Reading the log

Fabric Crash: NumberFormatException: For input string: "4 "

What the log looks like

NumberFormatException: For input string: "4 "
IllegalArgumentException: can't parse argument number: 4 
net\.fabricmc\.loader\.impl\.util\.Localization\.format\(Localization\.java:\d+\)\s+.*ResultAnalyzer\.addErrorToList

How to fix it

  1. Open `.minecraft/logs/latest.log` in a text editor and find the `[main/WARN]: Mod resolution failed` section right above `Uncaught exception in thread "main"`.
  2. Read the `Immediate reason:` and `Reason:` lines to see which mods conflict (`NEG_HARD_DEP ... breaks ...`) or are for the wrong Minecraft version (`HARD_DEP ... depends minecraft`).
  3. Remove or update the conflicting mods listed in that line—for example, remove OptiFabric if you are using Sodium/Iris, or update Iris and MaLiLib so their versions match.
  4. Update Fabric Loader to the latest version in your launcher settings so future mod incompatibility screens display properly without crashing on your system language.
LoadersFabric, Quilt
SeverityStops the game
CategoryReading the log

Check your own log

Related errors

Reading the logForge LoadingFailedException: Loading errors encounteredLook at the lines immediately inside 'Loading errors encountered: [ ... ]' to find the failing mod's name and Reading the logForge Mod Loading Crash (LoaderExceptionModCrash)Open the crash report and find the 'LoaderExceptionModCrash: Caught exception from <Mod Name>' line to see whiReading the logHarmless Server Warning: ClassNotFoundException: net/minecraft/class_5616 (registrate-fabric)Ignore [main/WARN] lines referencing net/minecraft/class_5616 (from registrate-fabric) as well as class_906 anReading the logInvocationTargetException — the real error is wrapped insideThis exception never is the cause — it only wraps another oneReading the logNullPointerException: "this.cpuVendor" is null (OSHI Warning)Check that this message is marked `[main/WARN]` in your log; it does not stop Minecraft or your server from ruReading the logReportedException: Exception generating new chunkOpen your `latest.log` or crash report and scroll below `net.minecraft.ReportedException: Exception generating