From 85c31ad2da57f2e7905ac64541f132aa0220749b Mon Sep 17 00:00:00 2001
From: mkorwel <matt.korwel@gmail.com>
Date: Wed, 11 Feb 2026 17:43:37 -0600
Subject: [PATCH] feat(cli): add --experimental-agent-harness command line flag
 #18267

---
 packages/cli/src/config/config.ts        | 9 ++++++++-
 packages/cli/src/gemini.test.tsx         | 1 +
 packages/core/src/agents/harness.test.ts | 8 ++++++--
 3 files changed, 15 insertions(+), 3 deletions(-)

diff --git a/packages/cli/src/config/config.ts b/packages/cli/src/config/config.ts
index 640212b061..50c10eec2a 100755
--- a/packages/cli/src/config/config.ts
+++ b/packages/cli/src/config/config.ts
@@ -78,6 +78,7 @@ export interface CliArgs {
   allowedMcpServerNames: string[] | undefined;
   allowedTools: string[] | undefined;
   experimentalAcp: boolean | undefined;
+  experimentalAgentHarness: boolean | undefined;
   extensions: string[] | undefined;
   listExtensions: boolean | undefined;
   resume: string | typeof RESUME_LATEST | undefined;
@@ -162,6 +163,10 @@ export async function parseArguments(
           type: 'boolean',
           description: 'Starts the agent in ACP mode',
         })
+        .option('experimental-agent-harness', {
+          type: 'boolean',
+          description: 'Enable the new unified agent harness',
+        })
         .option('allowed-mcp-server-names', {
           type: 'array',
           string: true,
@@ -788,7 +793,9 @@ export async function loadCliConfig(
     extensionLoader: extensionManager,
     enableExtensionReloading: settings.experimental?.extensionReloading,
     enableAgents: settings.experimental?.enableAgents,
-    enableAgentHarness: settings.experimental?.enableAgentHarness,
+    enableAgentHarness:
+      argv.experimentalAgentHarness ??
+      settings.experimental?.enableAgentHarness,
     plan: settings.experimental?.plan,
     enableEventDrivenScheduler: true,
     skillsSupport: settings.skills?.enabled ?? true,
diff --git a/packages/cli/src/gemini.test.tsx b/packages/cli/src/gemini.test.tsx
index 2e55c9b25d..62cb010d68 100644
--- a/packages/cli/src/gemini.test.tsx
+++ b/packages/cli/src/gemini.test.tsx
@@ -467,6 +467,7 @@ describe('gemini.tsx main function kitty protocol', () => {
       allowedMcpServerNames: undefined,
       allowedTools: undefined,
       experimentalAcp: undefined,
+      experimentalAgentHarness: undefined,
       extensions: undefined,
       listExtensions: undefined,
       includeDirectories: undefined,
diff --git a/packages/core/src/agents/harness.test.ts b/packages/core/src/agents/harness.test.ts
index 72682f9f0b..199c388cc0 100644
--- a/packages/core/src/agents/harness.test.ts
+++ b/packages/core/src/agents/harness.test.ts
@@ -10,7 +10,11 @@ import { makeFakeConfig } from '../test-utils/config.js';
 import { GeminiChat, StreamEventType } from '../core/geminiChat.js';
 import { GeminiEventType, type ServerGeminiStreamEvent } from '../core/turn.js';
 import { z } from 'zod';
-import { type LocalAgentDefinition, AgentTerminateMode } from './types.js';
+import {
+  type LocalAgentDefinition,
+  AgentTerminateMode,
+  type AgentDefinition,
+} from './types.js';
 import { scheduleAgentTools } from './agent-scheduler.js';
 import { logAgentFinish } from '../telemetry/loggers.js';
 import { type Config } from '../config/config.js';
@@ -72,7 +76,7 @@ describe('AgentHarness', () => {
 
     const harness = new AgentHarness({
       config: mockConfig,
-       
+
       definition: definition as unknown as AgentDefinition,
       inputs: {},
     });