enhancement: multi loader support

.github/workflows/multiloader.yml

@@ -0,0 +1,77 @@
+name: Multiloader Build
+
+# Builds the multiloader (multiloader/) — MultiLoader-Template layout
+# (ModDevGradle common+neoforge, Fabric Loom fabric; no architectury-loom).
+# Independent of the root single-loader build (build.yml).
+#
+# STRICT: there is no continue-on-error, so ANY matrix cell that fails to build
+# fails the whole workflow. All four loader x version cells are verified buildable
+# from public artifacts (gradle MCP, 2026-06-20):
+#   - neoforge @ 26.1.2  -> NeoForge 26.1.2.76
+#   - neoforge @ 26.2    -> NeoForge 26.2.0.6-beta (now on the public NeoForged Maven)
+#   - fabric   @ 26.2    -> Fabric Loom 1.17 + fabric-api 0.152.1+26.2 (de-obf, no mappings)
+#   - fabric   @ 26.1.2  -> Fabric Loom 1.17 + fabric-api 0.151.0+26.1.2; needs the access
+#                          widener (fabric/src/main/resources/nerospace.accesswidener) because
+#                          vanilla MC 26.1.2 kept BlockEntityType's constructor private
+#                          (Mojang made it public in 26.2; NeoForge widens it on both).
+
+on:
+  push:
+    paths:
+      - "multiloader/**"
+      - ".github/workflows/multiloader.yml"
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  build:
+    name: ${{ matrix.loader }} @ MC ${{ matrix.mc }}
+    runs-on: ubuntu-latest
+    strategy:
+      fail-fast: false
+      matrix:
+        include:
+          - loader: neoforge
+            mc: "26.1.2"
+          - loader: neoforge
+            mc: "26.2"
+          - loader: fabric
+            mc: "26.1.2"
+          - loader: fabric
+            mc: "26.2"
+
+    steps:
+      - name: Checkout repository
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+          fetch-tags: true
+
+      - name: Setup JDK 25
+        uses: actions/setup-java@v5
+        with:
+          java-version: "25"
+          distribution: "temurin"
+
+      - name: Setup Gradle
+        uses: gradle/actions/setup-gradle@v4
+
+      - name: Make Gradle wrapper executable
+        run: chmod +x ./multiloader/gradlew
+
+      - name: Build ${{ matrix.loader }} for MC ${{ matrix.mc }}
+        working-directory: multiloader
+        run: >-
+          ./gradlew :${{ matrix.loader }}:build
+          -Pminecraft_version=${{ matrix.mc }}
+          --stacktrace
+
+      - name: Upload ${{ matrix.loader }} ${{ matrix.mc }} jars
+        if: success()
+        uses: actions/upload-artifact@v4
+        with:
+          name: nerospace-${{ matrix.loader }}-${{ matrix.mc }}
+          path: multiloader/${{ matrix.loader }}/build/libs/*.jar
+          if-no-files-found: ignore

.gitignore

@@ -49,3 +49,5 @@ repo/
 !**/src/**/repo/
 PROJECT_PLAN.md
 /tools/__pycache__
+runs/
+/multiloader/fabric/runs

.vscode/launch.json

@@ -1,7 +1,6 @@
 {
-  "//": "Generic, committable run configs for Nerospace. Paths use ${workspaceFolder} so they work on any machine, and each config\u0027s preLaunchTask (see tasks.json) regenerates build/moddev/\u003crun\u003eArgs.txt before launch so it never fails after a clean. ModDevGradle no longer overwrites this file: build.gradle sets disableIdeRun() on every run, so this file is the source of truth.",
+  "//": "Run/debug configs for the ROOT single-loader NeoForge build (project \u0027nerospace\u0027). modFolders points at bin/main (IDE classes) AND build/resources/main (where the generated neoforge.mods.toml lives). Multiloader run/debug lives in multiloader/.vscode + nerospace.code-workspace.",
   "version": "0.2.0",
-  "//classPaths": "Each config launches from build/moddev/devlaunchClasspath.jar, a gradle-generated pathing jar whose MANIFEST Class-Path lists the exact NeoForge/Minecraft/DevLaunch dev jars for the version in gradle.properties (built by the devLaunchPathingJar task, which finalizes every prepare*Run preLaunchTask). With no $Auto entry, classPaths REPLACES the IDE-resolved runtime classpath, so a neo_version bump can never again launch a stale NeoForge and crash FML with \u0027version is null\u0027. projectName is kept only for source/breakpoint mapping; the mod loads via -Dfml.modFolders, not the classpath. Verified end-to-end: launching with only this jar boots GameTestServer and passes all gametests.",
   "configurations": [
     {
       "type": "java",

.vscode/tasks.json

@@ -1,5 +1,5 @@
 {
-  "//": "preLaunchTasks for launch.json: each runs the matching ModDevGradle 'prepare<Run>' task to (re)generate build/moddev/<run>Args.txt before launch, so launches never fail after a clean. Cross-platform: gradlew on Linux/macOS, gradlew.bat on Windows.",
+  "//": "Root single-loader prepareRun tasks (preLaunchTasks for the root launch.json) + Multiloader (multiloader/) build/run tasks. The multiloader tasks shell out to multiloader's OWN wrapper (Gradle 9.5.1) with cwd=multiloader; they do NOT need the multiloader Gradle build to be imported by the Java extension, so they work from the repo-root window.",
   "version": "2.0.0",
   "tasks": [
     {
@@ -37,6 +37,132 @@
       "args": ["prepareDataRun"],
       "presentation": { "reveal": "silent", "panel": "shared", "clear": false },
       "problemMatcher": []
+    },
+
+    {
+      "label": "ML: Run Fabric Client - 26.2",
+      "detail": "Multiloader RUN tasks launch the game directly via Gradle (no debugger). For breakpoint debugging, open nerospace.code-workspace and use its Run & Debug entries.",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":fabric:runClient", "-Pminecraft_version=26.2"],
+      "presentation": { "reveal": "always", "panel": "dedicated", "clear": true },
+      "problemMatcher": []
+    },
+    {
+      "label": "ML: Run NeoForge Client - 26.1.2",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":neoforge:runClient", "-Pminecraft_version=26.1.2"],
+      "presentation": { "reveal": "always", "panel": "dedicated", "clear": true },
+      "problemMatcher": []
+    },
+    {
+      "label": "ML: Run Fabric Client (pick MC)",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":fabric:runClient", "-Pminecraft_version=${input:mlMcVersion}"],
+      "presentation": { "reveal": "always", "panel": "dedicated", "clear": true },
+      "problemMatcher": []
+    },
+    {
+      "label": "ML: Run Fabric Server (pick MC)",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":fabric:runServer", "-Pminecraft_version=${input:mlMcVersion}"],
+      "presentation": { "reveal": "always", "panel": "dedicated", "clear": true },
+      "problemMatcher": []
+    },
+    {
+      "label": "ML: Run NeoForge Client (pick MC)",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":neoforge:runClient", "-Pminecraft_version=${input:mlMcVersion}"],
+      "presentation": { "reveal": "always", "panel": "dedicated", "clear": true },
+      "problemMatcher": []
+    },
+    {
+      "label": "ML: Run NeoForge Server (pick MC)",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":neoforge:runServer", "-Pminecraft_version=${input:mlMcVersion}"],
+      "presentation": { "reveal": "always", "panel": "dedicated", "clear": true },
+      "problemMatcher": []
+    },
+
+    {
+      "label": "ML: Build both loaders (pick MC)",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": ["build", "-Pminecraft_version=${input:mlMcVersion}"],
+      "group": "build",
+      "presentation": { "reveal": "always", "panel": "shared", "clear": true },
+      "problemMatcher": []
+    },
+    {
+      "label": "ML: Build NeoForge (pick MC)",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":neoforge:build", "-Pminecraft_version=${input:mlMcVersion}"],
+      "group": "build",
+      "presentation": { "reveal": "always", "panel": "shared", "clear": true },
+      "problemMatcher": []
+    },
+    {
+      "label": "ML: Build Fabric (pick MC)",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":fabric:build", "-Pminecraft_version=${input:mlMcVersion}"],
+      "group": "build",
+      "presentation": { "reveal": "always", "panel": "shared", "clear": true },
+      "problemMatcher": []
+    },
+    {
+      "label": "ML: Generate Fabric VS Code run configs (pick MC)",
+      "detail": "Loom's real task is 'vscode' (not genVsCodeRuns). Writes multiloader/.vscode/launch.json; use it from nerospace.code-workspace.",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":fabric:vscode", "-Pminecraft_version=${input:mlMcVersion}"],
+      "presentation": { "reveal": "always", "panel": "shared", "clear": true },
+      "problemMatcher": []
+    },
+    {
+      "label": "ML: Refresh loom caches",
+      "type": "process",
+      "command": "${workspaceFolder}/multiloader/gradlew",
+      "windows": { "command": "${workspaceFolder}/multiloader/gradlew.bat" },
+      "options": { "cwd": "${workspaceFolder}/multiloader" },
+      "args": [":fabric:build", "-Pminecraft_version=${input:mlMcVersion}", "--refresh-dependencies"],
+      "presentation": { "reveal": "always", "panel": "shared", "clear": true },
+      "problemMatcher": []
+    }
+  ],
+  "inputs": [
+    {
+      "id": "mlMcVersion",
+      "type": "pickString",
+      "description": "Minecraft version for the multiloader build",
+      "options": ["26.1.2", "26.2"],
+      "default": "26.2"
     }
   ]
 }