expose openai_responses API style to C and Go bindings

2 files changed, 67 insertions, 3 deletions

diff --git a/libpanto-go/panto.go b/libpanto-go/panto.go
index 35bc5fa..30caaca 100644
--- a/libpanto-go/panto.go
+++ b/libpanto-go/panto.go
@@ -57,8 +57,10 @@ type (
 // drift from the ABI: if a variant is inserted in panto.h, the values shift
 // with it instead of desyncing. Keep one Go constant per C value.
 const (
-	OpenAIChat        APIStyle = APIStyle(C.PANTO_OPENAI_CHAT)
-	AnthropicMessages APIStyle = APIStyle(C.PANTO_ANTHROPIC_MESSAGES)
+	OpenAIChat           APIStyle = APIStyle(C.PANTO_OPENAI_CHAT)
+	AnthropicMessages    APIStyle = APIStyle(C.PANTO_ANTHROPIC_MESSAGES)
+	OpenAIResponses      APIStyle = APIStyle(C.PANTO_OPENAI_RESPONSES)
+	OpenAICodexResponses APIStyle = APIStyle(C.PANTO_OPENAI_CODEX_RESPONSES)
 )
 
 const (
@@ -126,12 +128,18 @@ type Config struct {
 type ProviderConfig struct {
 	OpenAIChat        *OpenAIChatConfig
 	AnthropicMessages *AnthropicMessagesConfig
+	OpenAIResponses   *OpenAIResponsesConfig
 }
 type OpenAIChatConfig struct {
 	APIKey, BaseURL, Model string
 	Reasoning              ReasoningEffort
 	MaxTokens              uint32
 }
+type OpenAIResponsesConfig struct {
+	APIKey, BaseURL, Model string
+	Reasoning              ReasoningEffort
+	MaxTokens              uint32
+}
 type AnthropicMessagesConfig struct {
 	APIKey, BaseURL, Model, APIVersion string
 	MaxTokens                          uint32
@@ -1106,7 +1114,17 @@ func (cfg Config) c() (C.PantoConfig, cStrings, error) {
 func (p ProviderConfig) c() (C.PantoProviderConfig, cStrings, error) {
 	var out C.PantoProviderConfig
 	var cs cStrings
-	if p.OpenAIChat != nil == (p.AnthropicMessages != nil) {
+	n := 0
+	if p.OpenAIChat != nil {
+		n++
+	}
+	if p.AnthropicMessages != nil {
+		n++
+	}
+	if p.OpenAIResponses != nil {
+		n++
+	}
+	if n != 1 {
 		return out, nil, errors.New("exactly one provider config must be set")
 	}
 	if p.OpenAIChat != nil {
@@ -1114,6 +1132,11 @@ func (p ProviderConfig) c() (C.PantoProviderConfig, cStrings, error) {
 		setOpenAI(&out, p.OpenAIChat, &cs)
 		return out, cs, nil
 	}
+	if p.OpenAIResponses != nil {
+		out.tag = C.PANTO_OPENAI_RESPONSES
+		setOpenAIResponses(&out, p.OpenAIResponses, &cs)
+		return out, cs, nil
+	}
 	out.tag = C.PANTO_ANTHROPIC_MESSAGES
 	setAnthropic(&out, p.AnthropicMessages, &cs)
 	return out, cs, nil
@@ -1130,6 +1153,17 @@ func setOpenAI(out *C.PantoProviderConfig, cfg *OpenAIChatConfig, cs *cStrings)
 	c.max_tokens = C.uint32_t(cfg.MaxTokens)
 }
 
+func setOpenAIResponses(out *C.PantoProviderConfig, cfg *OpenAIResponsesConfig, cs *cStrings) {
+	apiKey, baseURL, model := C.CString(cfg.APIKey), C.CString(cfg.BaseURL), C.CString(cfg.Model)
+	*cs = append(*cs, apiKey, baseURL, model)
+	c := (*C.PantoOpenAIResponsesConfig)(unsafe.Pointer(&out.data[0]))
+	c.api_key = apiKey
+	c.base_url = baseURL
+	c.model = model
+	c.reasoning = C.PantoReasoningEffort(cfg.Reasoning)
+	c.max_tokens = C.uint32_t(cfg.MaxTokens)
+}
+
 func setAnthropic(out *C.PantoProviderConfig, cfg *AnthropicMessagesConfig, cs *cStrings) {
 	apiKey, baseURL, model, ver := C.CString(cfg.APIKey), C.CString(cfg.BaseURL), C.CString(cfg.Model), C.CString(cfg.APIVersion)
 	*cs = append(*cs, apiKey, baseURL, model, ver)
diff --git a/libpanto-go/panto_test.go b/libpanto-go/panto_test.go
index af8cafc..1270ead 100644
--- a/libpanto-go/panto_test.go
+++ b/libpanto-go/panto_test.go
@@ -164,6 +164,36 @@ func testConfig() Config {
 	}
 }
 
+func TestOpenAIResponsesProviderConfigPassesThrough(t *testing.T) {
+	provider := ProviderConfig{
+		OpenAIResponses: &OpenAIResponsesConfig{
+			APIKey:    "test-key",
+			BaseURL:   "http://localhost",
+			Model:     "test-model",
+			Reasoning: ReasoningMedium,
+			MaxTokens: 128,
+		},
+	}
+	c, strings, err := provider.c()
+	if err != nil {
+		t.Fatalf("ProviderConfig.c: %v", err)
+	}
+	defer strings.free()
+
+	if APIStyle(c.tag) != OpenAIResponses {
+		t.Fatalf("tag = %v, want %v", APIStyle(c.tag), OpenAIResponses)
+	}
+
+	Init()
+	defer Deinit()
+
+	a, err := NewAgent(Config{Provider: provider})
+	if err != nil {
+		t.Fatalf("NewAgent: %v", err)
+	}
+	defer a.Close()
+}
+
 func TestNewAgentSetSystemPromptDoesNotCrash(t *testing.T) {
 	Init()
 	defer Deinit()