Just Compatible

Server-side compatibility, safe world migration and preventive diagnostics for Minecraft 1.21.1 NeoForge. Install it only on the server together with Just Core; vanilla clients can connect normally.

Official downloads are available exclusively on CurseForge and Modrinth. GitHub contains source code, issues and changelogs, not mod binaries.

Three pillars

• World recovery: safely reconciles data after dimension or world-clock changes.
• Mod compatibility: targeted adapters for Waystones, Vinery, Starcatcher, Bountiful Baubles and vanilla Vaults.
• Server health: the early Mod Doctor reports explicit client-only JARs and conservative duplicate candidates before normal mod discovery.

Included integrations

• Waystones: repairs only unambiguous dimension references while preserving UUIDs and player discoveries. A backup is created first.
• Vinery: prevents existing wine age from going backwards when the primary world changes.
• Starcatcher: recognizes Overworld-, Nether- and End-like dimensions through vanilla dimension effects instead of hardcoded IDs.
• Bountiful Baubles: repairs stale attributes and migrated absolute clocks on supported artifacts after login, dimension travel or item use.
• Vanilla Vaults: diagnoses and repairs impossible absolute timers in loaded chunks while preserving keys, loot tables, state and rewarded players.

Mod Doctor safety

The Mod Doctor is conservative: it never deletes JARs, automatic quarantine is disabled by default, ambiguous findings are only reported, and Just Compatible, Just Core, Minecraft, NeoForge and language providers are protected. Every opt-in quarantine records the original and destination paths, SHA-256, version, reason and timestamp in an append-only manifest, and can be restored.

Commands

• /justcompatible scan — global read-only diagnostics.
• /justcompatible repair — applies only verified Waystones migrations after backup.
• /justcompatible doctor status — latest startup scan summary.
• /justcompatible doctor report — latest Mod Doctor report.
• /justcompatible doctor restore — restores available quarantined JARs; restart required.
• /justcompatible vaults scan|repair — loaded-chunk-only Vault timer tools.

Community and bug reports: https://discord.gg/cCHeBPKkD

Source and issue tracker: https://github.com/yofred09/just-compatible