2 files changed, 57 insertions, 1 deletions
diff --git a/internal/provider/forwarder.go b/internal/provider/forwarder.go
index a9d5734..0d40bb1 100644
--- a/internal/provider/forwarder.go
+++ b/internal/provider/forwarder.go
@@ -49,7 +49,7 @@ func (f *Forwarder) Forward(ctx context.Context, protocol domain.Protocol, reque
 		if err := ctx.Err(); err != nil {
 			return Result{Attempts: i}, err
 		}
-		body, err := rewriteModel(originalBody, route.UpstreamModel)
+		body, err := rewriteRequest(originalBody, route.UpstreamModel, protocol)
 		if err != nil {
 			return Result{Attempts: i}, err
 		}
@@ -80,12 +80,29 @@ func (f *Forwarder) Forward(ctx context.Context, protocol domain.Protocol, reque
 }
 
 func rewriteModel(body []byte, upstreamModel string) ([]byte, error) {
+	return rewriteRequest(body, upstreamModel, "")
+}
+
+func rewriteRequest(body []byte, upstreamModel string, protocol domain.Protocol) ([]byte, error) {
 	var object map[string]json.RawMessage
 	if err := json.Unmarshal(body, &object); err != nil {
 		return nil, fmt.Errorf("decode request body: %w", err)
 	}
 	encoded, _ := json.Marshal(upstreamModel)
 	object["model"] = encoded
+	if protocol == domain.ProtocolOpenAI {
+		var stream bool
+		_ = json.Unmarshal(object["stream"], &stream)
+		if stream {
+			var options map[string]json.RawMessage
+			_ = json.Unmarshal(object["stream_options"], &options)
+			if options == nil {
+				options = map[string]json.RawMessage{}
+			}
+			options["include_usage"] = json.RawMessage("true")
+			object["stream_options"], _ = json.Marshal(options)
+		}
+	}
 	result, err := json.Marshal(object)
 	if err != nil {
 		return nil, fmt.Errorf("encode upstream request: %w", err)
diff --git a/internal/provider/forwarder_test.go b/internal/provider/forwarder_test.go
new file mode 100644
index 0000000..2e9b4a1
--- /dev/null
+++ b/internal/provider/forwarder_test.go
@@ -0,0 +1,39 @@
+package provider
+
+import (
+	"encoding/json"
+	"testing"
+
+	"aigw/internal/domain"
+)
+
+func TestRewriteRequestForcesOpenAIStreamUsage(t *testing.T) {
+	result, err := rewriteRequest([]byte(`{"model":"public/model","stream":true,"stream_options":{"other":true}}`), "upstream/model", domain.ProtocolOpenAI)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var body struct {
+		Model         string         `json:"model"`
+		StreamOptions map[string]any `json:"stream_options"`
+	}
+	if err := json.Unmarshal(result, &body); err != nil {
+		t.Fatal(err)
+	}
+	if body.Model != "upstream/model" || body.StreamOptions["include_usage"] != true || body.StreamOptions["other"] != true {
+		t.Fatalf("unexpected rewritten body: %s", result)
+	}
+}
+
+func TestRewriteRequestDoesNotAddStreamOptionsToAnthropic(t *testing.T) {
+	result, err := rewriteRequest([]byte(`{"model":"public/model","stream":true}`), "upstream/model", domain.ProtocolAnthropic)
+	if err != nil {
+		t.Fatal(err)
+	}
+	var body map[string]json.RawMessage
+	if err := json.Unmarshal(result, &body); err != nil {
+		t.Fatal(err)
+	}
+	if _, exists := body["stream_options"]; exists {
+		t.Fatalf("unexpected OpenAI stream options in Anthropic request: %s", result)
+	}
+}