diff --git a/archreview/plans/R2-09-driver-fleet-batch-plan.md.tasks.json b/archreview/plans/R2-09-driver-fleet-batch-plan.md.tasks.json
index 0e58bbb9..b154d0d3 100644
--- a/archreview/plans/R2-09-driver-fleet-batch-plan.md.tasks.json
+++ b/archreview/plans/R2-09-driver-fleet-batch-plan.md.tasks.json
@@ -145,7 +145,7 @@
     {
       "id": "B4.4",
       "subject": "B4: S7 seam comment pointing R2-01 at ConnectionBackoff; suites green; merge PR 4",
-      "status": "pending",
+      "status": "completed",
       "blockedBy": [
         "B4.1",
         "B4.2",
diff --git a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs
index f97b8b26..829d28d8 100644
--- a/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs
+++ b/src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.S7/S7Driver.cs
@@ -1215,9 +1215,14 @@ public sealed class S7Driver
     ///         While the PLC is down every data call and probe tick pays a full connect attempt
     ///         bounded only by <c>_options.Timeout</c> (STAB-8). This method is the single
     ///         choke-point all S7 reconnects flow through (already gate-serialized), so the
-    ///         fleet-wide connect-attempt throttle planned in R2-09 plugs in here: a
-    ///         last-failed-attempt timestamp checked at the top of the slow path. Deliberately NOT
-    ///         implemented driver-locally — see
+    ///         fleet-wide connect-attempt throttle plugs in here. R2-09 (sub-batch B3/B4) shipped the
+    ///         shared <see cref="ConnectionBackoff"/> primitive
+    ///         (<c>src/Core/…/Core.Abstractions/ConnectionBackoff.cs</c>) — the S7 wiring is a
+    ///         per-driver <c>ConnectionBackoff</c> field consulted with <c>ShouldAttempt(now)</c> at
+    ///         the top of the slow path (fail fast + degrade inside the window) plus
+    ///         <c>RecordFailure</c>/<c>RecordSuccess</c> around the connect, all under <c>_gate</c>
+    ///         (which satisfies the primitive's caller-synchronized contract; TwinCAT/FOCAS/AbCip
+    ///         already wire it this way). Deliberately NOT implemented driver-locally here — owned by
     ///         <c>archreview/plans/R2-01-s7-fault-hardening-plan.md</c> Finding 3.
     ///     </para>
     /// </remarks>