Report · marked 25 Aug 2026

vercel/next.js

Solid foundations, held back in a few specific places.

JavaScript · 141,932 stars · 31,480 files · branch canary

77 /100 B+

Instructions 23/27Whether the repo tells an agent how to behave before it starts guessing. Losing marks on instruction quality and readme as an entry point.Setup 16/20Whether an agent can install the project and get it running without a human. Losing marks on environment config.Verification loop 24/25Whether an agent can check its own work. This is the category that most decides whether agent output is trustworthy. Losing marks on static type checking.Context economy 6/20Whether the repo fits in a context window, or fights it. Losing marks on no committed build output and file sizes fit in context.Navigability 10/10How quickly anything new can orient itself. Full marks.

Higher is better. Accent marks what is costing you most.

Fix these first

File sizes fit in context

A single file that fills the context window forces an agent to work from fragments, and it will confidently edit code it never saw. Splitting the worst offenders pays for itself immediately.

Environment config

Add a .env.example listing every variable with a safe placeholder value. It's the cheapest possible fix and it unblocks the whole first run.

README as an entry point

Give the README an Install and a Usage heading with real commands under each. Agents pattern-match on those headings.

The full marking

Every deduction below names the file or setting it came from.

Instructions 23/27 A

Whether the repo tells an agent how to behave before it starts guessing.

✓Agent instruction file 12/12

AGENTS.md is present, which is the format the most tools read.

Also found: CLAUDE.md

✗Instruction quality 10/12

Specific enough that an agent can act on it.

Worth fixing: it's 31k characters, which burns context on every single turn.

names the actual commands to run

uses headings, so an agent can skim it

includes copyable code blocks

✗README as an entry point 1/3

README exists but never explains how to get the thing running.

Give the README an Install and a Usage heading with real commands under each. Agents pattern-match on those headings.

Setup 16/20 A-

Whether an agent can install the project and get it running without a human.

✓Deterministic install 6/6

pnpm-lock.yaml pins the dependency tree.

Found pnpm-lock.yaml

✓Discoverable commands 6/6

Commands are declared where an agent will look for them.

package.json scripts (new-error, new-test, pr-adopt, clean, build, build-all…)

scripts/ directory

✗Environment config 0/4

Nothing documents the environment this needs. An agent will get a runtime error it can't diagnose.

Add a .env.example listing every variable with a safe placeholder value. It's the cheapest possible fix and it unblocks the whole first run.

✓Pinned runtime version 2/2

The language runtime version is pinned.

Found .node-version

✓Reproducible environment 2/2

.devcontainer/devcontainer.json gives a known-good environment.

Verification loop 24/25 A+

Whether an agent can check its own work. This is the category that most decides whether agent output is trustworthy.

✓Tests exist 8/8

20865 test files against 24337 source files.

e.g. .config/ast-grep/rule-tests/no-context-format-test.yml, .config/ast-grep/rule-tests/no-context-test.yml, .config/ast-grep/rule-tests/no-err-anyhow-test.yml

✓Test command is discoverable 7/7

An agent can find and run `npm run test`.

✓Continuous integration 4/4

38 GitHub Actions workflows define what "passing" means.

✓Lint and format rules 3/3

eslint.config.mjs encodes the house style.

✗Static type checking 2/3

Type checking is configured, but not in strict mode.

Turn on `"strict": true`. Type errors are the fastest feedback an agent gets, and non-strict mode silently discards most of them.

Context economy 6/20 D

Whether the repo fits in a context window, or fights it.

✗No committed build output 3/6

Generated output is committed: node_modules/.

Add these to .gitignore and `git rm -r --cached` them. Generated files pollute search results, so an agent grepping for a function finds the compiled copy and edits the wrong file.

✓.gitignore hygiene 3/3

.gitignore covers 58 patterns.

✗File sizes fit in context 0/6

132 source files are over 100KB.

A single file that fills the context window forces an agent to work from fragments, and it will confidently edit code it never saw. Splitting the worst offenders pays for itself immediately.

packages/next/src/compiled/webpack/bundle5.js — 2522KB

turbopack/crates/turbopack-ecmascript/tests/benches/packages-bundle.js — 2108KB

packages/next/src/compiled/babel-packages/packages-bundle.js — 1504KB

✗Repository weight 0/5

About 2542MB checked out. Large enough that cloning and searching are both slow.

Large binaries and vendored trees slow every operation an agent performs. Git LFS or a separate assets repo keeps the working tree navigable.

Here is your AGENTS.md

Drafted from what is actually in this repository: the install command from your lockfile, the commands you already declare, your real directory layout. Anything marked TODO needs a person. Save it at the root as AGENTS.md.

AGENTS.md — drafted for vercel/next.js

undefined

Open the raw markdown or curl -o AGENTS.md agentreadme.com/draft/vercel/next.js.md

Show the mark

The badge re-checks daily, so it keeps up as the repository changes. Use mark again to force it now.

[![agent ready](https://agentreadme.com/badge/vercel/next.js.svg)](https://agentreadme.com/vercel/next.js)

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All JavaScript repositories

Think this mark is wrong?

Every deduction above names the file it came from, so this can be settled by looking. If a check missed something, that is a rule worth fixing.

Open an issue, already filled in