feat: use sudo fallback for tailscale configuration commands

To avoid permission denied errors when modifying Tailscale configuration (serve/funnel),
we now attempt the command directly first. If it fails, we catch the error and retry
with `sudo -n`. This preserves existing behavior for users where it works, but
attempts to escalate privileges (non-interactively) if needed.

- Added `execWithSudoFallback` helper in `src/infra/tailscale.ts`.
- Updated `ensureFunnel`, `enableTailscaleServe`, `disableTailscaleServe`,
  `enableTailscaleFunnel`, and `disableTailscaleFunnel` to use the fallback helper.
- Added tests in `src/infra/tailscale.test.ts` to verify fallback behavior.

src/infra/tailscale.test.ts

@@ -1,6 +1,15 @@
 import { describe, expect, it, vi } from "vitest";
 
-import { ensureGoInstalled, ensureTailscaledInstalled, getTailnetHostname } from "./tailscale.js";
+import {
+  ensureGoInstalled,
+  ensureTailscaledInstalled,
+  getTailnetHostname,
+  enableTailscaleServe,
+  disableTailscaleServe,
+  enableTailscaleFunnel,
+  disableTailscaleFunnel,
+  ensureFunnel
+} from "./tailscale.js";
 
 describe("tailscale helpers", () => {
   it("parses DNS name from tailscale status", async () => {
@@ -48,4 +57,100 @@ describe("tailscale helpers", () => {
     await ensureTailscaledInstalled(exec as never, prompt, runtime);
     expect(exec).toHaveBeenCalledWith("brew", ["install", "tailscale"]);
   });
+
+  it("enableTailscaleServe attempts normal first, then sudo", async () => {
+    // 1. First attempt fails
+    // 2. Second attempt (sudo) succeeds
+    const exec = vi.fn()
+      .mockRejectedValueOnce(new Error("permission denied"))
+      .mockResolvedValueOnce({ stdout: "" });
+
+    await enableTailscaleServe(3000, exec as never);
+
+    expect(exec).toHaveBeenNthCalledWith(
+      1,
+      "tailscale",
+      expect.arrayContaining(["serve", "--bg", "--yes", "3000"]),
+      expect.any(Object)
+    );
+
+    expect(exec).toHaveBeenNthCalledWith(
+      2,
+      "sudo",
+      expect.arrayContaining(["-n", "tailscale", "serve", "--bg", "--yes", "3000"]),
+      expect.any(Object)
+    );
+  });
+
+  it("enableTailscaleServe does NOT use sudo if first attempt succeeds", async () => {
+    const exec = vi.fn().mockResolvedValue({ stdout: "" });
+
+    await enableTailscaleServe(3000, exec as never);
+
+    expect(exec).toHaveBeenCalledTimes(1);
+    expect(exec).toHaveBeenCalledWith(
+      "tailscale",
+      expect.arrayContaining(["serve", "--bg", "--yes", "3000"]),
+      expect.any(Object)
+    );
+  });
+
+  it("disableTailscaleServe uses fallback", async () => {
+    const exec = vi.fn()
+      .mockRejectedValueOnce(new Error("failed"))
+      .mockResolvedValueOnce({ stdout: "" });
+
+    await disableTailscaleServe(exec as never);
+
+    expect(exec).toHaveBeenCalledTimes(2);
+    expect(exec).toHaveBeenNthCalledWith(
+      2,
+      "sudo",
+      expect.arrayContaining(["-n", "tailscale", "serve", "reset"]),
+      expect.any(Object)
+    );
+  });
+
+  it("ensureFunnel uses fallback for enabling", async () => {
+    // Mock exec:
+    // 1. status (success)
+    // 2. enable (fails)
+    // 3. enable sudo (success)
+    const exec = vi.fn()
+      .mockResolvedValueOnce({ stdout: JSON.stringify({ BackendState: "Running" }) }) // status
+      .mockRejectedValueOnce(new Error("failed")) // enable normal
+      .mockResolvedValueOnce({ stdout: "" }); // enable sudo
+
+    const runtime = {
+      error: vi.fn(),
+      log: vi.fn(),
+      exit: vi.fn() as unknown as (code: number) => never,
+    };
+    const prompt = vi.fn();
+
+    await ensureFunnel(8080, exec as never, runtime, prompt);
+
+    // 1. status
+    expect(exec).toHaveBeenNthCalledWith(
+      1,
+      "tailscale",
+      expect.arrayContaining(["funnel", "status", "--json"])
+    );
+
+    // 2. enable normal
+    expect(exec).toHaveBeenNthCalledWith(
+      2,
+      "tailscale",
+      expect.arrayContaining(["funnel", "--yes", "--bg", "8080"]),
+      expect.any(Object)
+    );
+
+    // 3. enable sudo
+    expect(exec).toHaveBeenNthCalledWith(
+      3,
+      "sudo",
+      expect.arrayContaining(["-n", "tailscale", "funnel", "--yes", "--bg", "8080"]),
+      expect.any(Object)
+    );
+  });
 });

src/infra/tailscale.ts

@@ -206,6 +206,25 @@ export async function ensureTailscaledInstalled(
   await exec("brew", ["install", "tailscale"]);
 }
 
+// Helper to attempt a command, and retry with sudo if it fails.
+async function execWithSudoFallback(
+  exec: typeof runExec,
+  bin: string,
+  args: string[],
+  opts: { maxBuffer?: number; timeoutMs?: number },
+): Promise<{ stdout: string; stderr: string }> {
+  try {
+    return await exec(bin, args, opts);
+  } catch (err) {
+    // If the error suggests permission denied or access denied, try with sudo.
+    // Or honestly, for any error in these specific ops, trying sudo is a reasonable fallback
+    // given the context of what we're doing (system-level network config).
+    // We'll log a verbose message that we're falling back.
+    logVerbose(`Command failed, retrying with sudo: ${bin} ${args.join(" ")}`);
+    return await exec("sudo", ["-n", bin, ...args], opts);
+  }
+}
+
 export async function ensureFunnel(
   port: number,
   exec: typeof runExec = runExec,
@@ -237,10 +256,16 @@ export async function ensureFunnel(
     }
 
     logVerbose(`Enabling funnel on port ${port}…`);
-    const { stdout } = await exec("sudo", ["-n", tailscaleBin, "funnel", "--yes", "--bg", `${port}`], {
-      maxBuffer: 200_000,
-      timeoutMs: 15_000,
-    });
+    // Attempt with fallback
+    const { stdout } = await execWithSudoFallback(
+      exec,
+      tailscaleBin,
+      ["funnel", "--yes", "--bg", `${port}`],
+      {
+        maxBuffer: 200_000,
+        timeoutMs: 15_000,
+      },
+    );
     if (stdout.trim()) console.log(stdout.trim());
   } catch (err) {
     const errOutput = err as { stdout?: unknown; stderr?: unknown };
@@ -288,32 +313,52 @@ export async function ensureFunnel(
 
 export async function enableTailscaleServe(port: number, exec: typeof runExec = runExec) {
   const tailscaleBin = await getTailscaleBinary();
-  await exec("sudo", ["-n", tailscaleBin, "serve", "--bg", "--yes", `${port}`], {
-    maxBuffer: 200_000,
-    timeoutMs: 15_000,
-  });
+  await execWithSudoFallback(
+    exec,
+    tailscaleBin,
+    ["serve", "--bg", "--yes", `${port}`],
+    {
+      maxBuffer: 200_000,
+      timeoutMs: 15_000,
+    },
+  );
 }
 
 export async function disableTailscaleServe(exec: typeof runExec = runExec) {
   const tailscaleBin = await getTailscaleBinary();
-  await exec("sudo", ["-n", tailscaleBin, "serve", "reset"], {
-    maxBuffer: 200_000,
-    timeoutMs: 15_000,
-  });
+  await execWithSudoFallback(
+    exec,
+    tailscaleBin,
+    ["serve", "reset"],
+    {
+      maxBuffer: 200_000,
+      timeoutMs: 15_000,
+    },
+  );
 }
 
 export async function enableTailscaleFunnel(port: number, exec: typeof runExec = runExec) {
   const tailscaleBin = await getTailscaleBinary();
-  await exec("sudo", ["-n", tailscaleBin, "funnel", "--bg", "--yes", `${port}`], {
-    maxBuffer: 200_000,
-    timeoutMs: 15_000,
-  });
+  await execWithSudoFallback(
+    exec,
+    tailscaleBin,
+    ["funnel", "--bg", "--yes", `${port}`],
+    {
+      maxBuffer: 200_000,
+      timeoutMs: 15_000,
+    },
+  );
 }
 
 export async function disableTailscaleFunnel(exec: typeof runExec = runExec) {
   const tailscaleBin = await getTailscaleBinary();
-  await exec("sudo", ["-n", tailscaleBin, "funnel", "reset"], {
-    maxBuffer: 200_000,
-    timeoutMs: 15_000,
-  });
+  await execWithSudoFallback(
+    exec,
+    tailscaleBin,
+    ["funnel", "reset"],
+    {
+      maxBuffer: 200_000,
+      timeoutMs: 15_000,
+    },
+  );
 }