BYOK minimax_api provider cannot work with OpenAI-compatible third-party relay (X-Api-Key hardcoded) - mobile channel messages fail with 'login fail'

[tim-korso]

Environment

• MiniMax Code 3.0.60, macOS
• minimaxModelSource: minimax_api_key
• A custom provider (openai-completions + Authorization: Bearer) works fine for desktop chat and is the default model

Symptom

Messages sent from the mobile app (connected to desktop) fail with:

BYOK provider minimax_api upstream error: login fail: Please carry the API secret key in the 'X-Api-Key' field of the request header

Root cause analysis (verified against app behavior)

1. The minimax_api provider defaults to https://api.minimaxi.com/anthropic (official endpoint). The configured minimax_api.apiKey is a key for a third-party OpenAI-compatible relay.
2. parseMinimaxApiConfig only accepts apiKey and baseURL — there is no way to configure a custom auth header for the upstream.
3. The SDK's apiKeyAuth sends the key as X-Api-Key header, but the relay only accepts Authorization: Bearer (verified: X-Api-Key → 401 Missing API key; Bearer → 200 OK). The relay does expose an Anthropic-compatible endpoint (/v1/messages).
4. In the same turn, custom_provider:minimax-2 (openai-completions, Bearer) succeeds while minimax_api fails — some mobile-channel requests resolve to the unprefixed builtin MiniMax model and hit minimax_api.

Expected behavior

• Allow minimax_api (or custom providers) to configure auth as Authorization: Bearer / authToken, so BYOK users with third-party relays can use them for the mobile channel.
• Or: mobile-channel auxiliary requests should use the same custom_provider model as the main conversation instead of falling back to minimax_api.

Logs

~/.minimax/v2/observability/logs/runtime-2026081123.log — entries BYOK provider minimax_api upstream error: login fail: ... at 23:40 / 23:45 / 23:47