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/extendChain.ts

@@ -1,4 +1,4 @@
-import { copyFileSync, existsSync, readFileSync } from 'node:fs'
+import { copyFileSync, existsSync, readFileSync, writeFileSync } from 'node:fs'
 import { join } from 'node:path'
 import { composeShotPrompt } from '~/utils/globalLocks'
 import { composePromptParts } from '~/utils/promptParts'
@@ -16,12 +16,22 @@ import {
   nextFamilyPartName,
   removeExtendTemp
 } from '~/server/utils/library'
-import { extractLastFrame, probeHasAudio } from '~/server/utils/ffmpeg'
+import { probeHasAudio } from '~/server/utils/ffmpeg'
 import { ensureComfyReady } from '~/server/utils/comfyLifecycle'
 import { waitForComfySocket, watchComfyJob } from '~/server/utils/watch'
 import { comfyFilenamePrefix, queuePrompt, uploadImage } from '~/server/utils/comfy'
 import { buildWorkflow } from '~/server/utils/workflow'
 import { writePendingJob } from '~/server/utils/pending'
+import {
+  refineExtensionHandoffFrame,
+  resolveExtensionHandoffFrame
+} from '~/server/utils/extensionFrame'
+import {
+  clampRefinementDenoise,
+  parseRefineExtensionFrame,
+  parseSaveLosslessAnchor,
+  REFINEMENT_DENOISE_DEFAULT
+} from '~/utils/extensionFrame'
 
 const SAMPLERS = new Set(['res_multistep', 'euler', 'dpmpp_2m'])
 const SCHEDULERS = new Set(['simple', 'ddim_uniform', 'sgm_uniform'])
@@ -63,6 +73,9 @@ export async function beginExtendFromClip(params: {
   loraStack?: unknown
   folderLocked?: boolean
   name?: string
+  refineExtensionFrame?: boolean
+  saveLosslessAnchor?: boolean
+  refinementDenoise?: number
 }) {
   const source = getClip(params.ownerKey, params.clipId)
   const sourcePath = clipVideoPath(params.ownerKey, source.id)
@@ -111,6 +124,9 @@ export async function beginExtendFromClip(params: {
   const width = source.width || 1344
   const height = source.height || 768
   const clipName = String(params.name || '').trim() || nextFamilyPartName(params.ownerKey, source)
+  const refineExtensionFrame = parseRefineExtensionFrame(params.refineExtensionFrame, true)
+  const saveLosslessAnchor = parseSaveLosslessAnchor(params.saveLosslessAnchor, false)
+  const refinementDenoise = clampRefinementDenoise(params.refinementDenoise, REFINEMENT_DENOISE_DEFAULT)
 
   const job = createJob()
   job.kind = 'video'
@@ -149,6 +165,9 @@ export async function beginExtendFromClip(params: {
     workflow,
     globalLocks: source.globalLocks,
     permanenceRefs: source.permanenceRefs,
+    refineExtensionFrame,
+    saveLosslessAnchor,
+    refinementDenoise,
     ...loraFields
   }
 
@@ -169,6 +188,9 @@ export async function beginExtendFromClip(params: {
     fps,
     samplerName,
     scheduler,
+    refineExtensionFrame,
+    saveLosslessAnchor,
+    refinementDenoise,
     ...loraFields
   }).catch((error) => {
     removeExtendTemp(job.library?.extendTmpDir)
@@ -198,13 +220,21 @@ async function runExtend(
     fps: number
     samplerName: string
     scheduler: string
+    refineExtensionFrame?: boolean
+    saveLosslessAnchor?: boolean
+    refinementDenoise?: number
     loraName?: string
     loraStack?: import('~/utils/loras').LoraStackItem[]
   }
 ) {
   copyFileSync(params.sourcePath, params.part1Path)
-  await extractLastFrame(params.sourcePath, params.framePath)
-  const frame = readFileSync(params.framePath)
+  const handoff = await resolveExtensionHandoffFrame({
+    ownerKey: job.library!.ownerKey,
+    sourceClipId: job.library?.extendSourceClipId,
+    sourceVideoPath: params.sourcePath,
+    destPath: params.framePath
+  })
+  let frame = readFileSync(handoff.path)
   if (!frame.length || frame.length < 64) {
     throw new Error('Could not extract the last frame of the clip being extended')
   }
@@ -223,8 +253,36 @@ async function runExtend(
   })
 
   const done = watchComfyJob(job)
+  if (params.refineExtensionFrame !== false) {
+    emitJob(job, {
+      type: 'status',
+      message: handoff.source === 'anchor'
+        ? 'Refining lossless anchor frame...'
+        : 'Refining extracted handoff frame...',
+      progress: 3
+    })
+    try {
+      frame = await refineExtensionHandoffFrame({
+        frame,
+        denoise: params.refinementDenoise,
+        seed: params.seed,
+        clientId: job.clientId,
+        jobId: job.id,
+        onStatus: (message) => emitJob(job, { type: 'status', message, progress: 4 })
+      })
+      writeFileSync(params.framePath, frame)
+    } catch (error) {
+      const detail = error instanceof Error ? error.message : String(error)
+      emitJob(job, {
+        type: 'status',
+        message: `Frame refine skipped (${detail}). Using source frame.`,
+        progress: 4
+      })
+    }
+  }
+
   job.status = 'uploading'
-  emitJob(job, { type: 'status', message: 'Uploading last frame to ComfyUI...', progress: 4 })
+  emitJob(job, { type: 'status', message: 'Uploading last frame to ComfyUI...', progress: 5 })
   const uploaded = await uploadImage({ filename: 'last_frame.png', data: frame, type: 'image/png' }, job.id)
   if (job.library) {
     job.library.imageName = uploaded.name
@@ -251,7 +309,8 @@ async function runExtend(
     sound,
     workflow: job.library?.workflow,
     duration: job.library?.duration,
-    loraStack: params.loraStack || job.library?.loraStack || params.loraName || job.library?.loraName
+    loraStack: params.loraStack || job.library?.loraStack || params.loraName || job.library?.loraName,
+    saveLosslessAnchor: params.saveLosslessAnchor === true || job.library?.saveLosslessAnchor === true
   })
 
   const queued = await queuePrompt(graph, job.clientId)