diff --git a/VigilCareClinicalAPI.Tests/SirsDetectorTests.cs b/VigilCareClinicalAPI.Tests/SirsDetectorTests.cs
new file mode 100644
index 0000000..f3c46dd
--- /dev/null
+++ b/VigilCareClinicalAPI.Tests/SirsDetectorTests.cs
@@ -0,0 +1,214 @@
+using FluentAssertions;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using StackExchange.Redis;
+
+[Collection("Integration")]
+public class SirsDetectorTests : IAsyncLifetime
+{
+    private readonly ApiFixture _fixture;
+    private Guid _encounterId;
+    private Guid _patientId;
+
+    public SirsDetectorTests(ApiFixture fixture) => _fixture = fixture;
+
+    public async Task InitializeAsync()
+    {
+        // Reset PostgreSQL test data
+        using var scope = _fixture.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
+        await DbResetHelper.ResetAsync(db);
+
+        var patient = new Patient
+        {
+            Id = Guid.NewGuid(), Mrn = "MRN-SIRS-001", FirstName = "SIRS", LastName = "Test",
+            DateOfBirth = new DateOnly(1960, 1, 1), Gender = "M",
+            CreatedAt = DateTimeOffset.UtcNow
+        };
+        var encounter = new Encounter
+        {
+            Id = Guid.NewGuid(), PatientId = patient.Id, EncounterType = EncounterType.Inpatient,
+            Status = EncounterStatus.Active, Department = "ICU",
+            AttendingPhysician = "Dr. SIRS", AdmittedAt = DateTimeOffset.UtcNow,
+            CreatedAt = DateTimeOffset.UtcNow
+        };
+        db.Patients.Add(patient);
+        db.Encounters.Add(encounter);
+        await db.SaveChangesAsync();
+
+        _patientId = patient.Id;
+        _encounterId = encounter.Id;
+
+        // Flush all SIRS keys for this encounter from Redis
+        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();
+        var cache = redis.GetDatabase();
+        foreach (var key in SirsEvaluator.AllCriterionKeys(_encounterId))
+            await cache.KeyDeleteAsync(key);
+    }
+
+    public Task DisposeAsync() => Task.CompletedTask;
+
+    private SirsDetector CreateDetector()
+    {
+        using var scope = _fixture.Services.CreateScope();
+        return scope.ServiceProvider.GetRequiredService<SirsDetector>();
+    }
+
+    // Test 1: one criterion met — insufficient for alert
+    [Fact]
+    public async Task OneCriterion_NoAlert()
+    {
+        using var scope = _fixture.Services.CreateScope();
+        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
+
+        var result = await detector.ProcessObservationAsync(
+            _encounterId, _patientId, "HEART_RATE", 95m);
+
+        result.Outcome.Should().Be(SirsOutcome.InsufficientCriteria);
+        result.ActiveCount.Should().Be(1);
+
+        // Verify Redis key was set
+        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();
+        var ttl = await redis.GetDatabase()
+            .KeyTimeToLiveAsync(SirsEvaluator.CriterionKey(_encounterId, "HEART_RATE"));
+        ttl.Should().NotBeNull().And.BeGreaterThan(TimeSpan.Zero);
+    }
+
+    // Test 2: two criteria met — SEPSIS_WARNING alert created
+    [Fact]
+    public async Task TwoCriteriaMet_AlertCreated()
+    {
+        using var scope = _fixture.Services.CreateScope();
+        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
+        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
+
+        // Tachycardia
+        var r1 = await detector.ProcessObservationAsync(
+            _encounterId, _patientId, "HEART_RATE", 95m);
+        r1.Outcome.Should().Be(SirsOutcome.InsufficientCriteria);
+
+        // Fever — now count = 2 → alert
+        var r2 = await detector.ProcessObservationAsync(
+            _encounterId, _patientId, "TEMP_C", 38.5m);
+        r2.Outcome.Should().Be(SirsOutcome.AlertCreated);
+
+        // Verify clinical_alert row in PostgreSQL
+        var alert = await db.ClinicalAlerts.SingleAsync();
+        alert.AlertType.Should().Be(AlertType.SepsisWarning);
+        alert.Severity.Should().Be(AlertSeverity.Critical);
+        alert.Status.Should().Be(AlertStatus.Open);
+        alert.EncounterId.Should().Be(_encounterId);
+        alert.PatientId.Should().Be(_patientId);
+
+        // Verify outbox event was written in the same transaction
+        var outbox = await db.OutboxEvents.SingleAsync();
+        outbox.Topic.Should().Be("alert.generated");
+        outbox.PartitionKey.Should().Be(_encounterId.ToString());
+    }
+
+    // Test 3: third criterion met while alert already open — no second alert
+    [Fact]
+    public async Task ThreeCriteriaMet_NoSecondAlert()
+    {
+        using var scope = _fixture.Services.CreateScope();
+        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
+        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
+
+        await detector.ProcessObservationAsync(_encounterId, _patientId, "HEART_RATE", 95m);
+        await detector.ProcessObservationAsync(_encounterId, _patientId, "TEMP_C", 38.5m);
+        // Third criterion (tachypnea) — alert already open
+        var r3 = await detector.ProcessObservationAsync(
+            _encounterId, _patientId, "RESP_RATE", 22m);
+
+        r3.Outcome.Should().Be(SirsOutcome.AlertAlreadyOpen);
+
+        // Still exactly one alert — the WHERE NOT EXISTS prevented a duplicate
+        var alertCount = await db.ClinicalAlerts.CountAsync();
+        alertCount.Should().Be(1, "a second SEPSIS_WARNING must not be created while one is already open");
+    }
+
+    // Test 4: criterion clears — Redis key deleted, alert remains open
+    //
+    // This is the most important test in Phase 5. It verifies:
+    // (a) The DEL path works when a criterion is no longer met.
+    // (b) Clearing a criterion does not resolve the existing alert — the clinical
+    //     workflow requires explicit acknowledgment. A patient whose temperature
+    //     normalises may still be septic; the alert is for the clinician to evaluate.
+    [Fact]
+    public async Task CriterionClears_KeyDeleted_AlertRemainsOpen()
+    {
+        using var scope = _fixture.Services.CreateScope();
+        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
+        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
+        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();
+        var cache = redis.GetDatabase();
+
+        // Establish two criteria and create the alert
+        await detector.ProcessObservationAsync(_encounterId, _patientId, "HEART_RATE", 95m);
+        await detector.ProcessObservationAsync(_encounterId, _patientId, "TEMP_C", 38.5m);
+
+        // Temperature normalises
+        var result = await detector.ProcessObservationAsync(
+            _encounterId, _patientId, "TEMP_C", 37.0m);
+
+        // TEMP_C key must be gone from Redis
+        var tempKeyExists = await cache.KeyExistsAsync(
+            SirsEvaluator.CriterionKey(_encounterId, "TEMP_C"));
+        tempKeyExists.Should().BeFalse("a cleared criterion must be deleted from Redis immediately");
+
+        // HEART_RATE key must still exist (criterion still met)
+        var hrKeyExists = await cache.KeyExistsAsync(
+            SirsEvaluator.CriterionKey(_encounterId, "HEART_RATE"));
+        hrKeyExists.Should().BeTrue("an active criterion must remain until its own TTL or a clearing observation");
+
+        // Active count is now 1, but alert must stay open
+        result.Outcome.Should().Be(SirsOutcome.InsufficientCriteria);
+        result.ActiveCount.Should().Be(1);
+
+        var alert = await db.ClinicalAlerts.SingleAsync();
+        alert.Status.Should().Be(AlertStatus.Open,
+            "the existing alert is not auto-resolved when criteria drop below 2 — " +
+            "clinical acknowledgment is required");
+    }
+
+    // Test 5: at-least-once redelivery — idempotency under simulated crash
+    [Fact]
+    public async Task DuplicateObservationEvent_AlertCreatedOnce()
+    {
+        using var scope = _fixture.Services.CreateScope();
+        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
+        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
+
+        await detector.ProcessObservationAsync(_encounterId, _patientId, "HEART_RATE", 95m);
+
+        // Simulate: the consumer crashes after this call completes but before committing
+        // the Kafka offset. On restart, the same observation is redelivered.
+        await detector.ProcessObservationAsync(_encounterId, _patientId, "TEMP_C", 38.5m);
+        await detector.ProcessObservationAsync(_encounterId, _patientId, "TEMP_C", 38.5m); // duplicate
+
+        var alertCount = await db.ClinicalAlerts.CountAsync();
+        alertCount.Should().Be(1, "WHERE NOT EXISTS prevents duplicate alert on redelivery");
+
+        var outboxCount = await db.OutboxEvents.CountAsync();
+        outboxCount.Should().Be(1, "outbox event must be written exactly once");
+    }
+
+    // Test 6: non-SIRS code — engine ignores it entirely
+    [Fact]
+    public async Task NonSirsCode_NoRedisInteraction()
+    {
+        using var scope = _fixture.Services.CreateScope();
+        var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
+        var redis = scope.ServiceProvider.GetRequiredService<IConnectionMultiplexer>();
+
+        var result = await detector.ProcessObservationAsync(
+            _encounterId, _patientId, "POTASSIUM_MEQ_L", 3.2m);
+
+        result.Outcome.Should().Be(SirsOutcome.NotSirsCode);
+
+        // No SIRS keys were created for this encounter
+        var anyKey = await redis.GetDatabase()
+            .KeyExistsAsync(SirsEvaluator.CriterionKey(_encounterId, "POTASSIUM_MEQ_L"));
+        anyKey.Should().BeFalse();
+    }
+}
\ No newline at end of file
diff --git a/VigilCareClinicalAPI.Tests/SirsEvaluatorTests.cs b/VigilCareClinicalAPI.Tests/SirsEvaluatorTests.cs
new file mode 100644
index 0000000..9be202e
--- /dev/null
+++ b/VigilCareClinicalAPI.Tests/SirsEvaluatorTests.cs
@@ -0,0 +1,30 @@
+using FluentAssertions;
+
+public class SirsEvaluatorTests
+{
+    [Theory]
+    [InlineData("TEMP_C",     38.4,  true)]   // fever
+    [InlineData("TEMP_C",     35.9,  true)]   // hypothermia
+    [InlineData("TEMP_C",     37.0,  false)]  // normal
+    [InlineData("HEART_RATE", 91,    true)]
+    [InlineData("HEART_RATE", 90,    false)]  // boundary: 90 is NOT tachycardia (> not >=)
+    [InlineData("RESP_RATE",  21,    true)]
+    [InlineData("RESP_RATE",  20,    false)]  // boundary
+    [InlineData("WBC_K_UL",   12.1,  true)]   // leukocytosis
+    [InlineData("WBC_K_UL",   3.9,   true)]   // leukopenia
+    [InlineData("WBC_K_UL",   8.0,   false)]  // normal
+    [InlineData("POTASSIUM_MEQ_L", 4.0, false)] // not a SIRS code
+    public void MeetsCriterion_ReturnsExpected(string code, double value, bool expected)
+    {
+        SirsEvaluator.MeetsCriterion(code, (decimal)value).Should().Be(expected);
+    }
+
+    [Fact]
+    public void AllCriterionKeys_ReturnsFourKeys_AllDistinct()
+    {
+        var id = Guid.NewGuid();
+        var keys = SirsEvaluator.AllCriterionKeys(id);
+        keys.Should().HaveCount(4);
+        keys.Select(k => k.ToString()).Should().OnlyHaveUniqueItems();
+    }
+}
\ No newline at end of file
diff --git a/VigilCareClinicalAPI/BackgroundServices/SepsisEngineService.cs b/VigilCareClinicalAPI/BackgroundServices/SepsisEngineService.cs
new file mode 100644
index 0000000..e9995be
--- /dev/null
+++ b/VigilCareClinicalAPI/BackgroundServices/SepsisEngineService.cs
@@ -0,0 +1,98 @@
+using System.Text.Json;
+using Confluent.Kafka;
+using Microsoft.Extensions.Options;
+
+public class SepsisEngineService : BackgroundService
+{
+    private static readonly JsonSerializerOptions EventJsonOptions = new()
+    {
+        PropertyNameCaseInsensitive = true
+    };
+
+    private readonly IServiceProvider _services;
+    private readonly KafkaOptions _kafkaOptions;
+    private readonly ILogger<SepsisEngineService> _logger;
+
+    public SepsisEngineService(
+        IServiceProvider services,
+        IOptions<KafkaOptions> kafkaOptions,
+        ILogger<SepsisEngineService> logger)
+    {
+        _services = services;
+        _kafkaOptions = kafkaOptions.Value;
+        _logger = logger;
+    }
+
+    protected override async Task ExecuteAsync(CancellationToken stoppingToken)
+    {
+        var config = new ConsumerConfig
+        {
+            BootstrapServers = _kafkaOptions.BootstrapServers,
+            GroupId = "sepsis-engine",
+            AutoOffsetReset = AutoOffsetReset.Earliest,
+            EnableAutoCommit = false
+        };
+
+        using var consumer = new ConsumerBuilder<string, string>(config).Build();
+        // Subscribes to observation.recorded only.
+        // The es-indexer consumes all three topics; the sepsis engine only needs one.
+        // Subscribing to a superset of needed topics would waste CPU deserializing
+        // alert and encounter events that this engine discards immediately.
+        consumer.Subscribe(_kafkaOptions.Topics.ObservationRecorded);
+
+        _logger.LogInformation("SepsisEngineService started — consumer group: sepsis-engine");
+
+        try
+        {
+            while (!stoppingToken.IsCancellationRequested)
+            {
+                ConsumeResult<string, string>? result = null;
+                try
+                {
+                    result = consumer.Consume(stoppingToken);
+
+                    var evt = JsonSerializer.Deserialize<SepsisObservationEvent>(
+                        result.Message.Value, EventJsonOptions)!;
+
+                    // Create a scope per message — SirsDetector is scoped and
+                    // owns a fresh DbContext for each observation processed.
+                    using var scope = _services.CreateScope();
+                    var detector = scope.ServiceProvider.GetRequiredService<SirsDetector>();
+
+                    var outcome = await detector.ProcessObservationAsync(
+                        evt.EncounterId,
+                        evt.PatientId,
+                        evt.ObservationCode,
+                        evt.Value,
+                        stoppingToken);
+
+                    if (outcome.Outcome == SirsOutcome.AlertCreated)
+                        _logger.LogWarning(
+                            "SEPSIS_WARNING created via SepsisEngine " +
+                            "— encounter={EncounterId} code={Code} value={Value}",
+                            evt.EncounterId, evt.ObservationCode, evt.Value);
+
+                    // Commit only after successful processing.
+                    consumer.Commit(result);
+                }
+                catch (OperationCanceledException)
+                {
+                    break;
+                }
+                catch (Exception ex)
+                {
+                    _logger.LogError(ex,
+                        "SepsisEngine failed on topic={Topic} offset={Offset} — not committing",
+                        result?.Topic, result?.Offset.Value);
+                    // Back off before retrying so a persistent failure (e.g., Redis down)
+                    // does not spin the loop at maximum throughput.
+                    await Task.Delay(2000, stoppingToken);
+                }
+            }
+        }
+        finally
+        {
+            consumer.Close();
+        }
+    }
+}
\ No newline at end of file
diff --git a/VigilCareClinicalAPI/Data/Seed/DataSeeder.cs b/VigilCareClinicalAPI/Data/Seed/DataSeeder.cs
index a804d3b..3d0d689 100644
--- a/VigilCareClinicalAPI/Data/Seed/DataSeeder.cs
+++ b/VigilCareClinicalAPI/Data/Seed/DataSeeder.cs
@@ -62,6 +62,20 @@ public static class DataSeeder
                 Id = Guid.NewGuid(), ObservationCode = "SPO2", DisplayName = "Oxygen Saturation",
                 Unit = "%", CriticalLow = 88, WarningLow = 92, WarningHigh = null, CriticalHigh = null,
                 CreatedAt = DateTimeOffset.UtcNow
+            },
+            new AlertThreshold
+            {
+                Id = Guid.NewGuid(), ObservationCode = "RESP_RATE",
+                DisplayName = "Respiratory Rate", Unit = "breaths/min",
+                CriticalLow = null, WarningLow = 12m, WarningHigh = 20m, CriticalHigh = 30m,
+                CreatedAt = DateTimeOffset.UtcNow
+            },
+            new AlertThreshold
+            {
+                Id = Guid.NewGuid(), ObservationCode = "WBC_K_UL",
+                DisplayName = "White Blood Cell Count", Unit = "k/µL",
+                CriticalLow = 2.0m, WarningLow = 4.0m, WarningHigh = 12.0m, CriticalHigh = 20.0m,
+                CreatedAt = DateTimeOffset.UtcNow
             }
         };
         db.AlertThresholds.AddRange(thresholds);
diff --git a/VigilCareClinicalAPI/Models/Records/Sepsis/SepsisObservationEvent.cs b/VigilCareClinicalAPI/Models/Records/Sepsis/SepsisObservationEvent.cs
new file mode 100644
index 0000000..bdf7a6d
--- /dev/null
+++ b/VigilCareClinicalAPI/Models/Records/Sepsis/SepsisObservationEvent.cs
@@ -0,0 +1,6 @@
+// Subset of the observation.recorded payload — only the fields the sepsis engine needs.
+public record SepsisObservationEvent(
+    Guid EncounterId,
+    Guid PatientId,
+    string ObservationCode,
+    decimal Value);
\ No newline at end of file
diff --git a/VigilCareClinicalAPI/Models/Records/Sepsis/SirsOutcome.cs b/VigilCareClinicalAPI/Models/Records/Sepsis/SirsOutcome.cs
new file mode 100644
index 0000000..d1e1705
--- /dev/null
+++ b/VigilCareClinicalAPI/Models/Records/Sepsis/SirsOutcome.cs
@@ -0,0 +1,7 @@
+public enum SirsOutcome
+{
+    NotSirsCode,
+    InsufficientCriteria,
+    AlertCreated,
+    AlertAlreadyOpen
+}
\ No newline at end of file
diff --git a/VigilCareClinicalAPI/Models/Records/Sepsis/SirsResult.cs b/VigilCareClinicalAPI/Models/Records/Sepsis/SirsResult.cs
new file mode 100644
index 0000000..3719fbc
--- /dev/null
+++ b/VigilCareClinicalAPI/Models/Records/Sepsis/SirsResult.cs
@@ -0,0 +1,11 @@
+// Discriminated result — allows tests and callers to assert the exact outcome
+// without inspecting PostgreSQL or Redis directly.
+public record SirsResult(SirsOutcome Outcome, int ActiveCount = 0)
+{
+    public static readonly SirsResult NotSirsCode           = new(SirsOutcome.NotSirsCode);
+    public static readonly SirsResult AlertCreated          = new(SirsOutcome.AlertCreated);
+    public static readonly SirsResult AlertAlreadyOpen      = new(SirsOutcome.AlertAlreadyOpen);
+
+    public static SirsResult InsufficientCriteria(int count) =>
+        new(SirsOutcome.InsufficientCriteria, count);
+}
\ No newline at end of file
diff --git a/VigilCareClinicalAPI/Program.cs b/VigilCareClinicalAPI/Program.cs
index 2ca9f70..e79f8ec 100644
--- a/VigilCareClinicalAPI/Program.cs
+++ b/VigilCareClinicalAPI/Program.cs
@@ -12,10 +12,15 @@ try
 {    
     var builder = WebApplication.CreateBuilder(args);
 
-    builder.Host.UseSerilog((ctx, services, config) =>
-        config.ReadFrom.Configuration(ctx.Configuration)
-              .ReadFrom.Services(services)
-              .Enrich.FromLogContext());
+    // Serilog's reloadable logger can only be frozen once per process; skip in
+    // integration tests where WebApplicationFactory may build multiple hosts.
+    if (!builder.Environment.IsEnvironment("Testing"))
+    {
+        builder.Host.UseSerilog((ctx, services, config) =>
+            config.ReadFrom.Configuration(ctx.Configuration)
+                  .ReadFrom.Services(services)
+                  .Enrich.FromLogContext());
+    }
 
     builder.Services.AddDbContext<AppDbContext>(opts =>
         opts.UseNpgsql(builder.Configuration.GetConnectionString("DefaultConnection")));
@@ -43,12 +48,14 @@ try
     builder.Services.AddScoped<IObservationQueryService, ObservationQueryService>();
     builder.Services.AddScoped<IAlertService, AlertService>();
     builder.Services.AddScoped<IAnalyticsService, AnalyticsService>();
+    builder.Services.AddScoped<SirsDetector>();
 
     builder.Services.AddHostedService<ThresholdCacheLoader>();
     builder.Services.AddHostedService<KafkaTopicProvisioner>();
     builder.Services.AddHostedService<OutboxRelayService>();
     builder.Services.AddHostedService<ElasticIndexProvisioner>();
     builder.Services.AddHostedService<EsIndexerService>();
+    builder.Services.AddHostedService<SepsisEngineService>();
 
     builder.Services.AddControllers()
         .AddJsonOptions(opts =>
@@ -70,11 +77,14 @@ try
         await DataSeeder.SeedAsync(db, redis);
     }
 
-    app.UseSerilogRequestLogging(options =>
+    if (!app.Environment.IsEnvironment("Testing"))
     {
-        options.MessageTemplate =
-            "HTTP {RequestMethod} {RequestPath} responded {StatusCode} in {Elapsed:0.000}ms";
-    });
+        app.UseSerilogRequestLogging(options =>
+        {
+            options.MessageTemplate =
+                "HTTP {RequestMethod} {RequestPath} responded {StatusCode} in {Elapsed:0.000}ms";
+        });
+    }
 
     app.UseMiddleware<CorrelationIdMiddleware>();
     app.UseMiddleware<ExceptionHandlerMiddleware>();
diff --git a/VigilCareClinicalAPI/Sepsis/SirsDetector.cs b/VigilCareClinicalAPI/Sepsis/SirsDetector.cs
new file mode 100644
index 0000000..8b4d5f4
--- /dev/null
+++ b/VigilCareClinicalAPI/Sepsis/SirsDetector.cs
@@ -0,0 +1,161 @@
+using System.Text.Json;
+using Microsoft.EntityFrameworkCore;
+using StackExchange.Redis;
+
+public class SirsDetector
+{
+    // 30 minutes in seconds. This is a clinical parameter: SIRS criteria evaluated
+    // outside a 30-minute window are clinically stale. The TTL enforces the window
+    // automatically — no cleanup job required.
+    private const int SirsTtlSeconds = 1800;
+
+    private readonly IConnectionMultiplexer _redis;
+    private readonly IServiceProvider _services;
+    private readonly ILogger<SirsDetector> _logger;
+
+    public SirsDetector(
+        IConnectionMultiplexer redis,
+        IServiceProvider services,
+        ILogger<SirsDetector> logger)
+    {
+        _redis = redis;
+        _services = services;
+        _logger = logger;
+    }
+
+    public async Task<SirsResult> ProcessObservationAsync(
+        Guid encounterId,
+        Guid patientId,
+        string observationCode,
+        decimal value,
+        CancellationToken ct = default)
+    {
+        // Fast exit for non-SIRS codes. The sepsis engine subscribes to the full
+        // observation.recorded stream — the majority of messages (SpO2, potassium, glucose)
+        // are not SIRS-relevant and are discarded here without touching Redis or PostgreSQL.
+        if (!SirsEvaluator.SirsCodes.Contains(observationCode))
+            return SirsResult.NotSirsCode;
+
+        var cache = _redis.GetDatabase();
+        var key = SirsEvaluator.CriterionKey(encounterId, observationCode);
+
+        if (SirsEvaluator.MeetsCriterion(observationCode, value))
+        {
+            // SET with EX refreshes the TTL on every qualifying observation.
+            // A patient with tachycardia posting a reading every 60 seconds will keep
+            // sirs:{id}:HEART_RATE alive for 30 minutes after the LAST qualifying reading,
+            // not the first — the window slides forward with each new abnormal value.
+            await cache.StringSetAsync(key, "1", TimeSpan.FromSeconds(SirsTtlSeconds));
+
+            _logger.LogDebug("SIRS criterion set: {Key} (TTL={Ttl}s)", key, SirsTtlSeconds);
+        }
+        else
+        {
+            // Criterion no longer met — remove the key immediately rather than waiting
+            // for TTL expiry. If a patient's temperature normalises at 37.0 °C, the
+            // fever criterion must stop contributing to the count right away.
+            // Without this DEL, a recovered criterion could persist for up to 30 minutes
+            // and falsely sustain a SEPSIS_WARNING count.
+            await cache.KeyDeleteAsync(key);
+
+            _logger.LogDebug("SIRS criterion cleared: {Key}", key);
+        }
+
+        // Count active criteria in one MGET round-trip.
+        // MGET is O(N) where N = number of keys requested (4 here, always).
+        // Never use KEYS pattern for this check: KEYS scans the entire keyspace
+        // and blocks all other Redis operations until the scan completes.
+        var allKeys = SirsEvaluator.AllCriterionKeys(encounterId);
+        var values = await cache.StringGetAsync(allKeys);
+        var activeCount = values.Count(v => v.HasValue);
+
+        _logger.LogDebug(
+            "SIRS state for encounter {Id}: {Active}/4 criteria active after {Code}={Value}",
+            encounterId, activeCount, observationCode, value);
+
+        if (activeCount < 2)
+            return SirsResult.InsufficientCriteria(activeCount);
+
+        // Two or more criteria are active — attempt to create the alert.
+        var created = await TryCreateAlertAsync(encounterId, patientId, activeCount, ct);
+        return created ? SirsResult.AlertCreated : SirsResult.AlertAlreadyOpen;
+    }
+
+    // Creates the SEPSIS_WARNING alert and its outbox event in one atomic transaction.
+    // The INSERT WHERE NOT EXISTS pattern makes this safe under at-least-once delivery:
+    // if the consumer crashes after the INSERT but before committing the Kafka offset,
+    // the observation is reprocessed on restart. The second run hits the WHERE NOT EXISTS
+    // subquery, finds the existing open alert, inserts 0 rows, and returns false — no
+    // duplicate alert, no duplicate outbox event.
+    private async Task<bool> TryCreateAlertAsync(
+        Guid encounterId,
+        Guid patientId,
+        int activeCount,
+        CancellationToken ct)
+    {
+        using var scope = _services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<AppDbContext>();
+
+        await using var tx = await db.Database.BeginTransactionAsync(ct);
+
+        var alertId = Guid.NewGuid();
+        var triggeredAt = DateTimeOffset.UtcNow;
+        var details =
+            $"SIRS criteria met: {activeCount} of 4 criteria active within the 30-minute window.";
+
+        // One SQL round-trip: check + insert atomically.
+        // status IN ('OPEN', 'ESCALATED') prevents re-creating an alert that has been
+        // escalated but not yet resolved — the patient is still in danger.
+        var affected = await db.Database.ExecuteSqlInterpolatedAsync($"""
+            INSERT INTO clinical_alerts
+                (id, encounter_id, patient_id, alert_type, severity, details, status, triggered_at)
+            SELECT {alertId}, {encounterId}, {patientId},
+                   'SEPSIS_WARNING', 'CRITICAL', {details}, 'OPEN', {triggeredAt}
+            WHERE NOT EXISTS (
+                SELECT 1 FROM clinical_alerts
+                WHERE  encounter_id = {encounterId}
+                  AND  alert_type   = 'SEPSIS_WARNING'
+                  AND  status       IN ('OPEN', 'ESCALATED')
+            )
+            """, ct);
+
+        if (affected == 0)
+        {
+            await tx.RollbackAsync(ct);
+            _logger.LogDebug(
+                "SEPSIS_WARNING already open for encounter {Id} — no new alert", encounterId);
+            return false;
+        }
+
+        // Alert was created — write the outbox event in the same transaction.
+        // The relay (Phase 3) will publish to alert.generated, which Phase 6's
+        // notification worker reads to page the attending physician via RabbitMQ.
+        db.OutboxEvents.Add(new OutboxEvent
+        {
+            Id = Guid.NewGuid(),
+            Topic = "alert.generated",
+            Payload = JsonSerializer.Serialize(new
+            {
+                alertId,
+                encounterId,
+                patientId,
+                alertType = AlertType.SepsisWarning.ToDbString(),
+                severity  = "Critical",
+                triggeredAt,
+                partitionKey = encounterId.ToString()
+            }),
+            PartitionKey = encounterId.ToString(),
+            CreatedAt = DateTimeOffset.UtcNow
+        });
+
+        await db.SaveChangesAsync(ct);
+        await tx.CommitAsync(ct);
+
+        _logger.LogWarning(
+            "SEPSIS_WARNING alert {AlertId} created for encounter {EncounterId} " +
+            "— {Active}/4 SIRS criteria active",
+            alertId, encounterId, activeCount);
+
+        return true;
+    }
+}
\ No newline at end of file
diff --git a/VigilCareClinicalAPI/Sepsis/SirsEvaluator.cs b/VigilCareClinicalAPI/Sepsis/SirsEvaluator.cs
new file mode 100644
index 0000000..3d75fab
--- /dev/null
+++ b/VigilCareClinicalAPI/Sepsis/SirsEvaluator.cs
@@ -0,0 +1,38 @@
+using StackExchange.Redis;
+
+public static class SirsEvaluator
+{
+    // The four SIRS codes defined by this project's simplified SIRS criteria.
+    // Observations for any other code are ignored by the sepsis engine entirely —
+    // they pass through to the outbox and Elasticsearch but do not affect SIRS state.
+    public static readonly IReadOnlySet<string> SirsCodes =
+        new HashSet<string> { "TEMP_C", "HEART_RATE", "RESP_RATE", "WBC_K_UL" };
+
+    // Returns true if the observation value meets the SIRS criterion for its code.
+    // These thresholds are clinical parameters, not configuration — changing them
+    // requires clinical review, not a config file edit. They live here as named constants.
+    public static bool MeetsCriterion(string observationCode, decimal value) =>
+        observationCode switch
+        {
+            // Fever (> 38.3 °C) or hypothermia (< 36.0 °C)
+            "TEMP_C"     => value > 38.3m || value < 36.0m,
+            // Tachycardia
+            "HEART_RATE" => value > 90m,
+            // Tachypnea
+            "RESP_RATE"  => value > 20m,
+            // Leukocytosis or leukopenia
+            "WBC_K_UL"   => value > 12.0m || value < 4.0m,
+            _             => false
+        };
+
+    // Redis key for one SIRS criterion for one encounter.
+    public static string CriterionKey(Guid encounterId, string code) =>
+        $"sirs:{encounterId}:{code}";
+
+    // All four Redis keys for one encounter — used in MGET to count active criteria.
+    // The order is stable so the MGET result array always maps to the same codes.
+    public static RedisKey[] AllCriterionKeys(Guid encounterId) =>
+        SirsCodes
+            .Select(code => (RedisKey)CriterionKey(encounterId, code))
+            .ToArray();
+}
\ No newline at end of file
diff --git a/docs/decisions/sepsis-engine-design.md b/docs/decisions/sepsis-engine-design.md
new file mode 100644
index 0000000..7b486f4
--- /dev/null
+++ b/docs/decisions/sepsis-engine-design.md
@@ -0,0 +1,53 @@
+```markdown
+# Sepsis Engine Design Decisions
+
+## Why Redis for SIRS state, not a PostgreSQL time-range query
+
+At a medium hospital with 200 concurrent inpatients, each generating five observations
+per patient per minute, the sepsis engine processes approximately 17 observation events
+per second at steady state.
+
+A PostgreSQL alternative would look like this on every event:
+
+```sql
+SELECT observation_code
+FROM observations
+WHERE encounter_id = :encounterId
+  AND observation_code IN ('TEMP_C', 'HEART_RATE', 'RESP_RATE', 'WBC_K_UL')
+  AND recorded_at >= NOW() - INTERVAL '30 minutes'
+  AND (
+      (observation_code = 'TEMP_C'     AND (value > 38.3 OR value < 36.0)) OR
+      (observation_code = 'HEART_RATE' AND value > 90)                      OR
+      (observation_code = 'RESP_RATE'  AND value > 20)                      OR
+      (observation_code = 'WBC_K_UL'  AND (value > 12.0 OR value < 4.0))
+  );
+```
+
+This query hits the `observations` table on every event. Under load it competes for
+I/O with the ingest path writing new rows — both want the same composite index. With
+Redis: four `SET`/`DEL` operations and one `MGET`, all O(1), all in-memory. No disk
+I/O, no lock contention with the write path.
+
+The TTL enforces the 30-minute sliding window automatically. Without Redis (or an
+equivalent in-memory store), a background job would be needed to clean up stale
+criteria — another failure point, another deployment concern.
+
+## Why not Apache Flink
+
+Flink is a distributed stream processor designed for stateful computation at scale
+(millions of events per second across a fleet). It brings real costs:
+
+- A Flink cluster (JobManager + TaskManagers) is infrastructure that must be deployed,
+  monitored, and upgraded independently of the application.
+- Flink state backends (RocksDB, heap) add operational complexity that is not
+  justified unless the stream volume saturates what a single consumer thread can handle.
+- Flink's exactly-once semantics require Kafka transactions, which add latency and
+  require tuning separate from the rest of the application.
+
+At a single hospital (200 inpatients, ~17 observations/second), a Kafka consumer +
+Redis state store handles the volume with single-digit millisecond latency per event
+and no additional infrastructure. The trade-off: if this system needed to scale to a
+multi-hospital network with 50,000+ concurrent inpatients (~5,000 observations/second),
+Flink would become the right choice. The architecture decision is correct at this scale
+and defensible at interview with a clear scale inflection point named.
+```
\ No newline at end of file
diff --git a/scripts/run-sepsis-sirs-tests.sh b/scripts/run-sepsis-sirs-tests.sh
new file mode 100755
index 0000000..945d0b5
--- /dev/null
+++ b/scripts/run-sepsis-sirs-tests.sh
@@ -0,0 +1,544 @@
+#!/usr/bin/env bash
+
+set -euo pipefail
+
+SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
+COMPOSE_FILE="${COMPOSE_FILE:-${SCRIPT_DIR}/../docker-compose.yml}"
+
+BASE_URL="${BASE_URL:-http://localhost:5270}"
+REDIS_PORT="${REDIS_PORT:-6382}"
+ES_URL="${ES_URL:-http://localhost:9200}"
+PGHOST="${PGHOST:-localhost}"
+PGPORT="${PGPORT:-5436}"
+PGDATABASE="${PGDATABASE:-vigilcare}"
+PGUSER="${PGUSER:-postgres}"
+PGPASSWORD="${PGPASSWORD:-password}"
+
+SEPSIS_CONSUMER_GROUP="${SEPSIS_CONSUMER_GROUP:-sepsis-engine}"
+ES_CONSUMER_GROUP="${ES_CONSUMER_GROUP:-es-indexer}"
+SEPSIS_WAIT_SECS="${SEPSIS_WAIT_SECS:-45}"
+INDEX_WAIT_SECS="${INDEX_WAIT_SECS:-60}"
+RELAY_WAIT_SECS="${RELAY_WAIT_SECS:-45}"
+KAFKA_READY_WAIT_SECS="${KAFKA_READY_WAIT_SECS:-30}"
+TTL_DECAY_WAIT_SECS="${TTL_DECAY_WAIT_SECS:-5}"
+
+SCRIPT_RUN_ID="$(date -u +"%Y%m%d%H%M%S")"
+RECORDED_AT="$(date -u +"%Y-%m-%dT%H:%M:%SZ")"
+
+TMP_FILES=()
+
+cleanup() {
+  local f
+  for f in "${TMP_FILES[@]}"; do
+    rm -f "${f}" "${f}.status" 2>/dev/null || true
+  done
+}
+trap cleanup EXIT
+
+if ! command -v curl >/dev/null 2>&1; then
+  echo "Missing dependency: curl"
+  exit 1
+fi
+
+if ! command -v jq >/dev/null 2>&1; then
+  echo "Missing dependency: jq"
+  exit 1
+fi
+
+if ! command -v docker >/dev/null 2>&1 || [[ ! -f "${COMPOSE_FILE}" ]]; then
+  echo "Missing dependency: docker compose (${COMPOSE_FILE})"
+  exit 1
+fi
+
+compose() {
+  docker compose -f "${COMPOSE_FILE}" "$@"
+}
+
+kafka_exec() {
+  compose exec -T kafka "$@"
+}
+
+redis_cmd() {
+  if command -v redis-cli >/dev/null 2>&1; then
+    redis-cli -p "${REDIS_PORT}" "$@"
+  else
+    compose exec -T redis redis-cli "$@"
+  fi
+}
+
+psql_cmd() {
+  local sql="$1"
+  if command -v psql >/dev/null 2>&1; then
+    PGPASSWORD="${PGPASSWORD}" psql -h "${PGHOST}" -p "${PGPORT}" -U "${PGUSER}" -d "${PGDATABASE}" -tAc "${sql}"
+  else
+    compose exec -T postgres psql -U "${PGUSER}" -d "${PGDATABASE}" -tAc "${sql}"
+  fi
+}
+
+request() {
+  local method="$1"
+  local url="$2"
+  local body="${3:-}"
+  local tmp_body
+  tmp_body="$(mktemp)"
+  TMP_FILES+=("${tmp_body}")
+  local status
+
+  if [[ -n "${body}" ]]; then
+    status="$(curl -sS -o "${tmp_body}" -w "%{http_code}" -X "${method}" "${url}" \
+      -H "Content-Type: application/json" -d "${body}")"
+  else
+    status="$(curl -sS -o "${tmp_body}" -w "%{http_code}" -X "${method}" "${url}")"
+  fi
+
+  echo "${status}" > "${tmp_body}.status"
+  echo "${tmp_body}"
+}
+
+assert_status() {
+  local expected="$1"
+  local body_file="$2"
+  local status
+  status="$(cat "${body_file}.status")"
+  if [[ "${status}" != "${expected}" ]]; then
+    echo "Expected HTTP ${expected}, got ${status}"
+    echo "Response body:"
+    cat "${body_file}"
+    echo
+    return 1
+  fi
+}
+
+ingest_observation() {
+  local encounter_id="$1"
+  local code="$2"
+  local value="$3"
+  local unit="$4"
+  local source="$5"
+  local recorded_at="$6"
+  local idempotency_key="$7"
+
+  local payload
+  payload="$(jq -nc \
+    --arg code "${code}" \
+    --argjson value "${value}" \
+    --arg unit "${unit}" \
+    --arg source "${source}" \
+    --arg recordedAt "${recorded_at}" \
+    --arg key "${idempotency_key}" \
+    '{observations:[{observationCode:$code,value:$value,unit:$unit,source:$source,recordedAt:$recordedAt,idempotencyKey:$key}]}')"
+
+  local resp
+  resp="$(request POST "${BASE_URL}/api/v1/encounters/${encounter_id}/observations" "${payload}")"
+  assert_status "201" "${resp}"
+}
+
+wait_for_kafka() {
+  local elapsed=0
+  while (( elapsed < KAFKA_READY_WAIT_SECS )); do
+    if kafka_exec /opt/kafka/bin/kafka-broker-api-versions.sh --bootstrap-server localhost:9092 >/dev/null 2>&1; then
+      return 0
+    fi
+    sleep 2
+    elapsed=$((elapsed + 2))
+  done
+  echo "Kafka did not become ready within ${KAFKA_READY_WAIT_SECS}s"
+  return 1
+}
+
+consumer_group_lag() {
+  local group="$1"
+  kafka_exec /opt/kafka/bin/kafka-consumer-groups.sh \
+    --bootstrap-server localhost:9092 \
+    --describe \
+    --group "${group}" 2>/dev/null | \
+    awk '/observation.recorded/ { sum += $6 } END { print sum + 0 }'
+}
+
+wait_for_consumer_lag_zero() {
+  local group="$1"
+  local elapsed=0
+  while (( elapsed < SEPSIS_WAIT_SECS )); do
+    local lag
+    lag="$(consumer_group_lag "${group}")"
+    if [[ "${lag}" == "0" ]]; then
+      return 0
+    fi
+    sleep 1
+    elapsed=$((elapsed + 1))
+  done
+  echo "Consumer group ${group} lag did not reach zero within ${SEPSIS_WAIT_SECS}s (lag=${lag:-unknown})"
+  return 1
+}
+
+wait_for_sepsis_alert() {
+  local encounter_id="$1"
+  local elapsed=0
+  while (( elapsed < SEPSIS_WAIT_SECS )); do
+    local count
+    count="$(psql_cmd "SELECT COUNT(*) FROM clinical_alerts WHERE encounter_id = '${encounter_id}' AND alert_type = 'SEPSIS_WARNING' AND status = 'OPEN'")"
+    if [[ "${count}" == "1" ]]; then
+      return 0
+    fi
+    sleep 1
+    elapsed=$((elapsed + 1))
+  done
+  echo "SEPSIS_WARNING alert not found for encounter ${encounter_id} within ${SEPSIS_WAIT_SECS}s"
+  return 1
+}
+
+wait_for_outbox_processed() {
+  local outbox_id="$1"
+  local elapsed=0
+  while (( elapsed < RELAY_WAIT_SECS )); do
+    local processed
+    processed="$(psql_cmd "SELECT processed_at IS NOT NULL FROM outbox_events WHERE id = '${outbox_id}'")"
+    if [[ "${processed}" == "t" ]]; then
+      return 0
+    fi
+    sleep 1
+    elapsed=$((elapsed + 1))
+  done
+  echo "Outbox row ${outbox_id} was not processed within ${RELAY_WAIT_SECS}s"
+  return 1
+}
+
+latest_observation_outbox_id() {
+  local encounter_id="$1"
+  psql_cmd "SELECT id FROM outbox_events WHERE topic = 'observation.recorded' AND partition_key = '${encounter_id}' ORDER BY created_at DESC LIMIT 1"
+}
+
+# Observation ingest writes outbox first; relay publishes to Kafka; sepsis-engine consumes.
+# Consumer lag alone is not enough — lag can be 0 before the relay publishes the new event.
+wait_for_observation_pipeline() {
+  local encounter_id="$1"
+  local outbox_id
+  outbox_id="$(latest_observation_outbox_id "${encounter_id}")"
+  if [[ -z "${outbox_id}" ]]; then
+    echo "No observation.recorded outbox row for encounter ${encounter_id}"
+    return 1
+  fi
+  wait_for_outbox_processed "${outbox_id}"
+  wait_for_consumer_lag_zero "${SEPSIS_CONSUMER_GROUP}"
+}
+
+redis_get() {
+  local value
+  value="$(redis_cmd GET "$1" | tr -d '\r')"
+  if [[ "${value}" == "(nil)" ]]; then
+    echo ""
+  else
+    echo "${value}"
+  fi
+}
+
+redis_ttl() {
+  redis_cmd TTL "$1" | tr -d '\r'
+}
+
+sirs_key() {
+  local encounter_id="$1"
+  local code="$2"
+  echo "sirs:${encounter_id}:${code}"
+}
+
+TOTAL_STEPS=10
+
+echo "Running sepsis / SIRS verification against ${BASE_URL}"
+echo "Script run id: ${SCRIPT_RUN_ID}"
+
+echo ""
+echo "[0/${TOTAL_STEPS}] Preflight — API, Postgres, Redis, Kafka, and Elasticsearch reachable"
+preflight_status="$(curl -sS -o /dev/null -w "%{http_code}" "${BASE_URL}/api/v1/alert-thresholds" || true)"
+if [[ "${preflight_status}" != "200" ]]; then
+  echo "API not reachable at ${BASE_URL} (HTTP ${preflight_status})."
+  echo "Start the API with: dotnet run --project VigilCareClinicalAPI"
+  exit 1
+fi
+
+if ! psql_cmd "SELECT 1" >/dev/null 2>&1; then
+  echo "Postgres not reachable on ${PGHOST}:${PGPORT}."
+  echo "Start the stack with: docker compose up -d"
+  exit 1
+fi
+
+if ! redis_cmd PING >/dev/null 2>&1; then
+  echo "Redis not reachable on port ${REDIS_PORT}."
+  exit 1
+fi
+
+if ! wait_for_kafka; then
+  exit 1
+fi
+
+es_health_status="$(curl -sS "${ES_URL}/_cluster/health" | jq -r '.status' || true)"
+if [[ "${es_health_status}" != "green" && "${es_health_status}" != "yellow" ]]; then
+  echo "Elasticsearch cluster health is '${es_health_status}' (expected green or yellow)."
+  exit 1
+fi
+echo "OK: API, Postgres, Redis, Kafka, and Elasticsearch are up (cluster=${es_health_status})"
+
+echo ""
+echo "[1/${TOTAL_STEPS}] Creating patient, encounter, and baseline critical potassium alert"
+patient_payload='{"firstName":"SIRS","lastName":"Verifier","dateOfBirth":"1975-04-12","gender":"M"}'
+resp="$(request POST "${BASE_URL}/api/v1/patients" "${patient_payload}")"
+assert_status "201" "${resp}"
+patient_id="$(jq -r '.data.id' "${resp}")"
+
+enc_payload='{"encounterType":"Inpatient","department":"ICU","attendingPhysician":"Dr. SIRS"}'
+resp="$(request POST "${BASE_URL}/api/v1/patients/${patient_id}/encounters" "${enc_payload}")"
+assert_status "201" "${resp}"
+encounter_id="$(jq -r '.data.id' "${resp}")"
+echo "OK: patient ${patient_id}, encounter ${encounter_id}"
+
+critical_payload="$(jq -nc \
+  --arg recordedAt "${RECORDED_AT}" \
+  --arg key "sirs-potassium-${SCRIPT_RUN_ID}" \
+  '{observations:[{observationCode:"POTASSIUM_MEQ_L",value:2.1,unit:"mEq/L",source:"LAB",recordedAt:$recordedAt,idempotencyKey:$key}]}')"
+resp="$(request POST "${BASE_URL}/api/v1/encounters/${encounter_id}/observations" "${critical_payload}")"
+assert_status "201" "${resp}"
+if [[ "$(jq -r '.data.alertGenerated' "${resp}")" != "true" ]]; then
+  echo "Expected critical potassium ingest to generate an alert"
+  exit 1
+fi
+echo "OK: baseline critical alert ingested (for openAlertCount=2 after sepsis)"
+
+echo ""
+echo "[2/${TOTAL_STEPS}] End-to-end SIRS — tachycardia sets Redis key, no SEPSIS_WARNING yet"
+ingest_observation "${encounter_id}" "HEART_RATE" 95 "bpm" "DEVICE" "${RECORDED_AT}" \
+  "sirs-hr1-${SCRIPT_RUN_ID}"
+
+if ! wait_for_observation_pipeline "${encounter_id}"; then
+  exit 1
+fi
+
+hr_key="$(sirs_key "${encounter_id}" "HEART_RATE")"
+hr_value="$(redis_get "${hr_key}")"
+if [[ "${hr_value}" != "1" ]]; then
+  echo "Expected Redis ${hr_key} = 1, got '${hr_value}'"
+  exit 1
+fi
+
+hr_ttl="$(redis_ttl "${hr_key}")"
+if [[ "${hr_ttl}" -lt 1500 || "${hr_ttl}" -gt 1800 ]]; then
+  echo "Expected HEART_RATE TTL between 1500 and 1800, got ${hr_ttl}"
+  exit 1
+fi
+
+sepsis_count="$(psql_cmd "SELECT COUNT(*) FROM clinical_alerts WHERE encounter_id = '${encounter_id}' AND alert_type = 'SEPSIS_WARNING'")"
+if [[ "${sepsis_count}" != "0" ]]; then
+  echo "Expected no SEPSIS_WARNING after one criterion, got count=${sepsis_count}"
+  exit 1
+fi
+echo "OK: HEART_RATE key set (TTL=${hr_ttl}s), no sepsis alert yet"
+
+echo ""
+echo "[3/${TOTAL_STEPS}] End-to-end SIRS — fever triggers SEPSIS_WARNING through Kafka pipeline"
+recorded_fever="$(date -u +"%Y-%m-%dT%H:%M:%SZ")"
+ingest_observation "${encounter_id}" "TEMP_C" 38.5 "°C" "DEVICE" "${recorded_fever}" \
+  "sirs-temp-${SCRIPT_RUN_ID}"
+
+if ! wait_for_observation_pipeline "${encounter_id}"; then
+  exit 1
+fi
+
+if ! wait_for_sepsis_alert "${encounter_id}"; then
+  exit 1
+fi
+
+alert_row="$(psql_cmd "SELECT alert_type || '|' || severity || '|' || status FROM clinical_alerts WHERE encounter_id = '${encounter_id}' AND alert_type = 'SEPSIS_WARNING' LIMIT 1")"
+if [[ "${alert_row}" != "SEPSIS_WARNING|CRITICAL|OPEN" ]]; then
+  echo "Unexpected SEPSIS_WARNING row: '${alert_row}'"
+  exit 1
+fi
+echo "OK: SEPSIS_WARNING created (type=SEPSIS_WARNING, severity=CRITICAL, status=OPEN)"
+
+echo ""
+echo "[4/${TOTAL_STEPS}] Verifying alert.generated outbox row for sepsis alert"
+outbox_row="$(psql_cmd "SELECT topic || '|' || partition_key FROM outbox_events WHERE topic = 'alert.generated' AND partition_key = '${encounter_id}' ORDER BY created_at DESC LIMIT 1")"
+if [[ "${outbox_row}" != "alert.generated|${encounter_id}" ]]; then
+  echo "Expected alert.generated outbox row for encounter ${encounter_id}, got '${outbox_row}'"
+  exit 1
+fi
+
+sepsis_outbox_id="$(psql_cmd "SELECT id FROM outbox_events WHERE topic = 'alert.generated' AND partition_key = '${encounter_id}' ORDER BY created_at DESC LIMIT 1")"
+wait_for_outbox_processed "${sepsis_outbox_id}"
+echo "OK: alert.generated outbox row exists and was relayed"
+
+echo ""
+echo "[5/${TOTAL_STEPS}] Verifying SirsDetector uses MGET (one round-trip for four keys)"
+monitor_out="$(mktemp)"
+TMP_FILES+=("${monitor_out}")
+
+redis_cmd MONITOR > "${monitor_out}" 2>&1 &
+monitor_pid=$!
+sleep 0.5
+
+recorded_resp="$(date -u +"%Y-%m-%dT%H:%M:%SZ")"
+ingest_observation "${encounter_id}" "RESP_RATE" 22 "breaths/min" "DEVICE" "${recorded_resp}" \
+  "sirs-resp-monitor-${SCRIPT_RUN_ID}"
+
+if ! wait_for_observation_pipeline "${encounter_id}"; then
+  kill "${monitor_pid}" 2>/dev/null || true
+  exit 1
+fi
+
+sleep 1
+kill "${monitor_pid}" 2>/dev/null || true
+wait "${monitor_pid}" 2>/dev/null || true
+
+if grep -qi '"keys"' "${monitor_out}"; then
+  echo "MONITOR output contains KEYS — SirsDetector must not scan the keyspace"
+  exit 1
+fi
+
+mget_line="$(grep -i 'mget' "${monitor_out}" | grep -F "sirs:${encounter_id}" | head -n 1 || true)"
+if [[ -z "${mget_line}" ]]; then
+  echo "No MGET command found in Redis MONITOR output for encounter ${encounter_id}"
+  echo "MONITOR tail:"
+  tail -n 20 "${monitor_out}"
+  exit 1
+fi
+
+for code in TEMP_C HEART_RATE RESP_RATE WBC_K_UL; do
+  if ! grep -F "sirs:${encounter_id}:${code}" <<< "${mget_line}" >/dev/null; then
+    echo "MGET line missing key sirs:${encounter_id}:${code}"
+    echo "MGET line: ${mget_line}"
+    exit 1
+  fi
+done
+
+sirs_get_count="$(grep -cE '"get".*sirs:'"${encounter_id}" "${monitor_out}" || true)"
+if [[ "${sirs_get_count}" -ge 4 ]]; then
+  echo "Found ${sirs_get_count} individual GET commands on SIRS keys — expected MGET instead"
+  exit 1
+fi
+echo "OK: single MGET with all four SIRS keys observed"
+
+echo ""
+echo "[6/${TOTAL_STEPS}] Verifying TTL sliding window on HEART_RATE key"
+ttl_before_decay="$(redis_ttl "${hr_key}")"
+if (( TTL_DECAY_WAIT_SECS > 0 )); then
+  sleep "${TTL_DECAY_WAIT_SECS}"
+  ttl_after_decay="$(redis_ttl "${hr_key}")"
+  expected_max="$((ttl_before_decay - TTL_DECAY_WAIT_SECS + 2))"
+  if [[ "${ttl_after_decay}" -gt "${expected_max}" ]]; then
+    echo "Expected TTL to decay after ${TTL_DECAY_WAIT_SECS}s (${ttl_before_decay} -> <=${expected_max}), got ${ttl_after_decay}"
+    exit 1
+  fi
+  echo "OK: TTL decayed (${ttl_before_decay}s -> ${ttl_after_decay}s over ${TTL_DECAY_WAIT_SECS}s wait)"
+fi
+
+recorded_hr2="$(date -u +"%Y-%m-%dT%H:%M:%SZ")"
+ingest_observation "${encounter_id}" "HEART_RATE" 96 "bpm" "DEVICE" "${recorded_hr2}" \
+  "sirs-hr2-${SCRIPT_RUN_ID}"
+if ! wait_for_observation_pipeline "${encounter_id}"; then
+  exit 1
+fi
+
+ttl_after_refresh="$(redis_ttl "${hr_key}")"
+if [[ "${ttl_after_refresh}" -lt 1500 || "${ttl_after_refresh}" -gt 1800 ]]; then
+  echo "Expected HEART_RATE TTL to reset near 1800 after re-qualifying observation, got ${ttl_after_refresh}"
+  exit 1
+fi
+echo "OK: TTL reset after qualifying HEART_RATE observation (TTL=${ttl_after_refresh}s)"
+
+echo ""
+echo "[7/${TOTAL_STEPS}] Verifying consumer group independence (sepsis-engine and es-indexer)"
+if ! wait_for_consumer_lag_zero "${SEPSIS_CONSUMER_GROUP}"; then
+  exit 1
+fi
+if ! wait_for_consumer_lag_zero "${ES_CONSUMER_GROUP}"; then
+  exit 1
+fi
+echo "OK: sepsis-engine and es-indexer both have LAG=0 on observation.recorded"
+
+echo ""
+echo "[8/${TOTAL_STEPS}] Verifying SEPSIS_WARNING in Elasticsearch and openAlertCount=2"
+elapsed=0
+while (( elapsed < INDEX_WAIT_SECS )); do
+  es_hits="$(curl -sS "${ES_URL}/clinical_alerts/_search" \
+    -H "Content-Type: application/json" \
+    -d "{\"query\":{\"bool\":{\"must\":[{\"term\":{\"encounterId\":\"${encounter_id}\"}},{\"term\":{\"alertType\":\"SEPSIS_WARNING\"}}]}}}" \
+    | jq -r '.hits.total.value')"
+  if [[ "${es_hits}" == "1" ]]; then
+    break
+  fi
+  sleep 2
+  elapsed=$((elapsed + 2))
+done
+
+if [[ "${es_hits:-0}" != "1" ]]; then
+  echo "Expected 1 SEPSIS_WARNING document in clinical_alerts for encounter ${encounter_id}, got ${es_hits:-0}"
+  exit 1
+fi
+
+es_alert="$(curl -sS "${ES_URL}/clinical_alerts/_search" \
+  -H "Content-Type: application/json" \
+  -d "{\"query\":{\"bool\":{\"must\":[{\"term\":{\"encounterId\":\"${encounter_id}\"}},{\"term\":{\"alertType\":\"SEPSIS_WARNING\"}}]}}}" \
+  | jq -r '.hits.hits[0]._source | [.severity, .status] | @tsv')"
+if [[ "${es_alert}" != $'Critical\tOpen' ]]; then
+  echo "Expected Elasticsearch alert severity=Critical status=Open, got '${es_alert}'"
+  exit 1
+fi
+
+open_alert_count="$(curl -sS "${ES_URL}/patient_encounters/_source/${encounter_id}" | jq -r '.openAlertCount')"
+if [[ "${open_alert_count}" != "2" ]]; then
+  echo "Expected openAlertCount=2 (potassium + sepsis), got ${open_alert_count}"
+  exit 1
+fi
+echo "OK: SEPSIS_WARNING indexed (Critical/Open) and openAlertCount=2"
+
+echo ""
+echo "[9/${TOTAL_STEPS}] Verifying criterion clears immediately but alert remains open"
+ingest_observation "${encounter_id}" "TEMP_C" 38.5 "°C" "DEVICE" "$(date -u +"%Y-%m-%dT%H:%M:%SZ")" \
+  "sirs-temp-qual-${SCRIPT_RUN_ID}"
+if ! wait_for_observation_pipeline "${encounter_id}"; then
+  exit 1
+fi
+
+temp_key="$(sirs_key "${encounter_id}" "TEMP_C")"
+if [[ "$(redis_get "${temp_key}")" != "1" ]]; then
+  echo "Expected qualifying temperature to set ${temp_key}"
+  exit 1
+fi
+
+ingest_observation "${encounter_id}" "TEMP_C" 37.0 "°C" "DEVICE" "$(date -u +"%Y-%m-%dT%H:%M:%SZ")" \
+  "sirs-temp-normal-${SCRIPT_RUN_ID}"
+if ! wait_for_observation_pipeline "${encounter_id}"; then
+  exit 1
+fi
+
+temp_value="$(redis_get "${temp_key}")"
+if [[ -n "${temp_value}" ]]; then
+  echo "Expected ${temp_key} to be cleared after normal temperature, got '${temp_value}'"
+  exit 1
+fi
+
+alert_status="$(psql_cmd "SELECT status FROM clinical_alerts WHERE encounter_id = '${encounter_id}' AND alert_type = 'SEPSIS_WARNING' LIMIT 1")"
+if [[ "${alert_status}" != "OPEN" ]]; then
+  echo "Expected SEPSIS_WARNING to remain OPEN after criterion cleared, got '${alert_status}'"
+  exit 1
+fi
+echo "OK: TEMP_C key deleted on normalisation; SEPSIS_WARNING remains OPEN"
+
+echo ""
+echo "[10/${TOTAL_STEPS}] Verifying non-SIRS observation is ignored by the sepsis engine"
+ingest_observation "${encounter_id}" "POTASSIUM_MEQ_L" 3.2 "mEq/L" "LAB" "$(date -u +"%Y-%m-%dT%H:%M:%SZ")" \
+  "sirs-non-sirs-${SCRIPT_RUN_ID}"
+if ! wait_for_observation_pipeline "${encounter_id}"; then
+  exit 1
+fi
+
+pot_key="$(sirs_key "${encounter_id}" "POTASSIUM_MEQ_L")"
+if redis_cmd EXISTS "${pot_key}" | grep -q '^1'; then
+  echo "Non-SIRS code must not create a Redis SIRS key (${pot_key})"
+  exit 1
+fi
+echo "OK: non-SIRS observation did not create SIRS Redis keys"
+
+echo ""
+echo "All ${TOTAL_STEPS} sepsis / SIRS checks passed."
+echo ""
+echo "Prerequisites: docker compose up -d && dotnet run --project VigilCareClinicalAPI"
+echo "Optional: set TTL_DECAY_WAIT_SECS=60 to match the full sliding-window decay check in the plan."