Glossary
Harness
What is a harness?
A harness is the code and setup around an AI model that turns it into a working agent: its instructions, tools, memory and context, permissions, retries, logging and checks.
Also called: Agent harness
Why it matters
The same model can perform very differently depending on its harness. In practice, much of an agent’s reliability comes from the harness rather than the model.
Example
An invoice agent’s harness gives it read-only access to the ERP, a tool to fetch purchase orders, a rule to escalate anything over $50,000, and a log of every step.
Learn more
Guide · SeeWhat is a forward-deployed engineer?What FDEs do, the playbook they follow, and how to give every person the same capability.Guide · EquipWhat is an AI agent harness? The software that turns a model into an agentThe software that turns a model into an agent: what it does, why it matters, and what to ask vendors about theirs.