Edit a draft or scheduled campaign
Authorizations
A secret API key. Publishable keys cannot reach this API. A key may carry an expiry, and an expired key is refused exactly like an unknown one, with a 401 that names no reason; check the key's expires_at in the dashboard rather than inferring it from a response. When a merchant rolls a key's secret they choose a grace window of up to 3 days, and for its duration BOTH the new secret and the one it replaced authenticate, so an integration moves over on its own deploy schedule instead of at the instant the button is pressed. Move before the window closes: after it, the old secret is refused. Nothing else about this contract moves with a roll. The key keeps its id and its scopes, so the only thing an integration updates is the credential itself.
Headers
A unique key per logical write. Replaying a request with the same key returns the first response byte for byte instead of applying the write twice.
Path Parameters
Body
Every field is optional and an omitted one keeps its stored value, which is why this is a PATCH: sending the whole resource would let an omitted subject and body blank the campaign, and it would then go out empty to everyone in the segment. CONTENT IS FROZEN ONCE A SEND STARTS. Only a draft or scheduled campaign is editable; anything else is 409 invalid_transition, so a half-sent campaign cannot carry two different bodies.
Still unique per store; a clash is 409 name_taken.
email, sms, push Moving the audience. Re-validated against the store, so a segment deleted since this campaign was authored is 400 segment_not_found.
THE ONLY KEY ON THIS BODY THAT MAY BE SENT AS NULL, and null CLEARS it: the campaign stops rendering the stored template and falls back to its own subject and body. Omitting the key leaves it alone. Every other field refuses null, because for them a null is a misspelling rather than an intent.
Response
Success
