Add extension-frame refine and lossless anchor options.

Prefer clip anchor PNGs for handoffs, optionally run Bilateral+Flux cleanup before I2V, and save decoded last-frame anchors so sequential extensions accumulate less compression damage.

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

server/utils/workflow.ts

@@ -40,6 +40,7 @@ export interface GenerateParams {
   referenceImageNames?: string[]
   loraName?: string
   loraStack?: LoraStackItem[]
+  saveLosslessAnchor?: boolean
 }
 
 type WorkflowNode = { class_type: string; inputs: Record<string, unknown>; _meta?: { title?: string } }
@@ -228,9 +229,34 @@ export function buildWorkflow(params: GenerateParams) {
 
   resolveGraphLoraNames(graph, 'video')
   applyUserLoraToGraph(graph, params.loraStack || params.loraName)
+  attachLosslessAnchorSave(graph, params, version === 'v2' ? '164' : '105:90')
   return graph
 }
 
+function attachLosslessAnchorSave(graph: WorkflowGraph, params: GenerateParams, decodeNodeId: string) {
+  if (!params.saveLosslessAnchor) return
+  if (!graph[decodeNodeId]) return
+  const batchIndex = Math.max(0, Math.floor(Number(params.length) || 1) - 1)
+  const prefix = String(params.filenamePrefix || 'video/MiniMax_H3').replace(/\/+$/, '')
+  graph.aigen_anchor_pick = {
+    class_type: 'ImageFromBatch',
+    inputs: {
+      image: [decodeNodeId, 0],
+      batch_index: batchIndex,
+      length: 1
+    },
+    _meta: { title: 'Last Decoded Frame' }
+  }
+  graph.aigen_anchor_save = {
+    class_type: 'SaveImage',
+    inputs: {
+      filename_prefix: `${prefix}_last`,
+      images: ['aigen_anchor_pick', 0]
+    },
+    _meta: { title: 'Save Lossless Anchor' }
+  }
+}
+
 function promptForNode(classType: string, useRefs: boolean, actionPrompt: string, graphPrompt: string) {
   if (classType === 'MiniMaxH3ImageToVideo') return useRefs ? '' : actionPrompt
   if (classType === 'MiniMaxH3TextToVideo') return actionPrompt
@@ -302,6 +328,8 @@ function buildLtxWorkflow(params: GenerateParams, version: VideoWorkflowId) {
   }
   resolveGraphLoraNames(graph, 'video')
   applyUserLoraToGraph(graph, params.loraStack || params.loraName)
+  // LTX VAEDecode is typically node 15
+  attachLosslessAnchorSave(graph, params, '15')
   return graph
 }