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A Signal segment is a named, static group of contacts in one project. Membership changes only when a dashboard operator or API caller adds or removes a contact.

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What a segment contains

The segment record exposes its seg_… ID, name, project ID, contact count, unsubscribed count, and creation time. The contacts endpoint lists current members with cursor pagination. A segment does not store a property rule and does not continuously recalculate membership. If your application needs rule-driven grouping, calculate that rule in your own system and synchronize explicit membership changes.

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Membership operations

  • Create the segment with a name.
  • Add an existing contact through the contact-segment membership endpoint.
  • Remove a membership without deleting the contact.
  • List current contacts before using the group operationally.
  • Delete the segment only after callers stop referencing its ID.
Deleting a segment removes the grouping. It does not delete its contacts, properties, or topic preferences.

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Sending to a segment

Put one seg_… ID in to. It must be the only recipient and cannot be combined with cc or bcc. Signal resolves the current members and creates one independent message per resolved address. One audience request supports at most 50 resolved recipients. An audience larger than 50 is rejected rather than truncated. Suppression checks still apply before provider delivery.

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What membership does not prove

Segment membership is not a consent state. A member can have an explicit topic opt-out, global unsubscribe state, or suppression entry. Your sending workflow must select the correct audience boundary and honor the separate delivery fence.

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Pre-send checklist

  1. Retrieve or inspect the current membership.
  2. Confirm the group still matches the intended business population.
  3. Confirm the communication’s topic and consent requirements.
  4. Review unsubscribed and suppression state.
  5. Confirm the audience is within the 50-recipient request ceiling.
  6. Use a stable idempotency key for the logical send.
Do not assume a segment changed because a contact property changed. Only an explicit membership operation changes the segment.