diff --git a/client/src/pages/mobile/remotion-video.tsx b/client/src/pages/mobile/remotion-video.tsx
index c450b4a..9c43165 100644
--- a/client/src/pages/mobile/remotion-video.tsx
+++ b/client/src/pages/mobile/remotion-video.tsx
@@ -147,13 +147,43 @@ export default function MobileRemotionVideoPage() {
       const response = await fetch("/api/remotion/render", { method: "POST", body: formData });
       if (!response.ok) { const e = await response.json().catch(() => ({})); throw new Error(e.error || "Erreur"); }
       const data = await response.json();
-      setVideoUrl(data.url);
-      // Pre-fill description with overlay text so it appears in the Facebook post
-      if (overlayText && !publishDescription) setPublishDescription(overlayText);
-      toast({ title: "Vidéo générée !" });
+      
+      if (data.jobId) {
+        toast({ title: "Rendu démarré", description: "Veuillez patienter (~1-2 min)..." });
+        
+        const checkStatus = async () => {
+          try {
+            const res = await fetch(`/api/remotion/render/status/${data.jobId}`);
+            if (!res.ok) throw new Error("Erreur de suivi du rendu");
+            const job = await res.json();
+            
+            if (job.status === 'done') {
+              setVideoUrl(job.url);
+              if (overlayText && !publishDescription) setPublishDescription(overlayText);
+              toast({ title: "Vidéo générée !" });
+              setIsRendering(false);
+            } else if (job.status === 'error') {
+              toast({ title: "Erreur de rendu", description: job.error || "Échec du rendu", variant: "destructive" });
+              setIsRendering(false);
+            } else {
+              setTimeout(checkStatus, 3000);
+            }
+          } catch (e: any) {
+            toast({ title: "Erreur de connexion", description: e.message, variant: "destructive" });
+            setIsRendering(false);
+          }
+        };
+        setTimeout(checkStatus, 3000);
+      } else {
+        setVideoUrl(data.url);
+        if (overlayText && !publishDescription) setPublishDescription(overlayText);
+        toast({ title: "Vidéo générée !" });
+        setIsRendering(false);
+      }
     } catch (err: any) {
       toast({ title: "Erreur", description: err.message, variant: "destructive" });
-    } finally { setIsRendering(false); }
+      setIsRendering(false);
+    }
   };
 
   const handlePublish = async () => {
diff --git a/client/src/pages/remotion-video.tsx b/client/src/pages/remotion-video.tsx
index 46504c9..4a93596 100644
--- a/client/src/pages/remotion-video.tsx
+++ b/client/src/pages/remotion-video.tsx
@@ -114,13 +114,45 @@ export default function RemotionVideoPage() {
       const response = await fetch("/api/remotion/render", { method: "POST", body: formData });
       if (!response.ok) { const e = await response.json().catch(() => ({})); throw new Error(e.error || "Erreur"); }
       const data = await response.json();
-      setVideoUrl(data.url);
-      // Pre-fill description with overlay text so it appears in the Facebook post
-      if (overlayText && !publishDescription) setPublishDescription(overlayText);
-      toast({ title: "Vidéo générée !", description: "Votre vidéo est prête à publier." });
+      
+      if (data.jobId) {
+        toast({ title: "Rendu démarré", description: "Veuillez patienter (~1-2 min)..." });
+        
+        const checkStatus = async () => {
+          try {
+            const res = await fetch(`/api/remotion/render/status/${data.jobId}`);
+            if (!res.ok) throw new Error("Erreur de suivi du rendu");
+            const job = await res.json();
+            
+            if (job.status === 'done') {
+              setVideoUrl(job.url);
+              if (overlayText && !publishDescription) setPublishDescription(overlayText);
+              toast({ title: "Vidéo générée !", description: "Votre vidéo est prête à publier." });
+              setIsRendering(false);
+            } else if (job.status === 'error') {
+              toast({ title: "Erreur de rendu", description: job.error || "Échec du rendu", variant: "destructive" });
+              setIsRendering(false);
+            } else {
+              setTimeout(checkStatus, 3000);
+            }
+          } catch (e: any) {
+            toast({ title: "Erreur de connexion", description: e.message, variant: "destructive" });
+            setIsRendering(false);
+          }
+        };
+        setTimeout(checkStatus, 3000);
+      } else {
+        // Fallback for older sync backend
+        setVideoUrl(data.url);
+        if (overlayText && !publishDescription) setPublishDescription(overlayText);
+        toast({ title: "Vidéo générée !", description: "Votre vidéo est prête à publier." });
+        setIsRendering(false);
+      }
     } catch (err: any) {
       toast({ title: "Erreur", description: err.message || "Impossible de créer la vidéo.", variant: "destructive" });
-    } finally { setIsRendering(false); }
+      setIsRendering(false);
+    }
+    // Note: removed finally block so isRendering stays true during polling
   };
 
   const handlePublish = async () => {
diff --git a/server/routes/remotion.ts b/server/routes/remotion.ts
index 4a1496f..75042fe 100644
--- a/server/routes/remotion.ts
+++ b/server/routes/remotion.ts
@@ -33,6 +33,20 @@ async function generateVideoThumbnail(videoPath: string, outputPath: string, see
 
 export const remotionRouter = Router();
 
+interface RenderJob {
+  status: 'processing' | 'done' | 'error';
+  url?: string;
+  thumbnailUrl?: string | null;
+  error?: string;
+}
+const renderJobs = new Map<string, RenderJob>();
+
+remotionRouter.get("/render/status/:jobId", (req, res) => {
+  const job = renderJobs.get(req.params.jobId);
+  if (!job) return res.status(404).json({ error: "Job introuvable" });
+  res.json(job);
+});
+
 const uploadDir = path.join(process.cwd(), "uploads", "temp");
 if (!fs.existsSync(uploadDir)) {
   fs.mkdirSync(uploadDir, { recursive: true });
@@ -294,45 +308,58 @@ remotionRouter.post("/render", upload.fields([{ name: "images", maxCount: 4 }, {
       inputProps,
     });
 
-    const outputFilename = `out-${Date.now()}.mp4`;
-    const outputLocation = path.join(uploadDir, outputFilename);
+    const jobId = Date.now().toString();
+    renderJobs.set(jobId, { status: 'processing' });
+    res.json({ jobId, message: "Rendu démarré en arrière-plan" });
 
-    console.log("🎬 Rendering media...", totalFrames, "frames");
+    // Run async to prevent 504 Gateway Timeout
+    (async () => {
+      try {
+        const outputFilename = `out-${Date.now()}.mp4`;
+        const outputLocation = path.join(uploadDir, outputFilename);
 
-    await renderMedia({
-      composition: { ...composition, durationInFrames: totalFrames },
-      serveUrl: bundleLocation,
-      codec: "h264",
-      outputLocation,
-      inputProps,
-      chromiumOptions: {
-        disableWebSecurity: true,
-        ignoreCertificateErrors: true,
-        args: ["--no-sandbox", "--disable-setuid-sandbox", "--disable-dev-shm-usage", "--disable-gpu"],
-      },
-      concurrency: 1, // Limit concurrency to prevent Docker memory exhaustion
-    });
+        console.log("🎬 Rendering media...", totalFrames, "frames (Job:", jobId, ")");
 
-    console.log("✅ Render completed:", outputFilename);
+        await renderMedia({
+          composition: { ...composition, durationInFrames: totalFrames },
+          serveUrl: bundleLocation,
+          codec: "h264",
+          outputLocation,
+          inputProps,
+          chromiumOptions: {
+            disableWebSecurity: true,
+            ignoreCertificateErrors: true,
+            args: ["--no-sandbox", "--disable-setuid-sandbox", "--disable-dev-shm-usage", "--disable-gpu"],
+          },
+          concurrency: 1, // Limit concurrency to prevent Docker memory exhaustion
+        });
 
-    // Generate thumbnail for the video
-    const thumbnailFilename = outputFilename.replace('.mp4', '-thumb.jpg');
-    const thumbnailPath = path.join(uploadDir, thumbnailFilename);
-    const thumbnailGenerated = await generateVideoThumbnail(outputLocation, thumbnailPath, 2);
+        console.log("✅ Render completed:", outputFilename);
 
-    if (thumbnailGenerated) {
-      console.log("🖼️ Thumbnail generated:", thumbnailFilename);
-    }
+        // Generate thumbnail for the video
+        const thumbnailFilename = outputFilename.replace('.mp4', '-thumb.jpg');
+        const thumbnailPath = path.join(uploadDir, thumbnailFilename);
+        const thumbnailGenerated = await generateVideoThumbnail(outputLocation, thumbnailPath, 2);
 
-    // Return relative URL so any client (mobile, desktop, Docker) can access it
-    res.json({
-      url: `/uploads/temp/${outputFilename}`,
-      thumbnailUrl: thumbnailGenerated ? `/uploads/temp/${thumbnailFilename}` : null,
-    });
+        if (thumbnailGenerated) {
+          console.log("🖼️ Thumbnail generated:", thumbnailFilename);
+        }
+
+        renderJobs.set(jobId, {
+          status: 'done',
+          url: `/uploads/temp/${outputFilename}`,
+          thumbnailUrl: thumbnailGenerated ? `/uploads/temp/${thumbnailFilename}` : null,
+        });
+
+      } catch (err: any) {
+        console.error("❌ Remotion render error for Job", jobId, ":", err);
+        renderJobs.set(jobId, { status: 'error', error: "Erreur lors du rendu: " + err.message });
+      }
+    })();
 
   } catch (err: any) {
-    console.error("❌ Remotion render error:", err);
-    res.status(500).json({ error: "Erreur lors du rendu: " + err.message });
+    console.error("❌ Remotion pre-render error:", err);
+    res.status(500).json({ error: "Erreur lors du lancement du rendu: " + err.message });
   }
 });
 
diff --git a/task.md b/task.md
index 563f27e..ef2d704 100644
--- a/task.md
+++ b/task.md
@@ -6,7 +6,7 @@ Ajout d'une fonctionnalité complète de création de Reels Facebook permettant
 
 ## Current Focus
 
-**Phase: EXECUTION** - Fix Remotion Render Target Closed error.
+**Phase: EXECUTION** - Fix 504 Gateway Timeout on Remotion Render (Async Polling).
 
 ## Master Plan
 
@@ -269,3 +269,11 @@ Ajout d'une fonctionnalité complète de création de Reels Facebook permettant
 - [x] Ajouter les arguments `--disable-dev-shm-usage`, `--no-sandbox` aux options de Chromium.
 - [x] Limiter la concurrence `concurrency: 1` dans `renderMedia` pour économiser la mémoire en Docker.
 
+### Phase 26: Fix 504 Gateway Timeout (Async Remotion Render) 🚀
+
+- [x] Backend: Modifier `POST /api/remotion/render` pour retourner un `jobId` immédiatement.
+- [x] Backend: Créer la route `GET /api/remotion/render/status/:jobId` pour suivre l'état (in-memory map).
+- [x] Frontend: Modifier `remotion-video.tsx` pour faire du polling sur le `jobId` après la soumission.
+- [x] Frontend: Appliquer la même modification de polling à `mobile/remotion-video.tsx`.
+
+