diff --git a/internal/translator/openai/claude/openai_claude_request.go b/internal/translator/openai/claude/openai_claude_request.go
index 7ff7a582..5a769ca4 100644
--- a/internal/translator/openai/claude/openai_claude_request.go
+++ b/internal/translator/openai/claude/openai_claude_request.go
@@ -103,25 +103,41 @@ func ConvertClaudeRequestToOpenAI(modelName string, inputRawJSON []byte, stream
 	// Handle system message first
 	systemMsgJSON := []byte(`{"role":"system","content":[]}`)
 	hasSystemContent := false
-	if system := root.Get("system"); system.Exists() {
-		if system.Type == gjson.String {
-			if system.String() != "" && !util.IsClaudeCodeAttributionSystemText(system.String()) {
-				oldSystem := []byte(`{"type":"text","text":""}`)
-				oldSystem, _ = sjson.SetBytes(oldSystem, "text", system.String())
-				systemMsgJSON, _ = sjson.SetRawBytes(systemMsgJSON, "content.-1", oldSystem)
-				hasSystemContent = true
-			}
-		} else if system.Type == gjson.JSON {
-			if system.IsArray() {
-				systemResults := system.Array()
-				for i := 0; i < len(systemResults); i++ {
-					if contentItem, ok := convertClaudeContentPart(systemResults[i]); ok {
-						systemMsgJSON, _ = sjson.SetRawBytes(systemMsgJSON, "content.-1", []byte(contentItem))
-						hasSystemContent = true
-					}
-				}
-			}
+	appendSystemContent := func(content gjson.Result) {
+		if !content.Exists() {
+			return
 		}
+		if content.Type == gjson.String {
+			if content.String() == "" || util.IsClaudeCodeAttributionSystemText(content.String()) {
+				return
+			}
+			oldSystem := []byte(`{"type":"text","text":""}`)
+			oldSystem, _ = sjson.SetBytes(oldSystem, "text", content.String())
+			systemMsgJSON, _ = sjson.SetRawBytes(systemMsgJSON, "content.-1", oldSystem)
+			hasSystemContent = true
+			return
+		}
+		if content.IsArray() {
+			content.ForEach(func(_, item gjson.Result) bool {
+				if contentItem, ok := convertClaudeContentPart(item); ok {
+					systemMsgJSON, _ = sjson.SetRawBytes(systemMsgJSON, "content.-1", []byte(contentItem))
+					hasSystemContent = true
+				}
+				return true
+			})
+		}
+	}
+
+	if system := root.Get("system"); system.Exists() {
+		appendSystemContent(system)
+	}
+	if messages := root.Get("messages"); messages.Exists() && messages.IsArray() {
+		messages.ForEach(func(_, message gjson.Result) bool {
+			if message.Get("role").String() == "system" {
+				appendSystemContent(message.Get("content"))
+			}
+			return true
+		})
 	}
 	// Only add system message if it has content
 	if hasSystemContent {
@@ -132,6 +148,9 @@ func ConvertClaudeRequestToOpenAI(modelName string, inputRawJSON []byte, stream
 	if messages := root.Get("messages"); messages.Exists() && messages.IsArray() {
 		messages.ForEach(func(_, message gjson.Result) bool {
 			role := message.Get("role").String()
+			if role == "system" {
+				return true
+			}
 			contentResult := message.Get("content")
 
 			// Handle content
diff --git a/internal/translator/openai/claude/openai_claude_request_test.go b/internal/translator/openai/claude/openai_claude_request_test.go
index 9e2d771a..34de754d 100644
--- a/internal/translator/openai/claude/openai_claude_request_test.go
+++ b/internal/translator/openai/claude/openai_claude_request_test.go
@@ -2,6 +2,7 @@ package claude
 
 import (
 	"encoding/base64"
+	"fmt"
 	"testing"
 
 	"github.com/tidwall/gjson"
@@ -356,6 +357,47 @@ func validGPTChatReasoningSignature() string {
 	return base64.URLEncoding.EncodeToString(raw)
 }
 
+func TestConvertClaudeRequestToOpenAI_MidConversationSystemMessagesMoveToInitialSystem(t *testing.T) {
+	inputJSON := `{
+		"model": "claude-sonnet-4-5",
+		"system": [{"type": "text", "text": "Top-level rules"}],
+		"messages": [
+			{"role": "user", "content": [{"type": "text", "text": "Hello"}]},
+			{"role": "system", "content": "String mid-conversation rule"},
+			{"role": "assistant", "content": [{"type": "text", "text": "Hi there"}]},
+			{"role": "system", "content": [{"type": "text", "text": "Array mid-conversation rule"}]},
+			{"role": "user", "content": [{"type": "text", "text": "Follow up"}]}
+		]
+	}`
+
+	result := ConvertClaudeRequestToOpenAI("gpt-5", []byte(inputJSON), false)
+	resultJSON := gjson.ParseBytes(result)
+	messages := resultJSON.Get("messages").Array()
+
+	if len(messages) != 4 {
+		t.Fatalf("Expected 4 messages, got %d: %s", len(messages), resultJSON.Get("messages").Raw)
+	}
+
+	roles := make([]string, 0, len(messages))
+	for _, message := range messages {
+		roles = append(roles, message.Get("role").String())
+	}
+	if got, want := roles, []string{"system", "user", "assistant", "user"}; fmt.Sprintf("%v", got) != fmt.Sprintf("%v", want) {
+		t.Fatalf("Unexpected message roles: got %v, want %v", got, want)
+	}
+
+	systemContent := messages[0].Get("content").Array()
+	if len(systemContent) != 3 {
+		t.Fatalf("Expected 3 system content items, got %d: %s", len(systemContent), messages[0].Get("content").Raw)
+	}
+	wantTexts := []string{"Top-level rules", "String mid-conversation rule", "Array mid-conversation rule"}
+	for i, want := range wantTexts {
+		if got := systemContent[i].Get("text").String(); got != want {
+			t.Fatalf("system content[%d] = %q, want %q", i, got, want)
+		}
+	}
+}
+
 func TestConvertClaudeRequestToOpenAI_SystemMessageScenarios(t *testing.T) {
 	tests := []struct {
 		name        string