Cycles is a runtime authority for autonomous AI agents and workflows that enforces hard, pre-execution limits on spend, risk, and actions using a reserve-commit lifecycle: SDKs estimate and reserve budget for LLM calls or tool invocations, allow or deny actions (or apply caps like max tokens or tool denylists), then commit actual usage and release unused amounts. Use it to prevent runaway agent costs, isolate per-tenant API budgets, ensure deterministic, auditable policy decisions across providers (OpenAI, Anthropic, Bedrock, LangChain, etc.), and safely deploy autonomous AI systems with predictable cost and compliance controls.