Diff a proposed script against the open one and take it a hunk at a time

Plugin/unraid/pages/scheduler.php

@@ -2445,6 +2445,9 @@ if (document.getElementById('vv-sched-ai-chat')) {
     // Per-block Insert buttons render only where a page can receive them.
     onInsertCode: vvAiInsertCode,
     onOpenSource: vvAiOpenSource,
+    // Diff and per-hunk apply against whatever the editor holds at the moment of the click.
+    getCompareText: vvAiCompareText,
+    onReplaceCode:  vvAiReplaceCode,
   });
 }
 
@@ -2530,6 +2533,36 @@ function vvAiEditorOpen() {
   return !!ed && ed.style.display !== 'none';
 }
 
+// What a proposed block is diffed against: the editor exactly as it stands right now, not as it
+// was when the answer arrived. Read fresh on every draw, so applying one hunk and redrawing shows
+// the remaining differences rather than a stale picture.
+function vvAiCompareText() {
+  const ta = document.getElementById('vv-editor-body');
+  return (ta && vvAiEditorOpen()) ? ta.value : '';
+}
+
+// Takes the whole rewritten file back from a hunk apply. Whole-file rather than a splice because
+// the component computed the result against this exact text — handing back a range would make
+// both sides responsible for the arithmetic, and only one of them can be right.
+function vvAiReplaceCode(text) {
+  const ta = document.getElementById('vv-editor-body');
+  if (!ta || !vvAiEditorOpen()) {
+    if (vvSchedChat) vvSchedChat.note('The editor is not open — nothing was applied.');
+    return;
+  }
+
+  // Bracketed immediately, so one Ctrl+Z steps back over the whole hunk rather than unpicking it
+  // a keystroke at a time. Cursor position is kept where it was where that still makes sense.
+  vvUndoCapture(true);
+  const caret = Math.min(ta.selectionStart, text.length);
+  ta.value = text;
+  ta.selectionStart = ta.selectionEnd = caret;
+  vvUndoCapture(true);
+
+  vvSyncHlOverlay();
+  vvEditorCursorMoved();
+}
+
 // Called by the chat component's per-block Insert button, with that block's exact text. This
 // replaced a whole-answer offer: the offer had to guess which block was meant when an answer
 // carried several, and it asked after every code answer whether or not anything was wanted.