[dotnet-port-api] Add Response.ModelID

agent/response.go

@@ -45,6 +45,10 @@ type Response struct {
 	// ID identifies this response.
 	ID string `json:",omitzero"`
 
+	// ModelID is the identifier of the model that produced this response, when
+	// the provider supplies it. It is empty otherwise.
+	ModelID string `json:",omitzero"`
+
 	// ConversationID identifies conversation history retained after this response
 	// by the service or per-service-call history persistence. When nil, the response
 	// does not claim that its messages can be recovered from a retained conversation.
@@ -160,6 +164,7 @@ func (resp *Response) ToUpdates() []*ResponseUpdate {
 			AgentID:              resp.AgentID,
 			MessageID:            msg.ID,
 			ResponseID:           resp.ID,
+			ModelID:              resp.ModelID,
 			ConversationID:       resp.ConversationID,
 			FinishReason:         resp.FinishReason,
 			AuthorName:           msg.AuthorName,
@@ -169,11 +174,12 @@ func (resp *Response) ToUpdates() []*ResponseUpdate {
 		})
 	}
 
-	if hasAdditionalProperties || resp.ContinuationToken != "" {
+	if hasAdditionalProperties || resp.ContinuationToken != "" || resp.ModelID != "" {
 		extra := &ResponseUpdate{
 			AdditionalProperties: resp.AdditionalProperties,
 			AgentID:              resp.AgentID,
 			ResponseID:           resp.ID,
+			ModelID:              resp.ModelID,
 			ConversationID:       resp.ConversationID,
 			ContinuationToken:    resp.ContinuationToken,
 			CreatedAt:            resp.CreatedAt,
@@ -216,6 +222,7 @@ func (resp *Response) Update(update *ResponseUpdate) {
 	// clear values already received for the response.
 	resp.AgentID = cmp.Or(update.AgentID, resp.AgentID)
 	resp.ID = cmp.Or(update.ResponseID, resp.ID)
+	resp.ModelID = cmp.Or(update.ModelID, resp.ModelID)
 	if update.ConversationID != nil {
 		resp.ConversationID = update.ConversationID
 	}
@@ -313,6 +320,11 @@ type ResponseUpdate struct {
 	// ResponseID identifies the response of which this update is a part.
 	ResponseID string
 
+	// ModelID is the identifier of the model that produced this update, when the
+	// provider supplies it. It is typically set on updates that carry provider
+	// response metadata.
+	ModelID string `json:",omitzero"`
+
 	// ConversationID identifies history retained by the service or per-service-call
 	// history persistence. Providers set it only when later requests can refer to that
 	// history instead of resending the messages. Nil means this update does not

agent/response_test.go

@@ -486,6 +486,26 @@ func TestResponse_CreatedAt(t *testing.T) {
 	}
 }
 
+// ModelID folds onto the response from later updates and round-trips through
+// ToUpdates, matching how ResponseID/FinishReason are handled.
+func TestResponse_Update_ModelID(t *testing.T) {
+	resp := &agent.Response{}
+	resp.Update(&agent.ResponseUpdate{MessageID: "m1", Contents: message.Contents{&message.TextContent{Text: "hi"}}})
+	resp.Update(&agent.ResponseUpdate{MessageID: "m1", ModelID: "gpt-4o-mini-2024-07-18"})
+	if resp.ModelID != "gpt-4o-mini-2024-07-18" {
+		t.Fatalf("ModelID = %q, want gpt-4o-mini-2024-07-18", resp.ModelID)
+	}
+
+	// Round-trip: ToUpdates carries ModelID, and re-collecting preserves it.
+	var collected agent.Response
+	for _, u := range resp.ToUpdates() {
+		collected.Update(u)
+	}
+	if collected.ModelID != resp.ModelID {
+		t.Errorf("round-tripped ModelID = %q, want %q", collected.ModelID, resp.ModelID)
+	}
+}
+
 func TestResponse_Update_AdditionalProperties(t *testing.T) {
 	resp := &agent.Response{}
 

provider/anthropicprovider/agent.go

@@ -124,6 +124,7 @@ func (a *client) run(ctx context.Context, messages []*message.Message, options .
 				Role:              message.RoleAssistant,
 				MessageID:         resp.ID,
 				ResponseID:        resp.ID,
+				ModelID:           string(resp.Model),
 				CreatedAt:         time.Now(),
 				FinishReason:      mapStopReason(resp.StopReason),
 				RawRepresentation: resp,
@@ -135,6 +136,7 @@ func (a *client) run(ctx context.Context, messages []*message.Message, options .
 		defer func() { _ = stream.Close() }()
 
 		var messageID string
+		var modelID string
 		var finishReason string
 		var usage message.UsageDetails
 		var accumulated anthropic.Message
@@ -150,6 +152,7 @@ func (a *client) run(ctx context.Context, messages []*message.Message, options .
 			switch event := event.AsAny().(type) {
 			case anthropic.MessageStartEvent:
 				messageID = cmp.Or(messageID, event.Message.ID)
+				modelID = cmp.Or(modelID, string(event.Message.Model))
 				usage.Add(toUsageDetails(event.Message.Usage))
 			case anthropic.MessageDeltaEvent:
 				// Anthropic reports the final cumulative output token count on
@@ -213,6 +216,7 @@ func (a *client) run(ctx context.Context, messages []*message.Message, options .
 				Role:              message.RoleAssistant,
 				ResponseID:        messageID,
 				MessageID:         messageID,
+				ModelID:           modelID,
 				CreatedAt:         time.Now(),
 				RawRepresentation: event,
 			}, nil) {
@@ -227,6 +231,7 @@ func (a *client) run(ctx context.Context, messages []*message.Message, options .
 			CreatedAt:    time.Now(),
 			Role:         message.RoleAssistant,
 			MessageID:    messageID,
+			ModelID:      modelID,
 			FinishReason: finishReason,
 			Contents: []message.Content{
 				&message.UsageContent{

provider/anthropicprovider/agent_test.go

@@ -247,6 +247,25 @@ func TestStreamingUsage_DoesNotDoubleCountOutputTokens(t *testing.T) {
 
 // minimalStreamingResponse returns an SSE stream that delivers payload as a
 // single text delta.
+// A streamed run collected via ResponseStream.Collect must surface the model
+// that produced the response on Response.ModelID, matching the non-streaming
+// path. The model arrives on the message_start event.
+func TestStreamingModelIDSurfaced(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "text/event-stream")
+		_, _ = io.WriteString(w, minimalStreamingResponse("hi"))
+	}))
+	defer server.Close()
+
+	resp, err := newTestClient(t, server).RunText(t.Context(), "hello", agent.Stream(true)).Collect()
+	if err != nil {
+		t.Fatalf("error = %v", err)
+	}
+	if resp.ModelID != "claude-3-5-sonnet-20241022" {
+		t.Errorf("ModelID = %q, want claude-3-5-sonnet-20241022", resp.ModelID)
+	}
+}
+
 func minimalStreamingResponse(payload string) string {
 	payloadJSON, _ := json.Marshal(payload)
 	return "" +

provider/geminiprovider/agent.go

@@ -140,6 +140,7 @@ func (a *client) run(ctx context.Context, messages []*message.Message, options .
 			yield(&agent.ResponseUpdate{
 				Contents:          responseContents,
 				Role:              message.RoleAssistant,
+				ModelID:           resp.ModelVersion,
 				FinishReason:      finishReason,
 				CreatedAt:         time.Now(),
 				RawRepresentation: resp,
@@ -187,6 +188,7 @@ func (a *client) run(ctx context.Context, messages []*message.Message, options .
 			if !yield(&agent.ResponseUpdate{
 				Contents:          streamContents,
 				Role:              message.RoleAssistant,
+				ModelID:           resp.ModelVersion,
 				FinishReason:      finishReason,
 				CreatedAt:         time.Now(),
 				RawRepresentation: resp,
@@ -202,6 +204,7 @@ func (a *client) run(ctx context.Context, messages []*message.Message, options .
 			yield(&agent.ResponseUpdate{
 				Contents:          finalContents,
 				Role:              message.RoleAssistant,
+				ModelID:           latestMetadataResp.ModelVersion,
 				CreatedAt:         time.Now(),
 				RawRepresentation: latestMetadataResp,
 			}, nil)

provider/openaiprovider/chat.go

@@ -160,6 +160,7 @@ func (a *chatClient) run(ctx context.Context, messages []*message.Message, optio
 				Role:              message.RoleAssistant,
 				ResponseID:        resp.ID,
 				MessageID:         resp.ID,
+				ModelID:           resp.Model,
 				FinishReason:      finishReason,
 				CreatedAt:         time.Unix(resp.Created, 0),
 				RawRepresentation: resp,
@@ -216,6 +217,7 @@ func (a *chatClient) run(ctx context.Context, messages []*message.Message, optio
 				Role:              role,
 				ResponseID:        chunk.ID,
 				MessageID:         chunk.ID,
+				ModelID:           chunk.Model,
 				FinishReason:      finishReason,
 				CreatedAt:         time.Unix(chunk.Created, 0),
 				RawRepresentation: chunk,

provider/openaiprovider/chat_test.go

@@ -611,6 +611,23 @@ func TestChatLegacyFunctionCallFinishReasonNormalized_Streaming(t *testing.T) {
 	}
 }
 
+// The model that produced the response must be surfaced on Response.ModelID.
+func TestChatModelIDSurfaced(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = io.WriteString(w, `{"id":"chatcmpl-m","object":"chat.completion","created":1727888631,"model":"gpt-4o-mini-2024-07-18","choices":[{"index":0,"message":{"role":"assistant","content":"ok"},"finish_reason":"stop"}]}`)
+	}))
+	defer server.Close()
+
+	resp, err := newTestClient(server).RunText(t.Context(), "hi").Collect()
+	if err != nil {
+		t.Fatalf("error = %v", err)
+	}
+	if resp.ModelID != "gpt-4o-mini-2024-07-18" {
+		t.Errorf("ModelID = %q, want gpt-4o-mini-2024-07-18", resp.ModelID)
+	}
+}
+
 func TestChatURLCitationAnnotations_NonStreaming(t *testing.T) {
 	const input = `
             {

provider/openaiprovider/responses.go

@@ -1119,6 +1119,7 @@ func responsesProcessResponse(resp *responses.Response, seqNum int64, yield func
 
 	currentUpdate := &agent.ResponseUpdate{
 		ResponseID:   resp.ID,
+		ModelID:      resp.Model,
 		FinishReason: finishReason,
 		CreatedAt:    time.Unix(int64(resp.CreatedAt), 0),
 		Role:         message.RoleAssistant,
@@ -1140,6 +1141,7 @@ func responsesProcessResponse(resp *responses.Response, seqNum int64, yield func
 			}
 			currentUpdate.MessageID = out.ID
 			currentUpdate.ResponseID = resp.ID
+			currentUpdate.ModelID = resp.Model
 			currentUpdate.FinishReason = finishReason
 			// Only set ContinuationToken if it's not empty
 			if contToken != "" {
@@ -1429,6 +1431,7 @@ func responsesErrorContent(msg string, code string, details string) *message.Err
 type responsesStreamState struct {
 	mcpApprovalRequests map[string]*message.ToolApprovalRequestContent
 	messageID           string
+	model               string
 	role                message.Role
 	anyFunctions        bool
 	// imagePartialsSeen records image-generation item IDs that emitted a
@@ -1447,12 +1450,23 @@ func responsesProcessStreamingUpdate(update responses.ResponseStreamEventUnion,
 			Role:              role,
 			Contents:          contents,
 			MessageID:         state.messageID,
+			ModelID:           state.model,
 			ResponseID:        responseID,
 			RawRepresentation: update,
 		}
 		return u
 	}
 
+	// setModel records the response model from a lifecycle event so this and
+	// every subsequent streaming update carries it, matching the non-streaming
+	// path. The createUpdate above runs before this, so stamp u directly too.
+	setModel := func(u *agent.ResponseUpdate, model string) {
+		if model != "" {
+			state.model = model
+			u.ModelID = model
+		}
+	}
+
 	// Lifecycle metadata belongs to the response, not the active message.
 	// Omit its MessageID without resetting the state used by content updates.
 	var u *agent.ResponseUpdate
@@ -1462,6 +1476,7 @@ func responsesProcessStreamingUpdate(update responses.ResponseStreamEventUnion,
 		u.MessageID = ""
 		u.CreatedAt = time.Unix(int64(event.Response.CreatedAt), 0)
 		u.ResponseID = event.Response.ID
+		setModel(u, event.Response.Model)
 		u.AdditionalProperties = responsesPopulateAdditionalProperties(&event.Response)
 		if contToken := createContinuationToken(event.Response.ID, event.SequenceNumber, event.Response.Status, isBackground); contToken != "" {
 			u.ContinuationToken = contToken
@@ -1472,6 +1487,7 @@ func responsesProcessStreamingUpdate(update responses.ResponseStreamEventUnion,
 		u.MessageID = ""
 		u.CreatedAt = time.Unix(int64(event.Response.CreatedAt), 0)
 		u.ResponseID = event.Response.ID
+		setModel(u, event.Response.Model)
 		u.AdditionalProperties = responsesPopulateAdditionalProperties(&event.Response)
 		if contToken := createContinuationToken(event.Response.ID, event.SequenceNumber, event.Response.Status, isBackground); contToken != "" {
 			u.ContinuationToken = contToken
@@ -1482,6 +1498,7 @@ func responsesProcessStreamingUpdate(update responses.ResponseStreamEventUnion,
 		u.MessageID = ""
 		u.CreatedAt = time.Unix(int64(event.Response.CreatedAt), 0)
 		u.ResponseID = event.Response.ID
+		setModel(u, event.Response.Model)
 		u.AdditionalProperties = responsesPopulateAdditionalProperties(&event.Response)
 		if contToken := createContinuationToken(event.Response.ID, event.SequenceNumber, event.Response.Status, isBackground); contToken != "" {
 			u.ContinuationToken = contToken
@@ -1509,6 +1526,7 @@ func responsesProcessStreamingUpdate(update responses.ResponseStreamEventUnion,
 		u.MessageID = ""
 		u.CreatedAt = time.Unix(int64(event.Response.CreatedAt), 0)
 		u.ResponseID = event.Response.ID
+		setModel(u, event.Response.Model)
 		u.FinishReason = responsesFinishReason(&event.Response)
 		if state.anyFunctions && u.FinishReason == "stop" {
 			u.FinishReason = "tool_calls"
@@ -1524,6 +1542,7 @@ func responsesProcessStreamingUpdate(update responses.ResponseStreamEventUnion,
 		u.MessageID = ""
 		u.CreatedAt = time.Unix(int64(event.Response.CreatedAt), 0)
 		u.ResponseID = event.Response.ID
+		setModel(u, event.Response.Model)
 		u.FinishReason = responsesFinishReason(&event.Response)
 		u.AdditionalProperties = responsesPopulateAdditionalProperties(&event.Response)
 		if contToken := createContinuationToken(event.Response.ID, event.SequenceNumber, event.Response.Status, isBackground); contToken != "" {
@@ -1535,6 +1554,7 @@ func responsesProcessStreamingUpdate(update responses.ResponseStreamEventUnion,
 		u.MessageID = ""
 		u.CreatedAt = time.Unix(int64(event.Response.CreatedAt), 0)
 		u.ResponseID = event.Response.ID
+		setModel(u, event.Response.Model)
 		u.AdditionalProperties = responsesPopulateAdditionalProperties(&event.Response)
 		if failure := responsesFailureContent(&event.Response); failure != nil {
 			u.Contents = []message.Content{failure}