From e6a6392565cd3fc412214f63157c5f7df3faf452 Mon Sep 17 00:00:00 2001
From: SashegDev <gdsasheg@gmail.com>
Date: Mon, 13 Jul 2026 14:37:31 +0000
Subject: [PATCH] fix: dont intercept Forge -p, its a hardcoded bootstrap list
 not ${classpath}

Forge manifest -p is 8 hardcoded bootstrap JARs using ${library_directory},
not ${classpath}. Intercepting it replaced those with ALL libraries causing
duplicate module errors. Version jar stays on -cp only (not -p).
---
 .../launch/LaunchCommandBuilder.java          | 41 ++++++-------------
 1 file changed, 13 insertions(+), 28 deletions(-)

diff --git a/launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/launch/LaunchCommandBuilder.java b/launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/launch/LaunchCommandBuilder.java
index 8fdd0d3..e784e9d 100644
--- a/launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/launch/LaunchCommandBuilder.java
+++ b/launcher/launcher/src/main/java/sashegdev/zernmc/launcher/minecraft/launch/LaunchCommandBuilder.java
@@ -63,50 +63,35 @@ public class LaunchCommandBuilder {
             // always use ModLauncher as main class (version.json might have
             // BootstrapLauncher which breaks with Java module system)
             if ("forge".equals(loaderType) || "neoforge".equals(loaderType)) {
-                // Build TWO classpaths for Forge/NeoForge:
-                // 1. modulePath: libraries only (for -p module path) — version jar excluded
-                //    to prevent split-package conflict with Forge's "minecraft" module
-                // 2. classpath: libraries + version jar (for -cp classpath) — version jar
-                //    included so PreparableReloadListener and other MC classes are loadable
-                String modulePath;
+                // Forge manifest's -p is a HARDCODED list of 8 bootstrap JARs
+                // (bootstraplauncher, securejarhandler, asm-*, JarJarFileSystems)
+                // using ${library_directory}. Version jar is NOT on -p.
+                // Put version jar on -cp only → PreparableReloadListener loadable,
+                // no _1._20._1 vs minecraft split-package conflict.
                 String classpath;
                 if (manifest != null) {
-                    modulePath = buildClasspathFromManifest(manifest, false);
                     classpath = buildClasspathFromManifest(manifest, true);
                 } else {
-                    modulePath = "";
                     classpath = "";
                 }
-                if (modulePath == null || modulePath.isEmpty()) {
-                    modulePath = buildVanillaClasspath();
-                }
                 if (classpath == null || classpath.isEmpty()) {
-                    classpath = modulePath;
+                    classpath = buildVanillaClasspath();
                 }
 
                 command.add("-cp");
                 String cpFile = writeClasspathFile(classpath);
-                String mpFile = writeClasspathFile(modulePath);
                 command.add(cpFile);
 
-                // Add JVM arguments from version.json manifest.
-                // Intercept -p / --module-path to use mpFile (no version jar)
-                // and -cp / --classpath to skip (we already added our own -cp).
+                // Add JVM arguments from version.json manifest as-is.
+                // Forge's -p is a HARDCODED list of 8 bootstrap JARs (bootstraplauncher,
+                // securejarhandler, asm-*, JarJarFileSystems) — NOT ${classpath}.
+                // Do NOT intercept it. Version jar stays on -cp only (not -p),
+                // preventing _1._20._1 vs minecraft split-package conflicts.
                 if (manifest != null) {
                     Map<String, String> vars = buildVariableMap(options);
                     vars.put("classpath", cpFile);
-                    List<String> jvmArgs = manifest.getJvmArguments();
-                    for (int i = 0; i < jvmArgs.size(); i++) {
-                        String raw = jvmArgs.get(i);
-                        if (("-p".equals(raw) || "--module-path".equals(raw)) && i + 1 < jvmArgs.size()) {
-                            command.add(raw);
-                            i++;
-                            command.add(mpFile);
-                        } else if (("-cp".equals(raw) || "--classpath".equals(raw)) && i + 1 < jvmArgs.size()) {
-                            i++;
-                        } else {
-                            command.add(resolveVariable(raw, vars));
-                        }
+                    for (String arg : manifest.getJvmArguments()) {
+                        command.add(resolveVariable(arg, vars));
                     }
                 }