docs(net): N4 accepted - Opus review PASS; AP-125 filed; F1/F5 fixed

The N4 review confirmed the draw-order reclaim design (invariant attacked
from five angles, held) and NAK fidelity down to the decomp''s x87
comparison masks. This acceptance commit settles the two process debts it
found: AP-125 (standalone control packets vs retail''s CoalesceData
piggyback - the ACE-safety divergence that has shipped since N3''s ack and
N4''s NAK) now has its register row; the false rounding-bug justification
in AckNakScheduler (0.6 x 1e7 rounds UP under IEEE-754, truncation never
lost a tick) is rewritten as the defensive hardening it actually is; and
Admission.Process''s defaulted draw-ordinal is now ulong.MaxValue so an
accidental cleartext repark can never head a bubble-shift chain. Core.Net
737/737 green.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/plans/2026-07-29-network-transport-campaign.md

@@ -255,6 +255,6 @@ verbatim in each implementer prompt.
 | N1 | complete | `43e60a69` | Outbound sent-packet cache + resend on NAK (`Transport/`: `TransportClock`, `SequenceMath`, `SentPacketStore`, `OutboundFlowQueue`, `ReliableTransport`, `TransportStats`); `PacketCodec.FinalizeInPlace` sealed-checksum overload; `WorldSession` sweep in Tick + both handshake pump loops; TS-57 filed, TS-27 narrowed to inbound-only. **Fable review PASS.** Advisories: fresh sends keep `Time=0` (byte-identical wire; retail stamps the interval on every packet and ACE ignores the field — N3 folds the retail stamp in with the cadence work); the stale-NAK single-redundant-resend window is shared with retail (pending prunes at flush, after transmit — same frame order as `RecipientData::UseTime`). |
 | N2 | complete | `46d209d0` — **Fable review PASS** (tracker/codec-split/admission verified pre-commit against retail rules; gates lifecycle+nine-stop both PASS) | Inbound sequence-aligned ISAAC + NAK set (`Transport/InboundSequenceTracker`: watermark, sanity window, duplicate/parked-key path, sequence-ordered gap-walk pre-draw, verify-failure re-park, RejectRetransmit abandonment — `ProcessNewSeqNum @ 0x00544690`, `ProcessNewestSeqNum @ 0x00541930`, `SeqIDSanityCheck @ 0x00543A20`, `AddNakked @ 0x00549240`, `HandleEmptyAck @ 0x005448F0`); `PacketCodec` split into keystream-free `TryParseBorrowed` + `VerifyChecksum` (`TryDecodeBorrowed` deleted); `RejectRetransmit` ids exposed on both optional-header decoders; `ReliableTransport` now owns both keystreams; stats gained `InboundDupsDropped`/`InboundSanityDrops`/`ChecksumFailures`/`KeysParked`. Watermark init 1 is the AD-50 ACE adaptation (retail zero-init vs ACE's re-prime dance — first encrypted S2C is sequence 2; holtburger api.rs:30 agrees); pinned by the clean-lifecycle conformance test (zero NAKs, min encrypted S2C sequence == 2). 716 Core.Net tests green. **N3/N4 handoff note:** the interim per-packet reflex ack acks the ARRIVING sequence even while a gap is parked, so ACE prunes the lost id from its S2C cache (`AcknowledgeSequence` strictly-below) before N4 can NAK it — message-level recovery of a real loss needs N3's retail NAK-xor-ack sweep (§2.3's mutual exclusivity is load-bearing). Also noted for N4: ACE's `RejectRetransmit` consumes a fresh CLEARTEXT sequence via FlushPackets (no keystream word), so the client's gap walk parks a word for an id that never had one server-side — a real retail-vs-ACE incompatibility to resolve in N4's design (retail never assigns new sequences to cleartext). |
 | N3 | complete | `0265cc42` — Opus review PASS (advisories folded into N4: transitional-state wording, SharedInit citation, pump-order wording, control-packet Time/Iteration rule, stale budget-break comment) | AckNakScheduler + 2.0 s cumulative ack (`Transport/AckNakScheduler`): ONE shared timestamp (`ReceiverData::timeStamp_` @ +0x10) arbitrating NAK-xor-ack per sweep (`ClientNet::ProcessConnection @ 0x00545450`); the ack is one cleartext exact-flags `AckSequence` carrying the tracker's `highestIDReceived_` behind the >= 2.0 s gate (`SharedNet::EnqueuePak @ 0x00543B10` — the binary's only 0x4000 construction site), armed at connection birth (`ReceiverData::Init @ 0x00548EF0`). The Phase 4.9 per-packet reflex ack and `WorldSession.SendAck` are DELETED; the `[net-tick]` acks/s probe now reads `Stats.AcksSent`. Sweep order per `FlowQueue::Empty @ 0x00548A20`: interval clock, NAK/ack arbitration, pending resends, prune. **N3 transitional state (closed by N4):** a non-empty NAK set suppressed the ack and emitted NOTHING — the exposure was real even on loopback, just low-probability: one receive-buffer drop parks an id, every later sweep takes the silent NAK branch, acks stop (witness: `[net-tick] acks/s=0`), and ACE disconnects the quiet session at its 60 s timeout. N4 completed the branch. **N1 advisory retired (fold-in):** fresh reliable sends now stamp `Header.Time` = the current interval id (`FlowQueue::TransmitNewPackets @ 0x00547A60`, header build at 0x00547A84); ACE ignores inbound `Header.Time`, so the wire is unaffected. New `WorldSession.TransportClockSource` seam drives the gate on virtual time. 723 Core.Net tests green (keepalive property proven: a quiet session's 2 s acks refresh ACE's 60 s deadline across a 120 s virtual horizon; storm collapse: a 50-packet flood → ONE ack; the model accepts the reused-sequence ack without advancing its watermark). Connected lifecycle + canonical nine-stop gates PASS. |
-| N4 | complete | SHA recorded at N5 kickoff | Client NAK emission + RejectRetransmit consumption. `AckNakScheduler` completes the NAK branch: one cleartext exact-flags `RequestRetransmit` per sweep behind the STRICT 0.6 s gate on the ONE shared timestamp (`SharedNet::EnqueueNaks @ 0x00543BD0` — the 0x41-mask x87 test at 0x00543C03 proceeds only on strictly-greater, contrast the ack's >=), body u32 count + ids ascending capped at 114 (`ReceiverData::GetNaks @ 0x005490C0`, cap 0x72), borrowed sequence, never an ack in a NAK sweep. Control-header rule decided for BOTH emissions: `Time` = interval id, `Iteration` = session iteration, per the shared retail header build (`FlowQueue::TransmitNewPackets @ 0x00547A60` @ 0x00547A84); ACE reads neither. THE design piece: the AD-51 reclaimed-word pool in `InboundSequenceTracker` closes the ACE cleartext-reject keystream hazard the N2 ledger row recorded — ACE's `RejectRetransmit` consumes a fresh cleartext sequence with NO keystream word, so the gap walk mis-parks a word for it and the whole inbound stream runs one word ahead. On a VALIDATED cleartext reject (`WorldSession` calls `OnCleartextRejectSequence` post-checksum), the tracker removes the mis-park, bubble-shifts every later-drawn parked word down one position (per-word draw ordinals; ascending id ⇔ ascending draw order), and pools the excess for the next fresh draws, consumed lowest-draw-order-first — exact for any number of interleaved rejects in any arrival order (a plain FIFO is NOT: reject-after-higher-arrival crosses the parked chain, and dual out-of-order rejects pool out of draw order — both pinned by tests). Reject BODY ids keep N2's discard (word-bearing server-side, consumed-in-place). N3 advisories all folded: honest transitional wording (above), `ReceiverData::SharedInit @ 0x00548EF0` (from `Init @ 0x00548FA0`) citation, `FlowQueue::Empty` pump-order comment (TransmitNaks → TransmitAcks → TransmitNewPackets, interval increment LAST @ 0x00548A9D; our clock-first order is cosmetic vs ACE), the Time/Iteration rule, and the stale `WorldSession` budget-break comment. Gate arithmetic hardened: gate ticks now round (0.6 has no exact double; truncation opened the strict gate AT the boundary). 737 Core.Net tests green, including: strict-gate boundary, shared-timestamp both directions, NAK-suppresses-ack, full wire-shape + 114-cap pins, model-served retransmission round trip, five tracker reclaim proofs, the 130-s virtual prune → fresh-sequence reject system test (victim abandoned, later traffic decodes, pool drains to zero), 10 s long-loss (NAKs on the gate cadence, zero acks, heal inside the window), and the capstone soak: 2% seeded bidirectional loss × 10,000 messages → zero message loss both ways, ACE crypto headroom 256 at convergence with a ≥250 no-erosion floor mid-flight, NAK set / reclaim pool / pending resends / ACE out-of-order buffer all zero, cache at the single watermark entry (retail Flush prunes STRICTLY below the ack). Soak notes: ACE never NAKs a quiet client (§3 row 1), so convergence keeps a C2S trickle flowing — a real idle-client tail loss heals only on the next action, an ACE constraint outside N4's scope. |
+| N4 | complete | `852a59e3` — **Opus review PASS** (reclaim invariant attacked from five angles, held; NAK fidelity verified to the x87 masks; AP-125 filed + F1 false-arithmetic wording + F5 ordinal sentinel fixed in the acceptance commit; F3 Iteration-on-fresh-sends folds into N5) | Client NAK emission + RejectRetransmit consumption. `AckNakScheduler` completes the NAK branch: one cleartext exact-flags `RequestRetransmit` per sweep behind the STRICT 0.6 s gate on the ONE shared timestamp (`SharedNet::EnqueueNaks @ 0x00543BD0` — the 0x41-mask x87 test at 0x00543C03 proceeds only on strictly-greater, contrast the ack's >=), body u32 count + ids ascending capped at 114 (`ReceiverData::GetNaks @ 0x005490C0`, cap 0x72), borrowed sequence, never an ack in a NAK sweep. Control-header rule decided for BOTH emissions: `Time` = interval id, `Iteration` = session iteration, per the shared retail header build (`FlowQueue::TransmitNewPackets @ 0x00547A60` @ 0x00547A84); ACE reads neither. THE design piece: the AD-51 reclaimed-word pool in `InboundSequenceTracker` closes the ACE cleartext-reject keystream hazard the N2 ledger row recorded — ACE's `RejectRetransmit` consumes a fresh cleartext sequence with NO keystream word, so the gap walk mis-parks a word for it and the whole inbound stream runs one word ahead. On a VALIDATED cleartext reject (`WorldSession` calls `OnCleartextRejectSequence` post-checksum), the tracker removes the mis-park, bubble-shifts every later-drawn parked word down one position (per-word draw ordinals; ascending id ⇔ ascending draw order), and pools the excess for the next fresh draws, consumed lowest-draw-order-first — exact for any number of interleaved rejects in any arrival order (a plain FIFO is NOT: reject-after-higher-arrival crosses the parked chain, and dual out-of-order rejects pool out of draw order — both pinned by tests). Reject BODY ids keep N2's discard (word-bearing server-side, consumed-in-place). N3 advisories all folded: honest transitional wording (above), `ReceiverData::SharedInit @ 0x00548EF0` (from `Init @ 0x00548FA0`) citation, `FlowQueue::Empty` pump-order comment (TransmitNaks → TransmitAcks → TransmitNewPackets, interval increment LAST @ 0x00548A9D; our clock-first order is cosmetic vs ACE), the Time/Iteration rule, and the stale `WorldSession` budget-break comment. Gate arithmetic hardened: gate ticks now round (0.6 has no exact double; truncation opened the strict gate AT the boundary). 737 Core.Net tests green, including: strict-gate boundary, shared-timestamp both directions, NAK-suppresses-ack, full wire-shape + 114-cap pins, model-served retransmission round trip, five tracker reclaim proofs, the 130-s virtual prune → fresh-sequence reject system test (victim abandoned, later traffic decodes, pool drains to zero), 10 s long-loss (NAKs on the gate cadence, zero acks, heal inside the window), and the capstone soak: 2% seeded bidirectional loss × 10,000 messages → zero message loss both ways, ACE crypto headroom 256 at convergence with a ≥250 no-erosion floor mid-flight, NAK set / reclaim pool / pending resends / ACE out-of-order buffer all zero, cache at the single watermark entry (retail Flush prunes STRICTLY below the ack). Soak notes: ACE never NAKs a quiet client (§3 row 1), so convergence keeps a C2S trickle flowing — a real idle-client tail loss heals only on the next action, an ACE constraint outside N4's scope. |
 | N5 | pending | — | |
 | N6 | pending | — | |