Start a campaign

POST /campaigns/{id}/start

Validates the campaign is ready, then flips it to active and sets startedAt (on first start only, later restarts don't reset it). The workspace must not be billing-locked, and starting a draft, completed or archived campaign must fit your plan's active-campaign limit. It then runs the same checks as GET /campaigns/{id}/readiness, plus a live check that the AI provider is reachable when the copy uses {{ai_opener}}:

• At least one step exists that is a valid email step (subject + bodyText), a LinkedIn step (linkedin_connection / linkedin_message).
• Your plan includes the channel(s) the campaign actually uses.
• Your monthly campaign send limit hasn't been reached.
• At least one sending account is attached for each channel the campaign uses (email → senders, LinkedIn → linkedin-senders).
• At least one lead is queued.
• Copy checks: every merge tag exists, the campaign brief is written when the copy uses {{ai_opener}}, and the copy does not link to a Warmerly domain.

Checks marked severity: "warning" do not block, but the start is refused with 400 and error.details.needsAcknowledgement: true until you repeat the call with { "acknowledgeWarnings": true } in the JSON body.

curl -X POST https://app.warmerly.com/api/v1/campaigns/b6a1e7b0-2f2b-4b7a-8e2a-1a2b3c4d5e6f/start \
  -H "X-Api-Key: wmv_xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx"

{ "campaign": { "id": "b6a1e7b0-2f2b-4b7a-8e2a-1a2b3c4d5e6f", "status": "active", "startedAt": "2026-07-02T10:00:00.000Z", "...": "..." } }

Failing a readiness check returns 400 bad_request with a human-readable message (e.g. "Add at least one sending mailbox") and the checks in error.details.checks. Missing plan access returns 403 channel_not_included; hitting the monthly send cap returns 402 payment_required. Hitting your plan's active-campaign limit returns 402 plan_capacity, a billing-locked workspace returns 402 billing_locked, and a campaign whose only senders are not allowed to send campaigns at all (for example a free mailbox while sending from free mailboxes is switched off) returns 409 with code sender_cannot_send_campaigns.