fix: make browser daemon setup work on Windows (#7) (#12)

The Unix socket daemon introduced in v0.6.0 made several POSIX-only
assumptions that break setup on Windows:

- protocol.ts hardcoded a Unix socket path (/tmp/pi-browser-daemon.sock).
  Node IPC on Windows requires a named pipe (\\.\pipe\<name>); a /tmp
  path is not a valid net listen/connect target there.
- spawn.ts spawned the bare tsx binary / `npx` and probed the non-Windows
  .bin/tsx shim. On Windows npm binaries are .cmd shims that must run via a
  shell, and spawning them directly fails with EINVAL / ENOENT.
- isDaemonRunning() pre-checked the socket with fs.access(), which always
  fails for a named pipe and would report a live daemon as dead.
- stale-socket unlink() would throw on a named pipe path.

Changes:
- DAEMON_SOCKET_PATH is now platform-aware: named pipe on win32, Unix
  socket elsewhere.
- spawnDaemon() resolves tsx.cmd / npx.cmd on Windows, runs via shell with
  per-token quoting (paths with spaces) and windowsVerbatimArguments.
- isDaemonRunning() skips the fs.access pre-check on Windows and probes the
  pipe directly.
- stale-socket cleanup is a no-op on Windows (named pipes self-clean).
- setup.ts daemon-failure message uses the actual DAEMON_SOCKET_PATH.

Closes #7

3 files changed, 60 insertions, 16 deletions

diff --git a/src/daemon/protocol.ts b/src/daemon/protocol.ts
index 9d777bc..4fa4a2a 100644
--- a/src/daemon/protocol.ts
+++ b/src/daemon/protocol.ts
@@ -133,8 +133,18 @@ export const deserialize = (line: string): WireMessage | null => {
 
 // ── Constants ──────────────────────────────────────────────────────────────────
 
-/** Filesystem path for the daemon's Unix domain socket. */
-export const DAEMON_SOCKET_PATH = "/tmp/pi-browser-daemon.sock";
+/**
+ * IPC endpoint for the daemon.
+ *
+ * On POSIX platforms this is a Unix domain socket path. On Windows, Node's IPC
+ * requires a named pipe of the form `\\.\pipe\<name>` — a Unix path like
+ * `/tmp/…` is not a valid `net` listen/connect target there and causes setup
+ * to fail. See https://nodejs.org/api/net.html#ipc-support.
+ */
+export const DAEMON_SOCKET_PATH =
+  process.platform === "win32"
+    ? "\\\\.\\pipe\\pi-browser-daemon"
+    : "/tmp/pi-browser-daemon.sock";
 
 /**
  * How long the daemon stays alive with zero connected clients before exiting
diff --git a/src/daemon/spawn.ts b/src/daemon/spawn.ts
index 0a2670c..d051fcc 100644
--- a/src/daemon/spawn.ts
+++ b/src/daemon/spawn.ts
@@ -19,6 +19,19 @@ import { DAEMON_SOCKET_PATH, serialize, type WireControl } from "./protocol";
 
 const moduleDir = dirname(fileURLToPath(import.meta.url));
 
+const isWindows = process.platform === "win32";
+
+/**
+ * Remove a stale POSIX socket file. On Windows the daemon endpoint is a named
+ * pipe, which is not a filesystem entry and is torn down automatically when the
+ * owning process exits — so there is nothing to unlink, and calling unlink on a
+ * pipe path throws. This is a no-op on Windows.
+ */
+const cleanupStaleSocket = (): void => {
+  if (isWindows) return;
+  unlink(DAEMON_SOCKET_PATH).catch(() => {});
+};
+
 /**
  * Check whether the daemon is running by probing its Unix socket.
  * A file-existence check is unreliable — a crashed daemon leaves a stale socket.
@@ -26,11 +39,15 @@ const moduleDir = dirname(fileURLToPath(import.meta.url));
  * On failure, clean up the stale socket so ensureDaemon can spawn a fresh one.
  */
 export const isDaemonRunning = async (timeoutMs = 2_000): Promise<boolean> => {
-  // If the socket file doesn't exist, the daemon definitely isn't running.
-  try {
-    await access(DAEMON_SOCKET_PATH);
-  } catch {
-    return false;
+  // On POSIX, a missing socket file means the daemon definitely isn't running,
+  // so we can short-circuit. Windows named pipes are not filesystem entries —
+  // access() always fails there — so skip the pre-check and probe directly.
+  if (!isWindows) {
+    try {
+      await access(DAEMON_SOCKET_PATH);
+    } catch {
+      return false;
+    }
   }
 
   return new Promise((resolve) => {
@@ -45,7 +62,7 @@ export const isDaemonRunning = async (timeoutMs = 2_000): Promise<boolean> => {
     const timer = setTimeout(() => {
       sock.destroy();
       // ponytail: stale socket cleanup; ENOENT = already gone, fine
-      unlink(DAEMON_SOCKET_PATH).catch(() => {});
+      cleanupStaleSocket();
       done(false);
     }, timeoutMs);
 
@@ -70,7 +87,7 @@ export const isDaemonRunning = async (timeoutMs = 2_000): Promise<boolean> => {
       clearTimeout(timer);
       sock.destroy();
       // ponytail: connection refused = daemon dead, clean up stale socket
-      unlink(DAEMON_SOCKET_PATH).catch(() => {});
+      cleanupStaleSocket();
       done(false);
     });
 
@@ -96,18 +113,34 @@ export const isDaemonRunning = async (timeoutMs = 2_000): Promise<boolean> => {
 export const spawnDaemon = (): ChildProcess | null => {
   // Resolve the daemon entry point and tsx binary.
   const daemonScript = join(moduleDir, "index.ts");
-  const tsxBin = join(moduleDir, "..", "..", "node_modules", ".bin", "tsx");
 
-  // Use tsx to run the daemon TypeScript source directly.
-  // The spawed process inherits the parent's env so module resolution works.
+  // On Windows, npm installs binaries as `.cmd` shims, not bare executables,
+  // and the npx fallback is `npx.cmd`. A `.cmd` file can only be launched
+  // through a shell (spawning it directly yields EINVAL), so set shell: true
+  // whenever we invoke one.
+  const tsxBinBase = join(moduleDir, "..", "..", "node_modules", ".bin", "tsx");
+  const tsxBin = isWindows ? `${tsxBinBase}.cmd` : tsxBinBase;
+  const hasLocalTsx = existsSync(tsxBin);
+
+  // Use the local tsx binary to run the daemon TypeScript source directly.
+  // The spawned process inherits the parent's env so module resolution works.
   // Fall back to `npx tsx` if the local binary isn't available.
-  const cmd = existsSync(tsxBin) ? tsxBin : "npx";
-  const args = existsSync(tsxBin) ? [daemonScript] : ["tsx", daemonScript];
+  const cmd = hasLocalTsx ? tsxBin : isWindows ? "npx.cmd" : "npx";
+  const args = hasLocalTsx ? [daemonScript] : ["tsx", daemonScript];
+
+  // With shell: true, Node passes the command line to the shell verbatim
+  // without quoting, so any path containing spaces (e.g. C:\Users\Some Name)
+  // would be split into multiple tokens. Wrap each token in double quotes on
+  // Windows to keep space-containing paths intact.
+  const quote = (s: string): string => (isWindows ? `"${s}"` : s);
 
-  const child = spawn(cmd, args, {
+  const child = spawn(quote(cmd), args.map(quote), {
     detached: true,
     stdio: "ignore",
     env: { ...process.env },
+    // `.cmd` shims (local tsx or npx.cmd on Windows) must run via a shell.
+    shell: isWindows,
+    windowsVerbatimArguments: isWindows,
   });
 
   child.unref();
diff --git a/src/setup.ts b/src/setup.ts
index 561a343..1ff7c36 100644
--- a/src/setup.ts
+++ b/src/setup.ts
@@ -8,6 +8,7 @@ import type { ExtensionAPI } from "@mariozechner/pi-coding-agent";
 import { execSync } from "node:child_process";
 import type { BrowserClient } from "./client";
 import { ensureDaemon } from "./daemon/spawn";
+import { DAEMON_SOCKET_PATH } from "./daemon/protocol";
 
 // ── Public: register the /browser-setup slash command ──────────────────────
 
@@ -41,7 +42,7 @@ export async function performSetup(client: BrowserClient): Promise<SetupResult>
   // Step 2: Start the browser daemon (spawns if not running, silently reuses if alive)
   const daemonReady = await ensureDaemon();
   if (!daemonReady) {
-    return { success: false, error: "Could not start the browser daemon. Check /tmp/pi-browser-daemon.sock." };
+    return { success: false, error: `Could not start the browser daemon. Check ${DAEMON_SOCKET_PATH}.` };
   }
 
   // Step 3: Connect to Chrome DevTools