What does 400 bad_request mean when creating a run?

TroubleshootingUpdated November 2, 2026

400 bad_request on POST /v1/runs usually means:

input is missing (or the body isn't valid JSON, so it can't be read). Send Content-Type: application/json.
tier is invalid: use auto, flash, max or heavy.

The message says which field is wrong. Fix it and send again; nothing was started.

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