diff --git a/watchtower/wtdb/session_state_update.go b/watchtower/wtdb/session_state_update.go
new file mode 100644
index 00000000..7711b10f
--- /dev/null
+++ b/watchtower/wtdb/session_state_update.go
@@ -0,0 +1,23 @@
+package wtdb
+
+// SessionStateUpdate holds a state update sent by a client along with its
+// SessionID.
+type SessionStateUpdate struct {
+	// ID the session id of the client who sent the state update.
+	ID SessionID
+
+	// SeqNum the sequence number of the update within the session.
+	SeqNum uint16
+
+	// LastApplied the highest index that client has acknowledged is
+	// committed
+	LastApplied uint16
+
+	// Hint is the 16-byte prefix of the revoked commitment transaction.
+	Hint BreachHint
+
+	// EncryptedBlob is a ciphertext containing the sweep information for
+	// exacting justice if the commitment transaction matching the breach
+	// hint is braodcast.
+	EncryptedBlob []byte
+}