diff --git a/.gitignore b/.gitignore
index f434856..1211bfe 100644
--- a/.gitignore
+++ b/.gitignore
@@ -27,4 +27,7 @@ bun.lock
 pnpm-lock.yaml
 
 # wrangler
-.wrangler/
\ No newline at end of file
+.wrangler/
+
+# pnpm workspace
+pnpm-workspace.yaml
\ No newline at end of file
diff --git a/public/404.png b/public/404.png
new file mode 100644
index 0000000..9b626fe
Binary files /dev/null and b/public/404.png differ
diff --git a/src/components/editor/CodeEditor.astro b/src/components/editor/CodeEditor.astro
index 9dd1f99..3e7ea38 100644
--- a/src/components/editor/CodeEditor.astro
+++ b/src/components/editor/CodeEditor.astro
@@ -24,11 +24,10 @@ const { slug, initialCode = 'fn main() {\n    println!("Hola, mundo!");\n}\n' }
   import { basicSetup } from "codemirror";
   import { indentWithTab } from "@codemirror/commands";
   import { gruvbox } from "~/components/editor/theme";
-  import { db, editorCode } from "~/lib/stores/editor-store";
+  import { editorCode } from "~/lib/stores/editor-store";
   import { rust } from "~/components/editor/config";
 
   let editorView: EditorView | null = null;
-  let saveTimeout: number | undefined;
 
   async function initEditor() {
     const editorElement = document.getElementById("editor");
@@ -44,7 +43,7 @@ const { slug, initialCode = 'fn main() {\n    println!("Hola, mundo!");\n}\n' }
       initialCode: string;
     };
 
-    const initialDoc = (await db.getCode(slug)) ?? initialCode;
+    const initialDoc = initialCode;
 
     editorView = new EditorView({
       state: EditorState.create({
@@ -58,11 +57,6 @@ const { slug, initialCode = 'fn main() {\n    println!("Hola, mundo!");\n}\n' }
             if (update.docChanged) {
               const value = update.state.doc.toString();
               editorCode.set(value);
-              clearTimeout(saveTimeout);
-              saveTimeout = window.setTimeout(
-                () => db.saveCode(slug, value),
-                500,
-              );
             }
           }),
         ],
@@ -89,7 +83,6 @@ const { slug, initialCode = 'fn main() {\n    println!("Hola, mundo!");\n}\n' }
   document.addEventListener("astro:page-load", initEditor);
 
   document.addEventListener("astro:before-swap", () => {
-    clearTimeout(saveTimeout);
     window.removeEventListener("editor:reset", handleReset);
 
     if (editorView) {
diff --git a/src/components/editor/output/Terminal.astro b/src/components/editor/output/Terminal.astro
index 00cb371..24687dd 100644
--- a/src/components/editor/output/Terminal.astro
+++ b/src/components/editor/output/Terminal.astro
@@ -1,4 +1,5 @@
 ---
+import { getLangFromUrl, useTranslations } from "~/i18n/utils"
 import IconLoader2 from "~icons/tabler/loader-2"
 import IconPlayerPlay from "~icons/tabler/player-play"
 import IconRestore from "~icons/tabler/restore"
@@ -11,6 +12,8 @@ interface Props {
 
 const { expectedOutput, testCode } = Astro.props
 const isTestMode = !!testCode
+const lang = getLangFromUrl(Astro.url)
+const t = useTranslations(lang)
 ---
 
 <terminal-output
@@ -41,22 +44,22 @@ const isTestMode = !!testCode
 				id="btn-reset"
 				class="btn-control hover:text-yellow"
 				type="button"
-				aria-label="Reset code"
+				aria-label={t("editor.reset")}
 			>
 				<IconRestore font-size={14} />
-				<span>Reiniciar</span>
+				<span>{t("editor.reset")}</span>
 			</button>
 
 			<button
 				id="btn-run"
 				class="btn-control hover:text-green-500"
 				type="button"
-				aria-label="Run code"
+				aria-label={t("editor.run")}
 			>
 				<IconPlayerPlay class="group-data-running:hidden" font-size={14} />
 				<IconLoader2 class="hidden animate-spin group-data-running:block" font-size={14} />
-				<span class="group-data-running:hidden">Ejecutar</span>
-				<span class="hidden group-data-running:inline">Ejecutando...</span>
+				<span class="group-data-running:hidden">{t("editor.run")}</span>
+				<span class="hidden group-data-running:inline">{t("editor.running")}</span>
 			</button>
 		</div>
 	</header>
@@ -78,22 +81,22 @@ const isTestMode = !!testCode
 			<button
 				id="btn-reset-mobile"
 				type="button"
-				aria-label="Reset code"
+				aria-label={t("editor.reset")}
 				class="flex-1 flex items-center justify-center gap-2 py-3 text-sm text-secondary/60 border-r border-stroke-color hover:bg-stroke-color/20 active:bg-stroke-color/40 transition-colors cursor-pointer touch-manipulation"
 			>
 				<IconRestore font-size={18} />
-				<span>Reiniciar</span>
+				<span>{t("editor.reset")}</span>
 			</button>
 			<button
 				id="btn-run-mobile"
 				type="button"
-				aria-label="Run code"
+				aria-label={t("editor.run")}
 				class="flex-1 flex items-center justify-center gap-2 py-3 text-sm text-green-400 hover:bg-green-500/10 active:bg-green-500/20 transition-colors cursor-pointer touch-manipulation"
 			>
 				<IconPlayerPlay class="group-data-running:hidden" font-size={18} />
 				<IconLoader2 class="hidden animate-spin group-data-running:block" font-size={18} />
-				<span class="group-data-running:hidden">Ejecutar</span>
-				<span class="hidden group-data-running:inline">Ejecutando...</span>
+				<span class="group-data-running:hidden">{t("editor.run")}</span>
+				<span class="hidden group-data-running:inline">{t("editor.running")}</span>
 			</button>
 		</div>
 		<div class="hidden items-center gap-2 border-t border-stroke-color px-3 py-2 group-data-running:flex">
diff --git a/src/const/tracks.ts b/src/const/tracks.ts
index 3e8b902..6527a85 100644
--- a/src/const/tracks.ts
+++ b/src/const/tracks.ts
@@ -1,4 +1,31 @@
-import type { Track } from "~/entities/track"
+import type { Track, TrackI18n } from "~/entities/track"
+
+export const tracksI18n: Record<string, TrackI18n> = {
+	"fundamentos-de-rust": {
+		es: {
+			title: "Fundamentos de Rust",
+			description:
+				"Aprende Rust desde los fundamentos: sintaxis, ownership, borrowing y más. Ideal si nunca has programado en Rust.",
+		},
+		en: {
+			title: "Rust Fundamentals",
+			description:
+				"Learn Rust from the ground up: syntax, ownership, borrowing and more. Ideal if you've never programmed in Rust.",
+		},
+	},
+	"rust-avanzado-diseno-abstraccion": {
+		es: {
+			title: "Rust Avanzado: Diseño y Abstracción",
+			description:
+				"Profundiza en Rust con temas avanzados como lifetimes, traits, macros y programación asíncrona. Ideal para quienes ya conocen los fundamentos.",
+		},
+		en: {
+			title: "Advanced Rust: Design and Abstraction",
+			description:
+				"Deep dive into Rust with advanced topics like lifetimes, traits, macros and async programming. Ideal for those who already know the fundamentals.",
+		},
+	},
+}
 
 export const tracks: Track[] = [
 	{
diff --git a/src/entities/track.ts b/src/entities/track.ts
index f2e5007..1a007e4 100644
--- a/src/entities/track.ts
+++ b/src/entities/track.ts
@@ -1,5 +1,16 @@
 export type TrackBadgeKey = "track.badge.beginner" | "track.badge.advanced"
 
+export type TrackI18n = {
+	es: {
+		title: string
+		description: string
+	}
+	en: {
+		title: string
+		description: string
+	}
+}
+
 export type Track = {
 	id: string
 	title: string
diff --git a/src/features/content/components/NavButtons.astro b/src/features/content/components/NavButtons.astro
index 02516a4..d9ed6c5 100644
--- a/src/features/content/components/NavButtons.astro
+++ b/src/features/content/components/NavButtons.astro
@@ -1,4 +1,5 @@
 ---
+import { getLangFromUrl, useTranslations } from "~/i18n/utils"
 import IconLeft from "~icons/tabler/arrow-big-left-lines-filled"
 import IconRight from "~icons/tabler/arrow-big-right-lines-filled"
 
@@ -9,6 +10,7 @@ interface Props {
 }
 
 const { lang, previous, next } = Astro.props
+const t = useTranslations(lang as "es" | "en")
 const isNextDisabled = true
 
 const btnBaseClass =
@@ -21,7 +23,7 @@ const iconBaseClass = "block h-6 w-6 rounded-lg transition-all duration-200 tran
 <nav class="not-prose mt-auto flex w-full items-center justify-between pb-2" aria-label="Navegación de lecciones">
   <a
     href={previous ? `/${lang}/${previous.slug}` : undefined}
-    aria-label={previous ? `Anterior: ${previous.title}` : undefined}
+    aria-label={previous ? `${t("nav.previous")}: ${previous.title}` : undefined}
     aria-disabled={!previous}
     class={btnBaseClass}
   >
@@ -30,7 +32,7 @@ const iconBaseClass = "block h-6 w-6 rounded-lg transition-all duration-200 tran
     </span>
     <div class="flex flex-col text-left">
       <span class:list={["text-md font-medium", previous ? "text-yellow" : "text-[#ccc]"]}>
-        Anterior
+        {t("nav.previous")}
       </span>
       <span class="text-xs text-[#ccc]">{previous?.title || "-"}</span>
     </div>
@@ -38,13 +40,13 @@ const iconBaseClass = "block h-6 w-6 rounded-lg transition-all duration-200 tran
   <a
     id="next-lesson-btn"
     href={next ? `/${lang}/${next.slug}` : undefined}
-    aria-label={next ? `Siguiente: ${next.title}` : undefined}
+    aria-label={next ? `${t("nav.next")}: ${next.title}` : undefined}
     aria-disabled={isNextDisabled}
     class={nextBtnClass}
   >
     <div class="flex flex-col text-right">
       <span class:list={["text-md font-medium", next ? "text-yellow" : "text-[#ccc]"]}>
-        Siguiente
+        {t("nav.next")}
       </span>
       <span class="text-xs text-[#ccc]">{next?.title || "-"}</span>
     </div>
@@ -57,6 +59,7 @@ const iconBaseClass = "block h-6 w-6 rounded-lg transition-all duration-200 tran
 <script>
   import { db } from "~/lib/stores/editor-store"
   import { toast } from "~/utils/toasts"
+  import { useTranslations, getLangFromUrl } from "~/i18n/utils"
 
   const initNextButton = async () => {
     const btn = document.getElementById("next-lesson-btn") as HTMLAnchorElement | null
@@ -65,9 +68,11 @@ const iconBaseClass = "block h-6 w-6 rounded-lg transition-all duration-200 tran
     btn.addEventListener("click", (e) => {
       if (btn.ariaDisabled === "true") {
         e.preventDefault()
+        const currentLang = getLangFromUrl(new URL(window.location.href))
+        const t = useTranslations(currentLang)
         toast.info(
-          "Ejecuta el código",
-          "El código debe ser ejecutado al menos una vez para poder avanzar a la siguiente sección",
+          t("toast.run_required_title"),
+          t("toast.run_required_desc"),
         )
       }
     })
diff --git a/src/features/content/components/Navbar.astro b/src/features/content/components/Navbar.astro
index 0c8c02c..e020bf2 100644
--- a/src/features/content/components/Navbar.astro
+++ b/src/features/content/components/Navbar.astro
@@ -127,8 +127,8 @@ const sidebarItems = [...groupMap.values()].map(({ parent, children }) => ({
     // Setup reactive navbar (this handles all user state changes automatically)
     setupNavbar({
       profileLinkId: "nav-profile-link",
-      loginLinkId: null, // This navbar doesn't have a login link
-      logoutLinkId: null // This navbar doesn't have a logout link directly
+      loginLinkId: undefined,
+      logoutLinkId: undefined
     })
     
     // Update username in profile link dynamically by targeting the span
diff --git a/src/features/home/components/Community.astro b/src/features/home/components/Community.astro
index f0e2192..90cfc63 100644
--- a/src/features/home/components/Community.astro
+++ b/src/features/home/components/Community.astro
@@ -13,7 +13,7 @@ interface Props {
 }
 
 const { lang: langProp } = Astro.props
-const lang = langProp ?? getLangFromUrl(Astro.url)
+const lang = (langProp ?? getLangFromUrl(Astro.url)) as "es" | "en"
 const t = useTranslations(lang)
 ---
 
diff --git a/src/features/home/components/FAQ.astro b/src/features/home/components/FAQ.astro
index 8e5a0a0..7a32ad2 100644
--- a/src/features/home/components/FAQ.astro
+++ b/src/features/home/components/FAQ.astro
@@ -8,7 +8,7 @@ interface Props {
 }
 
 const { lang: langProp } = Astro.props
-const lang = langProp ?? getLangFromUrl(Astro.url)
+const lang = (langProp ?? getLangFromUrl(Astro.url)) as "es" | "en"
 const t = useTranslations(lang)
 
 const faqs = [
diff --git a/src/features/home/components/Features.astro b/src/features/home/components/Features.astro
index 956c810..1f56fc4 100644
--- a/src/features/home/components/Features.astro
+++ b/src/features/home/components/Features.astro
@@ -14,7 +14,7 @@ interface Props {
 }
 
 const { lang: langProp } = Astro.props
-const lang = langProp ?? getLangFromUrl(Astro.url)
+const lang = (langProp ?? getLangFromUrl(Astro.url)) as "es" | "en"
 const t = useTranslations(lang)
 ---
 
diff --git a/src/features/home/components/Hero.astro b/src/features/home/components/Hero.astro
index 46f0d29..302fbd4 100644
--- a/src/features/home/components/Hero.astro
+++ b/src/features/home/components/Hero.astro
@@ -16,7 +16,7 @@ interface Props {
 
 const { lang: langProp } = Astro.props
 const user = Astro.locals.user
-const lang = langProp ?? getLangFromUrl(Astro.url)
+const lang = (langProp ?? getLangFromUrl(Astro.url)) as "es" | "en"
 const t = useTranslations(lang)
 ---
 
diff --git a/src/features/home/components/HowItWorks.astro b/src/features/home/components/HowItWorks.astro
index 612a1b9..9ebdf91 100644
--- a/src/features/home/components/HowItWorks.astro
+++ b/src/features/home/components/HowItWorks.astro
@@ -17,7 +17,7 @@ interface Props {
 }
 
 const { lang: langProp } = Astro.props
-const lang = langProp ?? getLangFromUrl(Astro.url)
+const lang = (langProp ?? getLangFromUrl(Astro.url)) as "es" | "en"
 const t = useTranslations(lang)
 
 const topics = [
diff --git a/src/features/home/components/Playground.astro b/src/features/home/components/Playground.astro
index 64fae39..acff546 100644
--- a/src/features/home/components/Playground.astro
+++ b/src/features/home/components/Playground.astro
@@ -10,7 +10,7 @@ interface Props {
 }
 
 const { lang: langProp } = Astro.props
-const lang = langProp ?? getLangFromUrl(Astro.url)
+const lang = (langProp ?? getLangFromUrl(Astro.url)) as "es" | "en"
 const t = useTranslations(lang)
 ---
 
diff --git a/src/i18n/keys/en.keys.ts b/src/i18n/keys/en.keys.ts
index 184c5ea..d179cfc 100644
--- a/src/i18n/keys/en.keys.ts
+++ b/src/i18n/keys/en.keys.ts
@@ -364,4 +364,32 @@ export const en_keys = {
 	"learn.lessons": "lessons",
 	"learn.progress_of": "of",
 	"learn.continue_label": "Continue:",
+
+	// Editor/Terminal buttons
+	"editor.reset": "Reset",
+	"editor.run": "Run",
+	"editor.running": "Running...",
+	"editor.output_label": "Output",
+
+	// Navigation buttons
+	"nav.previous": "Previous",
+	"nav.next": "Next",
+	"nav.content": "Content",
+	"nav.code": "Code",
+	"nav.terminal": "Terminal",
+
+	// Lesson page
+	"lesson.tab_content": "Content",
+	"lesson.tab_editor": "Editor",
+	"lesson.tab_terminal": "Terminal",
+
+	// Toasts
+	"toast.run_required_title": "Run the code",
+	"toast.run_required_desc": "Code must be run at least once before moving to the next section",
+	"toast.completed_title": "You did it! 🦀",
+	"toast.completed_desc": "You completed {trackTitle}. Find your certificate in your profile.",
+
+	// Auth
+	"auth.login_required_title": "Login required",
+	"auth.login_required_desc": "You must log in to access the course",
 }
diff --git a/src/i18n/keys/es.keys.ts b/src/i18n/keys/es.keys.ts
index c0d4548..5773549 100644
--- a/src/i18n/keys/es.keys.ts
+++ b/src/i18n/keys/es.keys.ts
@@ -371,4 +371,32 @@ export const es_keys = {
 	"learn.lessons": "lecciones",
 	"learn.progress_of": "de",
 	"learn.continue_label": "Continuar:",
+
+	// Editor/Terminal buttons
+	"editor.reset": "Reiniciar",
+	"editor.run": "Ejecutar",
+	"editor.running": "Ejecutando...",
+	"editor.output_label": "Salida",
+
+	// Navigation buttons
+	"nav.previous": "Anterior",
+	"nav.next": "Siguiente",
+	"nav.content": "Contenido",
+	"nav.code": "Código",
+	"nav.terminal": "Terminal",
+
+	// Lesson page
+	"lesson.tab_content": "Contenido",
+	"lesson.tab_editor": "Editor",
+	"lesson.tab_terminal": "Terminal",
+
+	// Toasts
+	"toast.run_required_title": "Ejecuta el código",
+	"toast.run_required_desc": "El código debe ser ejecutado al menos una vez para poder avanzar a la siguiente sección",
+	"toast.completed_title": "¡Lo lograste! 🦀",
+	"toast.completed_desc": "Completaste {trackTitle}. Encuentra tu certificado en tu perfil.",
+
+	// Auth
+	"auth.login_required_title": "Inicia sesión requerida",
+	"auth.login_required_desc": "Debes iniciar sesión para acceder al curso",
 }
diff --git a/src/lib/auth/crypto.ts b/src/lib/auth/crypto.ts
index 8195aaf..da1c9dc 100644
--- a/src/lib/auth/crypto.ts
+++ b/src/lib/auth/crypto.ts
@@ -21,12 +21,12 @@ export async function hashPassword(password: string): Promise<string> {
 	const keyMaterial = await crypto.subtle.importKey("raw", new TextEncoder().encode(password), "PBKDF2", false, [
 		"deriveBits",
 	])
-	const hash = await crypto.subtle.deriveBits(
+	const hash = (await crypto.subtle.deriveBits(
 		{ name: "PBKDF2", salt, iterations: ITERATIONS, hash: "SHA-256" },
 		keyMaterial,
 		HASH_LENGTH * 8,
-	)
-	return `${bufToHex(salt)}:${bufToHex(hash)}`
+	)) as ArrayBuffer
+	return `${bufToHex(salt.buffer)}:${bufToHex(hash)}`
 }
 
 export async function verifyPassword(password: string, stored: string): Promise<boolean> {
@@ -36,16 +36,16 @@ export async function verifyPassword(password: string, stored: string): Promise<
 	const keyMaterial = await crypto.subtle.importKey("raw", new TextEncoder().encode(password), "PBKDF2", false, [
 		"deriveBits",
 	])
-	const hash = await crypto.subtle.deriveBits(
+	const hash = (await crypto.subtle.deriveBits(
 		{ name: "PBKDF2", salt, iterations: ITERATIONS, hash: "SHA-256" },
 		keyMaterial,
 		HASH_LENGTH * 8,
-	)
+	)) as ArrayBuffer
 	return bufToHex(hash) === hashHex
 }
 
 export function generateToken(): string {
-	return bufToHex(crypto.getRandomValues(new Uint8Array(32)))
+	return bufToHex(crypto.getRandomValues(new Uint8Array(32)).buffer)
 }
 
 export function generateId(): string {
diff --git a/src/lib/progress.ts b/src/lib/progress.ts
index cd3a8ca..838636d 100644
--- a/src/lib/progress.ts
+++ b/src/lib/progress.ts
@@ -1,24 +1,11 @@
-const STORAGE_KEY = "rustlings_progress"
-
 type Progress = Record<string, string[]>
 
 export function getProgress(): Progress {
-	try {
-		return JSON.parse(localStorage.getItem(STORAGE_KEY) ?? "{}") as Progress
-	} catch {
-		return {}
-	}
+	return {}
 }
 
-export function markLessonVisited(trackId: string, slug: string): void {
-	const progress = getProgress()
-	const visited = progress[trackId] ?? []
-	if (!visited.includes(slug)) {
-		progress[trackId] = [...visited, slug]
-		localStorage.setItem(STORAGE_KEY, JSON.stringify(progress))
-	}
-}
+export function markLessonVisited(_trackId: string, _slug: string): void {}
 
-export function getTrackProgress(trackId: string): string[] {
-	return getProgress()[trackId] ?? []
+export function getTrackProgress(_trackId: string): string[] {
+	return []
 }
diff --git a/src/lib/stores/auth-store.ts b/src/lib/stores/auth-store.ts
index 448e7f7..5389ef3 100644
--- a/src/lib/stores/auth-store.ts
+++ b/src/lib/stores/auth-store.ts
@@ -81,7 +81,7 @@ export const authActions = {
 		try {
 			const response = await fetch("/api/auth/me")
 			if (response.ok) {
-				const userData = await response.json()
+				const userData = (await response.json()) as { user: SessionUser; full_name_locked: boolean }
 				this.setUser(userData.user, userData.full_name_locked)
 			} else {
 				this.clearUser()
diff --git a/src/lib/stores/editor-store.ts b/src/lib/stores/editor-store.ts
index 0bdabed..893fa93 100644
--- a/src/lib/stores/editor-store.ts
+++ b/src/lib/stores/editor-store.ts
@@ -2,76 +2,11 @@ import { atom } from "nanostores"
 
 export const editorCode = atom("")
 
-class RustlingsDB {
-	private dbPromise: Promise<IDBDatabase> | null = null
-	private readonly DB_VERSION = 1
-	private readonly STORE_CODE = "snippets"
-	private readonly STORE_PROGRESS = "progress"
+// In-memory progress tracking (resets on page reload)
+// Server-side progress is handled via API calls
+class ServerProgressStore {
 	lastLesson: Record<string, { slug: string; title: string }> = {}
-
-	private initDB(): Promise<IDBDatabase> {
-		if (this.dbPromise) return this.dbPromise
-
-		this.dbPromise = new Promise<IDBDatabase>((resolve, reject) => {
-			const request = indexedDB.open("rustlings", this.DB_VERSION)
-
-			request.onupgradeneeded = (e) => {
-				const db = (e.target as IDBOpenDBRequest).result
-
-				if (!db.objectStoreNames.contains(this.STORE_CODE)) {
-					db.createObjectStore(this.STORE_CODE)
-				}
-
-				if (!db.objectStoreNames.contains(this.STORE_PROGRESS)) {
-					db.createObjectStore(this.STORE_PROGRESS)
-				}
-			}
-
-			request.onsuccess = (e) => resolve((e.target as IDBOpenDBRequest).result)
-			request.onerror = () => reject(new Error("Failed to open IndexedDB"))
-		})
-
-		return this.dbPromise
-	}
-
-	private async get<T>(store: string, key: string): Promise<T | null> {
-		const db = await this.initDB()
-		return new Promise((resolve) => {
-			const request = db.transaction(store, "readonly").objectStore(store).get(key)
-			request.onsuccess = () => resolve(request.result || null)
-			request.onerror = () => resolve(null)
-		})
-	}
-
-	private async set(store: string, key: string, value: unknown): Promise<void> {
-		const db = await this.initDB()
-		return new Promise((resolve, reject) => {
-			const request = db.transaction(store, "readwrite").objectStore(store).put(value, key)
-			request.onsuccess = () => resolve()
-			request.onerror = () => reject(request.error)
-		})
-	}
-
-	private async delete(store: string, key: string): Promise<void> {
-		const db = await this.initDB()
-		return new Promise((resolve, reject) => {
-			const request = db.transaction(store, "readwrite").objectStore(store).delete(key)
-			request.onsuccess = () => resolve()
-			request.onerror = () => reject(request.error)
-		})
-	}
-
-	async saveCode(slug: string, val: string) {
-		await this.set(this.STORE_CODE, slug, val)
-	}
-
-	async getCode(slug: string): Promise<string | null> {
-		return this.get<string>(this.STORE_CODE, slug)
-	}
-
-	async reset(slug: string) {
-		await Promise.all([this.delete(this.STORE_CODE, slug), this.delete(this.STORE_PROGRESS, slug)])
-	}
+	private completedLessons: Set<string> = new Set()
 
 	/** Records that the user visited this lesson (fire-and-forget for logged-in users) */
 	visitLesson(slug: string, courseId: string) {
@@ -84,7 +19,7 @@ class RustlingsDB {
 	}
 
 	async markCompleted(slug: string, courseId?: string) {
-		await this.set(this.STORE_PROGRESS, slug, true)
+		this.completedLessons.add(slug)
 		if (courseId) {
 			fetch("/api/progress/complete", {
 				method: "POST",
@@ -95,24 +30,17 @@ class RustlingsDB {
 	}
 
 	async isCompleted(slug: string): Promise<boolean> {
-		return (await this.get<boolean>(this.STORE_PROGRESS, slug)) || false
+		return this.completedLessons.has(slug)
+	}
+
+	async reset(slug: string) {
+		this.completedLessons.delete(slug)
 	}
 
 	/** Clear all local data (called on logout) */
 	async clearAll(): Promise<void> {
-		const db = await this.initDB()
-		await Promise.all([
-			new Promise<void>((resolve) => {
-				const req = db.transaction(this.STORE_CODE, "readwrite").objectStore(this.STORE_CODE).clear()
-				req.onsuccess = () => resolve()
-				req.onerror = () => resolve()
-			}),
-			new Promise<void>((resolve) => {
-				const req = db.transaction(this.STORE_PROGRESS, "readwrite").objectStore(this.STORE_PROGRESS).clear()
-				req.onsuccess = () => resolve()
-				req.onerror = () => resolve()
-			}),
-		])
+		this.completedLessons.clear()
+		this.lastLesson = {}
 	}
 
 	/** Load server-side completions + last lesson positions into local state (for logged-in users) */
@@ -126,7 +54,7 @@ class RustlingsDB {
 			}
 			for (const slugs of Object.values(progress)) {
 				for (const slug of slugs) {
-					await this.set(this.STORE_PROGRESS, slug, true)
+					this.completedLessons.add(slug)
 				}
 			}
 			this.lastLesson = lastLesson ?? {}
@@ -136,4 +64,4 @@ class RustlingsDB {
 	}
 }
 
-export const db = new RustlingsDB()
+export const db = new ServerProgressStore()
diff --git a/src/lib/stores/user-utils.ts b/src/lib/stores/user-utils.ts
index c8dbf15..6cac8b2 100644
--- a/src/lib/stores/user-utils.ts
+++ b/src/lib/stores/user-utils.ts
@@ -27,7 +27,7 @@ export function getDisplayName(): string {
  * Verifica si el usuario puede editar su nombre
  */
 export function canEditName(): boolean {
-	return authActions.canEditName()
+	return !!authActions.canEditName()
 }
 
 /**
diff --git a/src/pages/[lang]/404.astro b/src/pages/[lang]/404.astro
index a7560a2..e779d80 100644
--- a/src/pages/[lang]/404.astro
+++ b/src/pages/[lang]/404.astro
@@ -1,7 +1,5 @@
 ---
-import { Image } from "astro:assets"
-import img404 from "~/assets/images/webp/404.png"
-import { getLangFromUrl, useTranslations } from "~/i18n/utils"
+import { useTranslations } from "~/i18n/utils"
 import Layout from "~/layouts/Layout.astro"
 import IconLeft from "~icons/tabler/arrow-big-left-lines-filled"
 
@@ -11,14 +9,14 @@ export function getStaticPaths() {
 	return [{ params: { lang: "es" } }, { params: { lang: "en" } }]
 }
 
-const lang = getLangFromUrl(Astro.url)
+const lang = Astro.params.lang as "es" | "en"
 const t = useTranslations(lang)
 ---
 
 <Layout title={t("404.title")}>
   <main class="flex-1 flex flex-col items-center justify-center px-4 gap-8">
-    <Image
-      src={img404}
+    <img
+      src="/404.png"
       alt={t("404.image_alt")}
       class="w-full max-w-lg h-auto select-none pointer-events-none"
     />
diff --git a/src/pages/[lang]/[slug].astro b/src/pages/[lang]/[slug].astro
index 335b77e..629f2ab 100644
--- a/src/pages/[lang]/[slug].astro
+++ b/src/pages/[lang]/[slug].astro
@@ -5,6 +5,7 @@ import { tracks } from "~/const/tracks"
 import { getLessonsByLang, supportedLangs } from "~/content-manager"
 import NavButtons from "~/features/content/components/NavButtons.astro"
 import Navbar from "~/features/content/components/Navbar.astro"
+import { useTranslations } from "~/i18n/utils"
 import Layout from "~/layouts/Layout.astro"
 import IconBook from "~icons/tabler/book"
 import IconChevronDown from "~icons/tabler/chevron-down"
@@ -33,6 +34,11 @@ export function getStaticPaths() {
 
 const { lesson, lang, previousLesson, nextLesson } = Astro.props
 const currentTrack = tracks.find((t) => t.slugs.includes(lesson.meta.slug))
+const t = useTranslations(lang as "es" | "en")
+
+if (!Astro.locals.user) {
+	return Astro.redirect(`/${lang}/login?returnUrl=${encodeURIComponent(Astro.url.pathname)}`)
+}
 ---
 
 <style>
@@ -256,19 +262,19 @@ const currentTrack = tracks.find((t) => t.slugs.includes(lesson.meta.slug))
       class={`flex-1 flex flex-col items-center gap-1 py-2.5 touch-manipulation transition-colors ${!previousLesson ? "text-secondary/20 pointer-events-none" : "text-secondary/40 cursor-pointer hover:text-secondary"}`}
     >
       <IconChevronLeft font-size={20} />
-      <span class="text-[10px] font-medium">Anterior</span>
+      <span class="text-[10px] font-medium">{t("nav.previous")}</span>
     </a>
     <button id="tab-content" class="flex-1 flex flex-col items-center gap-1 py-2.5 text-yellow transition-colors cursor-pointer touch-manipulation">
       <IconBook font-size={20} />
-      <span class="text-[10px] font-medium">Contenido</span>
+      <span class="text-[10px] font-medium">{t("nav.content")}</span>
     </button>
     <button id="tab-editor" disabled={lesson.data.editor === false} class={`flex-1 flex flex-col items-center gap-1 py-2.5 transition-colors cursor-pointer touch-manipulation ${lesson.data.editor === false ? "text-secondary/20 opacity-30" : "text-secondary/40"}`}>
       <IconCode font-size={20} />
-      <span class="text-[10px] font-medium">Código</span>
+      <span class="text-[10px] font-medium">{t("nav.code")}</span>
     </button>
     <button id="tab-terminal" disabled={lesson.data.editor === false} class={`flex-1 flex flex-col items-center gap-1 py-2.5 transition-colors cursor-pointer touch-manipulation ${lesson.data.editor === false ? "text-secondary/20 opacity-30" : "text-secondary/40"}`}>
       <IconTerminal font-size={20} />
-      <span class="text-[10px] font-medium">Terminal</span>
+      <span class="text-[10px] font-medium">{t("nav.terminal")}</span>
     </button>
     <a
       id="mobile-next-btn"
@@ -277,7 +283,7 @@ const currentTrack = tracks.find((t) => t.slugs.includes(lesson.meta.slug))
       class={`flex-1 flex flex-col items-center gap-1 py-2.5 touch-manipulation transition-colors aria-disabled:text-secondary/20 aria-disabled:opacity-50 ${nextLesson ? "text-secondary/40 cursor-pointer hover:text-secondary" : ""}`}
     >
       <IconChevronRight font-size={20} />
-      <span class="text-[10px] font-medium">Siguiente</span>
+      <span class="text-[10px] font-medium">{t("nav.next")}</span>
     </a>
   </nav>
 </Layout>
@@ -316,21 +322,20 @@ const currentTrack = tracks.find((t) => t.slugs.includes(lesson.meta.slug))
 </script>
 
 <script>
-  import { markLessonVisited } from "~/lib/progress"
   import { db } from "~/lib/stores/editor-store"
+  import { useTranslations, getLangFromUrl } from "~/i18n/utils"
 
   document.addEventListener("astro:page-load", async () => {
     const tracker = document.getElementById("lesson-tracker")
     const trackId = tracker?.dataset.trackId ?? "visited"
     const slug = tracker?.dataset.slug ?? window.location.pathname.split("/").pop()
-    if (slug) markLessonVisited(trackId, slug)
+    const currentLang = getLangFromUrl(new URL(window.location.href))
+    const t = useTranslations(currentLang)
 
-    // Track lesson position on server (enables "login anywhere" resume)
     if (slug && trackId !== "visited") {
       db.visitLesson(slug, trackId)
     }
 
-    // Non-editor lessons complete on visit (no exercise to run)
     const isNonEditor = document.querySelector("[data-panel='right']")?.classList.contains("collapsed")
     if (isNonEditor && slug) {
       await db.markCompleted(slug, trackId)
@@ -342,8 +347,12 @@ const currentTrack = tracks.find((t) => t.slugs.includes(lesson.meta.slug))
 <script>
   import { db } from "~/lib/stores/editor-store"
   import { toast } from "~/utils/toasts"
+  import { useTranslations, getLangFromUrl } from "~/i18n/utils"
 
   document.addEventListener("astro:page-load", async () => {
+    const currentLang = getLangFromUrl(new URL(window.location.href))
+    const t = useTranslations(currentLang)
+
     const btn = document.getElementById("mobile-next-btn") as HTMLAnchorElement | null
     if (!btn || !btn.href) return
 
@@ -351,8 +360,8 @@ const currentTrack = tracks.find((t) => t.slugs.includes(lesson.meta.slug))
       if (btn.ariaDisabled === "true") {
         e.preventDefault()
         toast.info(
-          "Ejecuta el código",
-          "El código debe ser ejecutado al menos una vez para poder avanzar a la siguiente sección",
+          t("toast.run_required_title"),
+          t("toast.run_required_desc"),
         )
       }
     })
@@ -384,7 +393,6 @@ const currentTrack = tracks.find((t) => t.slugs.includes(lesson.meta.slug))
       if (resizer.dataset.direction === "vertical" && window.innerWidth < 1024)
         return;
 
-      // Check if editor is disabled by looking for collapsed class on right panel
       const container = resizer.parentElement!;
       const rightPanel =
         container.querySelector<HTMLElement>("[data-panel='right']") ??
@@ -516,29 +524,31 @@ const currentTrack = tracks.find((t) => t.slugs.includes(lesson.meta.slug))
 <script>
   import { toast } from "~/utils/toasts"
   import { db } from "~/lib/stores/editor-store"
+  import { useTranslations, getLangFromUrl } from "~/i18n/utils"
+
+  const shownTrackToasts = new Set<string>()
 
   document.addEventListener("astro:page-load", () => {
     window.addEventListener("lesson:completed", async () => {
       const tracker = document.getElementById("lesson-tracker")
       const trackId = tracker?.dataset.trackId
       const trackTitle = tracker?.dataset.trackTitle ?? "el curso"
+      const currentLang = getLangFromUrl(new URL(window.location.href))
+      const t = useTranslations(currentLang)
       if (!trackId) return
 
-      // Only show once per track
-      const tourKey = `cert-tour-${trackId}`
-      if (localStorage.getItem(tourKey)) return
+      if (shownTrackToasts.has(trackId)) return
 
-      // Check if ALL lessons in this track are now completed
       const trackSlugs: string[] = JSON.parse(tracker?.dataset.trackSlugs ?? "[]")
       if (!trackSlugs.length) return
       const results = await Promise.all(trackSlugs.map((s) => db.isCompleted(s)))
       if (!results.every(Boolean)) return
 
-      localStorage.setItem(tourKey, "1")
+      shownTrackToasts.add(trackId)
 
       toast.success(
-        "¡Lo lograste! 🦀", 
-        `Completaste ${trackTitle}. Encuentra tu certificado en tu perfil.`
+        t("toast.completed_title"),
+        t("toast.completed_desc").replace("{trackTitle}", trackTitle)
       )
     })
   })
diff --git a/src/pages/[lang]/aprender.astro b/src/pages/[lang]/aprender.astro
index 1bc314d..e1eb859 100644
--- a/src/pages/[lang]/aprender.astro
+++ b/src/pages/[lang]/aprender.astro
@@ -1,7 +1,7 @@
 ---
 import { Image } from "astro:assets"
 import logoImage from "~/assets/images/webp/logo.webp"
-import { tracks } from "~/const/tracks"
+import { tracks, tracksI18n } from "~/const/tracks"
 import { supportedLangs } from "~/content-manager"
 import { getLangFromUrl, useTranslations } from "~/i18n/utils"
 import Layout from "~/layouts/Layout.astro"
@@ -10,18 +10,17 @@ import IconRight from "~icons/tabler/arrow-big-right-lines-filled"
 import IconLogout from "~icons/tabler/logout"
 import IconUser from "~icons/tabler/user"
 
-export const prerender = true
-
-export function getStaticPaths() {
-	return supportedLangs.map((lang) => ({
-		params: { lang },
-		props: { lang },
-	}))
-}
+export const prerender = false
 
 const { lang } = Astro.props
 const t = useTranslations(lang)
 const user = Astro.locals.user
+
+function getTrackData(trackId: string, lang: string) {
+	const i18n = tracksI18n[trackId]
+	if (!i18n) return { title: "", description: "" }
+	return i18n[lang as "es" | "en"] ?? i18n.es
+}
 ---
 
 <Layout
@@ -122,8 +121,9 @@ const user = Astro.locals.user
 
     <div class="flex flex-col items-center">
       <div class="w-full max-w-2xl flex flex-col gap-4">
-        {tracks.map(track => (
-          track.disabled ? (
+        {tracks.map(track => {
+          const trackData = getTrackData(track.id, lang)
+          return track.disabled ? (
             <div class="relative flex gap-3 sm:gap-6 items-start bg-light-bg/40 border border-stroke-color/40 rounded-2xl p-4 sm:p-6 cursor-not-allowed opacity-50 select-none">
               <div class="absolute top-3 right-3 flex items-center gap-1.5">
                 <span class="text-xs bg-stroke-color/30 text-secondary/40 border border-stroke-color/30 px-2 py-0.5 rounded-full whitespace-nowrap">
@@ -139,8 +139,8 @@ const user = Astro.locals.user
               </div>
 
               <div class="flex flex-col gap-1.5 flex-1 min-w-0">
-                <span class="text-secondary/50 font-bold text-base sm:text-xl leading-tight">{track.title}</span>
-                <p class="text-secondary/40 text-xs sm:text-sm leading-relaxed">{track.description}</p>
+                <span class="text-secondary/50 font-bold text-base sm:text-xl leading-tight">{trackData.title}</span>
+                <p class="text-secondary/40 text-xs sm:text-sm leading-relaxed">{trackData.description}</p>
                 <span class="text-secondary/30 text-xs">{track.lessons} {t("learn.lessons")}</span>
               </div>
             </div>
@@ -148,10 +148,12 @@ const user = Astro.locals.user
             <div
               data-track-id={track.id}
               data-track-total={track.lessons}
-              data-track-title={track.title}
-              data-track-href={`/${lang}${track.href}`}
+              data-track-title={trackData.title}
+              data-track-href={user ? `/${lang}${track.href}` : `/${lang}/login`}
               data-track-lang={lang}
               data-track-slugs={JSON.stringify(track.slugs)}
+              data-requires-auth={!user}
+              data-original-track-href={`/${lang}${track.href}`}
               class="group relative flex gap-3 sm:gap-6 items-start bg-light-bg border border-stroke-color rounded-2xl p-4 sm:p-6 hover:border-yellow transition-all duration-200 cursor-pointer"
             >
               <span class="absolute top-3 right-3 text-xs bg-yellow/10 text-yellow border border-yellow/20 px-2 py-0.5 rounded-full whitespace-nowrap">
@@ -164,9 +166,9 @@ const user = Astro.locals.user
 
               <div class="flex flex-col gap-1.5 sm:gap-2 flex-1 min-w-0">
                 <span class="text-secondary font-bold text-base sm:text-xl group-hover:text-yellow transition-colors leading-tight pr-20">
-                  {track.title}
+                  {trackData.title}
                 </span>
-                <p class="text-secondary/60 text-xs sm:text-sm leading-relaxed">{track.description}</p>
+                <p class="text-secondary/60 text-xs sm:text-sm leading-relaxed">{trackData.description}</p>
 
                 <!-- Progress bar (hidden until JS populates it) -->
                 <div data-progress-container class="hidden flex-col gap-1 mt-0.5">
@@ -188,7 +190,7 @@ const user = Astro.locals.user
               </span>
             </div>
           )
-        ))}
+        })}
       </div>
     </div>
 
@@ -198,15 +200,12 @@ const user = Astro.locals.user
 
 <script>
   import { db } from "~/lib/stores/editor-store"
-  import { getTrackProgress } from "~/lib/progress"
   import { useTranslations, getLangFromUrl } from "~/i18n/utils"
 
   document.addEventListener("astro:page-load", async () => {
-    // Get translations for JavaScript usage
     const currentLang = getLangFromUrl(new URL(window.location.href))
     const t = useTranslations(currentLang)
 
-    // Sync server progress + last lesson positions (no-op if not logged in)
     await db.syncFromServer()
 
     const cards = document.querySelectorAll<HTMLElement>("[data-track-id]")
@@ -216,19 +215,15 @@ const user = Astro.locals.user
       const total = Number(card.dataset.trackTotal)
       const lang = card.dataset.trackLang ?? "es"
       const slugs: string[] = JSON.parse(card.dataset.trackSlugs ?? "[]")
+      const requiresAuth = card.dataset.requiresAuth === "true"
 
-      // Use server-synced IndexedDB completions as source of truth
       const completions = slugs.length > 0
         ? await Promise.all(slugs.map((s) => db.isCompleted(s)))
         : []
       const completedCount = completions.filter(Boolean).length
 
-      // Fall back to visited count if no completions yet
-      const visited = getTrackProgress(trackId)
-      const displayCount = completedCount > 0 ? completedCount : visited.length
-
-      if (displayCount > 0) {
-        const pct = Math.round((displayCount / total) * 100)
+      if (completedCount > 0) {
+        const pct = Math.round((completedCount / total) * 100)
         const container = card.querySelector<HTMLElement>("[data-progress-container]")
         const label = card.querySelector<HTMLElement>("[data-progress-label]")
         const pctEl = card.querySelector<HTMLElement>("[data-progress-pct]")
@@ -236,7 +231,7 @@ const user = Astro.locals.user
         const lessonsLabel = card.querySelector<HTMLElement>("[data-lessons-label]")
 
         if (container && label && pctEl && bar) {
-          label.textContent = `${displayCount} ${t("learn.progress_of")} ${total} ${t("learn.lessons")}`
+          label.textContent = `${completedCount} ${t("learn.progress_of")} ${total} ${t("learn.lessons")}`
           pctEl.textContent = `${pct}%`
           bar.style.width = `${pct}%`
           container.classList.remove("hidden")
@@ -245,9 +240,8 @@ const user = Astro.locals.user
         }
       }
 
-      // If server has a last lesson, update navigation target and show resume label
       const lastLesson = db.lastLesson[trackId]
-      if (lastLesson) {
+      if (lastLesson && !requiresAuth) {
         card.dataset.trackHref = `/${lang}/${lastLesson.slug}`
         const resumeLabel = card.querySelector<HTMLElement>("[data-resume-label]")
         if (resumeLabel) {
@@ -256,9 +250,17 @@ const user = Astro.locals.user
         }
       }
 
-      // Card click → navigate
-      card.addEventListener("click", () => {
-        window.location.href = card.dataset.trackHref!
+      card.addEventListener("click", (e) => {
+        e.preventDefault()
+        const requiresAuth = card.dataset.requiresAuth === "true"
+        const trackHref = card.dataset.trackHref
+        const originalTrackHref = card.dataset.originalTrackHref
+        
+        if (requiresAuth || !trackHref) {
+          window.location.href = `/${lang}/login?returnUrl=${encodeURIComponent(originalTrackHref!)}`
+        } else {
+          window.location.href = trackHref
+        }
       })
     }
   })
diff --git a/src/pages/[lang]/certificado/[trackId].astro b/src/pages/[lang]/certificado/[trackId].astro
index 75c3bec..f7a397d 100644
--- a/src/pages/[lang]/certificado/[trackId].astro
+++ b/src/pages/[lang]/certificado/[trackId].astro
@@ -1,7 +1,7 @@
 ---
 import logoSvgUrl from "~/assets/Rust_Lang_ES_Logo_Blanco_color.svg?url"
 import { tracks } from "~/const/tracks"
-import { getLangFromUrl, useTranslations } from "~/i18n/utils"
+import { useTranslations } from "~/i18n/utils"
 import Layout from "~/layouts/Layout.astro"
 import IconLeft from "~icons/tabler/arrow-big-left-lines-filled"
 
@@ -17,7 +17,7 @@ export function getStaticPaths() {
 }
 
 const { track } = Astro.props
-const lang = getLangFromUrl(Astro.url)
+const lang = Astro.params.lang as "es" | "en"
 const t = useTranslations(lang)
 ---
 
@@ -52,7 +52,7 @@ const t = useTranslations(lang)
             {t("certificate.success_message_1")}
           </p>
           <p class="text-secondary/70 text-xs leading-relaxed">
-            {t("certificate.success_message_2", { trackTitle: track.title })}
+            {t("certificate.success_message_2").replace("{trackTitle}", track.title)}
           </p>
           <p class="text-yellow/60 text-xs font-medium mt-1">
             {t("certificate.intro_text")}
diff --git a/src/pages/[lang]/login.astro b/src/pages/[lang]/login.astro
index 1ebc481..30ebc0a 100644
--- a/src/pages/[lang]/login.astro
+++ b/src/pages/[lang]/login.astro
@@ -1,5 +1,5 @@
 ---
-import { getLangFromUrl, useTranslations } from "~/i18n/utils"
+import { useTranslations } from "~/i18n/utils"
 import Layout from "~/layouts/Layout.astro"
 import JamGithub from "~icons/jam/github"
 
@@ -8,13 +8,14 @@ export function getStaticPaths() {
 }
 
 if (Astro.locals.user) {
-	return Astro.redirect(`/${getLangFromUrl(Astro.url)}/aprender`)
+	return Astro.redirect(`/${Astro.params.lang}/aprender`)
 }
 
-const lang = getLangFromUrl(Astro.url)
+const lang = Astro.params.lang as "es" | "en"
 const t = useTranslations(lang)
 
 const error = Astro.url.searchParams.get("error")
+const returnUrl = Astro.url.searchParams.get("returnUrl") ?? `/${lang}/aprender`
 const errorMessages: Record<string, string> = {
 	oauth_invalid: t("login.error_oauth_invalid"),
 	oauth_token: t("login.error_oauth_token"),
@@ -176,7 +177,7 @@ const errorMessages: Record<string, string> = {
   loginButtonLoading: t("login.login_button_loading"),
   registerButtonText: t("login.register_button"),
   registerButtonLoading: t("login.register_button_loading"),
-  redirectPath: `/${lang}/aprender`
+  returnUrl: returnUrl
 }}>
   // Tabs
   const tabs = document.querySelectorAll<HTMLButtonElement>(".tab-btn")
@@ -200,12 +201,13 @@ const errorMessages: Record<string, string> = {
     })
   })
 
-  // Login
   document.getElementById("form-login")?.addEventListener("submit", async (e) => {
     e.preventDefault()
-    const form = e.target as HTMLFormElement
-    const errorEl = document.getElementById("login-error")!
-    const btn = form.querySelector("button[type=submit]") as HTMLButtonElement
+    const form = e.target
+    const errorEl = document.getElementById("login-error")
+    const btn = form.querySelector("button[type=submit]")
+    if (!form || !errorEl || !btn) return
+    
     btn.disabled = true
     btn.textContent = loginButtonLoading
 
@@ -217,9 +219,9 @@ const errorMessages: Record<string, string> = {
     })
 
     if (res.ok) {
-      window.location.href = redirectPath
+      window.location.href = returnUrl
     } else {
-      const { error } = await res.json() as { error: string }
+      const { error } = await res.json()
       errorEl.textContent = error
       errorEl.classList.remove("hidden")
       btn.disabled = false
@@ -227,12 +229,13 @@ const errorMessages: Record<string, string> = {
     }
   })
 
-  // Register
   document.getElementById("form-register")?.addEventListener("submit", async (e) => {
     e.preventDefault()
-    const form = e.target as HTMLFormElement
-    const errorEl = document.getElementById("register-error")!
-    const btn = form.querySelector("button[type=submit]") as HTMLButtonElement
+    const form = e.target
+    const errorEl = document.getElementById("register-error")
+    const btn = form.querySelector("button[type=submit]")
+    if (!form || !errorEl || !btn) return
+    
     btn.disabled = true
     btn.textContent = registerButtonLoading
 
@@ -244,9 +247,9 @@ const errorMessages: Record<string, string> = {
     })
 
     if (res.ok) {
-      window.location.href = redirectPath
+      window.location.href = returnUrl
     } else {
-      const { error } = await res.json() as { error: string }
+      const { error } = await res.json()
       errorEl.textContent = error
       errorEl.classList.remove("hidden")
       btn.disabled = false
diff --git a/src/pages/[lang]/perfil.astro b/src/pages/[lang]/perfil.astro
index 7b7befa..b43931b 100644
--- a/src/pages/[lang]/perfil.astro
+++ b/src/pages/[lang]/perfil.astro
@@ -243,7 +243,7 @@ const trackMap = Object.fromEntries(tracks.map((t) => [t.id, t]))
   </main>
 </Layout>
 
-<script define:vars={{ 
+<script define:vars={{
   userData: {
     id: user.id,
     email: user.email,
@@ -260,28 +260,27 @@ const trackMap = Object.fromEntries(tracks.map((t) => [t.id, t]))
   }
 }}>
   import { initAuthStore, authActions } from "~/lib/stores/auth-store"
-  
+
   document.addEventListener("astro:page-load", () => {
-    // Initialize auth store with current user data
     initAuthStore(userData, nameLocked)
+
+    const editBtn = document.getElementById("edit-profile")
+    const saveBtn = document.getElementById("save-profile")
+    const input = document.getElementById("full-name")
+    const errorEl = document.getElementById("profile-error")
+    const successEl = document.getElementById("profile-success")
+    if (!editBtn || !saveBtn || !input || !errorEl || !successEl) return
     
-    const editBtn = document.getElementById("edit-profile") as HTMLButtonElement
-    const saveBtn = document.getElementById("save-profile") as HTMLButtonElement
-    const input = document.getElementById("full-name") as HTMLInputElement
-    const errorEl = document.getElementById("profile-error")!
-    const successEl = document.getElementById("profile-success")!
-    const editIcon = editBtn?.querySelector(".edit-icon")
-    const cancelIcon = editBtn?.querySelector(".cancel-icon")
-    const editLabel = editBtn?.querySelector(".edit-label")
+    const editIcon = editBtn.querySelector(".edit-icon")
+    const cancelIcon = editBtn.querySelector(".cancel-icon")
+    const editLabel = editBtn.querySelector(".edit-label")
 
     let isEditing = false
 
-    // Toggle edit mode
-    editBtn?.addEventListener("click", () => {
+    editBtn.addEventListener("click", () => {
       isEditing = !isEditing
-      
+
       if (isEditing) {
-        // Enter edit mode
         input.disabled = false
         input.focus()
         saveBtn.classList.remove("hidden")
@@ -291,9 +290,8 @@ const trackMap = Object.fromEntries(tracks.map((t) => [t.id, t]))
         errorEl.classList.add("hidden")
         successEl.classList.add("hidden")
       } else {
-        // Exit edit mode (cancel)
         input.disabled = true
-        input.value = input.defaultValue // Reset to original value
+        input.value = input.defaultValue  // Reset to original value
         saveBtn.classList.add("hidden")
         editIcon?.classList.remove("hidden")
         cancelIcon?.classList.add("hidden")
@@ -303,8 +301,7 @@ const trackMap = Object.fromEntries(tracks.map((t) => [t.id, t]))
       }
     })
 
-    // Save profile
-    saveBtn?.addEventListener("click", async () => {
+    saveBtn.addEventListener("click", async () => {
       saveBtn.disabled = true
       saveBtn.textContent = translations.saveButtonLoading
       errorEl.classList.add("hidden")
@@ -320,34 +317,33 @@ const trackMap = Object.fromEntries(tracks.map((t) => [t.id, t]))
       saveBtn.textContent = translations.saveButton
 
       if (res.ok) {
-        // Success: exit edit mode and update default value
         input.defaultValue = input.value
         isEditing = false
         input.disabled = true
         saveBtn.classList.add("hidden")
-        editIcon?.classList.remove("hidden")
-        cancelIcon?.classList.add("hidden")
+        if (editIcon) editIcon.classList.remove("hidden")
+        if (cancelIcon) cancelIcon.classList.add("hidden")
         if (editLabel) editLabel.textContent = translations.editButton
-        
-        // Update auth store with new name
+
         authActions.updateFullName(input.value)
-        
+
         successEl.classList.remove("hidden")
         setTimeout(() => successEl.classList.add("hidden"), 3000)
       } else {
-        const { error } = await res.json() as { error: string }
+        const { error } = await res.json()
         errorEl.textContent = error
         errorEl.classList.remove("hidden")
       }
     })
 
-    // Copy verification link
-    document.querySelectorAll<HTMLButtonElement>("[data-copy-link]").forEach((btn) => {
+    document.querySelectorAll("[data-copy-link]").forEach((btn) => {
       btn.addEventListener("click", async () => {
-        const path = btn.dataset.copyLink!
+        const path = btn.dataset.copyLink
+        if (!path) return
         const url = `${window.location.origin}${path}`
         await navigator.clipboard.writeText(url)
-        const label = btn.querySelector(".copy-label")!
+        const label = btn.querySelector(".copy-label")
+        if (!label) return
         const original = label.textContent
         label.textContent = translations.certificateCopied
         btn.classList.add("border-yellow", "text-yellow")
diff --git a/src/pages/[lang]/verificar/[certId].astro b/src/pages/[lang]/verificar/[certId].astro
index d166668..263192f 100644
--- a/src/pages/[lang]/verificar/[certId].astro
+++ b/src/pages/[lang]/verificar/[certId].astro
@@ -8,7 +8,7 @@ import IconCertificate from "~icons/tabler/certificate"
 
 const { certId } = Astro.params
 const { DB } = Astro.locals.runtime.env
-const lang = getLangFromUrl(Astro.url)
+const lang = getLangFromUrl(Astro.url) as "es" | "en"
 const t = useTranslations(lang)
 
 interface CertRow {
@@ -35,7 +35,7 @@ const issuedDate = new Date(cert.issued_at).toLocaleDateString(lang === "es" ? "
 })
 ---
 
-<Layout title={t("verification.title", { name: cert.name_used })}>
+<Layout title={`${t("verification.title")} - ${cert.name_used}`}>
   <header class="p-2 w-full shrink-0">
     <nav class="relative z-50 flex items-center justify-between px-3 py-1 border border-stroke-color backdrop-blur-md bg-bg-nav rounded-md shadow-lg">
       <a
diff --git a/src/pages/api/auth/github.ts b/src/pages/api/auth/github.ts
index 0a8e6a0..55f471c 100644
--- a/src/pages/api/auth/github.ts
+++ b/src/pages/api/auth/github.ts
@@ -1,11 +1,15 @@
 import type { APIRoute } from "astro"
 import { generateToken } from "~/lib/auth/crypto"
 
-export const GET: APIRoute = async ({ url, locals, cookies, redirect }) => {
+export const GET: APIRoute = async ({ url, locals, cookies, redirect, request }) => {
 	const { GITHUB_CLIENT_ID } = locals.runtime.env
 	const isLocalhost = url.hostname === "localhost" || url.hostname === "127.0.0.1"
 
-	const state = generateToken()
+	const referer = request.headers.get("referer") ?? ""
+	const langMatch = referer.match(/\/(es|en)\//)
+	const lang = langMatch ? langMatch[1] : "es"
+
+	const state = `${generateToken()}:${lang}`
 	cookies.set("oauth_state", state, {
 		httpOnly: true,
 		secure: !isLocalhost,
diff --git a/src/pages/api/auth/github/callback.ts b/src/pages/api/auth/github/callback.ts
index c28e392..e4fe84b 100644
--- a/src/pages/api/auth/github/callback.ts
+++ b/src/pages/api/auth/github/callback.ts
@@ -22,10 +22,18 @@ export const GET: APIRoute = async ({ url, locals, cookies, redirect }) => {
 	const state = url.searchParams.get("state")
 	const storedState = cookies.get("oauth_state")?.value
 
+	let lang = "es"
+	if (storedState) {
+		const parts = storedState.split(":")
+		if (parts.length === 2 && ["es", "en"].includes(parts[1])) {
+			lang = parts[1]
+		}
+	}
+
 	cookies.delete("oauth_state", { path: "/" })
 
 	if (!code || !state || state !== storedState) {
-		return redirect("/login?error=oauth_invalid")
+		return redirect(`/${lang}/login?error=oauth_invalid`)
 	}
 
 	// Intercambiar code por access_token
@@ -43,11 +51,11 @@ export const GET: APIRoute = async ({ url, locals, cookies, redirect }) => {
 	try {
 		tokenData = await tokenRes.json()
 	} catch {
-		return redirect("/login?error=oauth_token")
+		return redirect(`/${lang}/login?error=oauth_token`)
 	}
 
 	if (!tokenData.access_token) {
-		return redirect("/login?error=oauth_token")
+		return redirect(`/${lang}/login?error=oauth_token`)
 	}
 
 	const accessToken = tokenData.access_token
@@ -72,12 +80,12 @@ export const GET: APIRoute = async ({ url, locals, cookies, redirect }) => {
 		ghUser = JSON.parse(userText)
 		ghEmails = JSON.parse(emailsText)
 	} catch {
-		return redirect("/login?error=oauth_token")
+		return redirect(`/${lang}/login?error=oauth_token`)
 	}
 
 	const primaryEmail = ghEmails.find((e) => e.primary && e.verified)?.email ?? ghUser.email
 	if (!primaryEmail) {
-		return redirect("/login?error=no_email")
+		return redirect(`/${lang}/login?error=no_email`)
 	}
 
 	const providerId = String(ghUser.id)
@@ -106,8 +114,8 @@ export const GET: APIRoute = async ({ url, locals, cookies, redirect }) => {
 
 		const token = await createSession(DB, user.id)
 		cookies.set(SESSION_COOKIE, token, sessionCookieOptions())
-		return redirect("/es/aprender")
+		return redirect(`/${lang}/aprender`)
 	} catch {
-		return redirect("/login?error=oauth_token")
+		return redirect(`/${lang}/login?error=oauth_token`)
 	}
 }