CupHeads v1.4.0

Feature release. The version jumps past the retired 1.3.x line so stale installs can never be confused with current builds again.

Both players must run this same version. The connection handshake now carries the mod version and a wire-protocol number, so mismatched builds are refused with a clear message instead of silently desyncing.

Fixes (the boss-entry softlock)

• Enemy and boss state are now addressed by a deterministic cross-machine ID instead of Unity's process-local instance IDs, which could never match between two PCs.
• Boss HP is synchronised through the game's own damage path, so phase changes and the knockout stay in step.
• The parry broadcast, deterministic RNG, and a handful of input hooks all targeted methods that do not exist in Cuphead and silently failed to apply. They now hit the correct methods, so co-op fights no longer desync into a softlock.
• The mod logs a loud error and shows an in-game warning card if any hook ever fails to apply again.

Safety

• Version + protocol handshake; incompatible builds are refused with a clear message.
• Level-entry ready gate: the host briefly holds the fight until the guest's scene finishes loading (fail-open timeout).
• Automatic reconnect after an unexpected mid-run disconnect.
• Desync sentinel that samples boss HP and player positions and auto-resyncs after repeated mismatches.

Features

• Plane (shmup) level sync, ping-adaptive smoothing, and visual tracer streaks for the other player's shots.
• Comm wheel: hold C then press 1-4 to send WAIT / GO / REVIVE ME / SWELL WORK.
• Team results card on the knockout screen with both players' stats.
• A knocked-out player can steer their revive ghost sideways.
• Lobby ping and save-synced indicators, plus a join toast.

Under the hood

• A shared vintage UI theme using the game's own fonts on 1930s-style card panels.
• A Harmony hook audit that verifies every patch target against the game code and fails the build if one breaks.

Install with CupHeads.exe, or drop CupheadOnline.dll into Cuphead/BepInEx/plugins/CupheadOnline/. After launching, the BepInEx log should read Loading [CupHeads 1.4.0].