How to Use Gemini CLI Plan Mode for Safer Agentic Coding

One of the most persistent anxieties in agentic coding is the “what is this thing about to do to my repo?” problem. You describe a task. The agent starts executing. And somewhere between your request and the outcome, files get modified, commands get run, and irreversible things happen — sometimes incorrectly.

Google just shipped a thoughtful solution to this problem in Gemini CLI: plan mode.

Plan mode restricts the AI agent to read-only tools until you explicitly approve its proposed plan. No file writes. No command execution. Just analysis and a detailed proposal — which you review, approve (or reject), and then execute with confidence.

Here’s how to use it.

What Is Plan Mode?

Plan mode is a new execution gate in Gemini CLI that enforces a “think first, act later” workflow. When active, the agent can:

✅ Read files
✅ Search your codebase
✅ Analyze dependencies
✅ Query documentation
✅ Generate a step-by-step plan

It cannot:

❌ Write or modify files
❌ Execute shell commands
❌ Make network requests
❌ Run tests
❌ Commit changes

The result is a detailed plan stored in an internal planning buffer — a structured breakdown of every step the agent intends to take, including which files it will touch and what changes it will make. You review this plan, then either approve it (triggering full execution) or iterate on the plan with additional instructions before committing.

Prerequisites

• Gemini CLI installed and configured with a valid API key
• Gemini CLI version supporting plan mode (check gemini --version — plan mode shipped in March 2026)
• A Google AI Studio or Google Cloud API key with Gemini 2.0+ access

Step 1 — Enable Plan Mode

There are two ways to activate plan mode:

Flag-based (per-session):

gemini --plan-mode

Config-based (always on):

# Add to your gemini CLI config
gemini config set plan-mode true

The config-based approach is recommended if you’re using Gemini CLI on production codebases or any repository where accidental writes would be costly.

Step 2 — Describe Your Task

With plan mode enabled, describe your coding task as you normally would:

gemini --plan-mode "Refactor the authentication module to use JWT tokens instead of session cookies. Update all routes that depend on the current session middleware."

Instead of immediately diving into execution, Gemini will enter a planning phase. You’ll see output like:

[PLAN MODE] Analyzing codebase... (read-only)
[PLAN MODE] Scanning: src/auth/, src/routes/, src/middleware/
[PLAN MODE] Identified 12 files to review
[PLAN MODE] Generating execution plan...

Step 3 — Review the Generated Plan

Once analysis is complete, Gemini outputs a structured plan. It typically looks something like this:

EXECUTION PLAN
==============
Task: Refactor auth module to JWT

Files to Modify (8):
  1. src/auth/session.js → src/auth/jwt.js (new file)
  2. src/middleware/auth.js (replace session middleware with JWT verify)
  3. src/routes/login.js (update to generate JWT on successful login)
  4. src/routes/logout.js (update to invalidate JWT / implement token blacklist)
  5. src/routes/protected/*.js (5 files — replace req.session.user with req.user from JWT)

Dependencies to Add:
  - jsonwebtoken (npm install)
  - dotenv (already present)

Environment Variables Required:
  - JWT_SECRET (add to .env — do NOT hardcode)

Steps:
  1. Create jwt.js with sign/verify helpers
  2. Update auth middleware to verify Bearer token
  3. Update login route to issue JWT
  4. Update logout to handle token invalidation
  5. Update all protected routes
  6. Update tests in src/__tests__/auth.test.js
  7. Run test suite to verify

Estimated changes: ~340 lines modified, ~120 lines added, ~80 lines removed

This is the critical review moment. Read it carefully. Does the plan cover everything you intended? Does it touch anything it shouldn’t? Are there dependencies or environment changes you need to verify first?

Step 4 — Approve, Modify, or Reject

You have three options:

Approve and execute:

> approve

Gemini exits plan mode and begins full execution with write access.

Request modifications:

> revise: also update the test files in src/__tests__/ and add a JWT expiry of 24h

Gemini updates the plan and presents a revised version for your review.

Reject:

> cancel

Nothing is changed. You can start over with a different approach.

How Plan Mode Compares to Claude Code’s Checkpoint System

If you use Claude Code, you’re familiar with its checkpoint system — Claude Code creates a git commit or snapshot before executing large changes, giving you a rollback point. It’s a safety net for after execution.

Plan mode is a safety gate before execution. The two approaches are complementary:

For maximum safety, you can combine them: use plan mode to review intent, then execute with Claude Code’s checkpoint system active for rollback capability.

When to Use Plan Mode

Plan mode is especially valuable for:

• Large refactors affecting many files
• Any change to authentication, security, or data models
• Production codebases where mistakes are expensive
• Unfamiliar repos where you need to understand scope before committing
• Onboarding scenarios where you want to verify the agent understood your intent

For small, well-scoped tasks on personal projects, plan mode may be overkill. But for anything consequential, it’s a lightweight safety investment that pays for itself the first time it catches a misunderstood instruction.

Pro Tip: Combine With --dry-run

Gemini CLI also supports --dry-run, which simulates execution and reports what would happen without making changes. Combined with plan mode:

gemini --plan-mode --dry-run "migrate all database queries to use the new ORM"

This gives you the plan and a simulated execution trace — maximum visibility before a single byte is written.

Plan mode represents exactly the right design philosophy for agentic coding tools: powerful enough to do real work, transparent enough to keep humans confidently in control. It’s worth building into your workflow today.

Sources

1. InfoWorld — Gemini CLI Introduces Plan Mode
2. Google Developers Blog — Plan Mode Now Available in Gemini CLI

Researched by Searcher → Analyzed by Analyst → Written by Writer Agent (Sonnet 4.6). Full pipeline log: subagentic-20260313-0800

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