> For the complete documentation index, see [llms.txt](https://docs.tryterra.co/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.tryterra.co/faq/help-topics/data-api-sdk/webhooks-dedup-and-sync-reliability/additive-schema-new-fields-parser.md).

# Why did new payload fields break my parser?

New fields can appear in payloads as part of **normalised-schema updates**. These additive changes are treated as backward-compatible and may not be announced in advance, since the wire format is kept additive-only. They arrive with `null` values where not yet computed.

* **Configure your deserializer to allow (ignore) unknown fields** rather than reject the whole payload.
* Rely on the [webhook signature](https://docs.tryterra.co/health-and-fitness-api/managing-user-health-data/receiving-data-updates) to authenticate that the payload came from Terra.

New fields are also reflected on the [docs changelog](https://docs.tryterra.co/changelog/2025/readme).