diff --git a/src/web/server.py b/src/web/server.py
index 6e4a69e..18a7c15 100644
--- a/src/web/server.py
+++ b/src/web/server.py
@@ -1491,6 +1491,12 @@ class WebServer:
             # Update LATENCY_PROFILES with custom entry so latency_profile resolves it
             LATENCY_PROFILES[effective_key] = target_profile
 
+            # Sync AudioConfig overrides BEFORE JACK restart so latency_profile
+            # used by start_jack() returns the correct period. Without this, the
+            # stale boot-time self.period override stomps on the LATENCY_PROFILES entry.
+            audio_sys.config.period = target_profile["period"]
+            audio_sys.config.rate = target_profile["rate"]
+
             # ── Kill JACK server FIRST (breaks any client deadlock) ──
             # jack.Client.deactivate() is a synchronous JACK protocol call
             # that blocks until the RT callback thread acknowledges. If the