Controlled Document PDF preview fails with embedded images using platform:// URLs

Summary

Printing a Controlled Document containing embedded images produces a PDF object, but Huly displays Failed to preview and the generated file cannot be downloaded.

Regular Huly Documents containing embedded images print correctly. The issue appears specific to documents:class:ControlledDocument.

Environment

• Deployment: Huly self-hosted
• Huly version: v0.7.426
• Print image: hardcoreeng/print:v0.7.426
• Browser: Chrome 151 on Windows
• Document class: documents:class:ControlledDocument

The print service is configured with FRONT_URL, ACCOUNTS_URL, STORAGE_CONFIG, and PRINT_URL according to the self-hosting documentation.

Steps to reproduce

1. Create or open a Controlled Document.
2. Insert an image into its content.
3. Select the PDF print/export action.
4. Wait for PDF generation.
5. Attempt to preview or download the generated PDF.

Expected behavior

The Controlled Document should be exported to a downloadable PDF containing its embedded images, as happens with regular Huly Documents.

Actual behavior

• The print endpoint returns HTTP 200.
• Huly displays Failed to preview.
• The generated PDF cannot be downloaded.
• The print service reports failed requests for embedded images.

Relevant log

requestfailed
errorText: net::ERR_UNKNOWN_URL_SCHEME
url: platform://platform/files/workspace/?file=<redacted-file-id>

The same image is available during normal document viewing through the /files/... HTTP endpoint.

Additional observations

• Controlled Documents without embedded images can be printed.
• Regular Huly Documents with embedded images can be printed.
• The affected images were copied from another Huly document.
• The images exist in Huly storage and display normally in the Controlled Document.
• No guest tokens, authentication errors, storage errors, or HTTP 5xx responses were observed.

Suspected cause

The guest rendering path used to print a Controlled Document leaves embedded image sources in Huly's internal format:

platform://platform/files/workspace/?file=<file-id>

Headless Chromium does not support the platform:// scheme.

The Controlled Document guest renderer may need to resolve these references to authenticated HTTP(S) /files/... URLs before Puppeteer calls page.pdf().

Possible fix

Resolve internal file references in the Controlled Document guest renderer, or replace platform://platform/files/... image sources with guest-accessible HTTP(S) URLs before PDF rendering.

Security note

All workspace IDs, file IDs, document content, domains, and guest tokens have been redacted.