Disclosure: I'm Mohammed, founder of MemorySync. I drafted this page with AI assistance and checked it against the source issue and the MemorySync n8n guide. I didn't run any code on this page.
The question
In n8n-io/n8n#33161, a self-hosted user (n8n 2.27.4) runs an AI Agent with Anthropic as the main model and Google Gemini as the fallback. When Gemini answers, the reply is stored in the Postgres Chat Memory table with type: "user" instead of type: "ai". On the next message in that session, LangChain's mapStoredMessageToChatMessage throws Got unexpected type: user and the agent fails.
Status (checked 2026-10-28 via the GitHub API): open, 2 visible comments, last updated Jul 8, 2026. n8n's bot logged it internally (GHC-8825). One community comment suggests fixing it at the serialization boundary in n8n's Postgres Chat Memory node, before the message is written. No fix is linked in the issue yet.
What you can do now
These are workarounds, not an official fix. None of this was run for this page.
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Find the bad rows. In the chat memory table your Postgres Chat Memory node writes to, look for rows in the affected session whose stored message has
typeset touser. The error only fires for sessions that contain one. - Unblock a stuck session. Deleting or correcting those rows (back up first) lets the session load again. Changing the session ID also works, but the user loses that history.
- Stop new bad writes. Until the issue is fixed, avoid running Gemini as the fallback model on an agent that writes to Postgres Chat Memory, or use the same provider for primary and fallback.
- Follow the issue for a fix before upgrading or removing the workaround.
Where MemorySync fits
Mostly it doesn't: this is a serialization bug in one memory node, and switching backends is a big change to dodge it. If you were already planning to move agent memory out of your own Postgres, the MemorySync n8n guide documents a MemorySync Chat Memory sub-node for the AI Agent's Memory port that keeps the conversation history in MemorySync. The node package is memorysyncio/n8n-nodes-memorysync. I haven't tested it with a Gemini fallback, so don't treat it as a confirmed fix for this error. It's also self-hosted only for now (n8n Cloud verification is in progress).
Next step
Read the MemorySync n8n guide. To see save and recall in your browser first, try the MemorySync playground.
Sources
- n8n-io/n8n#33161, "Postgres Chat Memory: Gemini fallback writes 'user' type messages causing 'Got unexpected type: user' deserialization error" (read 2026-10-28)
- MemorySync n8n guide: docs.memorysync.io/guides/n8n
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