fix(responses): reject invalid SSE data JSON

Guard the openai-response streaming path against truncated/invalid SSE data payloads by validating data: JSON before forwarding; surface a 502 terminal error instead of letting clients crash with JSON parse errors.

sdk/api/handlers/handlers.go

@@ -716,6 +716,12 @@ func (h *BaseAPIHandler) ExecuteStreamWithAuthManager(ctx context.Context, handl
 					return
 				}
 				if len(chunk.Payload) > 0 {
+					if handlerType == "openai-response" {
+						if err := validateSSEDataJSON(chunk.Payload); err != nil {
+							_ = sendErr(&interfaces.ErrorMessage{StatusCode: http.StatusBadGateway, Error: err})
+							return
+						}
+					}
 					sentPayload = true
 					if okSendData := sendData(cloneBytes(chunk.Payload)); !okSendData {
 						return
@@ -727,6 +733,35 @@ func (h *BaseAPIHandler) ExecuteStreamWithAuthManager(ctx context.Context, handl
 	return dataChan, upstreamHeaders, errChan
 }
 
+func validateSSEDataJSON(chunk []byte) error {
+	for _, line := range bytes.Split(chunk, []byte("\n")) {
+		line = bytes.TrimSpace(line)
+		if len(line) == 0 {
+			continue
+		}
+		if !bytes.HasPrefix(line, []byte("data:")) {
+			continue
+		}
+		data := bytes.TrimSpace(line[5:])
+		if len(data) == 0 {
+			continue
+		}
+		if bytes.Equal(data, []byte("[DONE]")) {
+			continue
+		}
+		if json.Valid(data) {
+			continue
+		}
+		const max = 512
+		preview := data
+		if len(preview) > max {
+			preview = preview[:max]
+		}
+		return fmt.Errorf("invalid SSE data JSON (len=%d): %q", len(data), preview)
+	}
+	return nil
+}
+
 func statusFromError(err error) int {
 	if err == nil {
 		return 0

sdk/api/handlers/handlers_stream_bootstrap_test.go

@@ -134,6 +134,37 @@ type authAwareStreamExecutor struct {
 	authIDs []string
 }
 
+type invalidJSONStreamExecutor struct{}
+
+func (e *invalidJSONStreamExecutor) Identifier() string { return "codex" }
+
+func (e *invalidJSONStreamExecutor) Execute(context.Context, *coreauth.Auth, coreexecutor.Request, coreexecutor.Options) (coreexecutor.Response, error) {
+	return coreexecutor.Response{}, &coreauth.Error{Code: "not_implemented", Message: "Execute not implemented"}
+}
+
+func (e *invalidJSONStreamExecutor) ExecuteStream(context.Context, *coreauth.Auth, coreexecutor.Request, coreexecutor.Options) (*coreexecutor.StreamResult, error) {
+	ch := make(chan coreexecutor.StreamChunk, 1)
+	ch <- coreexecutor.StreamChunk{Payload: []byte("event: response.completed\ndata: {\"type\"")}
+	close(ch)
+	return &coreexecutor.StreamResult{Chunks: ch}, nil
+}
+
+func (e *invalidJSONStreamExecutor) Refresh(ctx context.Context, auth *coreauth.Auth) (*coreauth.Auth, error) {
+	return auth, nil
+}
+
+func (e *invalidJSONStreamExecutor) CountTokens(context.Context, *coreauth.Auth, coreexecutor.Request, coreexecutor.Options) (coreexecutor.Response, error) {
+	return coreexecutor.Response{}, &coreauth.Error{Code: "not_implemented", Message: "CountTokens not implemented"}
+}
+
+func (e *invalidJSONStreamExecutor) HttpRequest(ctx context.Context, auth *coreauth.Auth, req *http.Request) (*http.Response, error) {
+	return nil, &coreauth.Error{
+		Code:       "not_implemented",
+		Message:    "HttpRequest not implemented",
+		HTTPStatus: http.StatusNotImplemented,
+	}
+}
+
 func (e *authAwareStreamExecutor) Identifier() string { return "codex" }
 
 func (e *authAwareStreamExecutor) Execute(context.Context, *coreauth.Auth, coreexecutor.Request, coreexecutor.Options) (coreexecutor.Response, error) {
@@ -524,3 +555,55 @@ func TestExecuteStreamWithAuthManager_SelectedAuthCallbackReceivesAuthID(t *test
 		t.Fatalf("selectedAuthID = %q, want %q", selectedAuthID, "auth2")
 	}
 }
+
+func TestExecuteStreamWithAuthManager_ValidatesOpenAIResponsesStreamDataJSON(t *testing.T) {
+	executor := &invalidJSONStreamExecutor{}
+	manager := coreauth.NewManager(nil, nil, nil)
+	manager.RegisterExecutor(executor)
+
+	auth1 := &coreauth.Auth{
+		ID:       "auth1",
+		Provider: "codex",
+		Status:   coreauth.StatusActive,
+		Metadata: map[string]any{"email": "test1@example.com"},
+	}
+	if _, err := manager.Register(context.Background(), auth1); err != nil {
+		t.Fatalf("manager.Register(auth1): %v", err)
+	}
+
+	registry.GetGlobalRegistry().RegisterClient(auth1.ID, auth1.Provider, []*registry.ModelInfo{{ID: "test-model"}})
+	t.Cleanup(func() {
+		registry.GetGlobalRegistry().UnregisterClient(auth1.ID)
+	})
+
+	handler := NewBaseAPIHandlers(&sdkconfig.SDKConfig{}, manager)
+	dataChan, _, errChan := handler.ExecuteStreamWithAuthManager(context.Background(), "openai-response", "test-model", []byte(`{"model":"test-model"}`), "")
+	if dataChan == nil || errChan == nil {
+		t.Fatalf("expected non-nil channels")
+	}
+
+	var got []byte
+	for chunk := range dataChan {
+		got = append(got, chunk...)
+	}
+	if len(got) != 0 {
+		t.Fatalf("expected empty payload, got %q", string(got))
+	}
+
+	gotErr := false
+	for msg := range errChan {
+		if msg == nil {
+			continue
+		}
+		if msg.StatusCode != http.StatusBadGateway {
+			t.Fatalf("expected status %d, got %d", http.StatusBadGateway, msg.StatusCode)
+		}
+		if msg.Error == nil {
+			t.Fatalf("expected error")
+		}
+		gotErr = true
+	}
+	if !gotErr {
+		t.Fatalf("expected terminal error")
+	}
+}