How to Fix a SevTech: Ages Server That Keeps Crashing
SevTech: Ages runs on Forge 1.12.2 with Java 8, and generates heavy custom biome and age-progression data that make a few specific crash causes far more common here than on a newer pack.
See the SevTech: Ages pack page for boot-tested RAM data before you chase anything else.
1. Wrong Java version
SevTech needs Java 8 specifically. Java 11 or newer won't launch the server at all — this is the first thing to rule out if the server fails to start rather than crashing mid-session.
2. Mob Grinding Utils fan crash
A documented crash happens when a Mob Grinding Utils fan gets broken, from the mod's fan-breaking code specifically. If it's reproducible on fan breaking, update to a pack release where this was fixed, or avoid breaking fans in the meantime.
3. Outdated LWJGL
A NoSuchFieldError: OpenGL45 crash points to an outdated LWJGL — SevTech needs version 2.9.4. If you're on MultiMC or a similar launcher, this is set in the instance settings and worth checking directly rather than guessing.
4. Duplicate mods in the mods folder
A messy mods folder with duplicate jars from a previous install or a bad update is a known source of hard-to-diagnose crashes. If the crash log doesn't point anywhere obvious, deleting and re-uploading a clean mods folder is a faster fix than hunting for the duplicate by hand.
5. RAM below the 8 GB floor
SevTech generates custom biomes and keeps age-progression state in memory. Below 8 GB, expect consistent GC stalls while exploring; 10-12 GB is the real comfort zone for a group rather than a solo player.
FAQ
What Java version does SevTech: Ages need?+
Java 8 — it runs on Forge 1.12.2, and Java 11 or newer will fail to launch the server entirely. This is the first thing to check if the server won't start at all.
Why does my server crash when a Mob Grinding Utils fan gets broken?+
This is a documented crash in the mod's fan-breaking code. If it happens reliably, update to a pack version where it's been patched, or avoid breaking fans until you update.
I see a NoSuchFieldError: OpenGL45 crash — what's wrong?+
That's an outdated LWJGL. SevTech: Ages needs LWJGL 2.9.4 — if you're using a launcher like MultiMC, check the instance settings for the LWJGL version specifically.
Host SevTech: Ages on the right Forge 1.12.2 / Java 8 stack
CoalHost pins Java 8 and the correct Forge build for SevTech: Ages automatically, starting at the pack's 8 GB floor.
View SevTech: Ages Hosting →