Skip to content
Ultracite
Esc
↑↓navigate↵open⌘Jpreview

Vercel Agent reviews PRs against AGENTS.md

Vercel Agent’s Code Review reads AGENTS.md first among the guideline files it supports, so Ultracite’s rules become context for every pull request it reviews. It doesn’t edit as you work: it proposes fixes, runs each one in a Vercel Sandbox against your builds, tests and linters, and posts only the ones that pass.

Vercel Agent by VercelChecked against October 2026

# Ultracite Code Standards

This project uses **Ultracite**, a zero-config preset that enforces strict code quality standards through automated formatting and linting.

## Quick Reference

- **Format code**: `npx ultracite fix`
- **Check for issues**: `npx ultracite check`
- **Diagnose setup**: `npx ultracite doctor`

Oxlint + Oxfmt (the underlying engine) provides robust linting and formatting. Most issues are automatically fixable.

…
Ultracite’s rules
Where Vercel Agent looks for instructions
  1. 1AGENTS.mdUltraciteHighest priority. In a directory that has one, Code Review uses it and skips the other files.
  2. 2CLAUDE.mdUsed in a directory with no AGENTS.md.
  3. 3.github/copilot-instructions.mdThen Cursor (.cursor/rules/*.mdc, .cursorrules), Windsurf, Cline and other tools’ files, in that order.
  4. 4src/**/AGENTS.mdAdds to the parent directory’s guidelines for files in its subtree, and doesn’t affect anything outside it.
  5. 5@import "file.md"Guidelines can pull in other files with @import or relative Markdown links.

How Vercel Agent reads the rules

Code Review looks for guideline files in each directory and uses the highest-priority one there, with AGENTS.md at the top. Guidelines are inherited from parent directories and scoped to their own subtree.

Size limit
50 KB for all guidelines combined. Ultracite’s rules are about 5 KB.
Context, not orders
Guidelines are treated as context. Finding bugs, security issues and performance problems wins over any guideline that conflicts.
What to write
Vercel suggests guidelines cover what a linter can’t enforce. Ultracite’s rules end with a section on exactly that.
One per directory
With AGENTS.md and CLAUDE.md side by side, only AGENTS.md counts. A CLAUDE.md that just imports it loses nothing.
Triggers
New pull requests and new pushes to open ones, plus drafts if you turn that on. @vercel run a review starts one by hand.
Repositories
Reviews cover repositories connected to your Vercel projects: all of them by default, or only public or only private ones.

Fixes tested in a sandbox before you see them

Code Review writes a patch for each fix it proposes, runs it in a Vercel Sandbox with your real builds, tests and linters, and only posts suggestions that pass. Vercel’s docs don’t say how it picks those commands, so ultracite check in CI stays the gate for every commit.

- **Format code**: `npx ultracite fix`
- **Check for issues**: `npx ultracite check`
- **Diagnose setup**: `npx ultracite doctor`
What the rules tell it to run
  1. 01A pull request is opened or gets new commits, or someone comments @vercel run a review.
  2. 02Code Review reads the change against the whole codebase, with AGENTS.md as guidelines.
  3. 03Each proposed fix runs in a Vercel Sandbox against your builds, tests and linters; only passing ones are posted.
  4. 04You apply a suggestion with one click, and your CI runs ultracite check on the new commit.

Worth knowing about Vercel Agent

  • @vercel in pull request comments

    Mention @vercel in any pull request comment: @vercel run a review runs a full review, @vercel fix the type errors implements and commits a fix, and @vercel why is this failing? investigates. Replies land in the same thread.

  • It reads your CI results

    For a linked repository, Vercel Agent can read CI check results and save a check-job log to inspect. When it opens a pull request of its own, it works on a vercel-agent/ branch and only after you approve the plan.

  • Private packages in the sandbox

    If your tooling comes from a private registry, add NPM_TOKEN or NPM_RC as a Shared Environment Variable in Development or Preview so the sandbox can install dependencies. The credentials stay outside the sandbox.

  • The Ultracite skill

    Vercel Agent’s docs don’t describe loading SKILL.md skills, so the Ultracite skill in .agents/skills/ doesn’t come into it. Code Review gets the rules from AGENTS.md instead.

Vercel Agent questions, answered

Does Vercel Agent read AGENTS.md?
Code Review does. AGENTS.md is first in its list of guideline files, ahead of CLAUDE.md, .github/copilot-instructions.md and Cursor rules, and it applies by directory: inherited from parents, scoped to its own subtree.
Does Vercel Agent run my linter?
When it proposes a fix, yes: it runs the patch in a Vercel Sandbox against your real builds, tests and linters, and only shows suggestions that pass. That checks its own suggestions, not every commit, so keep ultracite check as a required CI check.
Why does Code Review ignore my CLAUDE.md?
When several guideline files share a directory, Code Review uses only the highest-priority one, and AGENTS.md outranks CLAUDE.md. Move what reviews need into AGENTS.md, or pull it in from there with @import "CLAUDE.md".
Can Vercel Agent fix lint errors on a pull request?
Mention @vercel with the request in a pull request comment. Vercel’s docs give @vercel fix the type errors as an example that implements and commits a fix, and @vercel why is this failing? to investigate.
Which Vercel plans include Vercel Agent?
Pro and Enterprise, in public beta. Code Review bills by tokens: the AI provider’s rate with no markup, plus $0.25 per million tokens.

Sources

Keep going

Ship less slop

One command sets up your linter, formatter, editor and agents. Works with Oxlint, Biome and ESLint.