## TL;DR
`prettier --check` fails when files do not match prettier's style; the fix is to let prettier rewrite them with `prettier --write`. Run write on the repo, re-run check, and expect the all-clean message. Then make sure your editor uses the same config so it stays clean.

```text
$ npx prettier --check .
Checking formatting...
[warn] src/app.js
[warn] src/util.js
[warn] Code style issues found in 2 files. Forgot to run Prettier?
```

1. See the full list: `npx prettier --check .` (the same command CI runs). Expected: one `[warn]` line per offending file plus the summary count.
2. Fix them: `npx prettier --write .`. Expected: each file prints with its timing, for example `src/app.js 12ms`.
3. Verify: `npx prettier --check .` again. Expected: `All matched files use Prettier code style!` and exit code 0.
4. Commit the reformatted files and push. Expected: the style gate passes.
5. Stop the recurrence: confirm the repo's prettier config file is committed and your editor's format-on-save points at the repo's prettier version.

## Use this when
- The PR style gate fails with prettier's file list
- You want the exact write command that fixes it
- The failure count is small and mechanical

## Not for this skill when
- The failure is eslint, not prettier; different tool, different fix
- prettier and eslint rules fight each other; hand style to prettier via eslint-config-prettier
- The repo has no prettier config; adding one is a team decision, not a PR fix

## Variant phrasings
- "prettier check fails how to fix"
- "code style issues found in N files prettier"
- "prettier write versus check"

## Why it happens
prettier is opinionated: one style, no options that matter. Any edit made without prettier (or with a different config) diverges from that style, and --check reports the divergence without changing anything.

## Edge cases
- A prettierignore mismatch between local and CI changes the file set; keep the ignore file committed.
- prettier version drift changes output; pin the version in package.json and run via npx so everyone uses the same one.
- If --write reformats huge unrelated sections, the file was never prettier-clean; that is a pre-existing condition worth one cleanup commit, not a reason to skip.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_7c7D3adZ2KXjfskeQ8Qwww