Client startup extremely slow (400+ seconds) when FerriteCore and Supplementaries are both installed (NeoForge 1.21.1)

[Esteban-Chielens]

Summary

I’m running into a very large client startup slowdown (400+ seconds) that only occurs when FerriteCore and Supplementaries are both installed on NeoForge 1.21.1. As soon as FerriteCore is removed, startup times return to normal.

Environment

• Minecraft: NeoForge 1.21.1
• Base modpack: Optimized FPS (Modrinth), used as a starting point
• Issue occurs on the client, during startup (before the main menu)
• System resources don’t appear to be the bottleneck (CPU/RAM usage remains normal during the hang)

What Happens

• Supplementaries + FerriteCore enabled

  • Client startup takes 400+ seconds
  • No clear errors or warnings in the logs

• Supplementaries enabled, FerriteCore disabled

  • Startup time is normal

• FerriteCore enabled, Supplementaries disabled

  • Startup time is normal

Because each mod works fine on its own, this looks like an interaction issue rather than a standalone bug in either mod.

Profiling Results

I profiled client startup using Spark. The vast majority of the time is spent in:

net.minecraft.client.resources.model.BlockStateModelLoader

Specifically during blockstate model loading.

Spark reports:

• Without Supplementaries: https://spark.lucko.me/HSeULPjj0e
• With Supplementaries: https://spark.lucko.me/73wz1AxJ5f

Blockstate Stats

Using Moonlight Lib’s blockstate_stats command, I got the following:

• Total blocks: 8,667
• Total blockstates: 162,458
• Average blockstates per block: 18.74

These numbers were reviewed by the Supplementaries developer and considered normal. This suggests the slowdown isn’t due to an unusually large number of blocks or blockstates, but rather how they’re being processed during model loading.

Troubleshooting So Far

• Did a binary search through mods → disabling FerriteCore consistently fixes the issue

• Tried disabling performance/render-related mods with no change:

  • Embeddium / Sodium
  • ETF / EMF
  • Fusion (connected textures)

• Logs don’t show anything obvious that explains the delay:
  https://mclo.gs/mgN0DoL

Expected Behavior

FerriteCore shouldn’t introduce extreme client startup delays when used with common content mods like Supplementaries, especially since both are widely used together in performance-focused modpacks.

Thoughts / Hypothesis

My guess is that some FerriteCore optimization path (possibly related to deduplication, caching, or model handling) is interacting poorly with Supplementaries during the client model bake phase.

This does not seem to be caused by:

• Excessive block count
• Excessive blockstate count
• GPU load
• Texture or emissive/connected texture mods

What I’m Looking For

Any guidance on:

• Known FerriteCore issues related to blockstate or model processing on NeoForge 1.21+
• Debug options or config flags that could help narrow this down
• Whether this might be a known incompatibility or a recent regression

---

If needed, I can also:

• Reduce this to a minimal reproduction setup
• Reformat it to match the project’s issue template
• Help track down a possible third mod if this is a three-way interaction

[malte0811]

I am unable to reproduce this with either:

• The "Optimized fps" pack plus Supplementaries or
• FerriteCore plus Supplementaries.

Please provide a minimal list of mods required to reproduce the issue. Your log contains a modlist, but I would prefer not to download ~110 mods manually.

[Esteban-Chielens]

I've tried to narrow it down, and I got the modlist down to handcrafted, ferrite core, supplementaries, modernfix and platform. It seems the issue stops whenever I disable any of those. I tried creating a new modpack with those exact mods installed and there the issue did not seem to appear for some reason. I searched other github pages and came across this issue which seems very related: ItsBlackGear/Platform#12 .

[malte0811]

Thank you for the list, and also for pointing out the other issue. I was able to reproduce the issue with the mods you mentioned. Dynamic Resources are disabled in ModernFix by default and are in some way part of the issue, that's probably why your copied pack still started quickly. I will do more debugging on this on the weekend.