After upgrading our Jenkins instance to LTS 2.541.2, we began experiencing persistent agent disconnections. Before the upgrade, all agents were functioning normally. Immediately after the upgrade, several agents went offline with the message: ‘This node is offline because it uses an old agent.jar and remoting version 3327.v868139a_d00e0 in red.’
Actions We Have Already Performed
We have carried out several corrective steps:
Updated the Jenkins agent to the latest version recommended by the controller.
Verified that all required agent‑related plugins, including the Swarm Client plugin, are installed and up to date.
Updated the swarm‑client.jar manually and deployed it via Artifactory.
Ensured that Content Security Policy (CSP) is enabled as recommended for LTS 2.541.2 in the Jenkins documentation.
Current Issue
Even after performing these actions, the agents still fail to connect. Jenkins continues to prompt for an agent update, and after updating, the agents still do not come online.
Does anyone have any insights or ideas about this issue?