gemini-cli - 💡(How to fix) Fix Regression: GOOGLE_API_KEY + GOOGLE_GEMINI_BASE_URL rejected with "Invalid auth method selected" in 0.44.x (worked in 0.43.0)

Description

Setting GOOGLE_API_KEY + GOOGLE_GEMINI_BASE_URL + GOOGLE_GENAI_USE_VERTEXAI=false to route gemini-cli through a custom proxy endpoint produces Invalid auth method selected (exit 41) in 0.44.0 and 0.44.1. This worked correctly in 0.43.0.

Steps to reproduce

# Install 0.44.0 or 0.44.1
npm install -g @google/[email protected]

# Set env vars to route through a local proxy
export GOOGLE_API_KEY=proxy-token
export GOOGLE_GEMINI_BASE_URL=http://127.0.0.1:8080
export GOOGLE_GENAI_USE_VERTEXAI=false
export GOOGLE_CLOUD_PROJECT=
export GOOGLE_CLOUD_LOCATION=

# Run in non-interactive mode
gemini --prompt "Hello world" --yolo

Result: Invalid auth method selected. (exit code 41)

Expected: gemini-cli should accept the API key and send requests to GOOGLE_GEMINI_BASE_URL.

What works

• 0.43.0: Same env vars work correctly — gemini-cli accepts the key and routes through the custom base URL
• 0.44.x with real AIza... keys: If GOOGLE_API_KEY starts with AIza, the validation passes but any non-standard key format is rejected

Environment

• gemini-cli 0.44.0 and 0.44.1
• Node.js 22.x
• Ubuntu 24.04, macOS ARM64, Windows Server 2025
• All three OS reproduce the same behavior

Context

We use GOOGLE_GEMINI_BASE_URL to route gemini-cli requests through a transport proxy for model routing (e.g., running gemini-cli against OpenAI/Azure models via a translation layer). The proxy doesn't need real Google API credentials — any token works as auth is handled by the proxy. This flow worked in 0.43.0 but broke in 0.44.0.

Workaround

Pin to 0.43.0: npm install -g @google/[email protected]