diff --git a/simplex-chat.cabal b/simplex-chat.cabal
index 916cceb589..4b95a7600e 100644
--- a/simplex-chat.cabal
+++ b/simplex-chat.cabal
@@ -137,6 +137,7 @@ library
       Simplex.Chat.Migrations.M20240214_redirect_file_id
       Simplex.Chat.Migrations.M20240222_app_settings
       Simplex.Chat.Migrations.M20240226_users_restrict
+      Simplex.Chat.Migrations.M20240228_pq
       Simplex.Chat.Mobile
       Simplex.Chat.Mobile.File
       Simplex.Chat.Mobile.Shared
diff --git a/src/Simplex/Chat.hs b/src/Simplex/Chat.hs
index 2f6eb0c910..e59f465dac 100644
--- a/src/Simplex/Chat.hs
+++ b/src/Simplex/Chat.hs
@@ -243,6 +243,7 @@ newChatController
     encryptLocalFiles <- newTVarIO False
     tempDirectory <- newTVarIO Nothing
     contactMergeEnabled <- newTVarIO True
+    pqExperimentalEnabled <- newTVarIO False
     pure
       ChatController
         { firstTime,
@@ -278,7 +279,8 @@ newChatController
           encryptLocalFiles,
           tempDirectory,
           logFilePath = logFile,
-          contactMergeEnabled
+          contactMergeEnabled,
+          pqExperimentalEnabled
         }
     where
       configServers :: DefaultAgentServers
@@ -589,6 +591,9 @@ processChatCommand' vr = \case
   SetContactMergeEnabled onOff -> do
     asks contactMergeEnabled >>= atomically . (`writeTVar` onOff)
     ok_
+  APISetPQEnabled onOff -> do
+    asks pqExperimentalEnabled >>= atomically . (`writeTVar` onOff)
+    ok_
   APIExportArchive cfg -> checkChatStopped $ exportArchive cfg >> ok_
   ExportArchive -> do
     ts <- liftIO getCurrentTime
@@ -1581,6 +1586,7 @@ processChatCommand' vr = \case
     -- [incognito] generate incognito profile for group membership
     incognitoProfile <- if incognito then Just <$> liftIO generateRandomProfile else pure Nothing
     groupInfo <- withStore $ \db -> createNewGroup db vr gVar user gProfile incognitoProfile
+    -- TODO [pq] create CISndGroupE2EEInfo (would affect tests)
     pure $ CRGroupCreated user groupInfo
   NewGroup incognito gProfile -> withUser $ \User {userId} ->
     processChatCommand $ APINewGroup userId incognito gProfile
@@ -1801,7 +1807,7 @@ processChatCommand' vr = \case
     case memberConn m of
       Just mConn -> do
         let msg = XGrpDirectInv cReq msgContent_
-        (sndMsg, _) <- sendDirectMessage mConn msg $ GroupId groupId
+        (sndMsg, _) <- sendDirectMessage mConn pqDummyFlag msg $ GroupId groupId
         withStore' $ \db -> setContactGrpInvSent db ct True
         let ct' = ct {contactGrpInvSent = True}
         forM_ msgContent_ $ \mc -> do
@@ -2208,7 +2214,7 @@ processChatCommand' vr = \case
         ctSndMsg ChangedProfileContact {mergedProfile', conn = Connection {connId}} = (ConnectionId connId, XInfo mergedProfile')
         ctMsgReq :: ChangedProfileContact -> Either ChatError SndMessage -> Either ChatError MsgReq
         ctMsgReq ChangedProfileContact {conn} = fmap $ \SndMessage {msgId, msgBody} ->
-          (conn, MsgFlags {notification = hasNotification XInfo_}, msgBody, msgId)
+          (conn, pqDummyFlag, MsgFlags {notification = hasNotification XInfo_}, msgBody, msgId)
     updateContactPrefs :: User -> Contact -> Preferences -> m ChatResponse
     updateContactPrefs _ ct@Contact {activeConn = Nothing} _ = throwChatError $ CEContactNotActive ct
     updateContactPrefs user@User {userId} ct@Contact {activeConn = Just Connection {customUserProfileId}, userPreferences = contactUserPrefs} contactUserPrefs'
@@ -2299,9 +2305,18 @@ processChatCommand' vr = \case
         groupMemberId <- getGroupMemberIdByName db user groupId groupMemberName
         pure (groupId, groupMemberId)
     sendGrpInvitation :: User -> Contact -> GroupInfo -> GroupMember -> ConnReqInvitation -> m ()
-    sendGrpInvitation user ct@Contact {localDisplayName} GroupInfo {groupId, groupProfile, membership} GroupMember {groupMemberId, memberId, memberRole = memRole} cReq = do
+    sendGrpInvitation user ct@Contact {localDisplayName} gInfo@GroupInfo {groupId, groupProfile, membership} GroupMember {groupMemberId, memberId, memberRole = memRole} cReq = do
+      currentMemCount <- withStore' $ \db -> getGroupCurrentMembersCount db user gInfo
       let GroupMember {memberRole = userRole, memberId = userMemberId} = membership
-          groupInv = GroupInvitation (MemberIdRole userMemberId userRole) (MemberIdRole memberId memRole) cReq groupProfile Nothing
+          groupInv =
+            GroupInvitation
+              { fromMember = MemberIdRole userMemberId userRole,
+                invitedMember = MemberIdRole memberId memRole,
+                connRequest = cReq,
+                groupProfile,
+                groupLinkId = Nothing,
+                groupSize = Just currentMemCount
+              }
       (msg, _) <- sendDirectContactMessage ct $ XGrpInv groupInv
       let content = CISndGroupInvitation (CIGroupInvitation {groupId, groupMemberId, localDisplayName, groupProfile, status = CIGISPending}) memRole
       ci <- saveSndChatItem user (CDDirectSnd ct) msg content
@@ -2733,7 +2748,7 @@ acceptFileReceive user@User {userId} RcvFileTransfer {fileId, xftpRcvFile, fileI
           GroupMember {activeConn} <- withStoreCtx (Just "acceptFileReceive, getGroupMember") $ \db -> getGroupMember db user groupId memId
           case activeConn of
             Just conn -> do
-              acceptFile CFCreateConnFileInvGroup $ \msg -> void $ sendDirectMessage conn msg $ GroupId groupId
+              acceptFile CFCreateConnFileInvGroup $ \msg -> void $ sendDirectMessage conn pqDummyFlag msg $ GroupId groupId
             _ -> throwChatError $ CEFileInternal "member connection not active"
         _ -> throwChatError $ CEFileInternal "invalid chat ref for file transfer"
   where
@@ -2856,9 +2871,18 @@ acceptGroupJoinRequestAsync
   incognitoProfile = do
     gVar <- asks random
     (groupMemberId, memberId) <- withStore $ \db -> createAcceptedMember db gVar user gInfo ucr gLinkMemRole
+    currentMemCount <- withStore' $ \db -> getGroupCurrentMembersCount db user gInfo
     let Profile {displayName} = profileToSendOnAccept user incognitoProfile True
         GroupMember {memberRole = userRole, memberId = userMemberId} = membership
-        msg = XGrpLinkInv $ GroupLinkInvitation (MemberIdRole userMemberId userRole) displayName (MemberIdRole memberId gLinkMemRole) groupProfile
+        msg =
+          XGrpLinkInv $
+            GroupLinkInvitation
+              { fromMember = MemberIdRole userMemberId userRole,
+                fromMemberName = displayName,
+                invitedMember = MemberIdRole memberId gLinkMemRole,
+                groupProfile,
+                groupSize = Just currentMemCount
+              }
     subMode <- chatReadVar subscriptionMode
     connIds <- agentAcceptContactAsync user True invId msg subMode
     withStore $ \db -> do
@@ -3313,7 +3337,7 @@ processAgentMsgSndFile _corrId aFileId msg =
                             useMember _ = Nothing
                         sendToMember :: (ValidFileDescription 'FRecipient, (Connection, SndFileTransfer)) -> m ()
                         sendToMember (rfd, (conn, sft)) =
-                          void $ sendFileDescription sft rfd sharedMsgId $ \msg' -> sendDirectMessage conn msg' $ GroupId groupId
+                          void $ sendFileDescription sft rfd sharedMsgId $ \msg' -> sendDirectMessage conn pqDummyFlag msg' $ GroupId groupId
                     _ -> pure ()
                 _ -> pure () -- TODO error?
         SFERR e
@@ -3490,6 +3514,11 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
                   sendXGrpMemInv hostConnId (Just directConnReq) xGrpMemIntroCont
               CRContactUri _ -> throwChatError $ CECommandError "unexpected ConnectionRequestUri type"
         MSG msgMeta _msgFlags msgBody -> do
+          -- TODO [pq] same for other direct connection events;
+          -- TODO      use ct', conn' downstream;
+          -- TODO      pqAgentDummy - would be returned in agent event
+          let pqAgentDummy = False
+          (_ct', _conn') <- updateContactPQ ct conn pqAgentDummy
           checkIntegrityCreateItem (CDDirectRcv ct) msgMeta
           cmdId <- createAckCmd conn
           withAckMessage agentConnId cmdId msgMeta $ do
@@ -3674,8 +3703,17 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
                 where
                   sendGrpInvitation :: Contact -> GroupMember -> Maybe GroupLinkId -> m ()
                   sendGrpInvitation ct GroupMember {memberId, memberRole = memRole} groupLinkId = do
+                    currentMemCount <- withStore' $ \db -> getGroupCurrentMembersCount db user gInfo
                     let GroupMember {memberRole = userRole, memberId = userMemberId} = membership
-                        groupInv = GroupInvitation (MemberIdRole userMemberId userRole) (MemberIdRole memberId memRole) cReq groupProfile groupLinkId
+                        groupInv =
+                          GroupInvitation
+                            { fromMember = MemberIdRole userMemberId userRole,
+                              invitedMember = MemberIdRole memberId memRole,
+                              connRequest = cReq,
+                              groupProfile,
+                              groupLinkId = groupLinkId,
+                              groupSize = Just currentMemCount
+                            }
                     (_msg, _) <- sendDirectContactMessage ct $ XGrpInv groupInv
                     -- we could link chat item with sent group invitation message (_msg)
                     createInternalChatItem user (CDGroupRcv gInfo m) (CIRcvGroupEvent RGEInvitedViaGroupLink) Nothing
@@ -3729,6 +3767,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
         case memberCategory m of
           GCHostMember -> do
             toView $ CRUserJoinedGroup user gInfo {membership = membership {memberStatus = GSMemConnected}} m {memberStatus = GSMemConnected}
+            -- TODO [pq] create CIRcvGroupE2EEInfo (would affect tests)
             createGroupFeatureItems gInfo m
             let GroupInfo {groupProfile = GroupProfile {description}} = gInfo
             memberConnectedChatItem gInfo m
@@ -3750,7 +3789,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
               sendXGrpLinkMem = do
                 let profileMode = ExistingIncognito <$> incognitoMembershipProfile gInfo
                     profileToSend = profileToSendOnAccept user profileMode True
-                void $ sendDirectMessage conn (XGrpLinkMem profileToSend) (GroupId groupId)
+                void $ sendDirectMessage conn pqDummyFlag (XGrpLinkMem profileToSend) (GroupId groupId)
               sendIntroductions members = do
                 intros <- withStore' $ \db -> createIntroductions db (maxVersion vr) members m
                 shuffledIntros <- liftIO $ shuffleIntros intros
@@ -3776,7 +3815,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
                   isAdmin GroupMemberIntro {reMember = GroupMember {memberRole}} = memberRole >= GRAdmin
                   hasPicture GroupMemberIntro {reMember = GroupMember {memberProfile = LocalProfile {image}}} = isJust image
               processIntro intro@GroupMemberIntro {introId} = do
-                void $ sendDirectMessage conn (memberIntro $ reMember intro) (GroupId groupId)
+                void $ sendDirectMessage conn pqDummyFlag (memberIntro $ reMember intro) (GroupId groupId)
                 withStore' $ \db -> updateIntroStatus db introId GMIntroSent
               sendHistory =
                 when (isCompatibleRange (memberChatVRange' m) batchSendVRange) $ do
@@ -3875,12 +3914,12 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
                   forM_ (invitedByGroupMemberId membership) $ \hostId -> do
                     host <- withStore $ \db -> getGroupMember db user groupId hostId
                     forM_ (memberConn host) $ \hostConn ->
-                      void $ sendDirectMessage hostConn (XGrpMemCon memberId) (GroupId groupId)
+                      void $ sendDirectMessage hostConn pqDummyFlag (XGrpMemCon memberId) (GroupId groupId)
                 GCPostMember ->
                   forM_ (invitedByGroupMemberId m) $ \invitingMemberId -> do
                     im <- withStore $ \db -> getGroupMember db user groupId invitingMemberId
                     forM_ (memberConn im) $ \imConn ->
-                      void $ sendDirectMessage imConn (XGrpMemCon memberId) (GroupId groupId)
+                      void $ sendDirectMessage imConn pqDummyFlag (XGrpMemCon memberId) (GroupId groupId)
                 _ -> messageWarning "sendXGrpMemCon: member category GCPreMember or GCPostMember is expected"
       MSG msgMeta _msgFlags msgBody -> do
         checkIntegrityCreateItem (CDGroupRcv gInfo m) msgMeta
@@ -4113,7 +4152,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
                     case activeConn of
                       Just gMemberConn -> do
                         sharedMsgId <- withStore $ \db -> getSharedMsgIdByFileId db userId fileId
-                        void $ sendDirectMessage gMemberConn (XFileAcptInv sharedMsgId (Just fileInvConnReq) fileName) $ GroupId groupId
+                        void $ sendDirectMessage gMemberConn pqDummyFlag (XFileAcptInv sharedMsgId (Just fileInvConnReq) fileName) $ GroupId groupId
                       _ -> throwChatError $ CECommandError "no GroupMember activeConn"
                   _ -> throwChatError $ CECommandError "no grpMemberId"
                 _ -> throwChatError $ CECommandError "unexpected cmdFunction"
@@ -4357,7 +4396,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
         else sendProbe . Probe =<< liftIO (encodedRandomBytes gVar 32)
       where
         sendProbe :: Probe -> m ()
-        sendProbe probe = void $ sendDirectMessage conn (XInfoProbe probe) (GroupId groupId)
+        sendProbe probe = void $ sendDirectMessage conn pqDummyFlag (XInfoProbe probe) (GroupId groupId)
 
     sendProbeHashes :: [ContactOrMember] -> Probe -> Int64 -> m ()
     sendProbeHashes cgms probe probeId =
@@ -4371,7 +4410,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
         sendProbeHash (COMGroupMember GroupMember {activeConn = Nothing}) = pure ()
         sendProbeHash cgm@(COMGroupMember m@GroupMember {groupId, activeConn = Just conn}) =
           when (memberCurrent m) $ do
-            void $ sendDirectMessage conn (XInfoProbeCheck probeHash) (GroupId groupId)
+            void $ sendDirectMessage conn pqDummyFlag (XInfoProbeCheck probeHash) (GroupId groupId)
             withStore' $ \db -> createSentProbeHash db userId probeId cgm
 
     messageWarning :: Text -> m ()
@@ -5056,7 +5095,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
           case cgm2 of
             COMContact c2@Contact {profile = p2}
               | memberCurrent m1 && isNothing memberContactId && profilesMatch p1 p2 -> do
-                  void $ sendDirectMessage conn (XInfoProbeOk probe) (GroupId groupId)
+                  void $ sendDirectMessage conn pqDummyFlag (XInfoProbeOk probe) (GroupId groupId)
                   COMContact <$$> associateMemberAndContact c2 m1
               | otherwise -> messageWarning "probeMatch ignored: profiles don't match or member already has contact or member not current" >> pure Nothing
             COMGroupMember _ -> messageWarning "probeMatch ignored: members are not matched with members" >> pure Nothing
@@ -5257,6 +5296,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
         XInfo p -> do
           let contactUsed = connDirect activeConn
           ct <- withStore $ \db -> createDirectContact db user conn' p contactUsed
+          -- TODO [pq] create CIRcvDirectE2EEInfo here?
           toView $ CRContactConnecting user ct
           pure conn'
         XGrpLinkInv glInv -> do
@@ -5312,7 +5352,7 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
     sendXGrpMemInv hostConnId directConnReq XGrpMemIntroCont {groupId, groupMemberId, memberId, groupConnReq} = do
       hostConn <- withStore $ \db -> getConnectionById db user hostConnId
       let msg = XGrpMemInv memberId IntroInvitation {groupConnReq, directConnReq}
-      void $ sendDirectMessage hostConn msg (GroupId groupId)
+      void $ sendDirectMessage hostConn pqDummyFlag msg (GroupId groupId)
       withStore' $ \db -> updateGroupMemberStatusById db userId groupMemberId GSMemIntroInvited
 
     xGrpMemInv :: GroupInfo -> GroupMember -> MemberId -> IntroInvitation -> m ()
@@ -5667,6 +5707,24 @@ processAgentMessageConn vr user@User {userId} corrId agentConnId agentMessage =
               toView $ CRChatItemStatusUpdated user (AChatItem SCTGroup SMDSnd (GroupChat gInfo) chatItem)
         _ -> pure ()
 
+    -- TODO [pq] track rcv and snd flags separately
+    updateContactPQ :: Contact -> Connection -> PQFlag -> m (Contact, Connection)
+    updateContactPQ ct conn@Connection {connId, pqEnabled} pqEnabled' =
+      flip catchChatError (const $ pure (ct, conn)) $ case (pqEnabled, pqEnabled') of
+        (Nothing, False) -> pure (ct, conn)
+        (Nothing, True) -> updatePQ $ CIRcvDirectE2EEInfo (E2EEInfo pqEnabled')
+        (Just b, b')
+          | b' /= b -> updatePQ $ CIRcvConnEvent (RCEPQEnabled pqEnabled')
+          | otherwise -> pure (ct, conn)
+      where
+        updatePQ ciContent = do
+          withStore' $ \db -> updateConnPQEnabled db connId pqEnabled'
+          let conn' = conn {pqEnabled = Just pqEnabled'} :: Connection
+              ct' = ct {activeConn = Just conn'} :: Contact
+          createInternalChatItem user (CDDirectRcv ct') ciContent Nothing
+          toView $ CRContactPQEnabled user ct' pqEnabled'
+          pure (ct', conn')
+
 metaBrokerTs :: MsgMeta -> UTCTime
 metaBrokerTs MsgMeta {broker = (_, brokerTs)} = brokerTs
 
@@ -5705,7 +5763,7 @@ sendDirectFileInline ct ft sharedMsgId = do
 
 sendMemberFileInline :: ChatMonad m => GroupMember -> Connection -> FileTransferMeta -> SharedMsgId -> m ()
 sendMemberFileInline m@GroupMember {groupId} conn ft sharedMsgId = do
-  msgDeliveryId <- sendFileInline_ ft sharedMsgId $ \msg -> sendDirectMessage conn msg $ GroupId groupId
+  msgDeliveryId <- sendFileInline_ ft sharedMsgId $ \msg -> sendDirectMessage conn pqDummyFlag msg $ GroupId groupId
   withStore' $ \db -> updateSndGroupFTDelivery db m conn ft msgDeliveryId
 
 sendFileInline_ :: ChatMonad m => FileTransferMeta -> SharedMsgId -> (ChatMsgEvent 'Binary -> m (SndMessage, Int64)) -> m Int64
@@ -5855,7 +5913,7 @@ cancelSndFileTransfer user@User {userId} ft@SndFileTransfer {fileId, connId, age
       when sendCancel $ case fileInline of
         Just _ -> do
           (sharedMsgId, conn) <- withStore $ \db -> (,) <$> getSharedMsgIdByFileId db userId fileId <*> getConnectionById db user connId
-          void . sendDirectMessage conn (BFileChunk sharedMsgId FileChunkCancel) $ ConnectionId connId
+          void . sendDirectMessage conn pqDummyFlag (BFileChunk sharedMsgId FileChunkCancel) $ ConnectionId connId
         _ -> withAgent $ \a -> void . sendMessage a acId SMP.noMsgFlags $ smpEncode FileChunkCancel
       pure fileConnId
     fileConnId = if isNothing fileInline then Just acId else Nothing
@@ -5896,7 +5954,9 @@ deleteOrUpdateMemberRecord user@User {userId} member =
 sendDirectContactMessage :: (MsgEncodingI e, ChatMonad m) => Contact -> ChatMsgEvent e -> m (SndMessage, Int64)
 sendDirectContactMessage ct chatMsgEvent = do
   conn@Connection {connId} <- liftEither $ contactSendConn_ ct
-  sendDirectMessage conn chatMsgEvent (ConnectionId connId)
+  -- TODO [pq] look up pqExperimentalEnabled on every send to pass flag to agent apis
+  pq <- readTVarIO =<< asks pqExperimentalEnabled
+  sendDirectMessage conn pq chatMsgEvent (ConnectionId connId)
 
 contactSendConn_ :: Contact -> Either ChatError Connection
 contactSendConn_ ct@Contact {activeConn} = case activeConn of
@@ -5909,11 +5969,11 @@ contactSendConn_ ct@Contact {activeConn} = case activeConn of
   where
     err = Left . ChatError
 
-sendDirectMessage :: (MsgEncodingI e, ChatMonad m) => Connection -> ChatMsgEvent e -> ConnOrGroupId -> m (SndMessage, Int64)
-sendDirectMessage conn chatMsgEvent connOrGroupId = do
+sendDirectMessage :: (MsgEncodingI e, ChatMonad m) => Connection -> PQFlag -> ChatMsgEvent e -> ConnOrGroupId -> m (SndMessage, Int64)
+sendDirectMessage conn pq chatMsgEvent connOrGroupId = do
   when (connDisabled conn) $ throwChatError (CEConnectionDisabled conn)
   msg@SndMessage {msgId, msgBody} <- createSndMessage chatMsgEvent connOrGroupId
-  (msg,) <$> deliverMessage conn (toCMEventTag chatMsgEvent) msgBody msgId
+  (msg,) <$> deliverMessage conn pq (toCMEventTag chatMsgEvent) msgBody msgId
 
 createSndMessage :: (MsgEncodingI e, ChatMonad m) => ChatMsgEvent e -> ConnOrGroupId -> m SndMessage
 createSndMessage chatMsgEvent connOrGroupId =
@@ -5957,35 +6017,44 @@ directMessage chatMsgEvent = do
     ECMEncoded encodedBody -> pure encodedBody
     ECMLarge -> throwChatError $ CEException "large message"
 
-deliverMessage :: ChatMonad m => Connection -> CMEventTag e -> MsgBody -> MessageId -> m Int64
-deliverMessage conn cmEventTag msgBody msgId = do
+deliverMessage :: ChatMonad m => Connection -> PQFlag -> CMEventTag e -> MsgBody -> MessageId -> m Int64
+deliverMessage conn pq cmEventTag msgBody msgId = do
   let msgFlags = MsgFlags {notification = hasNotification cmEventTag}
-  deliverMessage' conn msgFlags msgBody msgId
+  deliverMessage' conn pq msgFlags msgBody msgId
 
-deliverMessage' :: ChatMonad m => Connection -> MsgFlags -> MsgBody -> MessageId -> m Int64
-deliverMessage' conn msgFlags msgBody msgId =
-  deliverMessages [(conn, msgFlags, msgBody, msgId)] >>= \case
+deliverMessage' :: ChatMonad m => Connection -> PQFlag -> MsgFlags -> MsgBody -> MessageId -> m Int64
+deliverMessage' conn pq msgFlags msgBody msgId =
+  deliverMessages [(conn, pq, msgFlags, msgBody, msgId)] >>= \case
     [r] -> liftEither r
     rs -> throwChatError $ CEInternalError $ "deliverMessage: expected 1 result, got " <> show (length rs)
 
-type MsgReq = (Connection, MsgFlags, MsgBody, MessageId)
+type MsgReq = (Connection, PQFlag, MsgFlags, MsgBody, MessageId)
+
+-- TODO [pq] remove, replace in all places with actual flag / pqOff in groups
+pqDummyFlag :: PQFlag
+pqDummyFlag = False
+
+-- TODO remove in 5.7 (used for groups)
+pqOff :: PQFlag
+pqOff = False
 
 deliverMessages :: ChatMonad' m => [MsgReq] -> m [Either ChatError Int64]
 deliverMessages = deliverMessagesB . map Right
 
 deliverMessagesB :: ChatMonad' m => [Either ChatError MsgReq] -> m [Either ChatError Int64]
 deliverMessagesB msgReqs = do
+  -- TODO [pq] pass _pqFlag to sendMessagesB
   sent <- zipWith prepareBatch msgReqs <$> withAgent' (`sendMessagesB` map toAgent msgReqs)
   withStoreBatch $ \db -> map (bindRight $ createDelivery db) sent
   where
     toAgent = \case
-      Right (conn, msgFlags, msgBody, _msgId) -> Right (aConnId conn, msgFlags, msgBody)
+      Right (conn, _pqFlag, msgFlags, msgBody, _msgId) -> Right (aConnId conn, msgFlags, msgBody)
       Left _ce -> Left (AP.INTERNAL "ChatError, skip") -- as long as it is Left, the agent batchers should just step over it
     prepareBatch (Right req) (Right ar) = Right (req, ar)
     prepareBatch (Left ce) _ = Left ce -- restore original ChatError
     prepareBatch _ (Left ae) = Left $ ChatErrorAgent ae Nothing
     createDelivery :: DB.Connection -> (MsgReq, AgentMsgId) -> IO (Either ChatError Int64)
-    createDelivery db ((Connection {connId}, _, _, msgId), agentMsgId) =
+    createDelivery db ((Connection {connId}, _, _, _, msgId), agentMsgId) =
       Right <$> createSndMsgDelivery db (SndMsgDelivery {connId, agentMsgId}) msgId
 
 sendGroupMessage :: (MsgEncodingI e, ChatMonad m) => User -> GroupInfo -> [GroupMember] -> ChatMsgEvent e -> m (SndMessage, [GroupMember])
@@ -6016,7 +6085,7 @@ sendGroupMessage' user GroupInfo {groupId} members chatMsgEvent = do
   recipientMembers <- liftIO $ shuffleMembers (filter memberCurrent members)
   let msgFlags = MsgFlags {notification = hasNotification $ toCMEventTag chatMsgEvent}
       (toSend, pending) = foldr addMember ([], []) recipientMembers
-      msgReqs = map (\(_, conn) -> (conn, msgFlags, msgBody, msgId)) toSend
+      msgReqs = map (\(_, conn) -> (conn, pqOff, msgFlags, msgBody, msgId)) toSend
   delivered <- deliverMessages msgReqs
   let errors = lefts delivered
   unless (null errors) $ toView $ CRChatErrors (Just user) errors
@@ -6075,7 +6144,7 @@ sendGroupMemberMessage user m@GroupMember {groupMemberId} chatMsgEvent groupId i
   where
     messageMember :: SndMessage -> m ()
     messageMember SndMessage {msgId, msgBody} = forM_ (memberSendAction chatMsgEvent [m] m) $ \case
-      MSASend conn -> deliverMessage conn (toCMEventTag chatMsgEvent) msgBody msgId >> postDeliver
+      MSASend conn -> deliverMessage conn pqDummyFlag (toCMEventTag chatMsgEvent) msgBody msgId >> postDeliver
       MSAPending -> withStore' $ \db -> createPendingGroupMessage db groupMemberId msgId introId_
 
 sendPendingGroupMessages :: ChatMonad m => User -> GroupMember -> Connection -> m ()
@@ -6086,7 +6155,7 @@ sendPendingGroupMessages user GroupMember {groupMemberId, localDisplayName} conn
     processPendingMessage pgm `catchChatError` (toView . CRChatError (Just user))
   where
     processPendingMessage PendingGroupMessage {msgId, cmEventTag = ACMEventTag _ tag, msgBody, introId_} = do
-      void $ deliverMessage conn tag msgBody msgId
+      void $ deliverMessage conn pqDummyFlag tag msgBody msgId
       withStore' $ \db -> deletePendingGroupMessage db groupMemberId msgId
       case tag of
         XGrpMemFwd_ -> case introId_ of
@@ -6120,7 +6189,7 @@ saveGroupRcvMsg user groupId authorMember conn@Connection {connId} agentMsgMeta
         ChatErrorStore (SEDuplicateGroupMessage _ _ _ (Just forwardedByGroupMemberId)) -> do
           fm <- withStore $ \db -> getGroupMember db user groupId forwardedByGroupMemberId
           forM_ (memberConn fm) $ \fmConn ->
-            void $ sendDirectMessage fmConn (XGrpMemCon amMemId) (GroupId groupId)
+            void $ sendDirectMessage fmConn pqDummyFlag (XGrpMemCon amMemId) (GroupId groupId)
           throwError e
         _ -> throwError e
   pure (am', conn', msg)
@@ -6136,7 +6205,7 @@ saveGroupFwdRcvMsg user groupId forwardingMember refAuthorMember@GroupMember {me
         am@GroupMember {memberId = amMemberId} <- withStore $ \db -> getGroupMember db user groupId authorGroupMemberId
         if sameMemberId refMemberId am
           then forM_ (memberConn forwardingMember) $ \fmConn ->
-            void $ sendDirectMessage fmConn (XGrpMemCon amMemberId) (GroupId groupId)
+            void $ sendDirectMessage fmConn pqDummyFlag (XGrpMemCon amMemberId) (GroupId groupId)
           else toView $ CRMessageError user "error" "saveGroupFwdRcvMsg: referenced author member id doesn't match message member id"
         throwError e
       _ -> throwError e
@@ -6533,6 +6602,7 @@ chatCommandP =
       "/remote_hosts_folder " *> (SetRemoteHostsFolder <$> filePath),
       "/_files_encrypt " *> (APISetEncryptLocalFiles <$> onOffP),
       "/contact_merge " *> (SetContactMergeEnabled <$> onOffP),
+      "/_pq " *> (APISetPQEnabled <$> onOffP),
       "/_db export " *> (APIExportArchive <$> jsonP),
       "/db export" $> ExportArchive,
       "/_db import " *> (APIImportArchive <$> jsonP),
diff --git a/src/Simplex/Chat/Controller.hs b/src/Simplex/Chat/Controller.hs
index c482825e18..4b6c45002b 100644
--- a/src/Simplex/Chat/Controller.hs
+++ b/src/Simplex/Chat/Controller.hs
@@ -206,7 +206,8 @@ data ChatController = ChatController
     encryptLocalFiles :: TVar Bool,
     tempDirectory :: TVar (Maybe FilePath),
     logFilePath :: Maybe FilePath,
-    contactMergeEnabled :: TVar Bool
+    contactMergeEnabled :: TVar Bool,
+    pqExperimentalEnabled :: TVar Bool -- TODO remove in 5.7
   }
 
 data HelpSection = HSMain | HSFiles | HSGroups | HSContacts | HSMyAddress | HSIncognito | HSMarkdown | HSMessages | HSRemote | HSSettings | HSDatabase
@@ -243,6 +244,7 @@ data ChatCommand
   | SetRemoteHostsFolder FilePath
   | APISetEncryptLocalFiles Bool
   | SetContactMergeEnabled Bool
+  | APISetPQEnabled Bool
   | APIExportArchive ArchiveConfig
   | ExportArchive
   | APIImportArchive ArchiveConfig
@@ -697,6 +699,7 @@ data ChatResponse
   | CRRemoteCtrlSessionCode {remoteCtrl_ :: Maybe RemoteCtrlInfo, sessionCode :: Text}
   | CRRemoteCtrlConnected {remoteCtrl :: RemoteCtrlInfo}
   | CRRemoteCtrlStopped {rcsState :: RemoteCtrlSessionState, rcStopReason :: RemoteCtrlStopReason}
+  | CRContactPQEnabled {user :: User, contact :: Contact, pqEnabled :: Bool}
   | CRSQLResult {rows :: [Text]}
   | CRSlowSQLQueries {chatQueries :: [SlowSQLQuery], agentQueries :: [SlowSQLQuery]}
   | CRDebugLocks {chatLockName :: Maybe String, agentLocks :: AgentLocks}
diff --git a/src/Simplex/Chat/Messages/CIContent.hs b/src/Simplex/Chat/Messages/CIContent.hs
index a79eb0d952..f156d62581 100644
--- a/src/Simplex/Chat/Messages/CIContent.hs
+++ b/src/Simplex/Chat/Messages/CIContent.hs
@@ -139,13 +139,23 @@ data CIContent (d :: MsgDirection) where
   CISndModerated :: CIContent 'MDSnd
   CIRcvModerated :: CIContent 'MDRcv
   CIRcvBlocked :: CIContent 'MDRcv
+  CISndDirectE2EEInfo :: E2EEInfo -> CIContent 'MDSnd
+  CIRcvDirectE2EEInfo :: E2EEInfo -> CIContent 'MDRcv
+  CISndGroupE2EEInfo :: E2EEInfo -> CIContent 'MDSnd -- when new group is created
+  CIRcvGroupE2EEInfo :: E2EEInfo -> CIContent 'MDRcv -- when enabled with some member
   CIInvalidJSON :: Text -> CIContent d -- this is also used for logical database errors, e.g. SEBadChatItem
+
 -- ^ This type is used both in API and in DB, so we use different JSON encodings for the database and for the API
 -- ! ^ Nested sum types also have to use different encodings for database and API
 -- ! ^ to avoid breaking cross-platform compatibility, see RcvGroupEvent and SndGroupEvent
 
 deriving instance Show (CIContent d)
 
+data E2EEInfo = E2EEInfo
+  { pqEnabled :: Bool
+  }
+  deriving (Eq, Show)
+
 ciMsgContent :: CIContent d -> Maybe MsgContent
 ciMsgContent = \case
   CISndMsgContent mc -> Just mc
@@ -195,6 +205,8 @@ ciRequiresAttention content = case msgDirection @d of
     CIRcvGroupFeatureRejected _ -> True
     CIRcvModerated -> True
     CIRcvBlocked -> False
+    CIRcvDirectE2EEInfo _ -> False
+    CIRcvGroupE2EEInfo _ -> False
     CIInvalidJSON _ -> False
 
 newtype DBMsgErrorType = DBME MsgErrorType
@@ -250,8 +262,24 @@ ciContentToText = \case
   CISndModerated -> ciModeratedText
   CIRcvModerated -> ciModeratedText
   CIRcvBlocked -> "blocked"
+  CISndDirectE2EEInfo e2eeInfo -> directE2EEInfoToText e2eeInfo
+  CIRcvDirectE2EEInfo e2eeInfo -> directE2EEInfoToText e2eeInfo
+  CISndGroupE2EEInfo e2eeInfo -> groupE2EEInfoToText e2eeInfo
+  CIRcvGroupE2EEInfo e2eeInfo -> groupE2EEInfoToText e2eeInfo
   CIInvalidJSON _ -> "invalid content JSON"
 
+directE2EEInfoToText :: E2EEInfo -> Text
+directE2EEInfoToText E2EEInfo {pqEnabled}
+  | pqEnabled = "This conversation is protected by quantum resistant end-to-end encryption. It has perfect forward secrecy, repudiation and quantum resistant break-in recovery."
+  | otherwise = e2eeInfoNoPQText
+
+groupE2EEInfoToText :: E2EEInfo -> Text
+groupE2EEInfoToText _e2eeInfo = e2eeInfoNoPQText
+
+e2eeInfoNoPQText :: Text
+e2eeInfoNoPQText =
+  "This conversation is protected by end-to-end encryption with perfect forward secrecy, repudiation and break-in recovery."
+
 ciGroupInvitationToText :: CIGroupInvitation -> GroupMemberRole -> Text
 ciGroupInvitationToText CIGroupInvitation {groupProfile = GroupProfile {displayName, fullName}} role =
   "invitation to join group " <> displayName <> optionalFullName displayName fullName <> " as " <> (decodeLatin1 . strEncode $ role)
@@ -295,6 +323,9 @@ rcvConnEventToText = \case
     SPCompleted -> "changed address for you"
   RCERatchetSync syncStatus -> ratchetSyncStatusToText syncStatus
   RCEVerificationCodeReset -> "security code changed"
+  RCEPQEnabled enabled
+    | enabled -> "post-quantum encryption enabled"
+    | otherwise -> "post-quantum encryption disabled"
 
 ratchetSyncStatusToText :: RatchetSyncState -> Text
 ratchetSyncStatusToText = \case
@@ -382,6 +413,10 @@ data JSONCIContent
   | JCISndModerated
   | JCIRcvModerated
   | JCIRcvBlocked
+  | JCISndDirectE2EEInfo {e2eeInfo :: E2EEInfo}
+  | JCIRcvDirectE2EEInfo {e2eeInfo :: E2EEInfo}
+  | JCISndGroupE2EEInfo {e2eeInfo :: E2EEInfo}
+  | JCIRcvGroupE2EEInfo {e2eeInfo :: E2EEInfo}
   | JCIInvalidJSON {direction :: MsgDirection, json :: Text}
 
 jsonCIContent :: forall d. MsgDirectionI d => CIContent d -> JSONCIContent
@@ -412,6 +447,10 @@ jsonCIContent = \case
   CISndModerated -> JCISndModerated
   CIRcvModerated -> JCIRcvModerated
   CIRcvBlocked -> JCIRcvBlocked
+  CISndDirectE2EEInfo e2eeInfo -> JCISndDirectE2EEInfo e2eeInfo
+  CIRcvDirectE2EEInfo e2eeInfo -> JCIRcvDirectE2EEInfo e2eeInfo
+  CISndGroupE2EEInfo e2eeInfo -> JCISndGroupE2EEInfo e2eeInfo
+  CIRcvGroupE2EEInfo e2eeInfo -> JCIRcvGroupE2EEInfo e2eeInfo
   CIInvalidJSON json -> JCIInvalidJSON (toMsgDirection $ msgDirection @d) json
 
 aciContentJSON :: JSONCIContent -> ACIContent
@@ -442,6 +481,10 @@ aciContentJSON = \case
   JCISndModerated -> ACIContent SMDSnd CISndModerated
   JCIRcvModerated -> ACIContent SMDRcv CIRcvModerated
   JCIRcvBlocked -> ACIContent SMDRcv CIRcvBlocked
+  JCISndDirectE2EEInfo {e2eeInfo} -> ACIContent SMDSnd $ CISndDirectE2EEInfo e2eeInfo
+  JCIRcvDirectE2EEInfo {e2eeInfo} -> ACIContent SMDRcv $ CIRcvDirectE2EEInfo e2eeInfo
+  JCISndGroupE2EEInfo {e2eeInfo} -> ACIContent SMDSnd $ CISndGroupE2EEInfo e2eeInfo
+  JCIRcvGroupE2EEInfo {e2eeInfo} -> ACIContent SMDRcv $ CIRcvGroupE2EEInfo e2eeInfo
   JCIInvalidJSON dir json -> case fromMsgDirection dir of
     AMsgDirection d -> ACIContent d $ CIInvalidJSON json
 
@@ -473,6 +516,10 @@ data DBJSONCIContent
   | DBJCISndModerated
   | DBJCIRcvModerated
   | DBJCIRcvBlocked
+  | DBJCISndDirectE2EEInfo {e2eeInfo :: E2EEInfo}
+  | DBJCIRcvDirectE2EEInfo {e2eeInfo :: E2EEInfo}
+  | DBJCISndGroupE2EEInfo {e2eeInfo :: E2EEInfo}
+  | DBJCIRcvGroupE2EEInfo {e2eeInfo :: E2EEInfo}
   | DBJCIInvalidJSON {direction :: MsgDirection, json :: Text}
 
 dbJsonCIContent :: forall d. MsgDirectionI d => CIContent d -> DBJSONCIContent
@@ -503,6 +550,10 @@ dbJsonCIContent = \case
   CISndModerated -> DBJCISndModerated
   CIRcvModerated -> DBJCIRcvModerated
   CIRcvBlocked -> DBJCIRcvBlocked
+  CISndDirectE2EEInfo e2eeInfo -> DBJCISndDirectE2EEInfo e2eeInfo
+  CIRcvDirectE2EEInfo e2eeInfo -> DBJCIRcvDirectE2EEInfo e2eeInfo
+  CISndGroupE2EEInfo e2eeInfo -> DBJCISndGroupE2EEInfo e2eeInfo
+  CIRcvGroupE2EEInfo e2eeInfo -> DBJCIRcvGroupE2EEInfo e2eeInfo
   CIInvalidJSON json -> DBJCIInvalidJSON (toMsgDirection $ msgDirection @d) json
 
 aciContentDBJSON :: DBJSONCIContent -> ACIContent
@@ -533,6 +584,10 @@ aciContentDBJSON = \case
   DBJCISndModerated -> ACIContent SMDSnd CISndModerated
   DBJCIRcvModerated -> ACIContent SMDRcv CIRcvModerated
   DBJCIRcvBlocked -> ACIContent SMDRcv CIRcvBlocked
+  DBJCISndDirectE2EEInfo e2eeInfo -> ACIContent SMDSnd $ CISndDirectE2EEInfo e2eeInfo
+  DBJCIRcvDirectE2EEInfo e2eeInfo -> ACIContent SMDRcv $ CIRcvDirectE2EEInfo e2eeInfo
+  DBJCISndGroupE2EEInfo e2eeInfo -> ACIContent SMDSnd $ CISndGroupE2EEInfo e2eeInfo
+  DBJCIRcvGroupE2EEInfo e2eeInfo -> ACIContent SMDRcv $ CIRcvGroupE2EEInfo e2eeInfo
   DBJCIInvalidJSON dir json -> case fromMsgDirection dir of
     AMsgDirection d -> ACIContent d $ CIInvalidJSON json
 
@@ -558,6 +613,8 @@ ciCallInfoText status duration = case status of
   CISCallEnded -> "ended " <> durationText duration
   CISCallError -> "error"
 
+$(JQ.deriveJSON defaultJSON ''E2EEInfo)
+
 $(JQ.deriveJSON (enumJSON $ dropPrefix "MDE") ''MsgDecryptError)
 
 $(JQ.deriveJSON (enumJSON $ dropPrefix "CIGIS") ''CIGroupInvitationStatus)
@@ -626,4 +683,8 @@ toCIContentTag ciContent = case ciContent of
   CISndModerated -> "sndModerated"
   CIRcvModerated -> "rcvModerated"
   CIRcvBlocked -> "rcvBlocked"
+  CISndDirectE2EEInfo _ -> "sndDirectE2EEInfo"
+  CIRcvDirectE2EEInfo _ -> "rcvDirectE2EEInfo"
+  CISndGroupE2EEInfo _ -> "sndGroupE2EEInfo"
+  CIRcvGroupE2EEInfo _ -> "rcvGroupE2EEInfo"
   CIInvalidJSON _ -> "invalidJSON"
diff --git a/src/Simplex/Chat/Messages/CIContent/Events.hs b/src/Simplex/Chat/Messages/CIContent/Events.hs
index 05417a2e14..f0ff321118 100644
--- a/src/Simplex/Chat/Messages/CIContent/Events.hs
+++ b/src/Simplex/Chat/Messages/CIContent/Events.hs
@@ -42,6 +42,7 @@ data RcvConnEvent
   = RCESwitchQueue {phase :: SwitchPhase}
   | RCERatchetSync {syncStatus :: RatchetSyncState}
   | RCEVerificationCodeReset
+  | RCEPQEnabled {enabled :: Bool}
   deriving (Show)
 
 data SndConnEvent
diff --git a/src/Simplex/Chat/Migrations/M20240228_pq.hs b/src/Simplex/Chat/Migrations/M20240228_pq.hs
new file mode 100644
index 0000000000..a72d8915bb
--- /dev/null
+++ b/src/Simplex/Chat/Migrations/M20240228_pq.hs
@@ -0,0 +1,18 @@
+{-# LANGUAGE QuasiQuotes #-}
+
+module Simplex.Chat.Migrations.M20240228_pq where
+
+import Database.SQLite.Simple (Query)
+import Database.SQLite.Simple.QQ (sql)
+
+m20240228_pq :: Query
+m20240228_pq =
+  [sql|
+ALTER TABLE connections ADD COLUMN pq_enabled INTEGER;
+|]
+
+down_m20240228_pq :: Query
+down_m20240228_pq =
+  [sql|
+ALTER TABLE connections DROP COLUMN pq_enabled;
+|]
diff --git a/src/Simplex/Chat/Migrations/chat_schema.sql b/src/Simplex/Chat/Migrations/chat_schema.sql
index 98b9cfcc12..2ebfa87623 100644
--- a/src/Simplex/Chat/Migrations/chat_schema.sql
+++ b/src/Simplex/Chat/Migrations/chat_schema.sql
@@ -277,6 +277,7 @@ CREATE TABLE connections(
   peer_chat_max_version INTEGER NOT NULL DEFAULT 1,
   to_subscribe INTEGER DEFAULT 0 NOT NULL,
   contact_conn_initiated INTEGER NOT NULL DEFAULT 0,
+  pq_enabled INTEGER,
   FOREIGN KEY(snd_file_id, connection_id)
   REFERENCES snd_files(file_id, connection_id)
   ON DELETE CASCADE
diff --git a/src/Simplex/Chat/Store/Connections.hs b/src/Simplex/Chat/Store/Connections.hs
index fdc3703219..0e4ea5c286 100644
--- a/src/Simplex/Chat/Store/Connections.hs
+++ b/src/Simplex/Chat/Store/Connections.hs
@@ -60,7 +60,8 @@ getConnectionEntity db vr user@User {userId, userContactId} agentConnId = do
           db
           [sql|
             SELECT connection_id, agent_conn_id, conn_level, via_contact, via_user_contact_link, via_group_link, group_link_id, custom_user_profile_id,
-              conn_status, conn_type, contact_conn_initiated, local_alias, contact_id, group_member_id, snd_file_id, rcv_file_id, user_contact_link_id, created_at, security_code, security_code_verified_at, auth_err_counter,
+              conn_status, conn_type, contact_conn_initiated, local_alias, contact_id, group_member_id, snd_file_id, rcv_file_id, user_contact_link_id,
+              created_at, security_code, security_code_verified_at, pq_enabled, auth_err_counter,
               peer_chat_min_version, peer_chat_max_version
             FROM connections
             WHERE user_id = ? AND agent_conn_id = ?
diff --git a/src/Simplex/Chat/Store/Direct.hs b/src/Simplex/Chat/Store/Direct.hs
index b844317593..2ba940d007 100644
--- a/src/Simplex/Chat/Store/Direct.hs
+++ b/src/Simplex/Chat/Store/Direct.hs
@@ -173,7 +173,7 @@ getContactByConnReqHash db user@User {userId} cReqHash =
           cp.preferences, ct.user_preferences, ct.created_at, ct.updated_at, ct.chat_ts, ct.contact_group_member_id, ct.contact_grp_inv_sent,
           -- Connection
           c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id, c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias,
-          c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+          c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
           c.peer_chat_min_version, c.peer_chat_max_version
         FROM contacts ct
         JOIN contact_profiles cp ON ct.contact_profile_id = cp.contact_profile_id
@@ -569,7 +569,7 @@ createOrUpdateContactRequest db user@User {userId} userContactLinkId invId (Vers
               cp.preferences, ct.user_preferences, ct.created_at, ct.updated_at, ct.chat_ts, ct.contact_group_member_id, ct.contact_grp_inv_sent,
               -- Connection
               c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id, c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias,
-              c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+              c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
               c.peer_chat_min_version, c.peer_chat_max_version
             FROM contacts ct
             JOIN contact_profiles cp ON ct.contact_profile_id = cp.contact_profile_id
@@ -734,7 +734,7 @@ getContact_ db user@User {userId} contactId deleted =
           cp.preferences, ct.user_preferences, ct.created_at, ct.updated_at, ct.chat_ts, ct.contact_group_member_id, ct.contact_grp_inv_sent,
           -- Connection
           c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id, c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias,
-          c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+          c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
           c.peer_chat_min_version, c.peer_chat_max_version
         FROM contacts ct
         JOIN contact_profiles cp ON ct.contact_profile_id = cp.contact_profile_id
@@ -787,7 +787,8 @@ getContactConnections db userId Contact {contactId} =
         db
         [sql|
           SELECT c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id,
-            c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+            c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id,
+            c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
             c.peer_chat_min_version, c.peer_chat_max_version
           FROM connections c
           JOIN contacts ct ON ct.contact_id = c.contact_id
@@ -804,7 +805,8 @@ getConnectionById db User {userId} connId = ExceptT $ do
       db
       [sql|
         SELECT connection_id, agent_conn_id, conn_level, via_contact, via_user_contact_link, via_group_link, group_link_id, custom_user_profile_id,
-          conn_status, conn_type, contact_conn_initiated, local_alias, contact_id, group_member_id, snd_file_id, rcv_file_id, user_contact_link_id, created_at, security_code, security_code_verified_at, auth_err_counter,
+          conn_status, conn_type, contact_conn_initiated, local_alias, contact_id, group_member_id, snd_file_id, rcv_file_id, user_contact_link_id,
+          created_at, security_code, security_code_verified_at, pq_enabled, auth_err_counter,
           peer_chat_min_version, peer_chat_max_version
         FROM connections
         WHERE user_id = ? AND connection_id = ?
diff --git a/src/Simplex/Chat/Store/Groups.hs b/src/Simplex/Chat/Store/Groups.hs
index d82cc7570f..8ccec82ddf 100644
--- a/src/Simplex/Chat/Store/Groups.hs
+++ b/src/Simplex/Chat/Store/Groups.hs
@@ -193,7 +193,8 @@ getGroupLinkConnection db User {userId} groupInfo@GroupInfo {groupId} =
       db
       [sql|
         SELECT c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id,
-          c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+          c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id,
+          c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
           c.peer_chat_min_version, c.peer_chat_max_version
         FROM connections c
         JOIN user_contact_links uc ON c.user_contact_link_id = uc.user_contact_link_id
@@ -278,7 +279,8 @@ getGroupAndMember db User {userId, userContactId} groupMemberId vr =
           m.group_member_id, m.group_id, m.member_id, m.peer_chat_min_version, m.peer_chat_max_version, m.member_role, m.member_category, m.member_status, m.show_messages, m.member_restriction,
           m.invited_by, m.invited_by_group_member_id, m.local_display_name, m.contact_id, m.contact_profile_id, p.contact_profile_id, p.display_name, p.full_name, p.image, p.contact_link, p.local_alias, p.preferences,
           c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id,
-          c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+          c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id,
+          c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
           c.peer_chat_min_version, c.peer_chat_max_version
         FROM group_members m
         JOIN contact_profiles p ON p.contact_profile_id = COALESCE(m.member_profile_id, m.contact_profile_id)
@@ -685,7 +687,8 @@ groupMemberQuery =
       m.group_member_id, m.group_id, m.member_id, m.peer_chat_min_version, m.peer_chat_max_version, m.member_role, m.member_category, m.member_status, m.show_messages, m.member_restriction,
       m.invited_by, m.invited_by_group_member_id, m.local_display_name, m.contact_id, m.contact_profile_id, p.contact_profile_id, p.display_name, p.full_name, p.image, p.contact_link, p.local_alias, p.preferences,
       c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id,
-      c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+      c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id,
+      c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
       c.peer_chat_min_version, c.peer_chat_max_version
     FROM group_members m
     JOIN contact_profiles p ON p.contact_profile_id = COALESCE(m.member_profile_id, m.contact_profile_id)
@@ -1289,7 +1292,8 @@ getViaGroupMember db vr User {userId, userContactId} Contact {contactId} =
           m.group_member_id, m.group_id, m.member_id, m.peer_chat_min_version, m.peer_chat_max_version, m.member_role, m.member_category, m.member_status, m.show_messages, m.member_restriction,
           m.invited_by, m.invited_by_group_member_id, m.local_display_name, m.contact_id, m.contact_profile_id, p.contact_profile_id, p.display_name, p.full_name, p.image, p.contact_link, p.local_alias, p.preferences,
           c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id,
-          c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+          c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id,
+          c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
           c.peer_chat_min_version, c.peer_chat_max_version
         FROM group_members m
         JOIN contacts ct ON ct.contact_id = m.contact_id
@@ -1909,7 +1913,27 @@ createMemberContact
           :. (minV, maxV, currentTs, currentTs, subMode == SMOnlyCreate)
       )
     connId <- insertedRowId db
-    let ctConn = Connection {connId, agentConnId = AgentConnId acId, peerChatVRange, connType = ConnContact, contactConnInitiated = True, entityId = Just contactId, viaContact = Nothing, viaUserContactLink = Nothing, viaGroupLink = False, groupLinkId = Nothing, customUserProfileId, connLevel, connStatus = ConnNew, localAlias = "", createdAt = currentTs, connectionCode = Nothing, authErrCounter = 0}
+    let ctConn =
+          Connection
+            { connId,
+              agentConnId = AgentConnId acId,
+              peerChatVRange,
+              connType = ConnContact,
+              contactConnInitiated = True,
+              entityId = Just contactId,
+              viaContact = Nothing,
+              viaUserContactLink = Nothing,
+              viaGroupLink = False,
+              groupLinkId = Nothing,
+              customUserProfileId,
+              connLevel,
+              connStatus = ConnNew,
+              localAlias = "",
+              createdAt = currentTs,
+              connectionCode = Nothing,
+              pqEnabled = Nothing,
+              authErrCounter = 0
+            }
         mergedPreferences = contactUserPreferences user userPreferences preferences $ connIncognito ctConn
     pure Contact {contactId, localDisplayName, profile = memberProfile, activeConn = Just ctConn, viaGroup = Nothing, contactUsed = True, contactStatus = CSActive, chatSettings = defaultChatSettings, userPreferences, mergedPreferences, createdAt = currentTs, updatedAt = currentTs, chatTs = Just currentTs, contactGroupMemberId = Just groupMemberId, contactGrpInvSent = False}
 
@@ -2018,7 +2042,27 @@ createMemberContactConn_
       )
     connId <- insertedRowId db
     setCommandConnId db user cmdId connId
-    pure Connection {connId, agentConnId = AgentConnId acId, peerChatVRange, connType = ConnContact, contactConnInitiated = False, entityId = Just contactId, viaContact = Nothing, viaUserContactLink = Nothing, viaGroupLink = False, groupLinkId = Nothing, customUserProfileId, connLevel, connStatus = ConnJoined, localAlias = "", createdAt = currentTs, connectionCode = Nothing, authErrCounter = 0}
+    pure
+      Connection
+        { connId,
+          agentConnId = AgentConnId acId,
+          peerChatVRange,
+          connType = ConnContact,
+          contactConnInitiated = False,
+          entityId = Just contactId,
+          viaContact = Nothing,
+          viaUserContactLink = Nothing,
+          viaGroupLink = False,
+          groupLinkId = Nothing,
+          customUserProfileId,
+          connLevel,
+          connStatus = ConnJoined,
+          localAlias = "",
+          createdAt = currentTs,
+          connectionCode = Nothing,
+          pqEnabled = Nothing,
+          authErrCounter = 0
+        }
 
 updateMemberProfile :: DB.Connection -> User -> GroupMember -> Profile -> ExceptT StoreError IO GroupMember
 updateMemberProfile db user@User {userId} m p'
diff --git a/src/Simplex/Chat/Store/Migrations.hs b/src/Simplex/Chat/Store/Migrations.hs
index 6d3a7a9a4f..d8bdbd6fd3 100644
--- a/src/Simplex/Chat/Store/Migrations.hs
+++ b/src/Simplex/Chat/Store/Migrations.hs
@@ -101,6 +101,7 @@ import Simplex.Chat.Migrations.M20240122_indexes
 import Simplex.Chat.Migrations.M20240214_redirect_file_id
 import Simplex.Chat.Migrations.M20240222_app_settings
 import Simplex.Chat.Migrations.M20240226_users_restrict
+import Simplex.Chat.Migrations.M20240228_pq
 import Simplex.Messaging.Agent.Store.SQLite.Migrations (Migration (..))
 
 schemaMigrations :: [(String, Query, Maybe Query)]
@@ -201,7 +202,8 @@ schemaMigrations =
     ("20240122_indexes", m20240122_indexes, Just down_m20240122_indexes),
     ("20240214_redirect_file_id", m20240214_redirect_file_id, Just down_m20240214_redirect_file_id),
     ("20240222_app_settings", m20240222_app_settings, Just down_m20240222_app_settings),
-    ("20240226_users_restrict", m20240226_users_restrict, Just down_m20240226_users_restrict)
+    ("20240226_users_restrict", m20240226_users_restrict, Just down_m20240226_users_restrict),
+    ("20240228_pq", m20240228_pq, Just down_m20240228_pq)
   ]
 
 -- | The list of migrations in ascending order by date
diff --git a/src/Simplex/Chat/Store/Profiles.hs b/src/Simplex/Chat/Store/Profiles.hs
index eceb19ba34..ca1240d307 100644
--- a/src/Simplex/Chat/Store/Profiles.hs
+++ b/src/Simplex/Chat/Store/Profiles.hs
@@ -337,7 +337,8 @@ getUserAddressConnections db User {userId} = do
           db
           [sql|
             SELECT c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id,
-              c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+              c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id,
+              c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
               c.peer_chat_min_version, c.peer_chat_max_version
             FROM connections c
             JOIN user_contact_links uc ON c.user_contact_link_id = uc.user_contact_link_id
@@ -352,7 +353,8 @@ getUserContactLinks db User {userId} =
       db
       [sql|
         SELECT c.connection_id, c.agent_conn_id, c.conn_level, c.via_contact, c.via_user_contact_link, c.via_group_link, c.group_link_id, c.custom_user_profile_id,
-          c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id, c.created_at, c.security_code, c.security_code_verified_at, c.auth_err_counter,
+          c.conn_status, c.conn_type, c.contact_conn_initiated, c.local_alias, c.contact_id, c.group_member_id, c.snd_file_id, c.rcv_file_id, c.user_contact_link_id,
+          c.created_at, c.security_code, c.security_code_verified_at, c.pq_enabled, c.auth_err_counter,
           c.peer_chat_min_version, c.peer_chat_max_version,
           uc.user_contact_link_id, uc.conn_req_contact, uc.group_id
         FROM connections c
diff --git a/src/Simplex/Chat/Store/Shared.hs b/src/Simplex/Chat/Store/Shared.hs
index bc1232f427..65bf359cd4 100644
--- a/src/Simplex/Chat/Store/Shared.hs
+++ b/src/Simplex/Chat/Store/Shared.hs
@@ -148,16 +148,32 @@ toFileInfo (fileId, fileStatus, filePath) = CIFileInfo {fileId, fileStatus, file
 
 type EntityIdsRow = (Maybe Int64, Maybe Int64, Maybe Int64, Maybe Int64, Maybe Int64)
 
-type ConnectionRow = (Int64, ConnId, Int, Maybe Int64, Maybe Int64, Bool, Maybe GroupLinkId, Maybe Int64, ConnStatus, ConnType, Bool, LocalAlias) :. EntityIdsRow :. (UTCTime, Maybe Text, Maybe UTCTime, Int, Version, Version)
+type ConnectionRow = (Int64, ConnId, Int, Maybe Int64, Maybe Int64, Bool, Maybe GroupLinkId, Maybe Int64, ConnStatus, ConnType, Bool, LocalAlias) :. EntityIdsRow :. (UTCTime, Maybe Text, Maybe UTCTime, Maybe Bool, Int, Version, Version)
 
-type MaybeConnectionRow = (Maybe Int64, Maybe ConnId, Maybe Int, Maybe Int64, Maybe Int64, Maybe Bool, Maybe GroupLinkId, Maybe Int64, Maybe ConnStatus, Maybe ConnType, Maybe Bool, Maybe LocalAlias) :. EntityIdsRow :. (Maybe UTCTime, Maybe Text, Maybe UTCTime, Maybe Int, Maybe Version, Maybe Version)
+type MaybeConnectionRow = (Maybe Int64, Maybe ConnId, Maybe Int, Maybe Int64, Maybe Int64, Maybe Bool, Maybe GroupLinkId, Maybe Int64, Maybe ConnStatus, Maybe ConnType, Maybe Bool, Maybe LocalAlias) :. EntityIdsRow :. (Maybe UTCTime, Maybe Text, Maybe UTCTime, Maybe Bool, Maybe Int, Maybe Version, Maybe Version)
 
 toConnection :: ConnectionRow -> Connection
-toConnection ((connId, acId, connLevel, viaContact, viaUserContactLink, viaGroupLink, groupLinkId, customUserProfileId, connStatus, connType, contactConnInitiated, localAlias) :. (contactId, groupMemberId, sndFileId, rcvFileId, userContactLinkId) :. (createdAt, code_, verifiedAt_, authErrCounter, minVer, maxVer)) =
-  let entityId = entityId_ connType
-      connectionCode = SecurityCode <$> code_ <*> verifiedAt_
-      peerChatVRange = JVersionRange $ fromMaybe (versionToRange maxVer) $ safeVersionRange minVer maxVer
-   in Connection {connId, agentConnId = AgentConnId acId, peerChatVRange, connLevel, viaContact, viaUserContactLink, viaGroupLink, groupLinkId, customUserProfileId, connStatus, connType, contactConnInitiated, localAlias, entityId, connectionCode, authErrCounter, createdAt}
+toConnection ((connId, acId, connLevel, viaContact, viaUserContactLink, viaGroupLink, groupLinkId, customUserProfileId, connStatus, connType, contactConnInitiated, localAlias) :. (contactId, groupMemberId, sndFileId, rcvFileId, userContactLinkId) :. (createdAt, code_, verifiedAt_, pqEnabled, authErrCounter, minVer, maxVer)) =
+  Connection
+    { connId,
+      agentConnId = AgentConnId acId,
+      peerChatVRange = JVersionRange $ fromMaybe (versionToRange maxVer) $ safeVersionRange minVer maxVer,
+      connLevel,
+      viaContact,
+      viaUserContactLink,
+      viaGroupLink,
+      groupLinkId,
+      customUserProfileId,
+      connStatus,
+      connType,
+      contactConnInitiated,
+      localAlias,
+      entityId = entityId_ connType,
+      connectionCode = SecurityCode <$> code_ <*> verifiedAt_,
+      pqEnabled,
+      authErrCounter,
+      createdAt
+    }
   where
     entityId_ :: ConnType -> Maybe Int64
     entityId_ ConnContact = contactId
@@ -167,8 +183,8 @@ toConnection ((connId, acId, connLevel, viaContact, viaUserContactLink, viaGroup
     entityId_ ConnUserContact = userContactLinkId
 
 toMaybeConnection :: MaybeConnectionRow -> Maybe Connection
-toMaybeConnection ((Just connId, Just agentConnId, Just connLevel, viaContact, viaUserContactLink, Just viaGroupLink, groupLinkId, customUserProfileId, Just connStatus, Just connType, Just contactConnInitiated, Just localAlias) :. (contactId, groupMemberId, sndFileId, rcvFileId, userContactLinkId) :. (Just createdAt, code_, verifiedAt_, Just authErrCounter, Just minVer, Just maxVer)) =
-  Just $ toConnection ((connId, agentConnId, connLevel, viaContact, viaUserContactLink, viaGroupLink, groupLinkId, customUserProfileId, connStatus, connType, contactConnInitiated, localAlias) :. (contactId, groupMemberId, sndFileId, rcvFileId, userContactLinkId) :. (createdAt, code_, verifiedAt_, authErrCounter, minVer, maxVer))
+toMaybeConnection ((Just connId, Just agentConnId, Just connLevel, viaContact, viaUserContactLink, Just viaGroupLink, groupLinkId, customUserProfileId, Just connStatus, Just connType, Just contactConnInitiated, Just localAlias) :. (contactId, groupMemberId, sndFileId, rcvFileId, userContactLinkId) :. (Just createdAt, code_, verifiedAt_, pqEnabled_, Just authErrCounter, Just minVer, Just maxVer)) =
+  Just $ toConnection ((connId, agentConnId, connLevel, viaContact, viaUserContactLink, viaGroupLink, groupLinkId, customUserProfileId, connStatus, connType, contactConnInitiated, localAlias) :. (contactId, groupMemberId, sndFileId, rcvFileId, userContactLinkId) :. (createdAt, code_, verifiedAt_, pqEnabled_, authErrCounter, minVer, maxVer))
 toMaybeConnection _ = Nothing
 
 createConnection_ :: DB.Connection -> UserId -> ConnType -> Maybe Int64 -> ConnId -> VersionRange -> Maybe ContactId -> Maybe Int64 -> Maybe ProfileId -> Int -> UTCTime -> SubscriptionMode -> IO Connection
@@ -190,7 +206,27 @@ createConnection_ db userId connType entityId acId peerChatVRange@(VersionRange
         :. (minV, maxV, subMode == SMOnlyCreate)
     )
   connId <- insertedRowId db
-  pure Connection {connId, agentConnId = AgentConnId acId, peerChatVRange = JVersionRange peerChatVRange, connType, contactConnInitiated = False, entityId, viaContact, viaUserContactLink, viaGroupLink, groupLinkId = Nothing, customUserProfileId, connLevel, connStatus = ConnNew, localAlias = "", createdAt = currentTs, connectionCode = Nothing, authErrCounter = 0}
+  pure
+    Connection
+      { connId,
+        agentConnId = AgentConnId acId,
+        peerChatVRange = JVersionRange peerChatVRange,
+        connType,
+        contactConnInitiated = False,
+        entityId,
+        viaContact,
+        viaUserContactLink,
+        viaGroupLink,
+        groupLinkId = Nothing,
+        customUserProfileId,
+        connLevel,
+        connStatus = ConnNew,
+        localAlias = "",
+        createdAt = currentTs,
+        connectionCode = Nothing,
+        pqEnabled = Nothing,
+        authErrCounter = 0
+      }
   where
     ent ct = if connType == ct then entityId else Nothing
 
@@ -205,6 +241,17 @@ createIncognitoProfile_ db userId createdAt Profile {displayName, fullName, imag
     (displayName, fullName, image, userId, Just True, createdAt, createdAt)
   insertedRowId db
 
+updateConnPQEnabled :: DB.Connection -> Int64 -> Bool -> IO ()
+updateConnPQEnabled db connId pqEnabled =
+  DB.execute
+    db
+    [sql|
+      UPDATE connections
+      SET pq_enabled = ?
+      WHERE connection_id = ?
+    |]
+    (pqEnabled, connId)
+
 setPeerChatVRange :: DB.Connection -> Int64 -> VersionRange -> IO ()
 setPeerChatVRange db connId (VersionRange minVer maxVer) =
   DB.execute
diff --git a/src/Simplex/Chat/Types.hs b/src/Simplex/Chat/Types.hs
index 0a35a83edd..6376d50c26 100644
--- a/src/Simplex/Chat/Types.hs
+++ b/src/Simplex/Chat/Types.hs
@@ -211,6 +211,11 @@ contactDeleted Contact {contactStatus} = contactStatus == CSDeleted
 contactSecurityCode :: Contact -> Maybe SecurityCode
 contactSecurityCode Contact {activeConn} = connectionCode =<< activeConn
 
+contactPQEnabled :: Contact -> Bool
+contactPQEnabled Contact {activeConn} = case activeConn of
+  Just Connection {pqEnabled} -> pqEnabled == Just True
+  Nothing -> False
+
 data ContactStatus
   = CSActive
   | CSDeleted -- contact deleted by contact
@@ -563,7 +568,8 @@ data GroupInvitation = GroupInvitation
     invitedMember :: MemberIdRole,
     connRequest :: ConnReqInvitation,
     groupProfile :: GroupProfile,
-    groupLinkId :: Maybe GroupLinkId
+    groupLinkId :: Maybe GroupLinkId,
+    groupSize :: Maybe Int
   }
   deriving (Eq, Show)
 
@@ -571,7 +577,8 @@ data GroupLinkInvitation = GroupLinkInvitation
   { fromMember :: MemberIdRole,
     fromMemberName :: ContactName,
     invitedMember :: MemberIdRole,
-    groupProfile :: GroupProfile
+    groupProfile :: GroupProfile,
+    groupSize :: Maybe Int
   }
   deriving (Eq, Show)
 
@@ -1277,6 +1284,8 @@ type ConnReqInvitation = ConnectionRequestUri 'CMInvitation
 
 type ConnReqContact = ConnectionRequestUri 'CMContact
 
+type PQFlag = Bool
+
 data Connection = Connection
   { connId :: Int64,
     agentConnId :: AgentConnId,
@@ -1293,6 +1302,7 @@ data Connection = Connection
     localAlias :: Text,
     entityId :: Maybe Int64, -- contact, group member, file ID or user contact ID
     connectionCode :: Maybe SecurityCode,
+    pqEnabled :: Maybe PQFlag,
     authErrCounter :: Int,
     createdAt :: UTCTime
   }
diff --git a/src/Simplex/Chat/View.hs b/src/Simplex/Chat/View.hs
index 667613ba6a..de249cec4a 100644
--- a/src/Simplex/Chat/View.hs
+++ b/src/Simplex/Chat/View.hs
@@ -340,6 +340,7 @@ responseToView hu@(currentRH, user_) ChatConfig {logLevel, showReactions, showRe
   CRRemoteCtrlConnected RemoteCtrlInfo {remoteCtrlId = rcId, ctrlDeviceName} ->
     ["remote controller " <> sShow rcId <> " session started with " <> plain ctrlDeviceName]
   CRRemoteCtrlStopped {} -> ["remote controller stopped"]
+  CRContactPQEnabled u c pqOn -> ttyUser u [ttyContact' c <> ": post-quantum encryption " <> (if pqOn then "enabled" else "disabled")]
   CRSQLResult rows -> map plain rows
   CRSlowSQLQueries {chatQueries, agentQueries} ->
     let viewQuery SlowSQLQuery {query, queryStats = SlowQueryStats {count, timeMax, timeAvg}} =
@@ -1173,6 +1174,7 @@ viewContactInfo ct@Contact {contactId, profile = LocalProfile {localAlias, conta
       incognitoProfile
     <> ["alias: " <> plain localAlias | localAlias /= ""]
     <> [viewConnectionVerified (contactSecurityCode ct)]
+    <> ["post-quantum encryption enabled" | contactPQEnabled ct]
     <> maybe [] (\ac -> [viewPeerChatVRange (peerChatVRange ac)]) activeConn
 
 viewGroupInfo :: GroupInfo -> GroupSummary -> [StyledString]
diff --git a/tests/ProtocolTests.hs b/tests/ProtocolTests.hs
index c076ebecfc..822b079e9e 100644
--- a/tests/ProtocolTests.hs
+++ b/tests/ProtocolTests.hs
@@ -229,10 +229,10 @@ decodeChatMessageTest = describe "Chat message encoding/decoding" $ do
       ==# XContact testProfile Nothing
   it "x.grp.inv" $
     "{\"v\":\"1\",\"event\":\"x.grp.inv\",\"params\":{\"groupInvitation\":{\"connRequest\":\"simplex:/invitation#/?v=1&smp=smp%3A%2F%2F1234-w%3D%3D%40smp.simplex.im%3A5223%2F3456-w%3D%3D%23%2F%3Fv%3D1-2%26dh%3DMCowBQYDK2VuAyEAjiswwI3O_NlS8Fk3HJUW870EY2bAwmttMBsvRB9eV3o%253D&e2e=v%3D2%26x3dh%3DMEIwBQYDK2VvAzkAmKuSYeQ_m0SixPDS8Wq8VBaTS1cW-Lp0n0h4Diu-kUpR-qXx4SDJ32YGEFoGFGSbGPry5Ychr6U%3D%2CMEIwBQYDK2VvAzkAmKuSYeQ_m0SixPDS8Wq8VBaTS1cW-Lp0n0h4Diu-kUpR-qXx4SDJ32YGEFoGFGSbGPry5Ychr6U%3D\",\"invitedMember\":{\"memberRole\":\"member\",\"memberId\":\"BQYHCA==\"},\"groupProfile\":{\"fullName\":\"Team\",\"displayName\":\"team\",\"groupPreferences\":{\"reactions\":{\"enable\":\"on\"},\"voice\":{\"enable\":\"on\"}}},\"fromMember\":{\"memberRole\":\"admin\",\"memberId\":\"AQIDBA==\"}}}}"
-      #==# XGrpInv GroupInvitation {fromMember = MemberIdRole (MemberId "\1\2\3\4") GRAdmin, invitedMember = MemberIdRole (MemberId "\5\6\7\8") GRMember, connRequest = testConnReq, groupProfile = testGroupProfile, groupLinkId = Nothing}
+      #==# XGrpInv GroupInvitation {fromMember = MemberIdRole (MemberId "\1\2\3\4") GRAdmin, invitedMember = MemberIdRole (MemberId "\5\6\7\8") GRMember, connRequest = testConnReq, groupProfile = testGroupProfile, groupLinkId = Nothing, groupSize = Nothing}
   it "x.grp.inv with group link id" $
     "{\"v\":\"1\",\"event\":\"x.grp.inv\",\"params\":{\"groupInvitation\":{\"connRequest\":\"simplex:/invitation#/?v=1&smp=smp%3A%2F%2F1234-w%3D%3D%40smp.simplex.im%3A5223%2F3456-w%3D%3D%23%2F%3Fv%3D1-2%26dh%3DMCowBQYDK2VuAyEAjiswwI3O_NlS8Fk3HJUW870EY2bAwmttMBsvRB9eV3o%253D&e2e=v%3D2%26x3dh%3DMEIwBQYDK2VvAzkAmKuSYeQ_m0SixPDS8Wq8VBaTS1cW-Lp0n0h4Diu-kUpR-qXx4SDJ32YGEFoGFGSbGPry5Ychr6U%3D%2CMEIwBQYDK2VvAzkAmKuSYeQ_m0SixPDS8Wq8VBaTS1cW-Lp0n0h4Diu-kUpR-qXx4SDJ32YGEFoGFGSbGPry5Ychr6U%3D\",\"invitedMember\":{\"memberRole\":\"member\",\"memberId\":\"BQYHCA==\"},\"groupProfile\":{\"fullName\":\"Team\",\"displayName\":\"team\",\"groupPreferences\":{\"reactions\":{\"enable\":\"on\"},\"voice\":{\"enable\":\"on\"}}},\"fromMember\":{\"memberRole\":\"admin\",\"memberId\":\"AQIDBA==\"}, \"groupLinkId\":\"AQIDBA==\"}}}"
-      #==# XGrpInv GroupInvitation {fromMember = MemberIdRole (MemberId "\1\2\3\4") GRAdmin, invitedMember = MemberIdRole (MemberId "\5\6\7\8") GRMember, connRequest = testConnReq, groupProfile = testGroupProfile, groupLinkId = Just $ GroupLinkId "\1\2\3\4"}
+      #==# XGrpInv GroupInvitation {fromMember = MemberIdRole (MemberId "\1\2\3\4") GRAdmin, invitedMember = MemberIdRole (MemberId "\5\6\7\8") GRMember, connRequest = testConnReq, groupProfile = testGroupProfile, groupLinkId = Just $ GroupLinkId "\1\2\3\4", groupSize = Nothing}
   it "x.grp.acpt without incognito profile" $
     "{\"v\":\"1\",\"event\":\"x.grp.acpt\",\"params\":{\"memberId\":\"AQIDBA==\"}}"
       #==# XGrpAcpt (MemberId "\1\2\3\4")