diff --git a/proto/identity/associations/association.proto b/proto/identity/associations/association.proto
index 12becb26..e59a136e 100644
--- a/proto/identity/associations/association.proto
+++ b/proto/identity/associations/association.proto
@@ -16,6 +16,12 @@ message MemberIdentifier {
   }
 }
 
+// single member that optionally indicates the member that added them
+message Member {
+  MemberIdentifier identifier = 1;
+  optional MemberIdentifier added_by_entity = 2;
+}
+
 // The first entry of any XID log. The XID must be deterministically derivable
 // from the address and nonce.
 // The recovery address defaults to the initial associated_address unless
@@ -72,3 +78,23 @@ message IdentityUpdate {
   uint64 client_timestamp_ns = 2;
   string inbox_id = 3;
 }
+
+// Map of members belonging to an inbox_id
+message MemberMap {
+  MemberIdentifier key = 1;
+  Member value = 2;
+}
+
+// A final association state resulting from multiple `IdentityUpdates`
+message AssociationState {
+  string inbox_id = 1;
+  repeated MemberMap members = 2;
+  string recovery_address = 3;
+  repeated bytes seen_signatures = 4;
+}
+
+/// state diff between two final AssociationStates
+message AssociationStateDiff {
+  repeated MemberIdentifier new_members = 1;
+  repeated MemberIdentifier removed_members = 2;
+}
diff --git a/proto/mls_validation/v1/service.proto b/proto/mls_validation/v1/service.proto
index 7cff4d27..5a0482bd 100644
--- a/proto/mls_validation/v1/service.proto
+++ b/proto/mls_validation/v1/service.proto
@@ -2,6 +2,8 @@
 syntax = "proto3";
 package xmtp.mls_validation.v1;
 
+import "identity/associations/association.proto";
+
 option go_package = "github.com/xmtp/proto/v3/go/mls_validation/v1";
 
 // RPCs for the new MLS API
@@ -11,6 +13,9 @@ service ValidationApi {
 
   // Validates and parses a group message and returns relevant details
   rpc ValidateGroupMessages(ValidateGroupMessagesRequest) returns (ValidateGroupMessagesResponse) {}
+  
+  // Gets the final association state for a batch of identity updates
+  rpc GetAssociationState(GetAssociationStateRequest) returns (GetAssociationStateResponse) {}
 }
 
 // Contains a batch of serialized Key Packages
@@ -59,3 +64,17 @@ message ValidateGroupMessagesResponse {
 
   repeated ValidationResponse responses = 1;
 }
+
+// Request to get a final association state for identity updates
+message GetAssociationStateRequest {
+  // List of identity updates
+  repeated xmtp.identity.associations.IdentityUpdate old_updates = 1;
+  repeated xmtp.identity.associations.IdentityUpdate new_updates = 2;
+}
+
+// Response to GetAssociationStateRequest, containing the final association state
+// for an InboxID
+message GetAssociationStateResponse {
+  xmtp.identity.associations.AssociationState association_state = 1;
+  xmtp.identity.associations.AssociationStateDiff state_diff = 2;
+}