Concepts

This is the documentation for unreleased changes on main. For the released library, read v0.1.

Psych's words have exact meanings and no synonyms. Two pages carry them.

• Vocabulary: Spec, Version, Run, Record, Step, Turn, Agent, Workflow, Tool, Skill, Subagent, Scope, Port, Attempt, Lease. The three people get wrong are here too: a Version is an immutable content-hashed publication of a Spec, an Attempt is one execution pass by one Worker holding a lease, and a Record is one sequenced entry in a Run's log rather than a log line.
• Invariants: the rules a change is rejected for breaking. A Spec holds tool names and never a callable. MCP clients pool by (scope, server, credential) and never by URL. The reducer is pure. A model with no known price records cost=None, never 0. A Spec is validated at publish, never at run.

Both are worth reading once before writing code against the library, because neither is guessable from the shape of the API.