use customize

Author: anthonykim1

extensions/copilot/src/extension/chatSessions/copilotcli/node/copilotcliSessionService.ts

@@ -891,10 +891,16 @@ export class CopilotCLISessionService extends Disposable implements ICopilotCLIS
 		]);
 		const customAgents = agentInfos.map(i => i.agent);
 		const variablesContext = this._promptVariablesService.buildTemplateVariablesContext(options.sessionId, options.debugTargetSessionIds);
-		const systemMessageContent = variablesContext
-			? `${variablesContext}\n\n${COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE}`
-			: COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE;
-		const systemMessage = { mode: 'append' as const, content: systemMessageContent };
+		const systemMessage = {
+			mode: 'customize' as const,
+			sections: {
+				identity: {
+					action: 'replace' as const,
+					content: COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE,
+				},
+			},
+			...(variablesContext ? { content: variablesContext } : undefined),
+		};
 
 		const allOptions: SessionOptions = {
 			clientName: 'vscode',

extensions/copilot/src/extension/chatSessions/copilotcli/node/test/copilotCliSessionService.spec.ts

@@ -256,21 +256,35 @@ describe('CopilotCLISessionService', () => {
 
 			const callArgs = createSessionSpy.mock.calls[0][0];
 			expect(callArgs.systemMessage).toEqual({
-				mode: 'append',
-				content: COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE,
+				mode: 'customize',
+				sections: {
+					identity: {
+						action: 'replace',
+						content: COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE,
+					},
+				},
 			});
 		});
 
-		it('preserves prompt variable context before the VS Code Copilot CLI identity system message', async () => {
+		it('preserves prompt variable context separately from the VS Code Copilot CLI identity system message', async () => {
 			const variableContext = 'Resolved template variables are available here.';
 			vi.spyOn(NullPromptVariablesService.prototype, 'buildTemplateVariablesContext').mockReturnValue(variableContext);
 			const createSessionSpy = vi.spyOn(manager, 'createSession');
 			await service.createSession({ model: 'gpt-test', ...sessionOptionsFor(URI.file('/tmp')) }, CancellationToken.None);
 
-			const content = createSessionSpy.mock.calls[0][0].systemMessage?.content;
-			expect(content).toContain(variableContext);
-			expect(content).toContain(COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE);
-			expect(content!.indexOf(variableContext)).toBeLessThan(content!.indexOf(COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE));
+			const systemMessage = createSessionSpy.mock.calls[0][0].systemMessage;
+			expect(systemMessage?.mode).toBe('customize');
+			if (systemMessage?.mode !== 'customize') {
+				throw new Error('Expected customize-mode system message');
+			}
+			const identity = systemMessage.sections?.identity;
+			expect(identity?.action).toBe('replace');
+			if (identity?.action !== 'replace') {
+				throw new Error('Expected replace identity section override');
+			}
+			expect(systemMessage.content).toBe(variableContext);
+			expect(identity.content).toBe(COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE);
+			expect(identity.content).not.toContain(variableContext);
 		});
 
 		it('passes reasoningEffort to session manager when provided', async () => {
@@ -314,8 +328,13 @@ describe('CopilotCLISessionService', () => {
 
 			expect(getSessionSpy).toHaveBeenCalledWith(expect.objectContaining({
 				systemMessage: {
-					mode: 'append',
-					content: COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE,
+					mode: 'customize',
+					sections: {
+						identity: {
+							action: 'replace',
+							content: COPILOT_CLI_CHAT_PANEL_SYSTEM_MESSAGE,
+						},
+					},
 				},
 			}), true);
 		});

src/vs/platform/agentHost/node/copilot/copilotAgent.ts

@@ -85,8 +85,13 @@ const ReasoningEfforts = ['low', 'medium', 'high', 'xhigh'] as const;
 type ReasoningEffort = NonNullable<SessionConfig['reasoningEffort']>;
 
 export const COPILOT_AGENT_HOST_SYSTEM_MESSAGE = {
-	mode: 'append',
-	content: 'You are an AI assistant using Copilot CLI runtime in VS Code. When referring to yourself or this integration, do not describe yourself as a terminal assistant. When asked about your identity, you must state that you are an AI assistant using Copilot CLI runtime in VS Code.',
+	mode: 'customize',
+	sections: {
+		identity: {
+			action: 'replace',
+			content: 'You are an AI assistant using Copilot CLI runtime in VS Code. When referring to yourself or this integration, do not describe yourself as a terminal assistant. When asked about your identity, you must state that you are an AI assistant using Copilot CLI runtime in VS Code.',
+		},
+	},
 } satisfies NonNullable<ResumeSessionConfig['systemMessage']>;
 
 interface ISerializedModelSelection {

src/vs/platform/agentHost/test/node/copilotAgent.test.ts

@@ -699,7 +699,16 @@ suite('CopilotAgent', () => {
 				await agent.sendMessage(result.session, 'hello');
 
 				assert.ok(capturedConfig, 'SDK createSession should be called during provisional materialization');
-				assert.deepStrictEqual(capturedConfig.systemMessage, COPILOT_AGENT_HOST_SYSTEM_MESSAGE);
+				const systemMessage = capturedConfig.systemMessage;
+				assert.deepStrictEqual(systemMessage, COPILOT_AGENT_HOST_SYSTEM_MESSAGE);
+				if (!systemMessage || systemMessage.mode !== 'customize') {
+					assert.fail('Expected customize-mode system message');
+				}
+				assert.strictEqual(systemMessage.sections?.identity?.action, 'replace');
+				assert.strictEqual(
+					systemMessage.sections?.identity?.content,
+					'You are an AI assistant using Copilot CLI runtime in VS Code. When referring to yourself or this integration, do not describe yourself as a terminal assistant. When asked about your identity, you must state that you are an AI assistant using Copilot CLI runtime in VS Code.'
+				);
 			} finally {
 				await disposeAgent(agent);
 			}