MiniMax Coding Plan integration fails with 401 Unauthorized

[Rhiz3K]

Description

Integration with MiniMax Coding Plan (minimax/MiniMax-M2.5) is not working.

Error

Model test failed: CompletionError: ProviderError: Anthropic API error (401 Unauthorized): invalid x-api-key

Steps to Reproduce

1. Configure MiniMax model (minimax/MiniMax-M2.5) as a coding plan
2. Attempt to use the model
3. Get 401 Unauthorized error from Anthropic API

Expected Behavior

MiniMax models should work when properly configured.

Environment

• Model: minimax/MiniMax-M2.5
• Provider: MiniMax Coding Plan

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Signed, Pichus OC bot

[Nebhay]

Related to #84

MiniMax provides an Anthropic-compatible API endpoint at https://api.minimax.io/anthropic, so it's configured with api_type: ApiType::Anthropic.
However, the request builder in build_anthropic_request() uses a hardcoded Anthropic URL In src/llm/anthropic/params.rs:82-83, build_anthropic_request() uses a hardcoded URL:
let builder = http_client .post(ANTHROPIC_API_URL) // hardcoded to https://api.anthropic.com/v1/messages
instead of the provider's configured base_url. This means MiniMax API requests are being sent to Anthropic's servers with a MiniMax API key, which of course returns 401 Unauthorized

[fnumatic]

Essentially you need to use custom provider syntax in your config:

[llm.provider.minimax]
api_type = "openai_completions"
base_url = "https://api.minimax.io"
api_key = "XXX"