diff --git a/scripts/package-source.sh b/scripts/package-source.sh
index 2e8110b..38631c7 100755
--- a/scripts/package-source.sh
+++ b/scripts/package-source.sh
@@ -26,6 +26,17 @@ Developer ID signing/notarization requires your own identity and is separate.
 BUILD
 (cd "$source_dir" && CARGO_HOME="$destination/empty-cargo-home" CARGO_TARGET_DIR="$destination/check-target" cargo check --locked --offline --workspace --all-targets)
 (cd "$source_dir" && python3 scripts/check-core.py)
-tar -czf "$destination/sized-v2.0.0-source.tar.gz" -C "$destination" sized-source
+COPYFILE_DISABLE=1 tar --no-xattrs -czf "$destination/sized-v2.0.0-source.tar.gz" -C "$destination" sized-source
+# Reject platform metadata sidecars before any publication or Linux rebuild.
+python3 - "$destination/sized-v2.0.0-source.tar.gz" <<'PY_CHECK'
+import sys, tarfile
+from pathlib import PurePosixPath
+with tarfile.open(sys.argv[1]) as archive:
+    for entry in archive:
+        if any(part.startswith('._') for part in PurePosixPath(entry.name).parts):
+            raise SystemExit(f'Unexpected AppleDouble metadata: {entry.name}')
+        if any('xattr' in key.lower() for key in entry.pax_headers):
+            raise SystemExit(f'Unexpected extended attributes: {entry.name}')
+PY_CHECK
 printf '%s\n' "$revision" > "$destination/SOURCE-REVISION.txt"
 echo "Verified offline source: $destination/sized-v2.0.0-source.tar.gz"
diff --git a/scripts/release.sh b/scripts/release.sh
index ee19eb0..70aa821 100755
--- a/scripts/release.sh
+++ b/scripts/release.sh
@@ -46,7 +46,7 @@ python3 scripts/package-notices.py "$destination" --revision "$revision"
     printf 'Unsigned host build; not a notarized Mac application.\n'
 } > "$destination/BUILD-INFO.txt"
 
-tar -czf "$destination.tar.gz" -C "$destination" .
+COPYFILE_DISABLE=1 tar --no-xattrs -czf "$destination.tar.gz" -C "$destination" .
 (
     cd "$(dirname "$destination")"
     archive="$(basename "$destination").tar.gz"