microsoft/autogen · error · Exception

Agent state for {agentId} is not a valid JSON object.

Error message

Agent state for {agentId} is not a valid JSON object.

What it means

Thrown by GrpcAgentRuntime.LoadStateAsync when the persisted agent-state JSON contains an entry whose value is not a JSON object. State is expected as a map of agentId string to an object that the agent's LoadStateAsync can consume; a scalar, array, or string value for any agentId is rejected.

Source

Thrown at dotnet/src/Microsoft.AutoGen/Core.Grpc/GrpcAgentRuntime.cs:448

    }

    public ValueTask<AgentProxy> TryGetAgentProxyAsync(Contracts.AgentId agentId)
    {
        // TODO: Do we want to support getting remote agent proxies?
        return ValueTask.FromResult(new AgentProxy(agentId, this));
    }

    public async ValueTask LoadStateAsync(JsonElement state)
    {
        HashSet<AgentType> registeredTypes = this._agentsContainer.RegisteredAgentTypes;

        foreach (var agentIdStr in state.EnumerateObject())
        {
            Contracts.AgentId agentId = Contracts.AgentId.FromStr(agentIdStr.Name);

            if (agentIdStr.Value.ValueKind != JsonValueKind.Object)
            {
                throw new Exception($"Agent state for {agentId} is not a valid JSON object.");
            }

            if (registeredTypes.Contains(agentId.Type))
            {
                IHostableAgent agent = await this._agentsContainer.EnsureAgentAsync(agentId);
                await agent.LoadStateAsync(agentIdStr.Value);
            }
        }
    }

    public async ValueTask<JsonElement> SaveStateAsync()
    {
        Dictionary<string, JsonElement> state = new();
        foreach (var agent in this._agentsContainer.LiveAgents)
        {
            var agentState = await agent.SaveStateAsync();
            state[agent.Id.ToString()] = JsonSerializer.SerializeToElement(agentState);
        }

View on GitHub (pinned to 027ecf0a37)

Solutions

1. Inspect the state JSON at the failing agentId and correct the entry so each value is a JSON object
2. Make sure you pass the exact element produced by SaveStateAsync (a top-level object mapping agentId strings to agent state objects)
3. If migrating state between versions, write a conversion step that reshapes entries into per-agent objects before loading

Example fix

// before
// state JSON: { "myagent/instance1": 42 }
await runtime.LoadStateAsync(rootElement);

// after
// state JSON: { "myagent/instance1": { "state": 42 } }
await runtime.LoadStateAsync(rootElement);

foreach (var p in root.EnumerateObject())
{
    if (p.Value.ValueKind != JsonValueKind.Object)
        throw new InvalidDataException($"State entry {p.Name} is not an object");
}

static bool IsValidStateDocument(JsonElement e) => e.ValueKind == JsonValueKind.Object && e.EnumerateObject().All(p => p.Value.ValueKind == JsonValueKind.Object);

try { await runtime.LoadStateAsync(state); } catch (Exception ex) when (ex.Message.Contains("not a valid JSON object")) { _logger.LogError(ex, "Corrupt state file; starting fresh"); }

When it happens

Trigger: Calling LoadStateAsync with a JsonElement whose per-agent values are not objects, e.g. {"type/key": "someString"} or {"type/key": 123}; hand-edited or externally produced state files; a state document saved by a different version with a different schema.

Common situations: Restoring checkpoints written by an older/newer version of the framework; passing the wrong JsonDocument root (e.g. an element nested one level too deep or shallow); user-modified state JSON.

Related errors

• expand_scenario expects an str or list for 'template'
• JSON content must be a dict
• JSON content must be a dict
• Failed to list MCP prompts
• Failed to get MCP prompt

AI-assisted analysis of microsoft/autogen@027ecf0a37 (2026-08-15). Data as JSON: /api/errors/578e4f44d9e62b98. Report an issue: GitHub.