Why

Open source, top to bottom.

jsclaw's default container runs the proprietary Claude Code harness — 238 MB you can't read. agent-micro speaks the same container contract with code you can audit before your coffee cools.

	agent-micro	default runner
Agent harness	~50 kB of plain JS, AGPL	Claude Code — proprietary, 238 MB
npm dependencies	0	claude-code, MCP SDK, cron-parser
Container image	~150 MB	~1.5 GB
Auditable	✓ every line	partially
Container contract	✓ identical	✓
MCP passthrough · subscription auth	not yet · API key only	✓

Inside

Six files. The whole stack.

Built entirely on the Node standard library. The container is the sandbox; the loop is just a REPL with hands.

Drop-in contract

runner.js reads ContainerInput on stdin and writes sentinel-delimited output on stdout. Identity files, memory/*.md, IPC polling — identical to the default runner. Swap with one config line.

Fetch, nothing else

api.js speaks the Anthropic Messages API in ~80 lines: retries with backoff, prompt caching via cache_control, and ANTHROPIC_BASE_URL for proxies and alternative providers.

The agent loop

loop.js: send, execute tool calls, append results, repeat until the model stops. Context trimming keeps long sessions under the window.

Six core tools

bash, read_file, write_file, edit_file, glob, grep — unrestricted inside the container, because the container is the boundary.

IPC without MCP

send_message, schedule_task and friends as plain in-process functions writing atomic JSON files the host watcher picks up. No transport, no SDK.

Sessions are JSON

A session is the raw messages array on disk. Resume is a file read. No daemon, no database, nothing to migrate.

Quick start

One build, one config line.

Build the image and point jsclaw at it — or run the runner bare on your machine for development. No npm install in sight.

agent-micro — zsh

$ git clone https://github.com/jsclaw/agent-micro && cd agent-micro
$ docker build -t jsclaw-agent-micro:latest -f container/Dockerfile .
$ npx jsclaw config set containerImage jsclaw-agent-micro:latest

# or standalone, no container:
$ export ANTHROPIC_API_KEY=sk-ant-…
$ echo '{"prompt": "list the files here"}' | node runner.js

---JSCLAW_OUTPUT_START---
{"status":"success","result":"…","newSessionId":"…"}
---JSCLAW_OUTPUT_END---

Status: experimental. The loop, tools, sessions, and jsclaw IPC integration work and are tested; external MCP servers and web tools are on the roadmap. Bring an API key — subscription auth needs Claude Code.

The agent runner you
can read in one sitting.