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HTTP 501 · type api_error. The route you called is part of the published contract but has not shipped yet — it is marked x-fn-status: planned in the API reference. Nothing about your account, key, or resource is wrong; the surface simply isn’t live. Retrying won’t help; the changelog announces when planned surfaces ship.

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The shape

Distinguishing “not shipped” from “wrong id”: planned routes answer 501 not_implemented with the surface named in the error, while a genuinely unknown resource answers 404 not_found. If you see a 501, the route is marked x-fn-status: planned in the reference and simply has not shipped yet — your account is not missing a feature flag. The planned surfaces today: discover, extractions (single and batch), monitors, session/extraction refresh, redaction (DELETE), GET /v1/receipts/{id}, webhook test deliveries and redelivery, and /mcp.

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How to fix

  • Check the API reference — if the operation is marked x-fn-status: planned, build against the live surface instead (sessions cover most workflows today) and watch the changelog.
  • If the route is not marked planned and you get this (or a 404 you can’t explain), check the HTTP verb — a wrong method on a known path currently returns 404 as well — then include request_id in a support message.