# Adding new properties to request/response types of activities and determinism?

**URL:** <https://community.temporal.io/t/adding-new-properties-to-request-response-types-of-activities-and-determinism/13150>\
**Category:** Community Support\
**Created:** [August 12, 2024, 11:16pm UTC](https://community.temporal.io/t/adding-new-properties-to-request-response-types-of-activities-and-determinism/13150 "2024-08-12T23:16:29Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![pauldotknopf](https://sea2.discourse-cdn.com/flex016/user_avatar/community.temporal.io/pauldotknopf/32/5720_2.png) [@pauldotknopf](https://community.temporal.io/u/pauldotknopf)\
**Post date:** [August 12, 2024, 11:16pm UTC](https://community.temporal.io/t/adding-new-properties-to-request-response-types-of-activities-and-determinism/13150/1 "2024-08-12T23:16:29Z")

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Is it safe to add properties to request/response types to activities? Will it break validation when the history is replayed?

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**Author:** ![antonio.perez](https://sea2.discourse-cdn.com/flex016/user_avatar/community.temporal.io/antonio.perez/32/2417_2.png) [@antonio.perez](https://community.temporal.io/u/antonio.perez)\
**Post date:** [August 13, 2024, 2:50pm UTC](https://community.temporal.io/t/adding-new-properties-to-request-response-types-of-activities-and-determinism/13150/2 "2024-08-13T14:50:52Z")

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Hi @pauldotknopf

It won’t if those types are backward compatibles and the workflow code itself is [deterministic](https://docs.temporal.io/workflows#intrinsic-non-deterministic-logic), meaning that the workflow won’t take a different path during replay based on the new properties added to the returned types.

I would use [workflow replay](https://docs.temporal.io/workflows#replays) to test the changes.

The information shared in this post can be useful too [Changing WorkflowMethod param type](https://community.temporal.io/t/changing-workflowmethod-param-type/13117)

Antonio