Gemini CLI Relay Setup: Fix Auth and Endpoint Errors
Can Gemini CLI connect through a unified relay?
Yes, but only when the relay supports the API protocol Gemini CLI actually uses. A shared API address does not automatically make every AI client compatible. The most important troubleshooting step is checking protocol support before changing credentials or reinstalling the CLI.
59API provides low-cost, pay-as-you-go access to Claude and GPT models at https://api.59api.com, with compatibility for Claude Code, Codex, and OpenAI SDKs. Those capabilities do not, by themselves, establish Gemini CLI compatibility. Confirm that 59API currently offers a Gemini-native endpoint and suitable model routes before attempting this setup.
1. Check the relay’s compatibility first
Ask the relay provider these questions:
- Does the service accept Gemini-native generateContent and streamGenerateContent requests, rather than only OpenAI-compatible requests?
- What exact base URL, model identifier, and authentication header should Gemini clients use?
- Are streaming responses, function calling, and the tool workflows needed by Gemini CLI supported?
An OpenAI-compatible chat endpoint is not interchangeable with Gemini’s API. Likewise, access to Claude or GPT does not mean Gemini CLI can call those models directly. That requires an explicitly supported translation layer, including tool and response conversion.
2. Install and test Gemini CLI locally
Check the current package’s Node.js requirements with npm view @google/gemini-cli engines, then install a supported Node.js version. Install the CLI using npm install -g @google/gemini-cli and confirm installation with gemini --version.
Where practical, first test Gemini CLI against Google’s service with a Google-issued Gemini API key. This separates local installation problems from relay routing problems. A Google key and a relay-issued key are different credentials; do not assume either works on the other service.
3. Configure a custom endpoint only when supported
For Gemini CLI releases that support the custom endpoint override, the relevant environment variable is GOOGLE_GEMINI_BASE_URL. Check your installed release’s documentation before relying on it. For a macOS or Linux shell, export GEMINI_API_KEY with the relay-issued credential and GOOGLE_GEMINI_BASE_URL with the provider-confirmed Gemini base URL.
Do not blindly use https://api.59api.com/v1. That path may serve an OpenAI-compatible API rather than Gemini’s protocol. Also, do not append /v1beta unless the provider’s instructions require it; client libraries can add their own API-version paths.
Launch gemini and select Gemini API-key authentication if prompted, rather than Google account login or Vertex AI. Then test a provider-confirmed model with gemini -m MODEL_ID -p 'Reply with OK.', replacing MODEL_ID with the actual supported identifier.
4. Diagnose errors by their symptoms
- 401 or 403: Check for an expired key, incorrect authentication mode, missing model permissions, or a provider-specific header requirement.
- 404: Verify the full request path and model ID. A duplicated version prefix or an OpenAI-only route can cause this.
- 400 or unsupported field: The relay may reject Gemini request fields, tool declarations, or generation settings. Preserve the error message and request ID for support.
- 429: Check account balance, request limits, concurrency, and retry instructions. Repeated immediate retries can worsen throttling.
- Requests hang: Investigate streaming support, proxy buffering, and network timeouts. A successful non-streaming request does not prove streaming works.
FAQ: What should a successful compatibility test show?
A Gemini-native response normally contains a candidates structure, not an OpenAI-style choices structure. Test a simple prompt, a longer streamed response, and a harmless tool workflow separately. Passing the first test does not guarantee full CLI compatibility.
FAQ: Is 59API still useful without confirmed Gemini support?
Yes. For Claude Code, Codex, and OpenAI SDK workflows, 59API offers a unified, pay-as-you-go option positioned among the cheapest relays. Its native, official-quality models are offered without downgrading; compare current model rates, token charges, and your actual workload rather than assuming every request costs the same.
If those supported workflows fit your needs, consider signing up for 59API and checking its current pricing and referral rebate terms. Keep credentials outside repositories, use separate development keys where available, and never include secrets in troubleshooting logs.