Ai stability and ux improvements

src/editor/Editor.js

@@ -717,7 +717,8 @@
      * @param {!string} text
      */
     Editor.prototype._resetText = function (text) {
-        var currentText = this._codeMirror.getValue();
+        var cm = this._codeMirror;
+        var currentText = cm.getValue();
 
         // compare with ignoring line-endings, issue #11826
         var textLF = text ? text.replace(/(\r\n|\r|\n)/g, "\n") : null;
@@ -732,14 +733,51 @@
         var cursorPos = this.getCursorPos(),
             scrollPos = this.getScrollPos();
 
-        // This *will* fire a change event, but we clear the undo immediately afterward
-        this._codeMirror.setValue(text);
-        this._codeMirror.refresh();
+        // First-time content load (e.g. opening a file): there's no useful
+        // undo state to preserve — fall back to setValue + clearHistory so
+        // the user can't ctrl-z into the empty doc that existed before open.
+        var isInitialLoad = currentText === "" && cm.historySize().undo === 0;
 
-        // Make sure we can't undo back to the empty state before setValue(), and mark
-        // the document clean.
-        this._codeMirror.clearHistory();
-        this._codeMirror.markClean();
+        if (isInitialLoad) {
+            cm.setValue(text);
+            cm.refresh();
+            cm.clearHistory();
+        } else {
+            // External-content reload (disk change, AI edit, git checkout, etc.):
+            // replace ONLY the differing middle of the document so the change
+            // is undoable AND CodeMirror marks outside the changed region are
+            // preserved. The latter matters for HTML files used in live
+            // preview (each rendered element holds a mark) — replacing the
+            // whole doc would clear every mark and force a full preview
+            // refresh on every edit.
+            //
+            // O(n) common prefix + suffix scan: cheap enough to apply to all
+            // languages, and AI edits are typically tiny relative to file size.
+            var prefixLen = 0;
+            var minLen = Math.min(currentText.length, text.length);
+            while (prefixLen < minLen &&
+                    currentText.charCodeAt(prefixLen) === text.charCodeAt(prefixLen)) {
+                prefixLen++;
+            }
+            var maxSuffix = Math.min(currentText.length - prefixLen, text.length - prefixLen);
+            var suffixLen = 0;
+            while (suffixLen < maxSuffix &&
+                    currentText.charCodeAt(currentText.length - 1 - suffixLen) ===
+                    text.charCodeAt(text.length - 1 - suffixLen)) {
+                suffixLen++;
+            }
+            var fromPos = cm.posFromIndex(prefixLen);
+            var toPos = cm.posFromIndex(currentText.length - suffixLen);
+            var middle = text.substring(prefixLen, text.length - suffixLen);
+            cm.operation(function () {
+                cm.replaceRange(middle, fromPos, toPos, "+disk");
+            });
+            cm.refresh();
+        }
+        // markClean sets the new "saved" generation — disk == buffer right
+        // now, so dirty=false. Undoing past this generation will re-mark
+        // dirty, exactly like a manual edit.
+        cm.markClean();
 
         // restore cursor and scroll positions
         this.setCursorPos(cursorPos);

src/nls/root/strings.js

@@ -2199,6 +2199,8 @@ define({
     "AI_CHAT_TOOL_SEARCHED": "Searched: {0}",
     "AI_CHAT_TOOL_GREP": "Grep: {0}",
     "AI_CHAT_TOOL_READ_FILE": "Read {0}",
+    "AI_CHAT_TOOL_READ_FILE_RANGE": "Read {0} lines {1}-{2}",
+    "AI_CHAT_TOOL_READ_FILE_FROM": "Read {0} from line {1}",
     "AI_CHAT_TOOL_EDIT_FILE": "Edit {0}",
     "AI_CHAT_TOOL_WRITE_FILE": "Write {0}",
     "AI_CHAT_TOOL_RAN_CMD": "Ran command",
@@ -2214,10 +2216,19 @@ define({
     "AI_CHAT_UNDO_TITLE": "Undo changes from this response",
     "AI_CHAT_RESTORE_TITLE": "Restore files to this point",
     "AI_CHAT_RESTORED": "Restored",
+    "AI_CHAT_TOOL_APPLIED_DIRECTLY": "Applied directly to disk · diff not available",
+    "AI_CHAT_TOOL_REJECTED": "Edit rejected — file not modified",
+    "AI_CHAT_TOOL_REJECTED_REASON": "Reason: {0}",
+    "AI_CHAT_FILE_NOT_FOUND_TITLE": "File not found",
+    "AI_CHAT_FILE_NOT_FOUND_MSG": "Could not open <span class=\"dialog-filename\">{0}</span>. The file may have been moved or deleted.",
     "AI_CHAT_UNDO_RESTORE_WARNING_TITLE": "AI Undo & Restore",
     "AI_CHAT_UNDO_RESTORE_WARNING_BODY": "This will only undo changes made by the AI. Changes made outside the AI won’t be restored and may be lost. For full version history, use version control like Git.",
     "AI_CHAT_SHOW_DIFF": "Show diff",
     "AI_CHAT_HIDE_DIFF": "Hide diff",
+    "AI_CHAT_DIFF_MORE_TITLE": "Diff options",
+    "AI_CHAT_DIFF_EXPAND_ALL": "Expand all",
+    "AI_CHAT_DIFF_COLLAPSE_ALL": "Collapse all",
+    "AI_CHAT_DIFF_ALWAYS_SHOW": "Always show",
     "AI_CHAT_LABEL_YOU": "You",
     "AI_CHAT_LABEL_CLAUDE": "Claude",
     "AI_CHAT_SEND_ERROR": "Failed to send message: {0}",
@@ -2255,6 +2266,12 @@ define({
     "AI_CHAT_BASH_DENY": "Deny",
     "AI_CHAT_BASH_ALLOWED": "Command allowed",
     "AI_CHAT_BASH_DENIED": "Command denied",
+    "AI_CHAT_PLAN_WRITE_CONFIRM_TITLE": "Switch to Edit Mode?",
+    "AI_CHAT_PLAN_WRITE_CONFIRM_BODY": "Claude wants to edit {0}. You're currently in Plan Mode.",
+    "AI_CHAT_PLAN_WRITE_ALLOW": "Allow & Switch to Edit Mode",
+    "AI_CHAT_PLAN_WRITE_STAY": "Stay in Plan Mode",
+    "AI_CHAT_PLAN_WRITE_ALLOWED": "Switched to Edit Mode",
+    "AI_CHAT_PLAN_WRITE_STAYED": "Stayed in Plan Mode",
     "AI_CHAT_CODE_DEFAULT_LANG": "text",
     "AI_CHAT_CODE_COLLAPSE": "Collapse",
     "AI_CHAT_CODE_EXPAND": "Expand",