Jenkins 2.577 - Detached Plugins Leave the War

Jenkins published weekly jenkins-2.577 (2.577) on 11 August 2026, and the operator facing change is packaging: remaining detached plugins leave jenkins.war, cutting more than 20 MB from the download. Controllers that can reach the update center install those plugins as ordinary missing dependencies. Controllers that cannot must stage the files before the upgrade.

The full release notes and downloads are on the GitHub release page. The project points at the official changelog for the same weekly.

Change #27129 removes the last detached plugin copies that still shipped inside jenkins.war. The listed plugins are bouncycastle API, Command Agent Launcher, Oracle Java SE Development Kit Installer, JAXB, Trilead API, SSH server, JavaBeans Activation Framework (JAF) API, JavaMail API, and Instance Identity.

That code left Jenkins core between 2016 and 2022, across Jenkins 2.16 through 2.356. The war kept copies so that upgrades from those old versions, and plugins built against them, would keep working. 2.577 ends that compatibility copy.

Most running controllers are not affected. If the update center is reachable, Jenkins resolves and installs these plugins over the network whenever something needs them, the same path it uses for any other missing plugin dependency. That behavior does not depend on which Jenkins version is running. Sites that already have the plugins installed see a smaller war and no new plugin set.

The size cut is the clear win for image builds and artifact caches. A smaller war is cheaper to pull into a controller image and faster to copy into air gapped mirrors. The loser is any site that treated the war as a self contained plugin bundle and never talks to the update center. Those controllers used to get a silent copy of these plugins from the war itself. They will not get that copy after 2.577.

This is a packaging change, not a pipeline engine change. Job DSLs, agent protocols, and executor scheduling are not rewritten in this weekly. ETL jobs that Jenkins already launches keep the same launch path. The risk is missing plugin files at startup or at plugin install time, not a new scheduler algorithm.

The experimental page work in #26863 makes those pages consistent. The side panel scrolls on its own. The build bar stays sticky.

That matters if operators spend time on those experimental views while a build is running. It does not add a config key, a CLI flag, or a new REST field. Treat it as chrome. Pipeline runtimes and agent launchers do not change because the build bar sticks.

The remaining note is for plugin authors. Change #27165 corrects the Javadoc for QuotedStringTokenizer.quote(String) so it matches the real behavior: quoting is unconditional. The notes do not describe a runtime change. Plugin code that already called the method keeps the same quoting. Operators can skip that item.

This weekly is not a prerelease. It is a normal 2.577 weekly. Read the GitHub release page and the official changelog before rolling it onto a controller that still sits on Jenkins 2.356 or earlier.

If the controller can reach the update center, plan a normal weekly upgrade. Jenkins will fetch the now unbundled plugins when something needs them. Controllers already past 2.356 with these plugins present should see only the smaller war.

If the controller has no update center access, you are on the affected path. Download the plugin files from the update center on a machine that can reach it, then place them in the plugins directory of the Jenkins home directory before starting 2.577. Do the same before installing a plugin built against a baseline of 2.356 or earlier, because core will no longer pull those detached plugins in automatically.

The notes do not list a config file migration, a new system property, or a required Groovy init script. The work is artifact staging, not XML rewrite. Confirm the plugins directory under Jenkins home (JENKINS_HOME/plugins) already holds the listed plugins, or stage them, then start the new weekly.

Plugin authors can ignore the war change unless they still ship against a very old core baseline. The Javadoc correction on QuotedStringTokenizer.quote(String) is documentation only.