refactor(core): isolate specific agent changes

Author: adamfweidman

packages/core/src/agent/content-utils.test.ts

@@ -8,7 +8,6 @@ import { describe, expect, it } from 'vitest';
 import {
   geminiPartsToContentParts,
   contentPartsToGeminiParts,
-  toolResultDisplayToContentParts,
   buildToolResponseData,
 } from './content-utils.js';
 import type { Part } from '@google/genai';
@@ -200,27 +199,6 @@ describe('contentPartsToGeminiParts', () => {
   });
 });
 
-describe('toolResultDisplayToContentParts', () => {
-  it('returns undefined for undefined', () => {
-    expect(toolResultDisplayToContentParts(undefined)).toBeUndefined();
-  });
-
-  it('returns undefined for null', () => {
-    expect(toolResultDisplayToContentParts(null)).toBeUndefined();
-  });
-
-  it('handles string resultDisplay as-is', () => {
-    const result = toolResultDisplayToContentParts('File written');
-    expect(result).toEqual([{ type: 'text', text: 'File written' }]);
-  });
-
-  it('stringifies object resultDisplay', () => {
-    const display = { type: 'FileDiff', oldPath: 'a.ts', newPath: 'b.ts' };
-    const result = toolResultDisplayToContentParts(display);
-    expect(result).toEqual([{ type: 'text', text: JSON.stringify(display) }]);
-  });
-});
-
 describe('buildToolResponseData', () => {
   it('preserves outputFile and contentLength', () => {
     const result = buildToolResponseData({

packages/core/src/agent/content-utils.ts

@@ -105,24 +105,6 @@ export function contentPartsToGeminiParts(content: ContentPart[]): Part[] {
   return result;
 }
 
-/**
- * Converts a ToolCallResponseInfo.resultDisplay value into ContentPart[].
- * Handles string, object-valued (FileDiff, SubagentProgress, etc.),
- * and undefined resultDisplay consistently.
- */
-export function toolResultDisplayToContentParts(
-  resultDisplay: unknown,
-): ContentPart[] | undefined {
-  if (resultDisplay === undefined || resultDisplay === null) {
-    return undefined;
-  }
-  const text =
-    typeof resultDisplay === 'string'
-      ? resultDisplay
-      : JSON.stringify(resultDisplay);
-  return [{ type: 'text', text }];
-}
-
 /**
  * Builds the data record for a tool_response AgentEvent, preserving
  * all available metadata from the ToolCallResponseInfo.

packages/core/src/agent/event-translator.test.ts

@@ -155,9 +155,10 @@ describe('translateEvent', () => {
       expect(resp.content).toEqual([
         { type: 'text', text: 'Permission denied to write' },
       ]);
-      expect(resp.displayContent).toEqual([
-        { type: 'text', text: 'Permission denied' },
-      ]);
+      expect(resp.display?.result).toEqual({
+        type: 'text',
+        text: 'Permission denied',
+      });
       expect(resp.data).toEqual({ errorType: 'permission_denied' });
     });
 
@@ -200,9 +201,12 @@ describe('translateEvent', () => {
       };
       const result = translateEvent(event, state);
       const resp = result[0] as AgentEvent<'tool_response'>;
-      expect(resp.displayContent).toEqual([
-        { type: 'text', text: JSON.stringify(objectDisplay) },
-      ]);
+      expect(resp.display?.result).toEqual({
+        type: 'diff',
+        path: '/tmp/test.txt',
+        beforeText: 'a',
+        afterText: 'b',
+      });
     });
 
     it('passes through string resultDisplay as-is', () => {
@@ -220,9 +224,10 @@ describe('translateEvent', () => {
       };
       const result = translateEvent(event, state);
       const resp = result[0] as AgentEvent<'tool_response'>;
-      expect(resp.displayContent).toEqual([
-        { type: 'text', text: 'Command output text' },
-      ]);
+      expect(resp.display?.result).toEqual({
+        type: 'text',
+        text: 'Command output text',
+      });
     });
 
     it('preserves outputFile and contentLength in data', () => {
@@ -373,7 +378,7 @@ describe('translateEvent', () => {
       expect(err.type).toBe('error');
       expect(err.fatal).toBe(false);
       expect(err._meta?.['code']).toBe('AGENT_EXECUTION_BLOCKED');
-      expect(err.message).toBe('Agent execution blocked: Policy violation');
+      expect(err.message).toBe('Policy violation');
     });
 
     it('uses systemMessage in the final error message when available', () => {
@@ -388,9 +393,7 @@ describe('translateEvent', () => {
       };
       const result = translateEvent(event, state);
       const err = result[0] as AgentEvent<'error'>;
-      expect(err.message).toBe(
-        'Agent execution blocked: Blocked by policy hook',
-      );
+      expect(err.message).toBe('Blocked by policy hook');
     });
   });
 

packages/core/src/agent/event-translator.ts

@@ -25,12 +25,13 @@ import type {
   ErrorData,
   Usage,
   AgentEventType,
+  ToolDisplay,
 } from './types.js';
 import {
   geminiPartsToContentParts,
-  toolResultDisplayToContentParts,
   buildToolResponseData,
 } from './content-utils.js';
+import { toolResultDisplayToDisplayContent } from './tool-display-utils.js';
 
 // ---------------------------------------------------------------------------
 // Translation State
@@ -209,7 +210,7 @@ export function translateEvent(
       out.push(
         makeEvent('error', state, {
           status: 'PERMISSION_DENIED',
-          message: `Agent execution blocked: ${event.value.systemMessage?.trim() || event.value.reason}`,
+          message: event.value.systemMessage?.trim() || event.value.reason,
           fatal: false,
           _meta: { code: 'AGENT_EXECUTION_BLOCKED' },
         }),
@@ -235,16 +236,23 @@ export function translateEvent(
           requestId: event.value.callId,
           name: event.value.name,
           args: event.value.args,
+          display: event.value.display,
         }),
       );
       break;
 
     case GeminiEventType.ToolCallResponse: {
       ensureStreamStart(state, out);
-      const displayContent = toolResultDisplayToContentParts(
-        event.value.resultDisplay,
-      );
       const data = buildToolResponseData(event.value);
+      const display: ToolDisplay | undefined =
+        event.value.display ??
+        (event.value.resultDisplay
+          ? {
+              result: toolResultDisplayToDisplayContent(
+                event.value.resultDisplay,
+              ),
+            }
+          : undefined);
       out.push(
         makeEvent('tool_response', state, {
           requestId: event.value.callId,
@@ -253,7 +261,7 @@ export function translateEvent(
             ? [{ type: 'text', text: event.value.error.message }]
             : geminiPartsToContentParts(event.value.responseParts),
           isError: event.value.error !== undefined,
-          ...(displayContent ? { displayContent } : {}),
+          ...(display ? { display } : {}),
           ...(data ? { data } : {}),
         }),
       );
@@ -274,7 +282,6 @@ export function translateEvent(
       ((x: never) => {
         throw new Error(`Unhandled event type: ${JSON.stringify(x)}`);
       })(event);
-      break;
   }
 
   return out;

packages/core/src/agent/legacy-agent-session.test.ts

@@ -102,7 +102,10 @@ function makeCompletedToolCall(
     response: {
       callId,
       responseParts: [{ text: responseText }],
-      resultDisplay: undefined,
+      resultDisplay: responseText,
+      display: {
+        result: { type: 'text', text: responseText },
+      },
       error: undefined,
       errorType: undefined,
     },
@@ -200,7 +203,6 @@ describe('LegacyAgentSession', () => {
         expect.any(AbortSignal),
         'test-prompt',
         undefined,
-        false,
         'raw input',
       );
 
@@ -427,6 +429,12 @@ describe('LegacyAgentSession', () => {
         (e): e is AgentEvent<'tool_response'> => e.type === 'tool_response',
       );
       expect(toolResp?.name).toBe('read_file');
+      expect(toolResp?.display).toEqual(
+        expect.objectContaining({
+          name: 'read_file',
+          result: { type: 'text', text: 'file contents' },
+        }),
+      );
       expect(toolResp?.content).toEqual([
         { type: 'text', text: 'file contents' },
       ]);
@@ -489,9 +497,10 @@ describe('LegacyAgentSession', () => {
       expect(toolResp?.content).toEqual([
         { type: 'text', text: 'Permission denied' },
       ]);
-      expect(toolResp?.displayContent).toEqual([
-        { type: 'text', text: 'Error display' },
-      ]);
+      expect(toolResp?.display?.result).toEqual({
+        type: 'text',
+        text: 'Error display',
+      });
     });
 
     it('stops on STOP_EXECUTION tool error', async () => {
@@ -646,7 +655,7 @@ describe('LegacyAgentSession', () => {
           e.type === 'error' && e._meta?.['code'] === 'AGENT_EXECUTION_BLOCKED',
       );
       expect(blocked?.fatal).toBe(false);
-      expect(blocked?.message).toBe('Agent execution blocked: Blocked by hook');
+      expect(blocked?.message).toBe('Blocked by hook');
 
       const messages = events.filter(
         (e): e is AgentEvent<'message'> =>

packages/core/src/agent/legacy-agent-session.ts

@@ -23,8 +23,8 @@ import {
   buildToolResponseData,
   contentPartsToGeminiParts,
   geminiPartsToContentParts,
-  toolResultDisplayToContentParts,
 } from './content-utils.js';
+import { populateToolDisplay } from './tool-display-utils.js';
 import { AgentSession } from './agent-session.js';
 import {
   createTranslationState,
@@ -197,7 +197,6 @@ export class LegacyAgentProtocol implements AgentProtocol {
         this._abortController.signal,
         this._promptId,
         undefined,
-        false,
         currentDisplayContent,
       );
       currentDisplayContent = undefined;
@@ -263,9 +262,13 @@ export class LegacyAgentProtocol implements AgentProtocol {
         const content: ContentPart[] = response.error
           ? [{ type: 'text', text: response.error.message }]
           : geminiPartsToContentParts(response.responseParts);
-        const displayContent = toolResultDisplayToContentParts(
-          response.resultDisplay,
-        );
+        const display = populateToolDisplay({
+          name: request.name,
+          invocation: 'invocation' in tc ? tc.invocation : undefined,
+          resultDisplay: response.resultDisplay,
+          displayName: 'tool' in tc ? tc.tool?.displayName : undefined,
+          display: response.display,
+        });
         const data = buildToolResponseData(response);
 
         this._emit([
@@ -274,7 +277,7 @@ export class LegacyAgentProtocol implements AgentProtocol {
             name: request.name,
             content,
             isError: response.error !== undefined,
-            ...(displayContent ? { displayContent } : {}),
+            ...(display ? { display } : {}),
             ...(data ? { data } : {}),
           }),
         ]);