Firebase Functions "cannot determine backend specification"

I started intermittently receiving this error

⬢ functions: Failed to load function definition from source: FirebaseError: User code failed to load. Cannot determine backend specification

when starting the emulator. Reports of this on the internet speculate about a wide range of things but no root cause was known, so I’ve been just restarting constantly until the error doesn’t throw. Now, it’s 100% of the time and my development has screeched to a halt. After hours and hours of switching going down various guess-and-check rabbit holes, I’m at a loss.

firebase-tools version:

$ firebase --version
13.17.0

Here is a minimum reproducible version of functions/index.js:

const admin = require("firebase-admin/app");
admin.initializeApp();

const functions = require("firebase-functions/v1");

exports.created = functions.auth.user().onCreate(async (user) => {
  const email = user.email;
  console.log(email);
  return;
});

And the contents of functions/package.json:

{
  "name": "functions",
  "description": "Cloud Functions for Firebase",
  "scripts": {
    "lint": "eslint .",
    "serve": "firebase emulators:start --only functions",
    "shell": "firebase functions:shell",
    "start": "npm run shell",
    "deploy": "firebase deploy --only functions",
    "logs": "firebase functions:log"
  },
  "engines": {
    "node": "18"
  },
  "main": "index.js",
  "private": true,
  "dependencies": {
    "firebase-admin": "^12.4.0",
    "firebase-functions": "^6.0.1",
    "nodemailer": "^6.9.15"
  }
}

When starting the emulator with the --debug flag, this precedes the error in the log:

Failed to find version of module node: reached end of search path src/functions/node_modules
✔  functions: Using node@18 from host. 
Could not find functions.yaml. Must use http discovery
Found firebase-functions binary at 'src/functions/node_modules/.bin/firebase-functions'
Serving at port 8872

⬢  functions: Failed to load function definition from source: FirebaseError: User code failed to load. Cannot determine backend specification

Update:
After further debugging, it seems that when the emulator starts, it attempts to serve up the functions code via this:

node src/functions/node_modules/.bin/firebase-functions src/functions

My current best current guess is that there is a bug in firebase-tools where it no longer creates a functions.yaml (perhaps an artifact of a past version) or in firebase-functions where node crashes for some reason and thus does not serve the functions code within the 10s timeout expected by firebase-tools.