broadcast.* events

A broadcast finished sending, carrying the delivered and failed tallies.

When this fires

Every recipient in a broadcast has been attempted and the send is over. The payload carries what actually happened.

sent means the platform accepted the message, not that a human read it. There is no read receipt, and a delivered message sitting in a muted chat counts as sent.

Reading the failure count

A steady trickle of failures is normal and not actionable: the overwhelming majority are members who blocked the bot or deleted their account on the platform. Those are permanent; the sender detects them and stops retrying that recipient rather than burning attempts.

What is worth alerting on is a sudden change in the ratio. failed climbing from ~2% to ~40% between two broadcasts usually means the bot's credentials were revoked or the bot was removed from the project's resources, not that forty percent of an audience left at once.

sent + failed can be lower than the recipient_estimate reported by broadcast.queued: a recipient with no chat row is skipped without counting as either.

Caveats

  • Fires once per broadcast, at the end. A broadcast the platform rate-limits heavily can take minutes to finish; there is no progress event in between.
  • If the sending job is released and retried after a long rate-limit, the tallies count the completed run only.
  • A broadcast aborted before sending (no connected bot, an unknown audience, an empty body after sanitisation, or an audience the plan no longer includes) emits neither this nor broadcast.queued. Nothing was sent, so nothing is announced. The REST API refuses those cases up front with a 422 rather than accepting a send that will never leave.

Related events

  • broadcast.queued: the start, with the recipient estimate.
postWebhookbroadcast.completed

Headers

SB-Signaturestring required

t=<unix seconds>,v1=<hex>: the HMAC-SHA256 of "<t>.<raw body>" under the endpoint's secret. Verify it before acting, and refuse a t more than 300 seconds from now. During a secret rotation a v0= signature under the previous secret may precede v1=.

SB-Event-Idstring required

The event's ULID, bare. The envelope's id is the same ULID prefixed evt_, so strip the prefix before comparing. Deduplicate on it: a retry carries the same id.

SB-Event-Namestring required

The event name, the same as the envelope's type.

Content-Typestring required

Always application/json.

User-Agentstring required

Always Subscriby-Webhooks/1.0.

Payload

idstring required

A ULID unique to the event, prefixed evt_. Every retry carries the same id, so it is the key to deduplicate on.

type'broadcast.completed' required

The event name, always broadcast.completed here.

created_atstring date-time required

When the event was emitted, server time, ISO 8601.

api_versionstring required

The contract version of the payload shape, 2026-05-01 today. A breaking change to a shape ships under a new version.

project_idstring uuid nullable required

The project the event belongs to; null for team-scoped and billing events.

Response

Your endpoint acknowledged the delivery. Any 2xx status within 30 seconds marks it delivered; the response body is ignored.

Changes

Webhooks have no change history: a webhook is keyed by its event name rather than a path and method, so no recorded change can name it.