diff --git a/provider/openaiprovider/chat.go b/provider/openaiprovider/chat.go
index 9b551d43..55d66b3b 100644
--- a/provider/openaiprovider/chat.go
+++ b/provider/openaiprovider/chat.go
@@ -149,6 +149,7 @@ func (a *chatClient) run(ctx context.Context, messages []*message.Message, optio
 		// the streaming path below.
 		var contents []message.Content
 		var finishReason string
+		var additionalProperties map[string]any
 		if len(resp.Choices) > 0 {
 			choice := resp.Choices[0]
 			contents = make([]message.Content, 0, 1+len(choice.Message.ToolCalls))
@@ -168,19 +169,29 @@ func (a *chatClient) run(ctx context.Context, messages []*message.Message, optio
 				contents = append(contents, &message.ErrorContent{Message: choice.Message.Refusal, ErrorCode: "Refusal"})
 			}
 			finishReason = normalizeChatFinishReason(choice.FinishReason)
+			if len(choice.Logprobs.Content) > 0 || len(choice.Logprobs.Refusal) > 0 {
+				additionalProperties = map[string]any{"Logprobs": choice.Logprobs}
+			}
+		}
+		if resp.SystemFingerprint != "" {
+			if additionalProperties == nil {
+				additionalProperties = make(map[string]any)
+			}
+			additionalProperties["SystemFingerprint"] = resp.SystemFingerprint
 		}
 		if resp.JSON.Usage.Valid() {
 			contents = addUsage(contents, resp.Usage)
 		}
 		return func(yield func(*agent.ResponseUpdate, error) bool) {
 			update := &agent.ResponseUpdate{
-				Contents:          contents,
-				Role:              message.RoleAssistant,
-				ResponseID:        resp.ID,
-				MessageID:         resp.ID,
-				FinishReason:      finishReason,
-				CreatedAt:         time.Unix(resp.Created, 0),
-				RawRepresentation: resp,
+				Contents:             contents,
+				Role:                 message.RoleAssistant,
+				ResponseID:           resp.ID,
+				MessageID:            resp.ID,
+				FinishReason:         finishReason,
+				CreatedAt:            time.Unix(resp.Created, 0),
+				AdditionalProperties: additionalProperties,
+				RawRepresentation:    resp,
 			}
 			if !yield(update, nil) {
 				return
@@ -198,6 +209,10 @@ func (a *chatClient) run(ctx context.Context, messages []*message.Message, optio
 		stream := a.client.Chat.Completions.NewStreaming(ctx, body, telemetryOption)
 		defer func() { _ = stream.Close() }()
 		var acc openai.ChatCompletionAccumulator
+		// Logprobs stream incrementally (one chunk carries only its own tokens),
+		// so accumulate them across chunks; each update carries the running total
+		// and the final message keeps the complete per-choice list.
+		var accLogprobs openai.ChatCompletionChunkChoiceLogprobs
 		var created int64
 		for stream.Next() {
 			chunk := stream.Current()
@@ -221,17 +236,32 @@ func (a *chatClient) run(ctx context.Context, messages []*message.Message, optio
 				contents = addUsage(contents, chunk.Usage)
 			}
 			var finishReason string
+			var additionalProperties map[string]any
 			if len(chunk.Choices) > 0 {
 				finishReason = normalizeChatFinishReason(chunk.Choices[0].FinishReason)
+				if logprobs := chunk.Choices[0].Logprobs; len(logprobs.Content) > 0 || len(logprobs.Refusal) > 0 {
+					accLogprobs.Content = append(accLogprobs.Content, logprobs.Content...)
+					accLogprobs.Refusal = append(accLogprobs.Refusal, logprobs.Refusal...)
+				}
+			}
+			if len(accLogprobs.Content) > 0 || len(accLogprobs.Refusal) > 0 {
+				additionalProperties = map[string]any{"Logprobs": accLogprobs}
+			}
+			if chunk.SystemFingerprint != "" {
+				if additionalProperties == nil {
+					additionalProperties = make(map[string]any)
+				}
+				additionalProperties["SystemFingerprint"] = chunk.SystemFingerprint
 			}
 			resp := &agent.ResponseUpdate{
-				Contents:          contents,
-				Role:              role,
-				ResponseID:        chunk.ID,
-				MessageID:         chunk.ID,
-				FinishReason:      finishReason,
-				CreatedAt:         time.Unix(chunk.Created, 0),
-				RawRepresentation: chunk,
+				Contents:             contents,
+				Role:                 role,
+				ResponseID:           chunk.ID,
+				MessageID:            chunk.ID,
+				FinishReason:         finishReason,
+				CreatedAt:            time.Unix(chunk.Created, 0),
+				AdditionalProperties: additionalProperties,
+				RawRepresentation:    chunk,
 			}
 			if !yield(resp, nil) {
 				return
diff --git a/provider/openaiprovider/chat_test.go b/provider/openaiprovider/chat_test.go
index a42e5c02..99f0d422 100644
--- a/provider/openaiprovider/chat_test.go
+++ b/provider/openaiprovider/chat_test.go
@@ -837,6 +837,85 @@ func TestChatBasicRequestResponse_NonStreaming(t *testing.T) {
 	}
 }
 
+// system_fingerprint (response) and per-choice logprobs must be surfaced on the
+// update's AdditionalProperties, matching the Python client which carries both
+// as chat response metadata.
+func TestChatResponseMetadataSurfaced_NonStreaming(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-md","object":"chat.completion","created":1727888631,"model":"gpt-4o-mini","system_fingerprint":"fp_test","choices":[{"index":0,"message":{"role":"assistant","content":"ok"},"logprobs":{"content":[{"token":"ok","logprob":-0.1,"bytes":[111,107],"top_logprobs":[]}]},"finish_reason":"stop"}]}`)
+	}))
+	defer server.Close()
+
+	resp, err := newTestClient(server).RunText(t.Context(), "hi").Collect()
+	if err != nil {
+		t.Fatalf("error = %v", err)
+	}
+	props := lastMessageAdditionalProperties(t, resp)
+	if props["SystemFingerprint"] != "fp_test" {
+		t.Errorf("SystemFingerprint = %v, want %q", props["SystemFingerprint"], "fp_test")
+	}
+	if _, ok := props["Logprobs"]; !ok {
+		t.Errorf("Logprobs missing from AdditionalProperties: %#v", props)
+	}
+}
+
+func TestChatResponseMetadataSurfaced_Streaming(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, "data: {\"id\":\"chatcmpl-md\",\"object\":\"chat.completion.chunk\",\"created\":1727888631,\"model\":\"gpt-4o-mini\",\"system_fingerprint\":\"fp_test\",\"choices\":[{\"index\":0,\"delta\":{\"role\":\"assistant\",\"content\":\"ok\"},\"finish_reason\":\"stop\"}]}\n\n")
+		_, _ = io.WriteString(w, "data: [DONE]\n\n")
+	}))
+	defer server.Close()
+
+	resp, err := newTestClient(server).RunText(t.Context(), "hi", agent.Stream(true)).Collect()
+	if err != nil {
+		t.Fatalf("error = %v", err)
+	}
+	props := lastMessageAdditionalProperties(t, resp)
+	if props["SystemFingerprint"] != "fp_test" {
+		t.Errorf("SystemFingerprint = %v, want %q", props["SystemFingerprint"], "fp_test")
+	}
+}
+
+// Streaming logprobs arrive incrementally per chunk; the collected message must
+// carry the accumulated per-choice list, not just the final chunk's tokens.
+func TestChatStreamingLogprobsAccumulated(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, "data: {\"id\":\"c\",\"object\":\"chat.completion.chunk\",\"created\":1,\"model\":\"gpt-4o-mini\",\"choices\":[{\"index\":0,\"delta\":{\"role\":\"assistant\",\"content\":\"Hel\"},\"logprobs\":{\"content\":[{\"token\":\"Hel\",\"logprob\":-0.1,\"bytes\":[72],\"top_logprobs\":[]}]}}]}\n\n")
+		_, _ = io.WriteString(w, "data: {\"id\":\"c\",\"object\":\"chat.completion.chunk\",\"created\":1,\"model\":\"gpt-4o-mini\",\"choices\":[{\"index\":0,\"delta\":{\"content\":\"lo\"},\"logprobs\":{\"content\":[{\"token\":\"lo\",\"logprob\":-0.2,\"bytes\":[108],\"top_logprobs\":[]}]},\"finish_reason\":\"stop\"}]}\n\n")
+		_, _ = io.WriteString(w, "data: [DONE]\n\n")
+	}))
+	defer server.Close()
+
+	resp, err := newTestClient(server).RunText(t.Context(), "hi", agent.Stream(true)).Collect()
+	if err != nil {
+		t.Fatalf("error = %v", err)
+	}
+	props := lastMessageAdditionalProperties(t, resp)
+	lp, ok := props["Logprobs"].(openai.ChatCompletionChunkChoiceLogprobs)
+	if !ok {
+		t.Fatalf("Logprobs = %T, want ChatCompletionChunkChoiceLogprobs", props["Logprobs"])
+	}
+	if len(lp.Content) != 2 {
+		t.Errorf("accumulated logprob content = %d tokens, want 2 (one per chunk)", len(lp.Content))
+	}
+}
+
+// lastMessageAdditionalProperties returns the AdditionalProperties of the last
+// message carrying any, so metadata assertions do not depend on message count.
+func lastMessageAdditionalProperties(t *testing.T, resp *agent.Response) map[string]any {
+	t.Helper()
+	for i := len(resp.Messages) - 1; i >= 0; i-- {
+		if len(resp.Messages[i].AdditionalProperties) > 0 {
+			return resp.Messages[i].AdditionalProperties
+		}
+	}
+	t.Fatalf("no message carried AdditionalProperties: %#v", resp.Messages)
+	return nil
+}
+
 // cache_write_tokens (prompt-cache writes / cache creation) must be surfaced via AdditionalCounts,
 // matching the Python client.
 func TestChatCacheWriteTokensSurfaced(t *testing.T) {