Cardboard is an implementation of the popular Bukkit/Spigot/Paper Modding API for FabricMC. This mod lets you use plugins that are made for Bukkit and it's derivatives (Spigot & Paper) on a Fabric modded server.
Fabric version chart:
| Support | Minecraft | Git Branch | Dev Status |
|---|---|---|---|
| ✅ | Fabric 26.2 | ver-26.2-release | Active |
| ✅ | Fabric 26.1.2 | ver/26.1 | Low |
| ✅ | Fabric 1.21.11 | ver/1.21.11 | Low |
| ✅ | Fabric 1.21.1 | ver/1.21 | Low |
| ❌ | <= 1.20 |
See Supported Versions for more details. & View Downloads
Requires JDK 25 (auto-provisioned by the Gradle toolchain resolver) and Java 25 at runtime.
./gradlew clean build --no-daemon --stacktraceThe mod jar is produced at build/libs/Cardboard-<version>.jar. Drop it into a
Fabric server's mods/ folder alongside Fabric API
and iCommonLib; Bukkit plugins then go in plugins/.
The canonical release artifact is build/libs/Cardboard-<version>.jar from the
normal root build above. Cardboard supports reproducible builds with the
checked-in Gradle Wrapper 9.5.1 and Temurin JDK 25: two clean, full-history Git
checkouts of the same revision and dependency set must produce the same JAR
SHA-256, even when the checkout directories differ.
GitVersion contains source-derived diagnostics only: the project identity and
version, full Git commit SHA, commit count, commit timestamp, configured release
branch, and dirty state. Its compatibility BUILD_DATE and BUILD_UNIX_TIME
fields are derived from the commit timestamp rather than the wall clock. It does
not embed the hostname, username, absolute checkout path, or local branch.
Generated source lives below build/, so a normal build does not write into
src/main/java or dirty tracked sources.
The reproducibility contract applies to clean, full-history checkouts. A dirty
working tree is deliberately identified with DIRTY = 1 and is not guaranteed
to match the clean artifact for its HEAD. A shallow checkout cannot supply the
same history-derived revision count and is outside this contract.
Run the verifier and its own regression tests from the repository root:
python3 -B -m unittest discover -s tools/reproducibility/tests -p 'test_*.py' -v
python3 tools/reproducibility/verify.pyThe verifier performs two clean Wrapper builds of the reproducibleJar task,
compares the canonical JARs byte for byte, and fails with entry-level ZIP
diagnostics on any difference.
For the stronger different-directory procedure and report layout, see
tools/reproducibility/README.md.
The Cardboard CI GitHub Actions workflow runs for pull requests and pushes to
the maintained ver-26.2-release branch. It uses Temurin 25, Python 3.11, and
the checked-in Gradle Wrapper. Three independent jobs run the root Cardboard
build/regression suite, the isolated torture-harness build/regression suite,
and the reproducibility verifier against two full-history checkout paths.
Run the same verification locally from the repository root:
./gradlew clean build --no-daemon --stacktrace
./gradlew -p tools/torture/plugin clean build --no-daemon --stacktrace
python3 -m py_compile tools/torture/run.py tools/torture/tests/test_run.py
python3 -m unittest discover -s tools/torture/tests -p 'test_*.py' -v
python3 -B -m unittest discover -s tools/reproducibility/tests -p 'test_*.py' -v
python3 tools/reproducibility/verify.pySuccessful jobs retain the Cardboard and torture-helper JARs for 14 days. On build/test failure, any produced Gradle reports and Python test log are retained for 7 days. A reproducibility mismatch additionally retains both canonical JARs and its comparison report for 7 days.
Ordinary CI does not boot Minecraft, contact the deployment VPS, use RCON, or
run smoke/burst/soak scenarios. Those runtime checks require a disposable
server and remain manual under the procedure in tools/torture/README.md.
Point 1's six-hour soak is not repeated by pull-request verification.
Reproducibility verification is limited to Point 3 build identity; it does not
run or replace the real-plugin compatibility matrix from Point 4.
Minecraft 26.2 moved the entity and block-entity constants out of their type
classes (EntityType.X -> EntityTypes.X, BlockEntityType.X ->
BlockEntityTypes.X), stripped the colour metadata from ChatFormatting in
favour of world.scores.TeamColor, and ships Adventure 5. Cardboard on this
branch targets Paper-API 26.2.build.110-stable and Adventure 5.2.0.
This repository is derived from CardboardPowered/cardboard
and carries its history and license. The ver-26.2-release branch adds Minecraft 26.2 support.
We inherit the license from Paper. See Paper's License for full details. SrgLib is also licensed under MIT.
- BukkitTeam, Spigot, and Paper for their work on the API.
- Glowstone for the library loader.
- md_5's SpecialSource, SrgLib by Techcable & Orion, MinecraftMapping by Phase
- Contributors to Cardboard
This project is partnered with ApexHosting! Join our test server, cardboardmod.apexmc.co:25666, or get a Minecraft server by clicking on the banner below:
