error-pages

A launch-ready 404 is not "404 Page Not Found" on a blank framework default. It is a page that returns 404, looks like your product, and gets the visitor moving again. And a pretty 404 served with HTTP 200 is a soft-404 that search engines treat as real content.

Activate when

• Any site with routes; especially SPAs (Vite/CRA) where unknown URLs fall through to index.html with 200.
• The 404 is a framework default, unstyled, missing, or LINK_SOFT_404 showed up in check-links.
• Not for intentional redirects or for private/authenticated route handling (that is authorization).

Working alone

This skill is self-contained. Its companions (declared in its metadata) are skills whose method it may need to do its own promised work. Use of a companion can be conditional: declaring one does not mean running it. When a companion's lane applies, use the skill if it is installed; if not, follow its short entry in references/companion-methods.md and say in your report which lanes ran inline at reduced depth. Never skip an applicable lane silently. Skills mentioned here only for escalation, referral, documentation, or optional deeper follow-up are not dependencies: report the hand-off and finish honestly.

Companions: design-system-reconnaissance.

Inspect