You'll notice
Useful2 Signal2
Two published artifact pages parsed at once can no longer corrupt each other's validation.
What's wrong with this entry?
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What
The parser that decides what markup a published artifact page may contain now builds its matching state fresh per call, closing a class of bug where two parses running together could corrupt each other's position. What is accepted is unchanged: a doctype, the same base href shape, utf-8 charset only, and the expected root mount element.
Evidence
<!doctype[ \t\n\f\r]+html[ \t\n\f\r]*>
Strings lifted out of the shipped bundle, so the claim above can be checked against them.