feat: open edit tool changes in VS Code diff view with line focus

Tool-card clicks for edit-like actions now open a VS Code diff instead of only the file
Diff view focuses the first changed line for faster review
Uses a virtual readonly original buffer to avoid opening unsaved draft tabs

packages/ui/src/components/chat/message/parts/ToolPart.tsx

@@ -232,6 +232,45 @@ const getFirstChangedLineFromMetadata = (tool: string, metadata?: Record<string,
     return undefined;
 };
 
+const getPrimaryDiffFromMetadata = (
+    tool: string,
+    metadata?: Record<string, unknown>,
+    preferredPath?: string,
+): string | undefined => {
+    if (!metadata || (tool !== 'edit' && tool !== 'multiedit' && tool !== 'apply_patch')) {
+        return undefined;
+    }
+
+    const files = Array.isArray(metadata.files) ? metadata.files : [];
+    if (files.length > 0) {
+        const preferred = typeof preferredPath === 'string' && preferredPath.length > 0
+            ? preferredPath
+            : undefined;
+        const matched = preferred
+            ? files.find((file) => {
+                if (!file || typeof file !== 'object') {
+                    return false;
+                }
+                const candidate = file as { relativePath?: unknown; filePath?: unknown };
+                return candidate.relativePath === preferred || candidate.filePath === preferred;
+            })
+            : files[0];
+
+        if (matched && typeof matched === 'object') {
+            const patch = (matched as { diff?: unknown }).diff;
+            if (typeof patch === 'string' && patch.trim().length > 0) {
+                return patch;
+            }
+        }
+    }
+
+    if (typeof metadata.diff === 'string' && metadata.diff.trim().length > 0) {
+        return metadata.diff;
+    }
+
+    return undefined;
+};
+
 const getRelativePath = (absolutePath: string, currentDirectory: string): string => {
     if (absolutePath.startsWith(currentDirectory)) {
         const relativePath = absolutePath.substring(currentDirectory.length);
@@ -1713,14 +1752,21 @@ const ToolPart: React.FC<ToolPartProps> = ({
 
         let filePath: unknown;
         let targetLine: number | undefined;
+        let toolDiff: string | undefined;
         if (part.tool === 'edit' || part.tool === 'multiedit') {
             filePath = input?.filePath || input?.file_path || input?.path || metadata?.filePath || metadata?.file_path || metadata?.path;
             targetLine = getFirstChangedLineFromMetadata(part.tool, metadata);
+            if (typeof filePath === 'string') {
+                toolDiff = getPrimaryDiffFromMetadata(part.tool, metadata, filePath);
+            }
         } else if (part.tool === 'apply_patch') {
             const files = Array.isArray(metadata?.files) ? metadata?.files : [];
             const firstFile = files[0] as { relativePath?: string; filePath?: string } | undefined;
             filePath = firstFile?.relativePath || firstFile?.filePath;
             targetLine = getFirstChangedLineFromMetadata(part.tool, metadata);
+            if (typeof filePath === 'string') {
+                toolDiff = getPrimaryDiffFromMetadata(part.tool, metadata, filePath);
+            }
         } else if (['write', 'create', 'file_write', 'read', 'view', 'file_read', 'cat'].includes(part.tool)) {
             filePath = input?.filePath || input?.file_path || input?.path || metadata?.filePath || metadata?.file_path || metadata?.path;
         }
@@ -1731,6 +1777,11 @@ const ToolPart: React.FC<ToolPartProps> = ({
             if (!filePath.startsWith('/')) {
                 absolutePath = currentDirectory.endsWith('/') ? currentDirectory + filePath : currentDirectory + '/' + filePath;
             }
+            if (runtime.runtime.isVSCode && toolDiff && (part.tool === 'edit' || part.tool === 'multiedit' || part.tool === 'apply_patch')) {
+                const label = `${getRelativePath(absolutePath, currentDirectory)} (changes)`;
+                void runtime.editor.openDiff('', absolutePath, label, { line: targetLine, patch: toolDiff });
+                return;
+            }
             runtime.editor.openFile(absolutePath, targetLine);
         } else {
             onToggle(part.id);