diff --git a/server-rs/crates/module-runtime/src/lib.rs b/server-rs/crates/module-runtime/src/lib.rs
index 2cb68ce6b..bcec66d2e 100644
--- a/server-rs/crates/module-runtime/src/lib.rs
+++ b/server-rs/crates/module-runtime/src/lib.rs
@@ -4,15 +4,8 @@ pub mod civil_calendar;
 pub use civil_calendar::*;
 mod llm_billing;
 pub use llm_billing::*;
-mod membership_cycle;
-pub use membership_cycle::*;
-mod membership_limits;
-pub use membership_limits::*;
-mod membership_catalog;
-pub use membership_catalog::*;
-mod membership_upgrade;
-pub use membership_upgrade::*;
 mod application;
+pub mod membership;
 pub use agc_models::*;
 mod commands;
 mod domain;
@@ -23,6 +16,7 @@ pub use application::*;
 pub use commands::*;
 pub use domain::*;
 pub use errors::*;
+pub use membership::*;
 
 use shared_kernel::format_rfc3339 as format_shared_rfc3339;
 use time::OffsetDateTime;
diff --git a/server-rs/crates/module-runtime/src/membership_catalog.rs b/server-rs/crates/module-runtime/src/membership/catalog.rs
similarity index 100%
rename from server-rs/crates/module-runtime/src/membership_catalog.rs
rename to server-rs/crates/module-runtime/src/membership/catalog.rs
diff --git a/server-rs/crates/module-runtime/src/membership_cycle.rs b/server-rs/crates/module-runtime/src/membership/cycle.rs
similarity index 100%
rename from server-rs/crates/module-runtime/src/membership_cycle.rs
rename to server-rs/crates/module-runtime/src/membership/cycle.rs
diff --git a/server-rs/crates/module-runtime/src/membership_limits.rs b/server-rs/crates/module-runtime/src/membership/limits.rs
similarity index 100%
rename from server-rs/crates/module-runtime/src/membership_limits.rs
rename to server-rs/crates/module-runtime/src/membership/limits.rs
diff --git a/server-rs/crates/module-runtime/src/membership/mod.rs b/server-rs/crates/module-runtime/src/membership/mod.rs
new file mode 100644
index 000000000..5edfeeb37
--- /dev/null
+++ b/server-rs/crates/module-runtime/src/membership/mod.rs
@@ -0,0 +1,20 @@
+//! 会员计费领域层（纯函数，无 IO）。
+//!
+//! 只放会员侧的规则计算：档位目录与解析、自然月账期推进、并发上限哨兵与补差升级报价。
+//! SpacetimeDB 写入与事务编排留在 `spacetime-module`，HTTP 契约留在 `api-server`。
+//!
+//! 子模块按依赖顺序排列：
+//! - [`catalog`]：档位枚举 → 可下单套餐（价格 / 每期泥点 / 模型权限 / 并发）。
+//! - [`cycle`]：北京时间自然月账期（1/31 → 2/28 → 3/31，每期从原始锚点重算）。
+//! - [`limits`]：并发上限哨兵，`>= 128` 视为「不设上限」。
+//! - [`upgrade`]：补差升级报价与允许操作矩阵。
+
+mod catalog;
+mod cycle;
+mod limits;
+mod upgrade;
+
+pub use catalog::*;
+pub use cycle::*;
+pub use limits::*;
+pub use upgrade::*;
diff --git a/server-rs/crates/module-runtime/src/membership_upgrade.rs b/server-rs/crates/module-runtime/src/membership/upgrade.rs
similarity index 98%
rename from server-rs/crates/module-runtime/src/membership_upgrade.rs
rename to server-rs/crates/module-runtime/src/membership/upgrade.rs
index 029f7274f..3f5661eba 100644
--- a/server-rs/crates/module-runtime/src/membership_upgrade.rs
+++ b/server-rs/crates/module-runtime/src/membership/upgrade.rs
@@ -15,8 +15,8 @@
 
 use serde::{Deserialize, Serialize};
 
-use crate::membership_catalog::resolve_runtime_profile_membership_plan_snapshot;
-use crate::membership_cycle::membership_cycle_remaining_micros;
+use super::catalog::resolve_runtime_profile_membership_plan_snapshot;
+use super::cycle::membership_cycle_remaining_micros;
 use crate::{RuntimeProfileMembershipCycleKind, RuntimeProfileMembershipPlan};
 
 /// 比例分母：百万分之一。
@@ -194,7 +194,7 @@ fn ceil_div(numerator: u128, denominator: u128) -> u64 {
 #[cfg(test)]
 mod tests {
     use super::*;
-    use crate::membership_cycle::beijing_local_micros;
+    use crate::membership::cycle::beijing_local_micros;
 
     const DAY_MICROS: i64 = 86_400_000_000;