fix(debug): preserve configured dap launch args

packages/coding-agent/src/dap/session.ts

@@ -289,7 +289,7 @@ export class DapSessionManager {
 				...(options.extraLaunchArguments ?? {}),
 				program: options.program,
 				cwd: options.cwd,
-				args: options.args,
+				...(options.args !== undefined ? { args: options.args } : {}),
 			};
 			// Subscribe to stop events BEFORE launching so we don't miss
 			// stopOnEntry events that arrive before we start listening.

packages/coding-agent/test/debug/dap-launch-failures.test.ts

@@ -62,6 +62,7 @@ class FakeDapClient {
 	readonly #exited = Promise.withResolvers<void>();
 	readonly #handlers = new Map<string, Set<DapEventHandler>>();
 	#alive = true;
+	requests: Array<{ command: string; args: unknown }> = [];
 
 	constructor(
 		readonly adapter: DapResolvedAdapter,
@@ -73,6 +74,7 @@ class FakeDapClient {
 			attachErrorDelayMs?: number;
 			configurationDoneError?: string;
 			rejectStopWaiters?: boolean;
+			stopAfterLaunch?: boolean;
 		},
 	) {
 		this.proc = {
@@ -95,7 +97,8 @@ class FakeDapClient {
 		return { supportsConfigurationDoneRequest: true };
 	}
 
-	async sendRequest(command: string): Promise<unknown> {
+	async sendRequest(command: string, args?: unknown): Promise<unknown> {
+		this.requests.push({ command, args });
 		if (command === "launch" && this.options.launchError) {
 			if (this.options.launchErrorDelayMs) await Bun.sleep(this.options.launchErrorDelayMs);
 			throw new Error(this.options.launchError);
@@ -107,6 +110,9 @@ class FakeDapClient {
 		if (command === "configurationDone" && this.options.configurationDoneError) {
 			throw new Error(this.options.configurationDoneError);
 		}
+		if (command === "launch" && this.options.stopAfterLaunch) {
+			queueMicrotask(() => this.#emit("stopped", { reason: "entry", threadId: 1 }));
+		}
 		return {};
 	}
 
@@ -158,6 +164,21 @@ afterEach(() => {
 });
 
 describe("DAP launch failure handling", () => {
+	it("preserves adapter launchDefaults args when launch omits args", async () => {
+		const adapter: DapResolvedAdapter = {
+			...TEST_ADAPTER,
+			launchDefaults: { request: "launch", args: ["--configured"], stopOnEntry: true },
+		};
+		const manager = new DapSessionManager();
+		const fake = new FakeDapClient(adapter, process.cwd(), { stopAfterLaunch: true });
+		spyOn(DapClient, "spawn").mockResolvedValue(fake as unknown as DapClient);
+
+		await manager.launch({ adapter, program: "/bin/echo", cwd: process.cwd() }, undefined, 10);
+
+		const launch = fake.requests.find(request => request.command === "launch");
+		expect(launch?.args).toMatchObject({ args: ["--configured"], program: "/bin/echo" });
+	});
+
 	it("surfaces the launch failure when configurationDone also fails", async () => {
 		const manager = new DapSessionManager();
 		const fake = new FakeDapClient(TEST_ADAPTER, process.cwd(), {