Android split join proof can expose a structured DOM enter backspace gap

What happened

The first direct Android split/join proof row was supposed to be a transport question:

• collapse selection inside the bold middle leaf
• press Enter twice
• press Backspace twice
• expect the original paragraph text to come back

It failed on Android Appium. That alone could have been transport noise.

But the same sequence also failed on desktop Chromium with direct Playwright keyboard input after the same DOM-owned selection setup.

So the useful read is:

• this is not only an Android transport problem
• it exposes a broader structured DOM commit gap in the current stack

Failure shape

Instead of returning to the original paragraph:

• One before two middle three after four

the row collapses down to:

• One before two middle

That means the suffix after the split/join sequence is getting dropped.

Why this matters

This is exactly the kind of legacy Android/manual row that can reveal a deeper runtime weakness:

• browser-owned selection
• structured text with marks
• Enter/backspace structural churn
• current DOM commit path not owning structure changes robustly enough

Reusable rule

When an Android direct proof row goes red:

1. rerun the same semantic sequence on desktop Chromium
2. if desktop also fails, reclassify immediately from transport-only suspicion to product-bug candidate
3. only then decide whether Android-specific transport work is still the main queue