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[Bug] Error when using Tools/MCP with Anthropic models on Vertex AI #36
Description
Activity
Hi @aka012,
Would you mind sharing the part of your
librechat.yamlwhere you configure your Vertex AI endpoint so I can try to reproduce your error?Hi @dustinhealy
In my
librechat.yaml, I have configured thetitleModelunder thegooglesection as follows:google: titleModel: "claude-haiku-4-5"
To reproduce this issue:
-
Select the Google Anthropic model in the Agent.
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Execute a tool such as MCP or file_search.
Observation: Strangely, the error with file_search seems to occur specifically when using claude-haiku-4-5. Other models behave differently.
Reacted by Dustin Healy-
Hi @aka012,
After reviewing this with Danny, the reason for your error is because use of Anthropic models via Vertex AI is not yet implemented in LibreChat.
However, there is an open PR currently in review which will add this functionality: LibreChat-AI/LibreChat#9798.
Reacted by 장영일- added a commit that references this issue
on May 5, 2026
I am using the latest version of LibreChat with
@librechat/agents@3.0.32.I configured Vertex AI to use Anthropic models (specifically mapped as
claude-sonnet-4.5,claude-haiku-4-5, andclaude-opus-4-5). While basic chat completions function correctly without any issues, the following error occurs immediately after invoking Tools (e.g.,file_search) or using MCP (Model Context Protocol).Something went wrong. Here's the specific error message we encountered: An error occurred while processing the request: {"type":"error","error":{"type":"invalid_request_error","message":"messages: text content blocks must be non-empty"},"request_id":"req_vrtx_011CVUBrrdYh8CvbYcAFXMLQ"}server logs
{"attemptNumber":1,"cause":{"code":400,"message":"{\"type\":\"error\",\"error\":{\"type\":\"invalid_request_error\",\"message\":\"messages: text content blocks must be non-empty\"},\"request_id\":\"req_vrtx_011CVUCCef2Vy7pvbkXwYXtX\"}","status":"Bad Request"},"code":400,"config":{"body":"{\"anthropic_version\":\"vertex-2023-10-16\",\"messages\":[{\"role\":\"user\",\"content\":[{\"type\":\"text\",\"text\":\"file content plz\"}]},{\"role\":\"assistant\",\"content\":[{\"type\":\"text\",\"text\":\"\"},{\"type\":\"text\",\"text\":\"I\"},{\"type\":\"text\",\"text\":\"'\"},{\"type\":\"text\",\"text\"...","duplex":"half","headers":{},"method":"POST","responseType":"stream","url":{}},"level":"error","message":"[api/server/controllers/agents/client.js #sendCompletion] Operation abortedCould you please look into this? Any help would be appreciated.