Fix players disconnecting when updating boss bars #1656
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On 1.20.2, the Minecraft client started clearing boss bars after the login packet, which meant that the ProxyServer#showBossbar API would result in the player getting kicked if the boss bar they were previously shown was updated after switching servers. Therefore, I have added BossBarManager which drops boss bar packets once the client enters the configure phase to ensure that they do not disconnect, and then re-adds the boss bar once the client enters the login phase. This ensures that clients do not receive boss bar updates for boss bars that they don't exist and causing them to disconnect. I have also taken care to ensure that this logic only applies on 1.20.2 and up, as it is not necessary for older clients.
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R00tB33rMan
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Oct 2, 2025
R00tB33rMan
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Oct 3, 2025
4drian3d
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On 1.20.2, the Minecraft client started clearing boss bars after the login packet, which meant that the ProxyServer#showBossbar API would result in the player getting kicked if the boss bar they were previously shown was updated after switching servers.
Therefore, I have added BossBarManager which drops boss bar packets once the client enters the configure phase to ensure that they do not disconnect (if the client receives boss bar packets during the configure phase it seems to queue them up and then immediately disconnect at the end of the configure phase, leaving no opportunity to re-send the boss bar creation packet), and then re-adds the boss bar once the client logs in.
This ensures that clients do not receive boss bar updates for boss bars that they don't exist causing them to disconnect. I have also taken care to ensure that this logic only applies on 1.20.2 and up, as it is not necessary for older clients.
In addition, I removed boss bar tracking for backend servers for 1.20.2 and up clients - as it is no longer necessary for them to be manually removed due to the aforementioned change.
Fixes #1529