Raghu Bharadwaj

Posted on Aug 27 Originally published at techveda.live

The State of Automotive Grade Linux in 2026: Which Release to Build

#linux #automotive #embedded #yocto

The Automotive Grade Linux distribution is not one release on one baseline. As of 26 August 2026 its release-notes page documents three listed release series on three different Yocto Project releases: Ultimate Unagi on Scarthgap 5.0.x, Vibrant Vimba on Wrynose 6.0.x, and the old-stable Quirky Quillback on Kirkstone 4.0.x, which the Yocto Project now marks end of life. Which one you fetch depends on how long your programme has to be supported, and the answer is in the release notes rather than in any announcement.

If you have been asked to stand up an Automotive Grade Linux build this quarter, the first decision is also the one most likely to be wrong: which branch to fetch. The project publishes announcements, a product page and a release-notes wiki, and in August 2026 the three do not agree. An engineer who follows the press release lands on one baseline; an engineer who reads the release-notes table lands on a different one. The gap matters, because the two baselines have Yocto support windows that end two years apart, and a vehicle programme outlives both.

This is a practical problem rather than a criticism; large open source projects carry several series at once on purpose. What follows is what the artefacts say, why the project is structured this way, and what has moved since May.

What the Automotive Grade Linux release notes actually list

The release-notes wiki page at wiki.automotivelinux.org/agl-distro/release-notes records its own last modification as 24 August 2026. Read on 26 August 2026, it lists three named series.

Series	Yocto baseline	Upstream Yocto support	Fetch model	Main implication
Vibrant Vimba	Wrynose 6.0.x	To April 2030	`master` plus milestone manifest	Longest upstream horizon, but maturity and board coverage must be checked separately
Ultimate Unagi	Scarthgap 5.0.x	To April 2028	`unagi` branch plus manifest	Better fit where a cut branch and current board support matter
Quirky Quillback	Kirkstone 4.0.x	End of life	`quillback` branch	Legacy reproducibility only, unless the team owns the backports

Vibrant Vimba appears directly under the heading "Latest Stable Release". Its first listed feature is "Update to Yocto Project 'wrynose 6.0.x'". Its two documented builds are Milestone 1 v21.91.0 and Milestone 2 v21.92.0, and the Jira filter linked from both is labelled "Vibrant Vimba 22.0.0".

Ultimate Unagi is the 21.0.x series. Its feature list opens with "Update to Yocto Project 'scarthgap' 5.0.x" and goes on to name Qt 6.8, an upgrade to VSS 6.0, meta-flutter 3.38.3, the addition of meta-ros, KVM demo updates, and the line "Added sparrow-hawk board". Four point releases are documented. The notable-changes block for v21.0.2 reads "Yocto Project 'scarthgap' 5.0.18"; for v21.0.3 it reads "Yocto Project 'scarthgap' 5.0.19", plus layer and BSP updates and support for the Sifive hifive-premier-p550 board.

Quirky Quillback is the old-stable series, numbered 17.x, and its build-artifacts note reads "Uses Yocto 4.0.35 (YP kirkstone)".

The fetch commands are the clearest signal, because they encode the project's own view of each series. These run on your build machine.

raghu@techveda.org:~$ repo init -b unagi -m unagi_21.0.3.xml -u https://gerrit.automotivelinux.org/gerrit/AGL/AGL-repo
raghu@techveda.org:~$ repo sync

Unagi has a release branch of its own. So does Quillback, with -b quillback. Vibrant Vimba does not.

raghu@techveda.org:~$ repo init -b master -m vimba_21.92.0.xml -u https://gerrit.automotivelinux.org/gerrit/AGL/AGL-repo
raghu@techveda.org:~$ repo sync

The series the page calls "Latest Stable Release" is fetched from master with a milestone manifest, not from a cut release branch. That is a meaningful difference in what you are pinning. The branch it sits on is still the one under active development, whereas Unagi gives you both a manifest and a branch that is not moving underneath you.

Branch, manifest, and what actually counts as a baseline

Branch — a moving line of development.

Manifest — a pinned set of repository revisions, which is what makes a build reproducible.

Production baseline — a manifest, plus validation evidence, plus a maintenance plan naming who fixes what and for how long.

Why the project pins a Yocto LTS at all

Every series above is named after a Yocto Project release, and that is not decoration. A distribution built with OpenEmbedded inherits its recipe set, its toolchain, and its CVE-patching cadence from the Yocto release it is based on. When that release goes end of life, the recipes stop receiving fixes, and the burden of backporting moves to whoever is shipping the product.

The Yocto Project releases table, read on 26 August 2026, gives the windows. Scarthgap 5.0 was released in April 2024 and is long-term supported until April 2028. Wrynose 6.0 was released in April 2026 and is supported until April 2030. Kirkstone 4.0 came out in May 2022, reached 4.0.33 in February 2026, and is now marked end of life. The non-LTS releases show why the distinction exists: Walnascar 5.2 has been end of life since November 2025 and Whinlatter 5.3 is end of life too, both within roughly a year of release. Blacksail 6.1, due October 2026, is scheduled for six months of support.

One qualification matters before those dates are used for planning. They are upstream Yocto Project baseline support horizons and nothing more. They say nothing about how long AGL will maintain a given series, how long a silicon vendor will support its BSP layers, or what a vehicle programme will require. Each is a separate commitment, owned by a different party, and has to be confirmed with that party.

Set those windows against a vehicle programme. A platform entering production in 2028 and staying in service for a decade cannot be anchored to a baseline whose upstream fixes stop in April 2028. It cannot really be anchored to one that stops in April 2030 either, but the difference is two more years of somebody else doing the security backports before that work lands on your team. The same arithmetic governs kernel selection, and it is set out in more detail in Kernel LTS Support: Planning Embedded Products Around It.

The presence of a Kirkstone-based old-stable series in Automotive Grade Linux is not an oversight. Programmes that validated on Quillback years ago are still in the field, and the project keeps the series listed so those teams can reproduce a build. That does not make Kirkstone supported again. A team fetching -b quillback today takes on the backporting itself.

What changed between May and August 2026

Three months is enough to move the Automotive Grade Linux picture, and it has.

On 14 May 2026, at the AGL All Member Meeting in Tokyo, the Linux Foundation announced the initial availability of the AGL SoDeV reference platform, delivered through the Unified Code Base release codenamed Ultimate Unagi. The announcement described SoDeV as combining the Unified Code Base with Linux containers, VirtIO, the Xen hypervisor and the Zephyr RTOS, running on Renesas Sparrow Hawk reference boards, virtual machines and cloud environments. It stated the Yocto baseline as "Scarthgap LTS release 5.0.16", said Ultimate Unagi would be supported for two years, and committed to updates "approximately three weeks after each Scarthgap release by the Yocto Project". SoDeV had been announced in December 2025, so May is when developers could first fetch it.

By 24 August 2026, the date the release-notes page records for its last edit, two things had moved. Ultimate Unagi had reached v21.0.3 on Scarthgap 5.0.19, three point releases beyond the 5.0.16 named in May. And Vibrant Vimba, on Wrynose 6.0.x, had taken the "Latest Stable Release" heading.

The first is the three-week commitment being kept, visible in the artefacts rather than asserted. One caveat on the detail. The AGL notes for 21.0.3 cite Scarthgap 5.0.19, while the Yocto Project's own releases wiki, read the same day, lists 5.0.18 from June 2026 as the current Scarthgap version. The two sources were inconsistent when checked. The AGL entry records the baseline that AGL artefact was built against, which is not the same thing as a statement of upstream Scarthgap status, so confirm the current point release with the Yocto Project directly before resting maintenance assumptions on either number.

The second is a baseline change inside a single quarter. A team that started an Automotive Grade Linux evaluation from the May announcement is on Scarthgap; the page now points newcomers at Wrynose. Neither is wrong, but an evaluation framed as "we are building on what AGL ships" has already gone out of date once.

The product page adds a third answer. The Unified Code Base page on automotivelinux.org, read on 26 August 2026, still states "The latest release, UCB 16.0 (Prickly Pike)" and still describes the Unified Code Base as an in-vehicle infotainment distribution. The release-notes page's own introduction offers a fourth, saying "The latest stable release is Terrific Trout", directly above the heading naming Vibrant Vimba. Prose lags tables, and tables lag manifests.

Where SoDeV appears, and where it does not

This needs care, because the Automotive Grade Linux announcement and the release notes describe the same release in different vocabularies.

The string "SoDeV" does not appear anywhere on the AGL release-notes wiki page as read on 26 August 2026. Neither does the word "kernel", for any series. I checked the release-notes page, the Unified Code Base product page and the 14 May announcement, and found no published kernel version for any Unagi or Vimba point release. This post therefore does not state one, and you should not infer one from the Yocto baseline.

What the release notes do show is consistent with the announcement without confirming its component list. The Unagi layer list includes meta-virtualization, and the feature list includes "KVM demo updates" and the addition of the sparrow-hawk board. Those are the hooks a virtualised, multi-guest platform needs, but they are not proof that Xen and Zephyr are in the default image, and I did not verify that either way. If hypervisor configuration matters to your architecture, fetch the manifest and read the layer revisions.

One more detail is directly useful. Vibrant Vimba lists, verbatim, the known issue "R-Car Gen3 is not yet available (eta from upstream ~Oct) - use sparrow-hawk meantime". The newer baseline has lost a board that older builds had, with recovery expected around October. That is the kind of gap that does not appear in an announcement and does appear in a release note.

Choosing a branch

Reduce the Automotive Grade Linux branch decision to three questions.

How long does the support window need to run? If the programme extends past April 2028, Scarthgap's window ends inside it and Ultimate Unagi inherits that. Wrynose runs to April 2030. That is the strongest argument for Vibrant Vimba.

Do you need a cut release branch? Unagi has one. Vimba is fetched from master with a milestone manifest, and its milestone numbering is 21.9x rather than 22.0 even though the linked issue filter is labelled 22.0.0. Whether it is production-ready despite the "Latest Stable Release" heading is a question to put to the project directly rather than infer, and worth asking before committing a programme.

Which boards do you need today? The Unagi 21.0.3 artefacts table lists a Renesas H3 development board, QEMU on x86_64 and an Intel Up² board. Unagi added sparrow-hawk and, at 21.0.3, the Sifive hifive-premier-p550. Vimba currently lacks R-Car Gen3. If your bring-up target is one of those, board availability decides the branch regardless of support window, at least until October.

Underneath this sits an argument the project itself has been making. In a talk at the May All Member Meeting, published on the AGL blog on 23 June 2026, Hisao Munakata of Renesas argued that the software-defined vehicle transition repeats the Linux kernel's own 2.4 to 2.6 integration crisis, and that what resolved it was not any single technology but time-based release engineering: a fixed merge window, a validation-only period, and the discipline to defer whatever does not fit. He put the kernel's release-interval standard deviation across the v6 and v7 series at 2.83 days, and observed that automotive has no equivalent cadence. The three-week-after-Scarthgap commitment, and the point releases that followed it, are that discipline in practice. It is also why the release notes are the better source: a project on a cadence records where it is in its tables, not in its announcements.

A branch-selection checklist

Steps one and two decide the branch; the rest decide whether you can defend the choice.

Define the programme start date and the maintenance horizon it has to cover.
Confirm the boards you need and whether their BSP layers are present in the series you are considering.
Pin the exact manifest and archive the layer revisions it resolves to.
Confirm the current upstream Yocto support status with the Yocto Project, not a downstream page.
Read the release notes and issue tracker for the target branch, including known issues.
Verify virtualisation, image composition and board support from the actual layers, not announcement text.
Decide, and write down, who owns the backports once upstream support ends.

Key takeaways

Automotive Grade Linux lists three release series on three Yocto baselines: Vibrant Vimba on Wrynose 6.0.x, Ultimate Unagi 21.0.x on Scarthgap 5.0.x, and old-stable Quirky Quillback 17.x on Kirkstone 4.0.x.
Kirkstone is end of life; Scarthgap is supported to April 2028; Wrynose to April 2030. These are upstream Yocto horizons only, not AGL, BSP or programme commitments, but the support window should still drive the choice.
Unagi and Quillback have cut release branches. Vibrant Vimba is fetched from master with a milestone manifest.
Unagi moved from Scarthgap 5.0.16 in May to 5.0.19 by late August, which is the project's stated three-week cadence visible in the artefacts.
The announcement, the product page and the release-notes page each name a different "latest" release. Use the manifest as the reproducibility anchor, then validate maintenance status, BSP coverage and programme readiness separately.
Vibrant Vimba currently lists R-Car Gen3 as unavailable, with an upstream estimate of around October.

Frequently asked questions

Which Automotive Grade Linux release has the longest support window?
Vibrant Vimba, because it is based on Yocto Project Wrynose 6.0, which is supported until April 2030. Ultimate Unagi is based on Scarthgap 5.0, supported until April 2028.

Is Quirky Quillback still safe to build on?
It is still documented and still fetchable, but its Yocto baseline, Kirkstone 4.0, is marked end of life by the Yocto Project. A team building on it takes on the backporting of upstream recipe fixes itself.

What kernel version does Ultimate Unagi use?
The AGL release-notes page does not state one. The word "kernel" does not appear on that page for any series, and no kernel version was found on the Unified Code Base product page or in the May 2026 announcement either.

How do I fetch a specific Automotive Grade Linux release?
With repo init against the AGL-repo Gerrit URL, using the branch and manifest named in the release notes for that point release, then repo sync. Unagi uses -b unagi, Quillback uses -b quillback, and Vibrant Vimba uses -b master with a milestone manifest.

Is the AGL SoDeV platform the same thing as Ultimate Unagi?
The May 2026 announcement said the initial SoDeV reference platform was delivered through the Ultimate Unagi release. The name SoDeV does not appear on the release-notes page itself, so the mapping between the two is documented in the announcement rather than in the release notes.

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