feat(stability): unify readiness and recovery

backend-tests/AuthServiceTests.cs

@@ -1,6 +1,7 @@
 using System.Reflection;
 using System.Security.Claims;
 using Microsoft.EntityFrameworkCore;
+using Microsoft.EntityFrameworkCore.Storage;
 using Microsoft.Extensions.Primitives;
 using Nexus.Api.Data;
 using Nexus.Api.DTOs;
@@ -209,6 +210,47 @@ public sealed class AuthServiceTests
         Assert.Equal(originalHash, updated.PasswordHash);
     }
 
+    [Fact]
+    public async Task RefreshToken_SurvivesServiceRestart_WhenDatabasePersists()
+    {
+        var databaseRoot = new InMemoryDatabaseRoot();
+        var databaseName = Guid.NewGuid().ToString();
+        var configuration = new MemoryConfig(new Dictionary<string, string?>
+        {
+            ["Jwt:Key"] = "this-is-a-test-key-that-is-at-least-32-bytes-long!",
+            ["Jwt:Issuer"] = "nexus-test",
+            ["Jwt:Audience"] = "nexus-test-web",
+        });
+        var logger = Microsoft.Extensions.Logging.Abstractions.NullLogger<AuthService>.Instance;
+
+        AuthSession initialSession;
+        await using (var firstDb = new NexusDbContext(
+                         new DbContextOptionsBuilder<NexusDbContext>()
+                             .UseInMemoryDatabase(databaseName, databaseRoot)
+                             .Options))
+        {
+            await SeedUserAsync(firstDb, "restart@example.com", "RestartPassword123!");
+            var firstService = new AuthService(new UserRepository(firstDb), configuration, logger);
+            initialSession = Assert.IsType<AuthSession>(
+                await firstService.LoginAsync(Login("restart@example.com", "RestartPassword123!")));
+        }
+
+        await using var restartedDb = new NexusDbContext(
+            new DbContextOptionsBuilder<NexusDbContext>()
+                .UseInMemoryDatabase(databaseName, databaseRoot)
+                .Options);
+        var restartedService = new AuthService(
+            new UserRepository(restartedDb),
+            configuration,
+            logger);
+
+        var refreshed = await restartedService.RefreshAsync(initialSession.RefreshToken);
+
+        Assert.NotNull(refreshed);
+        Assert.NotEqual(initialSession.RefreshToken, refreshed.RefreshToken);
+        Assert.Equal(initialSession.User.Id, refreshed.User.Id);
+    }
+
     // ══════════════════════════════════════════════════════════════════
     // Change Password Tests
     // ══════════════════════════════════════════════════════════════════