microsoft/autogen · error · Exception

Agent factory with type {type} already exists.

Error message

Agent factory with type {type} already exists.

What it means

GrpcAgentTypesHost.RegisterAgentFactory throws when a factory for the same AgentType is already registered. The host keeps a Dictionary<AgentType, Func<...>> and refuses duplicate keys to prevent silently replacing agent implementations.

Source

Thrown at dotnet/src/Microsoft.AutoGen/Core.Grpc/GrpcAgentRuntime.cs:57

        return this.agentInstances[agentId];
    }

    public async ValueTask<Contracts.AgentId> GetAgentAsync(Contracts.AgentId agentId, bool lazy = true)
    {
        if (!lazy)
        {
            await this.EnsureAgentAsync(agentId);
        }

        return agentId;
    }

    public AgentType RegisterAgentFactory(AgentType type, Func<Contracts.AgentId, IAgentRuntime, ValueTask<IHostableAgent>> factoryFunc)
    {
        if (this.agentFactories.ContainsKey(type))
        {
            throw new Exception($"Agent factory with type {type} already exists.");
        }

        this.agentFactories.Add(type, factoryFunc);
        return type;
    }

    public void AddSubscription(ISubscriptionDefinition subscription)
    {
        if (this.Subscriptions.ContainsKey(subscription.Id))
        {
            throw new Exception($"Subscription with id {subscription.Id} already exists.");
        }

        this.Subscriptions.Add(subscription.Id, subscription);
    }

    public bool RemoveSubscriptionAsync(string subscriptionId)
    {

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Remove the duplicate registration — search for all RegisterAgentFactory/AddAgent calls for that type and keep one.
2. If using auto-registration attributes, delete the manual registration (or vice versa).
3. Guard registration with a check of RegisteredAgentTypes before calling RegisterAgentFactory in shared/pluggable code.

Example fix

// before
host.RegisterAgentFactory(new AgentType("planner"), plannerFactory);
host.RegisterAgentFactory(new AgentType("planner"), plannerFactory); // throws: duplicate

// after
if (!host.RegisteredAgentTypes.Contains(new AgentType("planner")))
{
    host.RegisterAgentFactory(new AgentType("planner"), plannerFactory);
}

if (!host.RegisteredAgentTypes.Contains(type))
{
    host.RegisterAgentFactory(type, factoryFunc);
}

static bool IsFactoryRegistered(GrpcAgentTypesHost host, AgentType type) =>
    host.RegisteredAgentTypes.Contains(type);

When it happens

Trigger: Calling RegisterAgentFactory(type, factory) twice with the same AgentType — commonly from double execution of startup code, hosting the same agent in two hosting groups, or DI lifetimes that re-run registration (e.g. scoped resolution invoking a register method).

Common situations: Adding the same agent via two AddAgent/RegisterAgent calls (e.g. in a shared extension method called twice); hot-reload or retry logic in startup that re-executes registration; combining an auto-scan/registration assembly attribute with explicit manual registration; tests that build the host multiple times against a shared host instance.

Related errors

• Agent with name {agentId.Type} not found.
• Subscription with id {subscription.Id} already exists.
• INVALID_ARGUMENT
• Agent with type {type} already exists.
• Agent with id {agent_id} already exists.

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/b1798a73466cef71. Report an issue: GitHub.