diff --git a/eleventy.config.js b/eleventy.config.js
index 69513a5..1d1d2a3 100644
--- a/eleventy.config.js
+++ b/eleventy.config.js
@@ -1,4 +1,6 @@
-const { I18nPlugin } = require("@11ty/eleventy");
+const {
+    I18nPlugin
+} = require("@11ty/eleventy");
 const i18n = require("eleventy-plugin-i18n");
 const eleventySass = require("eleventy-sass");
 const toml = require("@iarna/toml");
@@ -6,9 +8,9 @@ const toml = require("@iarna/toml");
 const fs = require("fs");
 const path = require("path");
 
-module.exports = function(eleventyConfig) {
+module.exports = function (eleventyConfig) {
     eleventyConfig.setLayoutsDirectory("_layouts");
-    
+
     eleventyConfig.addPassthroughCopy("img");
     eleventyConfig.addPassthroughCopy("css/fonts");
     eleventyConfig.addPassthroughCopy("js");
@@ -16,9 +18,15 @@ module.exports = function(eleventyConfig) {
     eleventyConfig.addPassthroughCopy("robots.txt");
     eleventyConfig.addPassthroughCopy("roms");
 
+    const defaultLanguage = "en";
+    // expose as global site data for templates
+    eleventyConfig.addGlobalData("site", {
+        defaultLocale: defaultLanguage
+    });
+
     eleventyConfig.addNunjucksFilter("values", obj => Object.values(obj));
 
-    eleventyConfig.addFilter("i18n_filter", function(collection, limit = null) {
+    eleventyConfig.addFilter("i18n_filter", function (collection, limit = null) {
         const lang = this.page.lang; // access page.lang from context
         let filtered = collection.filter(item => item.data.lang === lang);
         if (limit !== null) {
@@ -29,8 +37,8 @@ module.exports = function(eleventyConfig) {
 
     eleventyConfig.addPlugin(eleventySass);
     eleventyConfig.addPlugin(I18nPlugin, {
-        defaultLanguage: "en",
-        errorMode: "allow-fallback" // /en/ -> /
+        defaultLanguage: defaultLanguage,
+        errorMode: "allow-fallback", // /en/ -> /
     });
     eleventyConfig.addDataExtension("toml", (contents) => toml.parse(contents));
 
@@ -40,6 +48,94 @@ module.exports = function(eleventyConfig) {
     );
     const translations = toml.parse(translationsToml);
 
+    const LOCALE_URL_DEBUG = process.env.LOCALE_URL_DEBUG === "1" || process.env.LOCALE_URL_DEBUG === "true";
+
+    eleventyConfig.addNunjucksFilter("locale_url_resolve", function (targetUrl, desiredLocale) {
+        const ctx = (this && this.ctx) ? this.ctx : {};
+        const collections = (ctx.collections) ? ctx.collections : {};
+        const all = collections.all || [];
+
+        if (!targetUrl || typeof targetUrl !== "string") return targetUrl;
+        if (!targetUrl.startsWith("/")) return targetUrl; // external or relative link -> leave as is
+
+        // determine locale to resolve to
+        const pageLang = desiredLocale || (ctx.page && ctx.page.lang) || ctx.locale || defaultLanguage;
+
+        if (LOCALE_URL_DEBUG) {
+            console.warn(`[locale_url_resolve] resolving targetUrl="${targetUrl}" desiredLocale="${desiredLocale}" pageLang="${pageLang}"`);
+        }
+
+        // if requested locale is default, return the raw url (your default publishes to root)
+        if (pageLang === defaultLanguage) {
+            if (LOCALE_URL_DEBUG) console.warn(`[locale_url_resolve] requested locale is default (${defaultLanguage}) — returning raw URL "${targetUrl}"`);
+            return targetUrl;
+        }
+
+        // normalize targetUrl to ensure trailing slash for comparison
+        const normUrl = targetUrl.endsWith("/") ? targetUrl : (targetUrl + "/");
+
+        // try to find the canonical (default language) page corresponding to targetUrl
+        let canonical = all.find(p => {
+            return (p.url === normUrl || p.url === targetUrl) && p.data && p.data.lang === defaultLanguage;
+        });
+
+        // if not found, try to find any page with that url (maybe targetUrl already localized)
+        if (!canonical) {
+            canonical = all.find(p => (p.url === normUrl || p.url === targetUrl));
+        }
+
+        if (LOCALE_URL_DEBUG) {
+            if (canonical) {
+                const cs = (canonical.page && canonical.page.filePathStem) ? canonical.page.filePathStem : "(no stem)";
+                const clang = (canonical.data && canonical.data.lang) ? canonical.data.lang : "(no lang)";
+                console.warn(`[locale_url_resolve] canonical found: url="${canonical.url}" filePathStem="${cs}" lang="${clang}"`);
+            } else {
+                console.warn(`[locale_url_resolve] canonical NOT found for targetUrl="${targetUrl}". Will fallback to prefixed URL.`);
+            }
+        }
+
+        // if cannot find canonical page, fall back to a prefixed URL (best effort)
+        if (!canonical) {
+            const fallback = (`/${pageLang}${targetUrl}`).replace(/\/{2,}/g, "/");
+            if (LOCALE_URL_DEBUG) console.warn(`[locale_url_resolve] fallback -> "${fallback}"`);
+            return fallback;
+        }
+
+        // determine canonical filePathStem (the source input path without extension)
+        const canonicalLang = canonical.data && canonical.data.lang ? canonical.data.lang : defaultLanguage;
+        const canonicalStem = (canonical.page && canonical.page.filePathStem) ? canonical.page.filePathStem : "";
+
+        // remove the canonical lang prefix from the stem to create a "key" we can match across locales.
+        // e.g. "/en/about" -> "/about", "/es/about" -> "/about"
+        const key = canonicalStem.replace(new RegExp(`^/${canonicalLang}`), "").replace(/^\/+/, "");
+
+        if (LOCALE_URL_DEBUG) {
+            console.warn(`[locale_url_resolve] canonicalLang="${canonicalLang}" canonicalStem="${canonicalStem}" key="${key}"`);
+        }
+
+        // find the localized page whose filePathStem ends with that key and whose lang matches pageLang.
+        const localized = all.find(p => {
+            const pLang = p.data && p.data.lang;
+            const pStem = (p.page && p.page.filePathStem) ? p.page.filePathStem : "";
+            // be defensive: ensure pLang exists
+            if (!pLang) return false;
+            return pLang === pageLang && pStem.endsWith(key);
+        });
+
+        if (localized && localized.url) {
+            if (LOCALE_URL_DEBUG) {
+                const ls = (localized.page && localized.page.filePathStem) ? localized.page.filePathStem : "(no stem)";
+                console.warn(`[locale_url_resolve] localized found: url="${localized.url}" filePathStem="${ls}" lang="${localized.data.lang}"`);
+            }
+            return localized.url;
+        }
+
+        // no localized page found — fall back to prefixed path
+        const fallback2 = (`/${pageLang}${targetUrl}`).replace(/\/{2,}/g, "/");
+        if (LOCALE_URL_DEBUG) console.warn(`[locale_url_resolve] localized NOT found for key="${key}" — fallback -> "${fallback2}"`);
+        return fallback2;
+    });
+
     eleventyConfig.addPlugin(i18n, {
         translations,
         fallbackLocales: {