# Multiplayer — next work

Short, current checklist for online multiplayer. Historical design decisions,
implementation evidence, and completed work stay in
[`multiplayer-todo.md`](multiplayer-todo.md).

## Release blockers

- [ ] **Phase 4 playtest:** a human playtest at roughly 100 ms RTT. Confirm
  that ship and ball interaction feel local and contact corrections feel like
  bumps rather than glitches.
- [ ] **Phase 5 session:** complete a real 3v3 match with a mid-match
  disconnect and late joiner.
- [ ] **Phase 6 external check:** run the exported Docker server and clients
  from separate machines over the internet, then play a full match. Keep this
  controlled-only until Steam identity is complete.

## Phase 7 — Steam, identity, discovery

- [ ] Obtain the pinned GodotSteam client/server builds and Steamworks SDK
  access described in [`STEAM.md`](STEAM.md).
- [ ] Run `make verify-steam-templates` with the custom executables and fix
  any custom-template failures.
- [ ] Validate a two-account Steam SDR host/join using the existing explicit
  `NetworkManager` Steam transport. ENet direct-IP must keep passing its smoke
  test.
- [ ] Build the Steam server browser: internet, LAN, favourites, and history.
- [ ] Add Steam auth tickets, verified Steam identity in the roster, and a
  persistent ban list. This fixes the slot-reclaim security issue below.

## Phase 8 — casual and ranked matchmaking (1.0 launch blocker)

Design and reasoning: [`docs/MATCHMAKING.md`](docs/MATCHMAKING.md). This is a
different server model from the community-server one that exists today —
players queue, a matchmaker groups them, and a server is allocated per match.
Phase 7's Steam auth tickets are a hard prerequisite: a rating attached to a
spoofable identity is worse than no rating.

- [ ] Decide the rating algorithm (Glicko-2 recommended over Elo for a small
  launch population) and how a team result distributes across individuals.
- [ ] Choose the backend language and hosting, and cost out allocated servers
  per match at expected population.
- [ ] Stand up the backend: Steam auth ticket validation via the Steamworks
  Web API, queue, rating store, server allocator.
- [ ] Add an assigned-roster server mode so only matched SteamIDs may claim a
  slot, replacing the first-come model.
- [ ] Add server-authoritative match result reporting to the backend over a
  channel a client cannot forge.
- [ ] Client queue UI: playlist select, estimated wait, accept/decline,
  connect-on-assignment, post-match rating delta.
- [ ] Casual and ranked playlist rulesets (backfill, bots, abandon penalties,
  arena restriction — see the comparison table in the design doc).

Server orchestration (same phase — the servers must autoscale and bill only
for the duration of a match):

- [ ] Choose the orchestrator (Agones on Kubernetes is the recommended
  default; it models allocation, readiness and per-match lifetime natively).
- [ ] Fix readiness detection. Godot's stdout is block-buffered off a TTY, so
  `server_started` never appears in `docker logs` for a detached container —
  a log-grep readiness probe hangs forever. Probe the UDP socket, or flush.
- [ ] Support more than one match per host: a per-container port from a range,
  or one address per match. `--port` defaults to 7777 and the Dockerfile
  hardcodes `EXPOSE 7777/udp`.
- [ ] Add a no-show timeout so an allocated server that never fills abandons
  and exits instead of idling at cost.
- [ ] Re-measure boot-to-listening on native x86_64 Linux. The repo's current
  figure is ~870 ms, measured under emulation on arm64 — a pessimistic bound.
- [ ] Re-measure the SERVER.md sizing estimate (6–10 processes/core,
  150–250 MB RSS) under real concurrency before it sizes a bill.
- [ ] Keep `make verify-phase6` and `make verify-enet-integration` green:
  every allocation feature is opt-in via a `ServerConfig` flag defaulting to
  today's behaviour, with a second Compose file for the allocated path rather
  than mutating `compose.phase6-smoke.yml`.

## Known issues to resolve before public hosting

- [ ] Slot reclaim is currently keyed by display name, so someone can take a
  disconnected player's reserved slot. Do not expose public servers before
  verified Steam identity lands.
- [ ] Investigate occasional input loss during a long server stall; the
  existing sequence resync recovers it, but transport delivery is variable.
- [ ] Fix the remaining `_broadcast_snapshot` packet-send stderr race.

## Decide after the latency playtest

- [ ] Decide whether client-only, contact-cohort shadow physics is worthwhile
  for the remaining prediction weakness.

## Explicitly deferred

120 Hz simulation, latency-gap measurement, audio hooks, and split-screen are
not part of the current multiplayer release path.