diff --git a/app/api/chat/route.ts b/app/api/chat/route.ts
index 801f465..c37817d 100644
--- a/app/api/chat/route.ts
+++ b/app/api/chat/route.ts
@@ -20,6 +20,7 @@ import type { StatelessChatRequest, StatelessEvent } from '@/lib/types/chat';
 import type { ThinkingConfig } from '@/lib/types/provider';
 import { apiError } from '@/lib/server/api-response';
 import { createLogger } from '@/lib/logger';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 const log = createLogger('Chat API');
 
 // Allow streaming responses up to 60 seconds
@@ -63,8 +64,21 @@ export async function POST(req: NextRequest) {
     // Resolve API key: client > server > empty
     const modelString = body.model || 'gpt-4o-mini';
     const { providerId, modelId } = parseModelString(modelString);
-    const effectiveApiKey = resolveApiKey(providerId, body.apiKey);
-    const effectiveBaseUrl = resolveBaseUrl(providerId, body.baseUrl);
+
+    const clientBaseUrl = body.baseUrl || undefined;
+    if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+      const ssrfError = validateUrlForSSRF(clientBaseUrl);
+      if (ssrfError) {
+        return apiError('INVALID_URL', 403, ssrfError);
+      }
+    }
+
+    const effectiveApiKey = clientBaseUrl
+      ? body.apiKey || ''
+      : resolveApiKey(providerId, body.apiKey);
+    const effectiveBaseUrl = clientBaseUrl
+      ? clientBaseUrl
+      : resolveBaseUrl(providerId, body.baseUrl);
     const proxy = resolveProxy(providerId);
 
     if (!effectiveApiKey) {
diff --git a/app/api/generate/image/route.ts b/app/api/generate/image/route.ts
index 1c95618..a3b8c3a 100644
--- a/app/api/generate/image/route.ts
+++ b/app/api/generate/image/route.ts
@@ -21,6 +21,7 @@ import { resolveImageApiKey, resolveImageBaseUrl } from '@/lib/server/provider-c
 import type { ImageProviderId, ImageGenerationOptions } from '@/lib/media/types';
 import { createLogger } from '@/lib/logger';
 import { apiError, apiSuccess } from '@/lib/server/api-response';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 
 const log = createLogger('ImageGeneration API');
 
@@ -39,7 +40,16 @@ export async function POST(request: NextRequest) {
     const clientBaseUrl = request.headers.get('x-base-url') || undefined;
     const clientModel = request.headers.get('x-image-model') || undefined;
 
-    const apiKey = resolveImageApiKey(providerId, clientApiKey);
+    if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+      const ssrfError = validateUrlForSSRF(clientBaseUrl);
+      if (ssrfError) {
+        return apiError('INVALID_URL', 403, ssrfError);
+      }
+    }
+
+    const apiKey = clientBaseUrl
+      ? clientApiKey || ''
+      : resolveImageApiKey(providerId, clientApiKey);
     if (!apiKey) {
       return apiError(
         'MISSING_API_KEY',
@@ -48,7 +58,7 @@ export async function POST(request: NextRequest) {
       );
     }
 
-    const baseUrl = resolveImageBaseUrl(providerId, clientBaseUrl);
+    const baseUrl = clientBaseUrl ? clientBaseUrl : resolveImageBaseUrl(providerId, clientBaseUrl);
 
     // Resolve dimensions from aspect ratio if not explicitly set
     if (!body.width && !body.height && body.aspectRatio) {
diff --git a/app/api/generate/tts/route.ts b/app/api/generate/tts/route.ts
index 4ae820c..542f105 100644
--- a/app/api/generate/tts/route.ts
+++ b/app/api/generate/tts/route.ts
@@ -13,6 +13,7 @@ import { resolveTTSApiKey, resolveTTSBaseUrl } from '@/lib/server/provider-confi
 import type { TTSProviderId } from '@/lib/audio/types';
 import { createLogger } from '@/lib/logger';
 import { apiError, apiSuccess } from '@/lib/server/api-response';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 
 const log = createLogger('TTS API');
 
@@ -45,9 +46,20 @@ export async function POST(req: NextRequest) {
       return apiError('INVALID_REQUEST', 400, 'browser-native-tts must be handled client-side');
     }
 
-    // Resolve API key and base URL (server-side fallback)
-    const apiKey = resolveTTSApiKey(ttsProviderId, ttsApiKey || undefined);
-    const baseUrl = resolveTTSBaseUrl(ttsProviderId, ttsBaseUrl || undefined);
+    const clientBaseUrl = ttsBaseUrl || undefined;
+    if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+      const ssrfError = validateUrlForSSRF(clientBaseUrl);
+      if (ssrfError) {
+        return apiError('INVALID_URL', 403, ssrfError);
+      }
+    }
+
+    const apiKey = clientBaseUrl
+      ? ttsApiKey || ''
+      : resolveTTSApiKey(ttsProviderId, ttsApiKey || undefined);
+    const baseUrl = clientBaseUrl
+      ? clientBaseUrl
+      : resolveTTSBaseUrl(ttsProviderId, ttsBaseUrl || undefined);
 
     // Build TTS config
     const config = {
diff --git a/app/api/generate/video/route.ts b/app/api/generate/video/route.ts
index c852666..7ec3399 100644
--- a/app/api/generate/video/route.ts
+++ b/app/api/generate/video/route.ts
@@ -22,6 +22,7 @@ import { resolveVideoApiKey, resolveVideoBaseUrl } from '@/lib/server/provider-c
 import type { VideoProviderId, VideoGenerationOptions } from '@/lib/media/types';
 import { createLogger } from '@/lib/logger';
 import { apiError, apiSuccess } from '@/lib/server/api-response';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 
 const log = createLogger('VideoGeneration API');
 
@@ -40,7 +41,16 @@ export async function POST(request: NextRequest) {
     const clientBaseUrl = request.headers.get('x-base-url') || undefined;
     const clientModel = request.headers.get('x-video-model') || undefined;
 
-    const apiKey = resolveVideoApiKey(providerId, clientApiKey);
+    if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+      const ssrfError = validateUrlForSSRF(clientBaseUrl);
+      if (ssrfError) {
+        return apiError('INVALID_URL', 403, ssrfError);
+      }
+    }
+
+    const apiKey = clientBaseUrl
+      ? clientApiKey || ''
+      : resolveVideoApiKey(providerId, clientApiKey);
     if (!apiKey) {
       return apiError(
         'MISSING_API_KEY',
@@ -49,7 +59,7 @@ export async function POST(request: NextRequest) {
       );
     }
 
-    const baseUrl = resolveVideoBaseUrl(providerId, clientBaseUrl);
+    const baseUrl = clientBaseUrl ? clientBaseUrl : resolveVideoBaseUrl(providerId, clientBaseUrl);
 
     // Normalize options against provider capabilities
     const options = normalizeVideoOptions(providerId, body);
diff --git a/app/api/parse-pdf/route.ts b/app/api/parse-pdf/route.ts
index 2a6e5ab..94feff5 100644
--- a/app/api/parse-pdf/route.ts
+++ b/app/api/parse-pdf/route.ts
@@ -5,6 +5,7 @@ import type { PDFProviderId } from '@/lib/pdf/types';
 import type { ParsedPdfContent } from '@/lib/types/pdf';
 import { createLogger } from '@/lib/logger';
 import { apiError, apiSuccess } from '@/lib/server/api-response';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 const log = createLogger('Parse PDF');
 
 export async function POST(req: NextRequest) {
@@ -32,10 +33,22 @@ export async function POST(req: NextRequest) {
     // providerId is required from the client — no server-side store to fall back to
     const effectiveProviderId = providerId || ('unpdf' as PDFProviderId);
 
+    const clientBaseUrl = baseUrl || undefined;
+    if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+      const ssrfError = validateUrlForSSRF(clientBaseUrl);
+      if (ssrfError) {
+        return apiError('INVALID_URL', 403, ssrfError);
+      }
+    }
+
     const config = {
       providerId: effectiveProviderId,
-      apiKey: resolvePDFApiKey(effectiveProviderId, apiKey || undefined),
-      baseUrl: resolvePDFBaseUrl(effectiveProviderId, baseUrl || undefined),
+      apiKey: clientBaseUrl
+        ? apiKey || ''
+        : resolvePDFApiKey(effectiveProviderId, apiKey || undefined),
+      baseUrl: clientBaseUrl
+        ? clientBaseUrl
+        : resolvePDFBaseUrl(effectiveProviderId, baseUrl || undefined),
     };
 
     // Convert PDF to buffer
diff --git a/app/api/transcription/route.ts b/app/api/transcription/route.ts
index d496ff1..c3bf5a2 100644
--- a/app/api/transcription/route.ts
+++ b/app/api/transcription/route.ts
@@ -4,6 +4,7 @@ import { resolveASRApiKey, resolveASRBaseUrl } from '@/lib/server/provider-confi
 import type { ASRProviderId } from '@/lib/audio/types';
 import { createLogger } from '@/lib/logger';
 import { apiError, apiSuccess } from '@/lib/server/api-response';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 const log = createLogger('Transcription');
 
 export const maxDuration = 60;
@@ -24,11 +25,23 @@ export async function POST(req: NextRequest) {
     // providerId is required from the client — no server-side store to fall back to
     const effectiveProviderId = providerId || ('openai-whisper' as ASRProviderId);
 
+    const clientBaseUrl = baseUrl || undefined;
+    if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+      const ssrfError = validateUrlForSSRF(clientBaseUrl);
+      if (ssrfError) {
+        return apiError('INVALID_URL', 403, ssrfError);
+      }
+    }
+
     const config = {
       providerId: effectiveProviderId,
       language: language || 'auto',
-      apiKey: resolveASRApiKey(effectiveProviderId, apiKey || undefined),
-      baseUrl: resolveASRBaseUrl(effectiveProviderId, baseUrl || undefined),
+      apiKey: clientBaseUrl
+        ? apiKey || ''
+        : resolveASRApiKey(effectiveProviderId, apiKey || undefined),
+      baseUrl: clientBaseUrl
+        ? clientBaseUrl
+        : resolveASRBaseUrl(effectiveProviderId, baseUrl || undefined),
     };
 
     // Convert audio file to buffer
diff --git a/app/api/verify-image-provider/route.ts b/app/api/verify-image-provider/route.ts
index 75dc8fd..9ec0446 100644
--- a/app/api/verify-image-provider/route.ts
+++ b/app/api/verify-image-provider/route.ts
@@ -20,6 +20,7 @@ import { resolveImageApiKey, resolveImageBaseUrl } from '@/lib/server/provider-c
 import type { ImageProviderId } from '@/lib/media/types';
 import { apiError, apiSuccess } from '@/lib/server/api-response';
 import { createLogger } from '@/lib/logger';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 
 const log = createLogger('VerifyImageProvider');
 
@@ -30,8 +31,17 @@ export async function POST(request: NextRequest) {
     const clientApiKey = request.headers.get('x-api-key') || undefined;
     const clientBaseUrl = request.headers.get('x-base-url') || undefined;
 
-    const apiKey = resolveImageApiKey(providerId, clientApiKey);
-    const baseUrl = resolveImageBaseUrl(providerId, clientBaseUrl);
+    if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+      const ssrfError = validateUrlForSSRF(clientBaseUrl);
+      if (ssrfError) {
+        return apiError('INVALID_URL', 403, ssrfError);
+      }
+    }
+
+    const apiKey = clientBaseUrl
+      ? clientApiKey || ''
+      : resolveImageApiKey(providerId, clientApiKey);
+    const baseUrl = clientBaseUrl ? clientBaseUrl : resolveImageBaseUrl(providerId, clientBaseUrl);
 
     if (!apiKey) {
       return apiError('MISSING_API_KEY', 400, 'No API key configured');
diff --git a/app/api/verify-pdf-provider/route.ts b/app/api/verify-pdf-provider/route.ts
index 97b3e0b..3b0ac3f 100644
--- a/app/api/verify-pdf-provider/route.ts
+++ b/app/api/verify-pdf-provider/route.ts
@@ -2,6 +2,7 @@ import { NextRequest } from 'next/server';
 import { createLogger } from '@/lib/logger';
 import { apiError, apiSuccess } from '@/lib/server/api-response';
 import { resolvePDFApiKey, resolvePDFBaseUrl } from '@/lib/server/provider-config';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 
 const log = createLogger('Verify PDF Provider');
 
@@ -13,12 +14,22 @@ export async function POST(req: NextRequest) {
       return apiError('MISSING_REQUIRED_FIELD', 400, 'Provider ID is required');
     }
 
-    const resolvedBaseUrl = resolvePDFBaseUrl(providerId, baseUrl);
+    const clientBaseUrl = (baseUrl as string | undefined) || undefined;
+    if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+      const ssrfError = validateUrlForSSRF(clientBaseUrl);
+      if (ssrfError) {
+        return apiError('INVALID_URL', 403, ssrfError);
+      }
+    }
+
+    const resolvedBaseUrl = clientBaseUrl ? clientBaseUrl : resolvePDFBaseUrl(providerId, baseUrl);
     if (!resolvedBaseUrl) {
       return apiError('MISSING_REQUIRED_FIELD', 400, 'Base URL is required');
     }
 
-    const resolvedApiKey = resolvePDFApiKey(providerId, apiKey);
+    const resolvedApiKey = clientBaseUrl
+      ? (apiKey as string | undefined) || ''
+      : resolvePDFApiKey(providerId, apiKey);
 
     const headers: Record<string, string> = {};
     if (resolvedApiKey) {
@@ -28,8 +39,13 @@ export async function POST(req: NextRequest) {
     const response = await fetch(resolvedBaseUrl, {
       headers,
       signal: AbortSignal.timeout(10000),
+      redirect: 'manual',
     });
 
+    if (response.status >= 300 && response.status < 400) {
+      return apiError('REDIRECT_NOT_ALLOWED', 403, 'Redirects are not allowed');
+    }
+
     // MinerU's FastAPI root returns 404 (no root route), but the server is reachable.
     // Any HTTP response (including 404) means the server is up.
     return apiSuccess({
diff --git a/app/api/verify-video-provider/route.ts b/app/api/verify-video-provider/route.ts
index d11f971..69d4d33 100644
--- a/app/api/verify-video-provider/route.ts
+++ b/app/api/verify-video-provider/route.ts
@@ -20,6 +20,7 @@ import { resolveVideoApiKey, resolveVideoBaseUrl } from '@/lib/server/provider-c
 import type { VideoProviderId } from '@/lib/media/types';
 import { apiError, apiSuccess } from '@/lib/server/api-response';
 import { createLogger } from '@/lib/logger';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 
 const log = createLogger('VerifyVideoProvider');
 
@@ -30,8 +31,17 @@ export async function POST(request: NextRequest) {
     const clientApiKey = request.headers.get('x-api-key') || undefined;
     const clientBaseUrl = request.headers.get('x-base-url') || undefined;
 
-    const apiKey = resolveVideoApiKey(providerId, clientApiKey);
-    const baseUrl = resolveVideoBaseUrl(providerId, clientBaseUrl);
+    if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+      const ssrfError = validateUrlForSSRF(clientBaseUrl);
+      if (ssrfError) {
+        return apiError('INVALID_URL', 403, ssrfError);
+      }
+    }
+
+    const apiKey = clientBaseUrl
+      ? clientApiKey || ''
+      : resolveVideoApiKey(providerId, clientApiKey);
+    const baseUrl = clientBaseUrl ? clientBaseUrl : resolveVideoBaseUrl(providerId, clientBaseUrl);
 
     if (!apiKey) {
       return apiError('MISSING_API_KEY', 400, 'No API key configured');
diff --git a/lib/server/resolve-model.ts b/lib/server/resolve-model.ts
index 02c5084..71b9500 100644
--- a/lib/server/resolve-model.ts
+++ b/lib/server/resolve-model.ts
@@ -8,6 +8,7 @@
 import type { NextRequest } from 'next/server';
 import { getModel, parseModelString, type ModelWithInfo } from '@/lib/ai/providers';
 import { resolveApiKey, resolveBaseUrl, resolveProxy } from '@/lib/server/provider-config';
+import { validateUrlForSSRF } from '@/lib/server/ssrf-guard';
 
 export interface ResolvedModel extends ModelWithInfo {
   /** Original model string (e.g. "openai/gpt-4o-mini") */
@@ -28,8 +29,19 @@ export function resolveModel(params: {
 }): ResolvedModel {
   const modelString = params.modelString || process.env.DEFAULT_MODEL || 'gpt-4o-mini';
   const { providerId, modelId } = parseModelString(modelString);
-  const apiKey = resolveApiKey(providerId, params.apiKey || '');
-  const baseUrl = resolveBaseUrl(providerId, params.baseUrl);
+
+  const clientBaseUrl = params.baseUrl || undefined;
+  if (clientBaseUrl && process.env.NODE_ENV === 'production') {
+    const ssrfError = validateUrlForSSRF(clientBaseUrl);
+    if (ssrfError) {
+      throw new Error(ssrfError);
+    }
+  }
+
+  const apiKey = clientBaseUrl
+    ? params.apiKey || ''
+    : resolveApiKey(providerId, params.apiKey || '');
+  const baseUrl = clientBaseUrl ? clientBaseUrl : resolveBaseUrl(providerId, params.baseUrl);
   const proxy = resolveProxy(providerId);
   const { model, modelInfo } = getModel({
     providerId,