Gemini 3 Flash is now available in Gemini CLI

Source: Google Developers Blog

December 17, 2025

Gemini 3 Flash now available in Gemini CLI

Gemini 3 Flash is now integrated into the Gemini CLI, enabling high‑frequency, terminal‑based workflows.

• Performance: Achieves a SWE‑bench Verified score of 78 % for agentic coding, surpassing both the 2.5 series and Gemini 3 Pro.
• Efficiency: Designed to push the Pareto frontier of quality vs. cost and speed.
• Cost: Available in preview at less than a quarter of the cost of Gemini 3 Pro.
• Speed & Quality: With two of our best models powering Gemini CLI, you no longer have to sacrifice quality for speed.

Start Using Gemini 3 Flash with Gemini CLI

Starting today, most paid‑tier customers of Gemini CLI have access to both Gemini 3 Pro and Gemini 3 Flash, including:

• All non‑business customers of Google AI Pro or AI Ultra
• Users who have access via a paid API key through Google AI or Vertex
• Gemini Code Assist users that have been enabled by their cloud admin for preview models
  (admin instructions)

For free‑tier users

• Everyone who signed up on the previous waitlist has been onboarded – check your email for details.
• If you weren’t on the waitlist, we’re rolling out additional access gradually to keep the experience fast and reliable. Stay tuned, or view our docs to learn about your current options.

Upgrade Gemini CLI

Upgrade to the latest version (0.21.1 or newer):

npm install -g @google/gemini-cli@latest

Confirm the upgrade:

gemini --version   # should show 0.21.1 or later

Enable preview features

1. Run the /settings command.
2. Toggle Preview features to true.
3. Run /model and select Gemini 3.

What’s new?

This release brings the full capabilities of the Gemini 3 family to your terminal:

• Intelligent auto‑routing: Gemini CLI automatically reserves Gemini 3 Pro for highly complex reasoning tasks.
• Manual selector: Choose a specific model for all of your tasks.
• Gemini 3 Flash: Offers significant reasoning improvements, allowing you to run prompts that previously required the slower Pro tier—at a lower cost.

Build anything in the terminal with improved agentic coding

Gemini 3 Flash raises the performance floor of your coding sessions with strong reasoning, tool use, and multimodal capabilities.

Generate a ready‑to‑deploy app with 3D graphics

We used Gemini 3 Pro in Gemini CLI to build a 3D voxel simulation of the Golden Gate Bridge, treating the prompt as both a creative brief and a technical specification. But can Gemini 3 Flash do the same?

Previously, generating this level of functional code in a single pass was a job more suited for Pro models. Gemini 2.5 Flash, for example, often struggled with this complexity, resulting in broken logic. While Gemini 3 Pro’s state‑of‑the‑art reasoning creates a more visually appealing result, Gemini 3 Flash can still handle the task with precision, demonstrating that a rapid‑prototyping tool doesn’t have to compromise code quality.

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Improve Your Daily Work

The true test of a development assistant is how it handles the high‑volume, practical tasks you execute throughout the day. Gemini 3 Flash outperforms 2.5 Pro while being 3× faster at a fraction of the cost (based on the Artificial Analysis benchmark).

Action‑Code Changes from Large Context Windows

Managing large codebases often means sifting through hundreds of comments on a pull request to find the single actionable item. This requires a model capable of holding a massive context window without losing track of specific instructions.

In this demo, Gemini 3 Flash processes a simulated pull‑request thread containing 1,000 comments. It cuts through pages of “bikeshedding” to locate a single critical request regarding a timeout adjustment. Gemini CLI then applies the precise update to the configuration file on the first try, demonstrating the model’s ability to distinguish signal from noise and execute accurate edits within massive context windows.

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Simulate Realistic User Traffic for Stress Testing

Validating your backend infrastructure requires traffic that mimics actual user behavior, but writing custom load‑testing scripts that handle concurrency and specific user journeys is often time‑consuming. These tasks are well‑suited for Gemini 3 Flash, which reduces syntax hallucinations and failure loops while still providing fast responses.

In this demo, Gemini CLI is used to stress‑test a web application hosted on Cloud Run. Gemini 3 Flash generates a Python script using asyncio to simulate concurrent users across three distinct scenarios:

1. Successful Order
2. Payment Failed
3. Inventory Timeout

When the initial execution returns protocol errors, the model instantly analyzes the traceback and patches the script. You can then launch a comprehensive load test and view the resulting metrics in your Cloud Run dashboard within seconds.

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Stay in the flow longer

Gemini 3 Flash provides a new performance baseline for high‑frequency development tasks in the terminal. By raising the performance floor and integrating with Gemini CLI’s auto‑routing, it helps you work faster and more efficiently. Whether you’re building a new prototype or managing complex infrastructure, you now have a development assistant that can keep up with your pace of work.

Update your Gemini CLI today to the latest version to start building faster — at a lower cost per token — with Gemini 3 Flash.

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