fix(web-shell): prefer raw file diffs in tool output (#5992)

Co-authored-by: ytahdn <ytahdn@gmail.com>

packages/web-shell/client/components/messages/ToolGroup.test.tsx

@@ -13,6 +13,7 @@ vi.mock('../../App', async () => {
 
 const {
   buildUnifiedDiff,
+  extractDiff,
   formatToolGroupSummary,
   getActiveTool,
   getRawFileDiff,
@@ -184,6 +185,32 @@ describe('tool output logic', () => {
     ).toBe('');
   });
 
+  it('prefers raw fileDiff over content old/new text', () => {
+    const fileDiff =
+      'Index: file.ts\n@@ -10,1 +10,2 @@\n old context\n+precise line';
+
+    expect(
+      extractDiff(
+        makeTool({
+          toolName: 'edit',
+          content: [
+            {
+              type: 'diff',
+              oldText: 'full old text',
+              newText: 'full new text',
+            },
+          ],
+          rawOutput: {
+            fileDiff,
+            fileName: 'file.ts',
+            originalContent: 'full old text',
+            newContent: 'full new text',
+          },
+        }),
+      ),
+    ).toBe(fileDiff);
+  });
+
   it('builds a unified diff for changed content blocks', () => {
     expect(buildUnifiedDiff('same\nold', 'same\nnew')).toBe(
       ' same\n-old\n+new',

packages/web-shell/client/components/messages/ToolGroup.tsx

@@ -110,14 +110,18 @@ function hasEditContent(tool: ACPToolCall): boolean {
   return hasDiffContent(tool) || !!extractText(tool);
 }
 
-function extractDiff(tool: ACPToolCall): string {
+export function extractDiff(tool: ACPToolCall): string {
+  const rawFileDiff = getRawFileDiff(tool);
+  if (rawFileDiff) return rawFileDiff;
+
   if (tool.content) {
     const diffBlock = tool.content.find((b) => b.type === 'diff');
     if (diffBlock && diffBlock.type === 'diff') {
       return buildUnifiedDiff(diffBlock.oldText || '', diffBlock.newText || '');
     }
   }
-  return getRawFileDiff(tool);
+
+  return '';
 }
 
 export function getRawFileDiff(tool: ACPToolCall): string {