fix: stabilize API key Codex manifest refreshes

backend/internal/handler/openai_codex_models_handler.go

@@ -16,9 +16,12 @@ import (
 // GET {base_url}/models?client_version=... (custom provider mode) or
 // GET /backend-api/codex/models (chatgpt_base_url mode). Both routes land
 // here. The manifest is proxied verbatim from the selected account's ChatGPT
-// backend or custom API key upstream, so clients pointed at the gateway see an
-// always-current manifest instead of a frozen local cache.
+// backend or custom API key upstream. API key manifests use a short-lived,
+// asynchronously revalidated cache to tolerate canceled client requests.
 func (h *OpenAIGatewayHandler) CodexModels(c *gin.Context) {
+	if c.Request.Context().Err() != nil {
+		return
+	}
 	apiKey, ok := middleware2.GetAPIKeyFromContext(c)
 	if !ok || apiKey.Group == nil {
 		h.errorResponse(c, http.StatusUnauthorized, "invalid_request_error", "API key group is required")
@@ -31,15 +34,24 @@ func (h *OpenAIGatewayHandler) CodexModels(c *gin.Context) {
 
 	account, err := h.gatewayService.SelectAccountForModel(c.Request.Context(), apiKey.GroupID, "", "")
 	if err != nil {
+		if c.Request.Context().Err() != nil {
+			return
+		}
 		h.errorResponse(c, http.StatusServiceUnavailable, "upstream_error", "No available OpenAI accounts")
 		return
 	}
 
 	manifest, err := h.gatewayService.FetchCodexModelsManifest(c.Request.Context(), account, c.Query("client_version"), c.GetHeader("If-None-Match"))
 	if err != nil {
+		if c.Request.Context().Err() != nil {
+			return
+		}
 		h.errorResponse(c, infraerrors.Code(err), "upstream_error", infraerrors.Message(err))
 		return
 	}
+	if c.Request.Context().Err() != nil {
+		return
+	}
 
 	if manifest.ETag != "" {
 		c.Header("ETag", manifest.ETag)

backend/internal/handler/openai_codex_models_handler_test.go

@@ -0,0 +1,26 @@
+package handler
+
+import (
+	"context"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+)
+
+func TestCodexModelsCanceledRequestDoesNotWriteResponse(t *testing.T) {
+	gin.SetMode(gin.TestMode)
+	recorder := httptest.NewRecorder()
+	c, _ := gin.CreateTestContext(recorder)
+	ctx, cancel := context.WithCancel(context.Background())
+	cancel()
+	c.Request = httptest.NewRequest(http.MethodGet, "/v1/models", nil).WithContext(ctx)
+
+	h := &OpenAIGatewayHandler{}
+	h.CodexModels(c)
+
+	if c.Writer.Written() {
+		t.Fatalf("canceled request wrote an HTTP response: status=%d body=%q", recorder.Code, recorder.Body.String())
+	}
+}