fix(i18n): only trigger fallback for 404 responses#15704
Merged
ematipico merged 1 commit intowithastro:mainfrom Mar 2, 2026
Merged
fix(i18n): only trigger fallback for 404 responses#15704ematipico merged 1 commit intowithastro:mainfrom
ematipico merged 1 commit intowithastro:mainfrom
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The i18n fallback middleware was incorrectly intercepting all responses with status >= 300, including legitimate 3xx redirects, 403 forbidden, and 5xx server errors. This caused auth flows and form submissions on localized server routes to be incorrectly redirected to fallback locales. Changed the condition to only trigger fallback for 404 (page not found) responses, which is the intended behavior — fallback should only activate when a page doesn't exist in the requested locale. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Merging this PR will improve performance by 10.8%
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Summary
Fixes #15688
The i18n fallback middleware was incorrectly intercepting all responses with
status >= 300(inredirectToFallback) andstatus < 300as the pass-through gate (incomputeFallbackRoute). This caused legitimate 3xx redirects, 403 forbidden, and 5xx server errors on localized routes to be incorrectly redirected/rewritten to fallback locales.Impact: Auth flows returning 302 redirects, form submissions returning 303 See Other, and API routes returning 500 errors on localized server routes were all being caught by the fallback middleware and redirected to fallback locale URLs.
Changes
packages/astro/src/i18n/index.ts(line 375):response.status >= 300→response.status === 404packages/astro/src/i18n/fallback.ts(line 58):responseStatus < 300(pass-through) →responseStatus !== 404(only 404 triggers fallback)Test plan
fallback.test.js— added tests for 301, 302, 403, 500 all returningnone(no fallback)manual-routing.test.js— 3xx/4xx(non-404)/5xx now correctly return original response unchanged