Harnesses
A harness is the worker runtime Firstmate uses to run an agent session.
Different harnesses have different strengths, limits, authentication models, and supervision behavior.
Harness philosophy
Use the harness as a tool, not as the architecture. Firstmate keeps the operating contract stable while the underlying runtime can vary.
Good harness selection considers:
- task complexity
- model capability
- available quota
- authentication state
- required tool access
- reliability for the specific job
Practical rule
Do not pick a harness because it is fashionable. Pick the smallest reliable runtime that can complete the task safely.
What Firstmate standardizes
Firstmate standardizes the lifecycle around the harness:
- spawn
- trust handling
- steering
- interruption
- recovery
- status interpretation
- cleanup
Related pages: Scripts, Task lifecycle.