fix(drivers): wire PollGroupEngine onError->health + 30s poll backoff (05/STAB-9) [modbus,abcip,ablegacy]

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbCip/AbCipDriver.cs

@@ -133,10 +133,29 @@ public sealed class AbCipDriver : IDriver, IReadable, IWritable, ITagDiscovery,
         _poll = new PollGroupEngine(
             reader: ReadAsync,
             onChange: (handle, tagRef, snapshot) =>
-                OnDataChange?.Invoke(this, new DataChangeEventArgs(handle, tagRef, snapshot)));
+                OnDataChange?.Invoke(this, new DataChangeEventArgs(handle, tagRef, snapshot)),
+            onError: HandlePollError,
+            backoffCap: PollBackoffCap);
         _alarmProjection = new AbCipAlarmProjection(this, _options.AlarmPollInterval, _logger);
     }
 
+    /// <summary>Upper bound on the poll-loop failure backoff — adopts the S7-proven 30 s cap fleet-wide (05/STAB-8).</summary>
+    private static readonly TimeSpan PollBackoffCap = TimeSpan.FromSeconds(30);
+
+    /// <summary>
+    ///     05/STAB-9 — routes a poll-loop reader failure to the driver health surface: logs it and
+    ///     degrades to <see cref="DriverState.Degraded"/> preserving <c>LastSuccessfulRead</c>.
+    ///     Never downgrades a <see cref="DriverState.Faulted"/> state (a stronger, config-level signal).
+    /// </summary>
+    /// <param name="ex">The exception caught by the poll engine.</param>
+    internal void HandlePollError(Exception ex)
+    {
+        _logger.LogWarning(ex, "AbCip poll reader failed. Driver={DriverInstanceId}", _driverInstanceId);
+        var current = _health;
+        if (current.State != DriverState.Faulted)
+            _health = new DriverHealth(DriverState.Degraded, current.LastSuccessfulRead, ex.Message);
+    }
+
     /// <summary>
     ///     Fetch + cache the shape of a Logix UDT by template instance id. First call reads
     ///     the Template Object off the controller; subsequent calls for the same

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.AbLegacy/AbLegacyDriver.cs

@@ -65,7 +65,26 @@ public sealed class AbLegacyDriver : IDriver, IReadable, IWritable, ITagDiscover
         _poll = new PollGroupEngine(
             reader: ReadAsync,
             onChange: (handle, tagRef, snapshot) =>
-                OnDataChange?.Invoke(this, new DataChangeEventArgs(handle, tagRef, snapshot)));
+                OnDataChange?.Invoke(this, new DataChangeEventArgs(handle, tagRef, snapshot)),
+            onError: HandlePollError,
+            backoffCap: PollBackoffCap);
+    }
+
+    /// <summary>Upper bound on the poll-loop failure backoff — adopts the S7-proven 30 s cap fleet-wide (05/STAB-8).</summary>
+    private static readonly TimeSpan PollBackoffCap = TimeSpan.FromSeconds(30);
+
+    /// <summary>
+    ///     05/STAB-9 — routes a poll-loop reader failure to the driver health surface: logs it and
+    ///     degrades to <see cref="DriverState.Degraded"/> preserving <c>LastSuccessfulRead</c>.
+    ///     Never downgrades a <see cref="DriverState.Faulted"/> state (a stronger, config-level signal).
+    /// </summary>
+    /// <param name="ex">The exception caught by the poll engine.</param>
+    internal void HandlePollError(Exception ex)
+    {
+        _logger.LogWarning(ex, "AbLegacy poll reader failed. Driver={DriverInstanceId}", _driverInstanceId);
+        var current = _health;
+        if (current.State != DriverState.Faulted)
+            _health = new DriverHealth(DriverState.Degraded, current.LastSuccessfulRead, ex.Message);
     }
 
     /// <inheritdoc />

src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.Modbus/ModbusDriver.cs

@@ -118,7 +118,26 @@ public sealed class ModbusDriver
             {
                 if (!ShouldPublish(tagRef, snapshot)) return;
                 OnDataChange?.Invoke(this, new DataChangeEventArgs(handle, tagRef, snapshot));
-            });
+            },
+            onError: HandlePollError,
+            backoffCap: PollBackoffCap);
+    }
+
+    /// <summary>Upper bound on the poll-loop failure backoff — adopts the S7-proven 30 s cap fleet-wide (05/STAB-8).</summary>
+    private static readonly TimeSpan PollBackoffCap = TimeSpan.FromSeconds(30);
+
+    /// <summary>
+    ///     05/STAB-9 — routes a poll-loop reader failure to the driver health surface: logs it and
+    ///     degrades to <see cref="DriverState.Degraded"/> preserving <c>LastSuccessfulRead</c>.
+    ///     Never downgrades a <see cref="DriverState.Faulted"/> state (a stronger, config-level signal).
+    /// </summary>
+    /// <param name="ex">The exception caught by the poll engine.</param>
+    internal void HandlePollError(Exception ex)
+    {
+        _logger.LogWarning(ex, "Modbus poll reader failed. Driver={DriverInstanceId}", _driverInstanceId);
+        var current = ReadHealth();
+        if (current.State != DriverState.Faulted)
+            WriteHealth(new DriverHealth(DriverState.Degraded, current.LastSuccessfulRead, ex.Message));
     }
 
     /// <inheritdoc />