Subagent activity UX. (#17570)

packages/core/src/utils/tool-utils.test.ts

@@ -98,6 +98,17 @@ describe('shouldHideToolCall', () => {
       ).toBe(!visible);
     },
   );
+
+  it('hides tool calls with a parentCallId', () => {
+    expect(
+      shouldHideToolCall({
+        displayName: 'any_tool',
+        status: CoreToolCallStatus.Success,
+        hasResultDisplay: true,
+        parentCallId: 'some-parent',
+      }),
+    ).toBe(true);
+  });
 });
 
 describe('getToolSuggestion', () => {

packages/core/src/utils/tool-utils.ts

@@ -28,20 +28,28 @@ export interface ShouldHideToolCallParams {
   approvalMode?: ApprovalMode;
   /** Whether the tool has produced a result for display. */
   hasResultDisplay: boolean;
+  /** The ID of the parent tool call, if any. */
+  parentCallId?: string;
 }
 
 /**
  * Determines if a tool call should be hidden from the standard tool history UI.
  *
  * We hide tools in several cases:
- * 1. Ask User tools that are in progress, displayed via specialized UI.
- * 2. Ask User tools that errored without result display, typically param
+ * 1. Tool calls that have a parent, as they are "internal" to another tool (e.g. subagent).
+ * 2. Ask User tools that are in progress, displayed via specialized UI.
+ * 3. Ask User tools that errored without result display, typically param
  *    validation errors that the agent automatically recovers from.
- * 3. WriteFile and Edit tools when in Plan Mode, redundant because the
+ * 4. WriteFile and Edit tools when in Plan Mode, redundant because the
  *    resulting plans are displayed separately upon exiting plan mode.
  */
 export function shouldHideToolCall(params: ShouldHideToolCallParams): boolean {
-  const { displayName, status, approvalMode, hasResultDisplay } = params;
+  const { displayName, status, approvalMode, hasResultDisplay, parentCallId } =
+    params;
+
+  if (parentCallId) {
+    return true;
+  }
 
   switch (displayName) {
     case ASK_USER_DISPLAY_NAME: