diff --git a/fusion_plating/fusion_plating/__manifest__.py b/fusion_plating/fusion_plating/__manifest__.py
index b5c25e37..15002879 100644
--- a/fusion_plating/fusion_plating/__manifest__.py
+++ b/fusion_plating/fusion_plating/__manifest__.py
@@ -5,7 +5,7 @@
 
 {
     'name': 'Fusion Plating',
-    'version': '19.0.8.5.0',
+    'version': '19.0.8.5.1',
     'category': 'Manufacturing/Plating',
     'summary': 'Core plating / metal finishing ERP: facilities, processes, tanks, baths, jobs, operators.',
     'description': """
diff --git a/fusion_plating/fusion_plating/models/fp_job_step.py b/fusion_plating/fusion_plating/models/fp_job_step.py
index 01f09211..dd7fbc34 100644
--- a/fusion_plating/fusion_plating/models/fp_job_step.py
+++ b/fusion_plating/fusion_plating/models/fp_job_step.py
@@ -158,31 +158,31 @@ class FpJobStep(models.Model):
     # ------------------------------------------------------------------
     # Implemented: button_start (ready/paused → in_progress),
     #              button_finish (in_progress → done).
-    # Stubs (raise NotImplementedError for Task 1.6):
+    # Stubs (raise NotImplementedError; wiring deferred):
     #              button_pause   (in_progress → paused)
     #              button_resume  (covered by button_start when state='paused')
     #              button_skip    (pending/ready → skipped)
     #              button_cancel  (any non-done → cancelled)
-    # Predecessor-driven transition pending → ready will land in
-    # Task 1.6 along with first-step / dependency wiring.
+    # Predecessor-driven transition pending → ready will be wired
+    # alongside first-step / dependency logic in a future task.
     # ------------------------------------------------------------------
 
     def button_pause(self):
         raise NotImplementedError(_(
-            "button_pause lands in Task 1.6 (operator pause / break / "
+            "button_pause is not yet implemented (operator pause / break / "
             "end-of-shift). Use button_finish to complete a step or set "
             "state directly via privileged code."
         ))
 
     def button_skip(self):
         raise NotImplementedError(_(
-            "button_skip lands in Task 1.6 (skip an opt-in step that "
+            "button_skip is not yet implemented (skip an opt-in step that "
             "wasn't activated for this job)."
         ))
 
     def button_cancel(self):
         raise NotImplementedError(_(
-            "button_cancel lands in Task 1.6 (cancelling a single step; "
+            "button_cancel is not yet implemented (cancelling a single step; "
             "cancelling the whole job runs through fp.job.action_cancel)."
         ))
 
diff --git a/fusion_plating/fusion_plating/tests/test_fp_job_step_state_machine.py b/fusion_plating/fusion_plating/tests/test_fp_job_step_state_machine.py
index 3169641c..abea0953 100644
--- a/fusion_plating/fusion_plating/tests/test_fp_job_step_state_machine.py
+++ b/fusion_plating/fusion_plating/tests/test_fp_job_step_state_machine.py
@@ -103,3 +103,20 @@ class TestFpJobStepStateMachine(TransactionCase):
         step.duration_actual = 30.0
         # Recompute happens on read after a write to a depends field
         self.assertEqual(step.cost_total, 30.0)
+
+    def test_cost_total_recomputes_when_rate_changes(self):
+        # Insurance test: verify @api.depends('cost_per_hour') triggers
+        # through the related-from-work_centre chain. If a future Odoo
+        # upgrade breaks related-depends, this test catches it.
+        wc = self.env['fp.work.centre'].create({
+            'name': 'WC4', 'code': 'WC4', 'kind': 'wet_line',
+            'cost_per_hour': 60.0,
+        })
+        step = self._make_step(work_centre_id=wc.id)
+        step.duration_actual = 30.0
+        self.assertEqual(step.cost_total, 30.0)
+        # Change the rate; cost_total should recompute.
+        wc.cost_per_hour = 120.0
+        # Force recompute via invalidate (Odoo recomputes on next read).
+        step.invalidate_recordset(['cost_total'])
+        self.assertEqual(step.cost_total, 60.0)