diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4cd989e5a..e17de756c 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,27 @@
+# 0.4.0
+
+- SMP server implementation and [SMP protocol](https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md) changes:
+  - support 3072 bit RSA key size
+  - add SMP queue quotas
+  - set default transport block size to 4096 bits
+  - allow SMP client to change transport block size during transport connection handshake
+- SMP agent implementation and protocol changes:
+  - additional connection confirmation step for initiating party
+  - automatically resume subscribed duplex connections once transport connection is resumed
+  - passing an arbitrary binary information between parties during the duplex connection handshake - can be used to identify parties
+  - asynchronous duplex connection handshake - the parties do not have to be online at the same time
+  - asynchronous message delivery - the agent does not need transport connection to accept client messages for delivery
+  - additional confirmation of message reception from the client to prevent message loss in case of process termination
+  - set transport block size to 8192 bits (in the future the agent protocol can allow to have different block sizes for different duplex connections)
+  - added client commands and notifications (see [agent protocol](https://github.com/simplex-chat/simplexmq/blob/master/protocol/agent-protocol.md)):
+    - `REQ` - the notification about joining party establishing connection
+    - `ACPT` - the command to accept connection with the joining party
+    - `INFO` - the notification with the information from the initiating party
+    - `DOWN`/`UP` - the notifications about losing/resuming the connection
+    - `ACK` - the command to confirm that the message reception/processing is complete
+    - `MID` - the response to `SEND` confirming that the message is accepted by the agent
+    - `MERR` - the notification about permanent message delivery error (e.g., `ERR AUTH` indicating that the queue was removed)
+
 # 0.3.2
 
 - Support websockets
diff --git a/src/Simplex/Messaging/Agent/Protocol.hs b/src/Simplex/Messaging/Agent/Protocol.hs
index 518b4219d..44e42cdd4 100644
--- a/src/Simplex/Messaging/Agent/Protocol.hs
+++ b/src/Simplex/Messaging/Agent/Protocol.hs
@@ -312,7 +312,7 @@ data SMPServer = SMPServer
   deriving (Eq, Ord, Show)
 
 instance IsString SMPServer where
-  fromString = parseString . parseAll $ smpServerP
+  fromString = parseString $ parseAll smpServerP
 
 -- | SMP agent connection alias.
 type ConnId = ByteString
diff --git a/src/Simplex/Messaging/Crypto.hs b/src/Simplex/Messaging/Crypto.hs
index 10e7ad5b5..ccd8f5f90 100644
--- a/src/Simplex/Messaging/Crypto.hs
+++ b/src/Simplex/Messaging/Crypto.hs
@@ -169,10 +169,10 @@ instance PrivateKey APrivateKey where
           else Just $ PublicKey k
 
 instance IsString FullPrivateKey where
-  fromString = parseString (decode >=> decodePrivKey)
+  fromString = parseString $ decode >=> decodePrivKey
 
 instance IsString PublicKey where
-  fromString = parseString (decode >=> decodePubKey)
+  fromString = parseString $ decode >=> decodePubKey
 
 instance ToField SafePrivateKey where toField = toField . encodePrivKey
 
diff --git a/src/Simplex/Messaging/Transport.hs b/src/Simplex/Messaging/Transport.hs
index d8869f436..83d353ec9 100644
--- a/src/Simplex/Messaging/Transport.hs
+++ b/src/Simplex/Messaging/Transport.hs
@@ -66,6 +66,7 @@ import Data.Functor (($>))
 import Data.Maybe(fromMaybe)
 import Data.Set (Set)
 import qualified Data.Set as S
+import Data.String
 import Data.Word (Word32)
 import GHC.Generics (Generic)
 import GHC.IO.Exception (IOErrorType (..))
@@ -74,7 +75,7 @@ import Generic.Random (genericArbitraryU)
 import Network.Socket
 import Network.Transport.Internal (decodeNum16, decodeNum32, encodeEnum16, encodeEnum32, encodeWord32)
 import qualified Simplex.Messaging.Crypto as C
-import Simplex.Messaging.Parsers (parse, parseAll, parseRead1)
+import Simplex.Messaging.Parsers (parse, parseAll, parseRead1, parseString)
 import Simplex.Messaging.Util (bshow, liftError)
 import System.IO
 import System.IO.Error
@@ -213,11 +214,14 @@ trimCR s = if B.last s == '\r' then B.init s else s
 data SMPVersion = SMPVersion Int Int Int Int
   deriving (Eq, Ord)
 
+instance IsString SMPVersion where
+  fromString = parseString $ parseAll smpVersionP
+
 major :: SMPVersion -> (Int, Int)
 major (SMPVersion a b _ _) = (a, b)
 
 currentSMPVersion :: SMPVersion
-currentSMPVersion = SMPVersion 0 3 2 0
+currentSMPVersion = "0.4.0.0"
 
 serializeSMPVersion :: SMPVersion -> ByteString
 serializeSMPVersion (SMPVersion a b c d) = B.intercalate "." [bshow a, bshow b, bshow c, bshow d]
diff --git a/tests/AgentTests.hs b/tests/AgentTests.hs
index 545bcece4..73dd732c2 100644
--- a/tests/AgentTests.hs
+++ b/tests/AgentTests.hs
@@ -108,10 +108,10 @@ testDuplexConnection _ alice bob = do
   alice <# ("", "bob", CON)
   alice #: ("3", "bob", "SEND :hello") #> ("3", "bob", MID 1)
   alice <# ("", "bob", SENT 1)
-  alice #: ("4", "bob", "SEND :how are you?") #> ("4", "bob", MID 2)
-  alice <# ("", "bob", SENT 2)
   bob <#= \case ("", "alice", Msg "hello") -> True; _ -> False
   bob #: ("12", "alice", "ACK 1") #> ("12", "alice", OK)
+  alice #: ("4", "bob", "SEND :how are you?") #> ("4", "bob", MID 2)
+  alice <# ("", "bob", SENT 2)
   bob <#= \case ("", "alice", Msg "how are you?") -> True; _ -> False
   bob #: ("13", "alice", "ACK 2") #> ("13", "alice", OK)
   bob #: ("14", "alice", "SEND 9\nhello too") #> ("14", "alice", MID 3)
@@ -141,10 +141,10 @@ testDuplexConnRandomIds _ alice bob = do
   alice <# ("", bobConn, CON)
   alice #: ("2", bobConn, "SEND :hello") #> ("2", bobConn, MID 1)
   alice <# ("", bobConn, SENT 1)
-  alice #: ("3", bobConn, "SEND :how are you?") #> ("3", bobConn, MID 2)
-  alice <# ("", bobConn, SENT 2)
   bob <#= \case ("", c, Msg "hello") -> c == aliceConn; _ -> False
   bob #: ("12", aliceConn, "ACK 1") #> ("12", aliceConn, OK)
+  alice #: ("3", bobConn, "SEND :how are you?") #> ("3", bobConn, MID 2)
+  alice <# ("", bobConn, SENT 2)
   bob <#= \case ("", c, Msg "how are you?") -> c == aliceConn; _ -> False
   bob #: ("13", aliceConn, "ACK 2") #> ("13", aliceConn, OK)
   bob #: ("14", aliceConn, "SEND 9\nhello too") #> ("14", aliceConn, MID 3)
@@ -166,10 +166,10 @@ testSubscription _ alice1 alice2 bob = do
   (alice1, "alice") `connect` (bob, "bob")
   bob #: ("12", "alice", "SEND 5\nhello") #> ("12", "alice", MID 1)
   bob <# ("", "alice", SENT 1)
-  bob #: ("13", "alice", "SEND 11\nhello again") #> ("13", "alice", MID 2)
-  bob <# ("", "alice", SENT 2)
   alice1 <#= \case ("", "bob", Msg "hello") -> True; _ -> False
   alice1 #: ("1", "bob", "ACK 1") #> ("1", "bob", OK)
+  bob #: ("13", "alice", "SEND 11\nhello again") #> ("13", "alice", MID 2)
+  bob <# ("", "alice", SENT 2)
   alice1 <#= \case ("", "bob", Msg "hello again") -> True; _ -> False
   alice1 #: ("2", "bob", "ACK 2") #> ("2", "bob", OK)
   alice2 #: ("21", "bob", "SUB") #> ("21", "bob", OK)