jsclaw-agent-micro

Zero-dependency agent runner for jsclaw containers. Pure JavaScript ESM, no node_modules, talking to the Anthropic Messages API directly over fetch.

A drop-in replacement for jsclaw's default Claude Code runner: same stdin/stdout container contract, same identity files, same memory convention, same six IPC tools — in ~1,000 lines you can read in one sitting.

| | default runner (jsclaw-agent) | jsclaw-agent-micro | |--------------------|-------------------------------|--------------------------| | Agent harness | Claude Code (proprietary, 238 MB) | this repo (AGPL, ~50 kB) | | npm dependencies | claude-code, MCP SDK, cron-parser | none | | Container image | ~1.5 GB (incl. chromium) | ~150 MB | | Open source | partially | top to bottom |

Status

Experimental scaffold. The loop, tools, sessions, and jsclaw IPC integration work and are tested; it has not yet been hardened against long real-world workloads.

Usage

# Build the container
docker build -t jsclaw-agent-micro:latest -f container/Dockerfile .

# Point jsclaw at it
npx jsclaw config set containerImage jsclaw-agent-micro:latest

Or run it standalone, no container, for development:

export ANTHROPIC_API_KEY=sk-ant-...
export JSCLAW_WORKSPACE=$PWD
echo '{"prompt": "list the files here and summarize"}' | node runner.js

Output arrives as sentinel-delimited JSON on stdout (jsclaw's ContainerOutput shape):

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

What's inside

• runner.js — container entrypoint: ContainerInput on stdin, identity files (SOUL.md, IDENTITY.md, AGENTS.md, TOOLS.md, USER.md), memory/*.md loading, IPC input polling, close sentinel
• src/api.js — Anthropic Messages API over fetch: retries with backoff, prompt caching via cache_control
• src/loop.js — the agent loop: send, execute tool calls, append results, repeat; naive context trimming
• src/tools.js — bash, read_file, write_file, edit_file, glob, grep
• src/jsclaw-tools.js — jsclaw's six IPC tools (send_message, schedule_task, list_tasks, pause_task, resume_task, cancel_task) in-process — no MCP transport needed
• src/session.js — sessions are the raw messages array as JSON under .jsclaw-micro/sessions/

Environment variables

| Variable | Default | Description | |----------|---------|-------------| | ANTHROPIC_API_KEY | — | Required (or ANTHROPIC_AUTH_TOKEN) | | ANTHROPIC_BASE_URL | https://api.anthropic.com | Alternate endpoint/proxy | | JSCLAW_MICRO_MODEL | claude-sonnet-4-6 | Default model (ContainerInput model wins) | | JSCLAW_WORKSPACE | /workspace/agent | Agent workspace dir | | JSCLAW_IPC_BASE | /workspace/ipc | IPC base dir | | JSCLAW_SYSTEM_PROMPT | — | Extra system prompt | | JSCLAW_ALLOWED_TOOLS | all | JSON array of allowed tool names | | JSCLAW_MEMORY_MAX_CHARS | 8000 | Memory budget for the system prompt |

Not yet supported

• External MCP servers (ContainerInput.mcpServers is ignored with a stderr warning)
• Web search / web fetch tools
• Sub-agents
• Streaming (responses arrive per-turn, which is fine for headless use)
• Claude subscription auth — bring an API key

Development

npm test    # node --test, no network needed
npm run lint

License

AGPL-3.0-or-later. Copyright (c) 2026 Melvin Carvalho.