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Heads upKlaviyo · API & integrations · Wed, Jul 15, 2026
Klaviyo API 2026-07-15: Custom Objects GA, plus a breaking change to profile conversations
What changed
The 2026-07-15 revision made the Custom Objects API generally available, added a backfill flag to record historical events without triggering flows, and made a profile's conversations plural and multi-channel (SMS, WhatsApp, Instagram), which breaks code that reads the old singular conversation relationship.
What to do
Use the backfill flag for migrations so you don't re-fire flows, and have SMS integrations updated before adopting the revision.
Source
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