diff --git a/internal/translator/codex/openai/chat-completions/codex_openai_response.go b/internal/translator/codex/openai/chat-completions/codex_openai_response.go
index f0e264c8..0054d995 100644
--- a/internal/translator/codex/openai/chat-completions/codex_openai_response.go
+++ b/internal/translator/codex/openai/chat-completions/codex_openai_response.go
@@ -74,8 +74,13 @@ func ConvertCodexResponseToOpenAI(_ context.Context, modelName string, originalR
 	}
 
 	// Extract and set the model version.
+	cachedModel := (*param).(*ConvertCliToOpenAIParams).Model
 	if modelResult := gjson.GetBytes(rawJSON, "model"); modelResult.Exists() {
 		template, _ = sjson.Set(template, "model", modelResult.String())
+	} else if cachedModel != "" {
+		template, _ = sjson.Set(template, "model", cachedModel)
+	} else if modelName != "" {
+		template, _ = sjson.Set(template, "model", modelName)
 	}
 
 	template, _ = sjson.Set(template, "created", (*param).(*ConvertCliToOpenAIParams).CreatedAt)
diff --git a/internal/translator/codex/openai/chat-completions/codex_openai_response_test.go b/internal/translator/codex/openai/chat-completions/codex_openai_response_test.go
new file mode 100644
index 00000000..70aaea06
--- /dev/null
+++ b/internal/translator/codex/openai/chat-completions/codex_openai_response_test.go
@@ -0,0 +1,47 @@
+package chat_completions
+
+import (
+	"context"
+	"testing"
+
+	"github.com/tidwall/gjson"
+)
+
+func TestConvertCodexResponseToOpenAI_StreamSetsModelFromResponseCreated(t *testing.T) {
+	ctx := context.Background()
+	var param any
+
+	modelName := "gpt-5.3-codex"
+
+	out := ConvertCodexResponseToOpenAI(ctx, modelName, nil, nil, []byte(`data: {"type":"response.created","response":{"id":"resp_123","created_at":1700000000,"model":"gpt-5.3-codex"}}`), &param)
+	if len(out) != 0 {
+		t.Fatalf("expected no output for response.created, got %d chunks", len(out))
+	}
+
+	out = ConvertCodexResponseToOpenAI(ctx, modelName, nil, nil, []byte(`data: {"type":"response.output_text.delta","delta":"hello"}`), &param)
+	if len(out) != 1 {
+		t.Fatalf("expected 1 chunk, got %d", len(out))
+	}
+
+	gotModel := gjson.Get(out[0], "model").String()
+	if gotModel != modelName {
+		t.Fatalf("expected model %q, got %q", modelName, gotModel)
+	}
+}
+
+func TestConvertCodexResponseToOpenAI_FirstChunkUsesRequestModelName(t *testing.T) {
+	ctx := context.Background()
+	var param any
+
+	modelName := "gpt-5.3-codex"
+
+	out := ConvertCodexResponseToOpenAI(ctx, modelName, nil, nil, []byte(`data: {"type":"response.output_text.delta","delta":"hello"}`), &param)
+	if len(out) != 1 {
+		t.Fatalf("expected 1 chunk, got %d", len(out))
+	}
+
+	gotModel := gjson.Get(out[0], "model").String()
+	if gotModel != modelName {
+		t.Fatalf("expected model %q, got %q", modelName, gotModel)
+	}
+}