Claude Code Plan Mode: Complete Guide (2026)

Most agent mistakes don't happen because the model picked the wrong fix. They happen because it started executing before anyone — human or Claude — fully understood the problem. Plan mode exists to force that understanding first. It's a restricted mode where Claude can look at your codebase but can't touch it, and has to produce a written plan before it's allowed to write a single line.

If you've read our guide to permission modes, plan mode is one of the modes in that same rotation — but it deserves its own breakdown because it's the one most people under-use. Default mode asks permission per action. Auto-accept skips asking. Plan mode skips acting entirely until you've signed off on the whole approach.

What Plan Mode Actually Restricts

In plan mode, Claude is limited to read-only tools: reading files, searching code, grepping for patterns, fetching web pages, listing directories. Anything that would change state — editing a file, running a bash command with side effects, writing a new file — is unavailable. Not "ask before doing it." Unavailable. The model physically cannot call those tools while plan mode is active.

This matters because it changes what the model optimizes for. In default mode, an agent can course-correct live: try something, see it's wrong, try again. In plan mode there's no live feedback loop, so the incentive shifts toward getting the investigation right before committing to an approach — reading more context, checking more call sites, being explicit about tradeoffs instead of picking one silently.

Turning It On

Cycle through permission modes with Shift+Tab, or jump straight to plan mode from the command line:

claude --permission-mode plan

Mid-session, tell Claude directly — "switch to plan mode" or "don't make any changes yet, just investigate and propose a plan" — and it will use the mode-switching tool itself. You'll see the mode indicator change in the session, confirming no edit or bash-with-side-effects tool is going to fire until you approve something.

The Plan Review Loop

Here's the actual mechanic: Claude investigates using read-only tools, then instead of writing code, it presents a structured plan — what it's going to change, which files, in what order, and why — and stops. You get three options: approve as written, ask for changes, or reject and redirect entirely. Only on approval does Claude switch out of plan mode and start executing exactly what was presented.

This is the part people skip and shouldn't. The plan is your one chance to catch a bad approach before any code exists to review. Read it like you'd read a design doc, not like you'd skim a diff:

• Scope — is this touching only what you asked, or did it scope-creep into "related" files you didn't mention?
• Order of operations — for anything with migration or backward-compat implications, does the sequence avoid a broken intermediate state?
• Missing pieces — did it account for tests, config, or the other call sites of the thing it's changing?
• Assumptions stated out loud — a plan that says "I'm assuming X behaves like Y" is giving you a chance to correct a wrong assumption for free, before it's baked into code.

Rejecting a plan costs nothing — no files were touched. Rejecting a diff after the fact costs a rewrite. That asymmetry is the entire value proposition of plan mode.

Plan Mode vs. Auto-Accept vs. Output Styles

These get grouped together because they're all session-level toggles, but they control different things:

You can combine them: plan mode with the Explanatory output style gives you a heavily-narrated investigation phase, which is useful when you're using Claude to understand a change before you decide whether to let it happen, not just to make the change faster.

When to Actually Use It

Plan mode earns its keep on anything where the cost of a wrong first attempt is high relative to the cost of a few extra minutes reviewing a plan:

• Unfamiliar codebases — you don't have the context to catch a bad diff by eye yet, but you can catch a bad plan.
• Multi-file refactors — the risk isn't any single edit, it's the ordering and completeness across files. A plan surfaces that before execution.
• Anything touching auth, billing, or data migrations — domains where "try it and see" isn't an acceptable debugging strategy.
• Ambiguous requests — if you're not 100% sure what you asked for maps to one obvious implementation, plan mode forces Claude to make its interpretation explicit instead of guessing silently.

Skip it for small, reversible, well-scoped changes — fixing a typo, adding a single test, a one-line config change. Making Claude write a plan for a change simpler than the plan itself is friction with no payoff. Default mode with normal per-action approval is faster there.

What It Doesn't Protect Against

Plan mode reviews the intended approach, not the eventual execution. Once you approve a plan, Claude executes with the same care and same failure modes as default mode — it can still make an implementation mistake within an otherwise-sound plan, misread a file, or hit an edge case the plan didn't anticipate. Plan mode catches wrong direction, not wrong execution. For the latter, you still want checkpoints and /rewind as your safety net during the execution phase itself.

It also isn't a substitute for permission boundaries on genuinely dangerous operations. Plan mode blocks all write-capable tools uniformly — it doesn't distinguish "safe to auto-approve" from "needs a human" the way a permission config does. Use both together: plan mode for the investigation phase, a scoped permission mode for the execution phase.

A Simple Default

If you're not sure which mode to start a session in, the rule that scales: start new, non-trivial tasks in plan mode. Read the plan. Approve, correct, or redirect. Then let execution run in default or auto-accept depending on how much you trust the specific change. That sequence — plan, approve, execute — costs one extra read per task and prevents the most expensive class of agent mistake: confidently building the wrong thing quickly.