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Fix: Unknown paths return HTTP 404 or 410

Web-audit fix skill for the agent-friendly-404 check (Discoverability, SHOULD).

Goal

Return a real HTTP 404 or 410 for unknown paths instead of a 200 SPA shell.

Fix

Configure the origin so a nonsense path under the site returns HTTP 404 or 410, not 200 with the application shell. A soft-404 hides recovery from agents: they treat the page as content and never look for a sitemap or llms.txt. Verify with curl -sS -o /dev/null -w "%{http_code}" https://example.com/this-path-does-not-exist — it MUST print 404 (or 410).

Resources

Copy-paste prompt

Paste this into your coding agent. Your audit adds what it observed for this check:

Verify

Re-run the audit at https://anc.dev/audit or call the audit_website MCP tool; the agent-friendly-404 check should report pass.