Cookie language preference (oft_lang) overrides Accept-Language; /en/* 301s to unprefixed canonical URLs with Set-Cookie. | Dev Logs

Date: 2026-09-03 19:43 Summary: Cookie language preference (oft_lang) overrides Accept-Language; /en/* 301s to unprefixed canonical URLs with Set-Cookie. Visibility: people

[question] cookie 记住语言偏好：如果用户点击选取语言后，默认此语言。在用户选择英语，或者没有语言偏好设置时候且Accept-Language是英语默认访问链接中无/{lang}/的链接，如果这个用户访问有/en/链接，301跳到无/{lang}/的链接。

[try to solve]

Context

After choosing English via /en/, Tools mega links (unprefixed /tools/...) were re-negotiated by Accept-Language: zh into /zh/tools/.... Product ask: remember explicit language choice in a cookie; English (cookie or AL) stays on unprefixed URLs; visiting /en/... must 301 to the unprefixed canonical and set the preference.

Process

1. Extended src/site/lang.ts with LANG_PREF_COOKIE (oft_lang), parse/get/set helpers, and resolvePreferredLang (cookie > Accept-Language > default).
2. Worker (src/index.ts): early middleware 301-strips default-lang explicit prefixes (/en/... → /...) and Set-Cookie: oft_lang=en. Home / and unprefixed negotiation middleware use resolvePreferredLang with Vary: Accept-Language, Accept, Cookie.
3. toolRegistrar keeps a default-lang /en/tools/:slug → 301 fallback.
4. Lang switcher (scripts/site/components/header.mjs, src/pages/site/header.ts): data-lang-pref on alternate links + click script writes the same cookie (HTTPS adds Secure).
5. Rebuilt home/info Assets HTML so switcher markup/script is live on homes.

Root cause / analysis

Unprefixed English URLs are correct for SEO, but without a durable preference the server kept trusting Accept-Language on every hop. Cookie preference separates “browser default” from “user chose English,” and /en/ becomes a selection signal that consolidates to the canonical unprefixed URL (301) instead of a permanent parallel English tree.

Solution

Verified with GET curl on localhost:8788:

Accept-Language auto-redirects do not write the cookie; only switcher click or /en/ 301 does.

Notes / boundaries

• Paths: src/site/lang.ts, src/index.ts, src/site/toolRegistrar.ts, both header renderers, scripts/site/config.mjs comment.
• Tool-page HTML still needs a full npm run build:site (and local R2 refresh) to embed the click script on prerendered tool chrome; Worker /en/ → cookie already covers the English-selection path without that rebuild.
• Do not treat Accept-Language negotiation as an explicit preference.

[actions]

• Implemented cookie preference + /en/* 301 strip in Worker; updated lang switchers; rebuilt home/info Assets pages