Start free. Scale when you need to.

A chain is one agent execution session — opened with POST /v1/chains and closed with POST /v1/chains/:id/complete. Each chain maps to a single agent run from start to finish. Chains count against your monthly quota at the moment of creation.

A ledger entry is each append call to POST /v1/chains/:id/entries. Entries record individual agent events: tool calls, decisions, human handoffs, ingestion events, checkpoints, and errors. Every successful append increments your monthly entry quota by one.

The free tier enforces hard limits. When a quota is reached, the API returns HTTP 429 (quota_exceeded) and new chains or entries are blocked for the remainder of the calendar month. Quotas reset automatically at the start of the next month. To continue without interruption, upgrade to Pro — limits apply immediately.

Yes. Upgrading takes effect immediately — your limits increase to Pro levels the moment the plan change is applied. There is no wait for the next billing cycle, and you are not charged retroactively for usage already logged on the free tier.

Yes. The free tier is permanent. No credit card required, no trial period, no expiry date. You can prototype and run personal projects on the free tier indefinitely. 500 chains and 50,000 entries reset at the start of each calendar month.