feat: add unit tests for OpenAI responses request conversion

- Introduced a new test file for validating the conversion of OpenAI responses to chat completions.
- Implemented tests to ensure correct merging of consecutive function calls and proper handling of interrupted function calls.
- Enhanced the main conversion function to buffer consecutive function calls and emit them as a single assistant message.

internal/translator/openai/openai/responses/openai_openai-responses_request.go

@@ -57,11 +57,25 @@ func ConvertOpenAIResponsesRequestToOpenAIChatCompletions(modelName string, inpu
 
 	// Convert input array to messages
 	if input := root.Get("input"); input.Exists() && input.IsArray() {
+		pendingToolCalls := make([]interface{}, 0)
+		flushPendingToolCalls := func() {
+			if len(pendingToolCalls) == 0 {
+				return
+			}
+			assistantMessage := []byte(`{"role":"assistant","tool_calls":[]}`)
+			assistantMessage, _ = sjson.SetBytes(assistantMessage, "tool_calls", pendingToolCalls)
+			out, _ = sjson.SetRawBytes(out, "messages.-1", assistantMessage)
+			pendingToolCalls = pendingToolCalls[:0]
+		}
+
 		input.ForEach(func(_, item gjson.Result) bool {
 			itemType := item.Get("type").String()
 			if itemType == "" && item.Get("role").String() != "" {
 				itemType = "message"
 			}
+			if itemType != "function_call" {
+				flushPendingToolCalls()
+			}
 
 			switch itemType {
 			case "message", "":
@@ -112,9 +126,7 @@ func ConvertOpenAIResponsesRequestToOpenAIChatCompletions(modelName string, inpu
 				out, _ = sjson.SetRawBytes(out, "messages.-1", message)
 
 			case "function_call":
-				// Handle function call conversion to assistant message with tool_calls
-				assistantMessage := []byte(`{"role":"assistant","tool_calls":[]}`)
-
+				// Buffer consecutive function calls and emit them as one assistant message.
 				toolCall := []byte(`{"id":"","type":"function","function":{"name":"","arguments":""}}`)
 
 				if callId := item.Get("call_id"); callId.Exists() {
@@ -128,9 +140,7 @@ func ConvertOpenAIResponsesRequestToOpenAIChatCompletions(modelName string, inpu
 				if arguments := item.Get("arguments"); arguments.Exists() {
 					toolCall, _ = sjson.SetBytes(toolCall, "function.arguments", arguments.String())
 				}
-
-				assistantMessage, _ = sjson.SetRawBytes(assistantMessage, "tool_calls.0", toolCall)
-				out, _ = sjson.SetRawBytes(out, "messages.-1", assistantMessage)
+				pendingToolCalls = append(pendingToolCalls, gjson.ParseBytes(toolCall).Value())
 
 			case "function_call_output":
 				// Handle function call output conversion to tool message
@@ -149,6 +159,7 @@ func ConvertOpenAIResponsesRequestToOpenAIChatCompletions(modelName string, inpu
 
 			return true
 		})
+		flushPendingToolCalls()
 	} else if input.Type == gjson.String {
 		msg := []byte(`{}`)
 		msg, _ = sjson.SetBytes(msg, "role", "user")

internal/translator/openai/openai/responses/openai_openai-responses_request_test.go

@@ -0,0 +1,87 @@
+package responses
+
+import (
+	"bytes"
+	"encoding/json"
+	"testing"
+
+	"github.com/tidwall/gjson"
+)
+
+func prettyJSONForTest(raw []byte) string {
+	if !gjson.ValidBytes(raw) {
+		return string(raw)
+	}
+	var out bytes.Buffer
+	if err := json.Indent(&out, raw, "", "  "); err != nil {
+		return string(raw)
+	}
+	return out.String()
+}
+
+func TestConvertOpenAIResponsesRequestToOpenAIChatCompletions_MergeConsecutiveFunctionCalls(t *testing.T) {
+	raw := []byte(`{
+		"input": [
+			{"type":"function_call","call_id":"exec_command:0","name":"exec_command","arguments":"{\"cmd\":\"ls\"}"},
+			{"type":"function_call","call_id":"exec_command:1","name":"exec_command","arguments":"{\"cmd\":\"pwd\"}"},
+			{"type":"function_call_output","call_id":"exec_command:0","output":"ok0"},
+			{"type":"function_call_output","call_id":"exec_command:1","output":"ok1"}
+		]
+	}`)
+	t.Logf("input json:\n%s", prettyJSONForTest(raw))
+
+	out := ConvertOpenAIResponsesRequestToOpenAIChatCompletions("kimi-k2.6", raw, true)
+	t.Logf("output json:\n%s", prettyJSONForTest(out))
+
+	msgs := gjson.GetBytes(out, "messages")
+	if !msgs.Exists() || !msgs.IsArray() {
+		t.Fatalf("messages should be an array")
+	}
+	if got := len(msgs.Array()); got != 3 {
+		t.Fatalf("messages count = %d, want %d", got, 3)
+	}
+
+	if got := gjson.GetBytes(out, "messages.0.role").String(); got != "assistant" {
+		t.Fatalf("messages.0.role = %q, want %q", got, "assistant")
+	}
+	if got := len(gjson.GetBytes(out, "messages.0.tool_calls").Array()); got != 2 {
+		t.Fatalf("messages.0.tool_calls length = %d, want %d", got, 2)
+	}
+	if got := gjson.GetBytes(out, "messages.0.tool_calls.0.id").String(); got != "exec_command:0" {
+		t.Fatalf("messages.0.tool_calls.0.id = %q, want %q", got, "exec_command:0")
+	}
+	if got := gjson.GetBytes(out, "messages.0.tool_calls.1.id").String(); got != "exec_command:1" {
+		t.Fatalf("messages.0.tool_calls.1.id = %q, want %q", got, "exec_command:1")
+	}
+
+	if got := gjson.GetBytes(out, "messages.1.tool_call_id").String(); got != "exec_command:0" {
+		t.Fatalf("messages.1.tool_call_id = %q, want %q", got, "exec_command:0")
+	}
+	if got := gjson.GetBytes(out, "messages.2.tool_call_id").String(); got != "exec_command:1" {
+		t.Fatalf("messages.2.tool_call_id = %q, want %q", got, "exec_command:1")
+	}
+}
+
+func TestConvertOpenAIResponsesRequestToOpenAIChatCompletions_SplitFunctionCallsWhenInterrupted(t *testing.T) {
+	raw := []byte(`{
+		"input": [
+			{"type":"function_call","call_id":"call_a","name":"tool_a","arguments":"{}"},
+			{"type":"message","role":"user","content":"next"},
+			{"type":"function_call","call_id":"call_b","name":"tool_b","arguments":"{}"}
+		]
+	}`)
+	t.Logf("input json:\n%s", prettyJSONForTest(raw))
+
+	out := ConvertOpenAIResponsesRequestToOpenAIChatCompletions("kimi-k2.6", raw, false)
+	t.Logf("output json:\n%s", prettyJSONForTest(out))
+
+	if got := len(gjson.GetBytes(out, "messages").Array()); got != 3 {
+		t.Fatalf("messages count = %d, want %d", got, 3)
+	}
+	if got := gjson.GetBytes(out, "messages.0.tool_calls.0.id").String(); got != "call_a" {
+		t.Fatalf("messages.0.tool_calls.0.id = %q, want %q", got, "call_a")
+	}
+	if got := gjson.GetBytes(out, "messages.2.tool_calls.0.id").String(); got != "call_b" {
+		t.Fatalf("messages.2.tool_calls.0.id = %q, want %q", got, "call_b")
+	}
+}