pptx-template-clean-rebuild

Blank output usually means duplicate slide parts in the zip or duplicate slide references in presentation.xml.rels, caused by clearing a template's slides without removing their parts. LibreOffice tolerates this, but PowerPoint's strict parser rejects the package.

Open the .pptx as a zip, keep only the last-written entry for each duplicated filename, and rewrite the archive. Then rebuild presentation.xml.rels so each slide has one unique relationship ID referenced by sldIdLst.

Partial blanking happens when newly assigned slide rIds collide with non-slide relationships like notesMaster or presProps that occupy high rId numbers. Assign slide rIds starting above the maximum non-slide relationship ID to avoid collisions.

No. LibreOffice is lenient with malformed packages, so a file can render there while PowerPoint and strict preview engines show it as blank. Treat LibreOffice-normal plus PowerPoint-blank as a sign of package structure problems, not data loss.

Run the deduplication and rels rebuild as a post-processing step immediately after prs.save(), wrapped in a finalize function. This guarantees every generated file from a slide-containing template is clean without manual intervention.