feat(core): improve subagent result display (#20378)

packages/core/src/agents/browser/browserAgentInvocation.ts

@@ -17,6 +17,7 @@
 import { randomUUID } from 'node:crypto';
 import type { Config } from '../../config/config.js';
 import { LocalAgentExecutor } from '../local-executor.js';
+import { safeJsonToMarkdown } from '../../utils/markdownUtils.js';
 import {
   BaseToolInvocation,
   type ToolResult,
@@ -414,6 +415,8 @@ export class BrowserAgentInvocation extends BaseToolInvocation<
 
       const output = await executor.run(this.params, signal);
 
+      const displayResult = safeJsonToMarkdown(output.result);
+
       const resultContent = `Browser agent finished.
 Termination Reason: ${output.terminate_reason}
 Result:
@@ -425,7 +428,7 @@ Browser Agent Finished
 Termination Reason: ${output.terminate_reason}
 
 Result:
-${output.result}
+${displayResult}
 `;
 
       if (updateOutput) {

packages/core/src/agents/local-invocation.ts

@@ -6,6 +6,7 @@
 
 import type { Config } from '../config/config.js';
 import { LocalAgentExecutor } from './local-executor.js';
+import { safeJsonToMarkdown } from '../utils/markdownUtils.js';
 import {
   BaseToolInvocation,
   type ToolResult,
@@ -245,6 +246,8 @@ export class LocalSubagentInvocation extends BaseToolInvocation<
         throw cancelError;
       }
 
+      const displayResult = safeJsonToMarkdown(output.result);
+
       const resultContent = `Subagent '${this.definition.name}' finished.
 Termination Reason: ${output.terminate_reason}
 Result:
@@ -256,7 +259,7 @@ Subagent ${this.definition.name} Finished
 Termination Reason:\n ${output.terminate_reason}
 
 Result:
-${output.result}
+${displayResult}
 `;
 
       return {

packages/core/src/agents/remote-invocation.ts

@@ -25,6 +25,7 @@ import { extractIdsFromResponse, A2AResultReassembler } from './a2aUtils.js';
 import { GoogleAuth } from 'google-auth-library';
 import type { AuthenticationHandler } from '@a2a-js/sdk/client';
 import { debugLogger } from '../utils/debugLogger.js';
+import { safeJsonToMarkdown } from '../utils/markdownUtils.js';
 import type { AnsiOutput } from '../utils/terminalSerializer.js';
 import { A2AAuthProviderFactory } from './auth-provider/factory.js';
 
@@ -222,7 +223,7 @@ export class RemoteAgentInvocation extends BaseToolInvocation<
 
       return {
         llmContent: [{ text: finalOutput }],
-        returnDisplay: finalOutput,
+        returnDisplay: safeJsonToMarkdown(finalOutput),
       };
     } catch (error: unknown) {
       const partialOutput = reassembler.toString();