Your ROOT_URL in app.ini is https://source.parasitstudio.de:63000/ but you are visiting https://source.parasitstudio.de/wirtz/music-synthesizer-for-android/blame/commit/2d433d10566665a856bb1d9c8477e7e356e727c8/j2se/.externalToolBuilders/Proto%20Builder.launch
You should set ROOT_URL correctly, otherwise the web may not work correctly.
<?xml version="1.0" encoding="UTF-8" standalone="no"?>
<launchConfiguration type="org.eclipse.ui.externaltools.ProgramBuilderLaunchConfigurationType">
<booleanAttribute key="org.eclipse.debug.ui.ATTR_LAUNCH_IN_BACKGROUND" value="false"/>
<stringAttribute key="org.eclipse.ui.externaltools.ATTR_BUILD_SCOPE" value="${working_set:<?xml version="1.0" encoding="UTF-8"?> <resources> <item path="/MusicSynthesizerJ2SE/core/com/levien/synthesizer/core/model/composite/Presets.proto" type="1"/> <item path="/MusicSynthesizerJ2SE/core/com/levien/synthesizer/core/model/sample/Proto.proto" type="1"/> <item path="/MusicSynthesizerJ2SE/core/com/levien/synthesizer/core/music/Music.proto" type="1"/> </resources>}"/>
<stringAttribute key="org.eclipse.ui.externaltools.ATTR_LOCATION" value="${project_loc}/../core/bin/protoc"/>
<stringAttribute key="org.eclipse.ui.externaltools.ATTR_RUN_BUILD_KINDS" value="full,incremental,auto,"/>
<stringAttribute key="org.eclipse.ui.externaltools.ATTR_TOOL_ARGUMENTS" value="--java_out=../core/gen src/com/levien/synthesizer/core/model/composite/Presets.proto src/com/levien/synthesizer/core/music/Music.proto"/>
<booleanAttribute key="org.eclipse.ui.externaltools.ATTR_TRIGGERS_CONFIGURED" value="true"/>
<stringAttribute key="org.eclipse.ui.externaltools.ATTR_WORKING_DIRECTORY" value="${project_loc}/../core"/>
</launchConfiguration>