# Teku Incident Report - Dependency conflict on Windows causing Teku to crash

10 October 2024

## Description
A clash in the library `jc-kzg-4844` version between Teku and the Besu dependency (v2.0.0 and v1.0.0) caused a startup issue on Windows machines only. Ubuntu and MacOS do not seem affected.

A manual workaround was needed (delete `jc-kzg-4844-1.0.0.jar` from `/lib`) for Teku to start.

[Link to Pull Request with fix](https://github.com/Consensys/teku/pull/8704)

## User Impact

Every user running 24.10.0 and 24.10.1 on Windows.

Only one user reported the issue in our Discord.

## Timeline (all times in UTC)

- `2024-10-10 06:44` User reported an issue on Discord (ethstaker)
- `2024-10-10 14:44` Raised Pull Request with fix
- `2024-10-10 18:05` Finishing testing the fix
- `2024-10-10 18:30` Published announcement
- `2024-10-16 11:15` Teku 24.10.2 reelased

## Root Cause Analysis
Since upgrading to the new version of `jc-kzg-4844` which uses a different `groupId`, there is a clash with Besu dependencies which are still on the old version under a different `groupId`. This causes our final build under `/lib` to include both jars which causes issues for Windows users.

## Resolution
Prevent the conflicting dependency from being included in the project transitively.

[Link to Pull Request with fix](https://github.com/Consensys/teku/pull/8704)

## Lessons Learned
This isn’t the first time a Windows-specific issue has caused us trouble. We decided to add a Windows server to our testing fleet to catch future issues with Windows. We do not have many users running Teku on Windows, but if we say that we support that system, we need to do better testing to ensure that it is working.