77c99cc230
In PvP a BattleSession subscribes to both participants' FrameEmitted, and each RealParticipant raises it from its own WebSocket read loop -- two threads. The dispatch path (ComputeFrames + the relay PushAsync calls) mutates shared, non-thread-safe state: the BattleSessionState dictionaries (deck maps, post-swap hands, idx->cardId reveal map). Concurrent frames from both players could corrupt those dictionaries (InvalidOperationException / torn playSeq / wrong card identity). Add a per-session SemaphoreSlim _dispatchGate around the whole HandleFrameAsync so both read loops funnel through one critical section. ComputeFrames stays lock-free (the direct-call test seam is single-threaded). Analysis during the fix showed each OutboundSequencer is single-writer-per-instance in steady state (A's loop only writes B's Outbound and vice-versa), so the live race is the shared BattleSessionState, which the gate fully serializes. TDD: BattleSessionDispatchConcurrencyTests drives both participants to AfterReady, then fires TurnStart from both at once; the target PushAsync records peak in-flight dispatches. Red (MaxConcurrent=2) before the gate, green (1) after. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
SVSim.BattleNode
Socket.IO node-server emulation for in-battle real-time traffic — the second of prod's 4-server
topology. Handles Matched / BattleStart / Deal / per-action PlayActions / Echo /
TurnEnd between a client and a server-side opponent, for TK2 PvP and AI rank battles.
Documentation lives in the outer repo
This project's canonical reference is a single hub doc in the outer SVSim repo (this directory is an inner git repo, so the doc isn't tracked alongside the code):
→ docs/battle-node.md (from the SVSim root) — architecture, the dispatch matrix by battle
type, connect handshake + crypto, BattleFinish wire-result semantics, SIO/EIO event coverage,
reliability (pubSeq/playSeq/Gungnir), wire-format gotchas, where-to-extend, the manual smoke
walkthrough, and the consolidated open-items list.
Relative path from here: ../../../docs/battle-node.md.
Detailed per-URI wire shapes are in docs/api-spec/in-battle/; the hub links into them.
Keep docs/battle-node.md updated in the same change whenever you alter node behavior.