Gemini CLI Unveils 'Explain Mode' to Enhance Developer Codebase Comprehension

Philipp Schmid, AI Developer Experience at Google DeepMind, recently announced the introduction of "Explain Mode" for the Gemini Command Line Interface (CLI). This new feature is designed to assist developers in quickly grasping the structure, features, and implementation details of large or unfamiliar codebases, building upon the previously introduced "Plan Mode." The initiative aims to leverage Gemini's capabilities to significantly reduce the time developers spend understanding new projects.

According to Schmid's social media post, "When working on a large codebase or if you are new to a project you always need time to understand the project structure, what features are implemented and how. What if you can ask and use Gemini to help to get you up to speed?" This highlights the core problem "Explain Mode" seeks to solve by enabling interactive queries about code. The feature is currently in testing and evaluation, with Schmid noting "strong signal sofar" regarding its effectiveness.

Gemini CLI itself is an open-source AI agent that integrates Google's Gemini large language model directly into the terminal environment. It operates using a "reason and act" (ReAct) loop, utilizing built-in tools and external Multi-Context Processing (MCP) servers to handle complex development tasks. These tasks range from fixing bugs and creating new features to improving test coverage, providing a comprehensive AI-powered assistant for coding workflows.

The "Explain Mode" follows the earlier "Plan Mode," which allows developers to define custom instructions for strategic planning using GEMINI md files. This enables the AI to analyze, reason, and create detailed, read-only plans for development tasks without directly modifying the codebase. Both modes underscore a strategic approach to integrating AI into the developer workflow, emphasizing understanding and planning before execution.

The Gemini CLI offers free usage for Gemini 2.5 Pro, including its 1 million token context window, for up to 1,000 requests. This accessibility positions it as a competitive tool in the burgeoning market of AI coding assistants, alongside offerings like OpenAI Codex and Claude Code. While still undergoing evaluation, "Explain Mode" represents a significant step towards making large language models more practical and integrated tools for daily software development challenges.