diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 4b06ea1..c86ed05 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -76,18 +76,69 @@ jobs:
           path: dist/PDFApps-Linux.tar.gz
 
       # ── macOS ───────────────────────────────────────────────────
+      - name: Free macOS disk space
+        if: runner.os == 'macOS'
+        # macos-latest ships with Xcode (~16 GB) which our pure-Python
+        # build doesn't use. Removing it plus dropping APFS local
+        # snapshots frees enough disk for hdiutil to create the DMG.
+        # We keep CommandLineTools because PyInstaller calls
+        # lipo / codesign / otool to slice and re-sign Mach-O binaries
+        # — without those, the build dies with "lipo command ...
+        # failed with error code 1".
+        run: |
+          echo "── before cleanup ──"
+          df -h /
+          sudo rm -rf /Applications/Xcode*.app
+          # Default xcode-select path points at the (now gone) Xcode
+          # bundle; redirect to CommandLineTools so /usr/bin/lipo and
+          # friends keep resolving.
+          sudo xcode-select -s /Library/Developer/CommandLineTools || true
+          # Without this, the bytes freed by `rm -rf Xcode` are still
+          # reserved by Time Machine local snapshots and df doesn't
+          # actually drop.
+          sudo tmutil deletelocalsnapshots / || true
+          echo "── after cleanup ──"
+          df -h /
+
       - name: Build (macOS)
         if: runner.os == 'macOS'
         run: |
+          echo "── before PyInstaller ──"
+          df -h
           python -m PyInstaller --noconfirm pdfapps.spec
-          # Create DMG with the .app bundle and an Applications shortcut
+          echo "── after PyInstaller ──"
+          df -h
+          du -sh dist/PDFApps.app
+          # PyInstaller intermediates (~3-7 GB in build/ + the
+          # bootloader cache) and the loose Unix exe under dist/ are
+          # not needed for the DMG — only dist/PDFApps.app is.
+          rm -rf build/
+          rm -rf "$HOME/Library/Application Support/pyinstaller"
+          rm -f dist/PDFApps
+          # Create DMG with the .app bundle and an Applications
+          # shortcut. `mv` (not cp -R) — we don't need to keep the
+          # source .app after the DMG is built.
           mkdir -p dist/dmg
-          cp -R dist/PDFApps.app dist/dmg/
+          mv dist/PDFApps.app dist/dmg/
           ln -s /Applications dist/dmg/Applications
+          du -sh dist/dmg
+          # The previous `hdiutil create -srcfolder` (no -size)
+          # auto-estimated the intermediate sparse image too tight and
+          # died with "No space left on device" while *copying into
+          # the new DMG* — i.e. the runner had 83 GB free, but the
+          # mounted image at /Volumes/PDFApps/ ran out of bytes mid-
+          # copy. The .app has thousands of tiny files (Qt
+          # frameworks, qtawesome fonts, etc.) so HFS+ slack space
+          # blows past the auto-estimate. Force the intermediate to
+          # 1 GB; UDZO compression makes the final .dmg much smaller.
           hdiutil create -volname "PDFApps" \
             -srcfolder dist/dmg \
             -ov -format UDZO \
+            -size 1g \
             dist/PDFApps-macOS.dmg
+          echo "── after DMG ──"
+          df -h
+          ls -lh dist/PDFApps-macOS.dmg
 
       - name: Upload (macOS)
         if: runner.os == 'macOS'