diff --git a/hosts/yarn/forza-trigger/python-packages.nix b/hosts/yarn/forza-trigger/python-packages.nix
index 619ffd7..e7cf7f1 100644
--- a/hosts/yarn/forza-trigger/python-packages.nix
+++ b/hosts/yarn/forza-trigger/python-packages.nix
@@ -34,6 +34,17 @@ rec {
       hash = "sha256-yy1MQeRPqaLvoXaAigQd3gPFsFLbwKqrD4mP2zQqcFw=";
     };
 
+
+    # Library bug fix: trigger-effect params 8-10 are never propagated to
+    # the OUT report. effect.vibration() puts the frequency in param9, so
+    # without this patch every vibration call ships frequency=0 to the
+    # controller and the trigger sits silently in vibration mode. The
+    # patch fixes update_out_report to read params 8/9/10 directly off
+    # the parent TriggerEffect state. Confirmed live with strace before
+    # patching: byte 31 (= L2 param9) was 0 every tick during slip events.
+    patches = [
+      ../../../patches/dualsense-controller/0001-propagate-trigger-effect-params-8-10.patch
+    ];
     nativeBuildInputs = [ py.poetry-core ];
 
     # Upstream's pyproject pins pyee ^11 and cffi ^1.15. nixpkgs ships
diff --git a/patches/dualsense-controller/0001-propagate-trigger-effect-params-8-10.patch b/patches/dualsense-controller/0001-propagate-trigger-effect-params-8-10.patch
new file mode 100644
index 0000000..a7c68fd
--- /dev/null
+++ b/patches/dualsense-controller/0001-propagate-trigger-effect-params-8-10.patch
@@ -0,0 +1,43 @@
+From: forza-trigger maintenance <none@local>
+Date: 2026-05-07
+Subject: [PATCH] WriteStates: propagate trigger-effect params 8-10
+
+The library's update_out_report only copies trigger-effect params 1-7
+from per-state values to the OUT report. Params 8/9/10 are never
+propagated and stay at their OutReport-dataclass defaults of 0. This
+silently breaks effects that use those slots — most painfully
+effect.vibration() puts frequency in param9, so vibration mode ships
+frequency=0 in the wire and the trigger does nothing while in
+vibration mode. Confirmed live with strace on yarn: byte 31 (L2
+param9) wire-byte was 0 every tick despite the daemon calling
+effect.vibration(frequency=35).
+
+Fix: read params 8-10 directly off the parent TriggerEffect state
+(which already carries them correctly through _set_value), bypassing
+the per-param individual states. No new WriteStateName enum members
+needed.
+
+Upstream: needs filing against yesbotics/dualsense-controller-python.
+
+--- a/src/dualsense_controller/core/state/write_state/WriteStates.py
++++ b/src/dualsense_controller/core/state/write_state/WriteStates.py
+@@ -269,6 +269,19 @@
+             WriteStateName.RIGHT_TRIGGER_EFFECT_PARAM6).value_raw
+         out_report.right_trigger_effect_param7 = self._get_state_by_name(
+             WriteStateName.RIGHT_TRIGGER_EFFECT_PARAM7).value_raw
++        # Library bug workaround: params 8-10 are never registered as
++        # individual write states so the per-param fan-out in
++        # _on_*_trigger_effect_changed drops them. Read directly off the
++        # parent TriggerEffect state. Without this, effect.vibration(freq=N)
++        # ships frequency=0 to the controller and the trigger sits silent
++        # in vibration mode (confirmed live with strace on yarn before
++        # patching: byte 31 = L2 param9 was 0 every tick).
++        out_report.left_trigger_effect_param8 = self.left_trigger_effect.value.param8
++        out_report.left_trigger_effect_param9 = self.left_trigger_effect.value.param9
++        out_report.left_trigger_effect_param10 = self.left_trigger_effect.value.param10
++        out_report.right_trigger_effect_param8 = self.right_trigger_effect.value.param8
++        out_report.right_trigger_effect_param9 = self.right_trigger_effect.value.param9
++        out_report.right_trigger_effect_param10 = self.right_trigger_effect.value.param10
+ 
+     def _create_and_register_state(
+             self,