fix(redirects): Restore backend project source maps links

[sansynx]

DESCRIBE YOUR PR

Fixes #17865
Fixes #17859
Fixes #17858

The reported source maps links use Django, PHP, and Rails project names as JavaScript guide names. All three return 404. This redirects those exact URLs to the JavaScript source maps guide, which returns 200

The three cases share one fix, so they are grouped here. Regression tests exercise the middleware response and check that the destination does not redirect again. All 82 middleware and redirect-tooling tests pass

This repairs the docs URLs only, not the code that generates links in the Sentry application. Vercel preview review is still pending

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PRE-MERGE CHECKLIST

Make sure you've checked the following before merging your changes:

• Checked Vercel preview for correctness, including links
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LEGAL BOILERPLATE

Look, I get it. The entity doing business as "Sentry" was incorporated in the State of Delaware in 2015 as Functional Software, Inc. and is gonna need some rights from me in order to utilize my contributions in this here PR. So here's the deal: I retain all rights, title and interest in and to my contributions, and by keeping this boilerplate intact I confirm that Sentry can use, modify, copy, and redistribute my contributions, under Sentry's choice of terms.

EXTRA RESOURCES

• Sentry Docs contributor guide

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[cursor]

The plan checks redirects on the three broken source-map URLs, sibling JavaScript source-map pages, and production errors. An issue escalates when those URLs still fail to redirect or error volume rises above the measured band.

Services: sentry-docs, develop-docs.

Mention @change-monitor in a comment to update the plan.

Plan

What changed

Requests to /platforms/javascript/guides/python-django/sourcemaps/, /platforms/javascript/guides/php/sourcemaps/, and /platforms/javascript/guides/ruby-rails/sourcemaps/ now return 301 to /platforms/javascript/sourcemaps/.
sentry-docs must deploy before this is live. The same middleware.ts file also ships in develop-docs. The new rows sit in USER_DOCS_REDIRECTS and do not apply when developer docs mode is on.
This change targets issues/17865, issues/17859, and issues/17858.

Risk

A bad redirect map can send valid JavaScript guide source-map pages to the wrong URL. A middleware fault can fail every request on both ships.
Existing :guide placeholder rows already send /platforms/javascript/guides/php/sourcemaps/multiple-origins/ to /platforms/javascript/guides/php/sourcemaps/. After this change that chain continues to /platforms/javascript/sourcemaps/.

Intended effect

The new behavior is a 301 on those three paths. absent looks like those paths still logged as middleware passthrough while redirect spans on those paths stay at zero.

Signal	Baseline	Rule	Source
Redirect spans for the three broken paths	0 spans in 7d	Rise above 0 after deploy	Sentry org sentry project docs, environment:production AND middleware.outcome:redirect AND (url.path:"/platforms/javascript/guides/python-django/sourcemaps/" OR url.path:"/platforms/javascript/guides/php/sourcemaps/" OR url.path:"/platforms/javascript/guides/ruby-rails/sourcemaps/"), window 2026-09-27T06:58:42Z to 2026-10-04T06:58:42Z
Passthrough logs for the Django source-map URL	1 info log in 7d	Stay at 0 after deploy	Sentry org sentry project docs, production logs Middleware request processed: /platforms/javascript/guides/python-django/sourcemaps/, window 2026-09-27T06:58:42Z to 2026-10-04T06:58:42Z. Fixes issues/17865
Passthrough logs for the PHP source-map URL	1 info log in 7d	Stay at 0 after deploy	Sentry org sentry project docs, production logs Middleware request processed: /platforms/javascript/guides/php/sourcemaps/, window 2026-09-27T06:58:42Z to 2026-10-04T06:58:42Z. Fixes issues/17859
Passthrough logs for the Rails source-map URL	1 info log in 7d	Stay at 0 after deploy	Sentry org sentry project docs, production logs Middleware request processed: /platforms/javascript/guides/ruby-rails/sourcemaps/, window 2026-09-27T06:58:42Z to 2026-10-04T06:58:42Z. Fixes issues/17858

Those three logs all occurred at 2026-10-04T06:45:03Z to 2026-10-04T06:45:04Z. After deploy, handleRedirects returns before that log. Redirect spans on those paths must rise above zero if traffic continues.

Regression watch

A broken redirect table can widen to valid JavaScript guide source-map pages or fail middleware for every request. Watch errors first. Then watch redirect volume and sibling source-map pages.

Signal	Baseline	Rule	Source
Production errors on docs	0-15 events/h, 59 events in 24h	Hold in 0-15/h. Escalate if the rate rises above 15/h	Sentry org sentry project docs, environment:production error count, window 2026-10-03T06:58:42Z to 2026-10-04T06:58:42Z
Middleware redirect spans	200-1300 spans/h, 12900 spans in 24h	Hold in 200-1300/h. Escalate if volume collapses below 200/h or rises above 1300/h	Sentry org sentry project docs, environment:production middleware.outcome:redirect, window 2026-10-03T06:58:42Z to 2026-10-04T06:58:42Z
React JavaScript source-map page spans	0-100 spans/h, 313 spans in 24h	Hold in 0-100/h. Escalate if this path goes quiet across a full 24h	Sentry org sentry project docs, environment:production url.path:"/platforms/javascript/guides/react/sourcemaps/", window 2026-10-03T06:58:42Z to 2026-10-04T06:58:42Z
Production errors on develop-docs	0-3 events/h, 12 events in 24h	Hold in 0-3/h. Escalate if the rate rises above 3/h	Sentry org sentry project develop-docs, environment:production error count, window 2026-10-03T06:58:42Z to 2026-10-04T06:58:42Z

If error volume rises, check whether valid /platforms/javascript/guides/*/sourcemaps/ paths now redirect. Node, React, and Next.js source-map pages had traffic in this window.

Not observable

HTTP 404 and 301 status codes for the three broken URLs are not in traces. A 24h query for http.status_code:404 on /platforms/javascript/* returned 0.
Middleware root spans sample at 1%. Rare hits may not create redirect spans even when the 301 works. Use the passthrough logs for path hits.

[coolguyzone]

LGTM, thanks so much for fixing this @sansynx!

[vercel]

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Project	Deployment	Actions	Updated
develop-docs	Ready	Preview	Oct 8, 2026 9:20pm UTC
sentry-docs	Ready	Preview	Oct 8, 2026 9:20pm UTC