Tesla AI: FSD Supervised v14.3.9 starts rollout

Tesla AI posted that FSD Supervised v14.3.9 is starting to roll out shortly. In the same Tesla AI note, the account described a new active safety feature set. The first clause is firm: "FSD Supervised can now activate on your behalf when an imminent collision is detected and Automatic Emergency Braking (AEB) may not be enough."

The second clause stays in Tesla AI's weaker verb. The post says FSD Supervised may also engage if Tesla detects the driver is heavily distracted, or has accidentally disengaged FSD. Those are two different paths. The collision line is about a crash already forming when AEB might not cover it. The lapse line is about heavy distraction, or an accidental FSD drop, with the stack coming back on. "Accidentally disengaged FSD" only makes sense if FSD was already on.

Tesla AI kept the product name FSD Supervised on both clauses. The post does not name a car firmware id, a hardware class, or a region. It also does not say whether "activate on your behalf" is a full FSD session, a short intervention, or a handoff back to the driver after the event. Those sit open until in-car notes or a later Tesla or Tesla AI post fill them in.

v14.3.9 is a named point release on the v14.3 line. Tesla AI did not attach it to a 2026.x vehicle software build in this note. Independent update trackers still listed v14.3.8 on 2026.26.6.5 as of this morning.

Open questions stay practical. Is accidental disengage a steering-torque bump, a stalk, or a UI cancel? Will the AEB-plus path and the lapse path ship on the same cars? Does the same logic show up on AI3/HW3 Lite builds, or only the AI4 v14.3 line? Tesla AI did not say.

The AEB path is the harder product change if it behaves as posted. Automatic Emergency Braking is already on Tesla cars as a last-moment brake. Tesla AI is saying FSD Supervised can come on for the driver when a collision is already imminent and AEB may not be enough. Crash-avoidance rates for this build are still missing. The distraction and accidental-disengage line is softer: "may also engage," with no definition of heavy distraction and no list of what counts as accidental disengage.

Tesla AI did not say the new engage path requires a separate purchase, or that it is on by default for cars that never enabled FSD. There was no Vehicle Safety Report update and no Elon amplify attached to the note. Until in-car notes land, the only primary text is that one September 4 post.

Confirmed

• Tesla AI (Sept 4): FSD Supervised v14.3.9 "starting to roll out shortly"
• Same post: new active safety feature set; FSD Supervised can now activate on your behalf when an imminent collision is detected and AEB may not be enough
• Same post: it may also engage if Tesla detects the driver is heavily distracted or has accidentally disengaged FSD

Not confirmed

• Car firmware id (2026.x) and hardware class for v14.3.9
• Region, Fast Updates vs wide, or subscription gating for the new engage path
• Whether "activate on your behalf" is a full FSD session, a short intervention, or a later handoff
• Independent install counts or crash-avoidance rates for this build

What to watch: in-car release notes once cars pull the build; whether Tesla AI or Tesla posts a firmware number; early owner clips that show the AEB-plus or re-engage cases.