wrangler >=4.113.0 changed what `wrangler dev` does. wrangler dev started in a headless AI agent environment now prints the Local Explorer API URL and basic resource routes. Silent: code written for older versions still runs, without an error.

const fs = require("fs");
const path = require("path");
const { spawn } = require("child_process");
function symptom(msg) { console.error("FAIL: " + msg); process.exit(1); }
function broken(msg) { console.error("ERROR: " + msg); process.exit(2); }
const dir = fs.mkdtempSync("/tmp/proj-");
fs.writeFileSync(path.join(dir, "wrangler.json"), JSON.stringify({ name: "agent-hint", main: "index.js", compatibility_date: "2024-01-01" }));
fs.writeFileSync(path.join(dir, "index.js"), 'export default { fetch() { return new Response("hello-from-worker"); } };');
const env = Object.assign({}, process.env, { CLAUDECODE: "1", WRANGLER_SEND_METRICS: "false", NO_COLOR: "1", FORCE_COLOR: "0" });
const child = spawn(process.execPath, ["/w/node_modules/wrangler/bin/wrangler.js", "dev", "--ip", "127.0.0.1", "--port", "8787"], { cwd: dir, env, stdio: ["ignore", "pipe", "pipe"] });
let out = "";
let done = false;
let readyAt = 0;
const clean = () => out.replace(/\x1b\[[0-9;]*m/g, "");
child.stdout.on("data", (d) => { out += d; });
child.stderr.on("data", (d) => { out += d; });
child.on("exit", (code) => { if (!done) { done = true; broken("wrangler dev exited early with code " + code + ": " + clean().slice(-2000)); } });
function finish(fn) { if (done) return; done = true; clearInterval(timer); child.kill("SIGKILL"); fn(); }
const start = Date.now();
let probing = false;
const timer = setInterval(async () => {
  if (done) return;
  if (!readyAt && !probing) {
    probing = true;
    try {
      const res = await fetch("http://127.0.0.1:8787/");
      if ((await res.text()) === "hello-from-worker") readyAt = Date.now();
    } catch {}
    probing = false;
  }
  const text = clean();
  const hint = text.match(/The Local Explorer API is available at (http:\/\/\S+\/cdn-cgi\/explorer\/api)/);
  if (hint && text.includes("GET " + hint[1] + "/local/workers")) {
    finish(() => { console.log("OK: wrangler dev printed: " + hint[0]); process.exit(0); });
  } else if (readyAt && Date.now() - readyAt > 5000) {
    finish(() => symptom("wrangler dev run by an AI agent without a TTY did not print the Local Explorer API URL"));
  } else if (Date.now() - start > 75000) {
    finish(() => broken("wrangler dev did not serve the worker in time: " + text.slice(-2000)));
  }
}, 250);

const fs = require("fs");
const path = require("path");
const { spawn } = require("child_process");
function symptom(msg) { console.error("FAIL: " + msg); process.exit(1); }
function broken(msg) { console.error("ERROR: " + msg); process.exit(2); }
const dir = fs.mkdtempSync("/tmp/proj-");
fs.writeFileSync(path.join(dir, "wrangler.json"), JSON.stringify({ name: "agent-hint", main: "index.js", compatibility_date: "2024-01-01" }));
fs.writeFileSync(path.join(dir, "index.js"), 'export default { fetch() { return new Response("hello-from-worker"); } };');
const env = Object.assign({}, process.env, { CLAUDECODE: "1", WRANGLER_SEND_METRICS: "false", NO_COLOR: "1", FORCE_COLOR: "0" });
const child = spawn(process.execPath, ["/w/node_modules/wrangler/bin/wrangler.js", "dev", "--ip", "127.0.0.1", "--port", "8787"], { cwd: dir, env, stdio: ["ignore", "pipe", "pipe"] });
let out = "";
let done = false;
let readyAt = 0;
const clean = () => out.replace(/\x1b\[[0-9;]*m/g, "");
child.stdout.on("data", (d) => { out += d; });
child.stderr.on("data", (d) => { out += d; });
child.on("exit", (code) => { if (!done) { done = true; broken("wrangler dev exited early with code " + code + ": " + clean().slice(-2000)); } });
function finish(fn) { if (done) return; done = true; clearInterval(timer); child.kill("SIGKILL"); fn(); }
const start = Date.now();
let probing = false;
const timer = setInterval(async () => {
  if (done) return;
  if (!readyAt && !probing) {
    probing = true;
    try {
      const res = await fetch("http://127.0.0.1:8787/");
      if ((await res.text()) === "hello-from-worker") readyAt = Date.now();
    } catch {}
    probing = false;
  }
  const text = clean();
  const hint = text.match(/The Local Explorer API is available at (http:\/\/\S+\/cdn-cgi\/explorer\/api)/);
  if (hint && text.includes("GET " + hint[1] + "/local/workers")) {
    finish(() => { console.log("OK: wrangler dev printed: " + hint[0]); process.exit(0); });
  } else if (readyAt && Date.now() - readyAt > 5000) {
    finish(() => symptom("wrangler dev run by an AI agent without a TTY did not print the Local Explorer API URL"));
  } else if (Date.now() - start > 75000) {
    finish(() => broken("wrangler dev did not serve the worker in time: " + text.slice(-2000)));
  }
}, 250);