Gemini CLI with API429: Gemini API key mode and Google GenerateContent

Verify Node.js prerequisites and the pinned CLI package

Check your local runtime against the official Gemini CLI installation requirements before installing the package: the inspected build requires Node.js 20 or newer. On the review date, @google/gemini-cli@0.65.0 was observed in npm while the published changelog page showed release 0.64.0 dated October 13. Those version numbers record inspected package metadata and documentation rather than a live execution claim across every operating system.

The installation example pins @google/gemini-cli@0.65.0 explicitly instead of pulling an unpinned latest tag, so future CLI changes do not silently alter environment variable names or authentication prompts. After installing, run gemini --version in a clean terminal to confirm which binary is on your PATH before you export any connection settings.

Reconcile authentication docs with the Code Assist transition

When reviewing official Google documentation, keep two dated facts in view. On May 19, 2026, Google announced the transition from Gemini CLI toward Antigravity CLI, stating that consumer free, Pro and Ultra Code Assist requests in Gemini CLI end on June 18, 2026. At the same time, the Gemini CLI authentication page continues to list Google sign-in alongside Use Gemini API key and Vertex AI.

Do not misread that May 19, 2026 consumer Code Assist notice as a blanket shutdown of every paid API-key or enterprise path, and do not assume that consumer login plans apply to a custom gateway. This guide covers only the paid API-key path selected via Use Gemini API key, which corresponds to the gemini-api-key connection mode. It does not claim compatibility with Antigravity CLI, which would require its own verified connection contract.

Set the Google origin, v1beta version and hidden key

In your current Bash session, export GEMINI_MODEL=gemini-3.8-flash, GOOGLE_GEMINI_BASE_URL=https://gateway.api429.com and GOOGLE_GENAI_API_VERSION=v1beta. Note that GOOGLE_GEMINI_BASE_URL must be the gateway origin without a trailing /v1 path segment. Collect GEMINI_API_KEY using hidden terminal input via read -r -s so the key never appears in shell history or process arguments, and unset all four environment variables as soon as you exit the client.

When Gemini CLI prompts for an authentication method, choose Use Gemini API key (gemini-api-key). Google OAuth login and Vertex AI use different credential flows and are not interchangeable with an API429 key. If you previously used Gemini CLI on the same machine, inspect your user settings first so a persisted sign-in mode does not override the API-key selection, and never overwrite credentials belonging to other workspaces.

Distinguish native GenerateContent from other CLI protocols

Gemini CLI requires native Google paths such as /v1beta/models/{model}:generateContent, :streamGenerateContent and :countTokens with x-goog-api-key authentication. The canonical API429 public OpenAPI checked on October 25 does not enumerate these generateContent, streaming or token-counting methods, their /gemini aliases, or this authentication header. These client settings describe a candidate configuration, not verified gateway support. Before launching, obtain a current documented contract for the exact native methods and authentication required by your installed CLI. Schema omission leaves support unconfirmed; a model catalog entry does not resolve it.

Keep this contract separate from other terminal coding tools. Gemini CLI calls /v1beta/models/{model}:generateContent with x-goog-api-key, Codex CLI calls OpenAI POST /v1/responses with Bearer authentication, and Claude Code CLI calls Anthropic POST /v1/messages with x-api-key (/en/integrations/claude-code). A working OpenAI Compatible configuration in an editor or another CLI cannot be transferred to Gemini CLI simply by changing the model name.

Run a disposable check and separate agent tools from token billing

Before starting the interactive CLI, confirm that gemini-3.8-flash appears in an authenticated GET /v1/models check for your key; a public catalog listing alone does not guarantee access for every credential. Launch gemini inside an empty test folder and send one short nonconfidential question. If you encounter a 404 or 401 error, inspect the origin URL, v1beta setting and selected authentication mode using redacted error output rather than retrying in a loop.

Even a separately documented native method would not prove that every Gemini CLI agent feature works end to end. Native CLI execution, MCP servers, local tool loops and sandbox modes were not run for this guide. Confirm generateContent, streamGenerateContent and countTokens support for your exact connection before relying on these settings. Token counting is not a hard spending limit: context assembly, follow-up turns and repeated commands can consume billed tokens.

Check Node.js and install the pinned CLI version

node --version
npm install -g @google/gemini-cli@0.65.0
gemini --version

Bash: Google API environment variables and manual API key session

read -r -s -p "API429 key: " GEMINI_API_KEY
printf "\n"
export GEMINI_API_KEY
export GEMINI_MODEL=gemini-3.8-flash
export GOOGLE_GEMINI_BASE_URL=https://gateway.api429.com
export GOOGLE_GENAI_API_VERSION=v1beta
gemini
unset GEMINI_API_KEY GEMINI_MODEL GOOGLE_GEMINI_BASE_URL GOOGLE_GENAI_API_VERSION

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