fix: subagent tool call messages

packages/core/src/subagents/subagent-events.ts

@@ -9,6 +9,7 @@ import type {
   ToolCallConfirmationDetails,
   ToolConfirmationOutcome,
 } from '../tools/tools.js';
+import type { Part } from '@google/genai';
 
 export type SubAgentEvent =
   | 'start'
@@ -72,7 +73,7 @@ export interface SubAgentToolResultEvent {
   name: string;
   success: boolean;
   error?: string;
-  resultDisplay?: string;
+  responseParts?: Part[];
   durationMs?: number;
   timestamp: number;
 }

packages/core/src/subagents/subagent.ts

@@ -619,11 +619,7 @@ export class SubAgentScope {
             name: toolName,
             success,
             error: errorMessage,
-            resultDisplay: call.response.resultDisplay
-              ? typeof call.response.resultDisplay === 'string'
-                ? call.response.resultDisplay
-                : JSON.stringify(call.response.resultDisplay)
-              : undefined,
+            responseParts: call.response.responseParts,
             durationMs: duration,
             timestamp: Date.now(),
           } as SubAgentToolResultEvent);