ThinHarness
Build focused AI agents without framework sprawl
ThinHarness is a minimal, opinionated Python harness for purpose-built agents.
It owns the focused set of primitives that are tedious to rebuild and leaves the rest of the stack to your app.
It matches the harness-level feature coverage of frameworks 5–10× its size, so forking is a real option, not a theoretical one.
Pre-1.0, MIT licensed, Python 3.11+.
Features
- Scoped filesystem tools
- Structured output
- Tool retries
- Human approvals
- Subagents
- Parallel LLM calls
- Skills
- MCP
- Limits
- Event streaming
- OpenTelemetry tracing
Use Cases
- Information retrieval
- Customer support
- Workflow automation
Comments
I started building ThinHarness after getting tired with huge agent frameworks. I usually needed only a small slice of functionality, but that slice came with coupled assumptions that didn't match my application. I've been using it for all my agent projects recently but would love feedback from anyone building agent workflows in Python!
This is exactly what the agent ecosystem needed. So many frameworks push you into their opinionated stack, but most projects just need focused primitives - filesystem tools, structured output, retries. The fact that ThinHarness gets you 5-10x framework coverage in a tiny footprint while staying MIT licensed is huge for independent builders who don't want to get locked into ecosystem wars.
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Comments
I started building ThinHarness after getting tired with huge agent frameworks. I usually needed only a small slice of functionality, but that slice came with coupled assumptions that didn't match my application. I've been using it for all my agent projects recently but would love feedback from anyone building agent workflows in Python!
This is exactly what the agent ecosystem needed. So many frameworks push you into their opinionated stack, but most projects just need focused primitives - filesystem tools, structured output, retries. The fact that ThinHarness gets you 5-10x framework coverage in a tiny footprint while staying MIT licensed is huge for independent builders who don't want to get locked into ecosystem wars.
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