diff --git a/CHANGELOG.md b/CHANGELOG.md
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,4 +1,21 @@
 
+40000.1.0
+=========
+
+API changes:
+ * The postRootId of Post is now a Maybe PostId to better reflect the
+   actual wire format.
+ * MinCommand now has fields for reply parent and root post IDs to
+   support replying to posts with commands such as /me.
+ * CommandResponse's commandResponseType is now Maybe to permit optional
+   types.
+ * PreferenceCategory got a new constructor, PreferenceCategoryLast,
+   mapping to the "last" preference category.
+ * Added functions for bulk fetching for channel/user data:
+   * mmGetAllChannelsForUser
+   * mmGetAllChannelDataForUser
+   * mmGetAllChannelsWithDataForUser
+
 40000.0.1
 =========
 
diff --git a/mattermost-api.cabal b/mattermost-api.cabal
--- a/mattermost-api.cabal
+++ b/mattermost-api.cabal
@@ -1,5 +1,5 @@
 name:                mattermost-api
-version:             40000.0.1
+version:             40000.1.0
 synopsis:            Client API for Mattermost chat system
 description:         Client API for Mattermost chat system
 license:             BSD3
diff --git a/src/Network/Mattermost.hs b/src/Network/Mattermost.hs
--- a/src/Network/Mattermost.hs
+++ b/src/Network/Mattermost.hs
@@ -68,6 +68,9 @@
 , mmJoinChannel
 , mmGetTeams
 , mmGetChannels
+, mmGetAllChannelsForUser
+, mmGetAllChannelDataForUser
+, mmGetAllChannelsWithDataForUser
 , mmGetMoreChannels
 , mmGetChannel
 , mmViewChannel
@@ -144,7 +147,8 @@
                             , encode
                             , eitherDecode
                             )
-import           Data.Maybe ( maybeToList )
+import           Data.Maybe ( maybeToList, fromJust )
+import qualified Data.Foldable as F
 import qualified Data.Sequence as Seq
 import qualified Data.Text as T
 import           Control.Arrow ( left )
@@ -314,6 +318,40 @@
           (idString teamid)
           (idString chanid))
   return
+
+-- | Get channel/user metadata in bulk.
+mmGetAllChannelDataForUser :: Session
+                           -> TeamId
+                           -> UserId
+                           -> IO (Seq.Seq ChannelData)
+mmGetAllChannelDataForUser sess teamid userid =
+    mmDoRequest sess "mmGetAllChannelDataForUser" $
+      printf "/api/v4/users/%s/teams/%s/channels/members"
+             (idString userid)
+             (idString teamid)
+
+mmGetAllChannelsForUser :: Session
+                        -> TeamId
+                        -> UserId
+                        -> IO (Seq.Seq Channel)
+mmGetAllChannelsForUser sess teamid userid =
+    mmDoRequest sess "mmGetAllChannelsForUser" $
+      printf "/api/v4/users/%s/teams/%s/channels"
+             (idString userid)
+             (idString teamid)
+
+mmGetAllChannelsWithDataForUser :: Session
+                                -> TeamId
+                                -> UserId
+                                -> IO (HM.HashMap ChannelId ChannelWithData)
+mmGetAllChannelsWithDataForUser sess teamid userid = do
+    chans <- mmGetAllChannelsForUser sess teamid userid
+    datas <- mmGetAllChannelDataForUser sess teamid userid
+
+    let dataMap = HM.fromList $ F.toList $ (\d -> (channelDataChannelId d, d)) <$> datas
+        mkPair chan = (getId chan, ChannelWithData chan $ fromJust $ HM.lookup (getId chan) dataMap)
+
+    return $ HM.fromList $ F.toList $ mkPair <$> chans
 
 -- |
 -- route: @\/api\/v3\/teams\/{team_id}\/channels\/view@
diff --git a/src/Network/Mattermost/Types.hs b/src/Network/Mattermost/Types.hs
--- a/src/Network/Mattermost/Types.hs
+++ b/src/Network/Mattermost/Types.hs
@@ -640,7 +640,7 @@
   { postPendingPostId :: Maybe PostId
   , postOriginalId    :: Maybe PostId
   , postProps         :: PostProps
-  , postRootId        :: Text
+  , postRootId        :: Maybe PostId
   , postFileIds       :: Seq FileId
   , postId            :: PostId
   , postType          :: PostType
@@ -663,7 +663,7 @@
     postPendingPostId <- maybeFail (v .: "pending_post_id")
     postOriginalId    <- maybeFail (v .: "original_id")
     postProps         <- v .: "props"
-    postRootId        <- v .: "root_id"
+    postRootId        <- maybeFail (v .: "root_id")
     postFileIds       <- (v .: "file_ids") <|> (return mempty)
     postId            <- v .: "id"
     postType          <- v .: "type"
@@ -810,12 +810,16 @@
   = MinCommand
   { minComChannelId :: ChannelId
   , minComCommand   :: Text
+  , minComParentId  :: Maybe PostId
+  , minComRootId    :: Maybe PostId
   } deriving (Read, Show, Eq)
 
 instance A.ToJSON MinCommand where
   toJSON MinCommand { .. } = A.object
     [ "channel_id" .= minComChannelId
     , "command"   .= minComCommand
+    , "parent_id" .= minComParentId
+    , "root_id" .= minComRootId
     ]
 
 --
@@ -863,7 +867,7 @@
 
 data CommandResponse
   = CommandResponse
-  { commandResponseType         :: CommandResponseType
+  { commandResponseType         :: Maybe CommandResponseType
   , commandResponseText         :: Text
   , commandResponseUsername     :: Text
   , commandResponseIconURL      :: Text
@@ -873,7 +877,7 @@
 
 instance A.FromJSON CommandResponse where
   parseJSON = A.withObject "CommandResponse" $ \o -> do
-    commandResponseType         <- o .: "response_type"
+    commandResponseType         <- optional (o .: "response_type")
     commandResponseText         <- o .: "text"
     commandResponseUsername     <- o .: "username"
     commandResponseIconURL      <- o .: "icon_url"
@@ -952,6 +956,7 @@
   | PreferenceCategoryTheme
   | PreferenceCategoryAuthorizedOAuthApp
   | PreferenceCategoryNotifications
+  | PreferenceCategoryLast
   | PreferenceCategoryOther Text
     deriving (Read, Show, Eq)
 
@@ -965,6 +970,7 @@
     "theme"               -> PreferenceCategoryTheme
     "oauth_app"           -> PreferenceCategoryAuthorizedOAuthApp
     "notifications"       -> PreferenceCategoryNotifications
+    "last"                -> PreferenceCategoryLast
     _                     -> PreferenceCategoryOther t
 
 instance A.ToJSON PreferenceCategory where
@@ -977,6 +983,7 @@
     PreferenceCategoryTheme              -> "theme"
     PreferenceCategoryAuthorizedOAuthApp -> "oauth_app"
     PreferenceCategoryNotifications      -> "notifications"
+    PreferenceCategoryLast               -> "last"
     PreferenceCategoryOther t            -> t
 
 data PreferenceName