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/api/extend.post.ts

@@ -6,9 +6,26 @@ import { clipPartDuration, clampVideoDuration } from '~/utils/videoDuration'
 import { defaultVideoSteps, isLtxWorkflow, LTX_DISABLED_MESSAGE, ltxWorkflowEnabled, parseVideoWorkflow } from '~/utils/videoModels'
 import { composePromptParts } from '~/utils/promptParts'
 import { nextFamilyPartName } from '~/server/utils/library'
+import {
+  clampRefinementDenoise,
+  parseRefineExtensionFrame,
+  parseSaveLosslessAnchor,
+  REFINEMENT_DENOISE_DEFAULT
+} from '~/utils/extensionFrame'
 
 export default defineEventHandler(async (event) => {
-  const body = await readBody<{ clipId?: string; prompt?: string; promptPre?: string; promptPost?: string; duration?: number; lora?: unknown; loraStack?: unknown }>(event).catch(() => ({}))
+  const body = await readBody<{
+    clipId?: string
+    prompt?: string
+    promptPre?: string
+    promptPost?: string
+    duration?: number
+    lora?: unknown
+    loraStack?: unknown
+    refineExtensionFrame?: boolean | string
+    saveLosslessAnchor?: boolean | string
+    refinementDenoise?: number | string
+  }>(event).catch(() => ({}))
   const clipId = String(body?.clipId || '').trim()
   const prompt = String(body?.prompt || '').trim()
   if (!clipId) {
@@ -87,6 +104,9 @@ export default defineEventHandler(async (event) => {
       extensions: [],
       queueAutoRun: false,
       extendFromClipId: clipId,
+      refineExtensionFrame: parseRefineExtensionFrame(body?.refineExtensionFrame, true),
+      saveLosslessAnchor: parseSaveLosslessAnchor(body?.saveLosslessAnchor, false),
+      refinementDenoise: clampRefinementDenoise(body?.refinementDenoise, REFINEMENT_DENOISE_DEFAULT),
       globalLocks: source.globalLocks,
       permanenceRefs: source.permanenceRefs,
       ...persistLoraFields(loraStack)