Anthropic Claude model via Reverse Proxy returns thinking error due to outdated request format

[B-ai-P]

What happened?

When using the Anthropic Claude model via a reverse proxy (URL + password method), the following error occurs:

{
"error": {
"message": "Request validation failed. At 'thinking > type': Invalid literal value, expected "enabled" | At 'thinking > budget_tokens': Required",
"type": "proxy_validation_error"
}
}

This does not happen when using an official API key connection directly to the model provider (e.g., Anthropic API), because the request format and parameters are kept up to date with the latest API specifications.

However, when using a reverse proxy, it seems that the proxy service has not been updated for a long time — possibly due to low user — and is still using an outdated request format/parameter structure.

Although I have not verified with other models, I suspect that reverse proxy connections for other models might also be outdated in the same way.

Please consider updating all reverse proxy endpoints to match the latest API changes and avoid these request validation errors.

Version Information

Environment: Running from Docker with custom CONFIG_PATH

Base image: ghcr.io/danny-avila/librechat-dev:latest
Pulled on: 2025-08-10

CONFIG_PATH:
https://raw.githubusercontent.com/LibreChat-AI/librechat-config-yaml/main/librechat-up-l.yaml

Steps to Reproduce

1. Configure LibreChat to use the Anthropic Claude model via a reverse proxy (URL + password authentication).
2. Send any request to the model.
3. Observe the thinking error in the response.
4. Switch the same configuration to official API key mode and note that the error does not occur.

What browsers are you seeing the problem on?

Chrome

Relevant log output

{
  "error": {
    "message": "Request validation failed. At 'thinking > type': Invalid literal value, expected \"enabled\" | At 'thinking > budget_tokens': Required",
    "type": "proxy_validation_error"
  }
}

Screenshots

Code of Conduct

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[danny-avila]

Anthropic API payloads remain the same whether or not a reverse proxy is used. Official implementation is still expected if using a reverse proxy.