diff --git a/src/routes/clinicalAssistant.js b/src/routes/clinicalAssistant.js
index 36b753e..a97ae9a 100644
--- a/src/routes/clinicalAssistant.js
+++ b/src/routes/clinicalAssistant.js
@@ -1097,15 +1097,30 @@ async function generateImage(prompt, model) {
   if (!process.env.LITELLM_API_BASE) throw new Error('LiteLLM is required for image generation');
   var headers = { 'Content-Type': 'application/json' };
   if (process.env.LITELLM_API_KEY) headers.Authorization = 'Bearer ' + process.env.LITELLM_API_KEY;
+  var size = imageSizeForPrompt(prompt);
   var resp = await axios.post(gatewayUrl('/images/generations'), {
     model: model,
-    prompt: prompt,
-    size: '1024x1024'
+    prompt: imagePromptForCanvas(prompt, size),
+    size: size
   }, { headers: headers, timeout: 120000 });
   var item = resp.data && resp.data.data && resp.data.data[0] ? resp.data.data[0] : {};
   return { imageUrl: item.url || null, base64: item.b64_json || null, raw: (!item.url && !item.b64_json) ? resp.data : undefined };
 }
 
+function imageSizeForPrompt(prompt) {
+  var text = String(prompt || '');
+  if (/\b(flow\s*chart|flowchart|algorithm|pathway|timeline|vertical|stepwise|decision\s*tree|age\s*group|0-21|22-28|29-60)\b/i.test(text)) return '1024x1792';
+  if (/\b(table|matrix|comparison|wide|landscape|side-by-side)\b/i.test(text)) return '1792x1024';
+  return '1024x1024';
+}
+
+function imagePromptForCanvas(prompt, size) {
+  var guidance = ' Keep all text and boxes fully inside the canvas with generous margins. Use fewer words per box, large readable type, and avoid cropping at edges.';
+  if (size === '1024x1792') guidance += ' Use a vertical portrait layout with top-to-bottom flow and ample spacing between decision nodes.';
+  if (size === '1792x1024') guidance += ' Use a wide landscape layout with columns and ample horizontal spacing.';
+  return String(prompt || '').trim() + guidance;
+}
+
 async function getSetting(key, fallback) {
   try {
     var val = await db.getSetting(key);