diff --git a/src/routes/myResources.js b/src/routes/myResources.js
index 9a470583..d043b631 100644
--- a/src/routes/myResources.js
+++ b/src/routes/myResources.js
@@ -456,7 +456,7 @@ router.post('/my-resources/:id/refine', async function (req, res) {
     if (!instructions) return res.status(400).json({ error: 'Say what to change' });
 
     var existing = await db.get(
-      'SELECT id, kind, topic, markdown FROM user_resources WHERE id = ? AND user_id = ?',
+      'SELECT id, kind, topic, markdown, deck FROM user_resources WHERE id = ? AND user_id = ?',
       [parseInt(req.params.id, 10), req.user.id]
     );
     if (!existing) return res.status(404).json({ error: 'Not found' });
@@ -494,15 +494,29 @@ router.post('/my-resources/:id/refine', async function (req, res) {
         'substitute for it, and no image tag or URL goes into the markdown.'
       : '';
 
-    // The markdown is the thing being edited, which is the whole reason it is
-    // what gets stored: "change slide 4" is a text edit, not a binary patch.
-    var messages = [{ role: 'user', content:
-      'Revise the following Pandoc markdown according to the instruction. ' +
-      'Return ONLY the complete revised markdown, no commentary, no code fences. ' +
-      'Keep the same overall structure unless the instruction asks otherwise, and keep any ' +
-      'References section at the end.\n\nINSTRUCTION: ' + instructions + illustration + material +
-      '\n\nMARKDOWN:\n"""\n' + existing.markdown + '\n"""' }];
-    var options = { model: await resolveModel(req.body.model), temperature: 0.2 };
+    // A presentation with a stored deck is edited as a deck. Editing its
+    // markdown instead changed only the markdown: export renders from the deck,
+    // so a modification succeeded, said so, and produced an identical download.
+    var existingDeck = existing.deck
+      ? (typeof existing.deck === 'string' ? JSON.parse(existing.deck) : existing.deck) : null;
+    if (existingDeck && !(existingDeck.slides || []).length) existingDeck = null;
+
+    var messages = [{ role: 'user', content: existingDeck
+      ? 'Revise the following slide deck according to the instruction. Return ONLY the ' +
+        'complete revised JSON object, in exactly the same shape, no commentary and no code ' +
+        'fences. Keep every slide that the instruction does not ask you to change, including ' +
+        'its layout and its "image_job" values, and keep any References slide last.\n\n' +
+        'INSTRUCTION: ' + instructions + illustration + material +
+        '\n\nThe layouts available are:\n' + deckSchema.instructions(
+          (existingDeck.slides || []).length, 0) +
+        '\n\nDECK JSON:\n' + JSON.stringify({ slides: existingDeck.slides })
+      : 'Revise the following Pandoc markdown according to the instruction. ' +
+        'Return ONLY the complete revised markdown, no commentary, no code fences. ' +
+        'Keep the same overall structure unless the instruction asks otherwise, and keep any ' +
+        'References section at the end.\n\nINSTRUCTION: ' + instructions + illustration + material +
+        '\n\nMARKDOWN:\n"""\n' + existing.markdown + '\n"""' }];
+    // The reply restates the whole resource, so it needs room for one.
+    var options = { model: await resolveModel(req.body.model), temperature: 0.2, maxTokens: 16000 };
     var tools = sources.wantsImages ? resourceImages.tools : [];
     var callOptions = tools.length ? Object.assign({}, options, { tools: tools }) : options;
     if (tools.length && resourceImages.requestedCount(instructions)) callOptions.toolChoice = 'required';
@@ -515,7 +529,22 @@ router.post('/my-resources/:id/refine', async function (req, res) {
       });
     }
 
-    var revised = String((ai && ai.content) || '').trim();
+    var revisedDeck = existingDeck ? deckBuild.parse(ai && ai.content) : null;
+    if (existingDeck && !revisedDeck) {
+      // A reply that is not a deck would otherwise be saved as the markdown and
+      // silently drop every layout the deck held.
+      console.warn('[my-resources] refine did not return a usable deck; nothing changed');
+      return res.status(502).json({ error: 'That change could not be applied. Try wording it differently.' });
+    }
+    if (revisedDeck) {
+      // Carried through rather than trusted from the reply.
+      revisedDeck.title = existingDeck.title;
+      revisedDeck.subtitle = existingDeck.subtitle;
+      revisedDeck.date = existingDeck.date;
+    }
+
+    var revised = revisedDeck ? deckSchema.toMarkdown(revisedDeck)
+      : String((ai && ai.content) || '').trim();
     if (!revised) return res.status(502).json({ error: 'The model returned nothing. Try again.' });
 
     // Figures from a modification are added to the ones already there, not
@@ -523,9 +552,10 @@ router.post('/my-resources/:id/refine', async function (req, res) {
     var added = (ai.imageJobs || []).map(function (job) { return job.jobId; }).filter(Boolean);
     var row = await db.get(
       'UPDATE user_resources SET markdown = ?, title = ?, updated_at = NOW(), ' +
-      'image_ids = image_ids || ?::jsonb ' +
+      'image_ids = image_ids || ?::jsonb, deck = COALESCE(?::jsonb, deck) ' +
       'WHERE id = ? AND user_id = ? RETURNING id, title, updated_at',
-      [revised, firstHeading(revised), JSON.stringify(added), existing.id, req.user.id]
+      [revised, firstHeading(revised), JSON.stringify(added),
+       revisedDeck ? JSON.stringify(revisedDeck) : null, existing.id, req.user.id]
     );
     res.json({
       success: true, resource: row, markdown: revised,
diff --git a/test/my-resources.test.js b/test/my-resources.test.js
index 4ba60f26..ef837457 100644
--- a/test/my-resources.test.js
+++ b/test/my-resources.test.js
@@ -279,6 +279,27 @@ test('the library is bounded, searchable, and drives the modify picker', () => {
   assert.match(js, /library\.length\s*\n?\s*\? 'Nothing matches/);
 });
 
+test('modifying a presentation edits the deck, not only its markdown', () => {
+  const route = read('src/routes/myResources.js');
+  // Export renders from the stored deck. Refine edited the markdown beside it
+  // and left the deck alone, so a modification reported success, updated the
+  // library row, and produced a byte-identical download. Measured: markdown
+  // gained the new slide, the deck did not, and the exported pptx did not.
+  assert.match(route, /SELECT id, kind, topic, markdown, deck FROM user_resources/);
+  assert.match(route, /var revisedDeck = existingDeck \? deckBuild\.parse\(ai && ai\.content\) : null;/);
+  assert.match(route, /deck = COALESCE\(\?::jsonb, deck\)/, 'and the deck is written back');
+
+  // A reply that is not a deck must not be saved as markdown: that would drop
+  // every layout the deck held while looking like it worked.
+  assert.match(route, /refine did not return a usable deck; nothing changed/);
+  assert.match(route, /That change could not be applied\. Try wording it differently\./);
+
+  // An article has no deck and keeps the markdown path.
+  assert.match(route, /: 'Revise the following Pandoc markdown according to the instruction\. '/);
+  // The reply restates the whole resource, so it needs room for one.
+  assert.match(route, /temperature: 0\.2, maxTokens: 16000/);
+});
+
 test('modify revises something already generated, in place', () => {
   const js = read('public/js/myResources.js');
   // The endpoint existed with no way to reach it: the markdown is what is