Is /simplify something I need to install?

No. It ships bundled with Claude Code and has since v2.1.63 (February 2026). Installing or updating the CLI is the whole setup — there is no repo to clone and no marketplace listing.

What's the difference between /simplify and /code-review?

/simplify is a cleanup-only pass — reuse, simplification, efficiency, altitude — and it applies the fixes without hunting for bugs. /code-review reports correctness bugs at a chosen effort level and only edits your files when you pass --fix.

Why do older articles describe /simplify doing something different?

Because it changed identity twice in 2026: renamed to /code-review at v2.1.147 in May, then reinstated as cleanup-only at v2.1.154 days later. Posts written between February and May 2026 describe a command that no longer behaves that way.

Does it work on my whole codebase?

No — it reviews changed code: your branch's commits ahead of upstream plus uncommitted edits. For a repo-wide simplification pass, a standalone skill like Sentry's code-simplifier or Anthropic's code-simplifier plugin is the better fit.

Skill review · Anthropic official

Claude Simplify Skill

The Claude simplify skill most searches point to is /simplify, a skill bundled into Claude Code by Anthropic — not a separate download, and not on any marketplace. Run it after making changes and it reviews your recently changed code for reuse, simplification, efficiency, and altitude cleanups, then applies the fixes straight to your working tree. It is quality-only by design: it does not hunt for bugs, and Anthropic's docs point bug-hunters at /code-review --fix instead. One thing to know before relying on it: the command was reshaped twice in 2026. It shipped in v2.1.63 in February, was renamed to /code-review in v2.1.147 in May with the cleanup behavior removed, then came back three versions later as the cleanup-only skill it is today. Scripts written against the old behavior broke both times. There is no SKILL.md to inspect — the prompt ships inside the CLI — so everything here is verified from Anthropic's changelog and official documentation.

View the sourcelicense unclear · 143,658★ · facts checked September 1, 2026

By Robert MacKelfresh

Founder, Automation Squad · September 1, 2026

Install

1Install Claude Code if you don't have it: `npm install -g @anthropic-ai/claude-code`, or use the native installer from claude.com/claude-code. /simplify ships inside the CLI — there is nothing separate to download.
2Update to a current build with `claude update`. You need v2.1.154 (May 2026) or later for today's cleanup-only behavior; versions between v2.1.63 and v2.1.146 ran an older, different /simplify.
3Do some work first. /simplify reviews changed code, so it needs commits ahead of your upstream or uncommitted edits to have something to act on.
4Type /simplify in your session. It reviews the changes, applies the fixes, and reports what it did — then check the result with `git diff` before committing.
5Skip the Claude.ai Settings → Skills upload path entirely: /simplify is a Claude Code bundled skill and does not exist on claude.ai chat.

What it does

Cleanup-only review: Reviews your recently changed code — the branch's commits ahead of upstream plus uncommitted edits — for reuse, simplification, efficiency, and altitude cleanups. Per the changelog (v2.1.154), it deliberately skips the bug-hunting pass that /code-review runs.
Applies fixes automatically: Unlike a plain review, /simplify applies its findings to your working tree. You get edited files, not a list of suggestions — the follow-up step is reading the diff, not implementing advice.
Shares the /code-review machinery: Since v2.1.152 it has run on the same review engine as /code-review, which in current builds runs as a background subagent with its own context window; results land back in your conversation when done.
Explicit division of labor: Anthropic's code-review docs state it plainly: /simplify runs a separate cleanup-only review that applies fixes without hunting for bugs, and anyone who scripted /simplify for bug-finding should switch to /code-review --fix.
Respects project conventions: Reviews in this family follow your repository's CLAUDE.md like any Claude Code session, so cleanups land in your house style rather than a generic one.

Common questions

Is /simplify something I need to install?: No. It ships bundled with Claude Code and has since v2.1.63 (February 2026). Installing or updating the CLI is the whole setup — there is no repo to clone and no marketplace listing.
What's the difference between /simplify and /code-review?: /simplify is a cleanup-only pass — reuse, simplification, efficiency, altitude — and it applies the fixes without hunting for bugs. /code-review reports correctness bugs at a chosen effort level and only edits your files when you pass --fix.
Why do older articles describe /simplify doing something different?: Because it changed identity twice in 2026: renamed to /code-review at v2.1.147 in May, then reinstated as cleanup-only at v2.1.154 days later. Posts written between February and May 2026 describe a command that no longer behaves that way.
Does it work on my whole codebase?: No — it reviews changed code: your branch's commits ahead of upstream plus uncommitted edits. For a repo-wide simplification pass, a standalone skill like Sentry's code-simplifier or Anthropic's code-simplifier plugin is the better fit.

Before you install

Not open source and no inspectable SKILL.md — the prompt ships inside the proprietary CLI. The anthropics/claude-code repo (143k stars) hosts the changelog and issue tracker, not the skill's source, and carries no license file.
Renamed and reshaped twice in three months: added in v2.1.63 (Feb 2026), renamed to /code-review with the old behavior removed in v2.1.147 (May 21, 2026), then reinstated as cleanup-only across v2.1.152–2.1.154 (May 26–28, 2026). Anything scripted against the old /simplify broke, and most tutorials published before June 2026 describe behavior that no longer exists.
It edits your working tree automatically, and Anthropic's docs note that background-review fixes land outside session checkpoints, so /rewind will not undo them — commit before running and use git to revert.
Quality-only by design: a clean /simplify pass says nothing about correctness. Bugs are /code-review's job.
Thin documentation — there is no dedicated /simplify docs page; its behavior has to be pieced together from the commands reference, the code-review page, and changelog entries.
Not free to run: Claude Code requires a paid Claude subscription or API billing, and the review consumes usage like any other session work.
Claude Code only — it cannot be uploaded or used in claude.ai chat via Settings → Skills.

Facts come from the skill's own repository and docs on the date above, via the GitHub API — not from memory, and never from a sponsor.

Worth comparing

code-simplifier (anthropics/claude-plugins-official) — Anthropic's official plugin-marketplace agent for the same job — Apache-2.0, so the prompt is actually inspectable; installs via /plugin in Claude Code.
code-simplifier (getsentry/skills) — Sentry's Apache-2.0 skill, explicitly based on Anthropic's code-simplifier agent — a portable SKILL.md you can drop into .claude/skills or upload to Claude.ai (973 stars, pushed Aug 2026).
/code-review --fix (bundled) — The bundled sibling: hunts correctness bugs at a chosen effort level and applies the findings — use it when you want bugs found, not just cleanups.

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