Network Setup

Generate networking code adapted to the project's chosen package.

Before You Start

1. Read docs/ProjectConfig.yaml for:
   • networking — the package name ("ngo", "mirror", "photon", or "none"). If "none", stop — do not generate networking code.
   • architecture_pattern — "so-first" or "di-first" (affects how network services are wired).
   • mcp.unity_mcp — if true, call refresh_unity after creating files.
2. Read docs/TDD_Template.md for the authority matrix (who owns what data).
3. Read docs/CODING_STANDARDS.md for async patterns (Awaitable + CancellationToken) and class structure.
4. Read docs/NAMING_CONVENTIONS.md for file/class naming.

Package Quick Reference

Each package has a detailed reference file. Read the relevant one before generating code:

• NGO (Netcode for GameObjects): references/ngo.md — Unity's first-party solution. Uses NetworkVariable, [Rpc] attributes.
• Mirror: references/mirror.md — Community open-source. Uses [SyncVar], [Command]/[ClientRpc].
• Photon (PUN2/Fusion): references/photon.md — Cloud-hosted. Uses IPunObservable, [PunRPC].

Core Patterns (All Packages)

State Synchronization

Every package has a mechanism for syncing state from server/host to clients. The pattern is the same — only the syntax differs.

Package	Sync Mechanism	Change Callback	Example
NGO	NetworkVariable<T>	.OnValueChanged += handler	_health.OnValueChanged += OnHealthChanged;
Mirror	[SyncVar(hook = nameof(...))]	Hook method	[SyncVar(hook = nameof(OnHealthChanged))]
Photon	IPunObservable	OnPhotonSerializeView	Manual read/write in serialize callback

Remote Procedure Calls (RPCs)

RPCs let clients request actions on the server, or the server push updates to clients.

NGO:

[Rpc(SendTo.Server)]
public void RequestDamageServerRpc(int amount)
{
    // Runs on server — validate before applying
    if (amount < 0 || amount > MAX_DAMAGE) return;
    _health.Value = Mathf.Max(0, _health.Value - amount);
}

[Rpc(SendTo.ClientsAndHost)]
public void PlayHitEffectClientRpc()
{
    // Runs on all clients — visual/audio only, no game state
}

Mirror:

[Command]
public void CmdRequestDamage(int amount)
{
    if (amount < 0 || amount > MAX_DAMAGE) return;
    _health = Mathf.Max(0, _health - amount);
    RpcPlayHitEffect();
}

[ClientRpc]
public void RpcPlayHitEffect()
{
    // Visual/audio feedback on all clients
}

Photon:

public void RequestDamage(int amount)
{
    photonView.RPC(nameof(RpcTakeDamage), RpcTarget.MasterClient, amount);
}

[PunRPC]
private void RpcTakeDamage(int amount, PhotonMessageInfo info)
{
    if (!PhotonNetwork.IsMasterClient) return;
    if (amount < 0 || amount > MAX_DAMAGE) return;
    _health = Mathf.Max(0, _health - amount);
}

Network Object Spawning

Spawning networked objects follows the same principle: only the server/host creates the authoritative instance, and the network layer replicates it to clients.

NGO:

// Server only — spawn a networked prefab
var instance = Instantiate(_projectilePrefab, spawnPoint.position, spawnPoint.rotation);
instance.GetComponent<NetworkObject>().Spawn();

Mirror:

// Server only
var instance = Instantiate(_projectilePrefab, spawnPoint.position, spawnPoint.rotation);
NetworkServer.Spawn(instance);

Photon:

// Room owner or any client (Photon handles ownership)
PhotonNetwork.Instantiate(_projectilePrefabName, spawnPoint.position, spawnPoint.rotation);

Authority Matrix Template

Define who owns, reads, and writes each piece of networked state. Fill this in before writing code — it prevents authority bugs.

Entity	Owner	Read	Write	Sync Method	Validation
Player Health	Server	Everyone	Server	NetworkVariable / SyncVar	Clamp 0-max, rate limit
Player Position	Server	Everyone	Server	NetworkTransform	Speed cap, teleport check
Player Input	Client	Server	Owner	RPC (client -> server)	Sanitize on server
Chat Messages	Client	Everyone	Owner	RPC	Length limit, rate limit
Game Timer	Server	Everyone	Server	NetworkVariable / SyncVar	Server-authoritative only
Inventory	Server	Owner	Server	RPC + NetworkVariable	Validate item exists

Abstraction Layer (Optional)

When the project might switch networking packages later, or when using DI (architecture_pattern: "di-first"), wrap networking behind an interface:

public interface INetworkService
{
    bool IsServer { get; }
    bool IsClient { get; }
    bool IsConnected { get; }
    void SendToServer<T>(T message) where T : struct;
    void SendToClients<T>(T message) where T : struct;
}

Register the concrete implementation in the DI container (see uw-dependency-injection). Game systems depend on INetworkService, not the package directly. This makes testing easier too — mock the interface in EditMode tests.

Custom Type Serialization

When syncing custom structs over the network, each package has its own serialization approach:

NGO — implement INetworkSerializable:

public struct DamageEvent : INetworkSerializable
{
    public int Amount;
    public ulong AttackerId;

    public void NetworkSerialize<T>(BufferSerializer<T> serializer) where T : IReaderWriter
    {
        serializer.SerializeValue(ref Amount);
        serializer.SerializeValue(ref AttackerId);
    }
}

Mirror — implement custom Reader/Writer extensions or use [SyncVar] with supported types.

Photon — serialize manually in OnPhotonSerializeView or register custom types with PhotonPeer.RegisterType.

Client Prediction & Lag Compensation

For responsive gameplay (especially movement and shooting), client-side prediction avoids waiting for server confirmation:

1. Client predicts — apply input locally immediately.
2. Server validates — process the input authoritatively, send correction.
3. Client reconciles — if server state differs from prediction, snap or interpolate to correct position.

This is complex. NGO has built-in NetworkTransform prediction. Mirror has community prediction examples. Photon Fusion has built-in state authority with rollback. For custom prediction, start with movement only and expand from there.

After Setup

• DI integration: If architecture_pattern: "di-first", use uw-dependency-injection to register network services in the container.
• Write tests: Use uw-unity-test-runner — test game logic in EditMode by mocking INetworkService. Test actual networking in PlayMode.
• Authority matrix: Fill in docs/TDD_Template.md with the authority matrix before writing any sync code.

Rules

• Server-authoritative unless docs/TDD_Template.md explicitly specifies peer-to-peer.
• Never trust client input — always validate on the server (bounds check, rate limit, permission check).
• Cache NetworkBehaviour references in Awake() or OnNetworkSpawn() — never GetComponent in Update.
• Use [SerializeField] private for prefab references and configuration — never public fields.
• Check the package version in ProjectConfig.yaml before using any API — breaking changes happen between major versions.
• Use Awaitable with CancellationToken for async network operations (connection, scene loading) per CODING_STANDARDS.md.
• All networking code must live inside an .asmdef.
• If ProjectConfig.yaml -> mcp.unity_mcp is true, call refresh_unity after creating files.