If you’re running a Comma 3X in your Rivian R1T or R1S (Gen 1), there’s a new upgrade worth checking out. Developer Lukas Loetkolben, known for his work in the Comma community, has released a Longitudinal Upgrade Kit that unlocks full speed control and blind spot monitoring through Openpilot. It’s now available on his website: xnor.shop.
This harness plugs into your vehicle’s CAN system and allows Openpilot to handle acceleration and braking—taking over from Rivian’s built-in Adaptive Cruise Control (ACC). More importantly, it adds the ability to use your steering wheel buttons and scroll wheel for cruise control, and even feeds blind spot monitoring data into the Comma 3X.
What It Adds
Unlike the standard Comma 3X setup on Rivian, which only supports lateral control (steering), this harness gives Openpilot access to the vehicle’s longitudinal behavior—meaning throttle and brake. Once installed, you can:
- Use the +/- cruise buttons or scroll wheel on the steering wheel to control speed
- Let Openpilot manage acceleration and deceleration directly
- Replace Rivian’s factory ACC with a more responsive, customizable system
- See blind spot alerts integrated into the openpilot UI as well as auto lane change delay integration
The result is a more seamless experience that feels closer to OEM implementations, but with the flexibility and transparency of the openpilot ecosystem.
Installation and Compatibility
The kit is designed to be plug-and-play, with no cutting or permanent vehicle modifications required. It connects to the original Comma or Loetkolben harness and then plugs into the Comma 3X’s secondary USB-C port. It comes in two versions—one for Loetkolben’s custom harness and one that works with the standard Comma harness (an adapter is included in that version).
To run the kit, you’ll need to install a master-dev fork of Sunnypilot, such as sunnypilot/staging-c3-new. This fork adds support for steering wheel button input, scroll wheel integration, and blind spot monitoring display. It’s under active development and built to take advantage of the harness’s full feature set.
Why It Matters
Rivian’s stock cruise system is usable but conservative—acceleration can be sluggish, and deceleration can feel abrupt. With this kit, you get a smoother, more consistent experience driven entirely by Openpilot. The ability to manage cruise control directly from the steering wheel (instead of relying on touchscreen interactions) is a big win for usability. And blind spot monitoring integration adds a safety layer that many openpilot users have been asking for.
This isn’t just about convenience—it’s about trust in the system and minimizing distractions on the road. For anyone relying on openpilot for serious miles, especially in mixed highway and city conditions, this upgrade tightens the connection between driver, hardware, and software.
Pricing
The Rivian Longitudinal Upgrade Kit is available now for €299 or €349, depending on the version. You’ll want to double-check which harness you’re using (Comma vs. Lukas’) before ordering, as the installation and hardware is slightly different.
Link: xnor.shop product page
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