Rivian Chief Software Officer Wassym Bensaid posted a 25-letter string on X on Tuesday that rearranges into “Halloween Mode October Ninth”, about two hours after Tesla began rolling out its own Halloween software update.
The post consisted only of the letters “abcdeeeehhillmnnnoooorttw”, arranged in alphabetical order, with no other text, image or link.
Neither Bensaid nor Rivian has confirmed what the message means.
The reading was put forward in replies on X, and the letters match exactly, with none left over and none missing.
Earlier Than Any Previous Year
Rivian has shipped four Halloween editions, and this year’s will be the fifth.
The earliest so far was October 18, in 2024, and the feature became available on October 21 in both 2023 and 2025.
Bensaid had signalled an earlier start, writing on September 14 that “Halloween will be epic this year… and early”.
Rivian’s own account followed on October 1.
“You didn’t think we’d ghost you, right? Spooky update coming soon,” the company wrote on X.
Rivian has also listed limited-edition merchandise on its online store showing its Gear Guard mascot dressed as a ghost.
The company has not announced a theme, a software version or which vehicles will be covered.
Tesla Moved First
Tesla announced its update at 2:22 p.m. Eastern time on Tuesday.
“Halloween Mode now rolling out,” the company wrote on X, describing an update that “turns your Tesla into a haunted house on wheels”.
Features listed in the post include a ghost costume for the car’s on-screen avatar, a “Trick or Treat” setting that plays sounds and flickers the lights when visitors approach, and a new light show, wraps and lock sound.
It is being delivered with software version 2026.38.3.
Tesla’s release notes invite owners to “spread holiday fear year round”, which indicates the mode will remain available after October.
Bensaid’s post appeared two hours later, at 4:30 p.m. Eastern time.
What Rivian Has Done Before
Rivian’s Halloween features have been temporary, appearing for a fixed period and then being withdrawn.
Last year’s version, called Spooky Swamp, ran from October 21 to November 1 and was delivered in software version 2025.38.
It gave R1S and R1T vehicles with the newer hardware four exterior light and sound routines, along with swamp-themed animations on the cabin screens and themed music.
Older R1 vehicles received one exterior lighting option.
Owners switched it on through a card in the Rivian mobile app, and a motion setting could trigger the effects when someone approached the parked vehicle.
The 2024 edition introduced what Rivian called “car costumes”, including licensed themes based on Knight Rider and Back to the Future.
In 2023 the update turned the cabin accent lights green, replaced the lock sound with organ music and showed cyclists on the driver display as witches on broomsticks.
“The beauty of it, it’s all ephemeral,” Bensaid told Forbes last year. “It’s two weeks and it goes away.”
The New OS
The R1 moved to a redesigned software platform, Rivian OS 2, in an update that began rolling out on September 4, Bensaid said at the time.
Release notes for the R1’s latest update, version 2026.36, were shared by owners on October 3 and make no mention of Halloween.
Bensaid said on October 2 that the Rivian Assistant is coming to the R2 in the next over-the-air update. The release notes were announced earlier on Tuesday.
