feat: enhance message normalization for OpenAI tool calls and Claude system message tool injection

internal/format/openai/render.go

@@ -48,17 +48,9 @@ func BuildResponseObject(responseID, model, finalPrompt, finalThinking, finalTex
 	output := make([]any, 0, 2)
 	if len(detected) > 0 {
 		exposedOutputText = ""
-		toolCalls := make([]any, 0, len(detected))
-		for _, tc := range detected {
-			toolCalls = append(toolCalls, map[string]any{
-				"type":      "tool_call",
-				"name":      tc.Name,
-				"arguments": tc.Input,
-			})
-		}
 		output = append(output, map[string]any{
 			"type":       "tool_calls",
-			"tool_calls": toolCalls,
+			"tool_calls": util.FormatOpenAIToolCalls(detected),
 		})
 	} else {
 		content := []any{

internal/format/openai/render_test.go

@@ -0,0 +1,64 @@
+package openai
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestBuildResponseObjectToolCallsFollowChatShape(t *testing.T) {
+	obj := BuildResponseObject(
+		"resp_test",
+		"gpt-4o",
+		"prompt",
+		"",
+		`{"tool_calls":[{"name":"search","input":{"q":"golang"}}]}`,
+		[]string{"search"},
+	)
+
+	outputText, _ := obj["output_text"].(string)
+	if outputText != "" {
+		t.Fatalf("expected output_text to be hidden for tool calls, got %q", outputText)
+	}
+
+	output, _ := obj["output"].([]any)
+	if len(output) != 1 {
+		t.Fatalf("expected one tool_calls wrapper, got %#v", obj["output"])
+	}
+
+	first, _ := output[0].(map[string]any)
+	if first["type"] != "tool_calls" {
+		t.Fatalf("expected first output item type tool_calls, got %#v", first["type"])
+	}
+	var toolCalls []map[string]any
+	switch v := first["tool_calls"].(type) {
+	case []map[string]any:
+		toolCalls = v
+	case []any:
+		toolCalls = make([]map[string]any, 0, len(v))
+		for _, item := range v {
+			m, _ := item.(map[string]any)
+			if m != nil {
+				toolCalls = append(toolCalls, m)
+			}
+		}
+	}
+	if len(toolCalls) != 1 {
+		t.Fatalf("expected one tool call, got %#v", first["tool_calls"])
+	}
+	tc := toolCalls[0]
+	if tc["type"] != "function" || tc["id"] == "" {
+		t.Fatalf("unexpected tool call shape: %#v", tc)
+	}
+	fn, _ := tc["function"].(map[string]any)
+	if fn["name"] != "search" {
+		t.Fatalf("unexpected function name: %#v", fn["name"])
+	}
+	argsRaw, _ := fn["arguments"].(string)
+	var args map[string]any
+	if err := json.Unmarshal([]byte(argsRaw), &args); err != nil {
+		t.Fatalf("arguments should be valid json string, got=%q err=%v", argsRaw, err)
+	}
+	if args["q"] != "golang" {
+		t.Fatalf("unexpected arguments: %#v", args)
+	}
+}