OpenSpec Change: network-plugin-session

Change ID: network-plugin-session
Package: @suaveplan/network-plugin-session (new)
Status: PROPOSED
Type: new-package
Date: 2026-04-29

Why

The tiered mesh network provides peer-to-peer connectivity, but it has no concept of logical player groupings — sessions. A session is a scope within which peers see each other, exchange state, and interact. Sessions can be nested: a parent session (free-roam open world) contains child sessions (missions, heists, races), which may contain further nested sessions (mission phases, instanced interiors). This is the pattern used by GTA V Online, Destiny, The Division, and many other multiplayer games.

Without session management, every peer in the mesh receives every message from every other peer. Sessions provide:

Visibility isolation — peers only receive state from peers in their session branch
Nested hierarchies — missions inside free-roam, phases inside missions
Session-scoped host nomination — each session elects its own host for state authority
Capacity enforcement — hard caps per session type (free-roam: 30, mission: 4, race: 8)
Graceful transitions — joining/leaving sessions without dropping mesh connection
Parent state inheritance — sub-sessions can optionally receive read-only state from parent (weather, time, world events)

What changes

ADDED: SessionPlugin class implementing NetworkPlugin.
ADDED: SessionManager — maintains the session tree, handles create/destroy/join/leave/move operations.
ADDED: Session — represents one session node in the tree: id, parentId, hostId, peers[], capacity, rules, state.
ADDED: SessionRouter — intercepts outgoing messages and filters delivery to peers in the target session scope only.
ADDED: SessionHostElection — per-session host nomination, independent of mesh Tier 0 host. A peer can be host of multiple sessions.
ADDED: SessionTransitionManager — handles join/leave/move with state snapshot transfer and forwarding tunnel.
ADDED: ParentStateBridge — optionally replicates read-only parent state into child sessions (e.g., world time, weather).
ADDED: SessionCapacityEnforcer — rejects joins when capacity exceeded; can trigger session split.
ADDED: SessionRegistry — tracks all known sessions in the mesh, their hosts, and their peer counts.
ADDED: NETWORK_SESSION_CODES — frozen error registry.

Session hierarchy model

Mesh (all connected peers)
└── Session: "freeroam-01" (capacity: 30, host: Peer-A)
    ├── Peer-A (host)
    ├── Peer-B
    ├── Peer-C
    ├── Peer-D
    └── Session: "mission-heist-01" (capacity: 4, host: Peer-B)
        ├── Peer-B (host)
        ├── Peer-C
        ├── Peer-D
        └── Session: "phase-drill" (capacity: 2, host: Peer-C)
            ├── Peer-C (host)
            └── Peer-D

Rules:

A peer can be in exactly one leaf session at a time.
A peer implicitly belongs to all ancestor sessions (for parent state bridge).
Messages sent within a session are delivered only to peers in that session or its descendants.
Messages sent "upward" (to parent) are delivered to the parent session host only.
Each session has its own host, elected independently via the same governance scoring.

Out of scope

Game-specific state replication (entities, physics, AI) → gaming packages (gaming-ecs, gaming-r3f-networking).
Matchmaking (finding which session to join) → gaming-lobby, gaming-matchmaking.
Party system (persistent friend group) → gaming-party.
Persistence (saving session state to disk) → future network-plugin-session-persistence.

Source mapping

This change derives from the session concepts in ../suaveplan/enterprise/game-server.md (§sessions) and ../suaveplan/enterprise/lobby.md, but is a new design — suaveplan has no equivalent network-layer session plugin.

Requirement	Source lines	Notes
Session management	`game-server/README.md` §Sessions	reworded; suaveplan had session stubs in game-server, not network layer
Session host	`game-server/README.md` §Sessions	reworded; host per session, not per mesh
Capacity limits	`lobby/README.md` §Capacity	reworded; per-session, not per-lobby

Requirements with no source line

Requirement	Justification
Session-scoped message routing	Defensive — prevents free-roam state flooding mission peers
Nested session hierarchies	Required for GTA V-style missions-within-free-roam
Parent state bridge	Required so mission players still see world time/weather
Per-session host election	Required so mission host can be closest to mission peers, not free-roam host
Session transition with snapshot	Required for seamless join/leave without mesh disconnect

Verification approach

src/session/session.spec-conformance.test.ts — pins create, destroy, join, leave, move.
src/router/router.spec-conformance.test.ts — pins message delivery scope, upward routing, parent bridge.
src/election/election.spec-conformance.test.ts — pins per-session host election, independent of mesh host.
src/transition/transition.spec-conformance.test.ts — pins join/leave/move with state snapshot.
src/capacity/capacity.spec-conformance.test.ts — pins capacity enforcement, rejection, split trigger.
src/registry/session-registry.spec-conformance.test.ts — pins session tree tracking, peer counts.
tests/dep-graph.test.ts — pins no direct import of webrtc or gaming packages.

Migration impact

None — additive only.

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