fix: add gateway close context

src/gateway/call.test.ts

@@ -1,4 +1,4 @@
-import { beforeEach, describe, expect, it, vi } from "vitest";
+import { afterEach, beforeEach, describe, expect, it, vi } from "vitest";
 
 const loadConfig = vi.fn();
 const resolveGatewayPort = vi.fn();
@@ -7,7 +7,12 @@ const pickPrimaryTailnetIPv4 = vi.fn();
 let lastClientOptions: {
   url?: string;
   onHelloOk?: () => void | Promise<void>;
+  onClose?: (code: number, reason: string) => void;
 } | null = null;
+type StartMode = "hello" | "close" | "silent";
+let startMode: StartMode = "hello";
+let closeCode = 1006;
+let closeReason = "";
 
 vi.mock("../config/config.js", async (importOriginal) => {
   const actual = await importOriginal<typeof import("../config/config.js")>();
@@ -27,6 +32,7 @@ vi.mock("./client.js", () => ({
     constructor(opts: {
       url?: string;
       onHelloOk?: () => void | Promise<void>;
+      onClose?: (code: number, reason: string) => void;
     }) {
       lastClientOptions = opts;
     }
@@ -34,7 +40,11 @@ vi.mock("./client.js", () => ({
       return { ok: true };
     }
     start() {
-      void lastClientOptions?.onHelloOk?.();
+      if (startMode === "hello") {
+        void lastClientOptions?.onHelloOk?.();
+      } else if (startMode === "close") {
+        lastClientOptions?.onClose?.(closeCode, closeReason);
+      }
     }
     stop() {}
   },
@@ -48,6 +58,9 @@ describe("callGateway url resolution", () => {
     resolveGatewayPort.mockReset();
     pickPrimaryTailnetIPv4.mockReset();
     lastClientOptions = null;
+    startMode = "hello";
+    closeCode = 1006;
+    closeReason = "";
   });
 
   it("uses tailnet IP when local bind is tailnet", async () => {
@@ -80,3 +93,63 @@ describe("callGateway url resolution", () => {
     expect(lastClientOptions?.url).toBe("ws://127.0.0.1:18800");
   });
 });
+
+describe("callGateway error details", () => {
+  beforeEach(() => {
+    loadConfig.mockReset();
+    resolveGatewayPort.mockReset();
+    pickPrimaryTailnetIPv4.mockReset();
+    lastClientOptions = null;
+    startMode = "hello";
+    closeCode = 1006;
+    closeReason = "";
+  });
+
+  afterEach(() => {
+    vi.useRealTimers();
+  });
+
+  it("includes connection details when the gateway closes", async () => {
+    startMode = "close";
+    closeCode = 1006;
+    closeReason = "";
+    loadConfig.mockReturnValue({ gateway: { mode: "local", bind: "loopback" } });
+    resolveGatewayPort.mockReturnValue(18789);
+    pickPrimaryTailnetIPv4.mockReturnValue(undefined);
+
+    let err: Error | null = null;
+    try {
+      await callGateway({ method: "health" });
+    } catch (caught) {
+      err = caught as Error;
+    }
+
+    expect(err?.message).toContain("gateway closed (1006");
+    expect(err?.message).toContain("Gateway target: ws://127.0.0.1:18789");
+    expect(err?.message).toContain("Source: local loopback");
+    expect(err?.message).toContain("Bind: loopback");
+  });
+
+  it("includes connection details on timeout", async () => {
+    startMode = "silent";
+    loadConfig.mockReturnValue({ gateway: { mode: "local", bind: "loopback" } });
+    resolveGatewayPort.mockReturnValue(18789);
+    pickPrimaryTailnetIPv4.mockReturnValue(undefined);
+
+    vi.useFakeTimers();
+    let err: Error | null = null;
+    const promise = callGateway({ method: "health", timeoutMs: 5 }).catch(
+      (caught) => {
+        err = caught as Error;
+      },
+    );
+
+    await vi.advanceTimersByTimeAsync(5);
+    await promise;
+
+    expect(err?.message).toContain("gateway timeout after 5ms");
+    expect(err?.message).toContain("Gateway target: ws://127.0.0.1:18789");
+    expect(err?.message).toContain("Source: local loopback");
+    expect(err?.message).toContain("Bind: loopback");
+  });
+});