fix(cli): validate ACP tool allowlists after discovery

packages/coding-agent/src/main.ts

@@ -349,7 +349,7 @@ export interface AcpSessionFactoryOptions {
 	sessionDir?: string;
 	authStorage: AuthStorage;
 	modelRegistry: ModelRegistry;
-	parsedArgs: Pick<Args, "apiKey" | "trustedExtensions">;
+	parsedArgs: Pick<Args, "apiKey" | "trustedExtensions" | "tools">;
 	rawArgs: string[];
 	createSession: (options: CreateAgentSessionOptions) => Promise<CreateAgentSessionResult>;
 }
@@ -426,7 +426,7 @@ export function createAcpSessionFactory(args: AcpSessionFactoryOptions): AcpSess
 			args.authStorage.setRuntimeApiKey(nextSession.model.provider, args.parsedArgs.apiKey);
 		}
 		const runner = nextSession.extensionRunner;
-		applyExtensionFlags(
+		const reparsedArgs = applyExtensionFlags(
 			runner
 				? {
 						getFlags: () => runner.getFlags(),
@@ -437,6 +437,15 @@ export function createAcpSessionFactory(args: AcpSessionFactoryOptions): AcpSess
 				: undefined,
 			args.rawArgs,
 		);
+		const requestedTools = reparsedArgs?.tools ?? args.parsedArgs.tools;
+		if (requestedTools) {
+			try {
+				validateToolNames(requestedTools, nextSession.getAllToolNames());
+			} catch (error) {
+				await nextSession.dispose();
+				throw error;
+			}
+		}
 		return nextSession;
 	};
 }

packages/coding-agent/test/acp-mcp-isolation.test.ts

@@ -75,6 +75,43 @@ describe("createAcpSessionFactory MCP isolation (issue #1234)", () => {
 		}
 	});
 
+	it("rejects allowlisted tools absent from the completed ACP session registry", async () => {
+		const tempDir = TempDir.createSync("@pi-acp-tool-allowlist-");
+		let authStorage: AuthStorage | undefined;
+		try {
+			authStorage = await AuthStorage.create(tempDir.join("auth.db"));
+			const modelRegistry = new ModelRegistry(authStorage);
+			const settings = Settings.isolated({});
+			let disposed = false;
+			const fakeSession = {
+				extensionRunner: undefined,
+				getAllToolNames: () => ["read"],
+				dispose: async () => {
+					disposed = true;
+				},
+			} as unknown as AgentSession;
+			const factory = createAcpSessionFactory({
+				baseOptions: {} as CreateAgentSessionOptions,
+				settings,
+				sessionDir: tempDir.join("sessions"),
+				authStorage,
+				modelRegistry,
+				parsedArgs: { tools: ["read", "missing"] },
+				rawArgs: ["--tools", "read,missing"],
+				createSession: async () => ({ session: fakeSession }) as CreateAgentSessionResult,
+			});
+
+			await expect(factory(tempDir.path())).rejects.toThrow(/Unknown tool in --tools: missing/);
+			expect(disposed).toBe(true);
+		} finally {
+			try {
+				authStorage?.close();
+			} finally {
+				await tempDir.remove();
+			}
+		}
+	});
+
 	it("shares the trusted extension EventBus with the ACP session", async () => {
 		const tempDir = TempDir.createSync("@pi-acp-trusted-extension-");
 		let authStorage: AuthStorage | undefined;