RULE: Treat URL/slug design as a 10-year decision. Never let a slug change without a 301 redirect.

Rule: Every Candid client URL is designed for permanence. Slug renames require a 301 redirect from the old path. The redirect map is maintained for the life of the site — never garbage-collected.

Why: Zittrain et al. (Harvard Law 2014): 50% of URLs in Supreme Court opinions suffer reference rot (Zittrain et al. (Harvard Law 2014): 50% of URLs in U.S. Supreme Court opinions suffer reference rot). When the open web's most prestigious citation infrastructure rots at 50%, the typical SMB site's URL discipline is much worse. Every broken inbound link is a lost citation, a degraded SEO signal, a frustrated returning visitor.

Mueller on internal linking: "one of the biggest things that you can do on a website" — see John Mueller on internal linking: "one of the biggest things that you can do on a website". The same logic applies to inbound links from elsewhere — they degrade silently when URLs change.

How to apply:

• Slug taxonomy planned at IA phase, not bolted on later (see Reference: 5 URL structure patterns for multi-vertical IA (A through E), with field-observed usage)
• Every redirect lives in version control alongside the code (htaccess, Nginx conf, Next.js redirects.json — anywhere reviewable)
• Quarterly check: 404 rate trend. Spike = broken inbound links somewhere; fix the redirect
• On rebuild: redirect map is the first deliverable, not the last (see [[sej-892-migrations-523-day-recovery]])