part #2

src/__Libraries/StellaOps.Worker.Health/HostStartedHealthCheck.cs

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+using Microsoft.Extensions.Diagnostics.HealthChecks;
+using Microsoft.Extensions.Hosting;
+
+namespace StellaOps.Worker.Health;
+
+/// <summary>
+/// Health check that reports healthy once the host has fully started.
+/// Before <see cref="IHostApplicationLifetime.ApplicationStarted"/> fires,
+/// this check returns <see cref="HealthStatus.Degraded"/> so readiness
+/// probes can distinguish startup from running state.
+/// </summary>
+internal sealed class HostStartedHealthCheck : IHealthCheck, IDisposable
+{
+    private volatile bool _started;
+    private CancellationTokenRegistration _registration;
+
+    public HostStartedHealthCheck(IHostApplicationLifetime lifetime)
+    {
+        _registration = lifetime.ApplicationStarted.Register(() => _started = true);
+    }
+
+    public Task<HealthCheckResult> CheckHealthAsync(
+        HealthCheckContext context,
+        CancellationToken cancellationToken = default)
+    {
+        return Task.FromResult(_started
+            ? HealthCheckResult.Healthy("Host started.")
+            : HealthCheckResult.Degraded("Host is starting."));
+    }
+
+    public void Dispose()
+    {
+        _registration.Dispose();
+    }
+}

src/__Libraries/StellaOps.Worker.Health/StellaOps.Worker.Health.csproj

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+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+    <TreatWarningsAsErrors>true</TreatWarningsAsErrors>
+    <LangVersion>preview</LangVersion>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <FrameworkReference Include="Microsoft.AspNetCore.App" />
+  </ItemGroup>
+</Project>

src/__Libraries/StellaOps.Worker.Health/WorkerHealthExtensions.cs

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+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Diagnostics.HealthChecks;
+using Microsoft.AspNetCore.Http;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Diagnostics.HealthChecks;
+
+namespace StellaOps.Worker.Health;
+
+/// <summary>
+/// Extension methods to add lightweight health endpoints to worker services.
+/// </summary>
+public static class WorkerHealthExtensions
+{
+    /// <summary>
+    /// Registers a health check that tracks whether the host has fully started.
+    /// Call this on <c>builder.Services</c> before building the application.
+    /// </summary>
+    public static IServiceCollection AddWorkerHealthChecks(this IServiceCollection services)
+    {
+        services.AddHealthChecks()
+            .AddCheck<HostStartedHealthCheck>("host_started", tags: ["ready"]);
+        return services;
+    }
+
+    /// <summary>
+    /// Maps <c>/health/liveness</c> (always 200) and <c>/health/readiness</c>
+    /// (checks registered health checks) endpoints.
+    /// </summary>
+    public static WebApplication MapWorkerHealthEndpoints(this WebApplication app)
+    {
+        // Liveness: always returns 200 if the process is running
+        app.MapGet("/health/liveness", () => Results.Ok("Alive"))
+            .ExcludeFromDescription();
+
+        // Readiness: runs all registered health checks tagged "ready"
+        app.MapHealthChecks("/health/readiness", new HealthCheckOptions
+        {
+            Predicate = check => check.Tags.Contains("ready"),
+            ResultStatusCodes =
+            {
+                [HealthStatus.Healthy] = StatusCodes.Status200OK,
+                [HealthStatus.Degraded] = StatusCodes.Status503ServiceUnavailable,
+                [HealthStatus.Unhealthy] = StatusCodes.Status503ServiceUnavailable,
+            },
+        });
+
+        return app;
+    }
+}