feat(mcp-bridge): migrate Node.js stdio bridge to Deno

Replaces all Node.js-specific APIs with native Deno equivalents:
- process.env.* → Deno.env.get()
- process.stdin event loop → for-await async iteration
- process.stdout.write → Deno.stdout.writeSync (encoder)
- process.stderr.write → Deno.stderr.writeSync (encoder)
- process.exit → Deno.exit
- process.pid → Deno.pid
- Node shebang → Deno shebang on main.js + generate-offline-menu.js
- Adds deno.json with tasks and nodeModulesDir: none
- Nickel temp file moved to /tmp with absolute import path
- probeNickel() now catches PermissionDenied gracefully

node:child_process, node:fs, node:path, node:url imports retained
(Deno's Node compat layer handles them without change).

deno check: zero warnings.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: hyperpolymath

mcp-bridge/deno.json

@@ -0,0 +1,11 @@
+// SPDX-License-Identifier: MPL-2.0
+// Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
+//
+// Deno configuration for the BoJ MCP stdio bridge.
+{
+  "tasks": {
+    "start": "deno run --allow-net --allow-env --allow-read main.js",
+    "gen-menu": "deno run --allow-read lib/generate-offline-menu.js"
+  },
+  "nodeModulesDir": "none"
+}

mcp-bridge/lib/api-clients.js

@@ -10,9 +10,9 @@ import { isValidCartridgeName } from "./security.js";
 import { warn } from "./logger.js";
 import { SERVER_VERSION } from "./version.js";
 
-const BOJ_BASE = process.env.BOJ_URL || "http://localhost:7700";
-const GITHUB_TOKEN = process.env.GITHUB_TOKEN || "";
-const GITLAB_TOKEN = process.env.GITLAB_TOKEN || "";
+const BOJ_BASE = Deno.env.get("BOJ_URL") ?? "http://localhost:7700";
+const GITHUB_TOKEN = Deno.env.get("GITHUB_TOKEN") ?? "";
+const GITLAB_TOKEN = Deno.env.get("GITLAB_TOKEN") ?? "";
 
 // ===================================================================
 // BoJ REST API wrappers
@@ -253,7 +253,7 @@ async function gitlabApiCall(method, path, body) {
   if (!GITLAB_TOKEN) {
     return { error: "GITLAB_TOKEN not set." };
   }
-  const baseUrl = process.env.GITLAB_URL || "https://gitlab.com";
+  const baseUrl = Deno.env.get("GITLAB_URL") ?? "https://gitlab.com";
   try {
     const url = `${baseUrl}/api/v4${path}`;
     const opts = {

mcp-bridge/lib/generate-offline-menu.js

@@ -1,4 +1,4 @@
-#!/usr/bin/env node
+#!/usr/bin/env -S deno run --allow-read
 // SPDX-License-Identifier: MPL-2.0
 // Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
 //
@@ -30,5 +30,5 @@ try {
   console.log("\nUpdate mcp-bridge/lib/offline-menu.js with any new cartridges.");
 } catch (err) {
   console.error(`Error scanning cartridges directory: ${err.message}`);
-  process.exit(1);
+  Deno.exit(1);
 }

mcp-bridge/lib/logger.js

@@ -7,7 +7,8 @@
 // MCP JSON-RPC messages). Log level controlled via BOJ_LOG_LEVEL env.
 
 const LOG_LEVELS = { debug: 0, info: 1, warn: 2, error: 3, silent: 4 };
-let currentLevel = LOG_LEVELS[process.env.BOJ_LOG_LEVEL || "info"] ?? LOG_LEVELS.info;
+const _enc = new TextEncoder();
+let currentLevel = LOG_LEVELS[Deno.env.get("BOJ_LOG_LEVEL") ?? "info"] ?? LOG_LEVELS.info;
 
 /**
  * Update the minimum log level at runtime. Used by the MCP
@@ -38,7 +39,7 @@ function log(level, message, fields = {}) {
     msg: message,
     ...fields,
   };
-  process.stderr.write(JSON.stringify(entry) + "\n");
+  Deno.stderr.writeSync(_enc.encode(JSON.stringify(entry) + "\n"));
 }
 
 /** @param {string} msg @param {Record<string, unknown>} [fields] */

mcp-bridge/lib/nickel-validator.js

@@ -59,10 +59,15 @@ export function contractsPath() {
 /** Probe whether `nickel` is on PATH. Cached. */
 function probeNickel() {
   if (nickelAvailable !== null) return nickelAvailable;
-  const r = spawnSync("nickel", ["--version"], { stdio: "ignore" });
-  nickelAvailable = r.status === 0;
+  try {
+    const r = spawnSync("nickel", ["--version"], { stdio: "ignore" });
+    nickelAvailable = r.status === 0;
+  } catch {
+    // PermissionDenied (no --allow-run) or binary not found — treat as absent.
+    nickelAvailable = false;
+  }
   if (!nickelAvailable) {
-    const strict = process.env.COORD_REQUIRE_NICKEL === "1";
+    const strict = Deno.env.get("COORD_REQUIRE_NICKEL") === "1";
     if (strict) {
       throw new Error("COORD_REQUIRE_NICKEL=1 but `nickel` not on PATH");
     }
@@ -124,17 +129,17 @@ export function validateEnvelope(envelope, senderRole) {
   }
 
   // Write the call-site script to a temp file in the same dir as the
-  // contracts so its relative `import` resolves.
-  const tmp = resolve(dirname(path), `._validate_${process.pid}_${Date.now()}.ncl`);
+  // contracts so its relative `import` resolves. /tmp is writable and
+  // isolated enough; we use an absolute import path so location doesn't matter.
+  const tmp = resolve("/tmp", `._boj_validate_${Deno.pid}_${Date.now()}.ncl`);
   const script =
-    `let c = import "${path.split("/").pop()}" in\n` +
+    `let c = import "${path}" in\n` +
     `let e = ${toNickel(withMeta)} in\n` +
     `c.validate e\n`;
 
   try {
     writeFileSync(tmp, script);
     const r = spawnSync("nickel", ["eval", tmp], {
-      cwd: dirname(path),
       encoding: "utf8",
     });
     if (r.status === 0) return { ok: true };

mcp-bridge/lib/security.js

@@ -133,7 +133,7 @@ function scanObjectForInjection(obj, maxDepth = 10) {
 // Rate limiter (token bucket)
 // ===================================================================
 
-const RATE_LIMIT = parseInt(process.env.BOJ_RATE_LIMIT, 10) || 60;
+const RATE_LIMIT = parseInt(Deno.env.get("BOJ_RATE_LIMIT") ?? "60", 10) || 60;
 const RATE_WINDOW_MS = 60_000;
 
 const rateBucket = {

mcp-bridge/main.js

@@ -1,4 +1,4 @@
-#!/usr/bin/env node
+#!/usr/bin/env -S deno run --allow-net --allow-env --allow-read
 // SPDX-License-Identifier: MPL-2.0
 // Copyright (c) 2026 Jonathan D.A. Jewell (hyperpolymath) <j.d.a.jewell@open.ac.uk>
 //
@@ -8,8 +8,7 @@
 // stdio protocol so that Claude Code, Glama, and other MCP clients
 // can discover and invoke BoJ cartridge tools.
 //
-// Usage: deno run --allow-net main.js
-//    or: node main.js
+// Usage: deno run --allow-net --allow-env --allow-read main.js
 
 import {
   RATE_LIMIT,
@@ -37,45 +36,24 @@ import {
 } from "./lib/nickel-validator.js";
 import { info, warn, error as logError, setLevel as setLogLevel } from "./lib/logger.js";
 
-const BOJ_BASE = process.env.BOJ_URL || "http://localhost:7700";
+const BOJ_BASE = Deno.env.get("BOJ_URL") ?? "http://localhost:7700";
 const SERVER_NAME = "boj-server";
 const SERVER_VERSION = "0.4.0";
 
 // ===================================================================
 // JSON-RPC stdio transport
 // ===================================================================
 
+const encoder = new TextEncoder();
+const decoder = new TextDecoder();
+
 let buffer = "";
 const MAX_BUFFER_BYTES = 2 * 1_048_576; // 2 MB
 
-process.stdin.setEncoding("utf8");
 const pendingMessages = [];
 
-process.stdin.on("data", (chunk) => {
-  buffer += chunk;
-  if (buffer.length > MAX_BUFFER_BYTES) {
-    sendError(null, -32600, "Message too large");
-    buffer = "";
-    return;
-  }
-  let boundary;
-  while ((boundary = buffer.indexOf("\n")) !== -1) {
-    const line = buffer.slice(0, boundary).trim();
-    buffer = buffer.slice(boundary + 1);
-    if (line.length > 0) {
-      const p = handleMessage(line).catch(() => {});
-      pendingMessages.push(p);
-    }
-  }
-});
-
-process.stdin.on("end", async () => {
-  await Promise.allSettled(pendingMessages);
-  process.exit(0);
-});
-
 function send(obj) {
-  process.stdout.write(JSON.stringify(obj) + "\n");
+  Deno.stdout.writeSync(encoder.encode(JSON.stringify(obj) + "\n"));
 }
 
 function sendResult(id, result) {
@@ -268,7 +246,7 @@ async function dispatchTool(toolName, args) {
 // local-coord-mcp direct dispatch (loopback only, port 7745)
 // ===================================================================
 
-const LOCAL_COORD_URL = process.env.COORD_BACKEND_URL || "http://127.0.0.1:7745";
+const LOCAL_COORD_URL = Deno.env.get("COORD_BACKEND_URL") ?? "http://127.0.0.1:7745";
 
 // Nickel contracts run on coord_send / coord_send_gated only — those
 // are the two tools whose `message` argument carries an A2ML envelope.
@@ -477,3 +455,28 @@ async function handleMessage(line) {
       }
   }
 }
+
+// ===================================================================
+// Main I/O loop — async-iterable stdin (Deno)
+// ===================================================================
+
+for await (const chunk of Deno.stdin.readable) {
+  buffer += decoder.decode(chunk);
+  if (buffer.length > MAX_BUFFER_BYTES) {
+    sendError(null, -32600, "Message too large");
+    buffer = "";
+    continue;
+  }
+  let boundary;
+  while ((boundary = buffer.indexOf("\n")) !== -1) {
+    const line = buffer.slice(0, boundary).trim();
+    buffer = buffer.slice(boundary + 1);
+    if (line.length > 0) {
+      const p = handleMessage(line).catch(() => {});
+      pendingMessages.push(p);
+    }
+  }
+}
+
+await Promise.allSettled(pendingMessages);
+Deno.exit(0);