# Plan mode

## Start with a question

Choose **Plan** from the chat composer's mode picker. Describe the outcome, constraints,
and what needs deciding. Include the relevant files or project context.

For example:

> Investigate how sign-in works. Propose the smallest change that adds a retry state.
> Identify affected files, risks, and tests. Save the plan; do not implement it yet.

## What Plan can do

Plan has read-only investigation tools plus file-writing tools intended for Markdown
plans. These writes still pass through approval handling. It can save a plan such as
`PLAN.md` or `docs/plans/sign-in-retry.md`. Non-trivial plans can open in a rendered
preview alongside chat.

Plan is not a promise that nothing is written: plan documents and memory can be updated.
Source-code changes and terminal execution belong in an implementation mode.
Delegated work in Plan uses the read-only research profile.

## Review before implementation

A useful plan names the files involved, explains alternatives, identifies risks, and
defines how the result will be tested. Read the saved document and correct assumptions.
Then explicitly switch to **Agent** and ask it to implement the approved plan.

A saved plan is not an executed change. Check the actual diff and test results afterward.

See [Modes](/editor/modes), [Debug](/editor/debug-mode), and [Subagents](/editor/subagents).