diff --git a/src/proto/inspircd.rs b/src/proto/inspircd.rs
index 069a61d..279e202 100644
--- a/src/proto/inspircd.rs
+++ b/src/proto/inspircd.rs
@@ -32,6 +32,12 @@ impl Protocol for InspIrcd {
     }
 
     fn parse(&mut self, line: &str) -> Vec<NetEvent> {
+        // Strip an optional IRCv3 message-tag prefix (@k=v;… ) — insp tags PRIVMSGs
+        // with time/msgid, and it sits before the :source.
+        let line = match line.strip_prefix('@') {
+            Some(rest) => rest.splitn(2, ' ').nth(1).unwrap_or(""),
+            None => line,
+        };
         let (source, rest) = match line.strip_prefix(':') {
             Some(s) => {
                 let mut it = s.splitn(2, ' ');
@@ -76,8 +82,10 @@ impl Protocol for InspIrcd {
                 let dest = from.clone().unwrap_or_else(|| self.sid.clone());
                 vec![self.from_us(format!("PONG {} {}", dest, token))]
             }
+            // insp4 UID: uuid nickts nick realhost disphost realuser dispuser ip signonts +modes :gecos
+            // (both a real AND a displayed user field — see m_spanningtree/uid.cpp Builder).
             NetAction::IntroduceUser { uid, nick, ident, host, gecos } => vec![self.from_us(format!(
-                "UID {uid} {ts} {nick} {host} {host} {ident} 0.0.0.0 {ts} +ioS :{gecos}",
+                "UID {uid} {ts} {nick} {host} {host} {ident} {ident} 0.0.0.0 {ts} +i :{gecos}",
                 uid = uid, ts = self.ts, nick = nick, host = host, ident = ident, gecos = gecos
             ))],
             NetAction::Privmsg { from, to, text } => {
diff --git a/testing/fedserv_services.py b/testing/fedserv_services.py
new file mode 100644
index 0000000..233cab9
--- /dev/null
+++ b/testing/fedserv_services.py
@@ -0,0 +1,57 @@
+"""irctest controller for fedserv.
+
+Copy (or symlink) this file into irctest's ``irctest/controllers/`` directory,
+then run the services tests against an isolated InspIRCd + fedserv:
+
+    FEDSERV_BIN=/path/to/federated-services/target/release/fedserv \\
+    PATH=/path/to/inspircd/run/bin:$PATH \\
+    python -m pytest \\
+        --controller=irctest.controllers.inspircd \\
+        --services-controller=irctest.controllers.fedserv_services \\
+        irctest/server_tests/account_registration.py
+
+irctest spawns its own ircd + services on random ports, so this never touches a
+real network. See https://github.com/progval/irctest
+"""
+import os
+import shutil
+from typing import Type
+
+from irctest.basecontrollers import BaseServicesController, DirectoryBasedController
+
+CONFIG = """\
+[uplink]
+host = "{server_hostname}"
+port = {server_port}
+password = "password"
+
+[server]
+name = "My.Little.Services"
+sid = "42S"
+description = "Federated Services"
+protocol = 1206
+"""
+
+
+class FedservController(BaseServicesController, DirectoryBasedController):
+    software_name = "fedserv"
+    saslserv = "NickServ"
+
+    def run(self, protocol: str, server_hostname: str, server_port: int) -> None:
+        self.create_config()
+        assert protocol in ("inspircd", "inspircd3"), f"fedserv speaks inspircd, not {protocol}"
+
+        binary = (
+            os.environ.get("FEDSERV_BIN")
+            or shutil.which("fedserv")
+            or "target/release/fedserv"
+        )
+
+        with self.open_file("config.toml") as fd:
+            fd.write(CONFIG.format(server_hostname=server_hostname, server_port=server_port))
+
+        self.proc = self.execute([binary, "config.toml"], cwd=self.directory)
+
+
+def get_irctest_controller_class() -> Type[FedservController]:
+    return FedservController