diff --git a/src/ZB.MOM.WW.OtOpcUa.Server/Hosting/ScheduledRecycleHostedService.cs b/src/ZB.MOM.WW.OtOpcUa.Server/Hosting/ScheduledRecycleHostedService.cs
new file mode 100644
index 0000000..08c8231
--- /dev/null
+++ b/src/ZB.MOM.WW.OtOpcUa.Server/Hosting/ScheduledRecycleHostedService.cs
@@ -0,0 +1,117 @@
+using Microsoft.Extensions.Hosting;
+using Microsoft.Extensions.Logging;
+using ZB.MOM.WW.OtOpcUa.Core.Stability;
+
+namespace ZB.MOM.WW.OtOpcUa.Server.Hosting;
+
+///
+/// Drives one or more instances on a fixed tick
+/// cadence. Closes Phase 6.1 Stream B.4 by turning the shipped-as-pure-logic scheduler
+/// into a running background feature.
+///
+///
+/// Registered as a singleton in Program.cs. Each Tier C driver instance that wants a
+/// scheduled recycle registers its scheduler via
+/// at startup. The hosted service
+/// wakes every (default 1 min) and calls
+/// on each registered scheduler.
+///
+/// Scheduler registration is closed after starts — callers
+/// must register before the host starts, typically during DI setup. Adding a scheduler
+/// mid-flight throws to avoid confusing "some ticks saw my scheduler, some didn't" races.
+///
+public sealed class ScheduledRecycleHostedService : BackgroundService
+{
+ private readonly List _schedulers = [];
+ private readonly ILogger _logger;
+ private readonly TimeProvider _timeProvider;
+ private bool _started;
+
+ /// How often fires on each registered scheduler.
+ public TimeSpan TickInterval { get; }
+
+ public ScheduledRecycleHostedService(
+ ILogger logger,
+ TimeProvider? timeProvider = null,
+ TimeSpan? tickInterval = null)
+ {
+ _logger = logger;
+ _timeProvider = timeProvider ?? TimeProvider.System;
+ TickInterval = tickInterval ?? TimeSpan.FromMinutes(1);
+ }
+
+ /// Register a scheduler to drive. Must be called before the host starts.
+ public void AddScheduler(ScheduledRecycleScheduler scheduler)
+ {
+ ArgumentNullException.ThrowIfNull(scheduler);
+ if (_started)
+ throw new InvalidOperationException(
+ "Cannot register a ScheduledRecycleScheduler after the hosted service has started. " +
+ "Register all schedulers during DI configuration / startup.");
+ _schedulers.Add(scheduler);
+ }
+
+ /// Snapshot of the current tick count — diagnostics only.
+ public int TickCount { get; private set; }
+
+ /// Snapshot of the number of registered schedulers — diagnostics only.
+ public int SchedulerCount => _schedulers.Count;
+
+ public override Task StartAsync(CancellationToken cancellationToken)
+ {
+ _started = true;
+ return base.StartAsync(cancellationToken);
+ }
+
+ protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+ {
+ _logger.LogInformation(
+ "ScheduledRecycleHostedService starting — {Count} scheduler(s), tick interval = {Interval}",
+ _schedulers.Count, TickInterval);
+
+ while (!stoppingToken.IsCancellationRequested)
+ {
+ try
+ {
+ await Task.Delay(TickInterval, _timeProvider, stoppingToken).ConfigureAwait(false);
+ }
+ catch (OperationCanceledException) when (stoppingToken.IsCancellationRequested)
+ {
+ break;
+ }
+
+ await TickOnceAsync(stoppingToken).ConfigureAwait(false);
+ }
+
+ _logger.LogInformation("ScheduledRecycleHostedService stopping after {TickCount} tick(s).", TickCount);
+ }
+
+ ///
+ /// Execute one scheduler tick against every registered scheduler. Factored out of the
+ /// loop so tests can drive it directly without needing to
+ /// synchronize with .
+ ///
+ public async Task TickOnceAsync(CancellationToken cancellationToken)
+ {
+ var now = _timeProvider.GetUtcNow().UtcDateTime;
+ TickCount++;
+
+ foreach (var scheduler in _schedulers)
+ {
+ try
+ {
+ var fired = await scheduler.TickAsync(now, cancellationToken).ConfigureAwait(false);
+ if (fired)
+ _logger.LogInformation("Scheduled recycle fired at {Now:o}; next = {Next:o}",
+ now, scheduler.NextRecycleUtc);
+ }
+ catch (OperationCanceledException) { throw; }
+ catch (Exception ex)
+ {
+ // A single scheduler fault must not take down the rest — log + continue.
+ _logger.LogError(ex,
+ "ScheduledRecycleScheduler tick failed at {Now:o}; continuing to other schedulers.", now);
+ }
+ }
+ }
+}
diff --git a/tests/ZB.MOM.WW.OtOpcUa.Server.Tests/ScheduledRecycleHostedServiceTests.cs b/tests/ZB.MOM.WW.OtOpcUa.Server.Tests/ScheduledRecycleHostedServiceTests.cs
new file mode 100644
index 0000000..dea2800
--- /dev/null
+++ b/tests/ZB.MOM.WW.OtOpcUa.Server.Tests/ScheduledRecycleHostedServiceTests.cs
@@ -0,0 +1,152 @@
+using Microsoft.Extensions.Logging.Abstractions;
+using Shouldly;
+using Xunit;
+using ZB.MOM.WW.OtOpcUa.Core.Abstractions;
+using ZB.MOM.WW.OtOpcUa.Core.Stability;
+using ZB.MOM.WW.OtOpcUa.Server.Hosting;
+
+namespace ZB.MOM.WW.OtOpcUa.Server.Tests;
+
+[Trait("Category", "Unit")]
+public sealed class ScheduledRecycleHostedServiceTests
+{
+ private static readonly DateTime T0 = new(2026, 4, 19, 0, 0, 0, DateTimeKind.Utc);
+
+ private sealed class FakeClock : TimeProvider
+ {
+ public DateTime Utc { get; set; } = T0;
+ public override DateTimeOffset GetUtcNow() => new(Utc, TimeSpan.Zero);
+ }
+
+ private sealed class FakeSupervisor : IDriverSupervisor
+ {
+ public string DriverInstanceId => "tier-c-fake";
+ public int RecycleCount { get; private set; }
+ public Task RecycleAsync(string reason, CancellationToken cancellationToken)
+ {
+ RecycleCount++;
+ return Task.CompletedTask;
+ }
+ }
+
+ private sealed class ThrowingSupervisor : IDriverSupervisor
+ {
+ public string DriverInstanceId => "tier-c-throws";
+ public Task RecycleAsync(string reason, CancellationToken cancellationToken)
+ => throw new InvalidOperationException("supervisor unavailable");
+ }
+
+ [Fact]
+ public async Task TickOnce_BeforeInterval_DoesNotFire()
+ {
+ var clock = new FakeClock();
+ var supervisor = new FakeSupervisor();
+ var scheduler = new ScheduledRecycleScheduler(
+ DriverTier.C, TimeSpan.FromMinutes(5), T0, supervisor,
+ NullLogger.Instance);
+
+ var host = new ScheduledRecycleHostedService(NullLogger.Instance, clock);
+ host.AddScheduler(scheduler);
+
+ clock.Utc = T0.AddMinutes(1);
+ await host.TickOnceAsync(CancellationToken.None);
+
+ supervisor.RecycleCount.ShouldBe(0);
+ host.TickCount.ShouldBe(1);
+ }
+
+ [Fact]
+ public async Task TickOnce_AfterInterval_Fires()
+ {
+ var clock = new FakeClock();
+ var supervisor = new FakeSupervisor();
+ var scheduler = new ScheduledRecycleScheduler(
+ DriverTier.C, TimeSpan.FromMinutes(5), T0, supervisor,
+ NullLogger.Instance);
+
+ var host = new ScheduledRecycleHostedService(NullLogger.Instance, clock);
+ host.AddScheduler(scheduler);
+
+ clock.Utc = T0.AddMinutes(6);
+ await host.TickOnceAsync(CancellationToken.None);
+
+ supervisor.RecycleCount.ShouldBe(1);
+ }
+
+ [Fact]
+ public async Task TickOnce_MultipleTicks_AccumulateCount()
+ {
+ var clock = new FakeClock();
+ var host = new ScheduledRecycleHostedService(NullLogger.Instance, clock);
+
+ await host.TickOnceAsync(CancellationToken.None);
+ await host.TickOnceAsync(CancellationToken.None);
+ await host.TickOnceAsync(CancellationToken.None);
+
+ host.TickCount.ShouldBe(3);
+ }
+
+ [Fact]
+ public async Task AddScheduler_AfterStart_Throws()
+ {
+ var host = new ScheduledRecycleHostedService(NullLogger.Instance);
+ using var cts = new CancellationTokenSource();
+ cts.Cancel();
+
+ await host.StartAsync(cts.Token); // flips _started true even with cancelled token
+ await host.StopAsync(CancellationToken.None);
+
+ var scheduler = new ScheduledRecycleScheduler(
+ DriverTier.C, TimeSpan.FromMinutes(5), DateTime.UtcNow, new FakeSupervisor(),
+ NullLogger.Instance);
+
+ Should.Throw(() => host.AddScheduler(scheduler));
+ }
+
+ [Fact]
+ public async Task OneSchedulerThrowing_DoesNotStopOthers()
+ {
+ var clock = new FakeClock();
+ var good = new FakeSupervisor();
+ var bad = new ThrowingSupervisor();
+
+ var goodSch = new ScheduledRecycleScheduler(
+ DriverTier.C, TimeSpan.FromMinutes(5), T0, good,
+ NullLogger.Instance);
+ var badSch = new ScheduledRecycleScheduler(
+ DriverTier.C, TimeSpan.FromMinutes(5), T0, bad,
+ NullLogger.Instance);
+
+ var host = new ScheduledRecycleHostedService(NullLogger.Instance, clock);
+ host.AddScheduler(badSch);
+ host.AddScheduler(goodSch);
+
+ clock.Utc = T0.AddMinutes(6);
+ await host.TickOnceAsync(CancellationToken.None);
+
+ good.RecycleCount.ShouldBe(1, "a faulting scheduler must not poison its neighbours");
+ }
+
+ [Fact]
+ public void SchedulerCount_MatchesAdded()
+ {
+ var host = new ScheduledRecycleHostedService(NullLogger.Instance);
+ var sup = new FakeSupervisor();
+ host.AddScheduler(new ScheduledRecycleScheduler(DriverTier.C, TimeSpan.FromMinutes(5), DateTime.UtcNow, sup, NullLogger.Instance));
+ host.AddScheduler(new ScheduledRecycleScheduler(DriverTier.C, TimeSpan.FromMinutes(10), DateTime.UtcNow, sup, NullLogger.Instance));
+
+ host.SchedulerCount.ShouldBe(2);
+ }
+
+ [Fact]
+ public async Task EmptyScheduler_List_TicksCleanly()
+ {
+ var clock = new FakeClock();
+ var host = new ScheduledRecycleHostedService(NullLogger.Instance, clock);
+
+ // No registered schedulers — tick is a no-op + counter still advances.
+ await host.TickOnceAsync(CancellationToken.None);
+
+ host.TickCount.ShouldBe(1);
+ }
+}