Allow Studio 2 MiniMax text-to-video with empty start when locks are off.

Co-authored-by: Cursor <cursoragent@cursor.com>

server/utils/studio2/runner.ts

@@ -89,11 +89,12 @@ async function prepareGraph(r: any) {
             const { frameLength } = await import('../videoChain');
             const { ltxWorkflowEnabled, LTX_DISABLED_MESSAGE } = await import('~/utils/videoModels');
             if (!ltxWorkflowEnabled()) throw new Error(LTX_DISABLED_MESSAGE);
-            if (!start) throw new Error('Choose a start still for LTX video.');
+            const textToVideo = q.mode === 'video' && !start;
+            if (!start && !textToVideo) throw new Error('Choose a start still for LTX video.');
             const fps = s.fps || 24;
             graph = buildWorkflow({
-                workflow: 'ltx',
-                imageName: start,
+                workflow: textToVideo ? 'ltx-t2v' : 'ltx',
+                imageName: start || '',
                 prompt: q.compiledPrompt,
                 width: s.width,
                 height: s.height,
@@ -111,7 +112,7 @@ async function prepareGraph(r: any) {
                 useIdentityRefs: false
             });
             await ensureComfyLoraNames('video');
-            r.graphId = 'workflow_ltx_video.json';
+            r.graphId = textToVideo ? 'workflow_ltx_video.json#t2v' : 'workflow_ltx_video.json';
         } else {
             if (q.engine !== 'minimax')
                 throw new Error('Studio 2 video supports MiniMax H3 and LTX (xAIGen).');