fix: use client nick for synthetic JOINs and own-nick rewriting

irssi (and other IRC clients) only open a channel window when they see
a JOIN from their own nick. The synthetic JOINs were using the network
nick (e.g. pagumowa) but the client registered as tester -- mismatch.

Three changes:
- Synthetic JOIN prefix is now client_nick!user@bouncer
- 001 welcome uses the client's registered nick
- encode_nick/encode_message accept client_nick param to rewrite own
  nicks from any network to the client's nick, so irssi recognizes
  all self-actions consistently

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/bouncer/client.py

@@ -56,6 +56,11 @@ class Client:
         self._pass_raw: str = ""
         self._addr = writer.get_extra_info("peername", ("?", 0))
 
+    @property
+    def nick(self) -> str:
+        """The nick the client registered with."""
+        return self._nick
+
     async def handle(self) -> None:
         """Main client session loop."""
         log.info("client connected from %s", self._addr)
@@ -161,9 +166,8 @@ class Client:
     async def _send_welcome(self) -> None:
         """Send IRC welcome sequence and channel state from all networks."""
         server_name = "bouncer"
-        # Pick a representative nick for the welcome numerics
-        own_nicks = self._router.get_own_nicks()
-        nick = next(iter(own_nicks.values()), self._nick)
+        nick = self._nick
+        self_prefix = f"{nick}!{self._user}@bouncer"
 
         networks = ", ".join(self._router.network_names())
         self._send_msg(IRCMessage(
@@ -185,15 +189,14 @@ class Client:
 
         # Send namespaced channel state from every network
         for net_name, network in sorted(self._router.networks.items()):
-            net_nick = network.nick
             for channel in sorted(network.channels):
                 ns_channel = encode_channel(channel, net_name)
 
-                # Synthetic JOIN so the client knows we're in this channel
+                # Synthetic JOIN from client's own nick so irssi opens the window
                 self._send_msg(IRCMessage(
                     command="JOIN",
                     params=[ns_channel],
-                    prefix=net_nick,
+                    prefix=self_prefix,
                 ))
 
                 # Topic

src/bouncer/namespace.py

@@ -28,17 +28,31 @@ def decode_channel(namespaced: str) -> tuple[str, str | None]:
     return namespaced[:idx], namespaced[idx + 1:]
 
 
-def encode_nick(nick: str, network: str, own_nicks: dict[str, str]) -> str:
-    """Suffix a nick unless it belongs to us on *any* network."""
+def encode_nick(
+    nick: str,
+    network: str,
+    own_nicks: dict[str, str],
+    client_nick: str | None = None,
+) -> str:
+    """Suffix a nick unless it belongs to us on *any* network.
+
+    If *client_nick* is set, own nicks are rewritten to match the client's
+    registered nick so IRC clients recognise them as "self".
+    """
     if nick in own_nicks.values():
-        return nick
+        return client_nick if client_nick else nick
     return f"{nick}{SEPARATOR}{network}"
 
 
-def encode_prefix(prefix: str, network: str, own_nicks: dict[str, str]) -> str:
+def encode_prefix(
+    prefix: str,
+    network: str,
+    own_nicks: dict[str, str],
+    client_nick: str | None = None,
+) -> str:
     """Namespace the nick portion of ``nick!user@host``."""
     nick, user, host = parse_prefix(prefix)
-    enc = encode_nick(nick, network, own_nicks)
+    enc = encode_nick(nick, network, own_nicks, client_nick=client_nick)
     if user and host:
         return f"{enc}!{user}@{host}"
     if user:
@@ -66,16 +80,22 @@ def _is_channel(target: str) -> bool:
     return target.startswith(("#", "&", "+", "!"))
 
 
-def encode_message(msg: IRCMessage, network: str, own_nicks: dict[str, str]) -> IRCMessage:
+def encode_message(
+    msg: IRCMessage,
+    network: str,
+    own_nicks: dict[str, str],
+    client_nick: str | None = None,
+) -> IRCMessage:
     """Namespace an entire IRC message for delivery to a client.
 
     - Channels in params get ``/network`` suffix
     - Prefix nick gets ``/network`` suffix (unless it's our own)
+    - Own nicks rewritten to *client_nick* when set
     - Special handling for 353 (NAMREPLY nick list) and NICK (new nick in trailing)
     """
     prefix = msg.prefix
     if prefix:
-        prefix = encode_prefix(prefix, network, own_nicks)
+        prefix = encode_prefix(prefix, network, own_nicks, client_nick=client_nick)
 
     params = list(msg.params)
 
@@ -91,13 +111,15 @@ def encode_message(msg: IRCMessage, network: str, own_nicks: dict[str, str]) ->
             while bare and bare[0] in "@+%~&":
                 mode_prefix += bare[0]
                 bare = bare[1:]
-            encoded.append(mode_prefix + encode_nick(bare, network, own_nicks))
+            encoded.append(mode_prefix + encode_nick(
+                bare, network, own_nicks, client_nick=client_nick,
+            ))
         params[3] = " ".join(encoded)
 
     elif msg.command == "NICK" and params:
         # NICK: params[0] is the new nick
         new_nick = params[0]
-        params[0] = encode_nick(new_nick, network, own_nicks)
+        params[0] = encode_nick(new_nick, network, own_nicks, client_nick=client_nick)
 
     else:
         # Generic: namespace channel-like params[0]

src/bouncer/router.py

@@ -176,13 +176,14 @@ class Router:
             if max_msgs > 0:
                 await self.backlog.prune(network_name, keep=max_msgs)
 
-        # Namespace and forward to all clients
+        # Namespace and forward to all clients (per-client: own nicks -> client nick)
         own_nicks = self.get_own_nicks()
-        namespaced = encode_message(msg, network_name, own_nicks)
-        data = namespaced.format()
         for client in self.clients:
             try:
-                client.write(data)
+                namespaced = encode_message(
+                    msg, network_name, own_nicks, client_nick=client.nick,
+                )
+                client.write(namespaced.format())
             except Exception:
                 log.exception("failed to write to client")
 
@@ -203,7 +204,9 @@ class Router:
                 params=[entry.target, entry.content],
                 prefix=entry.sender,
             )
-            namespaced = encode_message(msg, network_name, own_nicks)
+            namespaced = encode_message(
+                msg, network_name, own_nicks, client_nick=client.nick,
+            )
             try:
                 client.write(namespaced.format())
             except Exception:

tests/test_namespace.py

@@ -44,6 +44,12 @@ class TestEncodeNick:
         # Own nick on another network still shown bare
         assert encode_nick("mybot2", "libera", OWN) == "mybot2"
 
+    def test_own_nick_rewritten_to_client_nick(self):
+        assert encode_nick("mybot", "libera", OWN, client_nick="tester") == "tester"
+
+    def test_foreign_nick_unaffected_by_client_nick(self):
+        assert encode_nick("user123", "libera", OWN, client_nick="tester") == "user123/libera"
+
 
 class TestEncodePrefix:
     def test_full_prefix(self):
@@ -141,3 +147,22 @@ class TestEncodeMessage:
         )
         out = encode_message(msg, "libera", OWN)
         assert out.raw is None  # raw must not carry over
+
+    def test_own_prefix_rewritten_to_client_nick(self):
+        msg = IRCMessage(
+            command="PRIVMSG",
+            params=["#test", "hello"],
+            prefix="mybot!ident@host",
+        )
+        out = encode_message(msg, "libera", OWN, client_nick="tester")
+        assert out.prefix == "tester!ident@host"
+
+    def test_namreply_own_nick_rewritten(self):
+        msg = IRCMessage(
+            command="353",
+            params=["mybot", "=", "#test", "@op mybot"],
+        )
+        out = encode_message(msg, "libera", OWN, client_nick="tester")
+        names = out.params[3].split()
+        assert names[0] == "@op/libera"
+        assert names[1] == "tester"