Superseded packet: a reliable-sequenced packet that arrives after a newer one
delivers no frame, yet is acknowledged and never resent, so its write went
unanswered. The test (red first: only "new" was refused, "old" got nothing)
showed the drop happens in the session below frame decoding, but an unfragmented
packet carries its whole frame, so the server can read the id from the packet
payload. Chosen: refuse it from the packet payload. A superseded fragment of a
larger write has no readable id in the packet, so write-receipt.md now says that
write may go unanswered and the client's unconfirmed outcome covers it.
Ordering: frame.sequence <= packet.sequence is replaced by sequence_at_or_before,
serial arithmetic modulo 2^32. Deviation from the brief: cultnet-rs'
at_or_before carries a 4096-sequence receive window made for duplicate detection;
a frame's first fragment may lie further back than that, so reusing it would
leave such a sequenced write unrefused and applied. The new test pins that, and a
hand mutant with the window fails it. A wrapped sequence cannot reach this
compare through the session today (it is judged a duplicate), so the unit test
pins the helper, not an end-to-end wrap.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>
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