arcattackandClaude Fable 5
54b6663b4d
Full cross-pod KILL now works: instance A (host 2) shoots B's mech (host 3) dead over the network; B runs the death transition on its own screen. Verified on a 2-node one-box run (BT_MP_FORCE_DMG on A): B's mech takes ~36 remote hits of 12 and is DESTROYED, with wreck swap + explosion. ROOT CAUSE (one bug): B's own MASTER mech was INVALID. Entity::Receive(Event*) does `if(!IsValid()) event->Defer()` -- so a cross-pod-delivered TakeDamage that arrived, resolved to B's real mech, and Posted, was DEFERRED forever; the handler never ran. The reconstructed Mech::Make force-set ValidFlag only for replicants (the P6 bring-up hack for the partial MakeReady handshake); a locally-created master never got validated. FIX (one line): Mech::Make now sets ValidFlag for the master too -- the reconstructed ctor builds the mech synchronously, so it's safe. Nothing else changed: targeting, the virtual victim->Dispatch, the replicant reroute, the wire, receive, and id resolution were ALL already correct. Two prior root causes were BOTH mis-diagnoses from the WRONG messageID: Entity::TakeDamageMessageID is 18, not 21. Every earlier probe filtered msgID==21, never matched a real TakeDamage, and mis-correlated the stray 21 hits' 3:19 / classID-48 against the real 3:22 hit -- inventing (a) a "cross-TU Entity layout divergence" (disproven: offsetof identical in both TUs, sizeof 444, entityID@0x17C) and (b) a "localID corrupted on the wire". Both FALSE; the id is correct end-to-end (3:22 = B's master). - game/reconstructed/mech.cpp: validate master + replicant at Make. - game/reconstructed/mech4.cpp: BT_MP_FORCE_DMG cleaned to a concise gated 2-node cross-pod reproducer (real virtual Dispatch path). - context/multiplayer.md, reconstruction-gotchas.md: corrected root cause + the validity-defers-cross-pod gotcha. Engine diagnostics reverted to clean. Solo un-regressed (the solo enemy was already force-valid; the change only ADDS ValidFlag). btl4.exe builds; full mission loop clean. Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
139 lines
10 KiB
Markdown
139 lines
10 KiB
Markdown
---
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id: multiplayer
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title: "Multiplayer — replication, netcode, the console"
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status: provisional
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source_sections: "PROGRESS_LOG.md §7 (Phase 7), §8 (P6); docs/HARD_PROBLEMS.md (P6)"
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related_topics: [wintesla-port, combat-damage, locomotion, decomp-reference]
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key_terms: [master, replicant, EGG, dead-reckon]
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open_questions:
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- "Cross-pod combat (damage to a replicant's master); replicant gait; pod-LAN config"
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---
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# Multiplayer
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Pod-to-pod networked play. The hard infrastructure exists (WinTesla replaced DOS `NETNUB` with a
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WinSock2 TCP stack); the work is integrating + smoke-testing it for BT. Full detail:
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`docs/PROGRESS_LOG.md §7, §8`; the problem writeup: `docs/HARD_PROBLEMS.md` (P6).
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## The stack (already reconstructed)
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- WinTesla replaced `NETNUB` with a **3446-line WinSock2 TCP** reimplementation (`MUNGA_L4/L4NET.CPP`,
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`SOCK_STREAM`/ReliableMode, zero SOCK_DGRAM); the master/replicant distributed-sim core
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(InterestManager/Entity/HostManager) is complete. So MP = integrate + smoke-test that stack (gated
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on P3 locomotion + P5 entity lifecycle + subsystem WAVEs). The rumored `L4NET.CPP:1853` send-size
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bug is DEAD CODE (`#if MESSAGE_BUFFERING`==0). [T2]
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## Master / replicant model
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- **[[master]]** = a locally-simulated entity (your mech + dummies); drives itself + EMITS update records.
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- **[[replicant]]** = a peer's mech, a local proxy; DeadReckons toward the master's replicated position.
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MUST `SetValidFlag()` at creation or every message defers forever ([[reconstruction-gotchas]] §9).
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## How a session forms
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`-net <port>` = networked mode (the pod listens on <port> for a CONSOLE, boots ConsoleOnly; game mesh
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= <port>+1). Solo (no `-net`) never touches WinSock. The mission egg's `[pilots]` section IS the
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roster (`pilot=ip[:port]` + a per-address page); each pod self-identifies by local-IP+game-port,
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connects to earlier pilots, listens for later ones — a deterministic full mesh; the mission loads when
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all connect. The **CONSOLE** (operator station — ABSENT from every archive) delivers the egg as chunked
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`ReceiveEggFileMessage` packets + the LAUNCH `RunMissionMessage`; **`tools/btconsole.py` is our console
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emulator** (⚠ `NotationFile::ReadText` expects NUL-SEPARATED lines). [T2]
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## Verified milestones (one box, two instances)
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- **P6 smoke test:** two instances share a world — console egg → TCP mesh → synchronized start →
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bidirectional entity replication (each renders its own mech + the peer's REPLICANT), 0 crashes.
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- **Movement replication:** A's mech WALKS on B's screen (the replicant tracks the master to ~1.5u via
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dead-reckoning). The authentic mission-start ladder runs (CreatingMission→…→RunningMission via the
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console LAUNCH). SIX bugs fixed to get here (dead-reckoner install, replicant-motion DeadReckon,
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master emission threshold, emission gated on RunningMission, the console-must-LAUNCH fact, replicant
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validity). [T2]
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- **Wire-format bug class found+fixed:** MakeMessages replicate RAW over TCP, so string payload must be
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INLINE (`char[N]` at the binary offsets), not a `const char*` pointer (garbage cross-pod). Check
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EVERY MakeMessage for pointer payloads. [T2]
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## Debug tooling (`BT_NET_TRACE`, permanent)
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`[net-tx]/[net-rx]` (L4NET), `[net-upd]` (update lookup), `[upd-repl]`, `[ent-exec]` (state ladder).
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Per-instance: `BT_LOG=<file>` + `BT_AFFINITY=<mask>` (CPU pin). Update stream ≈ 60 Hz × 144-byte
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records per moving master. [T2]
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## Cross-pod combat step 1+2 (task #46, 2026-07-09) [T2 findings]
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**Step 1 — target ANY peer mech: DONE + verified.** A live-mech registry (`BTRegisterMech`/
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`BTDeregisterMech` from the Mech ctor/dtor, btplayer.cpp) collects every Mech — player, dummy,
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AND peer replicants. The mech4 boresight world-pick now walks `BTGetTargetCandidates` (all mechs
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≠ shooter) and picks the CLOSEST the ray strikes, retargeting the whole fire/damage block from
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the solo `gEnemyMech` to the picked `hotTarget` (missile impact + projectile validation
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generalised via `BTIsRegisteredMech`). Verified one-box: instance A correctly enumerates B's
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mech as a live `ReplicantInstance` (inst=4), 20 zones, `ownerID=3`, alive. Solo un-regressed
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(pick→damage→kill chain clean).
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**Step 2 — cross-pod damage: SOLVED + verified end-to-end (task #47, 2026-07-09).** A one-line fix
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(`Mech::Make`) yields a full cross-pod KILL: instance A (host 2) shoots B's mech (host 3) dead over
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the network, B runs the death transition (wreck swap + explosion) on its own screen. [T2]
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**THE BUG (root cause): B's own MASTER mech was INVALID, so every dispatched network message to it was
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DEFERRED forever.** `Entity::Receive(Event*)` (ENTITY.cpp:165) does `if(!IsValid()) event->Defer();
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return;`. The reconstructed `Mech::Make` (mech.cpp) force-set `ValidFlag` ONLY for replicants (the P6
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bring-up hack for the partial MakeReady/CheckLoad handshake); a locally-created **master** never got
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validated. So A→B TakeDamage arrived, resolved to B's real master mech, Posted, drained to
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`Entity::Receive` — which saw `valid=0` and Deferred it. Handler never ran → 0 damage.
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**THE FIX:** `Mech::Make` now sets `ValidFlag` for the master too (`if (mech != 0) mech->SetValidFlag();`
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— the reconstructed ctor builds the whole mech synchronously, so it's safe). NOTHING ELSE changed: the
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targeting, the virtual `victim->Dispatch`, the reroute, the wire, the receive, and the id resolution
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were all already correct. Solo un-regressed (the solo enemy was already force-valid via btplayer:839;
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the change only ADDS `ValidFlag`).
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**Verified full path** (2-node one-box, `BT_MP_FORCE_DMG` on A firing at B's replicant once/sec):
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1. A: `victim->Dispatch(&td)` (VIRTUAL — the real beam path) → `Entity::Dispatch` reads `inst=Replicant`,
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stamps `entityID=3:22` (B's master id), `if(ReplicantInstance) SendMessage(ownerID=3, EntityManagerClientID)`.
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2. Wire: `NetworkManager::Send` (L4NET.CPP:1062) → `send()` to host 3 (online).
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3. B: `ReceiveNetworkPacket` (NTTMGR.cpp:107) → `GetEntityPointer(3:22)` = `entityIndexSocket.Find`
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(HOSTMGR.h:270) → resolves to B's **master mech (classID 3001=0xBB9)** → `Post(EntityManagerEventPriority)`.
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4. B: event drains → `Entity::Receive` (now `valid=1`) → `Mech::TakeDamageMessageHandler` (mech.cpp:548)
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→ invalidZone (−1) cylinder lookup → zone damage. ~36 hits × 12 → B's mech DESTROYED + death transition.
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**Two prior mis-diagnoses corrected — both were the WRONG messageID.** `Entity::TakeDamageMessageID` is
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**18**, NOT 21 (confirmed at runtime: `td.msgID=18`, so `Simulation::NextMessageID`=3, not 6). Every
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earlier probe filtered `msgID==21`, so it NEVER matched a real
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TakeDamage — the stray `msgID=21` hits it caught were an unrelated message, and correlating their `3:19` /
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`classID 48` against the real `3:22` TakeDamage produced two phantom root causes: (a) the "cross-TU Entity
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layout divergence" (disproven separately — an `offsetof` probe showed `Entity` is IDENTICAL in both TUs:
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`sizeof=444`, `entityID@380 (0x17C)`, `ownerID@388`, `simulationFlags@32`; distinct from the REAL P5
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raw-offset stomps at `this+0x2d4..0x2f0` in `docs/HARD_PROBLEMS.md`), and (b) the "localID drops by hostID
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on the wire" claim. Both are FALSE. The id is correct end-to-end (`3:22` = B's master); nothing on the wire
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is corrupted. Lesson: when a message probe seems to see a wrong id, first confirm the numeric messageID.
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Retained gated instrument: `[mp-force]` (BT_MP_FORCE_DMG + BT_MP_LOG) — the 2-node cross-pod reproducer,
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off in solo. `[mp-hdlr]` (BT_MP_NET, mech.cpp:554) logs each applied cross-pod hit. 2-node launch recipe +
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`scratchpad/mp_test.sh`: A `-egg MP.EGG -net 1501`, B `-net 1601`, then `python tools/btconsole.py MP.EGG
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127.0.0.1:1501 127.0.0.1:1601` (MP.EGG `[pilots]` = game ports 1502/1602).
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## Remaining (P6 phase 4 / Phase 7)
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Interactive 2-window driving + the `-net`-mode aim projection / drive (A's aim ray was dead — `noRay`, and
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`BT_AUTODRIVE`/`BT_GOTO` didn't move A in `-net` mode) so a HUMAN (not just the FORCE_DMG hook) can aim +
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fire cross-pod; replicant GAIT animation (derive from replicated velocity); the pod-LAN config (real IPs,
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bare-IP pilot entries). See [[open-questions]]. [T3]
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## MP-front scout (task #45, 2026-07-09) — the P6 chain SURVIVES the combat/HUD rework [T2]
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Re-ran the one-box smoke test on the current build (world-pick targeting, weapon groups, death
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transition, HUD all landed since P6): console egg → mesh → RunningMission on BOTH instances, 174+
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×144-byte update records EACH side (msgID=6), 2 mech trees per instance, 0 crashes over ~6 min.
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**Gap map to a first playable LAN fight** (in wiring order):
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1. **Enemy selection**: the world-pick tests only `gEnemyMech` (the solo dummy, btplayer.cpp:791).
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MP: the pick must test every OTHER mech (the peer replicants) — generalize to a candidate walk
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(mech entities != viewpoint). Small.
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2. **Cross-pod damage**: dispatch TakeDamage at the REPLICANT → verify the engine reroute carries
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it to the owning master (the KB claims Dispatch reroutes; not yet exercised with our STEP-6
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handler). The master takes real zone damage + runs its own death transition (task #42 placed the
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death dispatch victim-side — MP-correct by construction).
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3. **Victim visuals on the shooter's screen**: the wreck swap gates on zone/graphic state the
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REPLICANT copy may never see (zone damage may not replicate — only pose updates confirmed).
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Check DamageZone/subsystem state in the update stream; else replicate the death as an event.
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4. **Cross-pod beam visuals**: replicant emitters don't run the local trigger sim, so the peer's
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beams never draw today. ⭐ The authentic path exists: ServiceDischarge/ContinueDischarge SEND
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**beam-keepalive messages** (`FUN_0041c350`, templates @0x511e6c/@0x511e78, emitter.cpp already
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stubs them) — decode + route those to drive replicant beam draws.
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5. **2-window driving**: input gates on window focus (alternate windows; `BT_KEY_NOFOCUS` for
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harness). DEATHS scoring should light via the existing BTPostKillScore MP branch. Respawn =
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the P5 teardown debt (deferred until needed).
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## Key Relationships
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- Base: [[wintesla-port]] (L4NET). Depends on: [[locomotion]] (update writer), [[combat-damage]]
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(entity lifecycle). Detail: `docs/HARD_PROBLEMS.md` (P6).
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