It has been about a week since Tesla owners started receiving the FSD (Supervised) v12.4.3 update to their cars. However, after a few days of testing, Tesla owners found out that this version also has issues carried forward from the previous FSD V12 updates.
One of these complaints was from one of the beta testers from Omar (@Whole Mars Catalog / X) who belongs to the original early-access Tesla owners group and is also a retail investor in Tesla (TSLA).
“FSD 12.4.3 still ping-ponging within the lane too much on highways,” he reported on X (Twitter). To which Tesla CEO Elon Musk responded “12.5.x will finally combine the city and highway software stacks”.
Earlier in May, Elon Musk gave a tentative end-of-June timeline for the release of FSD v12.5. However, it has already been late. “12.5 will be out in late June. Will also see a major improvement in mpi and is single stack – no more implicit stack on highways,” Musk posted on X (formerly Twitter) [mpi = miles per intervention].
In this same discussion thread on X, Elon Musk also confirmed that the Tesla Cybertruck will start getting the Full Self-Driving (FSD) updates with FSD v12.5. Currently, Cybertrucks doesn’t have the option to download and install FSD (Supervised) updates (previously called FSD Beta).
Single Stack for Highways and City Streets
The term “single stack” for Autopilot/FSD is a bit confusing for the general public and even the majority of Tesla owners who don’t have a background in software or technology. Let’s understand this phenomenon from what I have learned from almost 9 years of covering Tesla Autopilot development.
There have been several iterations of the Tesla Autopilot software. The 1st version used the Mobileye software to run its cars around 9-10 years ago. However, down the road, Tesla developed its own Autopilot software and introduced Hardware 1 in cars and later on introduced Hardware 2.0 (explained in Elon Musk’s Autopilot 2.0 conference call from 2016).
In the initial years, Tesla software engineers tried to solve self-driving with hand-written code. During these years, Tesla focused on solving autonomy for highway driving (relatively easier). Autopilot performed better on highways with human supervision. This created a stack of software that was specific to highways.
Simultaneously, Tesla was working on solving autonomous driving on city streets. But this stack of Autopilot software was mostly not released to the public until the early FSD Beta builds started rolling out.
Constant releases of new software versions and hardware upgrades in new vehicles created multiple stacks of Autopilot software. Tesla had to keep some legacy code stacks while they worked on future releases.
In 2021, Tesla started migrating towards Tesla Vision as Andrej Karpathy led the company’s AI efforts for developing the next phase of Full Self-Driving (FSD) technology.
It wasn’t until November 2022 with the release of FSD Beta V11, that the automaker replaced the legacy code stack with the unified (single) stack for highways only. However, Tesla did not merge the stacks of city street navigation and highways for an even more unified stack.
The city streets stack was separately trained AI vision (end-to-end based on neural networks). When Tesla CEO Elon Musk demonstrated FSD v12 on his personal Tesla Model S last year, he said that 300K+ lines of C++ code was removed to convert the city streets stack to a full end-to-end neural network-based Autopilot navigation. Later on, this statement became part of the official release notes of FSD v12 and all of its subversions.
FSD (Supervised) v12 upgrades the city-streets driving stack to a single end-to-end neural network trained on millions of video clips, replacing over 300K lines of explicit C++ code.
Tesla FSD v12 Release Notes
Finally, with FSD v12.5, Tesla will merge the Autopilot software stacks for both city streets and highways. The impact of the new single stack will lower the development timeline for the Tesla AI software development team. This will result in faster version deployments, bug fixing, and a seamless single-version release across the fleet.
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