diff --git a/docs/plans/2026-07-29-network-transport-campaign.md b/docs/plans/2026-07-29-network-transport-campaign.md index 07ced8db..a181ee4d 100644 --- a/docs/plans/2026-07-29-network-transport-campaign.md +++ b/docs/plans/2026-07-29-network-transport-campaign.md @@ -1,6 +1,6 @@ -# Campaign N — Retail-Faithful Network Transport +# Campaign N — Retail-Faithful Network Transport -**Status: ACTIVE (approved 2026-07-29). Slices N0–N6.** +**Status: ACTIVE (approved 2026-07-29). Slices N0–N6.** acdream cannot survive a single lost UDP packet in either direction. This campaign ports retail's reliable-transport mechanism (the Sept 2013 named @@ -15,8 +15,8 @@ Read this before touching `src/AcDream.Core.Net/`. 1. **Outbound (the #260 wedge):** no sent-packet cache, no resend. ACE NAKs a client-sequence gap with `RequestRetransmit`; we parse the list and consume - it nowhere. One lost C2S datagram → ACE buffers everything after the gap - forever → all actions void, position updates void → ACE stops streaming new + it nowhere. One lost C2S datagram → ACE buffers everything after the gap + forever → all actions void, position updates void → ACE stops streaming new areas (the #256 "invisible portals") while the session stays alive on cleartext acks. Reproduced twice on Coldeve 2026-07-29 with the `ACDREAM_PROBE_NET` probe (`artifacts/coldeve-probe-20260729/`, local). @@ -25,7 +25,7 @@ Read this before touching `src/AcDream.Core.Net/`. shifts the keystream permanently; every later encrypted packet fails checksum and burns another word. Inbound silent forever. -Loopback ACE never drops packets — every historical gate was structurally +Loopback ACE never drops packets — every historical gate was structurally blind to both bugs. Slice N5's loss gate removes that blindness permanently. ## 2. The retail mechanism (port target) @@ -39,89 +39,89 @@ outbound = `RecipientData` + `ClientFlowQueue` + `SentPacketStore` (under ### 2.1 Outbound resend - Every reliable packet (fragments aboard) is cached AFTER a successful send - (`FlowQueue::TransmitNewPackets @ 0x00547A60` → `SentPacketStore:: + (`FlowQueue::TransmitNewPackets @ 0x00547A60` → `SentPacketStore:: AddSentPacket @ 0x0054AB00`), with disposable optional headers stripped first (`NetPacket::RemoveDisposableOptionalHeaders @ 0x00549510`). Under - our standalone-control design (§4) reliable packets never carry optional - headers, so the strip is a provable no-op — assert `optionalLength == 0` + our standalone-control design (§4) reliable packets never carry optional + headers, so the strip is a provable no-op — assert `optionalLength == 0` in `SentPacketStore.Add`. -- Server `RequestRetransmit` (0x1000) → merge-insert ids wrap-safe sorted +- Server `RequestRetransmit` (0x1000) → merge-insert ids wrap-safe sorted (`FlowQueue::EnqueueAcks @ 0x005488E0`); `ids[0]` doubles as an implicit cumulative ack (`RecipientData::ProcessNaks @ 0x00547010`). Ids no longer - cached → retail answers `RejectRetransmit`; we drop silently (row TS-57). + cached → retail answers `RejectRetransmit`; we drop silently (row TS-57). - Resend (`FlowQueue::TransmitAcks @ 0x005485B0` / `DequeueAck @ - 0x005472F0`): re-emit with a REBUILT 20-byte header — flags + 0x005472F0`): re-emit with a REBUILT 20-byte header — flags `Retransmission|EncryptedChecksum` (=3; |`BlobFragments` =7 with fragments), `Time` = the CURRENT interval id, `Sequence`/`DataSize` verbatim, checksum = fresh header hash + stored sealed checksum. Body bytes untouched; **the original ISAAC key is reused** (`CryptoSystem:: - EncryptData @ 0x0065FF40` takes the key as an optional in/out — null draws, + EncryptData @ 0x0065FF40` takes the key as an optional in/out — null draws, non-null reuses). Never a new keystream word. -- `AckSequence` (0x4000) inbound → wrap-safe max watermark → prune strictly +- `AckSequence` (0x4000) inbound → wrap-safe max watermark → prune strictly older (`SentPacketStore::Flush @ 0x0054ACD0`, pops from FIFO head while - `seqNum < watermark`). No timer-based resend exists — resend only on + `seqNum < watermark`). No timer-based resend exists — resend only on explicit NAK. -- Sequence allocation: `highestIDSent_` starts 1; `++`; wrap 0xFFFFFFFF → 1 +- Sequence allocation: `highestIDSent_` starts 1; `++`; wrap 0xFFFFFFFF → 1 (never 0). Unsequenced packets reuse the current watermark, cleartext, no ISAAC word. -- Pump order per frame (`FlowQueue::Empty @ 0x00548A20`): NAKs → retransmits - → new packets. +- Pump order per frame (`FlowQueue::Empty @ 0x00548A20`): NAKs → retransmits + → new packets. ### 2.2 Inbound sequencing + ISAAC discipline -**No transport reorder buffer** — packets process on arrival -(`SharedNet::ProcessPacket @ 0x00544790` → `ProcessNewSeqNum @ 0x00544690`): +**No transport reorder buffer** — packets process on arrival +(`SharedNet::ProcessPacket @ 0x00544790` → `ProcessNewSeqNum @ 0x00544690`): 1. `SeqIDSanityCheck @ 0x00543A20`: drop if seq is newer than `highestIDReceived_ + 0x7FFF` (wrap-safe). 2. Encrypted + not newer than the watermark = duplicate/late arrival: remove - from the NAK set — hit → decrypt with the **parked pre-drawn key**; - miss → drop silently at zero keystream cost. -3. Newer than the watermark → gap walk (`ProcessNewestSeqNum @ 0x00541930`): - for each missing id (skip 0) `AddNakked(id, null)` — **pre-draws one + from the NAK set — hit → decrypt with the **parked pre-drawn key**; + miss → drop silently at zero keystream cost. +3. Newer than the watermark → gap walk (`ProcessNewestSeqNum @ 0x00541930`): + for each missing id (skip 0) `AddNakked(id, null)` — **pre-draws one inbound ISAAC word per missing id, in sequence order, BEFORE the arriving packet's own key**, parking it beside the id (`ReceiverData::AddNakked @ 0x00549240`, idempotent). Cleartext packets walk to `seq+1` (they borrow an already-delivered sequence). Then watermark = seq. 4. Encrypted packets then decrypt with the parked key or the next drawn word. -5. Parse failure on a sequenced packet → re-park its consumed key +5. Parse failure on a sequenced packet → re-park its consumed key (`AddNakked(seq, &key)`), so the retransmission decodes. -6. Inbound `RejectRetransmit` (`SharedNet::HandleEmptyAck @ 0x005448F0`) → +6. Inbound `RejectRetransmit` (`SharedNet::HandleEmptyAck @ 0x005448F0`) → remove ids from the NAK set, silent abandonment. This keeps the inbound keystream aligned to SEQUENCE order, not arrival order -— the invariant the whole inbound port hangs on. +— the invariant the whole inbound port hangs on. ### 2.3 Ack/NAK sweep Per-frame per-connection sweep (`ClientNet::ProcessConnection @ 0x00545450`), mutually exclusive on ONE shared timestamp (`ReceiverData::timeStamp_`): -- NAK set non-empty → `RequestRetransmit`: ≤114 ids ascending, cleartext, +- NAK set non-empty → `RequestRetransmit`: ≤114 ids ascending, cleartext, 0.6 s gate (`SharedNet::EnqueueNaks @ 0x00543BD0`, `ReceiverData::GetNaks @ 0x005490C0`), and NO ack this sweep. -- Else → one cumulative `AckSequence` carrying `highestIDReceived_`, +- Else → one cumulative `AckSequence` carrying `highestIDReceived_`, unsequenced + cleartext, 2.0 s gate (`SharedNet::EnqueuePak @ 0x00543B10` - — the ONLY 0x4000 construction site in the binary; retail never acks + — the ONLY 0x4000 construction site in the binary; retail never acks per-packet). -### 2.4 Keepalive/time/flow (mostly deferred — §5) +### 2.4 Keepalive/time/flow (mostly deferred — §5) TimeSync (8-byte double) + EchoRequest (4-byte float) every ~3 s (`ClientFlowQueue::IncrementLocalInterval @ 0x00547F10`); inbound TimeSync adopts the server clock; Flow report sent on remote-interval advance; -inbound Flow ignored, no throttle (`WireRoomLeft` is a folded `return 1` — +inbound Flow ignored, no throttle (`WireRoomLeft` is a folded `return 1` — verified); dead link at 140 s without inbound data (self-stall guarded) with referral auto-reconnect; 0.5 s interval clock feeds `ProtoHeader::interval_` (our `PacketHeader.Time`). ### 2.5 Constants -464 max payload after the 20-byte header · 448 fragment payload · 114 NAK -list cap · +0x7FFF sanity window · 0.5 s interval tick · 2.0 s ack gate · -0.6 s NAK gate · ~3 s TimeSync/Echo · 140 s dead link · 10 s disconnect -drain · `0xBADD70DD` checksum placeholder · sequence init 1, wrap -0xFFFFFFFF→1 · 0.333 s ConnectResponse handshake resend. +464 max payload after the 20-byte header · 448 fragment payload · 114 NAK +list cap · +0x7FFF sanity window · 0.5 s interval tick · 2.0 s ack gate · +0.6 s NAK gate · ~3 s TimeSync/Echo · 140 s dead link · 10 s disconnect +drain · `0xBADD70DD` checksum placeholder · sequence init 1, wrap +0xFFFFFFFF→1 · 0.333 s ConnectResponse handshake resend. ## 3. ACE constraints (Coldeve runs ACE; references in the MAIN repo checkout) @@ -129,37 +129,37 @@ drain · `0xBADD70DD` checksum placeholder · sequence init 1, wrap |---|---|---| | NAKs client gaps at `expected+2`, 1 s limit, arrival-driven ONLY | NetworkSession.cs:351-363 | after one C2S loss two more sends must arrive before ACE NAKs; a quiet client is never NAKed | | Crypto search window 256 keys; re-key orphans permanently | CryptoSystem.cs:30-49 | NEVER re-key a resend; NEVER resend an already-accepted packet | -| Watermark advances on ANY packet with flags ≠ exactly `AckSequence` | NetworkSession.cs:474-476 | standalone unsequenced control packets other than exact-`AckSequence`/exact-`RequestRetransmit` can skip a REAL packet forever (the self-induced wedge) | +| Watermark advances on ANY packet with flags ≠ exactly `AckSequence` | NetworkSession.cs:474-476 | standalone unsequenced control packets other than exact-`AckSequence`/exact-`RequestRetransmit` can skip a REAL packet forever (the self-induced wedge) | | Honours only CLEARTEXT NAKs; encrypted NAKs silently ignored | NetworkSession.cs:283-284 | no NAK piggybacking; NAKs never refresh ACE's 60 s timeout | | Ack-only dedup exemption requires flags == `AckSequence` exactly | NetworkSession.cs:342-343 | equality check, not HasFlag | | ACE never proactively resends S2C; S2C cache prunes at 120 s | NetworkSession.cs:675-708, :251-262 | the client MUST NAK or inbound stalls; old NAKs get RejectRetransmit | | C2S fragment sequence strictly contiguous or dispatch stalls silently | NetworkSession.cs:532-543 | packet-level retransmission heals it automatically | | ACE sends TimeSync/20 s, cumulative ack/2 s, EchoResponse on request; NO disconnect/error packets ever | NetworkSession.cs:207-216, grep | every transport death is silence | | Rejects AckSequence/TimeSync/EchoRequest/Flow during AuthLoginRequest | Session.cs:101-102 | no sweep before negotiation completes | -| Inbound `Header.Time` ignored | grep | our interval field is cosmetic against ACE — safe | +| Inbound `Header.Time` ignored | grep | our interval field is cosmetic against ACE — safe | ## 4. Design -`src/AcDream.Core.Net/Transport/` — retail's split adapted to one login + one +`src/AcDream.Core.Net/Transport/` — retail's split adapted to one login + one world connection on one frame thread. `TransportClock` (injectable monotonic source + 0.5 s interval counter), `SequenceMath` (`IsNewer(a,b) => unchecked((int)(a-b)) > 0`), `SentPacketStore` (FIFO of rented wire buffers), `OutboundFlowQueue` (outbound ISAAC, HighestIdSent, fragment seq, pending resends, NAK/ack consumption), `InboundSequenceTracker` (inbound ISAAC, -HighestIdReceived, NAK set `SortedDictionary` seq→parked key), +HighestIdReceived, NAK set `SortedDictionary` seq→parked key), `AckNakScheduler` (ONE shared timestamp; per sweep NAK xor ack), `ReliableTransport` (composition + `Sweep()`), `TransportStats` (unconditional counters; printing probe-gated). Cache entry: `{ Sequence, rented Buffer (header+body), BodyLength, -SealedChecksum (= payloadHash ^ isaacKey — retail `NetPacket::checksum_`), -IsaacKey, HasFragments }`. Resend rewrites ONLY the header per §2.1; +SealedChecksum (= payloadHash ^ isaacKey — retail `NetPacket::checksum_`), +IsaacKey, HasFragments }`. Resend rewrites ONLY the header per §2.1; `PacketCodec.FinalizeInPlace` gains an overload returning `(isaacKeyUsed, sealedChecksum)`; the old signature forwards. -Inbound: codec splits pure-parse (`TryParseBorrowed` — no keystream) from +Inbound: codec splits pure-parse (`TryParseBorrowed` — no keystream) from `VerifyChecksum(header, headerHash, payloadHash, uint? isaacKey)`; the -tracker owns every key decision (retail's own factoring — `EncryptData`'s +tracker owns every key decision (retail's own factoring — `EncryptData`'s optional key parameter). `TryDecodeBorrowed(datagram, IsaacRandom?)` is deleted; owned `TryDecode` stays (test-only). @@ -173,21 +173,21 @@ unbounded like retail (ACE acks every 2 s; steady state is tens of entries); ## 5. Scope deferrals (divergence-register rows, filed in-slice) -- **TS-57** no outbound RejectRetransmit — ACE no-ops it; the standalone - unsequenced form trips the watermark hole (§3 row 3). -- **AP-125** standalone control packets only, no `CoalesceData` piggyback — +- **TS-57** no outbound RejectRetransmit — ACE no-ops it; the standalone + unsequenced form trips the watermark hole (§3 row 3). +- **AP-125** standalone control packets only, no `CoalesceData` piggyback — piggybacked NAKs become encrypted, which ACE ignores. -- **TS-58** no TimeSync/EchoRequest keepalive — standalone-unsafe against +- **TS-58** no TimeSync/EchoRequest keepalive — standalone-unsafe against the watermark hole; our 2 s ack already refreshes ACE's 60 s timeout. -- **TS-59** no Flow report — ACE parses and has no handler. -- **AD-49** blob-layer ephemeral ordering stamps not ported — provably a +- **TS-59** no Flow report — ACE parses and has no handler. +- **AD-49** blob-layer ephemeral ordering stamps not ported — provably a no-op against ACE (fragment `Id` is constant 0x80000000 and the stamp table keys on ACE's per-message-unique fragment sequence, so `FragIsObsoleteEmphemeral @ 0x0054A450` can never fire). -- **TS-60** no 140 s dead-link/referral auto-reconnect — LinkStatus exposes +- **TS-60** no 140 s dead-link/referral auto-reconnect — LinkStatus exposes the input; reconnect is Runtime's, its own campaign. - **TS-61** UDP send-failure burns the sequence+key (retail retries from the - queue head) — effectively unreachable. + queue head) — effectively unreachable. - **AP-126** one monotonic clock for all gates (retail's cur/local split immaterial to the gates we port). - Multi-fragment outbound (>448 B) stays unimplemented (nothing sends >448; @@ -205,7 +205,7 @@ unbounded like retail (ACE acks every 2 s; steady state is tens of entries); | N5 | Observability + LossyTransportDecorator + connected loss gate | M | partly | Opus | unit + loss gate | | N6 | Optional: ConnectResponse 0.333 s retransmit; assembler TTL | S | yes | Opus | unit + local ACE | -N1–N5 all touch `WorldSession.cs`: strictly sequential, ONE agent at a time. +N1–N5 all touch `WorldSession.cs`: strictly sequential, ONE agent at a time. Implementers Sonnet; a redo escalates to Opus; every diff reviewed by the Review-column model before commit. Key per-slice test specs are in the approved plan (`~/.claude/plans/mac-os-is-not-robust-sphinx.md`) and travel @@ -213,22 +213,22 @@ verbatim in each implementer prompt. ## 7. Landmines (verbatim in every implementer prompt) -1. Resends are NOT byte-identical — flags gain `Retransmission`, `Time` +1. Resends are NOT byte-identical — flags gain `Retransmission`, `Time` advances, the header hash MUST be recomputed; checksum = new header hash + stored sealed checksum. A verbatim resend fails ACE's CRC silently. -2. Never draw a new ISAAC word on a resend — one re-key permanently orphans +2. Never draw a new ISAAC word on a resend — one re-key permanently orphans a key in ACE's 256-entry window. -3. Never resend unrequested — a duplicate of an accepted packet burns up to +3. Never resend unrequested — a duplicate of an accepted packet burns up to the whole window. 4. The inbound gap-walk draws parked keys BEFORE the arriving packet's own - key, in sequence order — reversed, the stream is off by the gap size + key, in sequence order — reversed, the stream is off by the gap size forever. 5. Ack flags are an EQUALITY check (`Flags == AckSequence`), never HasFlag. 6. NAKs are cleartext (`Flags == RequestRetransmit` exactly) or ACE ignores them; NAKs do not refresh ACE's timeout. -7. The 0.6 s NAK gate and 2.0 s ack gate share ONE timestamp — a NAK delays +7. The 0.6 s NAK gate and 2.0 s ack gate share ONE timestamp — a NAK delays the next ack and vice versa; never both in one sweep. -8. The sweep must also run inside the blocking handshake pump loops — the +8. The sweep must also run inside the blocking handshake pump loops — the EnterWorld CreateObject flood precedes the first `Tick()`. 9. ACE/holtburger reference sources live in the MAIN repo checkout (`C:\Users\erikn\source\repos\acdream\references\`), not in worktrees. @@ -238,10 +238,10 @@ verbatim in each implementer prompt. 1. Per slice: `dotnet build` + full `dotnet test -c Release` + slice gate + one commit (retail symbol+address citations) + model review + revert SHA recorded here. -2. N1–N5: `tools/run-connected-world-lifecycle-gate.ps1` vs local ACE; +2. N1–N5: `tools/run-connected-world-lifecycle-gate.ps1` vs local ACE; N2/N3 add the canonical nine-stop route. 3. From N4: `tools/run-connected-loss-gate.ps1` at `ACDREAM_NET_DROP_PCT=2` - vs local ACE — passes only with NON-ZERO resend/NAK counters. + vs local ACE — passes only with NON-ZERO resend/NAK counters. 4. Final: one user Coldeve session past the 15-minute wedge horizon with portal churn, after N5. `[net-tick] nak-in/s` becomes the first direct measure of real C2S loss the project has had. @@ -251,10 +251,10 @@ verbatim in each implementer prompt. | Slice | Status | Commit | Notes | |---|---|---|---| -| N0 | complete | `7e9134b4` + `e3958610` | ACE-behaviour double + virtual clock + lossy link; the review fix-up added the `Session.CheckState` inbound gate, faithful `SendBundle` coalescing/splitting, two-phase termination, an ACE-loose C2S fragment parse, and ACE's MessageBuffer edge cases. 687 Core.Net tests green. N1 folded in the re-review's `ProcessFragment` two-branch split (existing-buffer checks Complete; new-buffer parks without checking — the zero-count buffer stays parked). | -| 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 | SHA recorded at N3 kickoff | 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 | pending | — | | -| N4 | pending | — | | -| N5 | pending | — | | -| N6 | pending | — | | +| N0 | complete | `7e9134b4` + `e3958610` | ACE-behaviour double + virtual clock + lossy link; the review fix-up added the `Session.CheckState` inbound gate, faithful `SendBundle` coalescing/splitting, two-phase termination, an ACE-loose C2S fragment parse, and ACE's MessageBuffer edge cases. 687 Core.Net tests green. N1 folded in the re-review's `ProcessFragment` two-branch split (existing-buffer checks Complete; new-buffer parks without checking — the zero-count buffer stays parked). | +| 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 | pending | — | | +| N4 | pending | — | | +| N5 | pending | — | | +| N6 | pending | — | |