diff --git a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/FlowEvent.avsc b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/FlowEvent.avsc
index e55a08d157..53b7fcb9b1 100644
--- a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/FlowEvent.avsc
+++ b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/FlowEvent.avsc
@@ -11,7 +11,6 @@
       "name": "payload",
       "type": [
         "net.corda.data.flow.event.StartFlow",
-        "net.corda.data.flow.event.Wakeup",
         "net.corda.data.flow.output.FlowStatus",
         "net.corda.data.flow.event.SessionEvent",
         "net.corda.data.flow.event.external.ExternalEventResponse"
diff --git a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/SessionEvent.avsc b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/SessionEvent.avsc
index d40abd5746..980ad4a443 100644
--- a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/SessionEvent.avsc
+++ b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/SessionEvent.avsc
@@ -50,8 +50,8 @@
     {
       "name": "payload",
       "type": [
-        "net.corda.data.flow.event.session.SessionInit",
-        "net.corda.data.flow.event.session.SessionConfirm",
+        "net.corda.data.flow.event.session.SessionCounterpartyInfoRequest",
+        "net.corda.data.flow.event.session.SessionCounterpartyInfoResponse",
         "net.corda.data.flow.event.session.SessionData",
         "net.corda.data.flow.event.session.SessionClose",
         "net.corda.data.flow.event.session.SessionError"
diff --git a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/Wakeup.avsc b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/Wakeup.avsc
deleted file mode 100644
index 0421ca665e..0000000000
--- a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/Wakeup.avsc
+++ /dev/null
@@ -1,7 +0,0 @@
-{
-  "type": "record",
-  "name": "Wakeup",
-  "namespace": "net.corda.data.flow.event",
-  "fields": []
-}
-
diff --git a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/session/SessionConfirm.avsc b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/session/SessionConfirm.avsc
deleted file mode 100644
index d51b9f99a5..0000000000
--- a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/session/SessionConfirm.avsc
+++ /dev/null
@@ -1,7 +0,0 @@
-{
-  "type": "record",
-  "name": "SessionConfirm",
-  "doc" : "Acknowledge to counterparty that the session has been confirmed and is ready to send and receive messages.",
-  "namespace": "net.corda.data.flow.event.session",
-  "fields": []
-}
diff --git a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/session/SessionCounterpartyInfoRequest.avsc b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/session/SessionCounterpartyInfoRequest.avsc
new file mode 100644
index 0000000000..99758c5d76
--- /dev/null
+++ b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/session/SessionCounterpartyInfoRequest.avsc
@@ -0,0 +1,13 @@
+{
+  "type": "record",
+  "name": "SessionCounterpartyInfoRequest",
+  "doc" : "Request counterparties flow session information. This includes the flow protocol version that they are running.",
+  "namespace": "net.corda.data.flow.event.session",
+  "fields": [
+    {
+      "name": "sessionInit",
+      "type": "net.corda.data.flow.event.session.SessionInit",
+      "doc": "Contains information that can be used to start an initiated flow. Will be null for messages sent to the initiator. Will be null when initiated party is confirmed to be present to ensure out of order messages that arrive first contain this info."
+    }
+  ]
+}
diff --git a/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/session/SessionCounterpartyInfoResponse.avsc b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/session/SessionCounterpartyInfoResponse.avsc
new file mode 100644
index 0000000000..039e4d4e3a
--- /dev/null
+++ b/data/avro-schema/src/main/resources/avro/net/corda/data/flow/event/session/SessionCounterpartyInfoResponse.avsc
@@ -0,0 +1,7 @@
+{
+  "type": "record",
+  "name": "SessionCounterpartyInfoResponse",
+  "doc" : "Sent from initiated to initiating party to inform them which protocol version of the flow they are running.",
+  "namespace": "net.corda.data.flow.event.session",
+  "fields": []
+}
diff --git a/gradle.properties b/gradle.properties
index 46577e1014..b775b41a9c 100644
--- a/gradle.properties
+++ b/gradle.properties
@@ -9,7 +9,7 @@ cordaProductVersion = 5.1.0
 # NOTE: update this each time this module contains a breaking change
 ## NOTE: currently this is a top level revision, so all API versions will line up, but this could be moved to
 ##   a per module property in which case module versions can change independently.
-cordaApiRevision = 20
+cordaApiRevision = 21
 
 # Main
 kotlinVersion = 1.8.21