feat(provider): support chat completions for openai providers

pkg/providers/http_provider.go

@@ -31,6 +31,7 @@ type HTTPProvider struct {
 	apiBase                  string
 	defaultModel             string
 	supportsResponsesCompact bool
+	responsesAPI             string
 	authMode                 string
 	timeout                  time.Duration
 	httpClient               *http.Client
@@ -48,6 +49,7 @@ func NewHTTPProvider(providerName, apiKey, apiBase, defaultModel string, support
 		apiBase:                  normalizedBase,
 		defaultModel:             strings.TrimSpace(defaultModel),
 		supportsResponsesCompact: supportsResponsesCompact,
+		responsesAPI:             "responses",
 		authMode:                 authMode,
 		timeout:                  timeout,
 		httpClient:               &http.Client{Timeout: timeout},
@@ -79,7 +81,7 @@ func (p *HTTPProvider) Chat(ctx context.Context, messages []Message, tools []Too
 	if !json.Valid(body) {
 		return nil, fmt.Errorf("API error (status %d, content-type %q): non-JSON response: %s", statusCode, contentType, previewResponseBody(body))
 	}
-	if p.useOpenAICompatChatUpstream() {
+	if p.useOpenAICompatChatUpstream() || p.useConfiguredOpenAICompatChat() {
 		return parseOpenAICompatResponse(body)
 	}
 	return parseResponsesAPIResponse(body)
@@ -102,7 +104,7 @@ func (p *HTTPProvider) ChatStream(ctx context.Context, messages []Message, tools
 	if !json.Valid(body) {
 		return nil, fmt.Errorf("API error (status %d, content-type %q): non-JSON response: %s", status, ctype, previewResponseBody(body))
 	}
-	if p.useOpenAICompatChatUpstream() {
+	if p.useOpenAICompatChatUpstream() || p.useConfiguredOpenAICompatChat() {
 		return parseOpenAICompatResponse(body)
 	}
 	return parseResponsesAPIResponse(body)

pkg/providers/openai_compat_adapter.go

@@ -112,6 +112,18 @@ func (p *HTTPProvider) useOpenAICompatChatUpstream() bool {
 	}
 }
 
+func (p *HTTPProvider) useConfiguredOpenAICompatChat() bool {
+	if p == nil {
+		return false
+	}
+	switch strings.ToLower(strings.TrimSpace(p.responsesAPI)) {
+	case "chat_completions":
+		return true
+	default:
+		return false
+	}
+}
+
 func (p *HTTPProvider) compatBase() string {
 	switch p.oauthProvider() {
 	case defaultQwenOAuthProvider:

pkg/providers/openai_compat_provider_test.go

@@ -1,6 +1,7 @@
 package providers
 
 import (
+	"encoding/json"
 	"net/http"
 	"net/http/httptest"
 	"strings"
@@ -180,3 +181,37 @@ func TestBuildOpenAICompatChatRequestStripsKimiPrefixAndSuffix(t *testing.T) {
 		t.Fatalf("reasoning_effort = %#v, want auto", got)
 	}
 }
+
+func TestHTTPProviderChatUsesConfiguredChatCompletionsAPI(t *testing.T) {
+	var gotPath string
+	var gotBody map[string]interface{}
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		gotPath = r.URL.Path
+		if err := json.NewDecoder(r.Body).Decode(&gotBody); err != nil {
+			t.Fatalf("decode request: %v", err)
+		}
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = w.Write([]byte(`{"choices":[{"message":{"content":"hello from chat"},"finish_reason":"stop"}],"usage":{"prompt_tokens":1,"completion_tokens":2,"total_tokens":3}}`))
+	}))
+	defer server.Close()
+
+	provider := NewHTTPProvider("openai", "token", server.URL+"/v1", "gpt-5", false, "api_key", 5*time.Second, nil)
+	provider.responsesAPI = "chat_completions"
+
+	resp, err := provider.Chat(t.Context(), []Message{{Role: "user", Content: "hi"}}, nil, "gpt-5", nil)
+	if err != nil {
+		t.Fatalf("Chat error: %v", err)
+	}
+	if gotPath != "/v1/chat/completions" {
+		t.Fatalf("path = %q, want /v1/chat/completions", gotPath)
+	}
+	if gotBody["model"] != "gpt-5" {
+		t.Fatalf("model = %#v, want gpt-5", gotBody["model"])
+	}
+	if resp.Content != "hello from chat" {
+		t.Fatalf("content = %q, want hello from chat", resp.Content)
+	}
+	if resp.Usage == nil || resp.Usage.TotalTokens != 3 {
+		t.Fatalf("usage = %#v, want total_tokens=3", resp.Usage)
+	}
+}

pkg/providers/provider_registry.go

@@ -116,7 +116,11 @@ func CreateProviderByName(cfg *config.Config, name string) (LLMProvider, error)
 	if oauthProvider == defaultIFlowOAuthProvider || strings.EqualFold(routeName, defaultIFlowOAuthProvider) {
 		return NewIFlowProvider(routeName, pc.APIKey, pc.APIBase, defaultModel, pc.SupportsResponsesCompact, pc.Auth, time.Duration(pc.TimeoutSec)*time.Second, oauth), nil
 	}
-	return NewHTTPProvider(routeName, pc.APIKey, pc.APIBase, defaultModel, pc.SupportsResponsesCompact, pc.Auth, time.Duration(pc.TimeoutSec)*time.Second, oauth), nil
+	provider := NewHTTPProvider(routeName, pc.APIKey, pc.APIBase, defaultModel, pc.SupportsResponsesCompact, pc.Auth, time.Duration(pc.TimeoutSec)*time.Second, oauth)
+	if api := strings.TrimSpace(pc.Responses.API); api != "" {
+		provider.responsesAPI = api
+	}
+	return provider, nil
 }
 
 func ProviderSupportsResponsesCompact(cfg *config.Config, name string) bool {

pkg/providers/responses_adapter.go

@@ -44,7 +44,7 @@ func (p *HTTPProvider) callResponses(ctx context.Context, messages []Message, to
 	if prevID, ok := stringOption(options, "responses_previous_response_id"); ok && prevID != "" {
 		requestBody["previous_response_id"] = prevID
 	}
-	if p.useOpenAICompatChatUpstream() {
+	if p.useOpenAICompatChatUpstream() || p.useConfiguredOpenAICompatChat() {
 		chatBody := p.buildOpenAICompatChatRequest(messages, tools, model, options)
 		return p.postJSON(ctx, endpointFor(p.compatBase(), "/chat/completions"), chatBody)
 	}
@@ -309,7 +309,7 @@ func (p *HTTPProvider) callResponsesStream(ctx context.Context, messages []Messa
 	if streamOpts, ok := mapOption(options, "responses_stream_options"); ok && len(streamOpts) > 0 {
 		requestBody["stream_options"] = streamOpts
 	}
-	if p.useOpenAICompatChatUpstream() {
+	if p.useOpenAICompatChatUpstream() || p.useConfiguredOpenAICompatChat() {
 		chatBody := p.buildOpenAICompatChatRequest(messages, tools, model, options)
 		chatBody["stream"] = true
 		streamOptions := map[string]interface{}{"include_usage": true}