[eric] paste-dialog: uncontrolled editor (large pastes typed like molasses through controlled MUI autosize)

frontend/src/app/pages/AgentChat/ChatInput/view/PastePreviewDialog.tsx

@@ -1,8 +1,7 @@
-import React, { useEffect, useState } from 'react';
+import React, { useState } from 'react';
 import Dialog from '@mui/material/Dialog';
 import Box from '@mui/material/Box';
 import Typography from '@mui/material/Typography';
-import TextField from '@mui/material/TextField';
 import { useClaudeTokens } from '@/shared/styles/ThemeContext';
 import { getPasteContent } from '@/app/components/editor/richEditorUtils';
 
@@ -12,25 +11,48 @@ interface Props {
   onSave: (pasteId: string, text: string) => void;
 }
 
+// Uncontrolled on purpose: huge pastes are this dialog's whole job, and a controlled MUI autosize field re-reconciles the full string + re-measures a shadow textarea per keystroke (typing molasses at ~300KB).
+const PasteEditor: React.FC<{ pasteId: string; initial: string; onSave: Props['onSave']; onCount: (n: number) => void }> = ({ pasteId, initial, onSave, onCount }) => {
+  const c = useClaudeTokens();
+  return (
+    <textarea
+      defaultValue={initial}
+      autoFocus
+      onChange={(e) => { onSave(pasteId, e.target.value); onCount(e.target.value.length); }}
+      style={{
+        width: '100%',
+        minHeight: '9rem',
+        maxHeight: '55vh',
+        height: '40vh',
+        resize: 'vertical',
+        overflowY: 'auto',
+        fontFamily: c.font.mono,
+        fontSize: '0.78rem',
+        lineHeight: 1.5,
+        color: c.text.primary,
+        background: 'transparent',
+        border: `1px solid ${c.border.subtle}`,
+        borderRadius: 8,
+        padding: '10px 12px',
+        outline: 'none',
+        boxSizing: 'border-box',
+      }}
+    />
+  );
+};
+
 export const PastePreviewDialog: React.FC<Props> = ({ pasteId, onClose, onSave }) => {
   const c = useClaudeTokens();
   const open = !!pasteId;
   const original = pasteId ? getPasteContent(pasteId) : undefined;
-  const [draft, setDraft] = useState('');
-
-  useEffect(() => {
-    setDraft(original ?? '');
-  }, [pasteId]);
-
-  const handleChange = (text: string) => {
-    setDraft(text);
-    if (pasteId) onSave(pasteId, text);
-  };
+  // Keyed by paste id so an id swap can never show the previous paste's count.
+  const [charCount, setCharCount] = useState<{ id: string; n: number } | null>(null);
+  const liveCount = charCount && charCount.id === pasteId ? charCount.n : null;
 
   return (
     <Dialog
       open={open}
-      onClose={onClose}
+      onClose={() => { setCharCount(null); onClose(); }}
       PaperProps={{ sx: { bgcolor: c.bg.elevated, borderRadius: 3, p: 0, minWidth: 520, maxWidth: 760, width: '70vw' } }}
     >
       <Box sx={{ p: 2, borderBottom: `1px solid ${c.border.subtle}` }}>
@@ -38,33 +60,17 @@ export const PastePreviewDialog: React.FC<Props> = ({ pasteId, onClose, onSave }
           Pasted text
         </Typography>
         <Typography sx={{ color: c.text.tertiary, fontSize: '0.75rem', mt: 0.25 }}>
-          {draft.length.toLocaleString()} characters
+          {(liveCount ?? original?.length ?? 0).toLocaleString()} characters
         </Typography>
       </Box>
       <Box sx={{ p: 2, bgcolor: c.bg.surface }}>
-        {original === undefined ? (
+        {original === undefined || pasteId === null ? (
           <Typography sx={{ color: c.text.tertiary, fontSize: '0.85rem', fontStyle: 'italic' }}>
             This pasted text is no longer available. Re-paste to restore it.
           </Typography>
         ) : (
-          <TextField
-            value={draft}
-            onChange={(e) => handleChange(e.target.value)}
-            multiline
-            fullWidth
-            minRows={6}
-            maxRows={20}
-            autoFocus
-            sx={{
-              '& .MuiInputBase-root': {
-                fontFamily: c.font.mono,
-                fontSize: '0.78rem',
-                color: c.text.primary,
-                alignItems: 'flex-start',
-              },
-              '& .MuiOutlinedInput-notchedOutline': { borderColor: c.border.subtle },
-            }}
-          />
+          // key remounts the editor per paste id, so a reopened dialog always seeds from the current stored content (no stale-draft sync effect to get wrong).
+          <PasteEditor key={pasteId} pasteId={pasteId} initial={original} onSave={onSave} onCount={(n) => setCharCount({ id: pasteId, n })} />
         )}
       </Box>
     </Dialog>