Cursor Bugbot and Design Bug Bot are different products from different companies, despite the similar names. Bugbot is the AI code reviewer in Cursor, whose maker is Anysphere (Cursor terms): it reads pull request diffs and reports bugs, security issues, and code quality problems. Design Bug Bot is a GitHub App made by 21st that reviews the UI code in a pull request against the components, tokens, spacing, and type scale your repository already uses.
Use Bugbot for logic, security, and code-quality review, including on GitLab, Bitbucket, or Azure DevOps. Add Design Bug Bot when a React team on GitHub keeps merging UI that works correctly but does not match the rest of the product.
Disclosure: 21st makes Design Bug Bot and published this comparison. It relies on Cursor's documentation, pricing page, blog, and changelog as checked on September 14, 2026. We did not run the two bots on a shared set of pull requests, so nothing here is a benchmark or an accuracy claim.
Cursor Bugbot and Design Bug Bot at a glance
| Area | Cursor Bugbot | Design Bug Bot |
|---|---|---|
| Review job | Bugs, security issues, and code quality problems in PR diffs. Bugbot docs | Reuse of existing components, tokens, spacing, and type scale, plus layout risks and unnecessary dependencies |
| What it reads | The diff, earlier PR comments, and your Bugbot rules. Bugbot docs | Changed UI code, compared with what the repository already contains |
| Rendered UI evidence | Not described in the Bugbot docs; Cursor's cloud agents attach screenshots to PRs they write. Changelog | Screenshots at desktop and mobile widths when its isolated render succeeds; code-backed recommendations when it cannot |
| Fixes | Fix suggestions; Autofix can spawn a Cloud Agent that pushes fixes. Bugbot docs | Suggested fix code in each finding; can push a branch to open a fix pull request |
| Merge blocking | Findings default to a neutral check; where fail-on-unresolved-issues is available, findings can fail it. Bugbot docs | Advisory: one updated comment and a check for each reviewed commit |
| Source control | GitHub, GitLab, Bitbucket, and Azure DevOps. Bugbot docs | GitHub only, for React codebases such as Next.js or Vite |
| Pricing model | Usage-based billing. Bugbot docs | 5 free successful reviews, then AI credits. Details |
What Bugbot does well
Bugbot sits in the pull request loop without extra ceremony. It reviews every PR update automatically, or on demand when someone comments "cursor review" or "bugbot run". It reads earlier top-level and inline comments to avoid repeating feedback, and by default it reviews only what changed since its last pass. Bugbot docs
Its rules are layered. Team admins set rules for every repository, a root .cursor/BUGBOT.md file always applies, and nested BUGBOT.md files apply when changed files sit below them, so a frontend folder can carry its own guidance. Learned rules come from your team's GitHub activity or an "@cursor remember" comment, manual rules can be scoped to paths, and "bugbot run verbose=true" lists every rule a run used.
Fixes are close at hand. Comments link to the issue in Cursor or on the web, and Autofix can spawn a Cloud Agent that pushes a fix to a new or existing branch. Developers can also run the same review from the agent with the /review-bugbot skill before pushing.
Where Design Bug Bot differs: the button that is not a bug
Picture a pull request that adds a pricing card with a hand-built Upgrade button: its own padding, radius, and hex color, although the repository already has a Button with a primary variant. The card also has a fixed width that makes the page scroll sideways on a phone. The click handler works, the types check, and nothing is insecure. To a code reviewer, this pull request is clean.
Bugbot can be taught to care: a frontend .cursor/BUGBOT.md could name the button to use and the allowed color tokens. But a rule is text your team has to keep current as components change, and Cursor's editor rules (the .mdc files in .cursor/rules) do not apply to Bugbot runs, so design guidance written for the agent must be restated for the reviewer. Bugbot docs
Design Bug Bot starts from the design system already in your code. It compares changed UI with your components, tokens, spacing, and type scale, and looks for layout risks such as horizontal overflow, fixed widths, and actions hidden on mobile. A finding explains the problem, points to the file and line when available, and includes suggested fix code you can inspect, copy, or hand to a coding agent.
It also tries to see the result. Changed pages and components are rendered in a React harness inside a disposable sandbox; when that works, the review can include screenshots and visual checks at desktop and mobile widths. When it cannot render, findings are labeled as code-backed recommendations.
It is not a general code reviewer for logic, security, or backend bugs, it does not block merges, and it is GitHub only and React-focused. It sits next to Bugbot rather than replacing it.
How to run them side by side
The PR passes Bugbot and still adds a second button. A passing or neutral Bugbot status says nothing about design reuse, and it is not meant to. Pointing to the existing component is Design Bug Bot's job.
Your code lives on GitLab, Bitbucket, or Azure DevOps. Design Bug Bot is GitHub only. There, a frontend BUGBOT.md file is the practical way to bring UI conventions into review.
A Cursor cloud agent wrote the PR and attached screenshots. Cloud agents can test the software they build in their own VM and attach videos, screenshots, and logs to their PRs. Changelog That shows the feature working; whether it reuses your components and holds up on mobile is a separate check.
You need a hard merge gate. Bugbot's check can fail on unresolved issues where your organization has that option. Treat Design Bug Bot's advisory check as input for the human reviewer.
Bugbot pricing
Cursor announced on May 11, 2026 that Bugbot was moving from a per-seat subscription to usage-based billing, starting for existing customers at the next renewal after June 8, 2026. Cursor blog
Listed on Cursor pricing on September 14, 2026: the Individual plan ($20 per month) includes "Bugbot on usage-based billing," and the Teams plan ($40 per user per month) includes "Agentic code reviews with Bugbot." Per the Bugbot docs, Teams usage bills from on-demand spend, and individual reviews use included usage first.
Design Bug Bot's free reviews and AI credit billing are covered in its trial and billing details.
Test both on one of your own pull requests
- Recreate two past changes on fresh branches: one that shipped a logic bug, and one that shipped a duplicate component or a mobile overflow. Write down the finding you expect for each.
- Let Bugbot review both as configured today. Then add a frontend BUGBOT.md file with your component and token rules, rerun it on the UI change, and confirm with "bugbot run verbose=true" that the rule was included.
- Let Design Bug Bot review the UI change in a GitHub repository, and note whether the findings came with screenshots or as code-backed recommendations.
- Compare fixes, not comment counts: which suggestion pointed to a component you already have, and which you would merge without rewriting.
Compare more code reviewers in CodeRabbit vs Design Bug Bot and the AI UI review tools guide. Open Design Bug Bot
Frequently asked
- Is Design Bug Bot made by Cursor?
- No. Bugbot is the AI code reviewer in Cursor, which is made by Anysphere, and it looks for bugs, security issues and code quality problems. Design Bug Bot is a separate GitHub App made by 21st that reviews UI changes against your repository's own components, tokens, spacing and type scale.
- Can Bugbot check UI design if I add rules?
- Partly. Bugbot reads team rules, learned and manual rules, and .cursor/BUGBOT.md files, including nested files in a frontend folder, so you can describe component and token conventions there. Cursor's .mdc editor rules do not apply to Bugbot runs, and a written rule does not render the change.
- Do Cursor's cloud agent screenshots mean Bugbot reviews visuals?
- No. Cursor's February 24, 2026 changelog says cloud agents can test the software they build and attach videos, screenshots and logs to the PRs they create. The Bugbot docs describe diff review. Design Bug Bot attempts a sandboxed render of changed components and adds desktop and mobile screenshots when it succeeds.
- How is Cursor Bugbot billed now?
- Cursor announced on May 11, 2026 that Bugbot was replacing seat fees with usage-based billing. Its docs say individual reviews use included usage first, then on-demand spend, and Teams usage bills from on-demand spend. Design Bug Bot starts with 5 free successful reviews, then uses AI credits.