Sender status

• Numbers show where they stand. Every number carries sender (test_only, pending, active, action_needed with a plain reason). New GET /v1/numbers/{number}, and the number.sender_updated event. See Numbers.
• Test only until registered. A live US number that is not linked to an approved registration can text your verified numbers and nobody else. Other sends answer 403 sender_not_registered with X-Delivered-Sender-State. This replaces the X-Delivered-Registration / X-Delivered-Warning headers, which are gone: unregistered traffic is now stopped instead of warned about.
• Automatic linking. When a registration is approved, the account's live numbers are linked to it and become active; numbers bought later link on their own. POST /v1/numbers/{number}/registration chooses a registration explicitly (up to 49 numbers each).
• One form to go live. Submitting a registration from a sandbox account is also the live-access request. Submit now requires complete business details and answers 400 naming what is missing.