diff --git a/apps/rowboat/app/api/uploaded-images/describe/route.ts b/apps/rowboat/app/api/uploaded-images/describe/route.ts
new file mode 100644
index 00000000..06b37765
--- /dev/null
+++ b/apps/rowboat/app/api/uploaded-images/describe/route.ts
@@ -0,0 +1,77 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { S3Client, GetObjectCommand, HeadObjectCommand } from '@aws-sdk/client-s3';
+import { GoogleGenerativeAI } from '@google/generative-ai';
+
+export async function POST(request: NextRequest) {
+  try {
+    const { id } = await request.json();
+    if (!id || typeof id !== 'string') {
+      return NextResponse.json({ error: 'id is required' }, { status: 400 });
+    }
+
+    const bucket = process.env.RAG_UPLOADS_S3_BUCKET || '';
+    if (!bucket) {
+      return NextResponse.json({ error: 'S3 bucket not configured' }, { status: 500 });
+    }
+
+    const region = process.env.RAG_UPLOADS_S3_REGION || 'us-east-1';
+    const s3 = new S3Client({
+      region,
+      credentials: process.env.AWS_ACCESS_KEY_ID && process.env.AWS_SECRET_ACCESS_KEY ? {
+        accessKeyId: process.env.AWS_ACCESS_KEY_ID as string,
+        secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY as string,
+      } : undefined,
+    });
+
+    const last2 = id.slice(-2).padStart(2, '0');
+    const dirA = last2.charAt(0);
+    const dirB = last2.charAt(1);
+    const baseKey = `uploaded_images/${dirA}/${dirB}/${id}`;
+    const exts = ['.png', '.jpg', '.webp', '.bin'];
+    let foundExt: string | null = null;
+    for (const ext of exts) {
+      try {
+        await s3.send(new HeadObjectCommand({ Bucket: bucket, Key: `${baseKey}${ext}` }));
+        foundExt = ext; break;
+      } catch {}
+    }
+    if (!foundExt) {
+      return NextResponse.json({ error: 'Not found' }, { status: 404 });
+    }
+
+    const key = `${baseKey}${foundExt}`;
+    const resp = await s3.send(new GetObjectCommand({ Bucket: bucket, Key: key }));
+    const contentType = resp.ContentType || 'application/octet-stream';
+    const body = resp.Body as any;
+    const chunks: Uint8Array[] = [];
+    await new Promise<void>((resolve, reject) => {
+      body.on('data', (c: Uint8Array) => chunks.push(c));
+      body.on('end', () => resolve());
+      body.on('error', reject);
+    });
+    const buf = Buffer.concat(chunks);
+
+    let descriptionMarkdown: string | null = null;
+    try {
+      const apiKey = process.env.GOOGLE_API_KEY || process.env.GEMINI_API_KEY || '';
+      if (apiKey) {
+        const genAI = new GoogleGenerativeAI(apiKey);
+        const model = genAI.getGenerativeModel({ model: 'gemini-2.5-flash' });
+        const prompt = 'Describe this image in concise, high-quality Markdown. Focus on key objects, text, layout, style, colors, and any notable details. Do not include extra commentary or instructions.';
+        const result = await model.generateContent([
+          { inlineData: { data: buf.toString('base64'), mimeType: contentType } },
+          prompt,
+        ]);
+        descriptionMarkdown = result.response?.text?.() || null;
+      }
+    } catch (e) {
+      console.warn('Gemini description failed', e);
+    }
+
+    return NextResponse.json({ id, description: descriptionMarkdown });
+  } catch (e) {
+    console.error('describe error', e);
+    return NextResponse.json({ error: 'Failed to describe' }, { status: 500 });
+  }
+}
+
diff --git a/apps/rowboat/app/api/uploaded-images/upload-url/route.ts b/apps/rowboat/app/api/uploaded-images/upload-url/route.ts
new file mode 100644
index 00000000..86c2537e
--- /dev/null
+++ b/apps/rowboat/app/api/uploaded-images/upload-url/route.ts
@@ -0,0 +1,47 @@
+import { NextRequest, NextResponse } from 'next/server';
+import { S3Client, PutObjectCommand } from '@aws-sdk/client-s3';
+import { getSignedUrl } from '@aws-sdk/s3-request-presigner';
+import crypto from 'crypto';
+
+export async function POST(request: NextRequest) {
+  try {
+    const bucket = process.env.RAG_UPLOADS_S3_BUCKET || '';
+    if (!bucket) {
+      return NextResponse.json({ error: 'S3 bucket not configured' }, { status: 500 });
+    }
+
+    const { mimeType } = await request.json();
+    if (!mimeType || typeof mimeType !== 'string') {
+      return NextResponse.json({ error: 'mimeType is required' }, { status: 400 });
+    }
+
+    const ext = mimeType === 'image/jpeg' ? '.jpg'
+      : mimeType === 'image/webp' ? '.webp'
+      : mimeType === 'image/png' ? '.png'
+      : '.bin';
+
+    const id = crypto.randomUUID();
+    const last2 = id.slice(-2).padStart(2, '0');
+    const dirA = last2.charAt(0);
+    const dirB = last2.charAt(1);
+    const key = `uploaded_images/${dirA}/${dirB}/${id}${ext}`;
+
+    const region = process.env.RAG_UPLOADS_S3_REGION || 'us-east-1';
+    const s3 = new S3Client({
+      region,
+      credentials: process.env.AWS_ACCESS_KEY_ID && process.env.AWS_SECRET_ACCESS_KEY ? {
+        accessKeyId: process.env.AWS_ACCESS_KEY_ID as string,
+        secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY as string,
+      } : undefined,
+    });
+
+    const command = new PutObjectCommand({ Bucket: bucket, Key: key, ContentType: mimeType });
+    const uploadUrl = await getSignedUrl(s3, command, { expiresIn: 600 });
+
+    return NextResponse.json({ id, key, uploadUrl, url: `/api/uploaded-images/${id}`, mimeType });
+  } catch (e) {
+    console.error('upload-url error', e);
+    return NextResponse.json({ error: 'Failed to create upload URL' }, { status: 500 });
+  }
+}
+
diff --git a/apps/rowboat/components/common/compose-box-playground.tsx b/apps/rowboat/components/common/compose-box-playground.tsx
index fe9f6396..39a30320 100644
--- a/apps/rowboat/components/common/compose-box-playground.tsx
+++ b/apps/rowboat/components/common/compose-box-playground.tsx
@@ -87,22 +87,73 @@ export function ComposeBoxPlayground({
             }
             const controller = new AbortController();
             uploadAbortRef.current = controller;
-            const form = new FormData();
-            form.append('file', file);
-            const res = await fetch('/api/uploaded-images', {
-                method: 'POST',
-                body: form,
-                signal: controller.signal,
-            });
-            if (!res.ok) {
-                throw new Error(`Upload failed: ${res.status}`);
-            }
-            const data = await res.json();
-            const url: string | undefined = data?.url;
-            if (!url) throw new Error('No URL returned');
-            // Only apply state if request wasn't aborted/dismissed
-            if (uploadAbortRef.current === controller) {
-                setPendingImage({ url, previewSrc, mimeType: data?.mimeType, description: data?.description ?? null });
+            let usedFallback = false;
+            try {
+                // 1) Request a presigned S3 upload URL
+                const urlRes = await fetch('/api/uploaded-images/upload-url', {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({ mimeType: file.type }),
+                    signal: controller.signal,
+                });
+                if (!urlRes.ok) throw new Error(`Failed to get upload URL: ${urlRes.status}`);
+                const urlData = await urlRes.json();
+                const uploadUrl: string | undefined = urlData?.uploadUrl;
+                const imageId: string | undefined = urlData?.id;
+                const imageUrl: string | undefined = urlData?.url;
+                if (!uploadUrl || !imageId || !imageUrl) throw new Error('Invalid upload URL response');
+
+                // 2) Upload the file directly to S3
+                const putRes = await fetch(uploadUrl, {
+                    method: 'PUT',
+                    headers: { 'Content-Type': file.type },
+                    body: file,
+                    signal: controller.signal,
+                });
+                if (!putRes.ok) throw new Error(`Failed to upload image: ${putRes.status}`);
+
+                // 3) Update local state with URL (description pending)
+                if (uploadAbortRef.current === controller) {
+                    setPendingImage({ url: imageUrl, previewSrc, mimeType: file.type, description: undefined });
+                }
+
+                // 4) Ask server to generate description from S3 image
+                const descRes = await fetch('/api/uploaded-images/describe', {
+                    method: 'POST',
+                    headers: { 'Content-Type': 'application/json' },
+                    body: JSON.stringify({ id: imageId }),
+                    signal: controller.signal,
+                });
+                if (descRes.ok) {
+                    const descData = await descRes.json();
+                    const description: string | null = descData?.description ?? null;
+                    if (uploadAbortRef.current === controller) {
+                        setPendingImage({ url: imageUrl, previewSrc, mimeType: file.type, description });
+                    }
+                } else {
+                    // If description fails, still allow sending
+                    if (uploadAbortRef.current === controller) {
+                        setPendingImage({ url: imageUrl, previewSrc, mimeType: file.type, description: null });
+                    }
+                }
+            } catch (err) {
+                // On local, S3 may be unconfigured. Fallback to legacy temp upload endpoint.
+                if (err?.name === 'AbortError') throw err;
+                usedFallback = true;
+                const form = new FormData();
+                form.append('file', file);
+                const res = await fetch('/api/uploaded-images', {
+                    method: 'POST',
+                    body: form,
+                    signal: controller.signal,
+                });
+                if (!res.ok) throw new Error(`Upload failed: ${res.status}`);
+                const data = await res.json();
+                const url: string | undefined = data?.url;
+                if (!url) throw new Error('No URL returned');
+                if (uploadAbortRef.current === controller) {
+                    setPendingImage({ url, previewSrc, mimeType: data?.mimeType || file.type, description: data?.description ?? null });
+                }
             }
         } catch (e: any) {
             if (e?.name === 'AbortError') {