tiletopia/scripts/mcpb-wrapper.mjs

#!/usr/bin/env node
// tiletopia .mcpb wrapper — entry_point for the bundled MCP server.
//
// What this is: a thin stdio shim Claude Desktop launches when the user
// installs `tiletopia.mcpb`. It reads the per-install MCP server settings
// (port + bearer token) that the running tiletopia app persisted to
// %APPDATA%\com.megaproxy.tiletopia\mcp.json, then execs `npx -y mcp-remote`
// with the right URL + Authorization header. Claude talks stdio to us; we
// proxy through mcp-remote, which talks HTTP to the tiletopia process.
//
// Why a wrapper (not just static args in the manifest):
//   - The bearer token is per-install — generated at first server start, also
//     rotated whenever the user clicks "Regenerate" in the MCP panel. We
//     can't bake it into the bundle (that'd be wrong for every other user)
//     and we don't want to make the user paste it into a user_config prompt
//     at install time. Reading it from %APPDATA% at launch makes the whole
//     thing zero-config and survives token rotation transparently.
//   - The port may also drift (if the saved port is taken, tiletopia falls
//     back to an OS-picked one and re-persists). Reading at launch keeps us
//     correct across that too.
//
// Failure modes & messages: every error we emit goes to stderr so the user
// sees it in Claude Desktop's extension log. We deliberately do NOT swallow
// or transform mcp-remote's own output beyond piping it.

import { spawn } from "node:child_process";
import { readFileSync, existsSync } from "node:fs";
import { join } from "node:path";

const APPDATA = process.env.APPDATA;
if (!APPDATA) {
  console.error(
    "[tiletopia-mcpb] %APPDATA% is unset — this bundle only runs on Windows.",
  );
  process.exit(2);
}

const CFG_PATH = join(APPDATA, "com.megaproxy.tiletopia", "mcp.json");
if (!existsSync(CFG_PATH)) {
  console.error(
    `[tiletopia-mcpb] config not found at ${CFG_PATH}. ` +
      "Launch tiletopia, open the 🤖 MCP panel, and click Server: ON at least " +
      "once so the port + token get persisted, then retry.",
  );
  process.exit(3);
}

let cfg;
try {
  cfg = JSON.parse(readFileSync(CFG_PATH, "utf8"));
} catch (e) {
  console.error(`[tiletopia-mcpb] failed to read/parse ${CFG_PATH}: ${e.message}`);
  process.exit(4);
}

const port = Number(cfg.port);
const token = String(cfg.token ?? "");
if (!Number.isInteger(port) || port <= 0 || port > 65535 || !token) {
  console.error(
    `[tiletopia-mcpb] ${CFG_PATH} is missing a valid port or token. ` +
      "Toggle the MCP server off and on in the tiletopia panel to regenerate it.",
  );
  process.exit(5);
}

const url = `http://127.0.0.1:${port}/mcp`;

// `npx.cmd` on Windows is the actual launcher; bare `npx` is a shim that
// node spawns from PATH and that's also fine. spawn() with shell:true ensures
// PATHEXT resolution picks up the .cmd correctly.
const child = spawn(
  "npx",
  [
    "-y",
    "mcp-remote",
    url,
    "--allow-http",
    "--header",
    `Authorization: Bearer ${token}`,
  ],
  {
    stdio: "inherit",
    shell: true,
  },
);

child.on("error", (e) => {
  console.error(
    `[tiletopia-mcpb] failed to spawn npx: ${e.message}. ` +
      "Make sure Node.js 18+ is installed and `npx` is on PATH.",
  );
  process.exit(6);
});

child.on("exit", (code, signal) => {
  if (signal) process.kill(process.pid, signal);
  else process.exit(code ?? 0);
});

// Forward terminate signals to the child so Claude Desktop's "disable
// extension" cleans up the mcp-remote subprocess.
for (const sig of ["SIGINT", "SIGTERM", "SIGHUP"]) {
  process.on(sig, () => {
    try {
      child.kill(sig);
    } catch {
      /* child may already be gone */
    }
  });
}