diff --git a/Command/P2PStdIO.hs b/Command/P2PStdIO.hs
index 4b38057e58..910d9cb7cc 100644
--- a/Command/P2PStdIO.hs
+++ b/Command/P2PStdIO.hs
@@ -99,7 +99,7 @@ performProxyCluster clientuuid clusteruuid servermode = do
 proxyClientSide :: UUID -> Annex ClientSide
 proxyClientSide clientuuid = do
 	clientrunst <- liftIO (mkRunState $ Serving clientuuid Nothing)
-	return $ ClientSide clientrunst (stdioP2PConnection Nothing)
+	ClientSide clientrunst <$> liftIO (stdioP2PConnectionDupped Nothing)
 
 p2pErrHandler :: Annex () -> (a -> CommandPerform) -> Annex (Either ProtoFailure a) -> CommandPerform
 p2pErrHandler closeconn cont a = a >>= \case
diff --git a/P2P/IO.hs b/P2P/IO.hs
index 15e0dccde4..42b53a671a 100644
--- a/P2P/IO.hs
+++ b/P2P/IO.hs
@@ -1,6 +1,6 @@
 {- P2P protocol, IO implementation
  -
- - Copyright 2016-2018 Joey Hess <id@joeyh.name>
+ - Copyright 2016-2024 Joey Hess <id@joeyh.name>
  -
  - Licensed under the GNU AGPL version 3 or higher.
  -}
@@ -16,6 +16,7 @@ module P2P.IO
 	, ConnIdent(..)
 	, ClosableConnection(..)
 	, stdioP2PConnection
+	, stdioP2PConnectionDupped
 	, connectPeer
 	, closeConnection
 	, serveUnixSocket
@@ -104,6 +105,20 @@ stdioP2PConnection g = P2PConnection
 	, connIdent = ConnIdent Nothing
 	}
 
+-- P2PConnection using stdio, but with the handles first duplicated,
+-- to avoid anything that might output to stdio (eg a program run by a
+-- special remote) from interfering with the connection.
+stdioP2PConnectionDupped :: Maybe Git.Repo -> IO P2PConnection
+stdioP2PConnectionDupped g = do
+	(readh, writeh) <- dupIoHandles
+	return $ P2PConnection
+		{ connRepo = g
+		, connCheckAuth = const False
+		, connIhdl = P2PHandle readh
+		, connOhdl = P2PHandle writeh
+		, connIdent = ConnIdent Nothing
+		}
+
 -- Opens a connection to a peer. Does not authenticate with it.
 connectPeer :: Maybe Git.Repo -> P2PAddress -> IO P2PConnection
 connectPeer g (TorAnnex onionaddress onionport) = do
diff --git a/doc/todo/git-annex_proxies.mdwn b/doc/todo/git-annex_proxies.mdwn
index 50eb5aeef3..8d803ec893 100644
--- a/doc/todo/git-annex_proxies.mdwn
+++ b/doc/todo/git-annex_proxies.mdwn
@@ -45,13 +45,6 @@ For June's work on [[design/passthrough_proxy]], remaining todos:
   rather than PUT-FROM or ALREADY-HAVE. Verify that the client processes
   that ok and displays it to the user.
 
-* If a special remote outputs to stdout, or reads from stdin, that will
-  mess up the P2P protocol. Move the special remote proxying into a
-  separate process perhaps, which can be run with stdout and stdin
-  redirected? Or, fix any special remotes that might do that. Are
-  there any left? External special remotes certainly don't since that would
-  mess up their own protocol. Hook special remotes can though.
-
 * Streaming download from proxied special remotes. See design.
 
 * Check annex.diskreserve when proxying for special remotes.