diff --git a/Cargo.lock b/Cargo.lock
index ba5c3c8e..ad90a3fa 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -717,7 +717,7 @@ checksum = "955d28af4278de8121b7ebeb796b6a45735dc01436d898801014aced2773a3d6"
 
 [[package]]
 name = "sentry_protos"
-version = "0.8.29"
+version = "0.8.30"
 dependencies = [
  "prost",
  "prost-types",
diff --git a/proto/sentry_protos/billing/v1/services/usage/v1/endpoint_usage.proto b/proto/sentry_protos/billing/v1/services/usage/v1/endpoint_usage.proto
index 73babbfe..2a3c4673 100644
--- a/proto/sentry_protos/billing/v1/services/usage/v1/endpoint_usage.proto
+++ b/proto/sentry_protos/billing/v1/services/usage/v1/endpoint_usage.proto
@@ -36,6 +36,12 @@ message GetUsageResponse {
   repeated DailySeatUsage seat_days = 3;
 
   repeated CategorySeatUsage seats = 2 [deprecated = true]; // DEPRECATED: use seat_days
+
+  // The latest timestamp of usage data included in this response (inclusive
+  // — there is at least one row at exactly this timestamp). Callers persist
+  // this as the contract's watermark; subsequent queries should resume
+  // strictly after this timestamp to avoid double-counting the boundary.
+  optional google.protobuf.Timestamp last_usage_ts = 4;
 }
 
 message GetUsageRequest {
diff --git a/rust/src/sentry_protos.billing.v1.services.usage.v1.rs b/rust/src/sentry_protos.billing.v1.services.usage.v1.rs
index a170e385..8611ba68 100644
--- a/rust/src/sentry_protos.billing.v1.services.usage.v1.rs
+++ b/rust/src/sentry_protos.billing.v1.services.usage.v1.rs
@@ -78,6 +78,12 @@ pub struct GetUsageResponse {
     #[deprecated]
     #[prost(message, repeated, tag = "2")]
     pub seats: ::prost::alloc::vec::Vec<CategorySeatUsage>,
+    /// The latest timestamp of usage data included in this response (inclusive
+    /// — there is at least one row at exactly this timestamp). Callers persist
+    /// this as the contract's watermark; subsequent queries should resume
+    /// strictly after this timestamp to avoid double-counting the boundary.
+    #[prost(message, optional, tag = "4")]
+    pub last_usage_ts: ::core::option::Option<::prost_types::Timestamp>,
 }
 #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct GetUsageRequest {