diff --git a/.gitignore b/.gitignore
index c99c3ac..c81757e 100644
--- a/.gitignore
+++ b/.gitignore
@@ -77,7 +77,6 @@ bin/
 
 
 
-
 *.cpi
 *.cpb
 *.cpk
diff --git a/contracts/src/main/java/com/r3/developers/csdetemplate/utxoexample/contracts/ChatContract.java b/contracts/src/main/java/com/r3/developers/csdetemplate/utxoexample/contracts/ChatContract.java
index 7e114ad..e42f0ca 100644
--- a/contracts/src/main/java/com/r3/developers/csdetemplate/utxoexample/contracts/ChatContract.java
+++ b/contracts/src/main/java/com/r3/developers/csdetemplate/utxoexample/contracts/ChatContract.java
@@ -1,8 +1,11 @@
 package com.r3.developers.csdetemplate.utxoexample.contracts;
 
+import com.r3.developers.csdetemplate.utxoexample.states.ChatState;
+import net.corda.v5.base.exceptions.CordaRuntimeException;
 import net.corda.v5.ledger.utxo.Command;
 import net.corda.v5.ledger.utxo.Contract;
 import net.corda.v5.ledger.utxo.ContractState;
+import net.corda.v5.ledger.utxo.StateAndRef;
 import net.corda.v5.ledger.utxo.transaction.UtxoLedgerTransaction;
 import org.jetbrains.annotations.NotNull;
 
@@ -11,36 +14,54 @@ import java.util.Set;
 
 import static java.util.Objects.*;
 
+// todo: START here
+
 public class ChatContract implements Contract {
 
     public static class Create implements Command { }
     public static class Update implements Command { }
 
-    @Override
-    public boolean isRelevant(@NotNull ContractState state, @NotNull Set<? extends PublicKey> myKeys) {
-        return Contract.super.isRelevant(state, myKeys);
-    }
+//    @Override
+//    public boolean isRelevant(@NotNull ContractState state, @NotNull Set<? extends PublicKey> myKeys) {
+//        return Contract.super.isRelevant(state, myKeys);
+//    }
 
     @Override
-    public void verify(@NotNull UtxoLedgerTransaction transaction) throws IllegalArgumentException {
-        Command command = requireNonNull( transaction.getCommands().get(0), "Require a single command");
+    public void verify(UtxoLedgerTransaction transaction) {
+
+
+//        Command command = requireNonNull( transaction.getCommands().get(0), "Require a single command");  // this doesn't ensure there is one command
+        requireThat( transaction.getCommands().size() == 1, "Require a single command.");
+        Command command = transaction.getCommands().get(0);
+
+        ChatState input = transaction.getOutputStates(ChatState.class).get(0);
+        ChatState output = transaction.getInputStates(ChatState.class).get(0);
+
+        requireThat(output.getParticipants().size() == 2, "The output state should have two and only two participants.");
 
         if(command.getClass() == Create.class) {
-            requireThat(transaction.getInputContractStates().isEmpty(), "When command is Create there should be no input state");
-            requireThat(transaction.getOutputContractStates().size() == 1, "When command is Create there should be one and only one output state");
+            requireThat(transaction.getInputContractStates().isEmpty(), "When command is Create there should be no input states.");
+            requireThat(transaction.getOutputContractStates().size() == 1, "When command is Create there should be one and only one output state.");
         }
         else if(command.getClass() == Update.class) {
-            requireThat(transaction.getInputContractStates().size() == 1, "When command is Update there should be one and only one input state");
-            requireThat(transaction.getOutputContractStates().size() == 1, "When command is Update there should be one and only one output state");
+            requireThat(transaction.getInputContractStates().size() == 1, "When command is Update there should be one and only one input state.");
+            requireThat(transaction.getOutputContractStates().size() == 1, "When command is Update there should be one and only one output state.");
+            requireThat(input.getId() == output.getId(), "When command is Update id must not change.");
+            requireThat(input.getChatName() == output.getChatName(), "When command is Update chatName must not change.");
+            requireThat(
+                    input.getParticipants().containsAll(output.getParticipants()) &&
+                    output.getParticipants().containsAll(input.getParticipants()),
+                    "When command is Update participants must not change.");
+
         }
         else {
-            throw new IllegalArgumentException("Unsupported command");
+            throw new CordaRuntimeException("Unsupported command");
         }
     }
 
-    private void requireThat(boolean asserted, String errorMessage) throws IllegalArgumentException {
+    private void requireThat(boolean asserted, String errorMessage) {
         if(!asserted) {
-            throw new IllegalArgumentException("Failed requirement: " + errorMessage);
+            throw new CordaRuntimeException("Failed requirement: " + errorMessage);
         }
     }
 }
diff --git a/contracts/src/main/java/com/r3/developers/csdetemplate/utxoexample/states/ChatState.java b/contracts/src/main/java/com/r3/developers/csdetemplate/utxoexample/states/ChatState.java
index 64af258..20f80ef 100644
--- a/contracts/src/main/java/com/r3/developers/csdetemplate/utxoexample/states/ChatState.java
+++ b/contracts/src/main/java/com/r3/developers/csdetemplate/utxoexample/states/ChatState.java
@@ -11,6 +11,8 @@ import org.jetbrains.annotations.NotNull;
 import java.security.PublicKey;
 import java.util.*;
 
+// todo: Clear out commented code
+
 //@CordaSerializable
 @BelongsToContract(ChatContract.class)
 public class ChatState implements ContractState {
@@ -38,17 +40,17 @@ public class ChatState implements ContractState {
         this.participants = participants;
     }
 
-    // Convenience constructor for initial ChatState objects that need a new UUID generated.
-    public ChatState(String chatName,
-                     MemberX500Name messageFrom,
-                     String message,
-                     List<PublicKey> participants) {
-        this(UUID.randomUUID(),
-                chatName,
-                messageFrom,
-                message,
-                participants);
-    }
+//    // Convenience constructor for initial ChatState objects that need a new UUID generated.
+//    public ChatState(String chatName,
+//                     MemberX500Name messageFrom,
+//                     String message,
+//                     List<PublicKey> participants) {
+//        this(UUID.randomUUID(),
+//                chatName,
+//                messageFrom,
+//                message,
+//                participants);
+//    }
 
     public UUID getId() {
         return id;
diff --git a/workflows/src/main/java/com/r3/developers/csdetemplate/utxoexample/workflows/CreateNewChatFlow.java b/workflows/src/main/java/com/r3/developers/csdetemplate/utxoexample/workflows/CreateNewChatFlow.java
index dd51fdd..c433fab 100644
--- a/workflows/src/main/java/com/r3/developers/csdetemplate/utxoexample/workflows/CreateNewChatFlow.java
+++ b/workflows/src/main/java/com/r3/developers/csdetemplate/utxoexample/workflows/CreateNewChatFlow.java
@@ -24,6 +24,7 @@ import java.time.Duration;
 import java.time.Instant;
 import java.util.Arrays;
 import java.util.Objects;
+import java.util.UUID;
 
 import static java.util.Objects.*;
 
@@ -65,7 +66,7 @@ public class CreateNewChatFlow implements RPCStartableFlow {
                     "can't find other member"
             );
 
-            ChatState chatState = new ChatState(
+            ChatState chatState = new ChatState(UUID.randomUUID(),
                     flowArgs.getChatName(),
                     myInfo.getName(),
                     flowArgs.getMessage(),