fix: fall back on model support errors during auth rotation

sdk/cliproxy/auth/openai_compat_pool_test.go

@@ -243,6 +243,75 @@ func TestManagerExecute_OpenAICompatAliasPoolStopsOnBadRequest(t *testing.T) {
 		t.Fatalf("execute calls = %v, want only first invalid model", got)
 	}
 }
+
+func TestManagerExecute_OpenAICompatAliasPoolFallsBackOnModelSupportBadRequest(t *testing.T) {
+	alias := "claude-opus-4.66"
+	modelSupportErr := &Error{
+		HTTPStatus: http.StatusBadRequest,
+		Message:    "invalid_request_error: The requested model is not supported.",
+	}
+	executor := &openAICompatPoolExecutor{
+		id:            "pool",
+		executeErrors: map[string]error{"qwen3.5-plus": modelSupportErr},
+	}
+	m := newOpenAICompatPoolTestManager(t, alias, []internalconfig.OpenAICompatibilityModel{
+		{Name: "qwen3.5-plus", Alias: alias},
+		{Name: "glm-5", Alias: alias},
+	}, executor)
+
+	resp, err := m.Execute(context.Background(), []string{"pool"}, cliproxyexecutor.Request{Model: alias}, cliproxyexecutor.Options{})
+	if err != nil {
+		t.Fatalf("execute error = %v, want fallback success", err)
+	}
+	if string(resp.Payload) != "glm-5" {
+		t.Fatalf("payload = %q, want %q", string(resp.Payload), "glm-5")
+	}
+	got := executor.ExecuteModels()
+	want := []string{"qwen3.5-plus", "glm-5"}
+	if len(got) != len(want) {
+		t.Fatalf("execute calls = %v, want %v", got, want)
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("execute call %d model = %q, want %q", i, got[i], want[i])
+		}
+	}
+}
+
+func TestManagerExecute_OpenAICompatAliasPoolFallsBackOnModelSupportUnprocessableEntity(t *testing.T) {
+	alias := "claude-opus-4.66"
+	modelSupportErr := &Error{
+		HTTPStatus: http.StatusUnprocessableEntity,
+		Message:    "The requested model is not supported.",
+	}
+	executor := &openAICompatPoolExecutor{
+		id:            "pool",
+		executeErrors: map[string]error{"qwen3.5-plus": modelSupportErr},
+	}
+	m := newOpenAICompatPoolTestManager(t, alias, []internalconfig.OpenAICompatibilityModel{
+		{Name: "qwen3.5-plus", Alias: alias},
+		{Name: "glm-5", Alias: alias},
+	}, executor)
+
+	resp, err := m.Execute(context.Background(), []string{"pool"}, cliproxyexecutor.Request{Model: alias}, cliproxyexecutor.Options{})
+	if err != nil {
+		t.Fatalf("execute error = %v, want fallback success", err)
+	}
+	if string(resp.Payload) != "glm-5" {
+		t.Fatalf("payload = %q, want %q", string(resp.Payload), "glm-5")
+	}
+	got := executor.ExecuteModels()
+	want := []string{"qwen3.5-plus", "glm-5"}
+	if len(got) != len(want) {
+		t.Fatalf("execute calls = %v, want %v", got, want)
+	}
+	for i := range want {
+		if got[i] != want[i] {
+			t.Fatalf("execute call %d model = %q, want %q", i, got[i], want[i])
+		}
+	}
+}
+
 func TestManagerExecute_OpenAICompatAliasPoolFallsBackWithinSameAuth(t *testing.T) {
 	alias := "claude-opus-4.66"
 	executor := &openAICompatPoolExecutor{