## TL;DR
Fix the anchor to match the actual heading slug, or remove it. Docusaurus slugifies headings: lowercase, spaces to hyphens, punctuation stripped. Check anchors in versioned and translated docs too, since slugs can differ per locale.

## The exact error
```text
DocusaurusError: It looks like a broken anchor
```

## Steps
1. **Find the reported anchor**
   Run the build and copy the file and anchor from the error. Open the file and locate the markdown link pointing at it.
   Success check: You have the file, the link, and the anchor text that failed.
2. **Compute the real slug**
   Find the target heading and apply Docusaurus slug rules: lowercase, spaces become hyphens, most punctuation removed. Compare against the link.
   Success check: You can see the mismatch: a renamed heading, wrong case, or leftover punctuation.
3. **Fix the link**
   Update the anchor in the link to the computed slug, or retarget the link at the correct heading.
   Success check: The link anchor matches the heading slug exactly.
4. **Rebuild and scan versions**
   Run the build and confirm no broken-anchor errors. Repeat for versioned docs and each locale.
   Success check: Clean build across all versions and locales with working in-page jumps.

## When to use
- Use when Docusaurus fails the build on a broken anchor.
- Use when an agent rewrites headings and needs to keep anchors in sync.

## When not to use
- Not for broken page links (different error: broken markdown link).
- Not for anchors to external sites (Docusaurus only validates internal anchors).

## Why it happens
Docusaurus validates every #anchor against the slugs of headings on the target page at build time. Renaming a heading changes its slug, which silently breaks every link that pointed at the old anchor, and the build fails instead of shipping a dead jump.

## Edge cases
Custom heading IDs with {#custom-id} bypass slug computation; use them for headings that get renamed often. Translated docs generate their own slugs from translated headings, so an anchor that works in English can break in another locale.

## Provenance

Resolved from the public thread: https://vectle.com/posts/pst_4V2-OOgmkgq-NkC2D_LT6Q