From 0a9def019488b13cd609bce8f42ffe96c58ef9f8 Mon Sep 17 00:00:00 2001
From: ell-hol <yacine.zahidi@gmail.com>
Date: Sat, 20 Jun 2026 11:25:15 +0200
Subject: [PATCH] Fix default string serialization in request marshaling

---
 internal/utils/json.go                     |  4 +++
 models/components/responsesrequest_test.go | 33 ++++++++++++++++++++++
 2 files changed, 37 insertions(+)
 create mode 100644 models/components/responsesrequest_test.go

diff --git a/internal/utils/json.go b/internal/utils/json.go
index a5a64183..da8de7a4 100644
--- a/internal/utils/json.go
+++ b/internal/utils/json.go
@@ -444,6 +444,10 @@ func handleDefaultConstValue(tagValue string, val interface{}, tag reflect.Struc
 			return []byte(fmt.Sprintf("%q", tagValue))
 		}
 	}
+	
+	if !json.Valid([]byte(tagValue)) {
+		return []byte(fmt.Sprintf("%q", tagValue))
+	}
 
 	return []byte(tagValue)
 }
diff --git a/models/components/responsesrequest_test.go b/models/components/responsesrequest_test.go
new file mode 100644
index 00000000..fac81403
--- /dev/null
+++ b/models/components/responsesrequest_test.go
@@ -0,0 +1,33 @@
+package components_test
+
+import (
+	"bytes"
+	"encoding/json"
+	"testing"
+
+	openrouter "github.com/OpenRouterTeam/go-sdk"
+	"github.com/OpenRouterTeam/go-sdk/models/components"
+)
+
+func TestResponsesRequestMarshalWithoutServiceTier(t *testing.T) {
+	req := components.ResponsesRequest{
+		Input: openrouter.Pointer(
+			components.CreateInputsUnionStr("Hey there"),
+		),
+		Model:  openrouter.Pointer("openai/gpt-4o-mini"),
+		Stream: openrouter.Bool(false),
+	}
+
+	b, err := json.Marshal(req)
+	if err != nil {
+		t.Fatalf("marshal failed: %v", err)
+	}
+
+	if !json.Valid(b) {
+		t.Fatalf("invalid JSON: %s", string(b))
+	}
+
+	if !bytes.Contains(b, []byte(`"service_tier":"auto"`)) {
+		t.Fatalf("expected service_tier default to be marshaled as string auto, got: %s", string(b))
+	}
+}