diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 23fda6a0a..04a2acdf0 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -49,7 +49,7 @@ jobs:
         run: cabal build --enable-tests
 
       - name: Test
-        timeout-minutes: 30
+        timeout-minutes: 40
         shell: bash
         run: cabal test --test-show-details=direct
 
diff --git a/notes-flow.txt b/notes-flow.txt
new file mode 100644
index 000000000..93f984509
--- /dev/null
+++ b/notes-flow.txt
@@ -0,0 +1,23 @@
+common:
+  corrId - random BS, used as CbNonce
+  entityId - p2r tlsUniq
+
+# setup
+s->p: "proxy", uri, auth?
+  # unless connected
+  p->r: "p_handshake"
+  p<-r: "r_key", tls-signed dh pub
+s<-r: "r_key", tls-signed dh pub # reply entityId contains tlsUniq
+
+# working
+s ; generate random dh priv, make shared secret
+s->p: s2r("forward", random dh pub, SEND command blob)
+  p->r: p2r("forward", random dh pub, s2r("forward", ...)))
+    r->c@ "msg", ...
+  p<-r: p2r("r_res", s2r("ok" / "error", error))
+s<-p@ s2r("ok" / "error", error)
+
+# expired
+  p<-r@ p2r("error", "key expired")
+s<-p@ "error", "key expired"
+s ; reconnect
\ No newline at end of file
diff --git a/rfcs/2023-09-12-second-relays.md b/rfcs/2023-09-12-second-relays.md
index 3721ee721..cad6c4a92 100644
--- a/rfcs/2023-09-12-second-relays.md
+++ b/rfcs/2023-09-12-second-relays.md
@@ -2,9 +2,9 @@
 
 ## Problem
 
-SMP protocol relays are chosen and can be controlled by the message recipients. It means that the recipients can find out IP addresses of message senders by modifying SMP relay code (or by using proxies and timing correlation), unless the senders use VPN or some overlay network. Tor is an audequate solution in most cases to mitigate it, but it requires additional technical knowledge to install and configure (even installing Orbot on Android is seen as "complex" by many users), and reduces usability because of higher latency.
+SMP protocol relays are chosen and can be controlled by the message recipients. It means that the recipients can find out IP addresses of message senders by modifying SMP relay code (or by using proxies and timing correlation), unless the senders use VPN or some overlay network. Tor is an adequate solution in most cases to mitigate it, but it requires additional technical knowledge to install and configure (even installing Orbot on Android is seen as "complex" by many users), and reduces usability because of higher latency.
 
-The lack of in-built IP address protection is the main concern of many users, particularly given that most people do not realise that it is lacking by default - without transport protection SimpleX is not perceived as a "whole product".
+The lack of in-built IP address protection is the main concern of many users, particularly given that most people do not realize that it is lacking by default - without transport protection SimpleX is not perceived as a "whole product".
 
 Similarly, XFTP protocol relays are chosen by senders, and they can be used to detect file recipients' IP addresses.
 
@@ -43,7 +43,7 @@ Overall, this is not a viable or even appropriate option for the current stage.
 
 3. SMP / XFTP proxy.
 
-Introduce SMP and XFTP protocol extenstions to allow message senders and file recipients to delegate the tasks of sending messages and receiving files to the proxies, so that peer-chosen relays can only observe IP addresses of the proxies and not of the users.
+Introduce SMP and XFTP protocol extensions to allow message senders and file recipients to delegate the tasks of sending messages and receiving files to the proxies, so that peer-chosen relays can only observe IP addresses of the proxies and not of the users.
 
 Pros:
 - no dependency on and lower latency than via Tor
@@ -68,7 +68,7 @@ Below considers this design.
 
 2. SMP proxy should not be able to observe queue addresses and their count on the destination relays. This requirement is not needed for XFTP proxies, as each file chunk is downloaded only once, so there is no need to hide its address.
 
-3. There must be no identifiers and cyphertext in common in outgoing and incoming traffic inside TLS (the current designs have this quality).
+3. There must be no identifiers and ciphertext in common in outgoing and incoming traffic inside TLS (the current designs have this quality).
 
 4. Traffic between the client and destination relays must be e2e encrypted, with MITM-by-proxy mitigated, relying on the relay identity (certificate fingerprint), ideally without any additional fingerprint in relay address.
 
@@ -97,11 +97,11 @@ This would also reduce the difference in how the traffic looks to the observer -
 
 The flow of the messages will be:
 
-1. Client requests proxy to create session with the relay by sending `server` command with the SMP relay address and optional proxy basic AUTH (below). It should be possible to batch multiple session requests into one block, to reduce traffic.
+1. Client requests proxy to create session with the relay by sending `PRXY` command with the SMP relay address and optional proxy basic AUTH (below). It should be possible to batch multiple session requests into one block, to reduce traffic.
 
-2. Proxy connects to SMP relay, negotiating a shared secret in the handshake that will be used to encrypt all sender blocks inside TLS (proxy-relay encryption). SMP relay also returns in handshake its temporary DH key to agree e2e encryption with the client (sender-relay encryption, to hide metadata sent to the destination relay from proxy).
+2. Proxy connects to SMP relay, negotiating a shared secret via a handshake headers - it will be used to encrypt all sender blocks inside TLS (proxy-relay encryption). DH key returned by SMP relay in handshake will also be used to encrypt client commands, combining it with random per-command keys (sender-relay encryption, to hide metadata sent to the destination relay from proxy).
 
-3. Proxy replies with `server_id` command including relay session ID to identify it in further requests, relay DH key for e2e encryption with the client - this key is signed with the TLS online private key associated with the certificate (its fingerprint is included in the relay address), and the TLS session ID between proxy and relay (this session ID must be used in transmissions, to mitigate replay attacks as before).
+3. Proxy replies to sender with `PKEY` message using "entityId" transmission field to indicate session ID for using in further requests, relay DH key for _s2r_ encryption with the client - this key is signed with the TLS online private key associated with the certificate (its fingerprint is included in the relay address), and the TLS session ID between proxy and relay (this session ID must be used in transmissions, to mitigate replay attacks as before).
 
 A possible attack here is that proxy can use this TLS session to replay commands received from the client. Possibly, it could be mitigated with a bloom filter per proxy/SMP relay connection that would reject the repeated DH keys (that need to be used for replay), and also with DH key expiration (this mitigation should allow some acceptable rate of false positives from the bloom filter).
 
@@ -113,11 +113,11 @@ It is important that the same public key from destination relay is returned to a
 
 *Unrelated cosideration for SMP protocol privacy improvement*: instead of signing commands to the destination relay, the sender could have a ratchet per queue agreed with the destination relay that would simply use authenticated encryption with per-message symmetric key to encrypt the message on the way to relay, and this encryption would be used as a proof of sender.
 
-4. Now the client sends `forward` to proxy, which it then forwards to SMP relay, applying additional encryption layer.
+4. Now the client sends `PFWD` to proxy, which it then forwards to SMP relay as `RFWD`, applying _p2r_ encryption layer.
 
-5. SMP relay sends `response` to proxy applying additional encryption layer, which it then forwards to the client removing the additional encryption layer.
+5. SMP relay sends `RRES` to proxy applying _p2r_ encryption layer, which it then forwards to the client as `PRES`, removing the _p2r_ encryption layer.
 
-Effectively it works as a simplified two-hop onion routing with the first relay (proxy) chosen by the sending client and the second relay chosen by the recipient, not only protecting senders' IP addresses from the recipients' relays, but also preventing recipients relays from correlating senders' traffic to different queues, as TLS session is owned by the proxy now and it mixes the traffic from multiple senders. To correlate traffic to users, proxy and relay would have to combine their information. SMP relays are still able to correlate traffic to receiving users via transport session.
+Effectively it works as a simplified two-hop onion routing with the first relay (proxy) chosen by the sending client and the second relay chosen by the recipient, not only protecting senders' IP addresses from the recipients' relays, but also preventing recipients' relays from correlating senders' traffic to different queues, as TLS session is owned by the proxy now and it mixes the traffic from multiple senders. To correlate traffic to users, proxy and relay would have to combine their information. SMP relays are still able to correlate traffic to receiving users via transport session.
 
 Sequence diagram for sending the message via SMP proxy:
 
@@ -126,33 +126,33 @@ Sequence diagram for sending the message via SMP proxy:
 |  sending  |               |    SMP    |                     |    SMP    |              | receiving |
 |  client   |               |   proxy   |                     |   relay   |              |  client   |
 -------------               -------------                     -------------              -------------
-     |       `server`             |                                 |                          |
-     | -------------------------> |   create TLS session, get keys  |                          |
+     |           `PRXY`           |                                 |                          |
+     | -------------------------> |                                 |                          |
      |                            | ------------------------------> |                          |
-     |        `server_id`         |       (if doesn't exist)        |                          |
+     |                            |          SMP handshake          |                          |
+     |                            | <------------------------------ |                          |
+     |           `PKEY`           |                                 |                          |
      | <------------------------- |                                 |                          |
      |                            |                                 |                          |
-     | TLS(F:s2r(SEND(e2e(msg)))) |                                 |                          |
-     | -------------------------> | TLS(F:p2r(s2r(SEND(e2e(msg))))) |                          |
+     |        `PFWD` (s2r)        |                                 |                          |
+     | -------------------------> |                                 |                          |
+     |                            |           `RFWD` (p2r)          |                          |
      |                            | ------------------------------> |                          |
-     |                            |                                 |                          |
-     |                            |     TLS(R:p2r(s2r(OK/ERR)))     |                          |
-     |     TLS(R:s2r(OK/ERR))     | <------------------------------ |                          |
-     | <------------------------- |                                 | TLS(MSG(r2c(e2e(msg))))  |
-     |                            |                                 | -----------------------> |
-     |                            |                                 |                          |
-     |                            |                                 |        TLS(ACK)          |
+     |                            |           `RRES` (p2r)          |                          |
+     |                            | <------------------------------ |                          |
+     |        `PRES` (s2r)        |                                 |           `MSG`          |
+     | <------------------------- |                                 | -----------------------> |
+     |                            |                                 |           `ACK`          |
      |                            |                                 | <----------------------- |
      |                            |                                 |                          |
      |                            |                                 |                          |
-
 ```
 
-Below diagram shows the encrypttion layers for `forward` and `response` commands:
+Below diagram shows the encrypttion layers for `PFWD`/`RFWD` commands and `RRES`/`PRES` responses:
 
-- s2r (added) - encryption between client and SMP relay, with relay key returned in server_id command, with MITM by proxy mitigated by verifying the certificate fingerprint included in the relay address.
+- s2r (added) - encryption between client and SMP relay, with relay key returned in relay handshake, with MITM by proxy mitigated by verifying the certificate fingerprint included in the relay address.
 - e2e (exists now) - end-to-end encryption per SMP queue, with double ratchet e2e encryption inside it.
-- p2r (added) - additional encryption between proxy and SMP relay with key agreed in the handshake, to mitigate traffic correlation inside TLS. This key could also be signed by the same certificate, if we don't want to rely on TLS security.
+- p2r (added) - additional encryption between proxy and SMP relay with the shared secret agreed in the handshake, to mitigate traffic correlation inside TLS.
 - r2c (exists now) additional encryption between SMP relay and client to prevent traffic correlation inside TLS.
 
 ```
@@ -167,30 +167,85 @@ Below diagram shows the encrypttion layers for `forward` and `response` commands
 -----------------             -----------------  -- TLS --  -----------------             -----------------
 ```
 
-When proxy connects to SMP relay it would indicate in the handshake that it will use proxy protocol and the SMP relay would expect the same `forward` commands and reply with `response`s.
+Question: should proxy declare its role in handshake? When proxy connects to SMP relay it would indicate in the handshake that it will act as a proxy and the SMP relay would expect the same `forward` commands and reply with `response`s.
 
-Below syntax aims to fit in 16kb block using spare capacity in SMP protocol.
+Common SMP transmission format (v4), for reference:
 
 ```abnf
-proxy_block = padded(proxy_transmission, 16384)
-proxy_transmission = corr_id relay_session_id proxy_command
-corr_id = length *8 OCTET
-proxy_command = server / server_id / forward / response / error
-server = "S" address [relay_basic_auth] ; creates transport session between proxy and relay
-server_id = "I" relay_session_id tls_session_id signed_relay_key ;
-    ; session_id is the TLS session ID between proxy and relay, it has to be included inside encrypted block to prevent replay attacks
-forward = %s"F" random_dh_pub_key encrypted_block ; it's important that a new key is used for each command, to prevent any correlation by proxy or by destination relay
-response = %s"R" encrypted_block; response received from the destination SMP relay
-relay_session_id = length *8 OCTET
-error = %s"E" error
+paddedTransmission = <padded(transmission), 16384>
+transmission = signature signed
+signature = 0 ; empty signatures here
+signed = sessionIdentifier corrId entityId (smpCommand / brokerMsg)
 ```
 
-The overhead is: 1+8 (corrId) + 1+8 (relay_session_id) + 1 (command) + 1+32 (random_dh_pub_key) + 2 (original length) + 16 (auth tag for e2e encryption) + 16 (auth tag for proxy to relay encryption) = 86 bytes. The reserve for sent messages in SMP is ~84 bytes, so it should about fit with some reduced bytes somewhere.
+- `corrId` is fully random each time and used as a nonce for encrypted blocks.
+- `entityId` carries tlsUniq from the current proxy-to-relay connection.
+- `smpCommand` gets extended with `s2p_command / p2r_command`.
+- `brokerMsg` gets extended with `r_key / r_response`.
 
-Another possible design is to allow mixing sent messages and normal SMP commands in the same transport connection, but it can make fitting in the block a bit harder, additional overhead would be: 1 (transmission count) + 2 (transmission size) + 1 (empty signature) = 4 bytes.
+```abnf
+s2p_command = proxy / forward
+p2r_command = p_handshake ; forward is
+proxy = %s"PRXY" SP relayUri SP basicAuth
+relayUri = length %s"smp://" serverIdentity "@" srvHost [":" port]
+forward = %s"PFWD" SP dhPublic SP encryptedBlock
+r_key = %s"PKEY" SP dhPublic
+r_response = %s"RRES" SP encryptedBlock
+dhPublic = length x509encoded
+```
 
 The above assumes that the client can only send one message to an SMP relay and then has to wait for response before sending the next message. Missing the response would cause re-delivery (further improvement is possible when proxy detects these redelieveries and not send them to relays but simply reply with the same response).
 
+### Implementation considerations for the client
+
+While client/server protocol is rather straightforward to implement, and it is already working, there are some decisions to make about how the client makes decisions about.
+
+1. When to use proxy and when to connect directly to the destination relay.
+
+While from the perspective of threat model improvement it may be beneficial to always use the proxy, choosing the proxy that is different from other relays in the connection, initially we need to make it opt-in, with an option to only use it for unknown destination relays, to minimize any unexpected adverse effect on the delivery latency.
+
+Proxy mode will be passed from the client via NetworkConfig.
+
+2. Which proxying relays to use.
+
+Ability to request access to the session with the destination relay (and to create such session) is protected with the same basic auth approach as creating queues - the logic here is that opening private servers to all users as proxies would increase the scenarios for DoS attacks (which is the case with the public servers).
+
+The open question is whether the client should choose proxies from:
+- all configured relays.
+- there should be a subset of configured relays.
+- there should be a separate list.
+
+E.g., there could be a second toggle in the relay configuration to allow using relay as proxy, in addition to the current toggle that allows creating queues.
+
+For simplicity, initially we will just use all enabled relays as potential proxies.
+
+3. How many proxying relays should be used during one session.
+
+This is not a simple question, and it creates a contradiction between two risks:
+- collusion between proxies and destination relays simplifies correlating sending clients by session - from the point of view of this risk, clients should follow the same policy for creating connections with proxies, that is to create a new connection for each user profile, and if transport isolation is set to "per connection" - for each destination queue.
+- traffic correlation by observable traffic sessions (particularly if an attacker can observe user's ISP traffic or multiple proxies) - from this point of view, it would be beneficial to use fewer proxies and fewer connections with proxies and see the risk of proxy colluding with the destination relay as lower than the risk of traffic observation that in the case of multiple sessions would allow to correlate traffic to rarely used destination relays (any private self-hosted relays) and the traffic of the user to a given proxy, to prove the fact of user communicating with the destination relay via the proxy.
+
+While we can transfer this choice on the users, it seems a complex decision to make, and overall the second risk (traffic correlation) seems more important to address than the first.
+
+In any case possible options are:
+1. Extreme option 1: Create a new proxy session, with the new random proxy, for each potential transport session that would exist if the user were to be connected to destination relays directly. That is, never to mix access to multiple relays from multiple user profiles (and in case of per-connection isolation, to multiple queues) into a one client session with proxy. This is a rather radical option that nullifies any advantages of having fewer sessions with proxies than there would have been with the destination relays and removes any benefits of batching destination server session requests (PRXY comands).
+2. Extreme option 2: Use only one proxy session at the time, mixing traffic from all user profiles and to all destination servers (and for all queues) into a session with one proxy. This minimizes the risks of traffic correlation in case of non-colluding proxy, but maximises the risk in case it colludes with the destination relays.
+3. Balanced option: Use one proxy session per user profile, but mix traffic to multiple queues irrespective of connection isolation option and to all destination servers. Given that connection isolation is an experimental option, this makes the most sense, but it would have to be disclosed.
+4. Less balanced option: take connection isolation option into account and create a new proxy connection for each destination queue. This feels worse than option 3.
+
+If option 3 is chosen, then the transport session key with the proxy would be different from the transport session key with the relay - proxy session will only use UserId as the key, and the relay session uses (UserId, Server, Maybe EntityId) as the key.
+
+If option 4 is chosen, the keys would also be different, as the proxy would then use (UserId, Maybe (Server, EntityId)) as the key.
+
+We could potentially key proxy sessions (and create proxy connections) per each destination relay, in the same way as we key relays themselves, but it seems to have the least sense, as we neither achieve isolation by queue in case proxy and destination relay collude, nor we sufficiently protect from traffic correlation by any observers.
+
+The implemented design is this:
+- for each destination relay a random proxy is chosen and used to send all messages - all requests from a client coalesce to a single session.
+- transport isolation mode is taken into account, that is if per-connection isolation is enabled, then a separate proxy connection will be created for each messaging queue.
+- supported modes when proxy is used: always, for unknown relays, for unknown relays when IP address is not protected, never.
+
+This decision is made because the argument for protection against collusion between proxy and relay and more balanced traffic distribution is stronger than the argument for protection against traffic correlation, because even mixing all messages to one proxy connection does not provide protection against traffic correlation by time, so in any case it requires adding delays.
+
 ### Threat model for SMP proxy and changes to threat model for SMP
 
 #### SMP proxy
diff --git a/simplexmq.cabal b/simplexmq.cabal
index 92b6a9cfb..bd0883c23 100644
--- a/simplexmq.cabal
+++ b/simplexmq.cabal
@@ -652,6 +652,7 @@ test-suite simplexmq-test
       ServerTests
       SMPAgentClient
       SMPClient
+      SMPProxyTests
       Util
       XFTPAgent
       XFTPCLI
diff --git a/src/Simplex/FileTransfer/Client.hs b/src/Simplex/FileTransfer/Client.hs
index 468df6157..7875542a6 100644
--- a/src/Simplex/FileTransfer/Client.hs
+++ b/src/Simplex/FileTransfer/Client.hs
@@ -51,13 +51,13 @@ import Simplex.Messaging.Protocol
     RecipientId,
     SenderId,
   )
-import Simplex.Messaging.Transport (ALPN, HandshakeError (VERSION), THandleAuth (..), THandleParams (..), TransportError (..), TransportPeer (..), supportedParameters)
+import Simplex.Messaging.Transport (ALPN, THandleAuth (..), THandleParams (..), TransportError (..), TransportPeer (..), supportedParameters)
 import Simplex.Messaging.Transport.Client (TransportClientConfig, TransportHost, alpn)
 import Simplex.Messaging.Transport.HTTP2
 import Simplex.Messaging.Transport.HTTP2.Client
 import Simplex.Messaging.Transport.HTTP2.File
 import Simplex.Messaging.Util (bshow, liftEitherWith, liftError', tshow, whenM)
-import Simplex.Messaging.Version (compatibleVersion, pattern Compatible)
+import Simplex.Messaging.Version
 import UnliftIO
 import UnliftIO.Directory
 
@@ -99,22 +99,24 @@ defaultXFTPClientConfig =
 
 getXFTPClient :: TransportSession FileResponse -> XFTPClientConfig -> (XFTPClient -> IO ()) -> IO (Either XFTPClientError XFTPClient)
 getXFTPClient transportSession@(_, srv, _) config@XFTPClientConfig {clientALPN, xftpNetworkConfig, serverVRange} disconnected = runExceptT $ do
-  let tcConfig = (transportClientConfig xftpNetworkConfig) {alpn = clientALPN}
-      http2Config = xftpHTTP2Config tcConfig config
-      username = proxyUsername transportSession
+  let username = proxyUsername transportSession
       ProtocolServer _ host port keyHash = srv
   useHost <- liftEither $ chooseTransportHost xftpNetworkConfig host
+  let tcConfig = (transportClientConfig xftpNetworkConfig useHost) {alpn = clientALPN}
+      http2Config = xftpHTTP2Config tcConfig config
   clientVar <- newTVarIO Nothing
   let usePort = if null port then "443" else port
       clientDisconnected = readTVarIO clientVar >>= mapM_ disconnected
   http2Client <- liftError' xftpClientError $ getVerifiedHTTP2Client (Just username) useHost usePort (Just keyHash) Nothing http2Config clientDisconnected
   let HTTP2Client {sessionId, sessionALPN} = http2Client
-      thParams0 = THandleParams {sessionId, blockSize = xftpBlockSize, thVersion = VersionXFTP 1, thAuth = Nothing, implySessId = False, batch = True}
+      v = VersionXFTP 1
+      thServerVRange = versionToRange v
+      thParams0 = THandleParams {sessionId, blockSize = xftpBlockSize, thVersion = v, thServerVRange, thAuth = Nothing, implySessId = False, batch = True}
   logDebug $ "Client negotiated handshake protocol: " <> tshow sessionALPN
   thParams@THandleParams {thVersion} <- case sessionALPN of
     Just "xftp/1" -> xftpClientHandshakeV1 serverVRange keyHash http2Client thParams0
     Nothing -> pure thParams0
-    _ -> throwError $ PCETransportError (TEHandshake VERSION)
+    _ -> throwError $ PCETransportError TEVersion
   logDebug $ "Client negotiated protocol: " <> tshow thVersion
   let c = XFTPClient {http2Client, thParams, transportSession, config}
   atomically $ writeTVar clientVar $ Just c
@@ -123,9 +125,10 @@ getXFTPClient transportSession@(_, srv, _) config@XFTPClientConfig {clientALPN,
 xftpClientHandshakeV1 :: VersionRangeXFTP -> C.KeyHash -> HTTP2Client -> THandleParamsXFTP 'TClient -> ExceptT XFTPClientError IO (THandleParamsXFTP 'TClient)
 xftpClientHandshakeV1 serverVRange keyHash@(C.KeyHash kh) c@HTTP2Client {sessionId, serverKey} thParams0 = do
   shs@XFTPServerHandshake {authPubKey = ck} <- getServerHandshake
-  (v, sk) <- processServerHandshake shs
+  (vr, sk) <- processServerHandshake shs
+  let v = maxVersion vr
   sendClientHandshake XFTPClientHandshake {xftpVersion = v, keyHash}
-  pure thParams0 {thAuth = Just THAuthClient {serverPeerPubKey = sk, serverCertKey = ck, sessSecret = Nothing}, thVersion = v}
+  pure thParams0 {thAuth = Just THAuthClient {serverPeerPubKey = sk, serverCertKey = ck, sessSecret = Nothing}, thVersion = v, thServerVRange = vr}
   where
     getServerHandshake :: ExceptT XFTPClientError IO XFTPServerHandshake
     getServerHandshake = do
@@ -133,13 +136,13 @@ xftpClientHandshakeV1 serverVRange keyHash@(C.KeyHash kh) c@HTTP2Client {session
       HTTP2Response {respBody = HTTP2Body {bodyHead = shsBody}} <-
         liftError' (const $ PCEResponseError HANDSHAKE) $ sendRequest c helloReq Nothing
       liftHS . smpDecode =<< liftHS (C.unPad shsBody)
-    processServerHandshake :: XFTPServerHandshake -> ExceptT XFTPClientError IO (VersionXFTP, C.PublicKeyX25519)
+    processServerHandshake :: XFTPServerHandshake -> ExceptT XFTPClientError IO (VersionRangeXFTP, C.PublicKeyX25519)
     processServerHandshake XFTPServerHandshake {xftpVersionRange, sessionId = serverSessId, authPubKey = serverAuth} = do
       unless (sessionId == serverSessId) $ throwError $ PCEResponseError SESSION
-      case xftpVersionRange `compatibleVersion` serverVRange of
-        Nothing -> throwError $ PCEResponseError HANDSHAKE
-        Just (Compatible v) ->
-          fmap (v,) . liftHS $ do
+      case xftpVersionRange `compatibleVRange` serverVRange of
+        Nothing -> throwError $ PCETransportError TEVersion
+        Just (Compatible vr) ->
+          fmap (vr,) . liftHS $ do
             let (X.CertificateChain cert, exact) = serverAuth
             case cert of
               [_leaf, ca] | XV.Fingerprint kh == XV.getFingerprint ca X.HashSHA256 -> pure ()
@@ -185,9 +188,11 @@ xftpClientError = \case
 
 sendXFTPCommand :: forall p. FilePartyI p => XFTPClient -> C.APrivateAuthKey -> XFTPFileId -> FileCommand p -> Maybe XFTPChunkSpec -> ExceptT XFTPClientError IO (FileResponse, HTTP2Body)
 sendXFTPCommand c@XFTPClient {thParams} pKey fId cmd chunkSpec_ = do
+  -- TODO random corrId
+  let corrIdUsedAsNonce = ""
   t <-
     liftEither . first PCETransportError $
-      xftpEncodeAuthTransmission thParams pKey ("", fId, FileCmd (sFileParty @p) cmd)
+      xftpEncodeAuthTransmission thParams pKey (corrIdUsedAsNonce, fId, FileCmd (sFileParty @p) cmd)
   sendXFTPTransmission c t chunkSpec_
 
 sendXFTPTransmission :: XFTPClient -> ByteString -> Maybe XFTPChunkSpec -> ExceptT XFTPClientError IO (FileResponse, HTTP2Body)
diff --git a/src/Simplex/FileTransfer/Protocol.hs b/src/Simplex/FileTransfer/Protocol.hs
index 418e48482..c55b327f8 100644
--- a/src/Simplex/FileTransfer/Protocol.hs
+++ b/src/Simplex/FileTransfer/Protocol.hs
@@ -48,6 +48,7 @@ import Simplex.Messaging.Protocol
     SndPublicAuthKey,
     Transmission,
     TransmissionForAuth (..),
+    CorrId (..),
     encodeTransmission,
     encodeTransmissionForAuth,
     messageTagP,
@@ -328,7 +329,7 @@ checkParty' c = case testEquality (sFileParty @p) (sFileParty @p') of
 xftpEncodeAuthTransmission :: ProtocolEncoding XFTPVersion e c => THandleParams XFTPVersion 'TClient -> C.APrivateAuthKey -> Transmission c -> Either TransportError ByteString
 xftpEncodeAuthTransmission thParams@THandleParams {thAuth} pKey (corrId, fId, msg) = do
   let TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth thParams (corrId, fId, msg)
-  xftpEncodeBatch1 . (,tToSend) =<< authTransmission thAuth (Just pKey) corrId tForAuth
+  xftpEncodeBatch1 . (,tToSend) =<< authTransmission thAuth (Just pKey) (C.cbNonce $ bs corrId) tForAuth
 
 xftpEncodeTransmission :: ProtocolEncoding XFTPVersion e c => THandleParams XFTPVersion p -> Transmission c -> Either TransportError ByteString
 xftpEncodeTransmission thParams (corrId, fId, msg) = do
diff --git a/src/Simplex/FileTransfer/Server.hs b/src/Simplex/FileTransfer/Server.hs
index 7b6787a43..41c652ea2 100644
--- a/src/Simplex/FileTransfer/Server.hs
+++ b/src/Simplex/FileTransfer/Server.hs
@@ -63,7 +63,7 @@ import Simplex.Messaging.Transport.HTTP2.File (fileBlockSize)
 import Simplex.Messaging.Transport.HTTP2.Server
 import Simplex.Messaging.Transport.Server (runTCPServer, tlsServerCredentials)
 import Simplex.Messaging.Util
-import Simplex.Messaging.Version (isCompatible)
+import Simplex.Messaging.Version
 import System.Exit (exitFailure)
 import System.FilePath ((</>))
 import System.IO (hPrint, hPutStrLn, universalNewlineMode)
@@ -91,10 +91,10 @@ runXFTPServerBlocking started cfg = newXFTPServerEnv cfg >>= runReaderT (xftpSer
 
 data Handshake
   = HandshakeSent C.PrivateKeyX25519
-  | HandshakeAccepted (THandleAuth 'TServer) VersionXFTP
+  | HandshakeAccepted (THandleParams XFTPVersion 'TServer)
 
 xftpServer :: XFTPServerConfig -> TMVar Bool -> M ()
-xftpServer cfg@XFTPServerConfig {xftpPort, transportConfig, inactiveClientExpiration, fileExpiration} started = do
+xftpServer cfg@XFTPServerConfig {xftpPort, transportConfig, inactiveClientExpiration, fileExpiration, xftpServerVRange} started = do
   mapM_ (expireServerFiles Nothing) fileExpiration
   restoreServerStats
   raceAny_ (runServer : expireFilesThread_ cfg <> serverStatsThread_ cfg <> controlPortThread_ cfg) `finally` stopServer
@@ -111,7 +111,9 @@ xftpServer cfg@XFTPServerConfig {xftpPort, transportConfig, inactiveClientExpira
       let cleanup sessionId = atomically $ TM.delete sessionId sessions
       liftIO . runHTTP2Server started xftpPort defaultHTTP2BufferSize serverParams transportConfig inactiveClientExpiration cleanup $ \sessionId sessionALPN r sendResponse -> do
         reqBody <- getHTTP2Body r xftpBlockSize
-        let thParams0 = THandleParams {sessionId, blockSize = xftpBlockSize, thVersion = VersionXFTP 1, thAuth = Nothing, implySessId = False, batch = True}
+        let v = VersionXFTP 1
+            thServerVRange = versionToRange v
+            thParams0 = THandleParams {sessionId, blockSize = xftpBlockSize, thVersion = v, thServerVRange, thAuth = Nothing, implySessId = False, batch = True}
             req0 = XFTPTransportRequest {thParams = thParams0, request = r, reqBody, sendResponse}
         flip runReaderT env $ case sessionALPN of
           Nothing -> processRequest req0
@@ -121,12 +123,12 @@ xftpServer cfg@XFTPServerConfig {xftpPort, transportConfig, inactiveClientExpira
               Just thParams -> processRequest req0 {thParams} -- proceed with new version (XXX: may as well switch the request handler here)
           _ -> liftIO . sendResponse $ H.responseNoBody N.ok200 [] -- shouldn't happen: means server picked handshake protocol it doesn't know about
     xftpServerHandshakeV1 :: X.CertificateChain -> C.APrivateSignKey -> TMap SessionId Handshake -> XFTPTransportRequest -> M (Maybe (THandleParams XFTPVersion 'TServer))
-    xftpServerHandshakeV1 chain serverSignKey sessions XFTPTransportRequest {thParams = thParams@THandleParams {sessionId}, reqBody = HTTP2Body {bodyHead}, sendResponse} = do
+    xftpServerHandshakeV1 chain serverSignKey sessions XFTPTransportRequest {thParams = thParams0@THandleParams {sessionId}, reqBody = HTTP2Body {bodyHead}, sendResponse} = do
       s <- atomically $ TM.lookup sessionId sessions
       r <- runExceptT $ case s of
         Nothing -> processHello
         Just (HandshakeSent pk) -> processClientHandshake pk
-        Just (HandshakeAccepted auth v) -> pure $ Just thParams {thAuth = Just auth, thVersion = v}
+        Just (HandshakeAccepted thParams) -> pure $ Just thParams
       either sendError pure r
       where
         processHello = do
@@ -134,21 +136,24 @@ xftpServer cfg@XFTPServerConfig {xftpPort, transportConfig, inactiveClientExpira
           (k, pk) <- atomically . C.generateKeyPair =<< asks random
           atomically $ TM.insert sessionId (HandshakeSent pk) sessions
           let authPubKey = (chain, C.signX509 serverSignKey $ C.publicToX509 k)
-          let hs = XFTPServerHandshake {xftpVersionRange = supportedFileServerVRange, sessionId, authPubKey}
+          let hs = XFTPServerHandshake {xftpVersionRange = xftpServerVRange, sessionId, authPubKey}
           shs <- encodeXftp hs
           liftIO . sendResponse $ H.responseBuilder N.ok200 [] shs
           pure Nothing
         processClientHandshake pk = do
           unless (B.length bodyHead == xftpBlockSize) $ throwError HANDSHAKE
           body <- liftHS $ C.unPad bodyHead
-          XFTPClientHandshake {xftpVersion, keyHash} <- liftHS $ smpDecode body
+          XFTPClientHandshake {xftpVersion = v, keyHash} <- liftHS $ smpDecode body
           kh <- asks serverIdentity
           unless (keyHash == kh) $ throwError HANDSHAKE
-          unless (xftpVersion `isCompatible` supportedFileServerVRange) $ throwError HANDSHAKE
-          let auth = THAuthServer {serverPrivKey = pk, sessSecret' = Nothing}
-          atomically $ TM.insert sessionId (HandshakeAccepted auth xftpVersion) sessions
-          liftIO . sendResponse $ H.responseNoBody N.ok200 []
-          pure Nothing
+          case compatibleVRange' xftpServerVRange v of
+            Just (Compatible vr) -> do
+              let auth = THAuthServer {serverPrivKey = pk, sessSecret' = Nothing}
+                  thParams = thParams0 {thAuth = Just auth, thVersion = v, thServerVRange = vr}
+              atomically $ TM.insert sessionId (HandshakeAccepted thParams) sessions
+              liftIO . sendResponse $ H.responseNoBody N.ok200 []
+              pure Nothing
+            Nothing -> throwError HANDSHAKE
         sendError :: XFTPErrorType -> M (Maybe (THandleParams XFTPVersion 'TServer))
         sendError err = do
           runExceptT (encodeXftp err) >>= \case
diff --git a/src/Simplex/FileTransfer/Server/Env.hs b/src/Simplex/FileTransfer/Server/Env.hs
index 414bfb4c4..58c1393f3 100644
--- a/src/Simplex/FileTransfer/Server/Env.hs
+++ b/src/Simplex/FileTransfer/Server/Env.hs
@@ -25,6 +25,7 @@ import Simplex.FileTransfer.Protocol (FileCmd, FileInfo (..), XFTPFileId)
 import Simplex.FileTransfer.Server.Stats
 import Simplex.FileTransfer.Server.Store
 import Simplex.FileTransfer.Server.StoreLog
+import Simplex.FileTransfer.Transport (VersionRangeXFTP)
 import qualified Simplex.Messaging.Crypto as C
 import Simplex.Messaging.Protocol (BasicAuth, RcvPublicAuthKey)
 import Simplex.Messaging.Server.Expiration
@@ -61,6 +62,8 @@ data XFTPServerConfig = XFTPServerConfig
     caCertificateFile :: FilePath,
     privateKeyFile :: FilePath,
     certificateFile :: FilePath,
+    -- | XFTP client-server protocol version range
+    xftpServerVRange :: VersionRangeXFTP,
     -- stats config - see SMP server config
     logStatsInterval :: Maybe Int64,
     logStatsStartTime :: Int64,
diff --git a/src/Simplex/FileTransfer/Server/Main.hs b/src/Simplex/FileTransfer/Server/Main.hs
index d53b3f4fa..b909b1617 100644
--- a/src/Simplex/FileTransfer/Server/Main.hs
+++ b/src/Simplex/FileTransfer/Server/Main.hs
@@ -20,6 +20,7 @@ import Simplex.FileTransfer.Chunks
 import Simplex.FileTransfer.Description (FileSize (..))
 import Simplex.FileTransfer.Server (runXFTPServer)
 import Simplex.FileTransfer.Server.Env (XFTPServerConfig (..), defFileExpirationHours, defaultFileExpiration, defaultInactiveClientExpiration, supportedXFTPhandshakes)
+import Simplex.FileTransfer.Transport (supportedFileServerVRange)
 import qualified Simplex.Messaging.Crypto as C
 import Simplex.Messaging.Encoding.String
 import Simplex.Messaging.Protocol (ProtoServerWithAuth (..), pattern XFTPServer)
@@ -174,6 +175,7 @@ xftpServerCLI cfgPath logPath = do
               caCertificateFile = c caCrtFile,
               privateKeyFile = c serverKeyFile,
               certificateFile = c serverCrtFile,
+              xftpServerVRange = supportedFileServerVRange,
               logStatsInterval = logStats $> 86400, -- seconds
               logStatsStartTime = 0, -- seconds from 00:00 UTC
               serverStatsLogFile = combine logPath "file-server-stats.daily.log",
diff --git a/src/Simplex/FileTransfer/Transport.hs b/src/Simplex/FileTransfer/Transport.hs
index 27f1b8b95..244e00972 100644
--- a/src/Simplex/FileTransfer/Transport.hs
+++ b/src/Simplex/FileTransfer/Transport.hs
@@ -37,6 +37,7 @@ import qualified Control.Exception as E
 import Control.Monad
 import Control.Monad.Except
 import Control.Monad.IO.Class
+import Control.Monad.Trans.Except
 import qualified Data.Aeson.TH as J
 import qualified Data.Attoparsec.ByteString.Char8 as A
 import Data.Bifunctor (bimap, first)
@@ -53,7 +54,7 @@ import Simplex.Messaging.Encoding
 import Simplex.Messaging.Encoding.String
 import Simplex.Messaging.Parsers
 import Simplex.Messaging.Protocol (CommandError)
-import Simplex.Messaging.Transport (HandshakeError (..), SessionId, THandle (..), THandleParams (..), TransportError (..), TransportPeer (..))
+import Simplex.Messaging.Transport (SessionId, THandle (..), THandleParams (..), TransportError (..), TransportPeer (..))
 import Simplex.Messaging.Transport.HTTP2.File
 import Simplex.Messaging.Util (bshow)
 import Simplex.Messaging.Version
@@ -95,7 +96,7 @@ supportedFileServerVRange = mkVersionRange initialXFTPVersion currentXFTPVersion
 
 -- XFTP protocol does not use this handshake method
 xftpClientHandshakeStub :: c -> Maybe C.KeyPairX25519 -> C.KeyHash -> VersionRangeXFTP -> ExceptT TransportError IO (THandle XFTPVersion c 'TClient)
-xftpClientHandshakeStub _c _ks _keyHash _xftpVRange = throwError $ TEHandshake VERSION
+xftpClientHandshakeStub _c _ks _keyHash _xftpVRange = throwE TEVersion
 
 data XFTPServerHandshake = XFTPServerHandshake
   { xftpVersionRange :: VersionRangeXFTP,
diff --git a/src/Simplex/Messaging/Agent.hs b/src/Simplex/Messaging/Agent.hs
index f7280facc..d4fb11dd5 100644
--- a/src/Simplex/Messaging/Agent.hs
+++ b/src/Simplex/Messaging/Agent.hs
@@ -849,7 +849,7 @@ joinConnSrv c userId connId hasNewConn enableNtfs cReqUri@CRContactUri {} cInfo
   lift (compatibleContactUri cReqUri) >>= \case
     Just (qInfo, vrsn) -> do
       (connId', cReq) <- newConnSrv c userId connId hasNewConn enableNtfs SCMInvitation Nothing (CR.IKNoPQ pqSup) subMode srv
-      sendInvitation c userId qInfo vrsn cReq cInfo
+      void $ sendInvitation c userId qInfo vrsn cReq cInfo
       pure connId'
     Nothing -> throwError $ AGENT A_VERSION
 
@@ -1358,13 +1358,17 @@ runSmpQueueMsgDelivery c@AgentClient {subQ} ConnData {connId} sq (Worker {doWork
                   | temporaryOrHostError e -> do
                       let msgTimeout = if msgType == AM_HELLO_ then helloTimeout else messageTimeout
                       expireTs <- addUTCTime (-msgTimeout) <$> liftIO getCurrentTime
-                      if internalTs < expireTs then notifyDelMsgs msgId e expireTs else retrySndMsg RIFast
+                      if internalTs < expireTs
+                        then notifyDelMsgs msgId e expireTs
+                        else do
+                          when (serverHostError e) $ notify $ MWARN (unId msgId) e
+                          retrySndMsg RIFast
                   | otherwise -> notifyDel msgId err
               where
                 retrySndMsg riMode = do
                   withStore' c $ \db -> updatePendingMsgRIState db connId msgId riState
                   retrySndOp c $ loop riMode
-            Right () -> do
+            Right proxySrv_ -> do
               case msgType of
                 AM_CONN_INFO -> setConfirmed
                 AM_CONN_INFO_REPLY -> setConfirmed
@@ -1386,7 +1390,7 @@ runSmpQueueMsgDelivery c@AgentClient {subQ} ConnData {connId} sq (Worker {doWork
                       when (status == Active) $ notify $ CON pqEncryption
                     -- this branch should never be reached as receive queue is created before the confirmation,
                     _ -> logError "HELLO sent without receive queue"
-                AM_A_MSG_ -> notify $ SENT mId
+                AM_A_MSG_ -> notify $ SENT mId proxySrv_
                 AM_A_RCVD_ -> pure ()
                 AM_QCONT_ -> pure ()
                 AM_QADD_ -> pure ()
@@ -2089,10 +2093,10 @@ processSMPTransmission c@AgentClient {smpClients, subQ} (tSess@(_, srv, _), _v,
       conn
       cData@ConnData {userId, connId, connAgentVersion, ratchetSyncState = rss} =
         withConnLock c connId "processSMP" $ case cmd of
-          Right (SMP.MSG msg@SMP.RcvMessage {msgId = srvMsgId}) ->
+          Right r@(SMP.MSG msg@SMP.RcvMessage {msgId = srvMsgId}) ->
             void . handleNotifyAck $ do
               isGET <- atomically $ hasGetLock c rq
-              unless isGET checkExpiredResponse
+              unless isGET $ checkExpiredResponse r
               msg' <- decryptSMPMessage rq msg
               ack' <- handleNotifyAck $ case msg' of
                 SMP.ClientRcvMsgBody {msgTs = srvTs, msgFlags, msgBody} -> processClientMsg srvTs msgFlags msgBody
@@ -2262,7 +2266,7 @@ processSMPTransmission c@AgentClient {smpClients, subQ} (tSess@(_, srv, _), _v,
             where
               processEND = \case
                 Just (Right clnt)
-                  | sessId == sessionId (thParams clnt) -> do
+                  | sessId == sessionId (thParams $ connectedClient clnt) -> do
                       removeSubscription c connId
                       notify' END
                       pure "END"
@@ -2270,8 +2274,8 @@ processSMPTransmission c@AgentClient {smpClients, subQ} (tSess@(_, srv, _), _v,
                 _ -> ignored
               ignored = pure "END from disconnected client - ignored"
           Right (SMP.ERR e) -> notify $ ERR $ SMP (B.unpack $ strEncode srv) e
-          Right SMP.OK -> checkExpiredResponse
-          Right _ -> unexpected
+          Right r@SMP.OK -> checkExpiredResponse r
+          Right r -> unexpected r
           Left e -> notify $ ERR $ protocolClientError SMP (B.unpack $ strEncode srv) e
         where
           notify :: forall e m. MonadIO m => AEntityI e => ACommand 'Agent e -> m ()
@@ -2286,16 +2290,16 @@ processSMPTransmission c@AgentClient {smpClients, subQ} (tSess@(_, srv, _), _v,
           enqueueCmd :: InternalCommand -> AM ()
           enqueueCmd = enqueueCommand c "" connId (Just srv) . AInternalCommand
 
-          unexpected :: AM ()
-          unexpected = do
+          unexpected :: BrokerMsg -> AM ()
+          unexpected r = do
             logServer "<--" c srv rId $ "unexpected: " <> bshow cmd
             -- TODO add extended information about transmission type once UNEXPECTED has string
-            notify . ERR $ BROKER (B.unpack $ strEncode srv) UNEXPECTED
+            notify . ERR $ BROKER (B.unpack $ strEncode srv) $ UNEXPECTED (take 32 $ show r)
 
-          checkExpiredResponse :: AM ()
-          checkExpiredResponse = case tType of
+          checkExpiredResponse :: BrokerMsg -> AM ()
+          checkExpiredResponse r = case tType of
             TTEvent -> pure ()
-            TTUncorrelatedResponse -> unexpected
+            TTUncorrelatedResponse -> unexpected r
             TTExpiredResponse (SMP.Cmd _ cmd') -> case cmd' of
               SMP.SUB -> do
                 added <-
@@ -2643,7 +2647,7 @@ confirmQueueAsync c cData sq srv connInfo e2eEncryption_ subMode = do
 confirmQueue :: AgentClient -> ConnData -> SndQueue -> SMPServerWithAuth -> ConnInfo -> Maybe (CR.SndE2ERatchetParams 'C.X448) -> SubscriptionMode -> AM ()
 confirmQueue c cData@ConnData {connId, connAgentVersion, pqSupport} sq srv connInfo e2eEncryption_ subMode = do
   msg <- mkConfirmation =<< mkAgentConfirmation c cData sq srv connInfo subMode
-  sendConfirmation c sq msg
+  void $ sendConfirmation c sq msg
   withStore' c $ \db -> setSndQueueStatus db sq Confirmed
   where
     mkConfirmation :: AgentMessage -> AM MsgBody
diff --git a/src/Simplex/Messaging/Agent/Client.hs b/src/Simplex/Messaging/Agent/Client.hs
index 0e4a5b49e..13adb9fdc 100644
--- a/src/Simplex/Messaging/Agent/Client.hs
+++ b/src/Simplex/Messaging/Agent/Client.hs
@@ -47,6 +47,7 @@ module Simplex.Messaging.Agent.Client
     sendInvitation,
     temporaryAgentError,
     temporaryOrHostError,
+    serverHostError,
     secureQueue,
     enableQueueNotifications,
     enableQueuesNtfs,
@@ -136,6 +137,8 @@ module Simplex.Messaging.Agent.Client
     SMPTransportSession,
     NtfTransportSession,
     XFTPTransportSession,
+    ProxiedRelay (..),
+    SMPConnectedClient (..),
   )
 where
 
@@ -149,6 +152,7 @@ import Control.Monad
 import Control.Monad.Except
 import Control.Monad.IO.Unlift
 import Control.Monad.Reader
+import Control.Monad.Trans.Except
 import Crypto.Random (ChaChaDRG)
 import qualified Data.Aeson as J
 import qualified Data.Aeson.TH as J
@@ -234,8 +238,8 @@ import qualified Simplex.Messaging.Protocol as SMP
 import Simplex.Messaging.Session
 import Simplex.Messaging.TMap (TMap)
 import qualified Simplex.Messaging.TMap as TM
-import Simplex.Messaging.Transport (SMPVersion, SessionId, THandleParams (sessionId))
-import Simplex.Messaging.Transport.Client (TransportHost)
+import Simplex.Messaging.Transport (SMPVersion, SessionId, THandleParams (sessionId), TransportError (..))
+import Simplex.Messaging.Transport.Client (TransportHost (..))
 import Simplex.Messaging.Util
 import Simplex.Messaging.Version
 import System.Mem.Weak (Weak)
@@ -268,6 +272,10 @@ data AgentClient = AgentClient
     msgQ :: TBQueue (ServerTransmission SMPVersion ErrorType BrokerMsg),
     smpServers :: TMap UserId (NonEmpty SMPServerWithAuth),
     smpClients :: TMap SMPTransportSession SMPClientVar,
+    -- smpProxiedRelays:
+    -- SMPTransportSession defines connection from proxy to relay,
+    -- SMPServerWithAuth defines client connected to SMP proxy (with the same userId and entityId in TransportSession)
+    smpProxiedRelays :: TMap SMPTransportSession SMPServerWithAuth,
     ntfServers :: TVar [NtfServer],
     ntfClients :: TMap NtfTransportSession NtfClientVar,
     xftpServers :: TMap UserId (NonEmpty XFTPServerWithAuth),
@@ -303,6 +311,13 @@ data AgentClient = AgentClient
     agentEnv :: Env
   }
 
+data SMPConnectedClient = SMPConnectedClient
+  { connectedClient :: SMPClient,
+    proxiedRelays :: TMap SMPServer ProxiedRelayVar
+  }
+
+type ProxiedRelayVar = SessionVar (Either AgentErrorType ProxiedRelay)
+
 getAgentWorker :: (Ord k, Show k) => String -> Bool -> AgentClient -> k -> TMap k Worker -> (Worker -> AM ()) -> AM' Worker
 getAgentWorker = getAgentWorker' id pure
 {-# INLINE getAgentWorker #-}
@@ -434,6 +449,7 @@ newAgentClient clientId InitialAgentServers {smp, ntf, xftp, netCfg} agentEnv =
   msgQ <- newTBQueue qSize
   smpServers <- newTVar smp
   smpClients <- TM.empty
+  smpProxiedRelays <- TM.empty
   ntfServers <- newTVar ntf
   ntfClients <- TM.empty
   xftpServers <- newTVar xftp
@@ -470,6 +486,7 @@ newAgentClient clientId InitialAgentServers {smp, ntf, xftp, netCfg} agentEnv =
         msgQ,
         smpServers,
         smpClients,
+        smpProxiedRelays,
         ntfServers,
         ntfClients,
         xftpServers,
@@ -519,15 +536,19 @@ agentDRG AgentClient {agentEnv = Env {random}} = random
 class (Encoding err, Show err) => ProtocolServerClient v err msg | msg -> v, msg -> err where
   type Client msg = c | c -> msg
   getProtocolServerClient :: AgentClient -> TransportSession msg -> AM (Client msg)
+  type ProtoClient msg = c | c -> msg
+  protocolClient :: Client msg -> ProtoClient msg
   clientProtocolError :: HostName -> err -> AgentErrorType
-  closeProtocolServerClient :: Client msg -> IO ()
-  clientServer :: Client msg -> String
-  clientTransportHost :: Client msg -> TransportHost
-  clientSessionTs :: Client msg -> UTCTime
+  closeProtocolServerClient :: ProtoClient msg -> IO ()
+  clientServer :: ProtoClient msg -> String
+  clientTransportHost :: ProtoClient msg -> TransportHost
+  clientSessionTs :: ProtoClient msg -> UTCTime
 
 instance ProtocolServerClient SMPVersion ErrorType BrokerMsg where
-  type Client BrokerMsg = ProtocolClient SMPVersion ErrorType BrokerMsg
+  type Client BrokerMsg = SMPConnectedClient
   getProtocolServerClient = getSMPServerClient
+  type ProtoClient BrokerMsg = ProtocolClient SMPVersion ErrorType BrokerMsg
+  protocolClient = connectedClient
   clientProtocolError = SMP
   closeProtocolServerClient = closeProtocolClient
   clientServer = protocolClientServer
@@ -537,6 +558,8 @@ instance ProtocolServerClient SMPVersion ErrorType BrokerMsg where
 instance ProtocolServerClient NTFVersion ErrorType NtfResponse where
   type Client NtfResponse = ProtocolClient NTFVersion ErrorType NtfResponse
   getProtocolServerClient = getNtfServerClient
+  type ProtoClient NtfResponse = ProtocolClient NTFVersion ErrorType NtfResponse
+  protocolClient = id
   clientProtocolError = NTF
   closeProtocolServerClient = closeProtocolClient
   clientServer = protocolClientServer
@@ -546,61 +569,121 @@ instance ProtocolServerClient NTFVersion ErrorType NtfResponse where
 instance ProtocolServerClient XFTPVersion XFTPErrorType FileResponse where
   type Client FileResponse = XFTPClient
   getProtocolServerClient = getXFTPServerClient
+  type ProtoClient FileResponse = XFTPClient
+  protocolClient = id
   clientProtocolError = XFTP
   closeProtocolServerClient = X.closeXFTPClient
   clientServer = X.xftpClientServer
   clientTransportHost = X.xftpTransportHost
   clientSessionTs = X.xftpSessionTs
 
-getSMPServerClient :: AgentClient -> SMPTransportSession -> AM SMPClient
-getSMPServerClient c@AgentClient {active, smpClients, msgQ, workerSeq} tSess@(userId, srv, _) = do
+getSMPServerClient :: AgentClient -> SMPTransportSession -> AM SMPConnectedClient
+getSMPServerClient c@AgentClient {active, smpClients, workerSeq} tSess = do
   unlessM (readTVarIO active) . throwError $ INACTIVE
   atomically (getSessVar workerSeq tSess smpClients)
     >>= either newClient (waitForProtocolClient c tSess)
   where
-    -- we resubscribe only on newClient error, but not on waitForProtocolClient error,
-    -- as the large number of delivery workers waiting for the client TMVar
-    -- make it expensive to check for pending subscriptions.
-    newClient v =
-      newProtocolClient c tSess smpClients connectClient v
-        `catchAgentError` \e -> lift (resubscribeSMPSession c tSess) >> throwError e
-    connectClient :: SMPClientVar -> AM SMPClient
-    connectClient v = do
+    newClient v = do
+      prs <- atomically TM.empty
+      smpConnectClient c tSess prs v
+
+getSMPProxyClient :: AgentClient -> SMPTransportSession -> AM (SMPConnectedClient, Either AgentErrorType ProxiedRelay)
+getSMPProxyClient c@AgentClient {active, smpClients, smpProxiedRelays, workerSeq} destSess@(userId, destSrv, qId) = do
+  unlessM (readTVarIO active) . throwError $ INACTIVE
+  proxySrv <- getNextServer c userId [destSrv]
+  atomically (getClientVar proxySrv) >>= \(tSess, auth, v) ->
+    either (newProxyClient tSess auth) (waitForProxyClient tSess auth) v
+  where
+    getClientVar :: SMPServerWithAuth -> STM (SMPTransportSession, Maybe SMP.BasicAuth, Either SMPClientVar SMPClientVar)
+    getClientVar proxySrv = do
+      ProtoServerWithAuth srv auth <- TM.lookup destSess smpProxiedRelays >>= maybe (TM.insert destSess proxySrv smpProxiedRelays $> proxySrv) pure
+      let tSess = (userId, srv, qId)
+      (tSess,auth,) <$> getSessVar workerSeq tSess smpClients
+    newProxyClient :: SMPTransportSession -> Maybe SMP.BasicAuth -> SMPClientVar -> AM (SMPConnectedClient, Either AgentErrorType ProxiedRelay)
+    newProxyClient tSess auth v = do
+      (prs, rv) <- atomically $ do
+        prs <- TM.empty
+        -- we do not need to check if it is a new proxied relay session,
+        -- as the client is just created and there are no sessions yet
+        (prs,) . either id id <$> getSessVar workerSeq destSrv prs
+      clnt <- smpConnectClient c tSess prs v
+      (clnt,) <$> newProxiedRelay clnt auth rv
+    waitForProxyClient :: SMPTransportSession -> Maybe SMP.BasicAuth -> SMPClientVar -> AM (SMPConnectedClient, Either AgentErrorType ProxiedRelay)
+    waitForProxyClient tSess auth v = do
+      clnt@(SMPConnectedClient _ prs) <- waitForProtocolClient c tSess v
+      sess <-
+        atomically (getSessVar workerSeq destSrv prs)
+          >>= either (newProxiedRelay clnt auth) (waitForProxiedRelay tSess)
+      pure (clnt, sess)
+    newProxiedRelay :: SMPConnectedClient -> Maybe SMP.BasicAuth -> ProxiedRelayVar -> AM (Either AgentErrorType ProxiedRelay)
+    newProxiedRelay clnt@(SMPConnectedClient smp prs) proxyAuth rv =
+      tryAgentError (liftClient SMP (clientServer smp) $ connectSMPProxiedRelay smp destSrv proxyAuth) >>= \case
+        Right sess -> do
+          atomically $ putTMVar (sessionVar rv) (Right sess)
+          liftIO $ incClientStat c userId clnt "PROXY" "OK"
+          pure $ Right sess
+        Left e -> do
+          liftIO $ incClientStat c userId clnt "PROXY" $ strEncode e
+          atomically $ do
+            unless (serverHostError e) $ do
+              removeSessVar rv destSrv prs
+              TM.delete destSess smpProxiedRelays
+            putTMVar (sessionVar rv) (Left e)
+            pure $ Left e
+    waitForProxiedRelay :: SMPTransportSession -> ProxiedRelayVar -> AM (Either AgentErrorType ProxiedRelay)
+    waitForProxiedRelay (_, srv, _) rv = do
+      NetworkConfig {tcpConnectTimeout} <- atomically $ getNetworkConfig c
+      sess_ <- liftIO $ tcpConnectTimeout `timeout` atomically (readTMVar $ sessionVar rv)
+      pure $ case sess_ of
+        Just (Right sess) -> Right sess
+        Just (Left e) -> Left e
+        Nothing -> Left $ BROKER (B.unpack $ strEncode srv) TIMEOUT
+
+smpConnectClient :: AgentClient -> SMPTransportSession -> TMap SMPServer ProxiedRelayVar -> SMPClientVar -> AM SMPConnectedClient
+smpConnectClient c@AgentClient {smpClients, msgQ} tSess@(_, srv, _) prs v =
+  newProtocolClient c tSess smpClients connectClient v
+    `catchAgentError` \e -> lift (resubscribeSMPSession c tSess) >> throwError e
+  where
+    connectClient :: SMPClientVar -> AM SMPConnectedClient
+    connectClient v' = do
       cfg <- lift $ getClientConfig c smpCfg
       g <- asks random
       env <- ask
-      liftError' (protocolClientError SMP $ B.unpack $ strEncode srv) $
-        getProtocolClient g tSess cfg (Just msgQ) $
-          clientDisconnected env v
+      liftError (protocolClientError SMP $ B.unpack $ strEncode srv) $ do
+        smp <- ExceptT $ getProtocolClient g tSess cfg (Just msgQ) $ smpClientDisconnected c tSess env v' prs
+        pure SMPConnectedClient {connectedClient = smp, proxiedRelays = prs}
 
-    clientDisconnected :: Env -> SMPClientVar -> SMPClient -> IO ()
-    clientDisconnected env v client = do
-      removeClientAndSubs >>= serverDown
-      logInfo . decodeUtf8 $ "Agent disconnected from " <> showServer srv
+smpClientDisconnected :: AgentClient -> SMPTransportSession -> Env -> SMPClientVar -> TMap SMPServer ProxiedRelayVar -> SMPClient -> IO ()
+smpClientDisconnected c@AgentClient {active, smpClients, smpProxiedRelays} tSess@(userId, srv, qId) env v prs client = do
+  removeClientAndSubs >>= serverDown
+  logInfo . decodeUtf8 $ "Agent disconnected from " <> showServer srv
+  where
+    -- we make active subscriptions pending only if the client for tSess was current (in the map) and active,
+    -- because we can have a race condition when a new current client could have already
+    -- made subscriptions active, and the old client would be processing diconnection later.
+    removeClientAndSubs :: IO ([RcvQueue], [ConnId])
+    removeClientAndSubs = atomically $ ifM currentActiveClient removeSubs $ pure ([], [])
       where
-        -- we make active subscriptions pending only if the client for tSess was current (in the map) and active,
-        -- because we can have a race condition when a new current client could have already
-        -- made subscriptions active, and the old client would be processing diconnection later.
-        removeClientAndSubs :: IO ([RcvQueue], [ConnId])
-        removeClientAndSubs = atomically $ ifM currentActiveClient removeSubs $ pure ([], [])
-          where
-            currentActiveClient = (&&) <$> removeSessVar' v tSess smpClients <*> readTVar active
-            removeSubs = do
-              (qs, cs) <- RQ.getDelSessQueues tSess $ activeSubs c
-              RQ.batchAddQueues (pendingSubs c) qs
-              pure (qs, cs)
+        currentActiveClient = (&&) <$> removeSessVar' v tSess smpClients <*> readTVar active
+        removeSubs = do
+          (qs, cs) <- RQ.getDelSessQueues tSess $ activeSubs c
+          RQ.batchAddQueues (pendingSubs c) qs
+          -- this removes proxied relays that this client created sessions to
+          destSrvs <- M.keys <$> readTVar prs
+          forM_ destSrvs $ \destSrv -> TM.delete (userId, destSrv, qId) smpProxiedRelays
+          pure (qs, cs)
 
-        serverDown :: ([RcvQueue], [ConnId]) -> IO ()
-        serverDown (qs, conns) = whenM (readTVarIO active) $ do
-          incClientStat c userId client "DISCONNECT" ""
-          notifySub "" $ hostEvent DISCONNECT client
-          unless (null conns) $ notifySub "" $ DOWN srv conns
-          unless (null qs) $ do
-            atomically $ mapM_ (releaseGetLock c) qs
-            runReaderT (resubscribeSMPSession c tSess) env
+    serverDown :: ([RcvQueue], [ConnId]) -> IO ()
+    serverDown (qs, conns) = whenM (readTVarIO active) $ do
+      incClientStat' c userId client "DISCONNECT" ""
+      notifySub "" $ hostEvent' DISCONNECT client
+      unless (null conns) $ notifySub "" $ DOWN srv conns
+      unless (null qs) $ do
+        atomically $ mapM_ (releaseGetLock c) qs
+        runReaderT (resubscribeSMPSession c tSess) env
 
-        notifySub :: forall e. AEntityI e => ConnId -> ACommand 'Agent e -> IO ()
-        notifySub connId cmd = atomically $ writeTBQueue (subQ c) ("", connId, APC (sAEntity @e) cmd)
+    notifySub :: forall e. AEntityI e => ConnId -> ACommand 'Agent e -> IO ()
+    notifySub connId cmd = atomically $ writeTBQueue (subQ c) ("", connId, APC (sAEntity @e) cmd)
 
 resubscribeSMPSession :: AgentClient -> SMPTransportSession -> AM' ()
 resubscribeSMPSession c@AgentClient {smpSubWorkers, workerSeq} tSess =
@@ -750,7 +833,11 @@ newProtocolClient c tSess@(userId, srv, entityId_) clients connectClient v =
       throwError e -- signal error to caller
 
 hostEvent :: forall v err msg. (ProtocolTypeI (ProtoType msg), ProtocolServerClient v err msg) => (AProtocolType -> TransportHost -> ACommand 'Agent 'AENone) -> Client msg -> ACommand 'Agent 'AENone
-hostEvent event = event (AProtocolType $ protocolTypeI @(ProtoType msg)) . clientTransportHost
+hostEvent event = hostEvent' event . protocolClient
+{-# INLINE hostEvent #-}
+
+hostEvent' :: forall v err msg. (ProtocolTypeI (ProtoType msg), ProtocolServerClient v err msg) => (AProtocolType -> TransportHost -> ACommand 'Agent 'AENone) -> ProtoClient msg -> ACommand 'Agent 'AENone
+hostEvent' event = event (AProtocolType $ protocolTypeI @(ProtoType msg)) . clientTransportHost
 
 getClientConfig :: AgentClient -> (AgentConfig -> ProtocolClientConfig v) -> AM' (ProtocolClientConfig v)
 getClientConfig c cfgSel = do
@@ -805,6 +892,7 @@ closeAgentClient c = do
   closeProtocolServerClients c smpClients
   closeProtocolServerClients c ntfClients
   closeProtocolServerClients c xftpClients
+  atomically $ writeTVar (smpProxiedRelays c) M.empty
   atomically (swapTVar (smpSubWorkers c) M.empty) >>= mapM_ cancelReconnect
   clearWorkers smpDeliveryWorkers >>= mapM_ (cancelWorker . fst)
   clearWorkers asyncCmdWorkers >>= mapM_ cancelWorker
@@ -857,7 +945,7 @@ closeClient_ c v = do
   NetworkConfig {tcpConnectTimeout} <- atomically $ getNetworkConfig c
   E.handle (\BlockedIndefinitelyOnSTM -> pure ()) $
     tcpConnectTimeout `timeout` atomically (readTMVar $ sessionVar v) >>= \case
-      Just (Right client) -> closeProtocolServerClient client `catchAll_` pure ()
+      Just (Right client) -> closeProtocolServerClient (protocolClient client) `catchAll_` pure ()
       _ -> pure ()
 
 closeXFTPServerClient :: AgentClient -> UserId -> XFTPServer -> FileDigest -> IO ()
@@ -910,6 +998,25 @@ withClient_ c tSess@(userId, srv, _) statCmd action = do
       stat cl $ strEncode e
       throwError e
 
+withProxySession :: AgentClient -> SMPTransportSession -> SMP.SenderId -> ByteString -> ((SMPConnectedClient, ProxiedRelay) -> AM a) -> AM a
+withProxySession c destSess@(userId, destSrv, _) entId cmdStr action = do
+  (cl, sess_) <- getSMPProxyClient c destSess
+  logServer ("--> " <> proxySrv cl <> " >") c destSrv entId cmdStr
+  case sess_ of
+    Right sess -> do
+      r <- (action (cl, sess) <* stat cl "OK") `catchAgentError` logServerError cl
+      logServer ("<-- " <> proxySrv cl <> " <") c destSrv entId "OK"
+      pure r
+    Left e -> logServerError cl e
+  where
+    stat cl = liftIO . incClientStat c userId cl cmdStr
+    proxySrv = showServer . protocolClientServer' . protocolClient
+    logServerError :: SMPConnectedClient -> AgentErrorType -> AM a
+    logServerError cl e = do
+      logServer ("<-- " <> proxySrv cl <> " <") c destSrv "" $ strEncode e
+      stat cl $ strEncode e
+      throwError e
+
 withLogClient_ :: ProtocolServerClient v err msg => AgentClient -> TransportSession msg -> EntityId -> ByteString -> (Client msg -> AM a) -> AM a
 withLogClient_ c tSess@(_, srv, _) entId cmdStr action = do
   logServer "-->" c srv entId cmdStr
@@ -918,22 +1025,64 @@ withLogClient_ c tSess@(_, srv, _) entId cmdStr action = do
   return res
 
 withClient :: forall v err msg a. ProtocolServerClient v err msg => AgentClient -> TransportSession msg -> ByteString -> (Client msg -> ExceptT (ProtocolClientError err) IO a) -> AM a
-withClient c tSess statKey action = withClient_ c tSess statKey $ \client -> liftClient (clientProtocolError @v @err @msg) (clientServer client) $ action client
+withClient c tSess statKey action = withClient_ c tSess statKey $ \client -> liftClient (clientProtocolError @v @err @msg) (clientServer $ protocolClient client) $ action client
 {-# INLINE withClient #-}
 
 withLogClient :: forall v err msg a. ProtocolServerClient v err msg => AgentClient -> TransportSession msg -> EntityId -> ByteString -> (Client msg -> ExceptT (ProtocolClientError err) IO a) -> AM a
-withLogClient c tSess entId cmdStr action = withLogClient_ c tSess entId cmdStr $ \client -> liftClient (clientProtocolError @v @err @msg) (clientServer client) $ action client
+withLogClient c tSess entId cmdStr action = withLogClient_ c tSess entId cmdStr $ \client -> liftClient (clientProtocolError @v @err @msg) (clientServer $ protocolClient client) $ action client
 {-# INLINE withLogClient #-}
 
 withSMPClient :: SMPQueueRec q => AgentClient -> q -> ByteString -> (SMPClient -> ExceptT SMPClientError IO a) -> AM a
 withSMPClient c q cmdStr action = do
   tSess <- liftIO $ mkSMPTransportSession c q
-  withLogClient c tSess (queueId q) cmdStr action
+  withLogClient c tSess (queueId q) cmdStr $ action . connectedClient
 
-withSMPClient_ :: SMPQueueRec q => AgentClient -> q -> ByteString -> (SMPClient -> AM a) -> AM a
-withSMPClient_ c q cmdStr action = do
-  tSess <- liftIO $ mkSMPTransportSession c q
-  withLogClient_ c tSess (queueId q) cmdStr action
+sendOrProxySMPMessage :: AgentClient -> UserId -> SMPServer -> ByteString -> Maybe SMP.SndPrivateAuthKey -> SMP.SenderId -> MsgFlags -> SMP.MsgBody -> AM (Maybe SMPServer)
+sendOrProxySMPMessage c userId destSrv cmdStr spKey_ senderId msgFlags msg = do
+  sess <- liftIO $ mkTransportSession c userId destSrv senderId
+  ifM (atomically shouldUseProxy) (sendViaProxy sess) (sendDirectly sess $> Nothing)
+  where
+    shouldUseProxy = do
+      cfg <- getNetworkConfig c
+      case smpProxyMode cfg of
+        SPMAlways -> pure True
+        SPMUnknown -> unknownServer
+        SPMUnprotected
+          | ipAddressProtected cfg destSrv -> pure False
+          | otherwise -> unknownServer
+        SPMNever -> pure False
+    directAllowed = do
+      cfg <- getNetworkConfig c
+      pure $ case smpProxyFallback cfg of
+        SPFAllow -> True
+        SPFAllowProtected -> ipAddressProtected cfg destSrv
+        SPFProhibit -> False
+    unknownServer = maybe True (all ((destSrv /=) . protoServer)) <$> TM.lookup userId (userServers c)
+    sendViaProxy destSess = do
+      r <- tryAgentError . withProxySession c destSess senderId ("PFWD " <> cmdStr) $ \(SMPConnectedClient smp _, proxySess) -> do
+        liftClient SMP (clientServer smp) (proxySMPMessage smp proxySess spKey_ senderId msgFlags msg) >>= \case
+          Right () -> pure . Just $ protocolClientServer' smp
+          Left proxyErr ->
+            throwE
+              PROXY
+                { proxyServer = protocolClientServer smp,
+                  relayServer = B.unpack $ strEncode destSrv,
+                  proxyErr
+                }
+      case r of
+        Right r' -> pure r'
+        Left e
+          | serverHostError e -> ifM (atomically directAllowed) (sendDirectly destSess $> Nothing) (throwE e)
+          | otherwise -> throwE e
+    sendDirectly tSess =
+      withLogClient_ c tSess senderId ("SEND " <> cmdStr) $ \(SMPConnectedClient smp _) ->
+        liftClient SMP (clientServer smp) $ sendSMPMessage smp spKey_ senderId msgFlags msg
+
+ipAddressProtected :: NetworkConfig -> ProtocolServer p -> Bool
+ipAddressProtected NetworkConfig {socksProxy, hostMode} (ProtocolServer _ hosts _ _) = do
+  isJust socksProxy || (hostMode == HMOnion && any isOnionHost hosts)
+  where
+    isOnionHost = \case THOnionHost _ -> True; _ -> False
 
 withNtfClient :: AgentClient -> NtfServer -> EntityId -> ByteString -> (NtfClient -> ExceptT NtfClientError IO a) -> AM a
 withNtfClient c srv = withLogClient c (0, srv, Nothing)
@@ -957,7 +1106,7 @@ protocolClientError :: (Show err, Encoding err) => (HostName -> err -> AgentErro
 protocolClientError protocolError_ host = \case
   PCEProtocolError e -> protocolError_ host e
   PCEResponseError e -> BROKER host $ RESPONSE $ B.unpack $ smpEncode e
-  PCEUnexpectedResponse _ -> BROKER host UNEXPECTED
+  PCEUnexpectedResponse r -> BROKER host $ UNEXPECTED $ take 32 $ show r
   PCEResponseTimeout -> BROKER host TIMEOUT
   PCENetworkError -> BROKER host NETWORK
   PCEIncompatibleHost -> BROKER host HOST
@@ -1004,7 +1153,6 @@ runSMPServerTest c userId (ProtoServerWithAuth srv auth) = do
           liftError (testErr TSSecureQueue) $ secureSMPQueue smp rpKey rcvId sKey
           liftError (testErr TSDeleteQueue) $ deleteSMPQueue smp rpKey rcvId
         ok <- tcpTimeout (networkConfig cfg) `timeout` closeProtocolClient smp
-        incClientStat c userId smp "SMP_TEST" "OK"
         pure $ either Just (const Nothing) r <|> maybe (Just (ProtocolTestFailure TSDisconnect $ BROKER addr TIMEOUT)) (const Nothing) ok
       Left e -> pure (Just $ testErr TSConnect e)
   where
@@ -1119,7 +1267,7 @@ newRcvQueue c userId connId (ProtoServerWithAuth srv auth) vRange subMode = do
   logServer "-->" c srv "" "NEW"
   tSess <- liftIO $ mkTransportSession c userId srv connId
   (sessId, QIK {rcvId, sndId, rcvPublicDhKey}) <-
-    withClient c tSess "NEW" $ \smp ->
+    withClient c tSess "NEW" $ \(SMPConnectedClient smp _) ->
       (sessionId $ thParams smp,) <$> createSMPQueue smp rKeys dhKey auth subMode
   liftIO . logServer "<--" c srv "" $ B.unwords ["IDS", logSecret rcvId, logSecret sndId]
   let rq =
@@ -1157,18 +1305,33 @@ processSubResult c rq@RcvQueue {connId} = \case
 
 temporaryAgentError :: AgentErrorType -> Bool
 temporaryAgentError = \case
-  BROKER _ NETWORK -> True
-  BROKER _ TIMEOUT -> True
+  BROKER _ e -> tempBrokerError e
+  SMP _ (SMP.PROXY (SMP.BROKER e)) -> tempBrokerError e
+  PROXY _ _ (ProxyProtocolError (SMP.PROXY (SMP.BROKER e))) -> tempBrokerError e
   INACTIVE -> True
   _ -> False
-{-# INLINE temporaryAgentError #-}
+  where
+    tempBrokerError = \case
+      NETWORK -> True
+      TIMEOUT -> True
+      _ -> False
 
 temporaryOrHostError :: AgentErrorType -> Bool
-temporaryOrHostError = \case
-  BROKER _ HOST -> True
-  e -> temporaryAgentError e
+temporaryOrHostError e = temporaryAgentError e || serverHostError e
 {-# INLINE temporaryOrHostError #-}
 
+serverHostError :: AgentErrorType -> Bool
+serverHostError = \case
+  BROKER _ e -> brokerHostError e
+  SMP _ (SMP.PROXY (SMP.BROKER e)) -> brokerHostError e
+  PROXY _ _ (ProxyProtocolError (SMP.PROXY (SMP.BROKER e))) -> brokerHostError e
+  _ -> False
+  where
+    brokerHostError = \case
+      HOST -> True
+      SMP.TRANSPORT TEVersion -> True
+      _ -> False
+
 -- | Subscribe to queues. The list of results can have a different order.
 subscribeQueues :: AgentClient -> [RcvQueue] -> AM' ([(RcvQueue, Either AgentErrorType ())], Maybe SessionId)
 subscribeQueues c qs = do
@@ -1211,7 +1374,7 @@ activeClientSession :: AgentClient -> SMPTransportSession -> SessionId -> STM Bo
 activeClientSession c tSess sessId = sameSess <$> tryReadSessVar tSess (smpClients c)
   where
     sameSess = \case
-      Just (Right smp) -> sessId == sessionId (thParams smp)
+      Just (Right (SMPConnectedClient smp _)) -> sessId == sessionId (thParams smp)
       _ -> False
 
 type BatchResponses e r = NonEmpty (RcvQueue, Either e r)
@@ -1233,7 +1396,7 @@ sendTSessionBatches statCmd statBatchSize toRQ action c qs =
     sendClientBatch (tSess@(userId, srv, _), qs') =
       tryAgentError' (getSMPServerClient c tSess) >>= \case
         Left e -> pure $ L.map ((,Left e) . toRQ) qs'
-        Right smp -> liftIO $ do
+        Right (SMPConnectedClient smp _) -> liftIO $ do
           logServer "-->" c srv (bshow (length qs') <> " queues") statCmd
           rs <- L.map agentError <$> action smp qs'
           statBatch
@@ -1302,20 +1465,17 @@ logSecret :: ByteString -> ByteString
 logSecret bs = encode $ B.take 3 bs
 {-# INLINE logSecret #-}
 
-sendConfirmation :: AgentClient -> SndQueue -> ByteString -> AM ()
-sendConfirmation c sq@SndQueue {sndId, sndPublicKey = Just sndPublicKey, e2ePubKey = e2ePubKey@Just {}} agentConfirmation =
-  withSMPClient_ c sq "SEND <CONF>" $ \smp -> do
-    let clientMsg = SMP.ClientMessage (SMP.PHConfirmation sndPublicKey) agentConfirmation
-    msg <- agentCbEncrypt sq e2ePubKey $ smpEncode clientMsg
-    liftClient SMP (clientServer smp) $ sendSMPMessage smp Nothing sndId (SMP.MsgFlags {notification = True}) msg
+sendConfirmation :: AgentClient -> SndQueue -> ByteString -> AM (Maybe SMPServer)
+sendConfirmation c sq@SndQueue {userId, server, sndId, sndPublicKey = Just sndPublicKey, e2ePubKey = e2ePubKey@Just {}} agentConfirmation = do
+  let clientMsg = SMP.ClientMessage (SMP.PHConfirmation sndPublicKey) agentConfirmation
+  msg <- agentCbEncrypt sq e2ePubKey $ smpEncode clientMsg
+  sendOrProxySMPMessage c userId server "<CONF>" Nothing sndId (MsgFlags {notification = True}) msg
 sendConfirmation _ _ _ = throwError $ INTERNAL "sendConfirmation called without snd_queue public key(s) in the database"
 
-sendInvitation :: AgentClient -> UserId -> Compatible SMPQueueInfo -> Compatible VersionSMPA -> ConnectionRequestUri 'CMInvitation -> ConnInfo -> AM ()
+sendInvitation :: AgentClient -> UserId -> Compatible SMPQueueInfo -> Compatible VersionSMPA -> ConnectionRequestUri 'CMInvitation -> ConnInfo -> AM (Maybe SMPServer)
 sendInvitation c userId (Compatible (SMPQueueInfo v SMPQueueAddress {smpServer, senderId, dhPublicKey})) (Compatible agentVersion) connReq connInfo = do
-  tSess <- liftIO $ mkTransportSession c userId smpServer senderId
-  withLogClient_ c tSess senderId "SEND <INV>" $ \smp -> do
-    msg <- mkInvitation
-    liftClient SMP (clientServer smp) $ sendSMPMessage smp Nothing senderId MsgFlags {notification = True} msg
+  msg <- mkInvitation
+  sendOrProxySMPMessage c userId smpServer "<INV>" Nothing senderId (MsgFlags {notification = True}) msg
   where
     mkInvitation :: AM ByteString
     -- this is only encrypted with per-queue E2E, not with double ratchet
@@ -1399,12 +1559,11 @@ deleteQueue c rq@RcvQueue {rcvId, rcvPrivateKey} = do
 deleteQueues :: AgentClient -> [RcvQueue] -> AM' [(RcvQueue, Either AgentErrorType ())]
 deleteQueues = sendTSessionBatches "DEL" 90 id $ sendBatch deleteSMPQueues
 
-sendAgentMessage :: AgentClient -> SndQueue -> MsgFlags -> ByteString -> AM ()
-sendAgentMessage c sq@SndQueue {sndId, sndPrivateKey} msgFlags agentMsg =
-  withSMPClient_ c sq "SEND <MSG>" $ \smp -> do
-    let clientMsg = SMP.ClientMessage SMP.PHEmpty agentMsg
-    msg <- agentCbEncrypt sq Nothing $ smpEncode clientMsg
-    liftClient SMP (clientServer smp) $ sendSMPMessage smp (Just sndPrivateKey) sndId msgFlags msg
+sendAgentMessage :: AgentClient -> SndQueue -> MsgFlags -> ByteString -> AM (Maybe SMPServer)
+sendAgentMessage c sq@SndQueue {userId, server, sndId, sndPrivateKey} msgFlags agentMsg = do
+  let clientMsg = SMP.ClientMessage SMP.PHEmpty agentMsg
+  msg <- agentCbEncrypt sq Nothing $ smpEncode clientMsg
+  sendOrProxySMPMessage c userId server "<MSG>" (Just sndPrivateKey) sndId msgFlags msg
 
 agentNtfRegisterToken :: AgentClient -> NtfToken -> NtfPublicAuthKey -> C.PublicKeyX25519 -> AM (NtfTokenId, C.PublicKeyX25519)
 agentNtfRegisterToken c NtfToken {deviceToken, ntfServer, ntfPrivKey} ntfPubKey pubDhKey =
@@ -1672,9 +1831,13 @@ incStat AgentClient {agentStats} n k = do
     _ -> newTVar n >>= \v -> TM.insert k v agentStats
 
 incClientStat :: ProtocolServerClient v err msg => AgentClient -> UserId -> Client msg -> ByteString -> ByteString -> IO ()
-incClientStat c userId pc = incClientStatN c userId pc 1
+incClientStat c userId = incClientStat' c userId . protocolClient
 {-# INLINE incClientStat #-}
 
+incClientStat' :: ProtocolServerClient v err msg => AgentClient -> UserId -> ProtoClient msg -> ByteString -> ByteString -> IO ()
+incClientStat' c userId pc = incClientStatN c userId pc 1
+{-# INLINE incClientStat' #-}
+
 incServerStat :: AgentClient -> UserId -> ProtocolServer p -> ByteString -> ByteString -> IO ()
 incServerStat c userId ProtocolServer {host} cmd res = do
   threadDelay 100000
@@ -1682,7 +1845,7 @@ incServerStat c userId ProtocolServer {host} cmd res = do
   where
     statsKey = AgentStatsKey {userId, host = strEncode $ L.head host, clientTs = "", cmd, res}
 
-incClientStatN :: ProtocolServerClient v err msg => AgentClient -> UserId -> Client msg -> Int -> ByteString -> ByteString -> IO ()
+incClientStatN :: ProtocolServerClient v err msg => AgentClient -> UserId -> ProtoClient msg -> Int -> ByteString -> ByteString -> IO ()
 incClientStatN c userId pc n cmd res = do
   atomically $ incStat c n statsKey
   where
diff --git a/src/Simplex/Messaging/Agent/Protocol.hs b/src/Simplex/Messaging/Agent/Protocol.hs
index e136a8bbb..1fc984ac5 100644
--- a/src/Simplex/Messaging/Agent/Protocol.hs
+++ b/src/Simplex/Messaging/Agent/Protocol.hs
@@ -189,6 +189,7 @@ import Simplex.FileTransfer.Description
 import Simplex.FileTransfer.Protocol (FileParty (..))
 import Simplex.FileTransfer.Transport (XFTPErrorType)
 import Simplex.Messaging.Agent.QueryString
+import Simplex.Messaging.Client (ProxyClientError)
 import qualified Simplex.Messaging.Crypto as C
 import Simplex.Messaging.Crypto.Ratchet
   ( InitialKeys (..),
@@ -206,6 +207,7 @@ import Simplex.Messaging.Encoding.String
 import Simplex.Messaging.Parsers
 import Simplex.Messaging.Protocol
   ( AProtocolType,
+    BrokerErrorType (..),
     EntityId,
     ErrorType,
     MsgBody,
@@ -233,7 +235,7 @@ import Simplex.Messaging.Protocol
   )
 import qualified Simplex.Messaging.Protocol as SMP
 import Simplex.Messaging.ServiceScheme
-import Simplex.Messaging.Transport (Transport (..), TransportError, serializeTransportError, transportErrorP)
+import Simplex.Messaging.Transport (Transport (..))
 import Simplex.Messaging.Transport.Client (TransportHost, TransportHosts_ (..))
 import Simplex.Messaging.Util
 import Simplex.Messaging.Version
@@ -393,7 +395,8 @@ data ACommand (p :: AParty) (e :: AEntity) where
   RSYNC :: RatchetSyncState -> Maybe AgentCryptoError -> ConnectionStats -> ACommand Agent AEConn
   SEND :: PQEncryption -> MsgFlags -> MsgBody -> ACommand Client AEConn
   MID :: AgentMsgId -> PQEncryption -> ACommand Agent AEConn
-  SENT :: AgentMsgId -> ACommand Agent AEConn
+  SENT :: AgentMsgId -> Maybe SMPServer -> ACommand Agent AEConn
+  MWARN :: AgentMsgId -> AgentErrorType -> ACommand Agent AEConn
   MERR :: AgentMsgId -> AgentErrorType -> ACommand Agent AEConn
   MERRS :: NonEmpty AgentMsgId -> AgentErrorType -> ACommand Agent AEConn
   MSG :: MsgMeta -> MsgFlags -> MsgBody -> ACommand Agent AEConn
@@ -457,6 +460,7 @@ data ACommandTag (p :: AParty) (e :: AEntity) where
   SEND_ :: ACommandTag Client AEConn
   MID_ :: ACommandTag Agent AEConn
   SENT_ :: ACommandTag Agent AEConn
+  MWARN_ :: ACommandTag Agent AEConn
   MERR_ :: ACommandTag Agent AEConn
   MERRS_ :: ACommandTag Agent AEConn
   MSG_ :: ACommandTag Agent AEConn
@@ -512,7 +516,8 @@ aCommandTag = \case
   RSYNC {} -> RSYNC_
   SEND {} -> SEND_
   MID {} -> MID_
-  SENT _ -> SENT_
+  SENT {} -> SENT_
+  MWARN {} -> MWARN_
   MERR {} -> MERR_
   MERRS {} -> MERRS_
   MSG {} -> MSG_
@@ -1300,6 +1305,7 @@ instance VersionRangeI SMPClientVersion SMPQueueUri where
   type VersionT SMPClientVersion SMPQueueUri = SMPQueueInfo
   versionRange = clientVRange
   toVersionT (SMPQueueUri _vr addr) v = SMPQueueInfo v addr
+  toVersionRange (SMPQueueUri _vr addr) vr = SMPQueueUri vr addr
 
 -- | SMP queue information sent out-of-band.
 --
@@ -1474,6 +1480,8 @@ data AgentErrorType
     NTF {serverAddress :: String, ntfErr :: ErrorType}
   | -- | XFTP protocol errors forwarded to agent clients
     XFTP {serverAddress :: String, xftpErr :: XFTPErrorType}
+  | -- | SMP proxy errors
+    PROXY {proxyServer :: String, relayServer :: String, proxyErr :: ProxyClientError}
   | -- | XRCP protocol errors forwarded to agent clients
     RCP {rcpErr :: RCErrorType}
   | -- | SMP server errors
@@ -1516,22 +1524,6 @@ data ConnectionErrorType
     NOT_AVAILABLE
   deriving (Eq, Read, Show, Exception)
 
--- | SMP server errors.
-data BrokerErrorType
-  = -- | invalid server response (failed to parse)
-    RESPONSE {smpErr :: String}
-  | -- | unexpected response
-    UNEXPECTED
-  | -- | network error
-    NETWORK
-  | -- | no compatible server host (e.g. onion when public is required, or vice versa)
-    HOST
-  | -- | handshake or other transport error
-    TRANSPORT {transportErr :: TransportError}
-  | -- | command response timeout
-    TIMEOUT
-  deriving (Eq, Read, Show, Exception)
-
 -- | Errors of another SMP agent.
 data SMPAgentError
   = -- | client or agent message that failed to parse
@@ -1566,12 +1558,14 @@ data AgentCryptoError
 
 instance StrEncoding AgentCryptoError where
   strP =
-    "DECRYPT_AES" $> DECRYPT_AES
-      <|> "DECRYPT_CB" $> DECRYPT_CB
-      <|> "RATCHET_HEADER" $> RATCHET_HEADER
-      <|> "RATCHET_EARLIER " *> (RATCHET_EARLIER <$> strP)
-      <|> "RATCHET_SKIPPED " *> (RATCHET_SKIPPED <$> strP)
-      <|> "RATCHET_SYNC" $> RATCHET_SYNC
+    A.takeTill (== ' ') >>= \case
+      "DECRYPT_AES" -> pure DECRYPT_AES
+      "DECRYPT_CB" -> pure DECRYPT_CB
+      "RATCHET_HEADER" -> pure RATCHET_HEADER
+      "RATCHET_EARLIER" -> RATCHET_EARLIER <$> _strP
+      "RATCHET_SKIPPED" -> RATCHET_SKIPPED <$> _strP
+      "RATCHET_SYNC" -> pure RATCHET_SYNC
+      _ -> fail "AgentCryptoError"
   strEncode = \case
     DECRYPT_AES -> "DECRYPT_AES"
     DECRYPT_CB -> "DECRYPT_CB"
@@ -1582,42 +1576,59 @@ instance StrEncoding AgentCryptoError where
 
 instance StrEncoding AgentErrorType where
   strP =
-    "CMD " *> (CMD <$> parseRead1)
-      <|> "CONN " *> (CONN <$> parseRead1)
-      <|> "SMP " *> (SMP <$> textP <*> _strP)
-      <|> "NTF " *> (NTF <$> textP <*> _strP)
-      <|> "XFTP " *> (XFTP <$> textP <*> _strP)
-      <|> "RCP " *> (RCP <$> strP)
-      <|> "BROKER " *> (BROKER <$> textP <* " RESPONSE " <*> (RESPONSE <$> textP))
-      <|> "BROKER " *> (BROKER <$> textP <* " TRANSPORT " <*> (TRANSPORT <$> transportErrorP))
-      <|> "BROKER " *> (BROKER <$> textP <* A.space <*> parseRead1)
-      <|> "AGENT CRYPTO " *> (AGENT . A_CRYPTO <$> parseRead A.takeByteString)
-      <|> "AGENT QUEUE " *> (AGENT . A_QUEUE <$> parseRead A.takeByteString)
-      <|> "AGENT " *> (AGENT <$> parseRead1)
-      <|> "INTERNAL " *> (INTERNAL <$> parseRead A.takeByteString)
-      <|> "CRITICAL " *> (CRITICAL <$> parseRead1 <* A.space <*> parseRead A.takeByteString)
-      <|> "INACTIVE" $> INACTIVE
+    A.takeTill (== ' ')
+      >>= \case
+        "CMD" -> CMD <$> (A.space *> parseRead1)
+        "CONN" -> CONN <$> (A.space *> parseRead1)
+        "SMP" -> SMP <$> (A.space *> srvP) <*> _strP
+        "NTF" -> NTF <$> (A.space *> srvP) <*> _strP
+        "XFTP" -> XFTP <$> (A.space *> srvP) <*> _strP
+        "PROXY" -> PROXY <$> (A.space *> srvP) <* A.space <*> srvP <*> _strP
+        "RCP" -> RCP <$> _strP
+        "BROKER" -> BROKER <$> (A.space *> srvP) <*> _strP
+        "AGENT" -> AGENT <$> _strP
+        "INTERNAL" -> INTERNAL <$> (A.space *> textP)
+        "CRITICAL" -> CRITICAL <$> (A.space *> parseRead1) <*> (A.space *> textP)
+        "INACTIVE" -> pure INACTIVE
+        _ -> fail "bad AgentErrorType"
     where
-      textP = T.unpack . safeDecodeUtf8 <$> A.takeTill (== ' ')
+      srvP = T.unpack . safeDecodeUtf8 <$> A.takeTill (== ' ')
+      textP = T.unpack . safeDecodeUtf8 <$> A.takeByteString
   strEncode = \case
     CMD e -> "CMD " <> bshow e
     CONN e -> "CONN " <> bshow e
     SMP srv e -> "SMP " <> text srv <> " " <> strEncode e
     NTF srv e -> "NTF " <> text srv <> " " <> strEncode e
     XFTP srv e -> "XFTP " <> text srv <> " " <> strEncode e
+    PROXY pxy srv e -> B.unwords ["PROXY", text pxy, text srv, strEncode e]
     RCP e -> "RCP " <> strEncode e
-    BROKER srv (RESPONSE e) -> "BROKER " <> text srv <> " RESPONSE " <> text e
-    BROKER srv (TRANSPORT e) -> "BROKER " <> text srv <> " TRANSPORT " <> serializeTransportError e
-    BROKER srv e -> "BROKER " <> text srv <> " " <> bshow e
-    AGENT (A_CRYPTO e) -> "AGENT CRYPTO " <> bshow e
-    AGENT (A_QUEUE e) -> "AGENT QUEUE " <> bshow e
-    AGENT e -> "AGENT " <> bshow e
-    INTERNAL e -> "INTERNAL " <> bshow e
-    CRITICAL restart e -> "CRITICAL " <> bshow restart <> " " <> bshow e
+    BROKER srv e -> B.unwords ["BROKER", text srv, strEncode e]
+    AGENT e -> "AGENT " <> strEncode e
+    INTERNAL e -> "INTERNAL " <> encodeUtf8 (T.pack e)
+    CRITICAL restart e -> "CRITICAL " <> bshow restart <> " " <> encodeUtf8 (T.pack e)
     INACTIVE -> "INACTIVE"
     where
       text = encodeUtf8 . T.pack
 
+instance StrEncoding SMPAgentError where
+  strP =
+    A.takeTill (== ' ')
+      >>= \case
+        "MESSAGE" -> pure A_MESSAGE
+        "PROHIBITED" -> pure A_PROHIBITED
+        "VERSION" -> pure A_VERSION
+        "CRYPTO" -> A_CRYPTO <$> _strP
+        "DUPLICATE" -> pure A_DUPLICATE
+        "QUEUE" -> A_QUEUE . T.unpack . safeDecodeUtf8 <$> (A.space *> A.takeByteString)
+        _ -> fail "bad SMPAgentError"
+  strEncode = \case
+    A_MESSAGE -> "MESSAGE"
+    A_PROHIBITED -> "PROHIBITED"
+    A_VERSION -> "VERSION"
+    A_CRYPTO e -> "CRYPTO " <> strEncode e
+    A_DUPLICATE -> "DUPLICATE"
+    A_QUEUE e -> "QUEUE " <> encodeUtf8 (T.pack e)
+
 cryptoErrToSyncState :: AgentCryptoError -> RatchetSyncState
 cryptoErrToSyncState = \case
   DECRYPT_AES -> RSAllowed
@@ -1660,6 +1671,7 @@ instance StrEncoding ACmdTag where
       "SEND" -> t SEND_
       "MID" -> ct MID_
       "SENT" -> ct SENT_
+      "MWARN" -> ct MWARN_
       "MERR" -> ct MERR_
       "MERRS" -> ct MERRS_
       "MSG" -> ct MSG_
@@ -1718,6 +1730,7 @@ instance (APartyI p, AEntityI e) => StrEncoding (ACommandTag p e) where
     SEND_ -> "SEND"
     MID_ -> "MID"
     SENT_ -> "SENT"
+    MWARN_ -> "MWARN"
     MERR_ -> "MERR"
     MERRS_ -> "MERRS"
     MSG_ -> "MSG"
@@ -1788,7 +1801,8 @@ commandP binaryP =
           SWITCH_ -> s (SWITCH <$> strP_ <*> strP_ <*> strP)
           RSYNC_ -> s (RSYNC <$> strP_ <*> strP <*> strP)
           MID_ -> s (MID <$> A.decimal <*> _strP)
-          SENT_ -> s (SENT <$> A.decimal)
+          SENT_ -> s (SENT <$> A.decimal <*> _strP)
+          MWARN_ -> s (MWARN <$> A.decimal <* A.space <*> strP)
           MERR_ -> s (MERR <$> A.decimal <* A.space <*> strP)
           MERRS_ -> s (MERRS <$> strP_ <*> strP)
           MSG_ -> s (MSG <$> strP <* A.space <*> smpP <* A.space <*> binaryP)
@@ -1851,7 +1865,8 @@ serializeCommand = \case
   RSYNC rrState cryptoErr cstats -> s (RSYNC_, rrState, cryptoErr, cstats)
   SEND pqEnc msgFlags msgBody -> B.unwords [s SEND_, s pqEnc, smpEncode msgFlags, serializeBinary msgBody]
   MID mId pqEnc -> s (MID_, mId, pqEnc)
-  SENT mId -> s (SENT_, mId)
+  SENT mId proxySrv_ -> s (SENT_, mId, proxySrv_)
+  MWARN mId e -> s (MWARN_, mId, e)
   MERR mId e -> s (MERR_, mId, e)
   MERRS mIds e -> s (MERRS_, mIds, e)
   MSG msgMeta msgFlags msgBody -> B.unwords [s MSG_, s msgMeta, smpEncode msgFlags, serializeBinary msgBody]
@@ -1977,8 +1992,6 @@ $(J.deriveJSON (sumTypeJSON id) ''CommandErrorType)
 
 $(J.deriveJSON (sumTypeJSON id) ''ConnectionErrorType)
 
-$(J.deriveJSON (sumTypeJSON id) ''BrokerErrorType)
-
 $(J.deriveJSON (sumTypeJSON id) ''AgentCryptoError)
 
 $(J.deriveJSON (sumTypeJSON id) ''SMPAgentError)
diff --git a/src/Simplex/Messaging/Client.hs b/src/Simplex/Messaging/Client.hs
index 6cee90839..97a2867ca 100644
--- a/src/Simplex/Messaging/Client.hs
+++ b/src/Simplex/Messaging/Client.hs
@@ -30,9 +30,11 @@ module Simplex.Messaging.Client
     TransportSession,
     ProtocolClient (thParams, sessionTs),
     SMPClient,
+    ProxiedRelay (..),
     getProtocolClient,
     closeProtocolClient,
     protocolClientServer,
+    protocolClientServer',
     transportHost',
     transportSession',
 
@@ -54,14 +56,22 @@ module Simplex.Messaging.Client
     suspendSMPQueue,
     deleteSMPQueue,
     deleteSMPQueues,
+    connectSMPProxiedRelay,
+    proxySMPMessage,
+    forwardSMPMessage,
     sendProtocolCommand,
 
     -- * Supporting types and client configuration
     ProtocolClientError (..),
     SMPClientError,
+    ProxyClientError (..),
     ProtocolClientConfig (..),
     NetworkConfig (..),
     TransportSessionMode (..),
+    HostMode (..),
+    SocksMode (..),
+    SMPProxyMode (..),
+    SMPProxyFallback (..),
     defaultClientConfig,
     defaultSMPClientConfig,
     defaultNetworkConfig,
@@ -69,6 +79,7 @@ module Simplex.Messaging.Client
     chooseTransportHost,
     proxyUsername,
     temporaryClientError,
+    smpProxyError,
     ServerTransmission,
     TransmissionType (..),
     ClientCommand,
@@ -92,6 +103,7 @@ import Control.Monad.IO.Class (liftIO)
 import Control.Monad.Trans.Except
 import Crypto.Random (ChaChaDRG)
 import qualified Data.Aeson.TH as J
+import qualified Data.Attoparsec.ByteString.Char8 as A
 import Data.ByteString.Char8 (ByteString)
 import qualified Data.ByteString.Char8 as B
 import Data.Functor (($>))
@@ -101,9 +113,12 @@ import Data.List.NonEmpty (NonEmpty (..))
 import qualified Data.List.NonEmpty as L
 import Data.Maybe (fromMaybe)
 import Data.Time.Clock (UTCTime (..), diffUTCTime, getCurrentTime)
+import qualified Data.X509 as X
+import qualified Data.X509.Validation as XV
 import Network.Socket (ServiceName)
 import Numeric.Natural
 import qualified Simplex.Messaging.Crypto as C
+import Simplex.Messaging.Encoding
 import Simplex.Messaging.Encoding.String
 import Simplex.Messaging.Parsers (defaultJSON, dropPrefix, enumJSON)
 import Simplex.Messaging.Protocol
@@ -113,7 +128,7 @@ import Simplex.Messaging.Transport
 import Simplex.Messaging.Transport.Client (SocksProxy, TransportClientConfig (..), TransportHost (..), defaultTcpConnectTimeout, runTransportClient)
 import Simplex.Messaging.Transport.KeepAlive
 import Simplex.Messaging.Transport.WebSockets (WS)
-import Simplex.Messaging.Util (bshow, diffToMicroseconds, ifM, raceAny_, threadDelay', tshow, whenM)
+import Simplex.Messaging.Util (bshow, diffToMicroseconds, ifM, liftEitherWith, raceAny_, threadDelay', tshow, whenM)
 import Simplex.Messaging.Version
 import System.Timeout (timeout)
 
@@ -131,6 +146,7 @@ data PClient v err msg = PClient
   { connected :: TVar Bool,
     transportSession :: TransportSession msg,
     transportHost :: TransportHost,
+    tcpConnectTimeout :: Int,
     tcpTimeout :: Int,
     sendPings :: TVar Bool,
     lastReceived :: TVar UTCTime,
@@ -160,6 +176,7 @@ smpClientStub g sessionId thVersion thAuth = do
           THandleParams
             { sessionId,
               thVersion,
+              thServerVRange = supportedServerSMPRelayVRange,
               thAuth,
               blockSize = smpBlockSize,
               implySessId = thVersion >= authCmdsSMPVersion,
@@ -171,6 +188,7 @@ smpClientStub g sessionId thVersion thAuth = do
             { connected,
               transportSession = (1, "smp://LcJUMfVhwD8yxjAiSaDzzGF3-kLG4Uh0Fl_ZIjrRwjI=@localhost:5001", Nothing),
               transportHost = "localhost",
+              tcpConnectTimeout = 20_000_000,
               tcpTimeout = 15_000_000,
               sendPings,
               lastReceived,
@@ -202,16 +220,30 @@ data HostMode
     HMPublic
   deriving (Eq, Show)
 
+data SocksMode
+  = -- | always use SOCKS proxy when enabled
+    SMAlways
+  | -- | use SOCKS proxy only for .onion hosts when no public host is available
+    -- This mode is used in SMP proxy to minimize SOCKS proxy usage.
+    SMOnion
+  deriving (Eq, Show)
+
 -- | network configuration for the client
 data NetworkConfig = NetworkConfig
   { -- | use SOCKS5 proxy
     socksProxy :: Maybe SocksProxy,
+    -- | when to use SOCKS proxy
+    socksMode :: SocksMode,
     -- | determines critera which host is chosen from the list
     hostMode :: HostMode,
     -- | if above criteria is not met, if the below setting is True return error, otherwise use the first host
     requiredHostMode :: Bool,
     -- | transport sessions are created per user or per entity
     sessionMode :: TransportSessionMode,
+    -- | SMP proxy mode
+    smpProxyMode :: SMPProxyMode,
+    -- | Fallback to direct connection when destination SMP relay does not support SMP proxy protocol extensions
+    smpProxyFallback :: SMPProxyFallback,
     -- | timeout for the initial client TCP/TLS connection (microseconds)
     tcpConnectTimeout :: Int,
     -- | timeout of protocol commands (microseconds)
@@ -233,13 +265,30 @@ data NetworkConfig = NetworkConfig
 data TransportSessionMode = TSMUser | TSMEntity
   deriving (Eq, Show)
 
+-- SMP proxy mode for sending messages
+data SMPProxyMode
+  = SPMAlways
+  | SPMUnknown -- use with unknown relays
+  | SPMUnprotected -- use with unknown relays when IP address is not protected (i.e., when neither SOCKS proxy nor .onion address is used)
+  | SPMNever
+  deriving (Eq, Show)
+
+data SMPProxyFallback
+  = SPFAllow -- connect directly when chosen proxy or destination relay do not support proxy protocol.
+  | SPFAllowProtected -- connect directly only when IP address is protected (SOCKS proxy or .onion address is used).
+  | SPFProhibit -- prohibit direct connection to destination relay.
+  deriving (Eq, Show)
+
 defaultNetworkConfig :: NetworkConfig
 defaultNetworkConfig =
   NetworkConfig
     { socksProxy = Nothing,
+      socksMode = SMAlways,
       hostMode = HMOnionViaSocks,
       requiredHostMode = False,
       sessionMode = TSMUser,
+      smpProxyMode = SPMNever,
+      smpProxyFallback = SPFAllow,
       tcpConnectTimeout = defaultTcpConnectTimeout,
       tcpTimeout = 15_000_000,
       tcpTimeoutPerKb = 5_000,
@@ -250,9 +299,14 @@ defaultNetworkConfig =
       logTLSErrors = False
     }
 
-transportClientConfig :: NetworkConfig -> TransportClientConfig
-transportClientConfig NetworkConfig {socksProxy, tcpConnectTimeout, tcpKeepAlive, logTLSErrors} =
-  TransportClientConfig {socksProxy, tcpConnectTimeout, tcpKeepAlive, logTLSErrors, clientCredentials = Nothing, alpn = Nothing}
+transportClientConfig :: NetworkConfig -> TransportHost -> TransportClientConfig
+transportClientConfig NetworkConfig {socksProxy, socksMode, tcpConnectTimeout, tcpKeepAlive, logTLSErrors} host =
+  TransportClientConfig {socksProxy = useSocksProxy socksMode, tcpConnectTimeout, tcpKeepAlive, logTLSErrors, clientCredentials = Nothing, alpn = Nothing}
+  where
+    useSocksProxy SMAlways = socksProxy
+    useSocksProxy SMOnion = case host of
+      THOnionHost _ -> socksProxy
+      _ -> Nothing
 {-# INLINE transportClientConfig #-}
 
 -- | protocol client configuration.
@@ -266,7 +320,7 @@ data ProtocolClientConfig v = ProtocolClientConfig
     clientALPN :: Maybe [ALPN],
     -- | client-server protocol version range
     serverVRange :: VersionRange v,
-    -- | agree shared session secret (used in SMP proxy)
+    -- | agree shared session secret (used in SMP proxy for additional encryption layer)
     agreeSecret :: Bool
   }
 
@@ -315,10 +369,14 @@ chooseTransportHost NetworkConfig {socksProxy, hostMode, requiredHostMode} hosts
     publicHost = find (not . isOnionHost) hosts
 
 protocolClientServer :: ProtocolTypeI (ProtoType msg) => ProtocolClient v err msg -> String
-protocolClientServer = B.unpack . strEncode . snd3 . transportSession . client_
+protocolClientServer = B.unpack . strEncode . protocolClientServer'
+{-# INLINE protocolClientServer #-}
+
+protocolClientServer' :: ProtocolClient v err msg -> ProtoServer msg
+protocolClientServer' = snd3 . transportSession . client_
   where
     snd3 (_, s, _) = s
-{-# INLINE protocolClientServer #-}
+{-# INLINE protocolClientServer' #-}
 
 transportHost' :: ProtocolClient v err msg -> TransportHost
 transportHost' = transportHost . client_
@@ -362,6 +420,7 @@ getProtocolClient g transportSession@(_, srv, _) cfg@ProtocolClientConfig {qSize
           { connected,
             transportSession,
             transportHost,
+            tcpConnectTimeout,
             tcpTimeout,
             sendPings,
             lastReceived,
@@ -376,7 +435,7 @@ getProtocolClient g transportSession@(_, srv, _) cfg@ProtocolClientConfig {qSize
     runClient :: (ServiceName, ATransport) -> TransportHost -> PClient v err msg -> IO (Either (ProtocolClientError err) (ProtocolClient v err msg))
     runClient (port', ATransport t) useHost c = do
       cVar <- newEmptyTMVarIO
-      let tcConfig = (transportClientConfig networkConfig) {alpn = clientALPN}
+      let tcConfig = (transportClientConfig networkConfig useHost) {alpn = clientALPN}
           username = proxyUsername transportSession
       action <-
         async $
@@ -521,6 +580,19 @@ temporaryClientError = \case
   _ -> False
 {-# INLINE temporaryClientError #-}
 
+-- converts error of client running on proxy to the error sent to client connected to proxy
+smpProxyError :: SMPClientError -> ErrorType
+smpProxyError = \case
+  PCEProtocolError e -> PROXY $ PROTOCOL e
+  PCEResponseError e -> PROXY $ BROKER $ RESPONSE $ B.unpack $ strEncode e
+  PCEUnexpectedResponse s -> PROXY $ BROKER $ UNEXPECTED $ B.unpack $ B.take 32 s
+  PCEResponseTimeout -> PROXY $ BROKER TIMEOUT
+  PCENetworkError -> PROXY $ BROKER NETWORK
+  PCEIncompatibleHost -> PROXY $ BROKER HOST
+  PCETransportError t -> PROXY $ BROKER $ TRANSPORT t
+  PCECryptoError _ -> CRYPTO
+  PCEIOError _ -> INTERNAL
+
 -- | Create a new SMP queue.
 --
 -- https://github.com/simplex-chat/simplexmq/blob/master/protocol/simplex-messaging.md#create-queue-command
@@ -674,6 +746,156 @@ deleteSMPQueues :: SMPClient -> NonEmpty (RcvPrivateAuthKey, RecipientId) -> IO
 deleteSMPQueues = okSMPCommands DEL
 {-# INLINE deleteSMPQueues #-}
 
+-- send PRXY :: SMPServer -> Maybe BasicAuth -> Command Sender
+-- receives PKEY :: SessionId -> X.CertificateChain -> X.SignedExact X.PubKey -> BrokerMsg
+connectSMPProxiedRelay :: SMPClient -> SMPServer -> Maybe BasicAuth -> ExceptT SMPClientError IO ProxiedRelay
+connectSMPProxiedRelay c@ProtocolClient {client_ = PClient {tcpConnectTimeout, tcpTimeout}} relayServ@ProtocolServer {keyHash = C.KeyHash kh} proxyAuth
+  | thVersion (thParams c) >= sendingProxySMPVersion =
+      sendProtocolCommand_ c Nothing tOut Nothing "" (Cmd SProxiedClient (PRXY relayServ proxyAuth)) >>= \case
+        PKEY sId vr (chain, key) ->
+          case supportedClientSMPRelayVRange `compatibleVersion` vr of
+            Nothing -> throwE $ transportErr TEVersion
+            Just (Compatible v) -> liftEitherWith (const $ transportErr $ TEHandshake IDENTITY) $ ProxiedRelay sId v <$> validateRelay chain key
+        r -> throwE . PCEUnexpectedResponse $ bshow r
+  | otherwise = throwE $ PCETransportError TEVersion
+  where
+    tOut = Just $ tcpConnectTimeout + tcpTimeout
+    transportErr = PCEProtocolError . PROXY . BROKER . TRANSPORT
+    validateRelay :: X.CertificateChain -> X.SignedExact X.PubKey -> Either String C.PublicKeyX25519
+    validateRelay (X.CertificateChain cert) exact = do
+      serverKey <- case cert of
+        [leaf, ca]
+          | XV.Fingerprint kh == XV.getFingerprint ca X.HashSHA256 ->
+              C.x509ToPublic (X.certPubKey . X.signedObject $ X.getSigned leaf, []) >>= C.pubKey
+        _ -> throwError "bad certificate"
+      pubKey <- C.verifyX509 serverKey exact
+      C.x509ToPublic (pubKey, []) >>= C.pubKey
+
+data ProxiedRelay = ProxiedRelay
+  { prSessionId :: SessionId,
+    prVersion :: VersionSMP,
+    prServerKey :: C.PublicKeyX25519
+  }
+
+data ProxyClientError
+  = -- | protocol error response from proxy
+    ProxyProtocolError ErrorType
+  | -- | unexpexted response
+    ProxyUnexpectedResponse String
+  | -- | error between proxy and server
+    ProxyResponseError ErrorType
+  deriving (Eq, Show, Exception)
+
+instance StrEncoding ProxyClientError where
+  strEncode = \case
+    ProxyProtocolError e -> "PROTOCOL " <> strEncode e
+    ProxyUnexpectedResponse s -> "UNEXPECTED " <> B.pack s
+    ProxyResponseError e -> "SYNTAX " <> strEncode e
+  strP =
+    A.takeTill (== ' ') >>= \case
+      "PROTOCOL" -> ProxyProtocolError <$> _strP
+      "UNEXPECTED" -> ProxyUnexpectedResponse . B.unpack <$> (A.space *> A.takeByteString)
+      "SYNTAX" -> ProxyResponseError <$> _strP
+      _ -> fail "bad ProxyClientError"
+
+-- consider how to process slow responses - is it handled somehow locally or delegated to the caller
+-- this method is used in the client
+-- sends PFWD :: C.PublicKeyX25519 -> EncTransmission -> Command Sender
+-- receives PRES :: EncResponse -> BrokerMsg -- proxy to client
+
+-- When client sends message via proxy, there may be one successful scenario and 9 error scenarios
+-- as shown below (WTF stands for unexpected response, ??? for response that failed to parse).
+--    client        proxy   relay   proxy        client
+-- 0) PFWD(SEND) -> RFWD -> RRES -> PRES(OK)  -> ok
+-- 1) PFWD(SEND) -> RFWD -> RRES -> PRES(ERR) -> PCEProtocolError - business logic error for client
+-- 2) PFWD(SEND) -> RFWD -> RRES -> PRES(WTF) -> PCEUnexpectedReponse - relay/client protocol logic error
+-- 3) PFWD(SEND) -> RFWD -> RRES -> PRES(???) -> PCEResponseError - relay/client syntax error
+-- 4) PFWD(SEND) -> RFWD -> ERR ->  ERR PROXY PROTOCOL -> ProxyProtocolError - proxy/relay business logic error
+-- 5) PFWD(SEND) -> RFWD -> WTF ->  ERR PROXY $ BROKER (UNEXPECTED s) -> ProxyProtocolError - proxy/relay protocol logic
+-- 6) PFWD(SEND) -> RFWD -> ??? ->  ERR PROXY $ BROKER (RESPONSE s) -> ProxyProtocolError - - proxy/relay syntax
+-- 7) PFWD(SEND) -> ERR  -> ProxyProtocolError - client/proxy business logic
+-- 8) PFWD(SEND) -> WTF  -> ProxyUnexpectedResponse - client/proxy protocol logic
+-- 9) PFWD(SEND) -> ???  -> ProxyResponseError - client/proxy syntax
+--
+-- We report as proxySMPMessage error (ExceptT error) the errors of two kinds:
+-- - protocol errors from the destination relay wrapped in PRES - to simplify processing of AUTH and QUOTA errors, in this case proxy is "transparent" for such errors (PCEProtocolError, PCEUnexpectedResponse, PCEResponseError)
+-- - other response/transport/connection errors from the client connected to proxy itself
+-- Other errors are reported in the function result as `Either ProxiedRelayError ()`, including
+-- - protocol  errors from the client connected to proxy in ProxyClientError (PCEProtocolError, PCEUnexpectedResponse, PCEResponseError)
+-- - other errors from the client running on proxy and connected to relay in PREProxiedRelayError
+
+proxySMPMessage ::
+  SMPClient ->
+  -- proxy session from PKEY
+  ProxiedRelay ->
+  -- message to deliver
+  Maybe SndPrivateAuthKey ->
+  SenderId ->
+  MsgFlags ->
+  MsgBody ->
+  ExceptT SMPClientError IO (Either ProxyClientError ())
+proxySMPMessage c@ProtocolClient {thParams = proxyThParams, client_ = PClient {clientCorrId = g, tcpTimeout}} (ProxiedRelay sessionId v serverKey) spKey sId flags msg = do
+  -- prepare params
+  let serverThAuth = (\ta -> ta {serverPeerPubKey = serverKey}) <$> thAuth proxyThParams
+      serverThParams = smpTHParamsSetVersion v proxyThParams {sessionId, thAuth = serverThAuth}
+  (cmdPubKey, cmdPrivKey) <- liftIO . atomically $ C.generateKeyPair @'C.X25519 g
+  let cmdSecret = C.dh' serverKey cmdPrivKey
+  nonce@(C.CbNonce corrId) <- liftIO . atomically $ C.randomCbNonce g
+  -- encode
+  let TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth serverThParams (CorrId corrId, sId, Cmd SSender (SEND flags msg))
+  auth <- liftEitherWith PCETransportError $ authTransmission serverThAuth spKey nonce tForAuth
+  b <- case batchTransmissions (batch serverThParams) (blockSize serverThParams) [Right (auth, tToSend)] of
+    [] -> throwE $ PCETransportError TELargeMsg
+    TBError e _ : _ -> throwE $ PCETransportError e
+    TBTransmission s _ : _ -> pure s
+    TBTransmissions s _ _ : _ -> pure s
+  et <- liftEitherWith PCECryptoError $ EncTransmission <$> C.cbEncrypt cmdSecret nonce b paddedProxiedMsgLength
+  -- proxy interaction errors are wrapped
+  let tOut = Just $ 2 * tcpTimeout
+  tryE (sendProtocolCommand_ c (Just nonce) tOut Nothing sessionId (Cmd SProxiedClient (PFWD v cmdPubKey et))) >>= \case
+    Right r -> case r of
+      PRES (EncResponse er) -> do
+        -- server interaction errors are thrown directly
+        t' <- liftEitherWith PCECryptoError $ C.cbDecrypt cmdSecret (C.reverseNonce nonce) er
+        case tParse serverThParams t' of
+          t'' :| [] -> case tDecodeParseValidate serverThParams t'' of
+            (_auth, _signed, (_c, _e, cmd)) -> case cmd of
+              Right OK -> pure $ Right ()
+              Right (ERR e) -> throwE $ PCEProtocolError e -- this is the error from the destination relay
+              Right e -> throwE $ PCEUnexpectedResponse $ B.take 32 $ bshow e
+              Left e -> throwE $ PCEResponseError e
+          _ -> throwE $ PCETransportError TEBadBlock
+      ERR e -> pure . Left $ ProxyProtocolError e -- this will not happen, this error is returned via Left
+      _ -> pure . Left $ ProxyUnexpectedResponse $ take 32 $ show r
+    Left e -> case e of
+      PCEProtocolError e' -> pure . Left $ ProxyProtocolError e'
+      PCEUnexpectedResponse r -> pure . Left $ ProxyUnexpectedResponse $ B.unpack r
+      PCEResponseError e' -> pure . Left $ ProxyResponseError e'
+      _ -> throwE e
+
+-- this method is used in the proxy
+-- sends RFWD :: EncFwdTransmission -> Command Sender
+-- receives RRES :: EncFwdResponse -> BrokerMsg
+-- proxy should send PRES to the client with EncResponse
+forwardSMPMessage :: SMPClient -> CorrId -> VersionSMP -> C.PublicKeyX25519 -> EncTransmission -> ExceptT SMPClientError IO EncResponse
+forwardSMPMessage c@ProtocolClient {thParams, client_ = PClient {clientCorrId = g}} fwdCorrId fwdVersion fwdKey fwdTransmission = do
+  -- prepare params
+  sessSecret <- case thAuth thParams of
+    Nothing -> throwError $ PCETransportError TENoServerAuth
+    Just THAuthClient {sessSecret} -> maybe (throwError $ PCETransportError TENoServerAuth) pure sessSecret
+  nonce <- liftIO . atomically $ C.randomCbNonce g
+  -- wrap
+  let fwdT = FwdTransmission {fwdCorrId, fwdVersion, fwdKey, fwdTransmission}
+      eft = EncFwdTransmission $ C.cbEncryptNoPad sessSecret nonce (smpEncode fwdT)
+  -- send
+  sendProtocolCommand_ c (Just nonce) Nothing Nothing "" (Cmd SSender (RFWD eft)) >>= \case
+    RRES (EncFwdResponse efr) -> do
+      -- unwrap
+      r' <- liftEitherWith PCECryptoError $ C.cbDecryptNoPad sessSecret (C.reverseNonce nonce) efr
+      FwdResponse {fwdCorrId = _, fwdResponse} <- liftEitherWith (const $ PCEResponseError BLOCK) $ smpDecode r'
+      pure fwdResponse
+    r -> throwE . PCEUnexpectedResponse $ B.take 32 $ bshow r
+
 okSMPCommand :: PartyI p => Command p -> SMPClient -> C.APrivateAuthKey -> QueueId -> ExceptT SMPClientError IO ()
 okSMPCommand cmd c pKey qId =
   sendSMPCommand c (Just pKey) qId cmd >>= \case
@@ -729,16 +951,19 @@ sendBatch c@ProtocolClient {client_ = PClient {sndQ}} b = do
     TBTransmissions s n rs
       | n > 0 -> do
           atomically $ writeTBQueue sndQ s
-          mapConcurrently (getResponse c) rs
+          mapConcurrently (getResponse c Nothing) rs
       | otherwise -> pure []
     TBTransmission s r -> do
       atomically $ writeTBQueue sndQ s
-      (: []) <$> getResponse c r
+      (: []) <$> getResponse c Nothing r
 
 -- | Send Protocol command
 sendProtocolCommand :: forall v err msg. Protocol v err msg => ProtocolClient v err msg -> Maybe C.APrivateAuthKey -> EntityId -> ProtoCommand msg -> ExceptT (ProtocolClientError err) IO msg
-sendProtocolCommand c@ProtocolClient {client_ = PClient {sndQ}, thParams = THandleParams {batch, blockSize}} pKey entId cmd =
-  ExceptT $ uncurry sendRecv =<< mkTransmission c (pKey, entId, cmd)
+sendProtocolCommand c = sendProtocolCommand_ c Nothing Nothing
+
+sendProtocolCommand_ :: forall v err msg. Protocol v err msg => ProtocolClient v err msg -> Maybe C.CbNonce -> Maybe Int -> Maybe C.APrivateAuthKey -> EntityId -> ProtoCommand msg -> ExceptT (ProtocolClientError err) IO msg
+sendProtocolCommand_ c@ProtocolClient {client_ = PClient {sndQ}, thParams = THandleParams {batch, blockSize}} nonce_ tOut pKey entId cmd =
+  ExceptT $ uncurry sendRecv =<< mkTransmission_ c nonce_ (pKey, entId, cmd)
   where
     -- two separate "atomically" needed to avoid blocking
     sendRecv :: Either TransportError SentRawTransmission -> Request err msg -> IO (Either (ProtocolClientError err) msg)
@@ -748,15 +973,15 @@ sendProtocolCommand c@ProtocolClient {client_ = PClient {sndQ}, thParams = THand
         | B.length s > blockSize - 2 -> pure . Left $ PCETransportError TELargeMsg
         | otherwise -> do
             atomically $ writeTBQueue sndQ s
-            response <$> getResponse c r
+            response <$> getResponse c tOut r
         where
           s
             | batch = tEncodeBatch1 t
             | otherwise = tEncode t
 
-getResponse :: ProtocolClient v err msg -> Request err msg -> IO (Response err msg)
-getResponse ProtocolClient {client_ = PClient {tcpTimeout, timeoutErrorCount}} Request {entityId, pending, responseVar} = do
-  r <- tcpTimeout `timeout` atomically (takeTMVar responseVar)
+getResponse :: ProtocolClient v err msg -> Maybe Int -> Request err msg -> IO (Response err msg)
+getResponse ProtocolClient {client_ = PClient {tcpTimeout, timeoutErrorCount}} tOut Request {entityId, pending, responseVar} = do
+  r <- fromMaybe tcpTimeout tOut `timeout` atomically (takeTMVar responseVar)
   response <- atomically $ do
     writeTVar pending False
     -- Try to read response again in case it arrived after timeout expired
@@ -767,16 +992,17 @@ getResponse ProtocolClient {client_ = PClient {tcpTimeout, timeoutErrorCount}} R
       Nothing -> modifyTVar' timeoutErrorCount (+ 1) $> Left PCEResponseTimeout
   pure Response {entityId, response}
 
-mkTransmission :: forall v err msg. Protocol v err msg => ProtocolClient v err msg -> ClientCommand msg -> IO (PCTransmission err msg)
-mkTransmission ProtocolClient {thParams, client_ = PClient {clientCorrId, sentCommands}} (pKey_, entityId, command) = do
-  corrId <- atomically getNextCorrId
-  let TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth thParams (corrId, entityId, command)
-      auth = authTransmission (thAuth thParams) pKey_ corrId tForAuth
-  r <- atomically $ mkRequest corrId
+mkTransmission :: Protocol v err msg => ProtocolClient v err msg -> ClientCommand msg -> IO (PCTransmission err msg)
+mkTransmission c = mkTransmission_ c Nothing
+
+mkTransmission_ :: forall v err msg. Protocol v err msg => ProtocolClient v err msg -> Maybe C.CbNonce -> ClientCommand msg -> IO (PCTransmission err msg)
+mkTransmission_ ProtocolClient {thParams, client_ = PClient {clientCorrId, sentCommands}} nonce_ (pKey_, entityId, command) = do
+  nonce@(C.CbNonce corrId) <- maybe (atomically $ C.randomCbNonce clientCorrId) pure nonce_
+  let TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth thParams (CorrId corrId, entityId, command)
+      auth = authTransmission (thAuth thParams) pKey_ nonce tForAuth
+  r <- atomically $ mkRequest (CorrId corrId)
   pure ((,tToSend) <$> auth, r)
   where
-    getNextCorrId :: STM CorrId
-    getNextCorrId = CorrId <$> C.randomBytes 24 clientCorrId -- also used as nonce
     mkRequest :: CorrId -> STM (Request err msg)
     mkRequest corrId = do
       pending <- newTVar True
@@ -792,13 +1018,13 @@ mkTransmission ProtocolClient {thParams, client_ = PClient {clientCorrId, sentCo
       TM.insert corrId r sentCommands
       pure r
 
-authTransmission :: Maybe (THandleAuth 'TClient) -> Maybe C.APrivateAuthKey -> CorrId -> ByteString -> Either TransportError (Maybe TransmissionAuth)
-authTransmission thAuth pKey_ (CorrId corrId) t = traverse authenticate pKey_
+authTransmission :: Maybe (THandleAuth 'TClient) -> Maybe C.APrivateAuthKey -> C.CbNonce -> ByteString -> Either TransportError (Maybe TransmissionAuth)
+authTransmission thAuth pKey_ nonce t = traverse authenticate pKey_
   where
     authenticate :: C.APrivateAuthKey -> Either TransportError TransmissionAuth
     authenticate (C.APrivateAuthKey a pk) = case a of
       C.SX25519 -> case thAuth of
-        Just THAuthClient {serverPeerPubKey = k} -> Right $ TAAuthenticator $ C.cbAuthenticate k pk (C.cbNonce corrId) t
+        Just THAuthClient {serverPeerPubKey = k} -> Right $ TAAuthenticator $ C.cbAuthenticate k pk nonce t
         Nothing -> Left TENoServerAuth
       C.SEd25519 -> sign pk
       C.SEd448 -> sign pk
@@ -807,6 +1033,14 @@ authTransmission thAuth pKey_ (CorrId corrId) t = traverse authenticate pKey_
 
 $(J.deriveJSON (enumJSON $ dropPrefix "HM") ''HostMode)
 
+$(J.deriveJSON (enumJSON $ dropPrefix "SM") ''SocksMode)
+
 $(J.deriveJSON (enumJSON $ dropPrefix "TSM") ''TransportSessionMode)
 
+$(J.deriveJSON (enumJSON $ dropPrefix "SPM") ''SMPProxyMode)
+
+$(J.deriveJSON (enumJSON $ dropPrefix "SPF") ''SMPProxyFallback)
+
 $(J.deriveJSON defaultJSON ''NetworkConfig)
+
+$(J.deriveJSON (enumJSON $ dropPrefix "Proxy") ''ProxyClientError)
diff --git a/src/Simplex/Messaging/Client/Agent.hs b/src/Simplex/Messaging/Client/Agent.hs
index aed56f1bd..d32d59b3f 100644
--- a/src/Simplex/Messaging/Client/Agent.hs
+++ b/src/Simplex/Messaging/Client/Agent.hs
@@ -98,6 +98,7 @@ data SMPClientAgent = SMPClientAgent
     agentQ :: TBQueue SMPClientAgentEvent,
     randomDrg :: TVar ChaChaDRG,
     smpClients :: TMap SMPServer SMPClientVar,
+    smpSessions :: TMap SessionId SMPClient,
     srvSubs :: TMap SMPServer (TMap SMPSub C.APrivateAuthKey),
     pendingSrvSubs :: TMap SMPServer (TMap SMPSub C.APrivateAuthKey),
     reconnections :: TVar [Async ()],
@@ -135,6 +136,7 @@ newSMPClientAgent agentCfg@SMPClientAgentConfig {msgQSize, agentQSize} randomDrg
   msgQ <- newTBQueue msgQSize
   agentQ <- newTBQueue agentQSize
   smpClients <- TM.empty
+  smpSessions <- TM.empty
   srvSubs <- TM.empty
   pendingSrvSubs <- TM.empty
   reconnections <- newTVar []
@@ -147,6 +149,7 @@ newSMPClientAgent agentCfg@SMPClientAgentConfig {msgQSize, agentQSize} randomDrg
         agentQ,
         randomDrg,
         smpClients,
+        smpSessions,
         srvSubs,
         pendingSrvSubs,
         reconnections,
@@ -155,7 +158,7 @@ newSMPClientAgent agentCfg@SMPClientAgentConfig {msgQSize, agentQSize} randomDrg
       }
 
 getSMPServerClient' :: SMPClientAgent -> SMPServer -> ExceptT SMPClientError IO SMPClient
-getSMPServerClient' ca@SMPClientAgent {agentCfg, smpClients, msgQ, randomDrg, workerSeq} srv =
+getSMPServerClient' ca@SMPClientAgent {agentCfg, smpClients, smpSessions, msgQ, randomDrg, workerSeq} srv =
   atomically getClientVar >>= either newSMPClient waitForSMPClient
   where
     getClientVar :: STM (Either SMPClientVar SMPClientVar)
@@ -178,7 +181,9 @@ getSMPServerClient' ca@SMPClientAgent {agentCfg, smpClients, msgQ, randomDrg, wo
           tryE (connectClient v) >>= \r -> case r of
             Right smp -> do
               logInfo . decodeUtf8 $ "Agent connected to " <> showServer srv
-              atomically $ putTMVar (sessionVar v) r
+              atomically $ do
+                putTMVar (sessionVar v) r
+                TM.insert (sessionId $ thParams smp) smp smpSessions
               successAction smp
             Left e -> do
               if e == PCENetworkError || e == PCEResponseTimeout
@@ -200,13 +205,14 @@ getSMPServerClient' ca@SMPClientAgent {agentCfg, smpClients, msgQ, randomDrg, wo
     connectClient v = ExceptT $ getProtocolClient randomDrg (1, srv, Nothing) (smpCfg agentCfg) (Just msgQ) (clientDisconnected v)
 
     clientDisconnected :: SMPClientVar -> SMPClient -> IO ()
-    clientDisconnected v _ = do
-      removeClientAndSubs v >>= (`forM_` serverDown)
+    clientDisconnected v smp = do
+      removeClientAndSubs v smp >>= (`forM_` serverDown)
       logInfo . decodeUtf8 $ "Agent disconnected from " <> showServer srv
 
-    removeClientAndSubs :: SMPClientVar -> IO (Maybe (Map SMPSub C.APrivateAuthKey))
-    removeClientAndSubs v = atomically $ do
+    removeClientAndSubs :: SMPClientVar -> SMPClient -> IO (Maybe (Map SMPSub C.APrivateAuthKey))
+    removeClientAndSubs v smp = atomically $ do
       removeSessVar v srv smpClients
+      TM.delete (sessionId $ thParams smp) smpSessions
       TM.lookupDelete srv (srvSubs ca) >>= mapM updateSubs
       where
         updateSubs sVar = do
@@ -271,6 +277,9 @@ getSMPServerClient' ca@SMPClientAgent {agentCfg, smpClients, msgQ, randomDrg, wo
     notify :: SMPClientAgentEvent -> IO ()
     notify evt = atomically $ writeTBQueue (agentQ ca) evt
 
+lookupSMPServerClient :: SMPClientAgent -> SessionId -> STM (Maybe SMPClient)
+lookupSMPServerClient SMPClientAgent {smpSessions} sessId = TM.lookup sessId smpSessions
+
 closeSMPClientAgent :: SMPClientAgent -> IO ()
 closeSMPClientAgent c = do
   closeSMPServerClients c
diff --git a/src/Simplex/Messaging/Crypto.hs b/src/Simplex/Messaging/Crypto.hs
index 28183a1fc..7aefbd709 100644
--- a/src/Simplex/Messaging/Crypto.hs
+++ b/src/Simplex/Messaging/Crypto.hs
@@ -141,6 +141,7 @@ module Simplex.Messaging.Crypto
     sbEncrypt_,
     cbNonce,
     randomCbNonce,
+    reverseNonce,
 
     -- * NaCl crypto_secretbox
     SbKey (unSbKey),
@@ -756,6 +757,8 @@ data Signature (a :: Algorithm) where
   SignatureEd25519 :: Ed25519.Signature -> Signature Ed25519
   SignatureEd448 :: Ed448.Signature -> Signature Ed448
 
+deriving instance Eq (Signature a)
+
 deriving instance Show (Signature a)
 
 data ASignature
@@ -1290,6 +1293,9 @@ randomCbNonce = fmap CryptoBoxNonce . randomBytes 24
 randomBytes :: Int -> TVar ChaChaDRG -> STM ByteString
 randomBytes n gVar = stateTVar gVar $ randomBytesGenerate n
 
+reverseNonce :: CbNonce -> CbNonce
+reverseNonce (CryptoBoxNonce s) = CryptoBoxNonce (B.reverse s)
+
 instance Encoding CbNonce where
   smpEncode = unCbNonce
   smpP = CryptoBoxNonce <$> A.take 24
diff --git a/src/Simplex/Messaging/Crypto/Ratchet.hs b/src/Simplex/Messaging/Crypto/Ratchet.hs
index 6ab84aa30..db13fddc1 100644
--- a/src/Simplex/Messaging/Crypto/Ratchet.hs
+++ b/src/Simplex/Messaging/Crypto/Ratchet.hs
@@ -117,7 +117,7 @@ import Simplex.Messaging.Crypto.SNTRUP761.Bindings
 import Simplex.Messaging.Encoding
 import Simplex.Messaging.Encoding.String
 import Simplex.Messaging.Parsers (blobFieldDecoder, defaultJSON, parseE, parseE')
-import Simplex.Messaging.Util ((<$?>), ($>>=))
+import Simplex.Messaging.Util (($>>=), (<$?>))
 import Simplex.Messaging.Version
 import Simplex.Messaging.Version.Internal
 import UnliftIO.STM
@@ -266,6 +266,7 @@ instance VersionRangeI E2EVersion (E2ERatchetParamsUri s a) where
   type VersionT E2EVersion (E2ERatchetParamsUri s a) = (E2ERatchetParams s a)
   versionRange (E2ERatchetParamsUri vr _ _ _) = vr
   toVersionT (E2ERatchetParamsUri _ k1 k2 kem_) v = E2ERatchetParams v k1 k2 kem_
+  toVersionRange (E2ERatchetParamsUri _ k1 k2 kem_) vr = E2ERatchetParamsUri vr k1 k2 kem_
 
 type RcvE2ERatchetParamsUri a = E2ERatchetParamsUri 'RKSProposed a
 
@@ -377,13 +378,15 @@ generateE2EParams g v useKEM_ = do
   where
     kemParams :: IO (Maybe (RKEMParams s, PrivRKEMParams s))
     kemParams = case useKEM_ of
-      Just useKem | v >= pqRatchetE2EEncryptVersion -> Just <$> do
-        ks@(k, _) <- sntrup761Keypair g
-        case useKem of
-          ProposeKEM -> pure (RKParamsProposed k, PrivateRKParamsProposed ks)
-          AcceptKEM k' -> do
-            (ct, shared) <- sntrup761Enc g k'
-            pure (RKParamsAccepted ct k, PrivateRKParamsAccepted ct shared ks)
+      Just useKem
+        | v >= pqRatchetE2EEncryptVersion ->
+            Just <$> do
+              ks@(k, _) <- sntrup761Keypair g
+              case useKem of
+                ProposeKEM -> pure (RKParamsProposed k, PrivateRKParamsProposed ks)
+                AcceptKEM k' -> do
+                  (ct, shared) <- sntrup761Enc g k'
+                  pure (RKParamsAccepted ct k, PrivateRKParamsAccepted ct shared ks)
       _ -> pure Nothing
 
 -- used by party initiating connection, Bob in double-ratchet spec
@@ -456,7 +459,7 @@ pqX3dh (sk1, rk1) dh1 dh2 dh3 kemAccepted =
     pq = maybe "" (\RatchetKEMAccepted {rcPQRss = KEMSharedKey ss} -> BA.convert ss) kemAccepted
     (hk, nhk, sk) =
       let salt = B.replicate 64 '\0'
-        in hkdf3 salt dhs "SimpleXX3DH"
+       in hkdf3 salt dhs "SimpleXX3DH"
 
 type RatchetX448 = Ratchet 'X448
 
@@ -698,8 +701,8 @@ data EncMessageHeader = EncMessageHeader
 
 -- this encoding depends on version in EncMessageHeader because it is "current" ratchet version
 instance Encoding EncMessageHeader where
-  smpEncode EncMessageHeader {ehVersion, ehIV, ehAuthTag, ehBody}
-    = smpEncode (ehVersion, ehIV, ehAuthTag) <> encodeLarge ehVersion ehBody
+  smpEncode EncMessageHeader {ehVersion, ehIV, ehAuthTag, ehBody} =
+    smpEncode (ehVersion, ehIV, ehAuthTag) <> encodeLarge ehVersion ehBody
   smpP = do
     (ehVersion, ehIV, ehAuthTag) <- smpP
     ehBody <- largeP
@@ -708,8 +711,6 @@ instance Encoding EncMessageHeader where
 -- the encoder always uses 2-byte lengths for the new version, even for short headers without PQ keys.
 encodeLarge :: VersionE2E -> ByteString -> ByteString
 encodeLarge v s
-  -- the condition for length is not necessary, it's here as a fallback.
-  -- | v >= pqRatchetE2EEncryptVersion || B.length s > 255 = smpEncode $ Large s
   | v >= pqRatchetE2EEncryptVersion = smpEncode $ Large s
   | otherwise = smpEncode s
 
@@ -729,8 +730,8 @@ data EncRatchetMessage = EncRatchetMessage
   }
 
 encodeEncRatchetMessage :: VersionE2E -> EncRatchetMessage -> ByteString
-encodeEncRatchetMessage v EncRatchetMessage {emHeader, emBody, emAuthTag}
-  = encodeLarge v emHeader <> smpEncode (emAuthTag, Tail emBody)
+encodeEncRatchetMessage v EncRatchetMessage {emHeader, emBody, emAuthTag} =
+  encodeLarge v emHeader <> smpEncode (emAuthTag, Tail emBody)
 
 encRatchetMessageP :: Parser EncRatchetMessage
 encRatchetMessageP = do
diff --git a/src/Simplex/Messaging/Encoding/String.hs b/src/Simplex/Messaging/Encoding/String.hs
index fcefdc73d..6b9fb5624 100644
--- a/src/Simplex/Messaging/Encoding/String.hs
+++ b/src/Simplex/Messaging/Encoding/String.hs
@@ -75,6 +75,8 @@ instance StrEncoding Str where
   strEncode = unStr
   strP = Str <$> A.takeTill (== ' ') <* optional A.space
 
+-- inherited from ByteString, the parser only allows non-empty strings
+-- only Char8 elements may round-trip as B.pack truncates unicode
 instance StrEncoding String where
   strEncode = strEncode . B.pack
   strP = B.unpack <$> strP
diff --git a/src/Simplex/Messaging/Notifications/Transport.hs b/src/Simplex/Messaging/Notifications/Transport.hs
index 58391c225..077ce634e 100644
--- a/src/Simplex/Messaging/Notifications/Transport.hs
+++ b/src/Simplex/Messaging/Notifications/Transport.hs
@@ -11,6 +11,7 @@ module Simplex.Messaging.Notifications.Transport where
 
 import Control.Monad (forM)
 import Control.Monad.Except
+import Control.Monad.Trans.Except
 import Data.Attoparsec.ByteString.Char8 (Parser)
 import Data.ByteString.Char8 (ByteString)
 import qualified Data.ByteString.Char8 as B
@@ -116,9 +117,10 @@ ntfServerHandshake serverSignKey c (k, pk) kh ntfVRange = do
     NtfClientHandshake {ntfVersion = v, keyHash}
       | keyHash /= kh ->
           throwError $ TEHandshake IDENTITY
-      | v `isCompatible` ntfVersionRange ->
-          pure $ ntfThHandleServer th v pk
-      | otherwise -> throwError $ TEHandshake VERSION
+      | otherwise ->
+          case compatibleVRange' ntfVersionRange v of
+            Just (Compatible vr) -> pure $ ntfThHandleServer th v vr pk
+            Nothing -> throwE TEVersion
 
 -- | Notifcations server client transport handshake.
 ntfClientHandshake :: forall c. Transport c => c -> C.KeyHash -> VersionRangeNTF -> ExceptT TransportError IO (THandleNTF c 'TClient)
@@ -127,34 +129,45 @@ ntfClientHandshake c keyHash ntfVRange = do
   NtfServerHandshake {sessionId = sessId, ntfVersionRange, authPubKey = sk'} <- getHandshake th
   if sessionId /= sessId
     then throwError TEBadSession
-    else case ntfVersionRange `compatibleVersion` ntfVRange of
-      Just (Compatible v) -> do
+    else case ntfVersionRange `compatibleVRange` ntfVRange of
+      Just (Compatible vr) -> do
         ck_ <- forM sk' $ \signedKey -> liftEitherWith (const $ TEHandshake BAD_AUTH) $ do
           serverKey <- getServerVerifyKey c
           pubKey <- C.verifyX509 serverKey signedKey
           (,(getServerCerts c, signedKey)) <$> (C.x509ToPublic (pubKey, []) >>= C.pubKey)
+        let v = maxVersion vr
         sendHandshake th $ NtfClientHandshake {ntfVersion = v, keyHash}
-        pure $ ntfThHandleClient th v ck_
-      Nothing -> throwError $ TEHandshake VERSION
+        pure $ ntfThHandleClient th v vr ck_
+      Nothing -> throwE TEVersion
 
-ntfThHandleServer :: forall c. THandleNTF c 'TServer -> VersionNTF -> C.PrivateKeyX25519 -> THandleNTF c 'TServer
-ntfThHandleServer th v pk =
+ntfThHandleServer :: forall c. THandleNTF c 'TServer -> VersionNTF -> VersionRangeNTF -> C.PrivateKeyX25519 -> THandleNTF c 'TServer
+ntfThHandleServer th v vr pk =
   let thAuth = THAuthServer {serverPrivKey = pk, sessSecret' = Nothing}
-   in ntfThHandle_ th v (Just thAuth)
+   in ntfThHandle_ th v vr (Just thAuth)
 
-ntfThHandleClient :: forall c. THandleNTF c 'TClient -> VersionNTF -> Maybe (C.PublicKeyX25519, (X.CertificateChain, X.SignedExact X.PubKey)) -> THandleNTF c 'TClient
-ntfThHandleClient th v ck_ =
+ntfThHandleClient :: forall c. THandleNTF c 'TClient -> VersionNTF -> VersionRangeNTF -> Maybe (C.PublicKeyX25519, (X.CertificateChain, X.SignedExact X.PubKey)) -> THandleNTF c 'TClient
+ntfThHandleClient th v vr ck_ =
   let thAuth = (\(k, ck) -> THAuthClient {serverPeerPubKey = k, serverCertKey = ck, sessSecret = Nothing}) <$> ck_
-   in ntfThHandle_ th v thAuth
+   in ntfThHandle_ th v vr thAuth
 
-ntfThHandle_ :: forall c p. THandleNTF c p -> VersionNTF -> Maybe (THandleAuth p) -> THandleNTF c p
-ntfThHandle_ th@THandle {params} v thAuth =
+ntfThHandle_ :: forall c p. THandleNTF c p -> VersionNTF -> VersionRangeNTF -> Maybe (THandleAuth p) -> THandleNTF c p
+ntfThHandle_ th@THandle {params} v vr thAuth =
   -- TODO drop SMP v6: make thAuth non-optional
   let v3 = v >= authBatchCmdsNTFVersion
-      params' = params {thVersion = v, thAuth, implySessId = v3, batch = v3}
+      params' = params {thVersion = v, thServerVRange = vr, thAuth, implySessId = v3, batch = v3}
    in (th :: THandleNTF c p) {params = params'}
 
 ntfTHandle :: Transport c => c -> THandleNTF c p
 ntfTHandle c = THandle {connection = c, params}
   where
-    params = THandleParams {sessionId = tlsUnique c, blockSize = ntfBlockSize, thVersion = VersionNTF 0, thAuth = Nothing, implySessId = False, batch = False}
+    v = VersionNTF 0
+    params =
+      THandleParams
+        { sessionId = tlsUnique c,
+          blockSize = ntfBlockSize,
+          thVersion = v,
+          thServerVRange = versionToRange v,
+          thAuth = Nothing,
+          implySessId = False,
+          batch = False
+        }
diff --git a/src/Simplex/Messaging/Protocol.hs b/src/Simplex/Messaging/Protocol.hs
index 1dc76dbab..1812dce37 100644
--- a/src/Simplex/Messaging/Protocol.hs
+++ b/src/Simplex/Messaging/Protocol.hs
@@ -43,6 +43,7 @@ module Simplex.Messaging.Protocol
   ( -- * SMP protocol parameters
     supportedSMPClientVRange,
     maxMessageLength,
+    paddedProxiedMsgLength,
     e2eEncConfirmationLength,
     e2eEncMessageLength,
 
@@ -56,6 +57,7 @@ module Simplex.Messaging.Protocol
     SubscriptionMode (..),
     Party (..),
     Cmd (..),
+    DirectParty,
     BrokerMsg (..),
     SParty (..),
     PartyI (..),
@@ -63,6 +65,8 @@ module Simplex.Messaging.Protocol
     ProtocolErrorType (..),
     ErrorType (..),
     CommandError (..),
+    ProxyError (..),
+    BrokerErrorType (..),
     Transmission,
     TransmissionAuth (..),
     SignedTransmission,
@@ -121,6 +125,12 @@ module Simplex.Messaging.Protocol
     EncNMsgMeta,
     SMPMsgMeta (..),
     NMsgMeta (..),
+    EncFwdResponse (..),
+    EncFwdTransmission (..),
+    EncResponse (..),
+    EncTransmission (..),
+    FwdResponse (..),
+    FwdTransmission (..),
     MsgFlags (..),
     initialSMPClientVersion,
     userProtocol,
@@ -167,6 +177,7 @@ module Simplex.Messaging.Protocol
 where
 
 import Control.Applicative (optional, (<|>))
+import Control.Exception (Exception)
 import Control.Monad
 import Control.Monad.Except
 import Data.Aeson (FromJSON (..), ToJSON (..))
@@ -185,10 +196,15 @@ import Data.List.NonEmpty (NonEmpty (..))
 import qualified Data.List.NonEmpty as L
 import Data.Maybe (isJust, isNothing)
 import Data.String
+import qualified Data.Text as T
+import Data.Text.Encoding (encodeUtf8)
 import Data.Time.Clock.System (SystemTime (..))
 import Data.Type.Equality
 import Data.Word (Word16)
+import qualified Data.X509 as X
 import GHC.TypeLits (ErrorMessage (..), TypeError, type (+))
+import qualified GHC.TypeLits as TE
+import qualified GHC.TypeLits as Type
 import Network.Socket (ServiceName)
 import qualified Simplex.Messaging.Crypto as C
 import Simplex.Messaging.Encoding
@@ -197,7 +213,7 @@ import Simplex.Messaging.Parsers
 import Simplex.Messaging.ServiceScheme
 import Simplex.Messaging.Transport
 import Simplex.Messaging.Transport.Client (TransportHost, TransportHosts (..))
-import Simplex.Messaging.Util (bshow, eitherToMaybe, (<$?>))
+import Simplex.Messaging.Util (bshow, eitherToMaybe, safeDecodeUtf8, (<$?>))
 import Simplex.Messaging.Version
 import Simplex.Messaging.Version.Internal
 
@@ -228,9 +244,16 @@ currentSMPClientVersion = VersionSMPC 2
 supportedSMPClientVRange :: VersionRangeSMPC
 supportedSMPClientVRange = mkVersionRange initialSMPClientVersion currentSMPClientVersion
 
-maxMessageLength :: Int
-maxMessageLength = 16088
+-- TODO v6.0 remove dependency on version
+maxMessageLength :: VersionSMP -> Int
+maxMessageLength v
+  | v >= sendingProxySMPVersion = 16064 -- max 16067
+  | otherwise = 16088 -- 16064 - always use this size to determine allowed ranges
 
+paddedProxiedMsgLength :: Int
+paddedProxiedMsgLength = 16242 -- 16241 .. 16243
+
+-- TODO v6.0 change to 16064
 type MaxMessageLen = 16088
 
 -- 16 extra bytes: 8 for timestamp and 8 for flags (7 flags and the space, only 1 flag is currently used)
@@ -244,7 +267,7 @@ e2eEncMessageLength :: Int
 e2eEncMessageLength = 16016 -- 16004 .. 16021
 
 -- | SMP protocol clients
-data Party = Recipient | Sender | Notifier
+data Party = Recipient | Sender | Notifier | ProxiedClient
   deriving (Show)
 
 -- | Singleton types for SMP protocol clients
@@ -252,11 +275,13 @@ data SParty :: Party -> Type where
   SRecipient :: SParty Recipient
   SSender :: SParty Sender
   SNotifier :: SParty Notifier
+  SProxiedClient :: SParty ProxiedClient
 
 instance TestEquality SParty where
   testEquality SRecipient SRecipient = Just Refl
   testEquality SSender SSender = Just Refl
   testEquality SNotifier SNotifier = Just Refl
+  testEquality SProxiedClient SProxiedClient = Just Refl
   testEquality _ _ = Nothing
 
 deriving instance Show (SParty p)
@@ -269,6 +294,15 @@ instance PartyI Sender where sParty = SSender
 
 instance PartyI Notifier where sParty = SNotifier
 
+instance PartyI ProxiedClient where sParty = SProxiedClient
+
+type family DirectParty (p :: Party) :: Constraint where
+  DirectParty Recipient = ()
+  DirectParty Sender = ()
+  DirectParty Notifier = ()
+  DirectParty p =
+    (Int ~ Bool, TypeError (Type.Text "Party " :<>: ShowType p :<>: Type.Text " is not direct"))
+
 -- | Type for client command of any participant.
 data Cmd = forall p. PartyI p => Cmd (SParty p) (Command p)
 
@@ -359,6 +393,17 @@ data Command (p :: Party) where
   PING :: Command Sender
   -- SMP notification subscriber commands
   NSUB :: Command Notifier
+  PRXY :: SMPServer -> Maybe BasicAuth -> Command ProxiedClient -- request a relay server connection by URI
+  -- Transmission to proxy:
+  -- - entity ID: ID of the session with relay returned in PKEY (response to PRXY)
+  -- - corrId: also used as a nonce to encrypt transmission to relay, corrId + 1 - from relay
+  -- - key (1st param in the command) is used to agree DH secret for this particular transmission and its response
+  -- Encrypted transmission should include session ID (tlsunique) from proxy-relay connection.
+  PFWD :: VersionSMP -> C.PublicKeyX25519 -> EncTransmission -> Command ProxiedClient -- use CorrId as CbNonce, client to proxy
+  -- Transmission forwarded to relay:
+  -- - entity ID: empty
+  -- - corrId: unique correlation ID between proxy and relay, also used as a nonce to encrypt forwarded transmission
+  RFWD :: EncFwdTransmission -> Command Sender -- use CorrId as CbNonce, proxy to relay
 
 deriving instance Show (Command p)
 
@@ -384,6 +429,26 @@ instance Encoding SubscriptionMode where
       'C' -> pure SMOnlyCreate
       _ -> fail "bad SubscriptionMode"
 
+newtype EncTransmission = EncTransmission ByteString
+  deriving (Show)
+
+data FwdTransmission = FwdTransmission
+  { fwdCorrId :: CorrId,
+    fwdVersion :: VersionSMP,
+    fwdKey :: C.PublicKeyX25519,
+    fwdTransmission :: EncTransmission
+  }
+
+instance Encoding FwdTransmission where
+  smpEncode FwdTransmission {fwdCorrId = CorrId corrId, fwdVersion, fwdKey, fwdTransmission = EncTransmission t} =
+    smpEncode (corrId, fwdVersion, fwdKey, Tail t)
+  smpP = do
+    (corrId, fwdVersion, fwdKey, Tail t) <- smpP
+    pure FwdTransmission {fwdCorrId = CorrId corrId, fwdVersion, fwdKey, fwdTransmission = EncTransmission t}
+
+newtype EncFwdTransmission = EncFwdTransmission ByteString
+  deriving (Show)
+
 data BrokerMsg where
   -- SMP broker messages (responses, client messages, notifications)
   IDS :: QueueIdsKeys -> BrokerMsg
@@ -393,6 +458,10 @@ data BrokerMsg where
   MSG :: RcvMessage -> BrokerMsg
   NID :: NotifierId -> RcvNtfPublicDhKey -> BrokerMsg
   NMSG :: C.CbNonce -> EncNMsgMeta -> BrokerMsg
+  -- Should include certificate chain
+  PKEY :: SessionId -> VersionRangeSMP -> (X.CertificateChain, X.SignedExact X.PubKey) -> BrokerMsg -- TLS-signed server key for proxy shared secret and initial sender key
+  RRES :: EncFwdResponse -> BrokerMsg -- relay to proxy
+  PRES :: EncResponse -> BrokerMsg -- proxy to client
   END :: BrokerMsg
   OK :: BrokerMsg
   ERR :: ErrorType -> BrokerMsg
@@ -405,6 +474,24 @@ data RcvMessage = RcvMessage
   }
   deriving (Eq, Show)
 
+newtype EncFwdResponse = EncFwdResponse ByteString
+  deriving (Eq, Show)
+
+data FwdResponse = FwdResponse
+  { fwdCorrId :: CorrId,
+    fwdResponse :: EncResponse
+  }
+
+instance Encoding FwdResponse where
+  smpEncode FwdResponse {fwdCorrId = CorrId corrId, fwdResponse = EncResponse t} =
+    smpEncode (corrId, Tail t)
+  smpP = do
+    (corrId, Tail t) <- smpP
+    pure FwdResponse {fwdCorrId = CorrId corrId, fwdResponse = EncResponse t}
+
+newtype EncResponse = EncResponse ByteString
+  deriving (Eq, Show)
+
 -- | received message without server/recipient encryption
 data Message
   = Message
@@ -567,6 +654,9 @@ data CommandTag (p :: Party) where
   DEL_ :: CommandTag Recipient
   SEND_ :: CommandTag Sender
   PING_ :: CommandTag Sender
+  PRXY_ :: CommandTag ProxiedClient
+  PFWD_ :: CommandTag ProxiedClient
+  RFWD_ :: CommandTag Sender
   NSUB_ :: CommandTag Notifier
 
 data CmdTag = forall p. PartyI p => CT (SParty p) (CommandTag p)
@@ -580,6 +670,9 @@ data BrokerMsgTag
   | MSG_
   | NID_
   | NMSG_
+  | PKEY_
+  | RRES_
+  | PRES_
   | END_
   | OK_
   | ERR_
@@ -607,6 +700,9 @@ instance PartyI p => Encoding (CommandTag p) where
     DEL_ -> "DEL"
     SEND_ -> "SEND"
     PING_ -> "PING"
+    PRXY_ -> "PRXY"
+    PFWD_ -> "PFWD"
+    RFWD_ -> "RFWD"
     NSUB_ -> "NSUB"
   smpP = messageTagP
 
@@ -623,6 +719,9 @@ instance ProtocolMsgTag CmdTag where
     "DEL" -> Just $ CT SRecipient DEL_
     "SEND" -> Just $ CT SSender SEND_
     "PING" -> Just $ CT SSender PING_
+    "PRXY" -> Just $ CT SProxiedClient PRXY_
+    "PFWD" -> Just $ CT SProxiedClient PFWD_
+    "RFWD" -> Just $ CT SSender RFWD_
     "NSUB" -> Just $ CT SNotifier NSUB_
     _ -> Nothing
 
@@ -639,6 +738,9 @@ instance Encoding BrokerMsgTag where
     MSG_ -> "MSG"
     NID_ -> "NID"
     NMSG_ -> "NMSG"
+    PKEY_ -> "PKEY"
+    RRES_ -> "RRES"
+    PRES_ -> "PRES"
     END_ -> "END"
     OK_ -> "OK"
     ERR_ -> "ERR"
@@ -651,6 +753,9 @@ instance ProtocolMsgTag BrokerMsgTag where
     "MSG" -> Just MSG_
     "NID" -> Just NID_
     "NMSG" -> Just NMSG_
+    "PKEY" -> Just PKEY_
+    "RRES" -> Just RRES_
+    "PRES" -> Just PRES_
     "END" -> Just END_
     "OK" -> Just OK_
     "ERR" -> Just ERR_
@@ -829,7 +934,7 @@ type family UserProtocol (p :: ProtocolType) :: Constraint where
   UserProtocol PSMP = ()
   UserProtocol PXFTP = ()
   UserProtocol a =
-    (Int ~ Bool, TypeError (Text "Servers for protocol " :<>: ShowType a :<>: Text " cannot be configured by the users"))
+    (Int ~ Bool, TypeError (TE.Text "Servers for protocol " :<>: ShowType a :<>: TE.Text " cannot be configured by the users"))
 
 userProtocol :: SProtocolType p -> Maybe (Dict (UserProtocol p))
 userProtocol = \case
@@ -1038,14 +1143,20 @@ data ErrorType
     SESSION
   | -- | SMP command is unknown or has invalid syntax
     CMD {cmdErr :: CommandError}
+  | -- | error from proxied relay
+    PROXY {proxyErr :: ProxyError}
   | -- | command authorization error - bad signature or non-existing SMP queue
     AUTH
+  | -- | encryption/decryption error in proxy protocol
+    CRYPTO
   | -- | SMP queue capacity is exceeded on the server
     QUOTA
   | -- | ACK command is sent without message to be acknowledged
     NO_MSG
   | -- | sent message is too large (> maxMessageLength = 16088 bytes)
     LARGE_MSG
+  | -- | relay public key is expired
+    EXPIRED
   | -- | internal server error
     INTERNAL
   | -- | used internally, never returned by the server (to be removed)
@@ -1055,8 +1166,12 @@ data ErrorType
 instance StrEncoding ErrorType where
   strEncode = \case
     CMD e -> "CMD " <> bshow e
+    PROXY e -> "PROXY " <> strEncode e
     e -> bshow e
-  strP = "CMD " *> (CMD <$> parseRead1) <|> parseRead1
+  strP =
+    "CMD " *> (CMD <$> parseRead1)
+      <|> "PROXY " *> (PROXY <$> strP)
+      <|> parseRead1
 
 -- | SMP command error type.
 data CommandError
@@ -1074,6 +1189,34 @@ data CommandError
     NO_ENTITY
   deriving (Eq, Read, Show)
 
+data ProxyError
+  = -- | Correctly parsed SMP server ERR response.
+    -- This error is forwarded to the agent client as AgentErrorType `ERR PROXY PROTOCOL err`.
+    PROTOCOL {protocolErr :: ErrorType}
+  | -- | destination server error
+    BROKER {brokerErr :: BrokerErrorType}
+  | -- | basic auth provided to proxy is invalid
+    BASIC_AUTH
+  | -- no destination server error
+    NO_SESSION
+  deriving (Eq, Read, Show)
+
+-- | SMP server errors.
+data BrokerErrorType
+  = -- | invalid server response (failed to parse)
+    RESPONSE {respErr :: String}
+  | -- | unexpected response
+    UNEXPECTED {respErr :: String}
+  | -- | network error
+    NETWORK
+  | -- | no compatible server host (e.g. onion when public is required, or vice versa)
+    HOST
+  | -- | handshake or other transport error
+    TRANSPORT {transportErr :: TransportError}
+  | -- | command response timeout
+    TIMEOUT
+  deriving (Eq, Read, Show, Exception)
+
 -- | SMP transmission parser.
 transmissionP :: THandleParams v p -> Parser RawTransmission
 transmissionP THandleParams {sessionId, implySessId} = do
@@ -1135,6 +1278,9 @@ instance PartyI p => ProtocolEncoding SMPVersion ErrorType (Command p) where
     SEND flags msg -> e (SEND_, ' ', flags, ' ', Tail msg)
     PING -> e PING_
     NSUB -> e NSUB_
+    PRXY host auth_ -> e (PRXY_, ' ', host, auth_)
+    PFWD fwdV pubKey (EncTransmission s) -> e (PFWD_, ' ', fwdV, pubKey, Tail s)
+    RFWD (EncFwdTransmission s) -> e (RFWD_, ' ', Tail s)
     where
       e :: Encoding a => a -> ByteString
       e = smpEncode
@@ -1144,24 +1290,33 @@ instance PartyI p => ProtocolEncoding SMPVersion ErrorType (Command p) where
   fromProtocolError = fromProtocolError @SMPVersion @ErrorType @BrokerMsg
   {-# INLINE fromProtocolError #-}
 
-  checkCredentials (auth, _, queueId, _) cmd = case cmd of
+  checkCredentials (auth, _, entId, _) cmd = case cmd of
     -- NEW must have signature but NOT queue ID
     NEW {}
       | isNothing auth -> Left $ CMD NO_AUTH
-      | not (B.null queueId) -> Left $ CMD HAS_AUTH
+      | not (B.null entId) -> Left $ CMD HAS_AUTH
       | otherwise -> Right cmd
     -- SEND must have queue ID, signature is not always required
     SEND {}
-      | B.null queueId -> Left $ CMD NO_ENTITY
+      | B.null entId -> Left $ CMD NO_ENTITY
       | otherwise -> Right cmd
-    -- PING must not have queue ID or signature
-    PING
-      | isNothing auth && B.null queueId -> Right cmd
+    PING -> noAuthCmd
+    PRXY {} -> noAuthCmd
+    PFWD {}
+      | B.null entId -> Left $ CMD NO_ENTITY
+      | isNothing auth -> Right cmd
       | otherwise -> Left $ CMD HAS_AUTH
+    RFWD _ -> noAuthCmd
     -- other client commands must have both signature and queue ID
     _
-      | isNothing auth || B.null queueId -> Left $ CMD NO_AUTH
+      | isNothing auth || B.null entId -> Left $ CMD NO_AUTH
       | otherwise -> Right cmd
+    where
+      -- command must not have entity ID (queue or session ID) or signature
+      noAuthCmd :: Either ErrorType (Command p)
+      noAuthCmd
+        | isNothing auth && B.null entId = Right cmd
+        | otherwise = Left $ CMD HAS_AUTH
 
 instance ProtocolEncoding SMPVersion ErrorType Cmd where
   type Tag Cmd = CmdTag
@@ -1189,6 +1344,11 @@ instance ProtocolEncoding SMPVersion ErrorType Cmd where
       Cmd SSender <$> case tag of
         SEND_ -> SEND <$> _smpP <*> (unTail <$> _smpP)
         PING_ -> pure PING
+        RFWD_ -> RFWD <$> (EncFwdTransmission . unTail <$> _smpP)
+    CT SProxiedClient tag ->
+      Cmd SProxiedClient <$> case tag of
+        PFWD_ -> PFWD <$> _smpP <*> smpP <*> (EncTransmission . unTail <$> smpP)
+        PRXY_ -> PRXY <$> _smpP <*> smpP
     CT SNotifier NSUB_ -> pure $ Cmd SNotifier NSUB
 
   fromProtocolError = fromProtocolError @SMPVersion @ErrorType @BrokerMsg
@@ -1204,6 +1364,9 @@ instance ProtocolEncoding SMPVersion ErrorType BrokerMsg where
       e (MSG_, ' ', msgId, Tail body)
     NID nId srvNtfDh -> e (NID_, ' ', nId, srvNtfDh)
     NMSG nmsgNonce encNMsgMeta -> e (NMSG_, ' ', nmsgNonce, encNMsgMeta)
+    PKEY sid vr (cert, key) -> e (PKEY_, ' ', sid, vr, C.encodeCertChain cert, C.SignedObject key)
+    RRES (EncFwdResponse encBlock) -> e (RRES_, ' ', Tail encBlock)
+    PRES (EncResponse encBlock) -> e (PRES_, ' ', Tail encBlock)
     END -> e END_
     OK -> e OK_
     ERR err -> e (ERR_, ' ', err)
@@ -1221,6 +1384,9 @@ instance ProtocolEncoding SMPVersion ErrorType BrokerMsg where
     IDS_ -> IDS <$> (QIK <$> _smpP <*> smpP <*> smpP)
     NID_ -> NID <$> _smpP <*> smpP
     NMSG_ -> NMSG <$> _smpP <*> smpP
+    PKEY_ -> PKEY <$> _smpP <*> smpP <*> ((,) <$> C.certChainP <*> (C.getSignedExact <$> smpP))
+    RRES_ -> RRES <$> (EncFwdResponse . unTail <$> _smpP)
+    PRES_ -> PRES <$> (EncResponse . unTail <$> _smpP)
     END_ -> pure END
     OK_ -> pure OK
     ERR_ -> ERR <$> _smpP
@@ -1233,19 +1399,24 @@ instance ProtocolEncoding SMPVersion ErrorType BrokerMsg where
     PEBlock -> BLOCK
   {-# INLINE fromProtocolError #-}
 
-  checkCredentials (_, _, queueId, _) cmd = case cmd of
+  checkCredentials (_, _, entId, _) cmd = case cmd of
     -- IDS response should not have queue ID
     IDS _ -> Right cmd
     -- ERR response does not always have queue ID
     ERR _ -> Right cmd
     -- PONG response must not have queue ID
-    PONG
-      | B.null queueId -> Right cmd
-      | otherwise -> Left $ CMD HAS_AUTH
+    PONG -> noEntityMsg
+    PKEY {} -> noEntityMsg
+    RRES _ -> noEntityMsg
     -- other broker responses must have queue ID
     _
-      | B.null queueId -> Left $ CMD NO_ENTITY
+      | B.null entId -> Left $ CMD NO_ENTITY
       | otherwise -> Right cmd
+    where
+      noEntityMsg :: Either ErrorType BrokerMsg
+      noEntityMsg
+        | B.null entId = Right cmd
+        | otherwise = Left $ CMD HAS_AUTH
 
 -- | Parse SMP protocol commands and broker messages
 parseProtocol :: forall v err msg. ProtocolEncoding v err msg => Version v -> ByteString -> Either err msg
@@ -1268,8 +1439,11 @@ instance Encoding ErrorType where
     BLOCK -> "BLOCK"
     SESSION -> "SESSION"
     CMD err -> "CMD " <> smpEncode err
+    PROXY err -> "PROXY " <> smpEncode err
     AUTH -> "AUTH"
+    CRYPTO -> "CRYPTO"
     QUOTA -> "QUOTA"
+    EXPIRED -> "EXPIRED"
     NO_MSG -> "NO_MSG"
     LARGE_MSG -> "LARGE_MSG"
     INTERNAL -> "INTERNAL"
@@ -1280,13 +1454,16 @@ instance Encoding ErrorType where
       "BLOCK" -> pure BLOCK
       "SESSION" -> pure SESSION
       "CMD" -> CMD <$> _smpP
+      "PROXY" -> PROXY <$> _smpP
       "AUTH" -> pure AUTH
+      "CRYPTO" -> pure CRYPTO
       "QUOTA" -> pure QUOTA
+      "EXPIRED" -> pure EXPIRED
       "NO_MSG" -> pure NO_MSG
       "LARGE_MSG" -> pure LARGE_MSG
       "INTERNAL" -> pure INTERNAL
       "DUPLICATE_" -> pure DUPLICATE_
-      _ -> fail "bad error type"
+      _ -> fail "bad ErrorType"
 
 instance Encoding CommandError where
   smpEncode e = case e of
@@ -1304,8 +1481,74 @@ instance Encoding CommandError where
       "NO_AUTH" -> pure NO_AUTH
       "HAS_AUTH" -> pure HAS_AUTH
       "NO_ENTITY" -> pure NO_ENTITY
-      "NO_QUEUE" -> pure NO_ENTITY
-      _ -> fail "bad command error type"
+      "NO_QUEUE" -> pure NO_ENTITY -- for backward compatibility
+      _ -> fail "bad CommandError"
+
+instance Encoding ProxyError where
+  smpEncode = \case
+    PROTOCOL e -> "PROTOCOL " <> smpEncode e
+    BROKER e -> "BROKER " <> smpEncode e
+    BASIC_AUTH -> "BASIC_AUTH"
+    NO_SESSION -> "NO_SESSION"
+  smpP =
+    A.takeTill (== ' ') >>= \case
+      "PROTOCOL" -> PROTOCOL <$> _smpP
+      "BROKER" -> BROKER <$> _smpP
+      "BASIC_AUTH" -> pure BASIC_AUTH
+      "NO_SESSION" -> pure NO_SESSION
+      _ -> fail "bad ProxyError"
+
+instance StrEncoding ProxyError where
+  strEncode = \case
+    PROTOCOL e -> "PROTOCOL " <> strEncode e
+    BROKER e -> "BROKER " <> strEncode e
+    BASIC_AUTH -> "BASIC_AUTH"
+    NO_SESSION -> "NO_SESSION"
+  strP =
+    A.takeTill (== ' ') >>= \case
+      "PROTOCOL" -> PROTOCOL <$> _strP
+      "BROKER" -> BROKER <$> _strP
+      "BASIC_AUTH" -> pure BASIC_AUTH
+      "NO_SESSION" -> pure NO_SESSION
+      _ -> fail "bad ProxyError"
+
+instance Encoding BrokerErrorType where
+  smpEncode = \case
+    RESPONSE e -> "RESPONSE " <> smpEncode e
+    UNEXPECTED e -> "UNEXPECTED " <> smpEncode e
+    TRANSPORT e -> "TRANSPORT " <> smpEncode e
+    NETWORK -> "NETWORK"
+    TIMEOUT -> "TIMEOUT"
+    HOST -> "HOST"
+  smpP =
+    A.takeTill (== ' ') >>= \case
+      "RESPONSE" -> RESPONSE <$> _smpP
+      "UNEXPECTED" -> UNEXPECTED <$> _smpP
+      "TRANSPORT" -> TRANSPORT <$> _smpP
+      "NETWORK" -> pure NETWORK
+      "TIMEOUT" -> pure TIMEOUT
+      "HOST" -> pure HOST
+      _ -> fail "bad BrokerErrorType"
+
+instance StrEncoding BrokerErrorType where
+  strEncode = \case
+    RESPONSE e -> "RESPONSE " <> encodeUtf8 (T.pack e)
+    UNEXPECTED e -> "UNEXPECTED " <> encodeUtf8 (T.pack e)
+    TRANSPORT e -> "TRANSPORT " <> smpEncode e
+    NETWORK -> "NETWORK"
+    TIMEOUT -> "TIMEOUT"
+    HOST -> "HOST"
+  strP =
+    A.takeTill (== ' ') >>= \case
+      "RESPONSE" -> RESPONSE <$> _textP
+      "UNEXPECTED" -> UNEXPECTED <$> _textP
+      "TRANSPORT" -> TRANSPORT <$> _smpP
+      "NETWORK" -> pure NETWORK
+      "TIMEOUT" -> pure TIMEOUT
+      "HOST" -> pure HOST
+      _ -> fail "bad BrokerErrorType"
+    where
+      _textP = A.space *> (T.unpack . safeDecodeUtf8 <$> A.takeByteString)
 
 -- | Send signed SMP transmission to TCP transport.
 tPut :: Transport c => THandle v c p -> NonEmpty (Either TransportError SentRawTransmission) -> IO [Either TransportError ()]
@@ -1444,4 +1687,7 @@ $(J.deriveJSON defaultJSON ''MsgFlags)
 
 $(J.deriveJSON (sumTypeJSON id) ''CommandError)
 
-$(J.deriveJSON (sumTypeJSON id) ''ErrorType)
+$(J.deriveJSON (sumTypeJSON id) ''BrokerErrorType)
+
+-- run deriveJSON in one TH splice to allow mutual instance
+$(concat <$> mapM @[] (J.deriveJSON (sumTypeJSON id)) [''ProxyError, ''ErrorType])
diff --git a/src/Simplex/Messaging/Server.hs b/src/Simplex/Messaging/Server.hs
index a09759814..33163664a 100644
--- a/src/Simplex/Messaging/Server.hs
+++ b/src/Simplex/Messaging/Server.hs
@@ -13,7 +13,6 @@
 {-# LANGUAGE RankNTypes #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE TupleSections #-}
-{-# LANGUAGE TypeApplications #-}
 
 -- |
 -- Module      : Simplex.Messaging.Server
@@ -43,6 +42,7 @@ import Control.Monad
 import Control.Monad.Except
 import Control.Monad.IO.Unlift
 import Control.Monad.Reader
+import Control.Monad.Trans.Except
 import Crypto.Random
 import Data.Bifunctor (first)
 import Data.ByteString.Base64 (encode)
@@ -54,7 +54,7 @@ import Data.Functor (($>))
 import Data.Int (Int64)
 import qualified Data.IntMap.Strict as IM
 import Data.List (intercalate, mapAccumR)
-import Data.List.NonEmpty (NonEmpty)
+import Data.List.NonEmpty (NonEmpty (..))
 import qualified Data.List.NonEmpty as L
 import qualified Data.Map.Strict as M
 import Data.Maybe (isNothing)
@@ -68,8 +68,10 @@ import GHC.Stats (getRTSStats)
 import GHC.TypeLits (KnownNat)
 import Network.Socket (ServiceName, Socket, socketToHandle)
 import Simplex.Messaging.Agent.Lock
+import Simplex.Messaging.Client (ProtocolClient (thParams), ProtocolClientError (..), forwardSMPMessage, smpProxyError)
+import Simplex.Messaging.Client.Agent (SMPClientAgent (..), SMPClientAgentEvent (..), getSMPServerClient', lookupSMPServerClient)
 import qualified Simplex.Messaging.Crypto as C
-import Simplex.Messaging.Encoding (Encoding (smpEncode))
+import Simplex.Messaging.Encoding
 import Simplex.Messaging.Encoding.String
 import Simplex.Messaging.Protocol
 import Simplex.Messaging.Server.Control
@@ -87,10 +89,12 @@ import Simplex.Messaging.Transport
 import Simplex.Messaging.Transport.Buffer (trimCR)
 import Simplex.Messaging.Transport.Server
 import Simplex.Messaging.Util
+import Simplex.Messaging.Version
 import System.Exit (exitFailure)
 import System.IO (hPrint, hPutStrLn, hSetNewlineMode, universalNewlineMode)
 import System.Mem.Weak (deRefWeak)
 import UnliftIO (timeout)
+import UnliftIO.Async (mapConcurrently)
 import UnliftIO.Concurrent
 import UnliftIO.Directory (doesFileExist, renameFile)
 import UnliftIO.Exception
@@ -123,11 +127,13 @@ type M a = ReaderT Env IO a
 smpServer :: TMVar Bool -> ServerConfig -> M ()
 smpServer started cfg@ServerConfig {transports, transportConfig = tCfg} = do
   s <- asks server
+  pa <- asks proxyAgent
   expired <- restoreServerMessages
   restoreServerStats expired
   raceAny_
     ( serverThread s "server subscribedQ" subscribedQ subscribers subscriptions cancelSub
         : serverThread s "server ntfSubscribedQ" ntfSubscribedQ Env.notifiers ntfSubscriptions (\_ -> pure ())
+        : receiveFromProxyAgent pa
         : map runServer transports <> expireMessagesThread_ cfg <> serverStatsThread_ cfg <> controlPortThread_ cfg
     )
     `finally` withLock' (savingLock s) "final" (saveServer False)
@@ -180,6 +186,19 @@ smpServer started cfg@ServerConfig {transports, transportConfig = tCfg} = do
           mkWeakThreadId t >>= atomically . modifyTVar' (endThreads c) . IM.insert tId
           atomically $ TM.lookupDelete qId (clientSubs c)
 
+    receiveFromProxyAgent :: ProxyAgent -> M ()
+    receiveFromProxyAgent ProxyAgent {smpAgent = SMPClientAgent {agentQ}} =
+      forever $
+        atomically (readTBQueue agentQ) >>= \case
+          CAConnected srv -> logInfo $ "SMP server connected " <> showServer' srv
+          CADisconnected srv [] -> logInfo $ "SMP server disconnected " <> showServer' srv
+          CADisconnected srv subs -> logError $ "SMP server disconnected " <> showServer' srv <> " / subscriptions: " <> tshow (length subs)
+          CAReconnected srv -> logInfo $ "SMP server reconnected " <> showServer' srv
+          CAResubscribed srv subs -> logError $ "SMP server resubscribed " <> showServer' srv <> " / subscriptions: " <> tshow (length subs)
+          CASubError srv errs -> logError $ "SMP server subscription errors " <> showServer' srv <> " / errors: " <> tshow (length errs)
+      where
+        showServer' = decodeLatin1 . strEncode . host
+
     expireMessagesThread_ :: ServerConfig -> [M ()]
     expireMessagesThread_ ServerConfig {messageExpiration = Just msgExp} = [expireMessages msgExp]
     expireMessagesThread_ _ = []
@@ -315,7 +334,7 @@ smpServer started cfg@ServerConfig {transports, transportConfig = tCfg} = do
               CPResume -> withAdminRole $ hPutStrLn h "resume not implemented"
               CPClients -> withAdminRole $ do
                 active <- unliftIO u (asks clients) >>= readTVarIO
-                hPutStrLn h $ "clientId,sessionId,connected,createdAt,rcvActiveAt,sndActiveAt,age,subscriptions"
+                hPutStrLn h "clientId,sessionId,connected,createdAt,rcvActiveAt,sndActiveAt,age,subscriptions"
                 forM_ (IM.toList active) $ \(cid, Client {sessionId, connected, createdAt, rcvActiveAt, sndActiveAt, subscriptions}) -> do
                   connected' <- bshow <$> readTVarIO connected
                   rcvActiveAt' <- strEncode <$> readTVarIO rcvActiveAt
@@ -411,7 +430,7 @@ smpServer started cfg@ServerConfig {transports, transportConfig = tCfg} = do
                     hPutStrLn h "AUTH"
 
 runClientTransport :: Transport c => THandleSMP c 'TServer -> M ()
-runClientTransport h@THandle {params = THandleParams {thVersion, sessionId}} = do
+runClientTransport h@THandle {params = thParams@THandleParams {thVersion, sessionId}} = do
   q <- asks $ tbqSize . config
   ts <- liftIO getSystemTime
   active <- asks clients
@@ -424,7 +443,7 @@ runClientTransport h@THandle {params = THandleParams {thVersion, sessionId}} = d
   expCfg <- asks $ inactiveClientExpiration . config
   th <- newMVar h -- put TH under a fair lock to interleave messages and command responses
   labelMyThread . B.unpack $ "client $" <> encode sessionId
-  raceAny_ ([liftIO $ send th c, liftIO $ sendMsg th c, client c s, receive h c] <> disconnectThread_ c expCfg)
+  raceAny_ ([liftIO $ send th c, liftIO $ sendMsg th c, client thParams c s, receive h c] <> disconnectThread_ c expCfg)
     `finally` clientDisconnected c
   where
     disconnectThread_ c (Just expCfg) = [liftIO $ disconnectTransport h (rcvActiveAt c) (sndActiveAt c) expCfg (noSubscriptions c)]
@@ -465,19 +484,19 @@ receive h@THandle {params = THandleParams {thAuth}} Client {rcvQ, sndQ, rcvActiv
   forever $ do
     ts <- L.toList <$> liftIO (tGet h)
     atomically . writeTVar rcvActiveAt =<< liftIO getSystemTime
-    as <- partitionEithers <$> mapM cmdAction ts
-    write sndQ $ fst as
-    write rcvQ $ snd as
+    (errs, cmds) <- partitionEithers <$> mapM cmdAction ts
+    write sndQ errs
+    write rcvQ cmds
   where
     cmdAction :: SignedTransmission ErrorType Cmd -> M (Either (Transmission BrokerMsg) (Maybe QueueRec, Transmission Cmd))
-    cmdAction (tAuth, authorized, (corrId, queueId, cmdOrError)) =
+    cmdAction (tAuth, authorized, (corrId, entId, cmdOrError)) =
       case cmdOrError of
-        Left e -> pure $ Left (corrId, queueId, ERR e)
-        Right cmd -> verified <$> verifyTransmission ((,C.cbNonce (bs corrId)) <$> thAuth) tAuth authorized queueId cmd
+        Left e -> pure $ Left (corrId, entId, ERR e)
+        Right cmd -> verified <$> verifyTransmission ((,C.cbNonce (bs corrId)) <$> thAuth) tAuth authorized entId cmd
           where
             verified = \case
-              VRVerified qr -> Right (qr, (corrId, queueId, cmd))
-              VRFailed -> Left (corrId, queueId, ERR AUTH)
+              VRVerified qr -> Right (qr, (corrId, entId, cmd))
+              VRFailed -> Left (corrId, entId, ERR AUTH)
     write q = mapM_ (atomically . writeTBQueue q) . L.nonEmpty
 
 send :: Transport c => MVar (THandleSMP c 'TServer) -> Client -> IO ()
@@ -545,16 +564,18 @@ verifyTransmission auth_ tAuth authorized queueId cmd =
     -- SEND will be accepted without authorization before the queue is secured with KEY command
     Cmd SSender SEND {} -> verifyQueue (\q -> Just q `verified` maybe (isNothing tAuth) verify (senderKey q)) <$> get SSender
     Cmd SSender PING -> pure $ VRVerified Nothing
+    Cmd SSender RFWD {} -> pure $ VRVerified Nothing
     -- NSUB will not be accepted without authorization
-    Cmd SNotifier NSUB -> verifyQueue (\q -> maybe dummyVerify (Just q `verifiedWith`) (notifierKey <$> notifier q)) <$> get SNotifier
+    Cmd SNotifier NSUB -> verifyQueue (\q -> maybe dummyVerify (\n -> Just q `verifiedWith` notifierKey n) (notifier q)) <$> get SNotifier
+    Cmd SProxiedClient _ -> pure $ VRVerified Nothing
   where
     verify = verifyCmdAuthorization auth_ tAuth authorized
     dummyVerify = verify (dummyAuthKey tAuth) `seq` VRFailed
     verifyQueue :: (QueueRec -> VerificationResult) -> Either ErrorType QueueRec -> VerificationResult
-    verifyQueue = either (\_ -> dummyVerify)
+    verifyQueue = either (const dummyVerify)
     verified q cond = if cond then VRVerified q else VRFailed
     verifiedWith q k = q `verified` verify k
-    get :: SParty p -> M (Either ErrorType QueueRec)
+    get :: DirectParty p => SParty p -> M (Either ErrorType QueueRec)
     get party = do
       st <- asks queueStore
       atomically $ getQueue st party queueId
@@ -604,25 +625,65 @@ dummyKeyEd448 = "MEMwBQYDK2VxAzoA6ibQc9XpkSLtwrf7PLvp81qW/etiumckVFImCMRdftcG/Xo
 dummyKeyX25519 :: C.PublicKey 'C.X25519
 dummyKeyX25519 = "MCowBQYDK2VuAyEA4JGSMYht18H4mas/jHeBwfcM7jLwNYJNOAhi2/g4RXg="
 
-client :: Client -> Server -> M ()
-client clnt@Client {subscriptions, ntfSubscriptions, rcvQ, sndQ, sessionId} Server {subscribedQ, ntfSubscribedQ, notifiers} = do
+client :: THandleParams SMPVersion 'TServer -> Client -> Server -> M ()
+client thParams' clnt@Client {subscriptions, ntfSubscriptions, rcvQ, sndQ, sessionId} Server {subscribedQ, ntfSubscribedQ, notifiers} = do
   labelMyThread . B.unpack $ "client $" <> encode sessionId <> " commands"
-  forever $
-    atomically (readTBQueue rcvQ)
-      >>= mapM processCommand
-      >>= atomically . writeTBQueue sndQ
+  forever $ do
+    (proxied, rs) <- partitionEithers . L.toList <$> (mapM processCommand =<< atomically (readTBQueue rcvQ))
+    forM_ (L.nonEmpty rs) reply
+    -- TODO cancel this thread if the client gets disconnected
+    -- TODO limit client concurrency
+    forM_ (L.nonEmpty proxied) $ \cmds -> forkIO $ mapConcurrently processProxiedCmd cmds >>= reply
   where
-    processCommand :: (Maybe QueueRec, Transmission Cmd) -> M (Transmission BrokerMsg)
+    reply :: MonadIO m => NonEmpty (Transmission BrokerMsg) -> m ()
+    reply = atomically . writeTBQueue sndQ
+    processProxiedCmd :: Transmission (Command 'ProxiedClient) -> M (Transmission BrokerMsg)
+    processProxiedCmd (corrId, sessId, command) = (corrId, sessId,) <$> case command of
+      PRXY srv auth -> ifM allowProxy getRelay (pure $ ERR $ PROXY BASIC_AUTH)
+        where
+          allowProxy = do
+            ServerConfig {allowSMPProxy, newQueueBasicAuth} <- asks config
+            pure $ allowSMPProxy && maybe True ((== auth) . Just) newQueueBasicAuth
+          getRelay = do
+            ProxyAgent {smpAgent} <- asks proxyAgent
+            liftIO $ proxyResp <$> runExceptT (getSMPServerClient' smpAgent srv) `catch` (pure . Left . PCEIOError)
+            where
+              proxyResp = \case
+                Left err -> ERR $ smpProxyError err
+                Right smp ->
+                  let THandleParams {sessionId = srvSessId, thVersion, thServerVRange, thAuth} = thParams smp
+                   in case compatibleVRange thServerVRange proxiedSMPRelayVRange of
+                        -- Cap the destination relay version range to prevent client version fingerprinting.
+                        -- See comment for proxiedSMPRelayVersion.
+                        Just (Compatible vr) | thVersion >= sendingProxySMPVersion -> case thAuth of
+                          Just THAuthClient {serverCertKey} -> PKEY srvSessId vr serverCertKey
+                          Nothing -> ERR $ transportErr TENoServerAuth
+                        _ -> ERR $ transportErr TEVersion                    
+      PFWD fwdV pubKey encBlock -> do
+        ProxyAgent {smpAgent} <- asks proxyAgent
+        atomically (lookupSMPServerClient smpAgent sessId) >>= \case
+          Just smp
+            | v >= sendingProxySMPVersion ->
+                liftIO $ either (ERR . smpProxyError) PRES <$>
+                   runExceptT (forwardSMPMessage smp corrId fwdV pubKey encBlock) `catchError` (pure . Left . PCEIOError)
+            | otherwise -> pure . ERR $ transportErr TEVersion
+            where
+              THandleParams {thVersion = v} = thParams smp
+          Nothing -> pure $ ERR $ PROXY NO_SESSION
+    transportErr :: TransportError -> ErrorType
+    transportErr = PROXY . BROKER . TRANSPORT
+    processCommand :: (Maybe QueueRec, Transmission Cmd) -> M (Either (Transmission (Command 'ProxiedClient)) (Transmission BrokerMsg))
     processCommand (qr_, (corrId, queueId, cmd)) = do
       st <- asks queueStore
       case cmd of
-        Cmd SSender command ->
-          case command of
-            SEND flags msgBody -> withQueue $ \qr -> sendMessage qr flags msgBody
-            PING -> pure (corrId, "", PONG)
-        Cmd SNotifier NSUB -> subscribeNotifications
+        Cmd SProxiedClient command -> pure $ Left (corrId, queueId, command)
+        Cmd SSender command -> Right <$> case command of
+          SEND flags msgBody -> withQueue $ \qr -> sendMessage qr flags msgBody
+          PING -> pure (corrId, "", PONG)
+          RFWD encBlock -> (corrId, "",) <$> processForwardedCommand encBlock
+        Cmd SNotifier NSUB -> Right <$> subscribeNotifications
         Cmd SRecipient command ->
-          case command of
+          Right <$> case command of
             NEW rKey dhKey auth subMode ->
               ifM
                 allowNew
@@ -828,7 +889,7 @@ client clnt@Client {subscriptions, ntfSubscriptions, rcvQ, sndQ, sessionId} Serv
 
         sendMessage :: QueueRec -> MsgFlags -> MsgBody -> M (Transmission BrokerMsg)
         sendMessage qr msgFlags msgBody
-          | B.length msgBody > maxMessageLength = pure $ err LARGE_MSG
+          | B.length msgBody > maxMessageLength thVersion = pure $ err LARGE_MSG
           | otherwise = case status qr of
               QueueOff -> return $ err AUTH
               QueueActive ->
@@ -852,6 +913,7 @@ client clnt@Client {subscriptions, ntfSubscriptions, rcvQ, sndQ, sessionId} Serv
                         atomically $ updatePeriodStats (activeQueues stats) (recipientId qr)
                         pure ok
           where
+            THandleParams {thVersion} = thParams'
             mkMessage :: C.MaxLenBS MaxMessageLen -> M Message
             mkMessage body = do
               msgId <- randomId =<< asks (msgIdBytes . config)
@@ -886,6 +948,56 @@ client clnt@Client {subscriptions, ntfSubscriptions, rcvQ, sndQ, sessionId} Serv
                   encNMsgMeta = C.cbEncrypt rcvNtfDhSecret cbNonce (smpEncode msgMeta) 128
               pure . (cbNonce,) $ fromRight "" encNMsgMeta
 
+        processForwardedCommand :: EncFwdTransmission -> M BrokerMsg
+        processForwardedCommand (EncFwdTransmission s) = fmap (either ERR id) . runExceptT $ do
+          THAuthServer {serverPrivKey, sessSecret'} <- maybe (throwE $ transportErr TENoServerAuth) pure (thAuth thParams')
+          sessSecret <- maybe (throwE $ transportErr TENoServerAuth) pure sessSecret'
+          let proxyNonce = C.cbNonce $ bs corrId
+          s' <- liftEitherWith (const CRYPTO) $ C.cbDecryptNoPad sessSecret proxyNonce s
+          FwdTransmission {fwdCorrId, fwdVersion, fwdKey, fwdTransmission = EncTransmission et} <- liftEitherWith (const $ CMD SYNTAX) $ smpDecode s'
+          let clientSecret = C.dh' fwdKey serverPrivKey
+              clientNonce = C.cbNonce $ bs fwdCorrId
+          b <- liftEitherWith (const CRYPTO) $ C.cbDecrypt clientSecret clientNonce et
+          let clntTHParams = smpTHParamsSetVersion fwdVersion thParams'
+          -- only allowing single forwarded transactions
+          t' <- case tParse clntTHParams b of
+            t :| [] -> pure $ tDecodeParseValidate clntTHParams t
+            _ -> throwE BLOCK
+          let clntThAuth = Just $ THAuthServer {serverPrivKey, sessSecret' = Just clientSecret}
+          -- process forwarded SEND
+          r <-
+            lift (rejectOrVerify clntThAuth t') >>= \case
+              Left r -> pure r
+              Right t''@(_, (corrId', entId', cmd')) -> case cmd' of
+                Cmd SSender SEND {} ->
+                  -- Left will not be returned by processCommand, as only SEND command is allowed
+                  fromRight (corrId', entId', ERR INTERNAL) <$> lift (processCommand t'')
+                _ ->
+                  pure (corrId', entId', ERR $ CMD PROHIBITED)
+          -- encode response
+          r' <- case batchTransmissions (batch clntTHParams) (blockSize clntTHParams) [Right (Nothing, encodeTransmission clntTHParams r)] of
+            [] -> throwE INTERNAL -- at least 1 item is guaranteed from NonEmpty/Right
+            TBError _ _ : _ -> throwE BLOCK
+            TBTransmission b' _ : _ -> pure b'
+            TBTransmissions b' _ _ : _ -> pure b'
+          -- encrypt to client
+          r2 <- liftEitherWith (const BLOCK) $ EncResponse <$> C.cbEncrypt clientSecret (C.reverseNonce clientNonce) r' paddedProxiedMsgLength
+          -- encrypt to proxy
+          let fr = FwdResponse {fwdCorrId, fwdResponse = r2}
+              r3 = EncFwdResponse $ C.cbEncryptNoPad sessSecret (C.reverseNonce proxyNonce) (smpEncode fr)
+          pure $ RRES r3
+          where
+            rejectOrVerify :: Maybe (THandleAuth 'TServer) -> SignedTransmission ErrorType Cmd -> M (Either (Transmission BrokerMsg) (Maybe QueueRec, Transmission Cmd))
+            rejectOrVerify clntThAuth (tAuth, authorized, (corrId', entId', cmdOrError)) =
+              case cmdOrError of
+                Left e -> pure $ Left (corrId', entId', ERR e)
+                Right cmd'@(Cmd SSender SEND {}) -> verified <$> verifyTransmission ((,C.cbNonce (bs corrId')) <$> clntThAuth) tAuth authorized entId' cmd'
+                  where
+                    verified = \case
+                      VRVerified qr -> Right (qr, (corrId', entId', cmd'))
+                      VRFailed -> Left (corrId', entId', ERR AUTH)
+                Right _ -> pure $ Left (corrId', entId', ERR $ CMD PROHIBITED)
+
         deliverMessage :: T.Text -> QueueRec -> RecipientId -> TVar Sub -> MsgQueue -> Maybe Message -> M (Transmission BrokerMsg)
         deliverMessage name qr rId sub q msg_ = time (name <> " deliver") $ do
           readTVarIO sub >>= \case
diff --git a/src/Simplex/Messaging/Server/Env/STM.hs b/src/Simplex/Messaging/Server/Env/STM.hs
index bd8262f07..f23192aeb 100644
--- a/src/Simplex/Messaging/Server/Env/STM.hs
+++ b/src/Simplex/Messaging/Server/Env/STM.hs
@@ -22,6 +22,7 @@ import Network.Socket (ServiceName)
 import qualified Network.TLS as T
 import Numeric.Natural
 import Simplex.Messaging.Agent.Lock
+import Simplex.Messaging.Client.Agent (SMPClientAgent, SMPClientAgentConfig, newSMPClientAgent)
 import Simplex.Messaging.Crypto (KeyHash (..))
 import qualified Simplex.Messaging.Crypto as C
 import Simplex.Messaging.Protocol
@@ -79,7 +80,9 @@ data ServerConfig = ServerConfig
     -- | TCP transport config
     transportConfig :: TransportServerConfig,
     -- | run listener on control port
-    controlPort :: Maybe ServiceName
+    controlPort :: Maybe ServiceName,
+    smpAgentCfg :: SMPClientAgentConfig,
+    allowSMPProxy :: Bool -- auth is the same with `newQueueBasicAuth`
   }
 
 defMsgExpirationDays :: Int64
@@ -110,8 +113,9 @@ data Env = Env
     tlsServerParams :: T.ServerParams,
     serverStats :: ServerStats,
     sockets :: SocketState,
-    clientSeq :: TVar Int,
-    clients :: TVar (IntMap Client)
+    clientSeq :: TVar ClientId,
+    clients :: TVar (IntMap Client),
+    proxyAgent :: ProxyAgent -- senders served on this proxy
   }
 
 data Server = Server
@@ -122,8 +126,14 @@ data Server = Server
     savingLock :: Lock
   }
 
+data ProxyAgent = ProxyAgent
+  { smpAgent :: SMPClientAgent
+  }
+
+type ClientId = Int
+
 data Client = Client
-  { clientId :: Int,
+  { clientId :: ClientId,
     subscriptions :: TMap RecipientId (TVar Sub),
     ntfSubscriptions :: TMap NotifierId (),
     rcvQ :: TBQueue (NonEmpty (Maybe QueueRec, Transmission Cmd)),
@@ -155,7 +165,7 @@ newServer = do
   savingLock <- createLock
   return Server {subscribedQ, subscribers, ntfSubscribedQ, notifiers, savingLock}
 
-newClient :: TVar Int -> Natural -> VersionSMP -> ByteString -> SystemTime -> STM Client
+newClient :: TVar ClientId -> Natural -> VersionSMP -> ByteString -> SystemTime -> STM Client
 newClient nextClientId qSize thVersion sessionId createdAt = do
   clientId <- stateTVar nextClientId $ \next -> (next, next + 1)
   subscriptions <- TM.empty
@@ -176,7 +186,7 @@ newSubscription subThread = do
   return Sub {subThread, delivered}
 
 newEnv :: ServerConfig -> IO Env
-newEnv config@ServerConfig {caCertificateFile, certificateFile, privateKeyFile, storeLogFile, transportConfig} = do
+newEnv config@ServerConfig {caCertificateFile, certificateFile, privateKeyFile, storeLogFile, smpAgentCfg, transportConfig} = do
   server <- atomically newServer
   queueStore <- atomically newQueueStore
   msgStore <- atomically newMsgStore
@@ -189,7 +199,8 @@ newEnv config@ServerConfig {caCertificateFile, certificateFile, privateKeyFile,
   sockets <- atomically newSocketState
   clientSeq <- newTVarIO 0
   clients <- newTVarIO mempty
-  return Env {config, server, serverIdentity, queueStore, msgStore, random, storeLog, tlsServerParams, serverStats, sockets, clientSeq, clients}
+  proxyAgent <- atomically $ newSMPProxyAgent smpAgentCfg random
+  return Env {config, server, serverIdentity, queueStore, msgStore, random, storeLog, tlsServerParams, serverStats, sockets, clientSeq, clients, proxyAgent}
   where
     restoreQueues :: QueueStore -> FilePath -> IO (StoreLog 'WriteMode)
     restoreQueues QueueStore {queues, senders, notifiers} f = do
@@ -205,3 +216,8 @@ newEnv config@ServerConfig {caCertificateFile, certificateFile, privateKeyFile,
     addNotifier q = case notifier q of
       Nothing -> id
       Just NtfCreds {notifierId} -> M.insert notifierId (recipientId q)
+
+newSMPProxyAgent :: SMPClientAgentConfig -> TVar ChaChaDRG -> STM ProxyAgent
+newSMPProxyAgent smpAgentCfg random = do
+  smpAgent <- newSMPClientAgent smpAgentCfg random
+  pure ProxyAgent {smpAgent}
diff --git a/src/Simplex/Messaging/Server/Main.hs b/src/Simplex/Messaging/Server/Main.hs
index d75d02812..418ef36c8 100644
--- a/src/Simplex/Messaging/Server/Main.hs
+++ b/src/Simplex/Messaging/Server/Main.hs
@@ -14,10 +14,13 @@ import qualified Data.ByteString.Char8 as B
 import Data.Functor (($>))
 import Data.Ini (lookupValue, readIniFile)
 import Data.Maybe (fromMaybe)
+import Data.Text (Text)
 import qualified Data.Text as T
 import Data.Text.Encoding (encodeUtf8)
 import Network.Socket (HostName)
 import Options.Applicative
+import Simplex.Messaging.Client (HostMode (..), NetworkConfig (..), ProtocolClientConfig (..), SocksMode (..), defaultNetworkConfig)
+import Simplex.Messaging.Client.Agent (SMPClientAgentConfig (..), defaultSMPClientAgentConfig)
 import qualified Simplex.Messaging.Crypto as C
 import Simplex.Messaging.Encoding.String
 import Simplex.Messaging.Protocol (BasicAuth (..), ProtoServerWithAuth (ProtoServerWithAuth), pattern SMPServer)
@@ -25,10 +28,11 @@ import Simplex.Messaging.Server (runSMPServer)
 import Simplex.Messaging.Server.CLI
 import Simplex.Messaging.Server.Env.STM (ServerConfig (..), defMsgExpirationDays, defaultInactiveClientExpiration, defaultMessageExpiration)
 import Simplex.Messaging.Server.Expiration
-import Simplex.Messaging.Transport (simplexMQVersion, supportedSMPHandshakes, supportedServerSMPRelayVRange)
+import Simplex.Messaging.Transport (batchCmdsSMPVersion, sendingProxySMPVersion, simplexMQVersion, supportedSMPHandshakes, supportedServerSMPRelayVRange)
 import Simplex.Messaging.Transport.Client (TransportHost (..))
 import Simplex.Messaging.Transport.Server (TransportServerConfig (..), defaultTransportServerConfig)
 import Simplex.Messaging.Util (safeDecodeUtf8)
+import Simplex.Messaging.Version (mkVersionRange)
 import System.Directory (createDirectoryIfMissing, doesFileExist)
 import System.FilePath (combine)
 import System.IO (BufferMode (..), hSetBuffering, stderr, stdout)
@@ -129,7 +133,7 @@ smpServerCLI cfgPath logPath =
                    )
                 <> "\n\n\
                    \# control_port_admin_password:\n\
-                   \# control_port_user_password:\n\
+                   \# control_port_user_password:\n\n\
                    \[TRANSPORT]\n\
                    \# host is only used to print server address on start\n"
                 <> ("host: " <> host <> "\n")
@@ -137,6 +141,18 @@ smpServerCLI cfgPath logPath =
                 <> "log_tls_errors: off\n\
                    \websockets: off\n\
                    \# control_port: 5224\n\n\
+                   \[PROXY]\n\
+                   \# Network configuration for SMP proxy client.\n\
+                   \# `host_mode` can be 'public' (default) or 'onion'.\n\
+                   \# It defines prefferred hostname for destination servers with multiple hostnames.\n\
+                   \# host_mode: public\n\
+                   \# required_host_mode: off\n\n\
+                   \# SOCKS proxy port for forwarding messages to destination servers.\n\
+                   \# You may need a separate instance of SOCKS proxy for incoming single-hop requests.\n\
+                   \# socks_proxy: localhost:9050\n\n\
+                   \# `socks_mode` can be 'onion' for SOCKS proxy to be used for .onion destination hosts only (default)\n\
+                   \# or 'always' to be used for all destination hosts (can be used if it is an .onion server).\n\
+                   \# socks_mode: onion\n\n\
                    \[INACTIVE_CLIENTS]\n\
                    \# TTL and interval to check inactive clients\n\
                    \disconnect: off\n"
@@ -214,8 +230,34 @@ smpServerCLI cfgPath logPath =
                   { logTLSErrors = fromMaybe False $ iniOnOff "TRANSPORT" "log_tls_errors" ini,
                     alpn = Just supportedSMPHandshakes
                   },
-              controlPort = either (const Nothing) (Just . T.unpack) $ lookupValue "TRANSPORT" "control_port" ini
+              controlPort = either (const Nothing) (Just . T.unpack) $ lookupValue "TRANSPORT" "control_port" ini,
+              smpAgentCfg =
+                defaultSMPClientAgentConfig
+                  { smpCfg =
+                      (smpCfg defaultSMPClientAgentConfig)
+                        { serverVRange = mkVersionRange batchCmdsSMPVersion sendingProxySMPVersion,
+                          agreeSecret = True,
+                          networkConfig =
+                            defaultNetworkConfig
+                              { socksProxy = either error id <$> strDecodeIni "PROXY" "socks_proxy" ini,
+                                socksMode = either (const SMOnion) textToSocksMode $ lookupValue "PROXY" "socks_mode" ini,
+                                hostMode = either (const HMPublic) textToHostMode $ lookupValue "PROXY" "host_mode" ini,
+                                requiredHostMode = fromMaybe False $ iniOnOff "PROXY" "required_host_mode" ini
+                              }
+                        }
+                  },
+              allowSMPProxy = True
             }
+        textToSocksMode :: Text -> SocksMode
+        textToSocksMode = \case
+          "always" -> SMAlways
+          "onion" -> SMOnion
+          s -> error . T.unpack $ "Invalid socks_mode: " <> s
+        textToHostMode :: Text -> HostMode
+        textToHostMode = \case
+          "public" -> HMPublic
+          "onion" -> HMOnionViaSocks
+          s -> error . T.unpack $ "Invalid host_mode: " <> s
 
 data CliCommand
   = Init InitOptions
@@ -306,4 +348,3 @@ cliCommandP cfgPath logPath iniFile =
       pure InitOptions {enableStoreLog, logStats, signAlgorithm, ip, fqdn, password, scripted}
     parseBasicAuth :: ReadM ServerPassword
     parseBasicAuth = eitherReader $ fmap ServerPassword . strDecode . B.pack
-
diff --git a/src/Simplex/Messaging/Server/QueueStore/STM.hs b/src/Simplex/Messaging/Server/QueueStore/STM.hs
index b76ad4998..8de7a38c6 100644
--- a/src/Simplex/Messaging/Server/QueueStore/STM.hs
+++ b/src/Simplex/Messaging/Server/QueueStore/STM.hs
@@ -54,7 +54,7 @@ addQueue QueueStore {queues, senders} q@QueueRec {recipientId = rId, senderId =
   where
     hasId = (||) <$> TM.member rId queues <*> TM.member sId senders
 
-getQueue :: QueueStore -> SParty p -> QueueId -> STM (Either ErrorType QueueRec)
+getQueue :: DirectParty p => QueueStore -> SParty p -> QueueId -> STM (Either ErrorType QueueRec)
 getQueue QueueStore {queues, senders, notifiers} party qId =
   toResult <$> (mapM readTVar =<< getVar)
   where
diff --git a/src/Simplex/Messaging/Transport.hs b/src/Simplex/Messaging/Transport.hs
index e1d383b5a..6eddcabf8 100644
--- a/src/Simplex/Messaging/Transport.hs
+++ b/src/Simplex/Messaging/Transport.hs
@@ -36,6 +36,7 @@ module Simplex.Messaging.Transport
     supportedSMPHandshakes,
     supportedClientSMPRelayVRange,
     supportedServerSMPRelayVRange,
+    proxiedSMPRelayVRange,
     legacyServerSMPRelayVRange,
     currentClientSMPRelayVersion,
     legacyServerSMPRelayVersion,
@@ -44,6 +45,7 @@ module Simplex.Messaging.Transport
     basicAuthSMPVersion,
     subModeSMPVersion,
     authCmdsSMPVersion,
+    sendingProxySMPVersion,
     simplexMQVersion,
     smpBlockSize,
     TransportConfig (..),
@@ -74,14 +76,13 @@ module Simplex.Messaging.Transport
     smpClientHandshake,
     tPutBlock,
     tGetBlock,
-    serializeTransportError,
-    transportErrorP,
     sendHandshake,
     getHandshake,
+    smpTHParamsSetVersion,
   )
 where
 
-import Control.Applicative (optional, (<|>))
+import Control.Applicative (optional)
 import Control.Monad (forM)
 import Control.Monad.Except
 import Control.Monad.Trans.Except (throwE)
@@ -152,14 +153,25 @@ subModeSMPVersion = VersionSMP 6
 authCmdsSMPVersion :: VersionSMP
 authCmdsSMPVersion = VersionSMP 7
 
+sendingProxySMPVersion :: VersionSMP
+sendingProxySMPVersion = VersionSMP 8
+
 currentClientSMPRelayVersion :: VersionSMP
-currentClientSMPRelayVersion = VersionSMP 7
+currentClientSMPRelayVersion = VersionSMP 8
 
 legacyServerSMPRelayVersion :: VersionSMP
 legacyServerSMPRelayVersion = VersionSMP 6
 
 currentServerSMPRelayVersion :: VersionSMP
-currentServerSMPRelayVersion = VersionSMP 7
+currentServerSMPRelayVersion = VersionSMP 8
+
+-- Max SMP protocol version to be used in e2e encrypted
+-- connection between client and server, as defined by SMP proxy.
+-- SMP proxy sets it to lower than its current version
+-- to prevent client version fingerprinting by the
+-- destination relays when clients upgrade at different times.
+proxiedSMPRelayVersion :: VersionSMP
+proxiedSMPRelayVersion = VersionSMP 8
 
 -- minimal supported protocol version is 4
 -- TODO remove code that supports sending commands without batching
@@ -172,6 +184,10 @@ legacyServerSMPRelayVRange = mkVersionRange batchCmdsSMPVersion legacyServerSMPR
 supportedServerSMPRelayVRange :: VersionRangeSMP
 supportedServerSMPRelayVRange = mkVersionRange batchCmdsSMPVersion currentServerSMPRelayVersion
 
+-- This range initially allows only version 8 - see the comment above.
+proxiedSMPRelayVRange :: VersionRangeSMP
+proxiedSMPRelayVRange = mkVersionRange sendingProxySMPVersion proxiedSMPRelayVersion
+
 supportedSMPHandshakes :: [ALPN]
 supportedSMPHandshakes = ["smp/1"]
 
@@ -338,6 +354,8 @@ type THandleSMP c p = THandle SMPVersion c p
 data THandleParams v p = THandleParams
   { sessionId :: SessionId,
     blockSize :: Int,
+    -- | server protocol version range
+    thServerVRange :: VersionRange v,
     -- | agreed server protocol version
     thVersion :: Version v,
     -- | peer public key for command authorization and shared secrets for entity ID encryption
@@ -370,6 +388,7 @@ data ServerHandshake = ServerHandshake
   { smpVersionRange :: VersionRangeSMP,
     sessionId :: SessionId,
     -- pub key to agree shared secrets for command authorization and entity ID encryption.
+    -- todo C.PublicKeyX25519
     authPubKey :: Maybe (X.CertificateChain, X.SignedExact X.PubKey)
   }
 
@@ -421,6 +440,8 @@ authEncryptCmdsP v p = if v >= authCmdsSMPVersion then optional p else pure Noth
 data TransportError
   = -- | error parsing transport block
     TEBadBlock
+  | -- | incompatible client or server version
+    TEVersion
   | -- | message does not fit in transport block
     TELargeMsg
   | -- | incorrect session ID
@@ -436,31 +457,29 @@ data TransportError
 data HandshakeError
   = -- | parsing error
     PARSE
-  | -- | incompatible peer version
-    VERSION
   | -- | incorrect server identity
     IDENTITY
   | -- | v7 authentication failed
     BAD_AUTH
   deriving (Eq, Read, Show, Exception)
 
--- | SMP encrypted transport error parser.
-transportErrorP :: Parser TransportError
-transportErrorP =
-  "BLOCK" $> TEBadBlock
-    <|> "LARGE_MSG" $> TELargeMsg
-    <|> "SESSION" $> TEBadSession
-    <|> "NO_AUTH" $> TENoServerAuth
-    <|> "HANDSHAKE " *> (TEHandshake <$> parseRead1)
-
--- | Serialize SMP encrypted transport error.
-serializeTransportError :: TransportError -> ByteString
-serializeTransportError = \case
-  TEBadBlock -> "BLOCK"
-  TELargeMsg -> "LARGE_MSG"
-  TEBadSession -> "SESSION"
-  TENoServerAuth -> "NO_AUTH"
-  TEHandshake e -> "HANDSHAKE " <> bshow e
+instance Encoding TransportError where
+  smpP =
+    A.takeTill (== ' ') >>= \case
+      "BLOCK" -> pure TEBadBlock
+      "VERSION" -> pure TEVersion
+      "LARGE_MSG" -> pure TELargeMsg
+      "SESSION" -> pure TEBadSession
+      "NO_AUTH" -> pure TENoServerAuth
+      "HANDSHAKE" -> TEHandshake <$> (A.space *> parseRead1)
+      _ -> fail "bad TransportError"
+  smpEncode = \case
+    TEBadBlock -> "BLOCK"
+    TEVersion -> "VERSION"
+    TELargeMsg -> "LARGE_MSG"
+    TEBadSession -> "SESSION"
+    TENoServerAuth -> "NO_AUTH"
+    TEHandshake e -> "HANDSHAKE " <> bshow e
 
 -- | Pad and send block to SMP transport.
 tPutBlock :: Transport c => THandle v c p -> ByteString -> IO (Either TransportError ())
@@ -490,9 +509,10 @@ smpServerHandshake serverSignKey c (k, pk) kh smpVRange = do
     ClientHandshake {smpVersion = v, keyHash, authPubKey = k'}
       | keyHash /= kh ->
           throwE $ TEHandshake IDENTITY
-      | v `isCompatible` smpVersionRange ->
-          pure $ smpThHandleServer th v pk k'
-      | otherwise -> throwE $ TEHandshake VERSION
+      | otherwise ->
+          case compatibleVRange' smpVersionRange v of
+            Just (Compatible vr) -> pure $ smpTHandleServer th v vr pk k'
+            Nothing -> throwE TEVersion
 
 -- | Client SMP transport handshake.
 --
@@ -503,8 +523,8 @@ smpClientHandshake c ks_ keyHash@(C.KeyHash kh) smpVRange = do
   ServerHandshake {sessionId = sessId, smpVersionRange, authPubKey} <- getHandshake th
   if sessionId /= sessId
     then throwE TEBadSession
-    else case smpVersionRange `compatibleVersion` smpVRange of
-      Just (Compatible v) -> do
+    else case smpVersionRange `compatibleVRange` smpVRange of
+      Just (Compatible vr) -> do
         ck_ <- forM authPubKey $ \certKey@(X.CertificateChain cert, exact) ->
           liftEitherWith (const $ TEHandshake BAD_AUTH) $ do
             case cert of
@@ -513,26 +533,33 @@ smpClientHandshake c ks_ keyHash@(C.KeyHash kh) smpVRange = do
             serverKey <- getServerVerifyKey c
             pubKey <- C.verifyX509 serverKey exact
             (,certKey) <$> (C.x509ToPublic (pubKey, []) >>= C.pubKey)
+        let v = maxVersion vr
         sendHandshake th $ ClientHandshake {smpVersion = v, keyHash, authPubKey = fst <$> ks_}
-        pure $ smpThHandleClient th v (snd <$> ks_) ck_
-      Nothing -> throwE $ TEHandshake VERSION
+        pure $ smpTHandleClient th v vr (snd <$> ks_) ck_
+      Nothing -> throwE TEVersion
 
-smpThHandleServer :: forall c. THandleSMP c 'TServer -> VersionSMP -> C.PrivateKeyX25519 -> Maybe C.PublicKeyX25519 -> THandleSMP c 'TServer
-smpThHandleServer th v pk k_ =
+smpTHandleServer :: forall c. THandleSMP c 'TServer -> VersionSMP -> VersionRangeSMP -> C.PrivateKeyX25519 -> Maybe C.PublicKeyX25519 -> THandleSMP c 'TServer
+smpTHandleServer th v vr pk k_ =
   let thAuth = THAuthServer {serverPrivKey = pk, sessSecret' = (`C.dh'` pk) <$> k_}
-   in smpThHandle_ th v (Just thAuth)
+   in smpTHandle_ th v vr (Just thAuth)
 
-smpThHandleClient :: forall c. THandleSMP c 'TClient -> VersionSMP -> Maybe C.PrivateKeyX25519 -> Maybe (C.PublicKeyX25519, (X.CertificateChain, X.SignedExact X.PubKey)) -> THandleSMP c 'TClient
-smpThHandleClient th v pk_ ck_ =
+smpTHandleClient :: forall c. THandleSMP c 'TClient -> VersionSMP -> VersionRangeSMP -> Maybe C.PrivateKeyX25519 -> Maybe (C.PublicKeyX25519, (X.CertificateChain, X.SignedExact X.PubKey)) -> THandleSMP c 'TClient
+smpTHandleClient th v vr pk_ ck_ =
   let thAuth = (\(k, ck) -> THAuthClient {serverPeerPubKey = k, serverCertKey = ck, sessSecret = C.dh' k <$> pk_}) <$> ck_
-   in smpThHandle_ th v thAuth
+   in smpTHandle_ th v vr thAuth
 
-smpThHandle_ :: forall c p. THandleSMP c p -> VersionSMP -> Maybe (THandleAuth p) -> THandleSMP c p
-smpThHandle_ th@THandle {params} v thAuth =
+smpTHandle_ :: forall c p. THandleSMP c p -> VersionSMP -> VersionRangeSMP -> Maybe (THandleAuth p) -> THandleSMP c p
+smpTHandle_ th@THandle {params} v vr thAuth =
   -- TODO drop SMP v6: make thAuth non-optional
-  let params' = params {thVersion = v, thAuth, implySessId = v >= authCmdsSMPVersion}
+  let params' = params {thVersion = v, thServerVRange = vr, thAuth, implySessId = v >= authCmdsSMPVersion}
    in (th :: THandleSMP c p) {params = params'}
 
+-- This function is only used with v >= 8, so currently it's a simple record update.
+-- It may require some parameters update in the future, to be consistent with smpTHandle_.
+smpTHParamsSetVersion :: VersionSMP -> THandleParams SMPVersion p -> THandleParams SMPVersion p
+smpTHParamsSetVersion v params = params {thVersion = v}
+{-# INLINE smpTHParamsSetVersion #-}
+
 sendHandshake :: (Transport c, Encoding smp) => THandle v c p -> smp -> ExceptT TransportError IO ()
 sendHandshake th = ExceptT . tPutBlock th . smpEncode
 
@@ -543,7 +570,17 @@ getHandshake th = ExceptT $ (first (\_ -> TEHandshake PARSE) . A.parseOnly smpP
 smpTHandle :: Transport c => c -> THandleSMP c p
 smpTHandle c = THandle {connection = c, params}
   where
-    params = THandleParams {sessionId = tlsUnique c, blockSize = smpBlockSize, thVersion = VersionSMP 0, thAuth = Nothing, implySessId = False, batch = True}
+    v = VersionSMP 0
+    params =
+      THandleParams
+        { sessionId = tlsUnique c,
+          blockSize = smpBlockSize,
+          thServerVRange = versionToRange v,
+          thVersion = v,
+          thAuth = Nothing,
+          implySessId = False,
+          batch = True
+        }
 
 $(J.deriveJSON (sumTypeJSON id) ''HandshakeError)
 
diff --git a/src/Simplex/Messaging/Version.hs b/src/Simplex/Messaging/Version.hs
index 25f7368d1..5576cfa9f 100644
--- a/src/Simplex/Messaging/Version.hs
+++ b/src/Simplex/Messaging/Version.hs
@@ -23,6 +23,8 @@ module Simplex.Messaging.Version
     isCompatibleRange,
     proveCompatible,
     compatibleVersion,
+    compatibleVRange,
+    compatibleVRange',
   )
 where
 
@@ -98,6 +100,7 @@ class VersionScope v => VersionI v a | a -> v where
 class VersionScope v => VersionRangeI v a | a -> v where
   type VersionT v a
   versionRange :: a -> VersionRange v
+  toVersionRange :: a -> VersionRange v -> a
   toVersionT :: a -> Version v -> VersionT v a
 
 instance VersionScope v => VersionI v (Version v) where
@@ -108,6 +111,7 @@ instance VersionScope v => VersionI v (Version v) where
 instance VersionScope v => VersionRangeI v (VersionRange v) where
   type VersionT v (VersionRange v) = Version v
   versionRange = id
+  toVersionRange _ vr = vr
   toVersionT _ v = v
 
 newtype Compatible a = Compatible_ a
@@ -135,5 +139,24 @@ compatibleVersion x vr =
     max1 = maxVersion $ versionRange x
     max2 = maxVersion vr
 
+-- | intersection of version ranges
+compatibleVRange :: VersionRangeI v a => a -> VersionRange v -> Maybe (Compatible a)
+compatibleVRange x vr =
+  compatibleVRange_ x (max min1 min2) (min max1 max2)
+  where
+    VRange min1 max1 = versionRange x
+    VRange min2 max2 = vr
+
+-- | version range capped by compatible version
+compatibleVRange' :: VersionRangeI v a => a -> Version v -> Maybe (Compatible a)
+compatibleVRange' x v
+  | v <= max1 = compatibleVRange_ x min1 v
+  | otherwise = Nothing
+  where
+    VRange min1 max1 = versionRange x
+
+compatibleVRange_ :: VersionRangeI v a => a -> Version v -> Version v -> Maybe (Compatible a)
+compatibleVRange_ x v1 v2 = Compatible_ . toVersionRange x <$> safeVersionRange v1 v2
+
 mkCompatibleIf :: a -> Bool -> Maybe (Compatible a)
 x `mkCompatibleIf` cond = if cond then Just $ Compatible_ x else Nothing
diff --git a/tests/AgentTests.hs b/tests/AgentTests.hs
index df117c105..65713aaa4 100644
--- a/tests/AgentTests.hs
+++ b/tests/AgentTests.hs
@@ -13,7 +13,7 @@ module AgentTests (agentTests) where
 
 import AgentTests.ConnectionRequestTests
 import AgentTests.DoubleRatchetTests (doubleRatchetTests)
-import AgentTests.FunctionalAPITests (functionalAPITests, inAnyOrder, pattern Msg, pattern Msg')
+import AgentTests.FunctionalAPITests (functionalAPITests, inAnyOrder, pattern Msg, pattern Msg', pattern SENT)
 import AgentTests.MigrationTests (migrationTests)
 import AgentTests.NotificationTests (notificationTests)
 import AgentTests.SQLiteTests (storeTests)
@@ -27,7 +27,7 @@ import GHC.Stack (withFrozenCallStack)
 import Network.HTTP.Types (urlEncode)
 import SMPAgentClient
 import SMPClient (testKeyHash, testPort, testPort2, testStoreLogFile, withSmpServer, withSmpServerStoreLogOn)
-import Simplex.Messaging.Agent.Protocol hiding (CONF, INFO, MID, REQ)
+import Simplex.Messaging.Agent.Protocol hiding (CONF, INFO, MID, REQ, SENT)
 import qualified Simplex.Messaging.Agent.Protocol as A
 import Simplex.Messaging.Crypto.Ratchet (InitialKeys (..), PQEncryption (..), PQSupport (..), pattern IKPQOff, pattern IKPQOn, pattern PQEncOn, pattern PQSupportOff, pattern PQSupportOn)
 import qualified Simplex.Messaging.Crypto.Ratchet as CR
@@ -429,8 +429,8 @@ testServerConnectionAfterError t _ = do
       bob #: ("1", "alice", "SUB") =#> \("1", "alice", ERR (BROKER _ e)) -> e == NETWORK || e == TIMEOUT
       alice #: ("1", "bob", "SUB") =#> \("1", "bob", ERR (BROKER _ e)) -> e == NETWORK || e == TIMEOUT
       withServer $ do
-        alice <#=? \case ("", "bob", APC _ (SENT 4)) -> True; ("", "", APC _ (UP s ["bob"])) -> s == server; _ -> False
-        alice <#=? \case ("", "bob", APC _ (SENT 4)) -> True; ("", "", APC _ (UP s ["bob"])) -> s == server; _ -> False
+        alice <#=? \case ("", "bob", APC SAEConn (SENT 4)) -> True; ("", "", APC _ (UP s ["bob"])) -> s == server; _ -> False
+        alice <#=? \case ("", "bob", APC SAEConn (SENT 4)) -> True; ("", "", APC _ (UP s ["bob"])) -> s == server; _ -> False
         bob <#=? \case ("", "alice", APC _ (Msg "hello")) -> True; ("", "", APC _ (UP s ["alice"])) -> s == server; _ -> False
         bob <#=? \case ("", "alice", APC _ (Msg "hello")) -> True; ("", "", APC _ (UP s ["alice"])) -> s == server; _ -> False
         bob #: ("2", "alice", "ACK 4") #> ("2", "alice", OK)
diff --git a/tests/AgentTests/FunctionalAPITests.hs b/tests/AgentTests/FunctionalAPITests.hs
index f1dcc058a..6ef2e00aa 100644
--- a/tests/AgentTests/FunctionalAPITests.hs
+++ b/tests/AgentTests/FunctionalAPITests.hs
@@ -45,6 +45,7 @@ module AgentTests.FunctionalAPITests
     pattern REQ,
     pattern Msg,
     pattern Msg',
+    pattern SENT,
     agentCfgV7,
   )
 where
@@ -70,17 +71,17 @@ import Data.Word (Word16)
 import qualified Database.SQLite.Simple as SQL
 import GHC.Stack (withFrozenCallStack)
 import SMPAgentClient
-import SMPClient (cfg, testPort, testPort2, testStoreLogFile2, withSmpServer, withSmpServerConfigOn, withSmpServerOn, withSmpServerStoreLogOn, withSmpServerStoreMsgLogOn, withSmpServerV7)
+import SMPClient (cfg, testPort, testPort2, testStoreLogFile2, withSmpServer, withSmpServerConfigOn, withSmpServerOn, withSmpServerProxy, withSmpServerStoreLogOn, withSmpServerStoreMsgLogOn, withSmpServerV7)
 import Simplex.Messaging.Agent hiding (createConnection, joinConnection, sendMessage)
 import qualified Simplex.Messaging.Agent as A
 import Simplex.Messaging.Agent.Client (ProtocolTestFailure (..), ProtocolTestStep (..), UserNetworkInfo (..), UserNetworkType (..), waitForUserNetwork)
 import Simplex.Messaging.Agent.Env.SQLite (AgentConfig (..), InitialAgentServers (..), createAgentStore)
-import Simplex.Messaging.Agent.Protocol hiding (CON, CONF, INFO, REQ)
+import Simplex.Messaging.Agent.Protocol hiding (CON, CONF, INFO, REQ, SENT)
 import qualified Simplex.Messaging.Agent.Protocol as A
 import Simplex.Messaging.Agent.RetryInterval (RetryInterval (..))
 import Simplex.Messaging.Agent.Store.SQLite (MigrationConfirmation (..), SQLiteStore (dbNew))
 import Simplex.Messaging.Agent.Store.SQLite.Common (withTransaction')
-import Simplex.Messaging.Client (NetworkConfig (..), ProtocolClientConfig (..), TransportSessionMode (TSMEntity, TSMUser), defaultClientConfig)
+import Simplex.Messaging.Client (NetworkConfig (..), ProtocolClientConfig (..), SMPProxyFallback (..), SMPProxyMode (..), TransportSessionMode (TSMEntity, TSMUser), defaultClientConfig)
 import qualified Simplex.Messaging.Crypto as C
 import Simplex.Messaging.Crypto.Ratchet (InitialKeys (..), PQEncryption (..), PQSupport (..), pattern PQEncOff, pattern PQEncOn, pattern PQSupportOff, pattern PQSupportOn)
 import qualified Simplex.Messaging.Crypto.Ratchet as CR
@@ -171,6 +172,9 @@ pattern MsgErr msgId err msgBody <- MSG MsgMeta {recipient = (msgId, _), integri
 pattern MsgErr' :: AgentMsgId -> MsgErrorType -> PQEncryption -> MsgBody -> ACommand 'Agent 'AEConn
 pattern MsgErr' msgId err pq msgBody <- MSG MsgMeta {recipient = (msgId, _), integrity = MsgError err, pqEncryption = pq} _ msgBody
 
+pattern SENT :: AgentMsgId -> ACommand 'Agent 'AEConn
+pattern SENT msgId = A.SENT msgId Nothing
+
 pattern Rcvd :: AgentMsgId -> ACommand 'Agent 'AEConn
 pattern Rcvd agentMsgId <- RCVD MsgMeta {integrity = MsgOk} [MsgReceipt {agentMsgId, msgRcptStatus = MROk}]
 
@@ -455,26 +459,28 @@ canCreateQueue allowNew (srvAuth, srvVersion) (clntAuth, clntVersion) =
   let v = basicAuthSMPVersion
    in allowNew && (isNothing srvAuth || (srvVersion >= v && clntVersion >= v && srvAuth == clntAuth))
 
-testMatrix2 :: ATransport -> (PQSupport -> AgentClient -> AgentClient -> AgentMsgId -> IO ()) -> Spec
+testMatrix2 :: ATransport -> (PQSupport -> Bool -> AgentClient -> AgentClient -> AgentMsgId -> IO ()) -> Spec
 testMatrix2 t runTest = do
-  it "v7" $ withSmpServerV7 t $ runTestCfg2 agentCfgV7 agentCfgV7 3 $ runTest PQSupportOn
-  it "v7 to current" $ withSmpServerV7 t $ runTestCfg2 agentCfgV7 agentCfg 3 $ runTest PQSupportOn
-  it "current to v7" $ withSmpServerV7 t $ runTestCfg2 agentCfg agentCfgV7 3 $ runTest PQSupportOn
-  it "current with v7 server" $ withSmpServerV7 t $ runTestCfg2 agentCfg agentCfg 3 $ runTest PQSupportOn
-  it "current" $ withSmpServer t $ runTestCfg2 agentCfg agentCfg 3 $ runTest PQSupportOn
-  it "prev" $ withSmpServer t $ runTestCfg2 agentCfgVPrev agentCfgVPrev 3 $ runTest PQSupportOff
-  it "prev to current" $ withSmpServer t $ runTestCfg2 agentCfgVPrev agentCfg 3 $ runTest PQSupportOff
-  it "current to prev" $ withSmpServer t $ runTestCfg2 agentCfg agentCfgVPrev 3 $ runTest PQSupportOff
+  it "v8, via proxy" $ withSmpServerProxy t $ runTestCfgServers2 agentProxyCfg agentProxyCfg (initAgentServersProxy SPMAlways SPFProhibit) 3 $ runTest PQSupportOn True
+  it "v7" $ withSmpServerV7 t $ runTestCfg2 agentCfgV7 agentCfgV7 3 $ runTest PQSupportOn False
+  it "v7 to current" $ withSmpServerV7 t $ runTestCfg2 agentCfgV7 agentCfg 3 $ runTest PQSupportOn False
+  it "current to v7" $ withSmpServerV7 t $ runTestCfg2 agentCfg agentCfgV7 3 $ runTest PQSupportOn False
+  it "current with v7 server" $ withSmpServerV7 t $ runTestCfg2 agentCfg agentCfg 3 $ runTest PQSupportOn False
+  it "current" $ withSmpServer t $ runTestCfg2 agentCfg agentCfg 3 $ runTest PQSupportOn False
+  it "prev" $ withSmpServer t $ runTestCfg2 agentCfgVPrev agentCfgVPrev 3 $ runTest PQSupportOff False
+  it "prev to current" $ withSmpServer t $ runTestCfg2 agentCfgVPrev agentCfg 3 $ runTest PQSupportOff False
+  it "current to prev" $ withSmpServer t $ runTestCfg2 agentCfg agentCfgVPrev 3 $ runTest PQSupportOff False
 
-testRatchetMatrix2 :: ATransport -> (PQSupport -> AgentClient -> AgentClient -> AgentMsgId -> IO ()) -> Spec
+testRatchetMatrix2 :: ATransport -> (PQSupport -> Bool -> AgentClient -> AgentClient -> AgentMsgId -> IO ()) -> Spec
 testRatchetMatrix2 t runTest = do
-  it "ratchet next" $ withSmpServerV7 t $ runTestCfg2 agentCfgV7 agentCfgV7 3 $ runTest PQSupportOn
-  it "ratchet next to current" $ withSmpServerV7 t $ runTestCfg2 agentCfgV7 agentCfg 3 $ runTest PQSupportOn
-  it "ratchet current to next" $ withSmpServerV7 t $ runTestCfg2 agentCfg agentCfgV7 3 $ runTest PQSupportOn
-  it "ratchet current" $ withSmpServer t $ runTestCfg2 agentCfg agentCfg 3 $ runTest PQSupportOn
-  it "ratchet prev" $ withSmpServer t $ runTestCfg2 agentCfgRatchetVPrev agentCfgRatchetVPrev 3 $ runTest PQSupportOff
-  it "ratchets prev to current" $ withSmpServer t $ runTestCfg2 agentCfgRatchetVPrev agentCfg 3 $ runTest PQSupportOff
-  it "ratchets current to prev" $ withSmpServer t $ runTestCfg2 agentCfg agentCfgRatchetVPrev 3 $ runTest PQSupportOff
+  it "v8, via proxy" $ withSmpServerProxy t $ runTestCfgServers2 agentProxyCfg agentProxyCfg (initAgentServersProxy SPMAlways SPFProhibit) 3 $ runTest PQSupportOn True
+  it "ratchet next" $ withSmpServerV7 t $ runTestCfg2 agentCfgV7 agentCfgV7 3 $ runTest PQSupportOn False
+  it "ratchet next to current" $ withSmpServerV7 t $ runTestCfg2 agentCfgV7 agentCfg 3 $ runTest PQSupportOn False
+  it "ratchet current to next" $ withSmpServerV7 t $ runTestCfg2 agentCfg agentCfgV7 3 $ runTest PQSupportOn False
+  it "ratchet current" $ withSmpServer t $ runTestCfg2 agentCfg agentCfg 3 $ runTest PQSupportOn False
+  it "ratchet prev" $ withSmpServer t $ runTestCfg2 agentCfgRatchetVPrev agentCfgRatchetVPrev 3 $ runTest PQSupportOff False
+  it "ratchets prev to current" $ withSmpServer t $ runTestCfg2 agentCfgRatchetVPrev agentCfg 3 $ runTest PQSupportOff False
+  it "ratchets current to prev" $ withSmpServer t $ runTestCfg2 agentCfg agentCfgRatchetVPrev 3 $ runTest PQSupportOff False
 
 testServerMatrix2 :: ATransport -> (InitialAgentServers -> IO ()) -> Spec
 testServerMatrix2 t runTest = do
@@ -482,10 +488,14 @@ testServerMatrix2 t runTest = do
   it "2 servers" $ withSmpServer t . withSmpServerOn t testPort2 $ runTest initAgentServers2
 
 runTestCfg2 :: HasCallStack => AgentConfig -> AgentConfig -> AgentMsgId -> (HasCallStack => AgentClient -> AgentClient -> AgentMsgId -> IO ()) -> IO ()
-runTestCfg2 aCfg bCfg baseMsgId runTest =
-  withAgentClientsCfg2 aCfg bCfg $ \a b -> runTest a b baseMsgId
+runTestCfg2 aCfg bCfg = runTestCfgServers2 aCfg bCfg initAgentServers
 {-# INLINE runTestCfg2 #-}
 
+runTestCfgServers2 :: HasCallStack => AgentConfig -> AgentConfig -> InitialAgentServers -> AgentMsgId -> (HasCallStack => AgentClient -> AgentClient -> AgentMsgId -> IO ()) -> IO ()
+runTestCfgServers2 aCfg bCfg servers baseMsgId runTest =
+  withAgentClientsCfgServers2 aCfg bCfg servers $ \a b -> runTest a b baseMsgId
+{-# INLINE runTestCfgServers2 #-}
+
 withAgentClientsCfgServers2 :: HasCallStack => AgentConfig -> AgentConfig -> InitialAgentServers -> (HasCallStack => AgentClient -> AgentClient -> IO ()) -> IO ()
 withAgentClientsCfgServers2 aCfg bCfg servers runTest =
   withAgent 1 aCfg servers testDB $ \a ->
@@ -506,8 +516,8 @@ withAgentClients3 runTest =
     withAgent 3 agentCfg initAgentServers testDB3 $ \c ->
       runTest a b c
 
-runAgentClientTest :: HasCallStack => PQSupport -> AgentClient -> AgentClient -> AgentMsgId -> IO ()
-runAgentClientTest pqSupport alice@AgentClient {} bob baseId =
+runAgentClientTest :: HasCallStack => PQSupport -> Bool -> AgentClient -> AgentClient -> AgentMsgId -> IO ()
+runAgentClientTest pqSupport viaProxy alice@AgentClient {} bob baseId =
   runRight_ $ do
     (bobId, qInfo) <- A.createConnection alice 1 True SCMInvitation Nothing (IKNoPQ pqSupport) SMSubscribe
     aliceId <- A.joinConnection bob 1 Nothing True qInfo "bob's connInfo" pqSupport SMSubscribe
@@ -519,18 +529,19 @@ runAgentClientTest pqSupport alice@AgentClient {} bob baseId =
     get bob ##> ("", aliceId, A.INFO pqSupport "alice's connInfo")
     get bob ##> ("", aliceId, A.CON pqEnc)
     -- message IDs 1 to 3 (or 1 to 4 in v1) get assigned to control messages, so first MSG is assigned ID 4
+    let proxySrv = if viaProxy then Just testSMPServer else Nothing
     1 <- msgId <$> A.sendMessage alice bobId pqEnc SMP.noMsgFlags "hello"
-    get alice ##> ("", bobId, SENT $ baseId + 1)
+    get alice ##> ("", bobId, A.SENT (baseId + 1) proxySrv)
     2 <- msgId <$> A.sendMessage alice bobId pqEnc SMP.noMsgFlags "how are you?"
-    get alice ##> ("", bobId, SENT $ baseId + 2)
+    get alice ##> ("", bobId, A.SENT (baseId + 2) proxySrv)
     get bob =##> \case ("", c, Msg' _ pq "hello") -> c == aliceId && pq == pqEnc; _ -> False
     ackMessage bob aliceId (baseId + 1) Nothing
     get bob =##> \case ("", c, Msg' _ pq "how are you?") -> c == aliceId && pq == pqEnc; _ -> False
     ackMessage bob aliceId (baseId + 2) Nothing
     3 <- msgId <$> A.sendMessage bob aliceId pqEnc SMP.noMsgFlags "hello too"
-    get bob ##> ("", aliceId, SENT $ baseId + 3)
+    get bob ##> ("", aliceId, A.SENT (baseId + 3) proxySrv)
     4 <- msgId <$> A.sendMessage bob aliceId pqEnc SMP.noMsgFlags "message 1"
-    get bob ##> ("", aliceId, SENT $ baseId + 4)
+    get bob ##> ("", aliceId, A.SENT (baseId + 4) proxySrv)
     get alice =##> \case ("", c, Msg' _ pq "hello too") -> c == bobId && pq == pqEnc; _ -> False
     ackMessage alice bobId (baseId + 3) Nothing
     get alice =##> \case ("", c, Msg' _ pq "message 1") -> c == bobId && pq == pqEnc; _ -> False
@@ -633,8 +644,8 @@ testAgentClient3 =
     get c =##> \case ("", connId, Msg "c5") -> connId == aIdForC; _ -> False
     ackMessage c aIdForC 5 Nothing
 
-runAgentClientContactTest :: HasCallStack => PQSupport -> AgentClient -> AgentClient -> AgentMsgId -> IO ()
-runAgentClientContactTest pqSupport alice bob baseId =
+runAgentClientContactTest :: HasCallStack => PQSupport -> Bool -> AgentClient -> AgentClient -> AgentMsgId -> IO ()
+runAgentClientContactTest pqSupport viaProxy alice bob baseId =
   runRight_ $ do
     (_, qInfo) <- A.createConnection alice 1 True SCMContact Nothing (IKNoPQ pqSupport) SMSubscribe
     aliceId <- A.prepareConnectionToJoin bob 1 True qInfo pqSupport
@@ -651,18 +662,19 @@ runAgentClientContactTest pqSupport alice bob baseId =
     get alice ##> ("", bobId, A.CON pqEnc)
     get bob ##> ("", aliceId, A.CON pqEnc)
     -- message IDs 1 to 3 (or 1 to 4 in v1) get assigned to control messages, so first MSG is assigned ID 4
+    let proxySrv = if viaProxy then Just testSMPServer else Nothing
     1 <- msgId <$> A.sendMessage alice bobId pqEnc SMP.noMsgFlags "hello"
-    get alice ##> ("", bobId, SENT $ baseId + 1)
+    get alice ##> ("", bobId, A.SENT (baseId + 1) proxySrv)
     2 <- msgId <$> A.sendMessage alice bobId pqEnc SMP.noMsgFlags "how are you?"
-    get alice ##> ("", bobId, SENT $ baseId + 2)
+    get alice ##> ("", bobId, A.SENT (baseId + 2) proxySrv)
     get bob =##> \case ("", c, Msg' _ pq "hello") -> c == aliceId && pq == pqEnc; _ -> False
     ackMessage bob aliceId (baseId + 1) Nothing
     get bob =##> \case ("", c, Msg' _ pq "how are you?") -> c == aliceId && pq == pqEnc; _ -> False
     ackMessage bob aliceId (baseId + 2) Nothing
     3 <- msgId <$> A.sendMessage bob aliceId pqEnc SMP.noMsgFlags "hello too"
-    get bob ##> ("", aliceId, SENT $ baseId + 3)
+    get bob ##> ("", aliceId, A.SENT (baseId + 3) proxySrv)
     4 <- msgId <$> A.sendMessage bob aliceId pqEnc SMP.noMsgFlags "message 1"
-    get bob ##> ("", aliceId, SENT $ baseId + 4)
+    get bob ##> ("", aliceId, A.SENT (baseId + 4) proxySrv)
     get alice =##> \case ("", c, Msg' _ pq "hello too") -> c == bobId && pq == pqEnc; _ -> False
     ackMessage alice bobId (baseId + 3) Nothing
     get alice =##> \case ("", c, Msg' _ pq "message 1") -> c == bobId && pq == pqEnc; _ -> False
@@ -1503,9 +1515,9 @@ testSuspendingAgentCompleteSending t = withAgentClients2 $ \a b -> do
     liftIO $ suspendAgent b 5000000
 
   withSmpServerStoreLogOn t testPort $ \_ -> runRight_ @AgentErrorType $ do
-    pGet b =##> \case ("", c, APC _ (SENT 5)) -> c == aId; ("", "", APC _ UP {}) -> True; _ -> False
-    pGet b =##> \case ("", c, APC _ (SENT 5)) -> c == aId; ("", "", APC _ UP {}) -> True; _ -> False
-    pGet b =##> \case ("", c, APC _ (SENT 6)) -> c == aId; ("", "", APC _ UP {}) -> True; _ -> False
+    pGet b =##> \case ("", c, APC SAEConn (SENT 5)) -> c == aId; ("", "", APC _ UP {}) -> True; _ -> False
+    pGet b =##> \case ("", c, APC SAEConn (SENT 5)) -> c == aId; ("", "", APC _ UP {}) -> True; _ -> False
+    pGet b =##> \case ("", c, APC SAEConn (SENT 6)) -> c == aId; ("", "", APC _ UP {}) -> True; _ -> False
     ("", "", SUSPENDED) <- nGet b
 
     pGet a =##> \case ("", c, APC _ (Msg "hello too")) -> c == bId; ("", "", APC _ UP {}) -> True; _ -> False
diff --git a/tests/AgentTests/NotificationTests.hs b/tests/AgentTests/NotificationTests.hs
index 3b497c8d4..04b7fc69c 100644
--- a/tests/AgentTests/NotificationTests.hs
+++ b/tests/AgentTests/NotificationTests.hs
@@ -36,6 +36,7 @@ import AgentTests.FunctionalAPITests
     pattern CONF,
     pattern INFO,
     pattern Msg,
+    pattern SENT,
   )
 import Control.Concurrent (ThreadId, killThread, threadDelay)
 import Control.Monad
@@ -55,7 +56,7 @@ import SMPClient (cfg, cfgV7, testPort, testPort2, testStoreLogFile2, withSmpSer
 import Simplex.Messaging.Agent hiding (createConnection, joinConnection, sendMessage)
 import Simplex.Messaging.Agent.Client (ProtocolTestFailure (..), ProtocolTestStep (..), withStore')
 import Simplex.Messaging.Agent.Env.SQLite (AgentConfig, Env (..), InitialAgentServers)
-import Simplex.Messaging.Agent.Protocol hiding (CON, CONF, INFO)
+import Simplex.Messaging.Agent.Protocol hiding (CON, CONF, INFO, SENT)
 import Simplex.Messaging.Agent.Store.SQLite (getSavedNtfToken)
 import qualified Simplex.Messaging.Crypto as C
 import Simplex.Messaging.Encoding.String
diff --git a/tests/CoreTests/BatchingTests.hs b/tests/CoreTests/BatchingTests.hs
index 5a60a1635..caab0637a 100644
--- a/tests/CoreTests/BatchingTests.hs
+++ b/tests/CoreTests/BatchingTests.hs
@@ -281,12 +281,12 @@ randomSUB_ :: (C.AlgorithmI a, C.AuthAlgorithm a) => C.SAlgorithm a -> VersionSM
 randomSUB_ a v sessId = do
   g <- C.newRandom
   rId <- atomically $ C.randomBytes 24 g
-  corrId <- atomically $ CorrId <$> C.randomBytes 24 g
+  nonce@(C.CbNonce corrId) <- atomically $ C.randomCbNonce g
   (rKey, rpKey) <- atomically $ C.generateAuthKeyPair a g
   thAuth_ <- testTHandleAuth v g rKey
   let thParams = testTHandleParams v sessId
-      TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth thParams (corrId, rId, Cmd SRecipient SUB)
-  pure $ (,tToSend) <$> authTransmission thAuth_ (Just rpKey) corrId tForAuth
+      TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth thParams (CorrId corrId, rId, Cmd SRecipient SUB)
+  pure $ (,tToSend) <$> authTransmission thAuth_ (Just rpKey) nonce tForAuth
 
 randomSUBCmd :: ProtocolClient SMPVersion ErrorType BrokerMsg -> IO (PCTransmission ErrorType BrokerMsg)
 randomSUBCmd = randomSUBCmd_ C.SEd25519
@@ -311,13 +311,13 @@ randomSEND_ :: (C.AlgorithmI a, C.AuthAlgorithm a) => C.SAlgorithm a -> VersionS
 randomSEND_ a v sessId len = do
   g <- C.newRandom
   sId <- atomically $ C.randomBytes 24 g
-  corrId <- atomically $ CorrId <$> C.randomBytes 3 g
+  nonce@(C.CbNonce corrId) <- atomically $ C.randomCbNonce g
   (sKey, spKey) <- atomically $ C.generateAuthKeyPair a g
   thAuth_ <- testTHandleAuth v g sKey
   msg <- atomically $ C.randomBytes len g
   let thParams = testTHandleParams v sessId
-      TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth thParams (corrId, sId, Cmd SSender $ SEND noMsgFlags msg)
-  pure $ (,tToSend) <$> authTransmission thAuth_ (Just spKey) corrId tForAuth
+      TransmissionForAuth {tForAuth, tToSend} = encodeTransmissionForAuth thParams (CorrId corrId, sId, Cmd SSender $ SEND noMsgFlags msg)
+  pure $ (,tToSend) <$> authTransmission thAuth_ (Just spKey) nonce tForAuth
 
 testTHandleParams :: VersionSMP -> ByteString -> THandleParams SMPVersion 'TClient
 testTHandleParams v sessionId =
@@ -325,6 +325,7 @@ testTHandleParams v sessionId =
     { sessionId,
       blockSize = smpBlockSize,
       thVersion = v,
+      thServerVRange = supportedServerSMPRelayVRange,
       thAuth = Nothing,
       implySessId = v >= authCmdsSMPVersion,
       batch = True
diff --git a/tests/CoreTests/ProtocolErrorTests.hs b/tests/CoreTests/ProtocolErrorTests.hs
index d574bfb4f..4466c4933 100644
--- a/tests/CoreTests/ProtocolErrorTests.hs
+++ b/tests/CoreTests/ProtocolErrorTests.hs
@@ -2,21 +2,20 @@
 {-# LANGUAGE LambdaCase #-}
 {-# LANGUAGE ScopedTypeVariables #-}
 {-# LANGUAGE StandaloneDeriving #-}
-{-# LANGUAGE TypeApplications #-}
 {-# OPTIONS_GHC -Wno-orphans #-}
 
 module CoreTests.ProtocolErrorTests where
 
-import qualified Data.ByteString.Char8 as B
-import qualified Data.Text as T
-import Data.Text.Encoding (encodeUtf8)
 import GHC.Generics (Generic)
 import Generic.Random (genericArbitraryU)
 import Simplex.FileTransfer.Transport (XFTPErrorType (..))
 import Simplex.Messaging.Agent.Protocol
+import qualified Simplex.Messaging.Agent.Protocol as Agent
+import Simplex.Messaging.Client (ProxyClientError (..))
 import Simplex.Messaging.Encoding
 import Simplex.Messaging.Encoding.String
 import Simplex.Messaging.Protocol (CommandError (..), ErrorType (..))
+import qualified Simplex.Messaging.Protocol as SMP
 import Simplex.Messaging.Transport (HandshakeError (..), TransportError (..))
 import Simplex.RemoteControl.Types (RCErrorType (..))
 import Test.Hspec
@@ -26,20 +25,34 @@ import Test.QuickCheck
 protocolErrorTests :: Spec
 protocolErrorTests = modifyMaxSuccess (const 1000) $ do
   describe "errors parsing / serializing" $ do
-    it "should parse SMP protocol errors" . property $ \(err :: ErrorType) ->
+    it "should parse SMP protocol errors" . property . forAll possibleErrorType $ \err ->
       smpDecode (smpEncode err) == Right err
-    it "should parse SMP agent errors" . property $ \(err :: AgentErrorType) ->
-      errHasSpaces err
-        || strDecode (strEncode err) == Right err
+    it "should parse SMP agent errors" . property . forAll possibleAgentErrorType $ \err ->
+      strDecode (strEncode err) == Right err
   where
-    errHasSpaces = \case
-      BROKER srv (RESPONSE e) -> hasSpaces srv || hasSpaces e
-      BROKER srv _ -> hasSpaces srv
-      SMP srv _ -> hasSpaces srv
-      NTF srv _ -> hasSpaces srv
-      XFTP srv _ -> hasSpaces srv
+    possibleErrorType :: Gen ErrorType
+    possibleErrorType = arbitrary >>= \e -> if skipErrorType e then discard else pure e
+    possibleAgentErrorType :: Gen AgentErrorType
+    possibleAgentErrorType =
+      arbitrary >>= \case
+        BROKER srv _ | hasSpaces srv -> discard
+        SMP srv e | hasSpaces srv || skipErrorType e -> discard
+        NTF srv e | hasSpaces srv || skipErrorType e -> discard
+        XFTP srv _ | hasSpaces srv -> discard
+        Agent.PROXY pxy srv _ | hasSpaces pxy || hasSpaces srv -> discard
+        Agent.PROXY _ _ (ProxyProtocolError e) | skipErrorType e -> discard
+        Agent.PROXY _ _ (ProxyUnexpectedResponse e) | hasUnicode e -> discard
+        Agent.PROXY _ _ (ProxyResponseError e) | skipErrorType e -> discard
+        ok -> pure ok
+    hasSpaces :: String -> Bool
+    hasSpaces = any (== ' ')
+    hasUnicode :: String -> Bool
+    hasUnicode = any (>= '\255')
+    skipErrorType = \case
+      SMP.PROXY (SMP.PROTOCOL e) -> skipErrorType e
+      SMP.PROXY (SMP.BROKER (UNEXPECTED s)) -> hasUnicode s
+      SMP.PROXY (SMP.BROKER (RESPONSE s)) -> hasUnicode s
       _ -> False
-    hasSpaces s = ' ' `B.elem` encodeUtf8 (T.pack s)
 
 deriving instance Generic AgentErrorType
 
@@ -47,6 +60,8 @@ deriving instance Generic CommandErrorType
 
 deriving instance Generic ConnectionErrorType
 
+deriving instance Generic ProxyClientError
+
 deriving instance Generic BrokerErrorType
 
 deriving instance Generic SMPAgentError
@@ -57,6 +72,8 @@ deriving instance Generic ErrorType
 
 deriving instance Generic CommandError
 
+deriving instance Generic SMP.ProxyError
+
 deriving instance Generic TransportError
 
 deriving instance Generic HandshakeError
@@ -71,6 +88,8 @@ instance Arbitrary CommandErrorType where arbitrary = genericArbitraryU
 
 instance Arbitrary ConnectionErrorType where arbitrary = genericArbitraryU
 
+instance Arbitrary ProxyClientError where arbitrary = genericArbitraryU
+
 instance Arbitrary BrokerErrorType where arbitrary = genericArbitraryU
 
 instance Arbitrary SMPAgentError where arbitrary = genericArbitraryU
@@ -81,6 +100,8 @@ instance Arbitrary ErrorType where arbitrary = genericArbitraryU
 
 instance Arbitrary CommandError where arbitrary = genericArbitraryU
 
+instance Arbitrary SMP.ProxyError where arbitrary = genericArbitraryU
+
 instance Arbitrary TransportError where arbitrary = genericArbitraryU
 
 instance Arbitrary HandshakeError where arbitrary = genericArbitraryU
diff --git a/tests/CoreTests/VersionRangeTests.hs b/tests/CoreTests/VersionRangeTests.hs
index cef556376..ff53cc6ca 100644
--- a/tests/CoreTests/VersionRangeTests.hs
+++ b/tests/CoreTests/VersionRangeTests.hs
@@ -6,6 +6,7 @@
 
 module CoreTests.VersionRangeTests where
 
+import Data.Word (Word16)
 import GHC.Generics (Generic)
 import Generic.Random (genericArbitraryU)
 import Simplex.Messaging.Version
@@ -38,6 +39,28 @@ versionRangeTests = modifyMaxSuccess (const 1000) $ do
       (vr 1 3, vr 2 3) `compatible` Just (Version 3)
       (vr 1 3, vr 2 4) `compatible` Just (Version 3)
       (vr 1 2, vr 3 4) `compatible` Nothing
+    it "should choose mutually compatible version range (range intersection)" $ do
+      (vr 1 1, vr 1 1) `compatibleVR` Just (vr 1 1)
+      (vr 1 1, vr 1 2) `compatibleVR` Just (vr 1 1)
+      (vr 1 2, vr 1 2) `compatibleVR` Just (vr 1 2)
+      (vr 1 2, vr 2 3) `compatibleVR` Just (vr 2 2)
+      (vr 1 3, vr 2 3) `compatibleVR` Just (vr 2 3)
+      (vr 1 3, vr 2 4) `compatibleVR` Just (vr 2 3)
+      (vr 1 2, vr 3 4) `compatibleVR` Nothing
+    it "should choose compatible version range with changed max version (capped range)" $ do
+      (vr 1 1, 1) `compatibleVR'` Just (vr 1 1)
+      (vr 1 1, 2) `compatibleVR'` Nothing
+      (vr 1 2, 2) `compatibleVR'` Just (vr 1 2)
+      (vr 1 2, 3) `compatibleVR'` Nothing
+      (vr 1 3, 2) `compatibleVR'` Just (vr 1 2)
+      (vr 1 3, 3) `compatibleVR'` Just (vr 1 3)
+      (vr 1 3, 4) `compatibleVR'` Nothing
+      (vr 2 3, 1) `compatibleVR'` Nothing
+      (vr 2 3, 2) `compatibleVR'` Just (vr 2 2)
+      (vr 2 3, 3) `compatibleVR'` Just (vr 2 3)
+      (vr 2 4, 1) `compatibleVR'` Nothing
+      (vr 2 4, 3) `compatibleVR'` Just (vr 2 3)
+      (vr 2 4, 4) `compatibleVR'` Just (vr 2 4)
     it "should check if version is compatible" $ do
       isCompatible @T (Version 1) (vr 1 2) `shouldBe` True
       isCompatible @T (Version 2) (vr 1 2) `shouldBe` True
@@ -63,3 +86,16 @@ versionRangeTests = modifyMaxSuccess (const 1000) $ do
       case compatibleVersion vr1 vr2 of
         Just (Compatible v') -> Just v' `shouldBe` v
         Nothing -> Nothing `shouldBe` v
+    compatibleVR :: (VersionRange T, VersionRange T) -> Maybe (VersionRange T) -> Expectation
+    (vr1, vr2) `compatibleVR` vr' = do
+      (vr1, vr2) `checkCompatibleVR` vr'
+      (vr2, vr1) `checkCompatibleVR` vr'
+    (vr1, vr2) `checkCompatibleVR` vr' =
+      case compatibleVRange vr1 vr2 of
+        Just (Compatible vr'') -> Just vr'' `shouldBe` vr'
+        Nothing -> Nothing `shouldBe` vr'
+    compatibleVR' :: (VersionRange T, Word16) -> Maybe (VersionRange T) -> Expectation
+    (vr1, v2) `compatibleVR'` vr' =
+      case compatibleVRange' vr1 (Version v2) of
+        Just (Compatible vr'') -> Just vr'' `shouldBe` vr'
+        Nothing -> Nothing `shouldBe` vr'
diff --git a/tests/SMPAgentClient.hs b/tests/SMPAgentClient.hs
index 5ff9197cb..3cf09e5db 100644
--- a/tests/SMPAgentClient.hs
+++ b/tests/SMPAgentClient.hs
@@ -20,7 +20,8 @@ import qualified Database.SQLite.Simple as SQL
 import Network.Socket (ServiceName)
 import NtfClient (ntfTestPort)
 import SMPClient
-  ( serverBracket,
+  ( proxyVRange,
+    serverBracket,
     testKeyHash,
     testPort,
     testPort2,
@@ -34,7 +35,7 @@ import Simplex.Messaging.Agent.RetryInterval
 import Simplex.Messaging.Agent.Server (runSMPAgentBlocking)
 import Simplex.Messaging.Agent.Store.SQLite (MigrationConfirmation (..), SQLiteStore (dbNew))
 import Simplex.Messaging.Agent.Store.SQLite.Common (withTransaction')
-import Simplex.Messaging.Client (ProtocolClientConfig (..), chooseTransportHost, defaultNetworkConfig, defaultSMPClientConfig)
+import Simplex.Messaging.Client (ProtocolClientConfig (..), SMPProxyFallback, SMPProxyMode, chooseTransportHost, defaultNetworkConfig, defaultSMPClientConfig)
 import Simplex.Messaging.Notifications.Client (defaultNTFClientConfig)
 import Simplex.Messaging.Parsers (parseAll)
 import Simplex.Messaging.Protocol (NtfServer, ProtoServerWithAuth)
@@ -198,6 +199,10 @@ initAgentServers =
 initAgentServers2 :: InitialAgentServers
 initAgentServers2 = initAgentServers {smp = userServers [noAuthSrv testSMPServer, noAuthSrv testSMPServer2]}
 
+initAgentServersProxy :: SMPProxyMode -> SMPProxyFallback -> InitialAgentServers
+initAgentServersProxy smpProxyMode smpProxyFallback =
+  initAgentServers {netCfg = (netCfg initAgentServers) {smpProxyMode, smpProxyFallback}}
+
 agentCfg :: AgentConfig
 agentCfg =
   defaultAgentConfig
@@ -217,6 +222,9 @@ agentCfg =
   where
     networkConfig = defaultNetworkConfig {tcpConnectTimeout = 1_000_000, tcpTimeout = 2_000_000}
 
+agentProxyCfg :: AgentConfig
+agentProxyCfg = agentCfg {smpCfg = (smpCfg agentCfg) {serverVRange = proxyVRange}}
+
 fastRetryInterval :: RetryInterval
 fastRetryInterval = defaultReconnectInterval {initialInterval = 50_000}
 
diff --git a/tests/SMPClient.hs b/tests/SMPClient.hs
index ae9baeb3c..441ece34b 100644
--- a/tests/SMPClient.hs
+++ b/tests/SMPClient.hs
@@ -16,7 +16,8 @@ import Control.Monad.Except (runExceptT)
 import Data.ByteString.Char8 (ByteString)
 import Data.List.NonEmpty (NonEmpty)
 import Network.Socket
-import Simplex.Messaging.Client (chooseTransportHost, defaultNetworkConfig)
+import Simplex.Messaging.Client (ProtocolClientConfig (..), chooseTransportHost, defaultNetworkConfig)
+import Simplex.Messaging.Client.Agent (SMPClientAgentConfig (..), defaultSMPClientAgentConfig)
 import qualified Simplex.Messaging.Crypto as C
 import Simplex.Messaging.Encoding
 import Simplex.Messaging.Protocol
@@ -75,8 +76,12 @@ testSMPClient = testSMPClientVR supportedClientSMPRelayVRange
 testSMPClientVR :: Transport c => VersionRangeSMP -> (THandleSMP c 'TClient -> IO a) -> IO a
 testSMPClientVR vr client = do
   Right useHost <- pure $ chooseTransportHost defaultNetworkConfig testHost
+  testSMPClient_ useHost testPort vr client
+
+testSMPClient_ :: Transport c => TransportHost -> ServiceName -> VersionRangeSMP -> (THandleSMP c 'TClient -> IO a) -> IO a
+testSMPClient_ host port vr client = do
   let tcConfig = defaultTransportClientConfig {Client.alpn = clientALPN}
-  runTransportClient tcConfig Nothing useHost testPort (Just testKeyHash) $ \h ->
+  runTransportClient tcConfig Nothing host port (Just testKeyHash) $ \h ->
     runExceptT (smpClientHandshake h Nothing testKeyHash vr) >>= \case
       Right th -> client th
       Left e -> error $ show e
@@ -112,12 +117,28 @@ cfg =
       certificateFile = "tests/fixtures/server.crt",
       smpServerVRange = supportedServerSMPRelayVRange,
       transportConfig = defaultTransportServerConfig {Server.alpn = Just supportedSMPHandshakes},
-      controlPort = Nothing
+      controlPort = Nothing,
+      smpAgentCfg = defaultSMPClientAgentConfig,
+      allowSMPProxy = False
     }
 
 cfgV7 :: ServerConfig
 cfgV7 = cfg {smpServerVRange = mkVersionRange batchCmdsSMPVersion authCmdsSMPVersion}
 
+cfgV8 :: ServerConfig
+cfgV8 = cfg {smpServerVRange = mkVersionRange batchCmdsSMPVersion sendingProxySMPVersion}
+
+proxyCfg :: ServerConfig
+proxyCfg =
+  cfgV7
+    { allowSMPProxy = True,
+      smpServerVRange = mkVersionRange batchCmdsSMPVersion sendingProxySMPVersion,
+      smpAgentCfg = defaultSMPClientAgentConfig {smpCfg = (smpCfg defaultSMPClientAgentConfig) {serverVRange = proxyVRange, agreeSecret = True}}
+    }
+
+proxyVRange :: VersionRangeSMP
+proxyVRange = mkVersionRange batchCmdsSMPVersion sendingProxySMPVersion
+
 withSmpServerStoreMsgLogOn :: HasCallStack => ATransport -> ServiceName -> (HasCallStack => ThreadId -> IO a) -> IO a
 withSmpServerStoreMsgLogOn t = withSmpServerConfigOn t cfg {storeLogFile = Just testStoreLogFile, storeMsgsFile = Just testStoreMsgsFile, serverStatsBackupFile = Just testServerStatsBackupFile}
 
@@ -155,6 +176,9 @@ withSmpServer t = withSmpServerOn t testPort
 withSmpServerV7 :: HasCallStack => ATransport -> IO a -> IO a
 withSmpServerV7 t = withSmpServerConfigOn t cfgV7 testPort . const
 
+withSmpServerProxy :: HasCallStack => ATransport -> IO a -> IO a
+withSmpServerProxy t = withSmpServerConfigOn t proxyCfg testPort . const
+
 runSmpTest :: forall c a. (HasCallStack, Transport c) => (HasCallStack => THandleSMP c 'TClient -> IO a) -> IO a
 runSmpTest test = withSmpServer (transport @c) $ testSMPClient test
 
diff --git a/tests/SMPProxyTests.hs b/tests/SMPProxyTests.hs
new file mode 100644
index 000000000..467700784
--- /dev/null
+++ b/tests/SMPProxyTests.hs
@@ -0,0 +1,203 @@
+{-# LANGUAGE DataKinds #-}
+{-# LANGUAGE DuplicateRecordFields #-}
+{-# LANGUAGE GADTs #-}
+{-# LANGUAGE LambdaCase #-}
+{-# LANGUAGE NamedFieldPuns #-}
+{-# LANGUAGE OverloadedLists #-}
+{-# LANGUAGE OverloadedStrings #-}
+{-# LANGUAGE PatternSynonyms #-}
+{-# LANGUAGE RankNTypes #-}
+{-# LANGUAGE ScopedTypeVariables #-}
+{-# LANGUAGE TupleSections #-}
+{-# LANGUAGE TypeApplications #-}
+
+module SMPProxyTests where
+
+import AgentTests.FunctionalAPITests
+import Control.Monad.Trans.Except (runExceptT)
+import Data.ByteString.Char8 (ByteString)
+import Data.List.NonEmpty (NonEmpty)
+import qualified Data.List.NonEmpty as L
+import SMPAgentClient
+import SMPClient
+import ServerTests (decryptMsgV3, sendRecv)
+import Simplex.Messaging.Agent hiding (createConnection, joinConnection, sendMessage)
+import qualified Simplex.Messaging.Agent as A
+import Simplex.Messaging.Agent.Env.SQLite (AgentConfig (..), InitialAgentServers (..))
+import Simplex.Messaging.Agent.Protocol hiding (CON, CONF, INFO, REQ)
+import qualified Simplex.Messaging.Agent.Protocol as A
+import Simplex.Messaging.Client
+import qualified Simplex.Messaging.Crypto as C
+import Simplex.Messaging.Crypto.Ratchet (pattern PQSupportOn)
+import qualified Simplex.Messaging.Crypto.Ratchet as CR
+import Simplex.Messaging.Protocol as SMP
+import Simplex.Messaging.Server.Env.STM (ServerConfig (..))
+import Simplex.Messaging.Transport
+import Simplex.Messaging.Version (mkVersionRange)
+import Test.Hspec
+import UnliftIO
+
+smpProxyTests :: Spec
+smpProxyTests = do
+  describe "server configuration" $ do
+    it "refuses proxy handshake unless enabled" testNoProxy
+    it "checks basic auth in proxy requests" testProxyAuth
+  describe "proxy requests" $ do
+    describe "bad relay URIs" $ do
+      xit "host not resolved" todo
+      xit "when SMP port blackholed" todo
+      xit "no SMP service at host/port" todo
+      xit "bad SMP fingerprint" todo
+    xit "batching proxy requests" todo
+  describe "deliver message via SMP proxy" $ do
+    let srv1 = SMPServer testHost testPort testKeyHash
+        srv2 = SMPServer testHost testPort2 testKeyHash
+    describe "client API" $ do
+      let maxLen = maxMessageLength sendingProxySMPVersion
+      describe "one server" $ do
+        it "deliver via proxy" . oneServer $ do
+          deliverMessageViaProxy srv1 srv1 C.SEd448 "hello 1" "hello 2"
+      describe "two servers" $ do
+        let proxyServ = srv1
+            relayServ = srv2
+        (msg1, msg2) <- runIO $ do
+          g <- C.newRandom
+          atomically $ (,) <$> C.randomBytes maxLen g <*> C.randomBytes maxLen g
+        it "deliver via proxy" . twoServersFirstProxy $
+          deliverMessageViaProxy proxyServ relayServ C.SEd448 "hello 1" "hello 2"
+        it "max message size, Ed448 keys" . twoServersFirstProxy $
+          deliverMessageViaProxy proxyServ relayServ C.SEd448 msg1 msg2
+        it "max message size, Ed25519 keys" . twoServersFirstProxy $
+          deliverMessageViaProxy proxyServ relayServ C.SEd25519 msg1 msg2
+        it "max message size, X25519 keys" . twoServersFirstProxy $
+          deliverMessageViaProxy proxyServ relayServ C.SX25519 msg1 msg2
+    describe "agent API" $ do
+      describe "one server" $ do
+        it "always via proxy" . oneServer $
+          agentDeliverMessageViaProxy ([srv1], SPMAlways, True) ([srv1], SPMAlways, True) C.SEd448 "hello 1" "hello 2"
+        it "without proxy" . oneServer $
+          agentDeliverMessageViaProxy ([srv1], SPMNever, False) ([srv1], SPMNever, False) C.SEd448 "hello 1" "hello 2"
+      describe "two servers" $ do
+        it "always via proxy" . twoServers $
+          agentDeliverMessageViaProxy ([srv1], SPMAlways, True) ([srv2], SPMAlways, True) C.SEd448 "hello 1" "hello 2"
+        it "both via proxy" . twoServers $
+          agentDeliverMessageViaProxy ([srv1], SPMUnknown, True) ([srv2], SPMUnknown, True) C.SEd448 "hello 1" "hello 2"
+        it "first via proxy" . twoServers $
+          agentDeliverMessageViaProxy ([srv1], SPMUnknown, True) ([srv2], SPMNever, False) C.SEd448 "hello 1" "hello 2"
+        it "without proxy" . twoServers $
+          agentDeliverMessageViaProxy ([srv1], SPMNever, False) ([srv2], SPMNever, False) C.SEd448 "hello 1" "hello 2"
+        it "first via proxy for unknown" . twoServers $
+          agentDeliverMessageViaProxy ([srv1], SPMUnknown, True) ([srv1, srv2], SPMUnknown, False) C.SEd448 "hello 1" "hello 2"
+        it "without proxy with fallback" . twoServers_ proxyCfg cfgV7 $
+          agentDeliverMessageViaProxy ([srv1], SPMUnknown, False) ([srv2], SPMUnknown, False) C.SEd448 "hello 1" "hello 2"
+        it "fails when fallback is prohibited" . twoServers_ proxyCfg cfgV7 $
+          agentViaProxyVersionError
+  where
+    oneServer = withSmpServerConfigOn (transport @TLS) proxyCfg testPort . const
+    twoServers = twoServers_ proxyCfg proxyCfg
+    twoServersFirstProxy = twoServers_ proxyCfg cfgV8
+    twoServers_ cfg1 cfg2 runTest =
+      withSmpServerConfigOn (transport @TLS) cfg1 testPort $ \_ ->
+        withSmpServerConfigOn (transport @TLS) cfg2 testPort2 $ const runTest
+
+deliverMessageViaProxy :: (C.AlgorithmI a, C.AuthAlgorithm a) => SMPServer -> SMPServer -> C.SAlgorithm a -> ByteString -> ByteString -> IO ()
+deliverMessageViaProxy proxyServ relayServ alg msg msg' = do
+  g <- C.newRandom
+  -- set up proxy
+  Right pc <- getProtocolClient g (1, proxyServ, Nothing) defaultSMPClientConfig {serverVRange = mkVersionRange batchCmdsSMPVersion sendingProxySMPVersion} Nothing (\_ -> pure ())
+  THAuthClient {} <- maybe (fail "getProtocolClient returned no thAuth") pure $ thAuth $ thParams pc
+  -- set up relay
+  msgQ <- newTBQueueIO 4
+  Right rc <- getProtocolClient g (2, relayServ, Nothing) defaultSMPClientConfig {serverVRange = mkVersionRange batchCmdsSMPVersion authCmdsSMPVersion} (Just msgQ) (\_ -> pure ())
+  runRight_ $ do
+    -- prepare receiving queue
+    (rPub, rPriv) <- atomically $ C.generateAuthKeyPair alg g
+    (rdhPub, rdhPriv :: C.PrivateKeyX25519) <- atomically $ C.generateKeyPair g
+    QIK {rcvId, sndId, rcvPublicDhKey = srvDh} <- createSMPQueue rc (rPub, rPriv) rdhPub (Just "correct") SMSubscribe
+    let dec = decryptMsgV3 $ C.dh' srvDh rdhPriv
+    -- get proxy session
+    sess <- connectSMPProxiedRelay pc relayServ (Just "correct")
+    -- send via proxy to unsecured queue
+    Right () <- proxySMPMessage pc sess Nothing sndId noMsgFlags msg
+    -- receive 1
+    (_tSess, _v, _sid, _isResp, _entId, Right (SMP.MSG RcvMessage {msgId, msgBody = EncRcvMsgBody encBody})) <- atomically $ readTBQueue msgQ
+    liftIO $ dec msgId encBody `shouldBe` Right msg
+    ackSMPMessage rc rPriv rcvId msgId
+    -- secure queue
+    (sPub, sPriv) <- atomically $ C.generateAuthKeyPair alg g
+    secureSMPQueue rc rPriv rcvId sPub
+    -- send via proxy to secured queue
+    Right () <- proxySMPMessage pc sess (Just sPriv) sndId noMsgFlags msg'
+    -- receive 2
+    (_tSess, _v, _sid, _isResp, _entId, Right (SMP.MSG RcvMessage {msgId = msgId', msgBody = EncRcvMsgBody encBody'})) <- atomically $ readTBQueue msgQ
+    liftIO $ dec msgId' encBody' `shouldBe` Right msg'
+    ackSMPMessage rc rPriv rcvId msgId'
+
+agentDeliverMessageViaProxy :: (C.AlgorithmI a, C.AuthAlgorithm a) => (NonEmpty SMPServer, SMPProxyMode, Bool) -> (NonEmpty SMPServer, SMPProxyMode, Bool) -> C.SAlgorithm a -> ByteString -> ByteString -> IO ()
+agentDeliverMessageViaProxy aTestCfg@(aSrvs, _, aViaProxy) bTestCfg@(bSrvs, _, bViaProxy) alg msg1 msg2 =
+  withAgent 1 aCfg (servers aTestCfg) testDB $ \alice ->
+    withAgent 2 aCfg (servers bTestCfg) testDB2 $ \bob -> runRight_ $ do
+      (bobId, qInfo) <- A.createConnection alice 1 True SCMInvitation Nothing (CR.IKNoPQ PQSupportOn) SMSubscribe
+      aliceId <- A.joinConnection bob 1 Nothing True qInfo "bob's connInfo" PQSupportOn SMSubscribe
+      ("", _, A.CONF confId pqSup' _ "bob's connInfo") <- get alice
+      liftIO $ pqSup' `shouldBe` PQSupportOn
+      allowConnection alice bobId confId "alice's connInfo"
+      let pqEnc = CR.PQEncOn
+      get alice ##> ("", bobId, A.CON pqEnc)
+      get bob ##> ("", aliceId, A.INFO PQSupportOn "alice's connInfo")
+      get bob ##> ("", aliceId, A.CON pqEnc)
+      -- message IDs 1 to 3 (or 1 to 4 in v1) get assigned to control messages, so first MSG is assigned ID 4
+      let aProxySrv = if aViaProxy then Just $ L.head aSrvs else Nothing
+      1 <- msgId <$> A.sendMessage alice bobId pqEnc noMsgFlags msg1
+      get alice ##> ("", bobId, A.SENT (baseId + 1) aProxySrv)
+      2 <- msgId <$> A.sendMessage alice bobId pqEnc noMsgFlags msg2
+      get alice ##> ("", bobId, A.SENT (baseId + 2) aProxySrv)
+      get bob =##> \case ("", c, Msg' _ pq msg1') -> c == aliceId && pq == pqEnc && msg1 == msg1'; _ -> False
+      ackMessage bob aliceId (baseId + 1) Nothing
+      get bob =##> \case ("", c, Msg' _ pq msg2') -> c == aliceId && pq == pqEnc && msg2 == msg2'; _ -> False
+      ackMessage bob aliceId (baseId + 2) Nothing
+      let bProxySrv = if bViaProxy then Just $ L.head bSrvs else Nothing
+      3 <- msgId <$> A.sendMessage bob aliceId pqEnc noMsgFlags msg1
+      get bob ##> ("", aliceId, A.SENT (baseId + 3) bProxySrv)
+      4 <- msgId <$> A.sendMessage bob aliceId pqEnc noMsgFlags msg2
+      get bob ##> ("", aliceId, A.SENT (baseId + 4) bProxySrv)
+      get alice =##> \case ("", c, Msg' _ pq msg1') -> c == bobId && pq == pqEnc && msg1 == msg1'; _ -> False
+      ackMessage alice bobId (baseId + 3) Nothing
+      get alice =##> \case ("", c, Msg' _ pq msg2') -> c == bobId && pq == pqEnc && msg2 == msg2'; _ -> False
+      ackMessage alice bobId (baseId + 4) Nothing
+  where
+    baseId = 3
+    msgId = subtract baseId . fst
+    aCfg = agentProxyCfg {sndAuthAlg = C.AuthAlg alg, rcvAuthAlg = C.AuthAlg alg}
+    servers (srvs, smpProxyMode, _) = (initAgentServersProxy smpProxyMode SPFAllow) {smp = userServers $ L.map noAuthSrv srvs}
+
+agentViaProxyVersionError :: IO ()
+agentViaProxyVersionError =
+  withAgent 1 agentProxyCfg (servers [SMPServer testHost testPort testKeyHash]) testDB $ \alice -> do
+    Left (A.BROKER _ (TRANSPORT TEVersion)) <-
+      withAgent 2 agentProxyCfg (servers [SMPServer testHost testPort2 testKeyHash]) testDB2 $ \bob -> runExceptT $ do
+        (_bobId, qInfo) <- A.createConnection alice 1 True SCMInvitation Nothing (CR.IKNoPQ PQSupportOn) SMSubscribe
+        A.joinConnection bob 1 Nothing True qInfo "bob's connInfo" PQSupportOn SMSubscribe
+    pure ()
+  where
+    servers srvs = (initAgentServersProxy SPMUnknown SPFProhibit) {smp = userServers $ L.map noAuthSrv srvs}
+
+testNoProxy :: IO ()
+testNoProxy = do
+  withSmpServerConfigOn (transport @TLS) cfg testPort2 $ \_ -> do
+    testSMPClient_ "127.0.0.1" testPort2 proxyVRange $ \(th :: THandleSMP TLS 'TClient) -> do
+      (_, _, (_corrId, _entityId, reply)) <- sendRecv th (Nothing, "0", "", PRXY testSMPServer Nothing)
+      reply `shouldBe` Right (SMP.ERR $ SMP.PROXY SMP.BASIC_AUTH)
+
+testProxyAuth :: IO ()
+testProxyAuth = do
+  withSmpServerConfigOn (transport @TLS) proxyCfgAuth testPort $ \_ -> do
+    testSMPClient_ "127.0.0.1" testPort proxyVRange $ \(th :: THandleSMP TLS 'TClient) -> do
+      (_, _s, (_corrId, _entityId, reply)) <- sendRecv th (Nothing, "0", "", PRXY testSMPServer2 $ Just "wrong")
+      reply `shouldBe` Right (SMP.ERR $ SMP.PROXY SMP.BASIC_AUTH)
+  where
+    proxyCfgAuth = proxyCfg {newQueueBasicAuth = Just "correct"}
+
+todo :: IO ()
+todo = do
+  fail "TODO"
diff --git a/tests/ServerTests.hs b/tests/ServerTests.hs
index b4c40cd99..b0ed67913 100644
--- a/tests/ServerTests.hs
+++ b/tests/ServerTests.hs
@@ -183,12 +183,12 @@ testCreateSecure (ATransport t) =
       Resp "dabc" _ err5 <- sendRecv s ("", "dabc", sId, _SEND "hello")
       (err5, ERR AUTH) #== "rejects unsigned SEND"
 
-      let maxAllowedMessage = B.replicate maxMessageLength '-'
+      let maxAllowedMessage = B.replicate (maxMessageLength currentClientSMPRelayVersion) '-'
       Resp "bcda" _ OK <- signSendRecv s sKey ("bcda", sId, _SEND maxAllowedMessage)
       Resp "" _ (Msg mId3 msg3) <- tGet1 r
       (dec mId3 msg3, Right maxAllowedMessage) #== "delivers message of max size"
 
-      let biggerMessage = B.replicate (maxMessageLength + 1) '-'
+      let biggerMessage = B.replicate (maxMessageLength currentClientSMPRelayVersion + 1) '-'
       Resp "bcda" _ (ERR LARGE_MSG) <- signSendRecv s sKey ("bcda", sId, _SEND biggerMessage)
       pure ()
 
@@ -931,8 +931,6 @@ instance Eq C.ASignature where
     Just Refl -> s == s'
     _ -> False
 
-deriving instance Eq (C.Signature a)
-
 syntaxTests :: ATransport -> Spec
 syntaxTests (ATransport t) = do
   it "unknown command" $ ("", "abcd", "1234", ('H', 'E', 'L', 'L', 'O')) >#> ("", "abcd", "1234", ERR $ CMD UNKNOWN)
diff --git a/tests/Test.hs b/tests/Test.hs
index aebceb22d..f9fb2a2c0 100644
--- a/tests/Test.hs
+++ b/tests/Test.hs
@@ -21,6 +21,7 @@ import GHC.IO.Exception (IOException (..))
 import qualified GHC.IO.Exception as IOException
 import NtfServerTests (ntfServerTests)
 import RemoteControl (remoteControlTests)
+import SMPProxyTests (smpProxyTests)
 import ServerTests
 import Simplex.Messaging.Transport (TLS, Transport (..))
 import Simplex.Messaging.Transport.WebSockets (WS)
@@ -59,6 +60,7 @@ main = do
         describe "SMP server via WebSockets" $ serverTests (transport @WS)
         describe "Notifications server" $ ntfServerTests (transport @TLS)
         describe "SMP client agent" $ agentTests (transport @TLS)
+        describe "SMP proxy" smpProxyTests
         describe "XFTP" $ do
           describe "XFTP server" xftpServerTests
           describe "XFTP file description" fileDescriptionTests
diff --git a/tests/XFTPClient.hs b/tests/XFTPClient.hs
index 5f38cc639..0152625a8 100644
--- a/tests/XFTPClient.hs
+++ b/tests/XFTPClient.hs
@@ -14,6 +14,7 @@ import Simplex.FileTransfer.Client
 import Simplex.FileTransfer.Description
 import Simplex.FileTransfer.Server (runXFTPServerBlocking)
 import Simplex.FileTransfer.Server.Env (XFTPServerConfig (..), defaultFileExpiration, defaultInactiveClientExpiration, supportedXFTPhandshakes)
+import Simplex.FileTransfer.Transport (supportedFileServerVRange)
 import Simplex.Messaging.Protocol (XFTPServer)
 import Simplex.Messaging.Transport (ALPN)
 import Simplex.Messaging.Transport.Server
@@ -118,6 +119,7 @@ testXFTPServerConfig_ alpn =
       caCertificateFile = "tests/fixtures/ca.crt",
       privateKeyFile = "tests/fixtures/server.key",
       certificateFile = "tests/fixtures/server.crt",
+      xftpServerVRange = supportedFileServerVRange,
       logStatsInterval = Nothing,
       logStatsStartTime = 0,
       serverStatsLogFile = "tests/tmp/xftp-server-stats.daily.log",