feat/redirects: Apply heading (#fragment) redirects in the browser

[marcleblanc2]

Problem

src/data/redirects.ts contains 386 entries whose source includes a #fragment, e.g.

{source: '/cody/quickstart#introduction', destination: '/cody/quickstart#cody-quickstart'}

Browsers never send the fragment to the server, so src/middleware.ts (which matches r.source === pathname) has never fired for any of them — and neither did the Next redirects() config they were originally added to in 2023. Verified on the live site: https://sourcegraph.com/docs/batch_changes/explanations/permissions_in_batch_changes#code-host-interactions-in-batch-changes serves the not-found page with no Location header.

This also means there has been no way to add a redirect when renaming a heading, so inbound anchored links silently break.

Change

• src/components/FragmentRedirect.tsx: client component rendered once in the root layout. After load (and on hashchange) it looks up pathname + location.hash in the # entries of the same redirects list. Same-page hit → history.replaceState + scroll to the new heading (no reload). Cross-page hit → location.replace. It also handles the two-step case where the middleware redirects the path and the browser carries a stale fragment onto the new page.
• src/data/redirects.ts: exported as ESM (export const updatedRedirectsData) so the middleware and the client component import the same list. No entries were moved, added, or removed. Added a header comment explaining which entries are handled where.
• src/middleware.ts: require → import. Behaviour unchanged.

Heading renames are now handled by adding one line to the existing list: {source: '/page#old-heading', destination: '/page#new-heading'}.

Verification (dev server, headless Chromium)

Requested URL	Landed on
/batch_changes/explanations/permissions_in_batch_changes#code-host-interactions-in-batch-changes (404 today)	/batch-changes/permissions-in-batch-changes#code-host-interactions-in-batch-changes, scrolled to heading
/cody/quickstart#introduction (same-page rename)	/cody/quickstart#cody-quickstart, no reload, scrolled to heading
/cody/clients/install-vscode#requirements (what the browser lands on after the middleware's 307 from /cody/overview/install-vscode#requirements)	/cody/clients/install-vscode#prerequisites
/cody/quickstart#prerequisites (valid anchor, control)	unchanged
/admin/http_https_configuration (middleware path redirect, control)	307 → /self-hosted/http-https-configuration

eslint clean on changed files; node dev/check-links.mjs passes; tsc errors are pre-existing (contentlayer/generated).

Notes / follow-ups (not in this PR)

• The # entries now ship to the client as part of the redirects chunk (~15 KB compressed, cached across pages). Most of the 386 point at long-gone Cody pages and could be pruned.
• The bare /batch_changes/explanations/permissions_in_batch_changes (no anchor) still 404s; it needs a fragment-less entry.
• 203 duplicate sources and 108 entries whose destination no longer exists were found while auditing; separate cleanup.
• Pre-existing: createRedirectUrl hardcodes /docs, so middleware redirects 404 in local dev; notFound() pages return HTTP 200 in production.

Amp threads

• Redirect list cleanup

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Project	Deployment	Actions	Updated
sourcegraph-docs	Ready	Preview	Sep 8, 2026 1:40am UTC