■ Summary
In InDesign 2026 (v21.x) and InDesign 2027 (v22.x), exporting a document containing Japanese vertical text (Tategumi) to HTML completely breaks the text layout. This is a critical regression bug, as the exact same document exported cleanly in InDesign 2025 (v20.x).

■ Environment
- App Versions affected: Adobe InDesign 2026 (21.0+) and InDesign 2027 (22.x)
- Last working version: Adobe InDesign 2025 (20.x)
- OS: macOS

■ Steps to Reproduce
1. Create a new document in InDesign 2026 or 2027.
2. Place both Horizontal text frames (Yokogumi) and Vertical text frames (Tategumi) with Japanese text (including Tate-chu-yoko numbers).
3. Go to File > Export > select "HTML" and export the document.
4. Open the exported "index.html" in a web browser.

■ Actual Result (See attached Image 2)
- Horizontal text (top half) exports and renders properly.
- Vertical text (bottom half) is completely broken: all characters collapse and overlap into a single line/spot at the top edge, and Tate-chu-yoko numbers / trailing characters detach, rotate, and scatter toward the bottom of the page.
- This occurs regardless of frame type (both standard Text Frames and Frame Grids are affected) or Mojikumi settings (both "No Mojikumi" and "Punctuation width half / 1-em indent" are affected).
(Note: The vertical labels next to the broken text in the screenshot were converted to outlines for reference, which is why they display normally.)

■ Expected Result (See attached Image 1)
Japanese vertical text frames and frame grids should maintain their proper vertical layout, character spacing, and Tate-chu-yoko formatting when exported to HTML, just as they did in InDesign 2025.

■ Business Impact
HTML export of vertical Japanese text is essential for Japanese publishing, e-book, and web workflows. Because this bug remains unfixed in InDesign 2027, we are forced to stay on InDesign 2025. Please prioritize fixing this regression.