MuseScore 4 fails to export parts via JSON batch export – segmentation fault or no output

Issue type

Import/export issue

Description with steps to reproduce

When exporting .mscz files using the -j batch export option in MuseScore 4, the expected output (full score + individual parts as PDFs) is either not created at all or causes a segmentation fault.

This issue occurs across all MuseScore 4.x versions tested, including the latest release and a current nightly build.
In contrast, MuseScore 3.6.2 performs the same operation correctly.

Expected behavior

MuseScore should export:

• testfile.pdf (full score)
• testfile_Tenor.pdf and testfile_Bass.pdf (individual parts)

using the following export_job.json:

[
  {
    "in": "./testfile.mscz",
    "out": [
      "testfile.pdf",
      ["testfile_", ".pdf"]
    ]
  }
]

Command

musescore.AppImage -j export_job.json

How to create the test files

Create in MuseScore v3.6.2

• File → New…
• Enter title: v3.6.2
• Choose Instruments
• Vocals - Tenor
• Vocals - Bass
• Finish
• File → Parts…
• All parts
• OK
• File → Save as…
• Filename: v3.6.mscz
• Save

Create in MuseScore v4.0.0

• File → New…
• Choose Instruments
• Vocals - Tenor
• Vocals - Bass
• Done
• File → Save as…
• Filename: v4.0.0.mscz
• Save

Convert to MuseScore v4.0.0

• Open test file v3.6.mscz with MuseScore v4.0.0
• Change title to: 3t4
• File → Save as…
• Filename: 3to4.mscz
• Save

Results summary

MuseScore Version	v3.6.2.mscz	v4.0.0.mscz	3to4.mscz
MuseScore 3.6.2	✅ Full + Parts (OK)
MuseScore 4.0.0	❌ No files
MuseScore 4.1.1	❌ No files
MuseScore 4.2.1	❌ No files
MuseScore 4.3.2	❌ No files
MuseScore 4.4.4	❌ No files	❌ No files	❌ No files
MuseScore 4.5.2	❌ Segfault	❌️ Segfault	⚠ Full OK + Parts blank
MuseScore Nightly	❌️ Segfault	⚠️ Full OK + Parts missing	❌️ Segfault

Environment

• Ubuntu 22.04 (headless CI: GitHub Actions)
• Dependencies installed: xvfb, libfuse2, libegl1, libopengl0, libjack-jackd2-0
• MuseScore AppImages used as CLI tools

Additional information

• MuseScore 3.6.2 handles the export job as expected
• MuseScore 4 fails silently or crashes with:

  QEventLoop: Cannot be used without QApplication
  

Environment

• Ubuntu 22.04 headless
• GitHub Actions

.github\workflows\convert.yml

name: Convert MuseScore files to PDF

on:
  push:


jobs:
  convert:
    runs-on: ubuntu-22.04


    steps:
      - name: Checkout repository
        uses: actions/checkout@v3


      - name: Install dependencies (xvfb + wget + libfuse + OpenGL + JACK)
        run: |
          sudo apt-get update
          sudo apt-get install -y \
            xvfb wget libfuse2 \
            libegl1 libopengl0 libjack-jackd2-0


      - name: Download MuseScore AppImage
        run: |
          wget -q https://ftp.osuosl.org/pub/musescore-nightlies/linux/4x/nightly/MuseScore-Studio-Nightly-251280318-master-3b25461-x86_64.AppImage -O musescore.AppImage
          chmod +x musescore.AppImage


      - name: Convert .mscz/.mscx to PDF (Parts)
        run: |
          find . -name '*.mscz' | while read file; do
            name=$(basename "$file")
            name_no_ext="${name%.*}"


            echo "[
              {
                \"in\": \"$file\",
                \"out\": [
                  \"${name_no_ext}.pdf\",
                  [\"${name_no_ext}_\", \".pdf\"]
                ]
              }
            ]" > export_job.json


            echo "::group::export_job.json"
            cat export_job.json
            echo "::endgroup::"


            export QT_LOGGING_RULES="qt.qml.typeregistration=false"
            xvfb-run -a ./musescore.AppImage -j export_job.json
          done


      - name: Upload PDF files as artifacts
        uses: actions/upload-artifact@v4
        with:
          name: converted-pdfs
          path: '**/*.pdf'

Supporting files, videos and screenshots

publisher-debug-feat-export-parts.zip

What is the latest version of MuseScore Studio where this issue is present?

4.5.2

Regression

Yes, this used to work in MuseScore 3.x and now is broken

Operating system

Ubuntu 22.04 and Windows 10

Additional context

No response

Checklist

• This report follows the guidelines for reporting bugs and issues
• I have verified that this issue has not been logged before, by searching the issue tracker for similar issues
• I have attached all requested files and information to this report
• I have attempted to identify the root problem as concisely as possible, and have used minimal reproducible examples where possible