PaperMC / PaperMC/Paper

Server crash starting spark background profiler

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status: needs triage version: 26.1.2
Dominant language
Java
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Description

Stack trace

https://pastebin.com/SUqs8Bnr

Plugin and Datapack List

pl
[18:52:24 INFO]: ℹ Server Plugins (2):
[18:52:24 INFO]: Paper Plugins:
[18:52:24 INFO]: - ServiceIO, Worlds
datapack list
[18:52:38 INFO]: There are 3 data pack(s) enabled: [vanilla (built-in)], [paper (built-in)], [file/bukkit (world)]
[18:52:38 INFO]: There are no more data packs available

Actions to reproduce (if known)

Start paper 26.1.2 using java 26

Paper version

This server is running Paper version 26.1.2-60-main@b4682bf (2026-05-04T06:25:04Z) (Implementing API version 26.1.2.build.60-stable)
You are running the latest version
Previous version: 26.1.2-53-39a1aa5 (MC: 26.1.2)

Other

No response

Contributor guide

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First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start with the linked Stack trace and reproduce Paper 26.1.2 on Java 26 while starting the server with the listed plugins and datapacks. Trace the spark background profiler startup path implicated by the crash; done means the same server starts without crashing under those conditions.

Written by the indexing model from the issue text.

Assessment

Tech stack
java, spark
Domain
backend, observability-sre
Issue type
Bug
Difficulty
4/5
Estimated time
3-5 days
Activity status
Quiet
Clarity
Mostly clear
Newbie friendliness
48/100

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