Old mods and dependencies on 26.1

Checked against Fabric’s documentation and blog on 2 November 2026.

Why they fail

26.1 is the first Minecraft version without obfuscation. Mods built for 1.21.11 or older were compiled against other names, so they need at least a recompile to run on 26.1 (Fabric, 14 March 2026). Fabric’s porting page goes further: no existing mod for 1.21.11 or older works on 26.1, even as a compile-only dependency (Fabric: Porting to 26.1).

Fixes

1. Replace every dependency with its 26.1 build. If a mod you need has no 26.1 build yet, remove it until it has one.
2. Use the plain configurations on Fabric. modImplementation, modCompileOnly and modApi become implementation, compileOnly and api with the net.fabricmc.fabric-loom plugin.
3. Depend on fabric-api, not fabric. Fabric API no longer provides the fabric mod id. If fabric.mod.json says "fabric" in depends, change it to "fabric-api" (Fabric, 14 March 2026).
4. Check for removed Fabric API modules. fabric-convention-tags-v1 and fabric-loot-api-v2 are gone in 26.1, and so is the HudRenderCallback event (use HudElementRegistry).

In Linen

• Linen Check reads the build and names the file and the fix.
• Claude Code, Anthropic’s extension, on your own Claude plan, gets Linen’s tools (gradle, lookup_symbol, search_source and others) and Linen Check after every edit. Ask it to go through your dependencies with you.