Sinytra Connector ERROR
Sinytra Connector lets you run Fabric mods on a Forge or NeoForge server by translating Fabric APIs to Forge equivalents at load time. When it logs '[Sinytra Connector] ERROR', a Fabric mod has hit a code path that Connector can't translate — usually a rendering or networking call that's structurally different between the two loaders.
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How to fix it
- 1
Identify the failing Fabric mod
The error line names the mod ID. It usually looks like 'Failed to process mod sodium: ...' or 'Could not load class for mod XXX'. That mod is the suspect — Connector worked fine until it.
- 2
Look for a native Forge equivalent
Most popular Fabric mods have a Forge port or a direct equivalent. Sodium → Embeddium, Iris → Oculus, Lithium → Performant. If a Forge-native version exists, use that instead of running the Fabric mod through Connector.
- 3
Update Connector itself
Connector compatibility improves with every release. If your error is from an older Connector build, updating to the latest beta often resolves the issue.
- 4
Disable the Fabric mod if no replacement exists
Some Fabric-only mods (especially mods touching client-side rendering deeply) simply don't translate. Move the .jar out of mods/ and accept the lost feature, or migrate the world to a pure-Fabric pack.
Alternative causes
These can produce the same error message — worth ruling out if the steps above don't resolve it.
Cascading NoClassDefFoundError after the Connector error
Connector errors almost always cascade into 'java.lang.NoClassDefFoundError' for a Fabric-only class. The Connector line is the root cause — fix that and the cascade disappears.
Two copies of the same mod (one Forge, one Fabric)
If a modpack installs both the Forge-native and the Fabric-via-Connector version of the same mod, Connector will refuse to translate the second one. Pick one and delete the other.
Frequently asked
Is Sinytra Connector safe for production servers?
Yes for most mods, no for some. Stable for content mods, item mods, food mods, and most worldgen mods. Less stable for performance mods (Sodium, Lithium) and rendering mods (Iris). Test before relying on it.
Will Sinytra Connector survive future MC updates?
Each MC version requires a Connector update; the project tracks Forge releases closely but expect a 1-4 week lag after a new MC version drops.
Can I run a Forge modpack and add one Fabric mod via Connector?
Yes — that's the most common Connector use case. Just be sure the Fabric mod isn't already shipped as a Forge port (you'd be loading it twice).
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Last reviewed 2026-06-05. If a step is wrong or out of date, tell us — we'll fix the article and the auto-pattern at the same time.