Split prompts into pre/prompt/post and tidy the AIGen video form.

Keep wrappers off the library mid-prompt so Use as input and Extend restore the same split, send stills to xAIGen as hidden inputs, and stop the two-column library from growing with the list.

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

server/api/extend.post.ts

@@ -1,6 +1,7 @@
 import { copyFileSync, existsSync, readFileSync } from 'node:fs'
 import { join } from 'node:path'
 import { composeShotPrompt } from '~/utils/globalLocks'
+import { composePromptParts } from '~/utils/promptParts'
 import { parsePostedLoraStack, listStudioLoras, persistLoraFields, ensureComfyLoraNames } from '~/server/utils/loras'
 import { readLoraStack } from '~/utils/loras'
 import { clampVideoCfg } from '~/utils/generationPresets'
@@ -39,7 +40,7 @@ function parseScheduler(raw: unknown) {
 }
 
 export default defineEventHandler(async (event) => {
-  const body = await readBody<{ clipId?: string; prompt?: 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 }>(event).catch(() => ({}))
   const clipId = String(body?.clipId || '').trim()
   const prompt = String(body?.prompt || '').trim()
   if (!clipId) {
@@ -60,9 +61,11 @@ export default defineEventHandler(async (event) => {
   const destFolder = publicLibrary(event).folders.find(folder => folder.id === source.folderId)
   const folderLocked = Boolean(destFolder?.protected && !destFolder.unlocked)
   const durationSeconds = parseExtendDuration(body?.duration)
+  const promptPre = String(body?.promptPre ?? source.promptPre ?? '').trim()
+  const promptPost = String(body?.promptPost ?? source.promptPost ?? '').trim()
   const composedPrompt = composeShotPrompt({
     globalLocks: source.globalLocks,
-    prompt,
+    prompt: composePromptParts(promptPre, prompt, promptPost),
     shotIndex: (source.chainIndex || 0) + 1,
     familyRefs: source.permanenceRefs
   })
@@ -99,7 +102,10 @@ export default defineEventHandler(async (event) => {
     hideThumbnail: source.hideThumbnail,
     folderLocked,
     name: clipName,
-    prompt: composedPrompt,
+    prompt,
+    promptMid: prompt,
+    promptPre: promptPre || undefined,
+    promptPost: promptPost || undefined,
     aspect: source.aspect || '16:9',
     width,
     height,