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);

packages/ui/src/lib/api/types.ts

@@ -598,7 +598,12 @@ export interface ToolsAPI {
 
 export interface EditorAPI {
   openFile(path: string, line?: number, column?: number): Promise<void>;
-  openDiff(original: string, modified: string, label?: string): Promise<void>;
+  openDiff(
+    original: string,
+    modified: string,
+    label?: string,
+    options?: { line?: number; patch?: string },
+  ): Promise<void>;
 }
 
 export interface VSCodeAPI {

packages/vscode/src/bridge.ts

@@ -169,6 +169,130 @@ const readUriAsAttachment = async (
   }
 };
 
+type ParsedDiffHunk = {
+  newStart: number;
+  oldLines: string[];
+  newLines: string[];
+};
+
+const VIRTUAL_DIFF_SCHEME = 'openchamber-diff';
+const virtualDiffContents = new Map<string, string>();
+let virtualDiffCounter = 0;
+let virtualDiffProviderDisposable: vscode.Disposable | null = null;
+
+const ensureVirtualDiffProviderRegistered = (ctx?: BridgeContext): void => {
+  if (virtualDiffProviderDisposable) {
+    return;
+  }
+
+  virtualDiffProviderDisposable = vscode.workspace.registerTextDocumentContentProvider(
+    VIRTUAL_DIFF_SCHEME,
+    {
+      provideTextDocumentContent: (uri: vscode.Uri) => {
+        const key = new URLSearchParams(uri.query).get('key') || '';
+        return virtualDiffContents.get(key) ?? '';
+      },
+    },
+  );
+
+  if (ctx?.context) {
+    ctx.context.subscriptions.push(virtualDiffProviderDisposable);
+  }
+};
+
+const createVirtualOriginalDiffUri = (modifiedPath: string, content: string): vscode.Uri => {
+  const key = `${Date.now()}-${++virtualDiffCounter}`;
+  virtualDiffContents.set(key, content);
+
+  if (virtualDiffContents.size > 100) {
+    const firstKey = virtualDiffContents.keys().next().value;
+    if (typeof firstKey === 'string') {
+      virtualDiffContents.delete(firstKey);
+    }
+  }
+
+  const fileName = path.basename(modifiedPath) || 'file';
+  return vscode.Uri.from({
+    scheme: VIRTUAL_DIFF_SCHEME,
+    path: `/${fileName} (before)`,
+    query: `key=${encodeURIComponent(key)}`,
+  });
+};
+
+const parseUnifiedDiffHunks = (patch: string): ParsedDiffHunk[] => {
+  if (typeof patch !== 'string' || patch.trim().length === 0) {
+    return [];
+  }
+
+  const lines = patch.split('\n');
+  const hunks: ParsedDiffHunk[] = [];
+  let current: ParsedDiffHunk | null = null;
+
+  for (const rawLine of lines) {
+    const line = rawLine.replace(/\r$/, '');
+    const headerMatch = line.match(/^@@\s+-\d+(?:,\d+)?\s+\+(\d+)(?:,\d+)?\s+@@/);
+    if (headerMatch) {
+      if (current) {
+        hunks.push(current);
+      }
+      const newStart = Number.parseInt(headerMatch[1] ?? '', 10);
+      current = {
+        newStart: Number.isFinite(newStart) ? Math.max(1, newStart) : 1,
+        oldLines: [],
+        newLines: [],
+      };
+      continue;
+    }
+
+    if (!current) {
+      continue;
+    }
+
+    if (line.startsWith(' ')) {
+      const text = line.slice(1);
+      current.oldLines.push(text);
+      current.newLines.push(text);
+      continue;
+    }
+
+    if (line.startsWith('+') && !line.startsWith('+++')) {
+      current.newLines.push(line.slice(1));
+      continue;
+    }
+
+    if (line.startsWith('-') && !line.startsWith('---')) {
+      current.oldLines.push(line.slice(1));
+      continue;
+    }
+  }
+
+  if (current) {
+    hunks.push(current);
+  }
+
+  return hunks;
+};
+
+const reconstructOriginalContentFromPatch = (modifiedContent: string, patch: string): string | null => {
+  const hunks = parseUnifiedDiffHunks(patch);
+  if (hunks.length === 0) {
+    return null;
+  }
+
+  const lines = modifiedContent.split('\n');
+  for (let index = hunks.length - 1; index >= 0; index -= 1) {
+    const hunk = hunks[index];
+    if (!hunk) {
+      continue;
+    }
+    const startIndex = Math.max(0, hunk.newStart - 1);
+    const replaceCount = hunk.newLines.length;
+    lines.splice(startIndex, replaceCount, ...hunk.oldLines);
+  }
+
+  return lines.join('\n');
+};
+
 const isPathInside = (candidatePath: string, parentPath: string): boolean => {
   const normalizedCandidate = path.resolve(candidatePath);
   const normalizedParent = path.resolve(parentPath);
@@ -2783,16 +2907,44 @@ export async function handleBridgeMessage(message: BridgeRequest, ctx?: BridgeCo
       }
 
       case 'editor:openDiff': {
-        const { original, modified, label } = payload as { original: string; modified: string; label?: string };
+        const { original, modified, label, line, patch } = payload as {
+          original: string;
+          modified: string;
+          label?: string;
+          line?: number;
+          patch?: string;
+        };
         try {
-          // If the paths are just content, we need to create virtual documents or temp files.
-          // However, 'editor:openDiff' usually implies comparing two URIs.
-          // If the payload contains file paths:
-          const originalUri = vscode.Uri.file(original);
           const modifiedUri = vscode.Uri.file(modified);
-          const title = label || `${path.basename(original)} ↔ ${path.basename(modified)}`;
-          
+          const modifiedDoc = await vscode.workspace.openTextDocument(modifiedUri);
+          let originalUri = original ? vscode.Uri.file(original) : modifiedUri;
+
+          if (typeof patch === 'string' && patch.trim().length > 0) {
+            const originalContent = reconstructOriginalContentFromPatch(modifiedDoc.getText(), patch);
+            if (typeof originalContent === 'string') {
+              ensureVirtualDiffProviderRegistered(ctx);
+              originalUri = createVirtualOriginalDiffUri(modified, originalContent);
+            }
+          }
+
+          const leftLabel = original ? path.basename(original) : `${path.basename(modified)} (before)`;
+          const title = label || `${leftLabel} ↔ ${path.basename(modified)}`;
+
           await vscode.commands.executeCommand('vscode.diff', originalUri, modifiedUri, title);
+
+          if (typeof line === 'number' && Number.isFinite(line)) {
+            const targetLine = Math.max(0, Math.trunc(line) - 1);
+            await new Promise((resolve) => setTimeout(resolve, 0));
+            const targetEditor = vscode.window.visibleTextEditors.find(
+              (editor) => editor.document.uri.toString() === modifiedUri.toString(),
+            );
+            if (targetEditor) {
+              const target = new vscode.Position(targetLine, 0);
+              targetEditor.selection = new vscode.Selection(target, target);
+              targetEditor.revealRange(new vscode.Range(target, target), vscode.TextEditorRevealType.InCenter);
+            }
+          }
+
           return { id, type, success: true };
         } catch (error) {
            const errorMessage = error instanceof Error ? error.message : String(error);

packages/vscode/webview/api/editor.ts

@@ -6,7 +6,13 @@ export const createVSCodeEditorAPI = (): EditorAPI => ({
   openFile: async (path: string, line?: number, column?: number) => {
     await sendBridgeMessage('editor:openFile', { path, line, column });
   },
-  openDiff: async (original: string, modified: string, label?: string) => {
-    await sendBridgeMessage('editor:openDiff', { original, modified, label });
+  openDiff: async (original: string, modified: string, label?: string, options?: { line?: number; patch?: string }) => {
+    await sendBridgeMessage('editor:openDiff', {
+      original,
+      modified,
+      label,
+      line: options?.line,
+      patch: options?.patch,
+    });
   },
 });