Fix: Use Next.js API proxy to avoid mixed-content/CORS errors

HTTPS pages cannot fetch from HTTP backend ports. Added Next.js
API route proxies for /api/vocabulary, /api/learning-units, /api/progress
that forward to backend-lehrer internally (same Docker network, HTTP).

All frontend pages now use same-origin requests (getApiBase = '')
instead of direct port:8001 connections.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

studio-v2/app/api/learning-units/[...path]/route.ts

@@ -0,0 +1,36 @@
+import { NextRequest, NextResponse } from 'next/server'
+
+const BACKEND_URL = process.env.BACKEND_URL || 'http://backend-lehrer:8001'
+
+async function proxyRequest(
+  request: NextRequest,
+  { params }: { params: Promise<{ path: string[] }> }
+): Promise<NextResponse> {
+  const { path } = await params
+  const pathStr = path.join('/')
+  const searchParams = request.nextUrl.searchParams.toString()
+  const url = `${BACKEND_URL}/api/learning-units/${pathStr}${searchParams ? `?${searchParams}` : ''}`
+
+  try {
+    const fetchOptions: RequestInit = {
+      method: request.method,
+      headers: { 'Content-Type': 'application/json' },
+    }
+    if (request.method !== 'GET' && request.method !== 'HEAD') {
+      fetchOptions.body = await request.text()
+    }
+    const resp = await fetch(url, fetchOptions)
+    const data = await resp.text()
+    return new NextResponse(data, {
+      status: resp.status,
+      headers: { 'Content-Type': resp.headers.get('Content-Type') || 'application/json' },
+    })
+  } catch (e) {
+    return NextResponse.json({ error: String(e) }, { status: 502 })
+  }
+}
+
+export const GET = proxyRequest
+export const POST = proxyRequest
+export const PUT = proxyRequest
+export const DELETE = proxyRequest

studio-v2/app/api/learning-units/route.ts

@@ -0,0 +1,29 @@
+import { NextRequest, NextResponse } from 'next/server'
+
+const BACKEND_URL = process.env.BACKEND_URL || 'http://backend-lehrer:8001'
+
+async function proxyRequest(request: NextRequest): Promise<NextResponse> {
+  const searchParams = request.nextUrl.searchParams.toString()
+  const url = `${BACKEND_URL}/api/learning-units/${searchParams ? `?${searchParams}` : ''}`
+
+  try {
+    const fetchOptions: RequestInit = {
+      method: request.method,
+      headers: { 'Content-Type': 'application/json' },
+    }
+    if (request.method !== 'GET' && request.method !== 'HEAD') {
+      fetchOptions.body = await request.text()
+    }
+    const resp = await fetch(url, fetchOptions)
+    const data = await resp.text()
+    return new NextResponse(data, {
+      status: resp.status,
+      headers: { 'Content-Type': resp.headers.get('Content-Type') || 'application/json' },
+    })
+  } catch (e) {
+    return NextResponse.json({ error: String(e) }, { status: 502 })
+  }
+}
+
+export const GET = proxyRequest
+export const POST = proxyRequest

studio-v2/app/api/progress/[...path]/route.ts

@@ -0,0 +1,34 @@
+import { NextRequest, NextResponse } from 'next/server'
+
+const BACKEND_URL = process.env.BACKEND_URL || 'http://backend-lehrer:8001'
+
+async function proxyRequest(
+  request: NextRequest,
+  { params }: { params: Promise<{ path: string[] }> }
+): Promise<NextResponse> {
+  const { path } = await params
+  const pathStr = path.join('/')
+  const searchParams = request.nextUrl.searchParams.toString()
+  const url = `${BACKEND_URL}/api/progress/${pathStr}${searchParams ? `?${searchParams}` : ''}`
+
+  try {
+    const fetchOptions: RequestInit = {
+      method: request.method,
+      headers: { 'Content-Type': 'application/json' },
+    }
+    if (request.method !== 'GET' && request.method !== 'HEAD') {
+      fetchOptions.body = await request.text()
+    }
+    const resp = await fetch(url, fetchOptions)
+    const data = await resp.text()
+    return new NextResponse(data, {
+      status: resp.status,
+      headers: { 'Content-Type': resp.headers.get('Content-Type') || 'application/json' },
+    })
+  } catch (e) {
+    return NextResponse.json({ error: String(e) }, { status: 502 })
+  }
+}
+
+export const GET = proxyRequest
+export const POST = proxyRequest

studio-v2/app/api/vocabulary/[...path]/route.ts

@@ -0,0 +1,36 @@
+import { NextRequest, NextResponse } from 'next/server'
+
+const BACKEND_URL = process.env.BACKEND_URL || 'http://backend-lehrer:8001'
+
+async function proxyRequest(
+  request: NextRequest,
+  { params }: { params: Promise<{ path: string[] }> }
+): Promise<NextResponse> {
+  const { path } = await params
+  const pathStr = path.join('/')
+  const searchParams = request.nextUrl.searchParams.toString()
+  const url = `${BACKEND_URL}/api/vocabulary/${pathStr}${searchParams ? `?${searchParams}` : ''}`
+
+  try {
+    const fetchOptions: RequestInit = {
+      method: request.method,
+      headers: { 'Content-Type': 'application/json' },
+    }
+    if (request.method !== 'GET' && request.method !== 'HEAD') {
+      fetchOptions.body = await request.text()
+    }
+    const resp = await fetch(url, fetchOptions)
+    const data = await resp.text()
+    return new NextResponse(data, {
+      status: resp.status,
+      headers: { 'Content-Type': resp.headers.get('Content-Type') || 'application/json' },
+    })
+  } catch (e) {
+    return NextResponse.json({ error: String(e) }, { status: 502 })
+  }
+}
+
+export const GET = proxyRequest
+export const POST = proxyRequest
+export const PUT = proxyRequest
+export const DELETE = proxyRequest

studio-v2/app/api/vocabulary/route.ts

@@ -0,0 +1,29 @@
+import { NextRequest, NextResponse } from 'next/server'
+
+const BACKEND_URL = process.env.BACKEND_URL || 'http://backend-lehrer:8001'
+
+async function proxyRequest(request: NextRequest): Promise<NextResponse> {
+  const searchParams = request.nextUrl.searchParams.toString()
+  const url = `${BACKEND_URL}/api/vocabulary/${searchParams ? `?${searchParams}` : ''}`
+
+  try {
+    const fetchOptions: RequestInit = {
+      method: request.method,
+      headers: { 'Content-Type': 'application/json' },
+    }
+    if (request.method !== 'GET' && request.method !== 'HEAD') {
+      fetchOptions.body = await request.text()
+    }
+    const resp = await fetch(url, fetchOptions)
+    const data = await resp.text()
+    return new NextResponse(data, {
+      status: resp.status,
+      headers: { 'Content-Type': resp.headers.get('Content-Type') || 'application/json' },
+    })
+  } catch (e) {
+    return NextResponse.json({ error: String(e) }, { status: 502 })
+  }
+}
+
+export const GET = proxyRequest
+export const POST = proxyRequest

studio-v2/app/learn/[unitId]/flashcards/page.tsx

@@ -15,11 +15,11 @@ interface QAItem {
   incorrect_count: number
 }
 
-function getBackendUrl() {
-  if (typeof window === 'undefined') return 'http://localhost:8001'
-  const { hostname, protocol } = window.location
-  if (hostname === 'localhost') return 'http://localhost:8001'
-  return `${protocol}//${hostname}:8001`
+function getApiBase() {
+  return ''  // Same-origin proxy
+  
+  
+  
 }
 
 export default function FlashcardsPage() {
@@ -45,7 +45,7 @@ export default function FlashcardsPage() {
   const loadQA = async () => {
     setIsLoading(true)
     try {
-      const resp = await fetch(`${getBackendUrl()}/api/learning-units/${unitId}/qa`)
+      const resp = await fetch(`${getApiBase()}/api/learning-units/${unitId}/qa`)
       if (!resp.ok) throw new Error(`HTTP ${resp.status}`)
       const data = await resp.json()
       setItems(data.qa_items || [])
@@ -63,7 +63,7 @@ export default function FlashcardsPage() {
     // Update Leitner progress
     try {
       await fetch(
-        `${getBackendUrl()}/api/learning-units/${unitId}/leitner/update?item_id=${item.id}&correct=${correct}`,
+        `${getApiBase()}/api/learning-units/${unitId}/leitner/update?item_id=${item.id}&correct=${correct}`,
         { method: 'POST' }
       )
     } catch (err) {

studio-v2/app/learn/[unitId]/quiz/page.tsx

@@ -13,11 +13,11 @@ interface MCQuestion {
   explanation?: string
 }
 
-function getBackendUrl() {
-  if (typeof window === 'undefined') return 'http://localhost:8001'
-  const { hostname, protocol } = window.location
-  if (hostname === 'localhost') return 'http://localhost:8001'
-  return `${protocol}//${hostname}:8001`
+function getApiBase() {
+  return ''  // Same-origin proxy
+  
+  
+  
 }
 
 export default function QuizPage() {
@@ -43,7 +43,7 @@ export default function QuizPage() {
   const loadMC = async () => {
     setIsLoading(true)
     try {
-      const resp = await fetch(`${getBackendUrl()}/api/learning-units/${unitId}/mc`)
+      const resp = await fetch(`${getApiBase()}/api/learning-units/${unitId}/mc`)
       if (!resp.ok) throw new Error(`HTTP ${resp.status}`)
       const data = await resp.json()
       setQuestions(data.questions || [])

studio-v2/app/learn/[unitId]/story/page.tsx

@@ -5,16 +5,16 @@ import { useParams, useRouter } from 'next/navigation'
 import { useTheme } from '@/lib/ThemeContext'
 import { AudioButton } from '@/components/learn/AudioButton'
 
-function getBackendUrl() {
-  if (typeof window === 'undefined') return 'http://localhost:8001'
-  const { hostname, protocol } = window.location
-  if (hostname === 'localhost') return 'http://localhost:8001'
-  return `${protocol}//${hostname}:8001`
+function getApiBase() {
+  return ''  // Same-origin proxy
+  
+  
+  
 }
 
 function getKlausurApiUrl() {
   if (typeof window === 'undefined') return 'http://localhost:8086'
-  const { hostname, protocol } = window.location
+  
   if (hostname === 'localhost') return 'http://localhost:8086'
   return `${protocol}//${hostname}/klausur-api`
 }
@@ -39,7 +39,7 @@ export default function StoryPage() {
 
     try {
       // First get the QA data to extract vocabulary
-      const qaResp = await fetch(`${getBackendUrl()}/api/learning-units/${unitId}/qa`)
+      const qaResp = await fetch(`${getApiBase()}/api/learning-units/${unitId}/qa`)
       let vocabulary: { english: string; german: string }[] = []
 
       if (qaResp.ok) {
@@ -58,7 +58,7 @@ export default function StoryPage() {
       }
 
       // Generate story
-      const resp = await fetch(`${getBackendUrl()}/api/learning-units/${unitId}/generate-story`, {
+      const resp = await fetch(`${getApiBase()}/api/learning-units/${unitId}/generate-story`, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify({ vocabulary, language, grade_level: '5-8' }),

studio-v2/app/learn/[unitId]/type/page.tsx

@@ -13,11 +13,11 @@ interface QAItem {
   leitner_box: number
 }
 
-function getBackendUrl() {
-  if (typeof window === 'undefined') return 'http://localhost:8001'
-  const { hostname, protocol } = window.location
-  if (hostname === 'localhost') return 'http://localhost:8001'
-  return `${protocol}//${hostname}:8001`
+function getApiBase() {
+  return ''  // Same-origin proxy
+  
+  
+  
 }
 
 export default function TypePage() {
@@ -44,7 +44,7 @@ export default function TypePage() {
   const loadQA = async () => {
     setIsLoading(true)
     try {
-      const resp = await fetch(`${getBackendUrl()}/api/learning-units/${unitId}/qa`)
+      const resp = await fetch(`${getApiBase()}/api/learning-units/${unitId}/qa`)
       if (!resp.ok) throw new Error(`HTTP ${resp.status}`)
       const data = await resp.json()
       setItems(data.qa_items || [])
@@ -61,7 +61,7 @@ export default function TypePage() {
 
     try {
       await fetch(
-        `${getBackendUrl()}/api/learning-units/${unitId}/leitner/update?item_id=${item.id}&correct=${correct}`,
+        `${getApiBase()}/api/learning-units/${unitId}/leitner/update?item_id=${item.id}&correct=${correct}`,
         { method: 'POST' }
       )
     } catch (err) {

studio-v2/app/learn/page.tsx

@@ -17,11 +17,8 @@ interface LearningUnit {
   created_at: string
 }
 
-function getBackendUrl() {
-  if (typeof window === 'undefined') return 'http://localhost:8001'
-  const { hostname, protocol } = window.location
-  if (hostname === 'localhost') return 'http://localhost:8001'
-  return `${protocol}//${hostname}:8001`
+function getApiBase() {
+  return ''  // Same-origin proxy via /api/learning-units/...
 }
 
 export default function LearnPage() {
@@ -41,7 +38,7 @@ export default function LearnPage() {
   const loadUnits = async () => {
     setIsLoading(true)
     try {
-      const resp = await fetch(`${getBackendUrl()}/api/learning-units/`)
+      const resp = await fetch(`${getApiBase()}/api/learning-units/`)
       if (!resp.ok) throw new Error(`HTTP ${resp.status}`)
       const data = await resp.json()
       setUnits(data)
@@ -54,7 +51,7 @@ export default function LearnPage() {
 
   const handleDelete = async (unitId: string) => {
     try {
-      const resp = await fetch(`${getBackendUrl()}/api/learning-units/${unitId}`, { method: 'DELETE' })
+      const resp = await fetch(`${getApiBase()}/api/learning-units/${unitId}`, { method: 'DELETE' })
       if (resp.ok) {
         setUnits((prev) => prev.filter((u) => u.id !== unitId))
       }

studio-v2/app/vocabulary/page.tsx

@@ -22,11 +22,9 @@ interface VocabWord {
   tags: string[]
 }
 
-function getBackendUrl() {
-  if (typeof window === 'undefined') return 'http://localhost:8001'
-  const { hostname, protocol } = window.location
-  if (hostname === 'localhost') return 'http://localhost:8001'
-  return `${protocol}//${hostname}:8001`
+/** Use Next.js API proxy to avoid mixed-content/CORS issues */
+function getApiBase() {
+  return ''  // Same-origin: /api/vocabulary/... proxied by Next.js
 }
 
 export default function VocabularyPage() {
@@ -55,7 +53,7 @@ export default function VocabularyPage() {
 
   // Load filters on mount
   useEffect(() => {
-    fetch(`${getBackendUrl()}/api/vocabulary/filters`)
+    fetch(`${getApiBase()}/api/vocabulary/filters`)
       .then(r => r.ok ? r.json() : null)
       .then(d => { if (d) setFilters(d) })
       .catch(() => {})
@@ -73,12 +71,12 @@ export default function VocabularyPage() {
       try {
         let url: string
         if (query.trim()) {
-          url = `${getBackendUrl()}/api/vocabulary/search?q=${encodeURIComponent(query)}&limit=30`
+          url = `${getApiBase()}/api/vocabulary/search?q=${encodeURIComponent(query)}&limit=30`
         } else {
           const params = new URLSearchParams({ limit: '30' })
           if (posFilter) params.set('pos', posFilter)
           if (diffFilter) params.set('difficulty', String(diffFilter))
-          url = `${getBackendUrl()}/api/vocabulary/browse?${params}`
+          url = `${getApiBase()}/api/vocabulary/browse?${params}`
         }
         const resp = await fetch(url)
         if (resp.ok) {
@@ -107,7 +105,7 @@ export default function VocabularyPage() {
     if (!unitTitle.trim() || selectedWords.length === 0) return
     setIsCreating(true)
     try {
-      const resp = await fetch(`${getBackendUrl()}/api/vocabulary/units`, {
+      const resp = await fetch(`${getApiBase()}/api/vocabulary/units`, {
         method: 'POST',
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify({

studio-v2/components/dashboard/LearningProgress.tsx

@@ -31,11 +31,11 @@ interface LearningProgressProps {
   glassCard: string
 }
 
-function getBackendUrl() {
-  if (typeof window === 'undefined') return 'http://localhost:8001'
-  const { hostname, protocol } = window.location
-  if (hostname === 'localhost') return 'http://localhost:8001'
-  return `${protocol}//${hostname}:8001`
+function getApiBase() {
+  return ''  // Same-origin proxy
+  
+  
+  
 }
 
 export function LearningProgress({ isDark, glassCard }: LearningProgressProps) {
@@ -51,8 +51,8 @@ export function LearningProgress({ isDark, glassCard }: LearningProgressProps) {
     setIsLoading(true)
     try {
       const [unitsResp, progressResp] = await Promise.all([
-        fetch(`${getBackendUrl()}/api/learning-units/`),
-        fetch(`${getBackendUrl()}/api/progress/`),
+        fetch(`${getApiBase()}/api/learning-units/`),
+        fetch(`${getApiBase()}/api/progress/`),
       ])
 
       if (unitsResp.ok) setUnits(await unitsResp.json())