retries

Once an agent loop runs past a few iterations the failure surface shifts: state bloats, tool calls fail in three distinct ways, retries multiply if you stack them wrong, and unbounded budgets rack up four-figure bills overnight. The state, errors, and budgets you need to make the loop survive contact with reality.

Why "the same request twice should produce the same result" is one of the most useful properties you can give an API, the standard patterns for implementing it (keys, dedupe tables, natural idempotency), and what goes wrong when you don't.