.NET: [Bug]: Unable to filter out tool messages from the chat history

[marcominerva]

Description

Using the StorageInputMessageFilter property of InMemoryChatHistoryProvider, I can filter messages before actually saving them to the store. However, suppose I do something like this:

var session = await agent.CreateSessionAsync();
var response = await agent.RunAsync("What is the weather like in Taggia?", session);

Assume that I have added an MCP tool to the Agent that provides weather information. In this situation, when the StorageInputMessageFilter function is invoked, it only receives the user’s question, not the messages generated by the tool that are used to produce the assistant’s response.

So, with this code:

var history = await agent.SerializeSessionAsync(session);
var json = history.GetRawText();

I get something like this:

{
   "stateBag":{
      "InMemoryChatHistoryProvider":{
         "messages":[
            {
               "role":"user",
               "contents":[
                  {
                     "$type":"text",
                     "text":"what is the weather like in taggia?"
                  }
               ]
            },
            {
               "authorName":"Default",
               "createdAt":"2026-02-25T15:29:06+00:00",
               "role":"assistant",
               "contents":[
                  {
                     "$type":"functionCall",
                     "callId":"call_pkfoo13EAg7rE31Zj2AramGU",
                     "name":"get_current_weather",
                     "arguments":{
                        "city":"Taggia"
                     },
                     "informationalOnly":true
                  }
               ],
               "messageId":"chatcmpl-DDB6whyBMG5qsKwQHCMAAwUnHyLx0"
            },
            {
               "authorName":"Default",
               "createdAt":"2026-02-25T15:29:06.5427865+00:00",
               "role":"tool",
               "contents":[
                  {
                     "$type":"functionResult",
                     "callId":"call_pkfoo13EAg7rE31Zj2AramGU",
                     "result":{
                        "content":[
                           {
                              "type":"text",
                              "text":"{\"cityName\":\"Taggia\",\"condition\":\"Clouds\",\"conditionIcon\":\"03d\",\"conditionIconUrl\":\"https://openweathermap.org/img/w/03d.png\",\"conditionDescription\":\"scattered clouds\",\"temperature\":14.79,\"units\":\"Metric\"}"
                           }
                        ],
                        "structuredContent":{
                           "cityName":"Taggia",
                           "condition":"Clouds",
                           "conditionIcon":"03d",
                           "conditionIconUrl":"https://openweathermap.org/img/w/03d.png",
                           "conditionDescription":"scattered clouds",
                           "temperature":14.79,
                           "units":"Metric"
                        }
                     }
                  }
               ],
               "messageId":"094bdfe0e2104be4b517bf687c09b76e"
            },
            {
               "authorName":"Default",
               "createdAt":"2026-02-25T15:29:07+00:00",
               "role":"assistant",
               "contents":[
                  {
                     "$type":"text",
                     "text":"The current weather in Taggia is scattered clouds with a temperature of about 14.8°C."
                  }
               ],
               "messageId":"chatcmpl-DDB6xyFaI8YUys7xJfxaJdOC3wbKg"
            }
         ]
      }
   }
}

I would like to exclude the functionCall and functionResult messages from the history. Is it possible?

Package Versions

Microsoft.Agents.AI.OpenAI: 1.0.0-rc1

.NET Version

.NET 10.0.3

[filipw]

A related question is why the user messages are always saved without a CreatedAt?

[westey-m]

Thanks, @marcominerva, this makes sense. Let me look into getting this supported.

[westey-m]

A related question is why the user messages are always saved without a CreatedAt?

@filipw, since user messages are typically produced by the agent caller, it is up to the caller to set CreatedAt to the value they want. Agent Framework does not set or change CreatedAt for request messages, including for the RunAsync(string, options, CancellationToken) overload, so it is null by default. This is a deliberate decision which was made to avoid any cache misses if using response caching that may use CreatedAt as part of the cache key.

Therefore, if you want CreatedAt on user messages do the following:

var message = new ChatMessage(ChatRole.User, "Hello") { CreatedAt = DateTimeOffset.UtcNow };
await agent.RunAsync(message);