The stamp functions (Rust refuse_unread_format, TS refuseUnreadFormat) are the single owner of the stamp rule, accept v1 and v3, and are called only from the one reader every whole-store write runs under the lock. The fix's header peek (TS refuseUnreadStoreBytes, peekHeader) is deleted. Its tests that v3 is refused and that a stampless file is healed are dropped; the reversal is a Breaking line in the Rust and TS CHANGELOGs. The 0xff-after-stamp test now runs over v1 and v3.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>