wrangler >=4.124.0 changed what `--latest` does. It uses the latest compatibility date supported by this version of Wrangler. Silent: code written for older versions still runs, without an error.

const { spawnSync } = require("child_process");
const fs = require("fs");
const path = require("path");
const dir = "/w/proj";
fs.rmSync(dir, { recursive: true, force: true });
fs.mkdirSync(dir, { recursive: true });
const home = fs.mkdtempSync("/tmp/home-");
function wrangler(args, extraEnv, dropEnv) {
  const env = Object.assign({}, process.env, { CI: "1", WRANGLER_SEND_METRICS: "false", NO_COLOR: "1", FORCE_COLOR: "0", HOME: home }, extraEnv || {});
  for (const k of dropEnv || []) delete env[k];
  const r = spawnSync(process.execPath, ["--no-warnings", "/w/node_modules/wrangler/wrangler-dist/cli.js", ...args], { cwd: dir, encoding: "utf8", timeout: 40000, env });
  const out = (String(r.stdout || "") + String(r.stderr || "")).replace(/\x1b\[[0-9;]*m/g, "");
  return { status: r.status, out };
}
function symptom(msg) { console.error("FAIL: " + msg); process.exit(1); }
function broken(msg, out) {
  console.error("ERROR: " + msg);
  if (out) console.error(out.slice(-2000));
  process.exit(2);
}
function write(name, content) {
  fs.writeFileSync(path.join(dir, name), typeof content === "string" ? content : JSON.stringify(content, null, 2));
}
write("index.js", 'export default { fetch() { return new Response("ok"); } };\n');
write("wrangler.json", { name: "latest-date", main: "index.js" });
const wv = JSON.parse(fs.readFileSync(require.resolve("workerd/package.json", { paths: ["/w/node_modules/wrangler"] }), "utf8")).version;
const m = /^1\.(\d{4})(\d{2})(\d{2})\./.exec(wv);
if (!m) broken("unexpected workerd version " + wv);
const expected = m[1] + "-" + m[2] + "-" + m[3];
const r = wrangler(["deploy", "--dry-run", "--outdir", "out", "--latest"]);
if (r.out.includes("Using the latest version of the Workers runtime.")) symptom("--latest still means the newest Workers runtime, not the bundled workerd release date");
if (r.status !== 0 || !r.out.includes("latest compatibility date supported by this version of Wrangler (" + expected + ")")) broken("unexpected output; expected the workerd release date " + expected, r.out);
console.log("OK: --latest resolved to " + expected);

const { spawnSync } = require("child_process");
const fs = require("fs");
const path = require("path");
const dir = "/w/proj";
fs.rmSync(dir, { recursive: true, force: true });
fs.mkdirSync(dir, { recursive: true });
const home = fs.mkdtempSync("/tmp/home-");
function wrangler(args, extraEnv, dropEnv) {
  const env = Object.assign({}, process.env, { CI: "1", WRANGLER_SEND_METRICS: "false", NO_COLOR: "1", FORCE_COLOR: "0", HOME: home }, extraEnv || {});
  for (const k of dropEnv || []) delete env[k];
  const r = spawnSync(process.execPath, ["--no-warnings", "/w/node_modules/wrangler/wrangler-dist/cli.js", ...args], { cwd: dir, encoding: "utf8", timeout: 40000, env });
  const out = (String(r.stdout || "") + String(r.stderr || "")).replace(/\x1b\[[0-9;]*m/g, "");
  return { status: r.status, out };
}
function symptom(msg) { console.error("FAIL: " + msg); process.exit(1); }
function broken(msg, out) {
  console.error("ERROR: " + msg);
  if (out) console.error(out.slice(-2000));
  process.exit(2);
}
function write(name, content) {
  fs.writeFileSync(path.join(dir, name), typeof content === "string" ? content : JSON.stringify(content, null, 2));
}
write("index.js", 'export default { fetch() { return new Response("ok"); } };\n');
write("wrangler.json", { name: "latest-date", main: "index.js" });
const wv = JSON.parse(fs.readFileSync(require.resolve("workerd/package.json", { paths: ["/w/node_modules/wrangler"] }), "utf8")).version;
const m = /^1\.(\d{4})(\d{2})(\d{2})\./.exec(wv);
if (!m) broken("unexpected workerd version " + wv);
const expected = m[1] + "-" + m[2] + "-" + m[3];
const r = wrangler(["deploy", "--dry-run", "--outdir", "out", "--latest"]);
if (r.out.includes("Using the latest version of the Workers runtime.")) symptom("--latest still means the newest Workers runtime, not the bundled workerd release date");
if (r.status !== 0 || !r.out.includes("latest compatibility date supported by this version of Wrangler (" + expected + ")")) broken("unexpected output; expected the workerd release date " + expected, r.out);
console.log("OK: --latest resolved to " + expected);