Mistake: a URL pattern that changes when the source data changes

Mistake: a URL pattern that changes when the source data changes

If the slug is built from a mutable field — a company's display name, a re-orderable category — then a rename silently changes the URL, orphaning the old one and creating a duplicate. At scale this manufactures thousands of soft-404s.

Stable-URL SOP:
— Step 1. Owner: dev. Slugs derive from an immutable id or a frozen slug column, never from a field users can edit.
— Step 2. Owner: dev. On any name change, keep the original slug and 301 only via an explicit, logged redirect — never by re-slugging in place.
— Step 3. Owner: SEO. Diff this build's URL set against last build's. Gate: any URL that disappeared must have a 301, or the build fails.
— Step 4. Owner: data. Store slug_history so old URLs always resolve.

Guardrail: URLs are append-only; you add and redirect, you never silently mutate.

Ship gate: don't publish until all boxes are checked.