diff --git a/Cargo.lock b/Cargo.lock
index 11fd409c..11f1749f 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -717,7 +717,7 @@ checksum = "955d28af4278de8121b7ebeb796b6a45735dc01436d898801014aced2773a3d6"
 
 [[package]]
 name = "sentry_protos"
-version = "0.37.0"
+version = "0.37.1"
 dependencies = [
  "prost",
  "prost-types",
diff --git a/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_assign_balance_contract.proto b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_assign_balance_contract.proto
new file mode 100644
index 00000000..21eee7ee
--- /dev/null
+++ b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_assign_balance_contract.proto
@@ -0,0 +1,12 @@
+syntax = "proto3";
+
+package sentry_protos.billing.v1.services.engagement.v1;
+
+message AssignBalanceContractRequest {
+  optional uint64 previous_contract_id = 1;
+  uint64 contract_id = 2;
+}
+
+message AssignBalanceContractResponse {
+  bool assigned = 1;
+}
diff --git a/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_get_contract_balance.proto b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_get_contract_balance.proto
new file mode 100644
index 00000000..0bba80dd
--- /dev/null
+++ b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_get_contract_balance.proto
@@ -0,0 +1,11 @@
+syntax = "proto3";
+
+package sentry_protos.billing.v1.services.engagement.v1;
+
+message GetContractBalanceRequest {
+  uint64 contract_id = 1;
+}
+
+message GetContractBalanceResponse {
+  uint64 balance_cents = 1;
+}
diff --git a/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_get_unassigned_balances.proto b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_get_unassigned_balances.proto
new file mode 100644
index 00000000..34b059c1
--- /dev/null
+++ b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_get_unassigned_balances.proto
@@ -0,0 +1,9 @@
+syntax = "proto3";
+
+package sentry_protos.billing.v1.services.engagement.v1;
+
+message GetUnassignedBalancesRequest {}
+
+message GetUnassignedBalancesResponse {
+  repeated uint64 previous_contract_ids = 1;
+}
diff --git a/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_rollover_monetary_grants.proto b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_rollover_monetary_grants.proto
new file mode 100644
index 00000000..de4b7005
--- /dev/null
+++ b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_rollover_monetary_grants.proto
@@ -0,0 +1,10 @@
+syntax = "proto3";
+
+package sentry_protos.billing.v1.services.engagement.v1;
+
+message RolloverMonetaryGrantsRequest {
+  uint64 previous_contract_id = 1;
+  uint64 next_contract_id = 2;
+}
+
+message RolloverMonetaryGrantsResponse {}
diff --git a/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_stage_rollover_balance.proto b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_stage_rollover_balance.proto
new file mode 100644
index 00000000..fb2ec668
--- /dev/null
+++ b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_stage_rollover_balance.proto
@@ -0,0 +1,11 @@
+syntax = "proto3";
+
+package sentry_protos.billing.v1.services.engagement.v1;
+
+message StageRolloverBalanceRequest {
+  uint64 contract_id = 1;
+  // Amount used in the previous contract that will be subtracted when carrying over the balance.
+  uint64 amount_used_cents = 2;
+}
+
+message StageRolloverBalanceResponse {}
diff --git a/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_stage_rollover_monetary_grants.proto b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_stage_rollover_monetary_grants.proto
new file mode 100644
index 00000000..d27bf975
--- /dev/null
+++ b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_stage_rollover_monetary_grants.proto
@@ -0,0 +1,10 @@
+syntax = "proto3";
+
+package sentry_protos.billing.v1.services.engagement.v1;
+
+message StageRolloverMonetaryGrantsRequest {
+  uint64 previous_contract_id = 1;
+  optional uint64 balance_cents_used = 2;
+}
+
+message StageRolloverMonetaryGrantsResponse {}
diff --git a/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_upsert_contract_balance.proto b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_upsert_contract_balance.proto
new file mode 100644
index 00000000..11bcdb65
--- /dev/null
+++ b/proto/sentry_protos/billing/v1/services/engagement/v1/endpoint_upsert_contract_balance.proto
@@ -0,0 +1,14 @@
+syntax = "proto3";
+
+package sentry_protos.billing.v1.services.engagement.v1;
+
+message UpsertContractBalanceRequest {
+  uint64 contract_id = 1;
+  int64 amount_cents = 2;
+  // There may not be a previous contract if this is the first contract for the organization.
+  optional uint64 previous_contract_id = 3;
+}
+
+message UpsertContractBalanceResponse {
+  uint64 new_balance_cents = 1;
+}
diff --git a/rust/src/sentry_protos.billing.v1.services.engagement.v1.rs b/rust/src/sentry_protos.billing.v1.services.engagement.v1.rs
index 1abc56d1..1c81b7e4 100644
--- a/rust/src/sentry_protos.billing.v1.services.engagement.v1.rs
+++ b/rust/src/sentry_protos.billing.v1.services.engagement.v1.rs
@@ -1,4 +1,16 @@
 // This file is @generated by prost-build.
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct AssignBalanceContractRequest {
+    #[prost(uint64, optional, tag = "1")]
+    pub previous_contract_id: ::core::option::Option<u64>,
+    #[prost(uint64, tag = "2")]
+    pub contract_id: u64,
+}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct AssignBalanceContractResponse {
+    #[prost(bool, tag = "1")]
+    pub assigned: bool,
+}
 /// How a Grant was created.
 #[derive(Clone, Copy, Debug, PartialEq, Eq, Hash, PartialOrd, Ord, ::prost::Enumeration)]
 #[repr(i32)]
@@ -308,6 +320,16 @@ pub struct GetActiveTrialsResponse {
     #[prost(message, repeated, tag = "1")]
     pub trials: ::prost::alloc::vec::Vec<Trial>,
 }
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct GetContractBalanceRequest {
+    #[prost(uint64, tag = "1")]
+    pub contract_id: u64,
+}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct GetContractBalanceResponse {
+    #[prost(uint64, tag = "1")]
+    pub balance_cents: u64,
+}
 /// A grant with counter-grant chains collapsed into a single effective amount.
 /// Returned in drain priority order (end_date ASC, effective_amount ASC, grant_id ASC).
 #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
@@ -432,6 +454,13 @@ impl EffectiveMonetarySource {
         }
     }
 }
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct GetUnassignedBalancesRequest {}
+#[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct GetUnassignedBalancesResponse {
+    #[prost(uint64, repeated, tag = "1")]
+    pub previous_contract_ids: ::prost::alloc::vec::Vec<u64>,
+}
 #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct EffectiveUnitGrant {
     #[prost(string, tag = "1")]
@@ -467,6 +496,34 @@ pub struct GetUnitGrantsResponse {
     #[prost(message, repeated, tag = "1")]
     pub grants: ::prost::alloc::vec::Vec<EffectiveUnitGrant>,
 }
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct RolloverMonetaryGrantsRequest {
+    #[prost(uint64, tag = "1")]
+    pub previous_contract_id: u64,
+    #[prost(uint64, tag = "2")]
+    pub next_contract_id: u64,
+}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct RolloverMonetaryGrantsResponse {}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct StageRolloverBalanceRequest {
+    #[prost(uint64, tag = "1")]
+    pub contract_id: u64,
+    /// Amount used in the previous contract that will be subtracted when carrying over the balance.
+    #[prost(uint64, tag = "2")]
+    pub amount_used_cents: u64,
+}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct StageRolloverBalanceResponse {}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct StageRolloverMonetaryGrantsRequest {
+    #[prost(uint64, tag = "1")]
+    pub previous_contract_id: u64,
+    #[prost(uint64, optional, tag = "2")]
+    pub balance_cents_used: ::core::option::Option<u64>,
+}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct StageRolloverMonetaryGrantsResponse {}
 #[derive(Clone, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct StartTrialRequest {
     #[prost(uint64, tag = "1")]
@@ -494,3 +551,18 @@ pub mod start_trial_request {
 }
 #[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
 pub struct StartTrialResponse {}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct UpsertContractBalanceRequest {
+    #[prost(uint64, tag = "1")]
+    pub contract_id: u64,
+    #[prost(int64, tag = "2")]
+    pub amount_cents: i64,
+    /// There may not be a previous contract if this is the first contract for the organization.
+    #[prost(uint64, optional, tag = "3")]
+    pub previous_contract_id: ::core::option::Option<u64>,
+}
+#[derive(Clone, Copy, PartialEq, Eq, Hash, ::prost::Message)]
+pub struct UpsertContractBalanceResponse {
+    #[prost(uint64, tag = "1")]
+    pub new_balance_cents: u64,
+}