Hermes Agent user builds a Mac app that reads a car's engine live

A Hermes Agent user asked his AI agent to build a Mac app that watches a car while it runs, and the result is now free for anyone to download. The app, called HermesOBD, reads live engine data from a 2005 Ford Mustang through a small Bluetooth plug and passes a running summary to Hermes Agent, which comments on what it sees, according to a post by witcheer, a community member at Nous Research, on the 26th of October 2026.

The car belonged to a neighbour, witcheer wrote. The developer, who publishes as trafalger1801, put the finished app on its public page on GitHub on the 25th of October 2026, as open source, meaning anyone can read, copy and change it.

The post had passed 47,000 views by the 27th of October, according to the counter on X. Teknium, who describes himself on X as cofounder and lead engineer of Hermes Agent at Nous Research, shared it on the 26th of October with a word of praise.

What the app does, in plain words

Cars like the Mustang have a standard repair socket, known as the OBD port, that mechanics plug their testers into. It usually sits under the dashboard on the driver's side, the project's notes say. HermesOBD turns a Mac into that tester.

A small adapter goes into the socket and talks to the Mac over Bluetooth. The one used on the Mustang is an Innova 3210RS, a code reader sold in shops such as Canadian Tire. Once connected, the app does five things, according to the project page:

• Live gauges. Engine speed in turns per minute, road speed, engine water temperature, fuel level, battery voltage and more. The Mustang offered 47 readings, and every one on the dashboard came through.
• Fault codes. It reads the codes behind the orange engine warning light, both the saved ones and the pending ones the car has spotted but not yet confirmed.
• A record of each drive. It can save every reading to a simple spreadsheet file for later.
• A practice mode. A built-in simulator shows made-up numbers, coloured orange and labelled as such, so the app can be tried without a car.
• A link to Hermes Agent. It can send the readings to the user's own agent for comments and questions.

How Hermes Agent rides along

Hermes Agent is an AI assistant made by Nous Research that runs on a machine of the user's choosing and builds up memory and skills over time.

In HermesOBD, every 30 seconds by default, the app sends the agent a short written summary: the latest, lowest, average and highest value of each reading, plus any fault codes. The gap can be set anywhere from 15 seconds to five minutes, the project page says.

Each summary is linked to the ones before it, so the agent can say how the engine is changing over the drive. Reading the fault codes sends an extra summary straight away. The user can also type questions about the numbers inside the app and get answers there.

The summaries leave out the car's serial number, its location and personal details, according to the developer. The link to the agent switches itself off every time the app starts, and the app shows the exact text it sent.

Built to look at the car and leave it alone

A car's computer can also accept commands that change how the engine runs. HermesOBD is built to refuse them. Every command passes through an allowlist, a fixed list of permitted requests, and anything outside it is blocked before it reaches the car, the project page says.

That rules out tuning, which means changing engine settings, and reflashing, which means rewriting the car's software. The developer wrote that reflashing over a cheap wireless plug could leave a car unable to start if the link dropped halfway.

One action that changes something is allowed, under guard: clearing the fault codes. It is off by default and asks the user to switch it on, park, turn the engine off and type the word CLEAR. The app checks again that the car is still and the engine stopped before it sends anything.

The notes also tell drivers to leave the screen to a passenger, or to record the drive and read it afterwards.

Where the project stands

The live readings and the fault codes were checked on the Mustang itself, with the Innova adapter, according to the developer's notes. The Hermes commentary has so far been run on practice data from the simulator.

• Price: free, under the MIT licence, which lets anyone use and change the code.
• Computer: a Mac on macOS 14 or newer.
• Adapters: plugs that speak the common ELM327 standard, the language most cheap car readers use, over Bluetooth or Wi-Fi.
• Interest: 39 GitHub users had starred it, a public bookmark, and 4 had made their own copy by the 27th of October.

An agent that builds what it is asked for

The request in this story was ordinary: a person wanted to see a car's health on a laptop, and asked an agent. The answer was a working app with its own safety rules.

The app also expects the agent to be awake. Its notes say the Hermes service has to be running whenever the commentary is switched on. An agent that takes jobs like this at any hour needs a machine that stays on.

OneClickClaw runs Hermes Agent on a dedicated EU server that stays on around the clock, from €14.99 a month, with a 7-day free trial at oneclickclaw.io.

Sources: witcheer on X, the project page on GitHub, Teknium on X.