diff --git a/docs/reference/tracebox.md b/docs/reference/tracebox.md
index 0c64b7e0467..0647e395991 100644
--- a/docs/reference/tracebox.md
+++ b/docs/reference/tracebox.md
@@ -87,6 +87,9 @@ The following applets are available:
 `traced_probes`
 :    Probes for system-wide tracing (ftrace, /proc pollers).
 
+`traced_relay`
+:    Relays trace data to a remote tracing service.
+
 `traced_perf`
 :    Perf-based CPU profiling data source.
 
diff --git a/src/tracebox/BUILD.gn b/src/tracebox/BUILD.gn
index 65a64279132..d967889dfe0 100644
--- a/src/tracebox/BUILD.gn
+++ b/src/tracebox/BUILD.gn
@@ -23,6 +23,7 @@ executable("tracebox") {
     "../perfetto_cmd",
     "../perfetto_cmd:trigger_perfetto_cmd",
     "../traced/service",
+    "../traced_relay:lib",
     "../websocket_bridge:lib",
   ]
   if (enable_perfetto_traced_probes) {
diff --git a/src/tracebox/tracebox.cc b/src/tracebox/tracebox.cc
index f8833aef97e..2fc8ba45429 100644
--- a/src/tracebox/tracebox.cc
+++ b/src/tracebox/tracebox.cc
@@ -48,6 +48,7 @@ struct Applet {
 const Applet g_applets[]{
     {"traced", ServiceMain},
     {"traced_probes", ProbesMain},
+    {"traced_relay", RelayServiceMain},
 #if PERFETTO_BUILDFLAG(PERFETTO_TRACED_PERF)
     {"traced_perf", TracedPerfMain},
 #endif
diff --git a/src/traced_relay/relay_service.cc b/src/traced_relay/relay_service.cc
index e973e5cf10e..bad3677af9b 100644
--- a/src/traced_relay/relay_service.cc
+++ b/src/traced_relay/relay_service.cc
@@ -602,6 +602,16 @@ int PERFETTO_EXPORT_ENTRYPOINT RelayServiceMain(int argc, char** argv) {
     svc->Start(listen_socket, GetRelaySocket());
   }
 
+  // If the TRACED_RELAY_NOTIFY_FD env var is set, write 1 and close the FD.
+  // This is so tools can synchronize with the point where the IPC socket
+  // has been opened, without having to poll.
+  const char* env_notif = getenv("TRACED_RELAY_NOTIFY_FD");
+  if (env_notif) {
+    int notif_fd = atoi(env_notif);
+    PERFETTO_CHECK(base::WriteAll(notif_fd, "1", 1) == 1);
+    PERFETTO_CHECK(base::CloseFile(notif_fd) == 0);
+  }
+
   // Set the CPU limit and start the watchdog running. The memory limit will
   // be set inside the service code as it relies on the size of buffers.
   // The CPU limit is the generic one defined in watchdog.h.