Quick answer: Godot 4 MultiplayerSpawner ignoring nodes that exist in the scene at startup? Spawner only tracks runtime spawns - mark pre-existing nodes with the spawner.
Level has placed enemies. Host sees them; clients connect to empty world.
Pre-register existing nodes
On _ready: spawner.spawn(existing_node). Tracked from there; replicates to clients.
Or use scene-state replication
For levels with static content, replicate the scene tree at connection. Heavier; covers everything.
Verify with the network profile
Spawner tracks N nodes; expected M. Mismatch indicates which side has the bug.
“Spawners are runtime tools. Pre-existing actors need explicit registration.”
For levels with placed actors, the registration pass is non-optional. Document in your level workflow.