topic Error 400 when creating multiple timeline event throught the batch API in APIs & Integrations

Error 400 when creating multiple timeline event throught the batch API

yoLotus — Fri, 03 Oct 2025 16:12:43 GMT

Hello,

I've encountered an error 400 when using the timeline event batch API, and the error message reported that it was due to one item in the batch.

I'm trying to get if 1 item one error prevents all others items in the batch from being processed. I see nothing related to batch error handling in the doc.

Here's the error I got:


[400]: {"status":"error","message":"There was an issue creating the timeline event: com.hubspot.contactsapi.exceptions.ContactExistsException: Contact already exists. Existing ID: <contact_id>","correlationId":"<correlationID>","context":{"errorDetails":["com.hubspot.contactsapi.exceptions.ContactExistsException: Contact already exists. Existing ID: <contact_id>"]},"category":"VALIDATION_ERROR","subCategory":"TimelineEventErrors.UPSERT_ERROR"}

Re: Error 400 when creating multiple timeline event throught the batch API

STierney — Fri, 03 Oct 2025 18:11:18 GMT

Hey @yoLotus - thanks for posting in the Community!

I'd like to tag in some experts here to see if they have any insight for us! @stefen, @ChrisoKlepke, @BarryGrennan - any idea what may be causing this error?

Shane, Senior Community Moderator

Re: Error 400 when creating multiple timeline event throught the batch API

yoLotus — Sat, 04 Oct 2025 10:55:59 GMT

Hello @STierney , thanks a lot to involve some expert in the loop 🙏

The error itself is not really an issue actually, I'd like to understand if other items of the batch (with no errors) have been successfully processed by Hubspot.

Re: Error 400 when creating multiple timeline event throught the batch API

yoLotus — Mon, 06 Oct 2025 15:30:44 GMT

I've got my answer from Hubspot Developer and the whole batched will be dismissed if one item fails.