diff --git a/server-rs/crates/module-runtime/src/membership/upgrade.rs b/server-rs/crates/module-runtime/src/membership/upgrade.rs
index 30545a1d9..169f3213e 100644
--- a/server-rs/crates/module-runtime/src/membership/upgrade.rs
+++ b/server-rs/crates/module-runtime/src/membership/upgrade.rs
@@ -161,8 +161,8 @@ fn validate_runtime_profile_membership_upgrade_quote_input(
 pub fn quote_runtime_profile_membership_upgrade(
     input: RuntimeProfileMembershipUpgradeQuoteInput,
 ) -> Result<RuntimeProfileMembershipUpgradeQuote, RuntimeProfileMembershipUpgradeRejection> {
-    validate_runtime_profile_membership_upgrade_quote_input(&input)?;
     check_runtime_profile_membership_upgrade_allowed(&input.current, &input.target)?;
+    validate_runtime_profile_membership_upgrade_quote_input(&input)?;
 
     let current = input.current;
     let target = input.target;
@@ -506,6 +506,22 @@ mod tests {
             }),
             Err(RuntimeProfileMembershipUpgradeRejection::CycleKindChangeUnsupported)
         );
+        // 中文注释：年付转月付时 `cycle_index = 3` 超过月付的 1 期；领域校验必须先于数值校验，
+        // 否则会被误判成 InvalidQuoteInput，破坏「账期变更不支持」这一对外契约。
+        assert_eq!(
+            quote_runtime_profile_membership_upgrade(RuntimeProfileMembershipUpgradeQuoteInput {
+                current: snapshot(
+                    RuntimeProfileMembershipPlan::Plus,
+                    RuntimeProfileMembershipCycleKind::Yearly,
+                ),
+                target: snapshot(
+                    RuntimeProfileMembershipPlan::Pro,
+                    RuntimeProfileMembershipCycleKind::Monthly,
+                ),
+                ..base_input()
+            }),
+            Err(RuntimeProfileMembershipUpgradeRejection::CycleKindChangeUnsupported)
+        );
     }
 
     #[test]