Show HN: Cycles – hard limits on agent actions before execution (opens in new tab)

Rate limits control velocity. They say nothing about what an agent is allowed to do next. An agent can pass every rate-limit check and still delete 400 records, send 200 emails, or place orders before anyone notices. The damage isn't always in the bill — it's in the consequence.

Cycles is an open protocol for pre-execution enforcement. The core mechanism: reserve exposure before the action runs, commit actual usage after, release the remainder if it fails. Every reservation is idempotent so retries don't double-count.

Atomic operations mean concurrent agents can't both see "enough budget" and both proceed. It's not a rate limiter. It's not an observability tool. It's a runtime authority that answers one question before every instrumented action: is this still allowed to proceed?

Three clients: Python (PyPI), TypeScript (npm), Spring Boot (Maven Central). Self-hostable server, Apache 2.0.

Integrations: OpenClaw, LangChain, Vercel, FastAPI

The demo shows the failure mode in 60 seconds — same agent, same bug, two outcomes: without Cycles it burns $6, with Cycles it stops at $1.

Happy to answer questions about the protocol design, the idempotency semantics, or the concurrency model.