would run?
node dist/cli/index.js detect      # (or: npm run dev -- detect)

# run the checks once
node dist/cli/index.js check

How it decides what to run

1. A pi-green-loop.json (or .pi-green-loop.json) in the project root, if present, wins.

2. Otherwise it auto-detects per ecosystem (first match per kind, polyglot repos supported):

   Ecosystem	Detected from	Checks
   Node	package.json scripts	typecheck / lint / test / build (npm/pnpm/yarn/bun)
   Python	pyproject.toml etc.	pytest, ruff check ., mypy .
   Go	go.mod	go test ./..., go vet ./..., golangci-lint run, go build ./...
   Rust	Cargo.toml	cargo test, cargo clippy, cargo check, cargo build
   Make	Makefile	make <test|lint|build> (lowest priority)

Generate a starter config (add --ci to also write a GitHub Actions workflow):

node dist/cli/index.js init --ci

// pi-green-loop.json
{
  "timeoutMs": 300000,
  "checks": [
    { "name": "typecheck", "kind": "typecheck", "command": "npm run typecheck" },
    { "name": "test",      "kind": "test",      "command": "npm test" }
  ]
}

Fast & focused

Scope a run to just the tests affected by what changed:

node dist/cli/index.js check --since HEAD~1          # tests touching files changed since a git ref
node dist/cli/index.js check --affected src/a.ts,src/b.ts

When scoping isn't possible (no git, unknown framework, empty set) it safely falls back to the full suite — it never reports a false pass by running zero tests. watch accumulates changed files and scopes each re-run automatically.

Run formatters / autofixers, then re-check:

node dist/cli/index.js fix    # prettier/eslint --fix, ruff format/--fix, gofmt, cargo fmt (only what's detected)

fix never installs anything — it only runs a tool when there's evidence it's already available (a dependency or its config file).

The loop (pi extension)

The pi adapter listens for agent_end and, once the agent is idle, runs the checks scoped to the files it just edited. On failure it injects a parsed failure summary back as a follow-up so the agent fixes it. The loop is guarded:

• Debounced — only runs when idle with no queued messages.
• Capped — at most maxAttempts (default 3) auto-fixes per interactive turn.
• Stops when stuck — if a run reproduces the exact same failures, it pauses instead of looping (/green resumes it).
• Skips redundant runs — caches the last all-green commit and skips when HEAD is unchanged and nothing was edited.
• Status gauge — a footer status plus a widget listing the currently-failing checks.

/green runs the checks now; /green on · /green off toggle the auto-fix loop.

Development

npm install
npm run build      # tsc -> dist/
npm test           # node --test suite
npm run typecheck  # tsc --noEmit

pi-green-loop checks itself: node dist/cli/index.js check runs its own typecheck + test + build.

License

MIT — see LICENSE.