NEVER Do (Expert Multiplayer Rules)

NEVER trust client-reported state — Clients own their 'Input', NOT their 'Position' or 'Health'. Server must validate every coordinate and health change.
NEVER use get_tree() groups for authority checks — Use is_multiplayer_authority(). Group registration is non-deterministic in high-latency joins.
NEVER allow unrestricted RPC rates — A malicious client can call a 'FireWeapon' RPC 10,000 times per second. Always implement rate-limiting (net_rpc_rate_limiter.gd).

NEVER skip Client-Side Prediction — Movement without prediction feels 'heavy' and unresponsive. Predict movement locally, then correct only on server disagreement.
NEVER sync peers at 60Hz — Sending entire state every frame will saturate client bandwidth. Use a lower tick-rate (20-30Hz) and interpolate between packets.
NEVER snap peer positions — Abrupt position updates cause 'jitter'. Store a buffer of past states and lerp between them with a 100ms delay.

NEVER sync 'Full Floats' if possible — Quantize Vector3 data (truncating decimals) to save 50%+ bandwidth. Use MultiplayerSynchronizer with delta-sync enabled.
NEVER ignore 'Late Joiners' — Players who join mid-game won't see existing environmental changes. Broadcast a full world-state 'Snapshot' on peer connection.
NEVER test on 0ms ping — Everything works on localhost. Use a simulator (net_latency_simulator.gd) with 150ms ping to identify sync bugs.

godot-adapt-single-to-multiplayer