diff --git a/.protolint.yaml b/.protolint.yaml
index 3aef447..5a92260 100644
--- a/.protolint.yaml
+++ b/.protolint.yaml
@@ -50,6 +50,8 @@ lint:
       - MESSAGES_HAVE_COMMENT
       - RPCS_HAVE_COMMENT
       - SERVICES_HAVE_COMMENT
+      # Allow for fields we have in libxmtp like "sent_at_ns"
+      - FIELD_NAMES_EXCLUDE_PREPOSITIONS
 
   # Linter rules option.
   rules_option:
diff --git a/proto/device_sync/consent_backup.proto b/proto/device_sync/consent_backup.proto
new file mode 100644
index 0000000..12bd636
--- /dev/null
+++ b/proto/device_sync/consent_backup.proto
@@ -0,0 +1,26 @@
+// Definitions for backups
+syntax = "proto3";
+package xmtp.device_sync.consent_backup;
+
+// Proto representation of a consent record save
+message ConsentSave {
+  ConsentTypeSave entity_type = 1;
+  ConsentStateSave state = 2;
+  string entity = 3;
+}
+
+// Consent record type
+enum ConsentTypeSave {
+  CONSENT_TYPE_SAVE_UNSPECIFIED = 0;
+  CONSENT_TYPE_SAVE_CONVERSATION_ID = 1;
+  CONSENT_TYPE_SAVE_INBOX_ID = 2;
+  CONSENT_TYPE_SAVE_ADDRESS = 3;
+}
+
+// Consent record state
+enum ConsentStateSave {
+  CONSENT_STATE_SAVE_UNSPECIFIED = 0;
+  CONSENT_STATE_SAVE_UNKNOWN = 1;
+  CONSENT_STATE_SAVE_ALLOWED = 2;
+  CONSENT_STATE_SAVE_DENIED = 3;
+}
diff --git a/proto/device_sync/device_sync.proto b/proto/device_sync/device_sync.proto
new file mode 100644
index 0000000..95a513b
--- /dev/null
+++ b/proto/device_sync/device_sync.proto
@@ -0,0 +1,33 @@
+// Definitions for backups
+syntax = "proto3";
+package xmtp.device_sync;
+
+import "device_sync/consent_backup.proto";
+import "device_sync/group_backup.proto";
+import "device_sync/message_backup.proto";
+
+// Union type representing everything that can be serialied and saved in a backup archive.
+message BackupElement {
+  oneof element {
+    BackupMetadataSave metadata = 1;
+    xmtp.device_sync.group_backup.GroupSave group = 2;
+    xmtp.device_sync.message_backup.GroupMessageSave group_message = 3;
+    xmtp.device_sync.consent_backup.ConsentSave consent = 4;
+  }
+}
+
+// Proto representation of backup metadata
+// (Backup version is explicitly missing - it's stored as a header.)
+message BackupMetadataSave {
+  repeated BackupElementSelection elements = 2;
+  int64 exported_at_ns = 3;
+  optional int64 start_ns = 4;
+  optional int64 end_ns = 5;
+}
+
+// Elements selected for backup
+enum BackupElementSelection {
+  BACKUP_ELEMENT_SELECTION_UNSPECIFIED = 0;
+  BACKUP_ELEMENT_SELECTION_MESSAGES = 1;
+  BACKUP_ELEMENT_SELECTION_CONSENT = 2;
+}
diff --git a/proto/device_sync/group_backup.proto b/proto/device_sync/group_backup.proto
new file mode 100644
index 0000000..df52390
--- /dev/null
+++ b/proto/device_sync/group_backup.proto
@@ -0,0 +1,35 @@
+// Definitions for backups
+syntax = "proto3";
+package xmtp.device_sync.group_backup;
+
+// Proto representation of a stored group
+message GroupSave {
+  bytes id = 1;
+  int64 created_at_ns = 2;
+  GroupMembershipStateSave membership_state = 3;
+  int64 installations_last_checked = 4;
+  string added_by_inbox_id = 5;
+  optional int64 welcome_id = 6;
+  int64 rotated_at_ns = 7;
+  ConversationTypeSave conversation_type = 8;
+  optional string dm_id = 9;
+  optional int64 last_message_ns = 10;
+  optional int64 message_disappear_from_ns = 11;
+  optional int64 message_disappear_in_ns = 12;
+}
+
+// Group membership state
+enum GroupMembershipStateSave {
+  GROUP_MEMBERSHIP_STATE_SAVE_UNSPECIFIED = 0;
+  GROUP_MEMBERSHIP_STATE_SAVE_ALLOWED = 1;
+  GROUP_MEMBERSHIP_STATE_SAVE_REJECTED = 2;
+  GROUP_MEMBERSHIP_STATE_SAVE_PENDING = 3;
+}
+
+// Conversation type
+enum ConversationTypeSave {
+  CONVERSATION_TYPE_SAVE_UNSPECIFIED = 0;
+  CONVERSATION_TYPE_SAVE_GROUP = 1;
+  CONVERSATION_TYPE_SAVE_DM = 2;
+  CONVERSATION_TYPE_SAVE_SYNC = 3;
+}
diff --git a/proto/device_sync/message_backup.proto b/proto/device_sync/message_backup.proto
new file mode 100644
index 0000000..9870cfe
--- /dev/null
+++ b/proto/device_sync/message_backup.proto
@@ -0,0 +1,50 @@
+// Definitions for backups
+syntax = "proto3";
+package xmtp.device_sync.message_backup;
+
+// Proto representation of a stored group message
+message GroupMessageSave {
+  bytes id = 1;
+  bytes group_id = 2;
+  bytes decrypted_message_bytes = 3;
+  int64 sent_at_ns = 4;
+  GroupMessageKindSave kind = 5;
+  bytes sender_installation_id = 6;
+  string sender_inbox_id = 7;
+  DeliveryStatusSave delivery_status = 8;
+  ContentTypeSave content_type = 9;
+  int32 version_major = 10;
+  int32 version_minor = 11;
+  string authority_id = 12;
+  optional bytes reference_id = 13;
+}
+
+// Group message kind
+enum GroupMessageKindSave {
+  GROUP_MESSAGE_KIND_SAVE_UNSPECIFIED = 0;
+  GROUP_MESSAGE_KIND_SAVE_APPLICATION = 1;
+  GROUP_MESSAGE_KIND_SAVE_MEMBERSHIP_CHANGE = 2;
+}
+
+// Group message delivery status
+enum DeliveryStatusSave {
+  DELIVERY_STATUS_SAVE_UNSPECIFIED = 0;
+  DELIVERY_STATUS_SAVE_UNPUBLISHED = 1;
+  DELIVERY_STATUS_SAVE_PUBLISHED = 2;
+  DELIVERY_STATUS_SAVE_FAILED = 3;
+}
+
+// Group message content type
+enum ContentTypeSave {
+  CONTENT_TYPE_SAVE_UNSPECIFIED = 0;
+  CONTENT_TYPE_SAVE_UNKNOWN = 1;
+  CONTENT_TYPE_SAVE_TEXT = 2;
+  CONTENT_TYPE_SAVE_GROUP_MEMBERSHIP_CHANGE = 3;
+  CONTENT_TYPE_SAVE_GROUP_UPDATED = 4;
+  CONTENT_TYPE_SAVE_REACTION = 5;
+  CONTENT_TYPE_SAVE_READ_RECEIPT = 6;
+  CONTENT_TYPE_SAVE_REPLY = 7;
+  CONTENT_TYPE_SAVE_ATTACHMENT = 8;
+  CONTENT_TYPE_SAVE_REMOTE_ATTACHMENT = 9;
+  CONTENT_TYPE_SAVE_TRANSACTION_REFERENCE = 10;
+}