Pioneer Coding Agent

A tiny (~180-line), zero-dependency agentic coding agent that runs on any Anthropic-compatible /v1/messages API. Built for Pioneer, works with the Anthropic API too.

Drop it in a repo, give it a task, and it reads files, edits them, runs your build/tests, and reports what it changed — all from one small file you can read in five minutes. No framework, no install, no lock-in.

export PIONEER_API_KEY=pio_sk_...your_key...
node pioneer-agent.mjs "add a GET /api/health route that returns { ok: true }"

Why

Most coding agents are heavy frameworks. This is the opposite: one file, raw fetch, the standard Anthropic tool-use loop. Use it to:

• Run agentic coding against a cheaper or alternative Anthropic-compatible endpoint (Pioneer, a self-hosted gateway, etc.) instead of your primary one.
• Drive headless code-gen on a server or in CI with zero dependencies.
• Read and understand a complete agent loop without wading through a framework.

Requirements

• Node 20+ (uses the built-in global fetch). No npm install needed.

Setup

Env var	Required	Default	Notes
PIONEER_API_KEY	yes	—	Sent as the X-API-Key header.
PIONEER_BASE_URL	no	https://api.pioneer.ai/v1	Use https://api.anthropic.com/v1 for Anthropic.
PIONEER_MODEL	no	claude-sonnet-4-6	Any model your endpoint serves.

Usage

Run it from the root of the repo you want it to work on:

node pioneer-agent.mjs "your task in plain English"

Optional convenience wrapper:

# /usr/local/bin/pio
#!/usr/bin/env bash
set -a; source ~/.pioneer-env; set +a   # a file holding your env exports (gitignored!)
node /path/to/pioneer-agent.mjs "$@"

pio "refactor lib/date.ts to use Intl.DateTimeFormat and update the tests"

What it does

The agent has four tools, all confined to the current working directory:

• list_dir — list a directory
• read_file — read a file
• write_file — create/overwrite a file (full content)
• run_bash — run a shell command (build, test, grep, git diff, …)

It runs the standard tool-use loop until the model finishes, then prints the files it changed and the token usage.

Safety

• File ops are confined to the working directory (paths that escape are rejected).
• run_bash executes arbitrary shell commands. Run this in a repo/VM you trust, ideally a sandbox or container. Treat it like letting a contributor run a script.
• It never commits or pushes. Review the diff (git diff) and commit yourself.
• Never commit your API key. Keep it in an env var or a gitignored env file.

License

MIT — see LICENSE. Contributions welcome.