Changelog

The API limits reference now lists the per-plan rate limits (sustained requests per second, plus a burst allowance on Agents) and concurrency limits (simultaneous in-flight requests) for every plan, across both the audio (TTS) and Agents surfaces. Limits apply per account, not per API key.

429 Too Many Requests responses are now self-describing:

• A Retry-After header tells you when to retry.
• The error code distinguishes the two cases: rate_limited (too many requests per second) versus concurrency_limited (too many simultaneous requests).
• The error envelope carries a docs_url that links straight to the limits reference, which lists your plan’s limits and how to raise them.

Rate and concurrency limits rise with your plan, and Enterprise limits are starting points rather than hard caps.