comma.ai has shrunk its driver-assistance computer to a fifth of the size of the model it replaces and left the price at $999. It is also, since September, the subject of a federal defect investigation. Both things are true at once, and anyone shopping for one needs both.
What the box actually is
The comma 4 mounts on your windscreen and plugs into a wiring harness built for your exact car. It runs openpilot, comma’s open-source driver-assistance software, which takes over adaptive cruise control and lane centering from the factory system on more than 325 supported models. One camera watches the road. Another watches you, and complains when you stop watching the road.
Inside: a Snapdragon 845 MAX, three camera views, 128 GB of storage, USB 3.1 Gen 2 and high-precision GPS — the same compute and sensor suite as the comma 3X, in a body one-fifth the size. openpilot 0.11, released in March, is described by comma as the first assisted-driving system trained inside a neural simulation. A separate add-on called Chestnut, out since August, hangs an external AMD GPU off the device over USB-to-PCIe for anyone who wants more compute than that.
The investigation
On 23 September 2026 the NHTSA Office of Defects Investigation opened file PE26007 into comma.ai’s hands-off driver assistance. It covers five crashes. Two of them killed three people; across four of them as many as eleven people were injured, some seriously. The thread NHTSA names is the system failing to detect or respond to slow or stopped vehicles in the same lane.
One of the fatal crashes happened in February in Ascension Parish, Louisiana. A 2022 Toyota RAV4 struck a stopped first-responder vehicle, and two rear-seat passengers died. That car was running FrogPilot — a third-party fork of openpilot, not comma’s own build.
The distinction cuts both ways. openpilot being open source is precisely why forks exist, and a fork is not the manufacturer’s software. It is also precisely why a buyer cannot assume that the code running on a second-hand device is the code comma shipped.
What comma says itself
comma’s own documentation states that adaptive cruise control performance can be affected by vehicles in the same lane that are not moving — which is the exact failure mode under investigation — and that the driver must be capable of immediately retaking manual control. Neither sentence is buried. Both sit on the website, in plain language, which is more than most of the industry manages when describing what its systems record and what they cannot see.
An opened investigation is not a finding of fault. NHTSA closes plenty of them without one. But it is a published list of crashes with a named common failure, and that is a different kind of document from a marketing spec sheet.
The honest summary
For $999 you get capable lane centering on cars whose factory system is mediocre, from a company that publishes its source code and its limitations. You also get a device whose hardest problem — a stationary object in your lane — is the one currently sitting in a federal file. Buy it as an assistance system you supervise every second. It is the opposite of the gadgets that promise to do the work for you, and it is honest about that. Do not buy it as anything else.