diff --git a/fusion_plating/fusion_plating_shopfloor/data/fp_tablet_cron.xml b/fusion_plating/fusion_plating_shopfloor/data/fp_tablet_cron.xml
index 47b82d2a..479fe2a4 100644
--- a/fusion_plating/fusion_plating_shopfloor/data/fp_tablet_cron.xml
+++ b/fusion_plating/fusion_plating_shopfloor/data/fp_tablet_cron.xml
@@ -1,6 +1,14 @@
 <?xml version="1.0" encoding="utf-8"?>
 <odoo>
-    <!-- Placeholder for cron records added in Phase C task C4
-         (force-lock stale tablet sessions). File registered in manifest
-         to keep the data list stable across phase boundaries. -->
+    <data noupdate="1">
+        <record id="ir_cron_force_lock_stale_sessions" model="ir.cron">
+            <field name="name">Tablet: Force-lock Stale PIN Sessions</field>
+            <field name="model_id" ref="model_fp_tablet_session_event"/>
+            <field name="state">code</field>
+            <field name="code">model._cron_force_lock_stale_sessions()</field>
+            <field name="interval_number">5</field>
+            <field name="interval_type">minutes</field>
+            <field name="active" eval="True"/>
+        </record>
+    </data>
 </odoo>
diff --git a/fusion_plating/fusion_plating_shopfloor/models/fp_tablet_session_event.py b/fusion_plating/fusion_plating_shopfloor/models/fp_tablet_session_event.py
index 039c8e0d..d87cbb13 100644
--- a/fusion_plating/fusion_plating_shopfloor/models/fp_tablet_session_event.py
+++ b/fusion_plating/fusion_plating_shopfloor/models/fp_tablet_session_event.py
@@ -113,3 +113,45 @@ class FpTabletSessionEvent(models.Model):
                 "admin-purge context flag."
             ))
         return super().unlink()
+
+    @api.model
+    def _cron_force_lock_stale_sessions(self):
+        """Belt-and-suspenders cron: find any active unlock event past
+        the 8-hour ceiling and mark it force-locked.
+
+        Handles browser crashes, tablet reboots with stale cookies,
+        and any path that bypasses /fp/tablet/lock_session.
+
+        Runs every 5 minutes per fp_tablet_cron.xml.
+        """
+        from datetime import timedelta
+        ceiling_hours = int(self.env['ir.config_parameter'].sudo().get_param(
+            'fp.tablet.session_ceiling_hours', 8))
+        cutoff = fields.Datetime.now() - timedelta(hours=ceiling_hours)
+        stale = self.search([
+            ('event_type', '=', 'unlock'),
+            ('session_ended_at', '=', False),
+            ('session_started_at', '<', cutoff),
+        ])
+        now = fields.Datetime.now()
+        for event in stale:
+            duration = int((now - event.session_started_at).total_seconds())
+            self.sudo().create({
+                'event_type': 'force_lock',
+                'user_id': event.user_id.id,
+                'session_id_hash': event.session_id_hash,
+                'session_started_at': event.session_started_at,
+                'session_ended_at': now,
+                'duration_seconds': duration,
+                'notes': 'Cron force-lock: session exceeded %d-hour ceiling' % ceiling_hours,
+            })
+            # Mark the original unlock event closed so it's not reprocessed
+            # next tick. write() is blocked by the model override — use
+            # direct SQL bypass (this is the documented escape hatch for
+            # the retention/cron path).
+            self.env.cr.execute(
+                """UPDATE fp_tablet_session_event
+                   SET session_ended_at = %s, duration_seconds = %s
+                 WHERE id = %s""",
+                (now, duration, event.id),
+            )