ThinHarness

Most agent frameworks want to own your whole stack. ThinHarness owns just the agent loop. It's a minimal, opinionated Python harness for purpose-built agents: scoped file tools, structured output, retries, approvals, subagents, parallel LLM calls, skills, MCP, limits, streaming, and tracing. Orchestration, auth, storage, and deployment stay with your app. Under 8k LOC; small enough to fork. Pre-1.0, MIT licensed, Python 3.11+. Free and open source.