[coolguyzone]

DESCRIBE YOUR PR

Fixes #20226.

When no platform is active, PlatformLink points at /platform-redirect/?next=<encoded path>. sanitizeNext returned only url.pathname, so the anchor was dropped from both the redirect and the links on the selection page. Around 770 PlatformLink uses carry an anchor.

Reproduced before the fix:

$ curl -sI '.../platform-redirect/?next=/configuration/options/%23tracing-options&platform=python'
HTTP/2 307
location: /platforms/python//configuration/options/     ← no fragment, and a double slash

The fragment can't just be appended to the returned path — page.tsx feeds that value into nodeForPath(...pathname.split('/')), so a #frag segment would break doc tree resolution and fall through to "We couldn't find documentation for this path". So the path and the fragment are now returned separately, and only the two URL-building sites append the fragment.

• sanitizeNext returns {pathname, hash}; every doc tree lookup keeps using pathname alone
• Fragments are allowlisted (/^#[\w.-]+$/, which covers slugs like godot_logger.event_mask); an unrecognized fragment is dropped rather than failing the whole redirect
• Adds platformUrlFor, which joins the platform URL with the path without leaving the // that made every platform redirect 308 a second time
• Drive-by: four PlatformLinks had a trailing slash appended after the fragment by older trailing-slash tooling, so their anchors matched nothing. The two Flutter ones also pointed through a redirect at an id that no longer exists, and now go straight to /debug-symbols/#when-to-upload-debug-symbols

Security

The existing hardening is deliberately untouched — the colon guard still runs on the whole decoded string before parsing (so javascript:/data: are still rejected), the origin check is unchanged, and a fragment is only ever appended to a doc-tree-resolved URL, so it can't influence the origin. New tests cover /a/#@example.com and /a/#//example.com being dropped, plus %2523 double-encoding.

Verification

• 516/516 vitest tests pass (25 in utils.spec.ts, up from 16)
• tsc, eslint and prettier clean
• pnpm lint:trailing-slash clean — the current linter is already fragment-aware, so the four fixed anchors don't regress

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PRE-MERGE CHECKLIST

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• Checked Vercel preview for correctness, including links
• PR was reviewed and approved by any necessary SMEs (subject matter experts)
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Project	Deployment	Actions	Updated
develop-docs	Ready	Preview	Oct 26, 2026 6:34pm UTC
sentry-docs	Ready	Preview	Oct 26, 2026 6:34pm UTC

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Monitoring services · Rollout details

Status	Service	Environment
🔵 Deployed	develop-docs	production
🔵 Deployed	sentry-docs	production

Mention @rollout in a comment to update the plan.

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Verified in production

• Heading-fragment picker requests kept returning 200, and the route had no errors.
• Heading-link picker requests stayed successful.