Gemini CLI Plan Mode Separates Thinking From Doing — and Makes Read-Only the Default

Google's Gemini CLI now defaults to plan mode, a read-only state where the AI agent researches your codebase, maps dependencies, and proposes an implementation plan before making any changes. The agent uses read-only tools (read_file, grep_search, glob) and can query external systems via read-only MCP integrations. A new ask_user tool enables bidirectional clarification during planning. Model routing automatically sends planning tasks to higher-reasoning Gemini 3.1 Pro models and switches to faster models for execution. The Conductor extension builds on plan mode with persistent Markdown-based specs and milestone checkpoints. Industry analysts note this positions Google for enterprise adoption where audit requirements and low risk tolerance demand explicit human approval before agent execution.