usemux

A pull request can look harmless and still break something in a file it never touched. Try Reviewer in Cowork: usemux.com/cowork

Writing code with agents is fast. Reviewing it is the bottleneck. That was the #1 piece of feedback we got on Cowork. An agent can open a PR in minutes, but someone still has to verify it. And the bugs that actually break production rarely look obvious in an isolated diff. Today, we're launching Reviewer. It is live now in Cowork's new Code Review tab, in muxcode, and on the mux web app. Point Reviewer at any repository in your workspace index and define the paths you care about. It reviews every matching open PR immediately, and re-checks every 10 minutes. It runs in the background on mux, so it keeps working when your laptop is closed. Most tools only read the diff. Reviewer reads the surrounding system: → Upstream callers of modified symbols, even across untouched files → Downstream imports and the exact lines where changed files are consumed → Your repository's REVIEW.md and workspace context Why this matters in practice: In one of our test repos, a PR updated surcharge rates from fractions (0.12) to percentages (12). The diff itself looked clean. Because Reviewer traced the callers, it saw that src/quote.js still multiplied the return value as a fraction. A 1,200 surcharge would have turned into 120,000. Reviewer marked the PR as blocking, wrote the fix, and generated a test covering quote.js end-to-end. Every review gives you the failure mode, severity, proposed fix, and a test to catch it, linked to exact files and line numbers. If it hits a blind spot it cannot read, it states that explicitly instead of hallucinating a clean bill of health. Two invariants we built in from day one: 1. Reviews remain private drafts until you explicitly enable posting. 2. Reviewer never approves. It comments or requests changes; a human always merges. To everyone who told us review was the bottleneck: thank you. We built this for you. Cowork and Reviewer are included in mux Pro, Pro+, and Team plans.

Introducing Cowork, in muxcode 1.0.19. Paste an issue, or just say what's broken. Cowork asks only what's missing, proves it with a failing test, fixes it, and opens a draft PR for you. Cowork is on Pro and Pro+, with DeepSeek V4.1 Flash included. usemux.com/cowork/

Bring the models you already use, run a task in a cloud sandbox, follow the agents as they work, and review the changes before applying them. This walkthrough takes a real bug from prompt to verified fix, with passing tests and a diff you can inspect. muxco.de

ship more, and better, with the models you already use.

Introducing mux: the durable harness for your coding agents. Now in Preview. Start with muxcode, a free Mac app. Your agent runs on your machine and only does what you allow. Try it: usemux.com