API Changelog

API Changelog

Every change to the SIPSTACK API is recorded here, newest first. Entries are dated with the API’s version scheme (YYYY-MM-DD). Deprecations list the replacement and the cool-down window during which the old and new surfaces run concurrently — see Versioning → Deprecation Policy.

How to read this page

• Added — new endpoints, fields, scopes, or events. Additive and non-breaking; safe to ignore until you need them.
• Changed — behavior changes to an existing surface.
• Deprecated — surfaces scheduled for removal, with their replacement and cool-down window.
• Removed — surfaces taken out after their cool-down window elapsed.

New entries are prepended above, so the top of the page is always the latest version.

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2026-09-XX

SMS send limits on the messaging API, and one delivery-rate definition for Flare campaigns.

Added

• delivery_stats on Flare campaign list rows and deliveryStats on the campaign detail — attempted, delivered, failed, undelivered, failed_total, awaiting, no_receipt, delivery_rate, failure_rate and provisional (camelCase on the detail). The delivery rate is delivered ÷ attempted, where attempted = delivered + failed + undelivered + messages still waiting for a carrier receipt; queued and cancelled messages are not counted. awaiting is messages sent within the last 72 hours without a receipt (the rate is provisional while it is above 0); no_receipt is messages sent more than 72 hours ago that the carrier never confirmed. The existing messages_sent / messages_delivered / messages_failed / message_count fields are unchanged. Computing a rate as messages_delivered / messages_sent ignores failures — use delivery_rate instead.
• Campaign analytics adds attempted, awaiting, noReceipt and provisional.

Changed

• Campaign analytics deliveryRate and failureRate now use the same definition as delivery_stats, so they match the campaign list and detail.

• POST /api/v2/messages/send returns a specific status and code when a plan SMS limit refuses a send, instead of a generic 500: 429 PAID_LIMIT_REACHED (with reason and a Retry-After header), 429 TRIAL_LIMIT_REACHED, 403 CARD_NOT_VERIFIED, 402 CAPABILITY_RESTRICTED_BY_STATE, and 503 when a limit can’t be checked. See Rate Limits → Plan Message Limits.

• Segments are counted with the GSM-7 character set. Accented letters in that set (for example é, ñ, ü) no longer switch a message to 70-character Unicode segments, and € ^ { } [ ] ~ \ | each count as two characters. See how segments are counted.

2026-06-10

The baseline public API reference, grouped by product.

Added

• Public API Reference, organized by product — the Developer API documented across Nova (voice / calls, numbers, extensions, voicemails, recordings, transcriptions), Flare (SMS/MMS send and history, contacts, campaigns, contact lists), and Aura (AI voice-agent calls, agents, knowledge bases), plus account-level Numbers, API keys, and Webhooks.
• API-key authentication (x-api-key) with per-key scopes — see Authentication and API Keys.
• Pagination contract across list endpoints — offset paging (page / limit / total / totalPages) everywhere, plus keyset paging (next_cursor) on the high-volume history endpoints. See Pagination.
• Webhooks for real-time event delivery, with signed payloads and a subscribable event catalog. See Webhooks.
• Rate limits with standard RateLimit-* response headers. See Rate Limits.

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