Topic · 5 posts
Model APIs & Application Surfaces
Tool use, structured output, prompt caching, durable execution, and the route handlers that sit between a model and a production system.
- 5 min
Nightly builds for a national retail chain, and why I checkpoint agent runs
Packaging POS releases where a failed rollout stopped checkout and store revenue, with a rollback path per store. The instinct that made durable execution obvious twenty years later.
- 6 min
A multi-minute agent run should not die on one transient failure
The v1 research agent lost entire runs to a single timeout. Rebuilding it on durable execution meant every unit of work checkpoints independently — and the interesting part was handling the failures that used to disappear silently.
- 5 min
How to unit-test an iteration cap without ever calling a model
The agent loop's most important safety property is that it stops. Testing that against a live API is slow, expensive and flaky — so I put one interface between the loop and the execution engine, and the test became four lines.
- 6 min
One JSON schema, three formats, no branching logic
A tabular invoice, an ASCII-art grocery receipt, and a prose billing email through one unchanging code path — and the null-safe money handling that decides whether the result is usable in a financial system.
- 5 min
One cache breakpoint cut my agent loop's input cost by 47%
An agent loop re-sends its entire prefix on every iteration. Real token counts before and after a single cache_control marker — plus the two ways to silently break it and never see an error.