First-time setup: the first login made while no administrator exists becomes it

Sign-up stays closed (invitations only), so a new server's first login could only be made over SSH with admin
create-root, and an invitation needs a group, which needs a login. While no administrator exists, GET
/clientapi/user/setup says so and POST takes a SetupForm (login, password, first persona): the login is made the
administrator with its persona, and setup closes for good (owner decision 2026-10-16: first come, first served, no setup
code).

ServerSetup is one document with a fixed id, so the first request to insert it wins and two setups at once make one
administrator. A setup that fails before its login is made gives the claim back; one that named an administrator never
does, whoever is demoted or deleted later, and the CLI stays the way back. admin promote and create-root --admin seal it
too, migration _018 seals a server that already had an administrator, and no backup holds it nor does a restore drop it,
since a restore tombstones an administrator made after the backup. Public sign-up, NodeInfo and the instance API are
unchanged. RootUser.SetAdmin is the one place an administrator is made (with isModerator, which IsAdminPolicy asks for),
and the invitation endpoints share InsertPersona with setup.

Tests: ServerSetupTests on the invitations-only host (setup, the race, failed setups, sign-up still closed, the CLI's
seal) and the migration; the whole suite passes (962). In the pasture, decePub's setup and invitation pages pass end to
end.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -150,9 +150,20 @@ curl-able. Outbound fetches only go to https DNS names resolving to public addre
 `Federation__AllowPrivateNetworks=true`, `Federation__AllowPlainHttp=true` and `Federation__AcceptAnyCertificate=true`,
 which startup refuses in Production.
 
+Sign-up is closed in production (invitations only). The server's first login is made from the client instead, while no
+administrator exists (owner decision 2026-10-16, first come, first served):
+- `GET /clientapi/user/setup` says whether setup waits (`ViewServerSetup.IsPending`), and `POST` takes a `SetupForm`
+  (login, password, first persona). That login is made the administrator, with its persona.
+- `ServerSetup` (`Models/ServerSetup.cs`) closes setup for good: one document with the fixed id `setup`. The first request
+  to insert it wins, so two setups at once make one administrator.
+  - It is never given back once it names an administrator, whoever is demoted or deleted later.
+  - `admin promote` and `create-root --admin` seal it too, and migration `_018` seals a server that already had an
+    administrator.
+  - It is never in a backup and never dropped by a restore.
+
 The admin CLI runs with every service built but nothing started (no Kestrel, no hosted services), so it can run next to
-the live service. Sign-up is closed in production (invitations only), so the first login is made here; promoting is how
-an admin is made (signing up as "admin" grants nothing):
+the live service. It is the way back when setup is closed and no administrator can sign in; promoting is how an admin is
+made (signing up as "admin" grants nothing):
 
 ```bash
 cd /var/www/privapub.thepra.dev
@@ -503,8 +514,9 @@ group www-data and reaches the private mongod; `sudo -u www-data` works too.
     backup rotates out), copies where a link can't be made. `--db-only` lists them instead.
 
   **Never in a backup** (`ServerBackup.Excluded`): `InteractionSalt` (owner rule), `Job` and `Delivery` (work in flight),
-  `EmailRecovery`, `openiddict.tokens` and `.authorizations` (sessions), `MaintenanceLock`, and `AppConfiguration`
-  (its SMTP password; it is made again from appsettings at boot). One backup or restore runs at a time
+  `EmailRecovery`, `openiddict.tokens` and `.authorizations` (sessions), `MaintenanceLock`, `ServerSetup` (a restore
+  never opens setup again), and `AppConfiguration` (its SMTP password; it is made again from appsettings at boot). One
+  backup or restore runs at a time
   (`MaintenanceLock`, a heartbeat document; a holder silent for 2 minutes is taken over), and the media janitor purges
   nothing meanwhile. `BackupScheduler` backs up at `Backups:NightlyAt` (03:30 UTC), or at once when it missed the night;
   rotation keeps 7 daily and 4 weekly nightly backups, 3 pre-deploy, 3 pre-restore, and manual and uploaded ones until

PrivaPub.ClientModels/SetupForm.cs

@@ -0,0 +1,18 @@
+using PrivaPub.ClientModels.Resources;
+
+using System.ComponentModel.DataAnnotations;
+
+namespace PrivaPub.ClientModels
+{
+	// The server's first login, made while it has no administrator (/clientapi/user/setup), with its first persona.
+	public class SetupForm : LoginForm
+	{
+		[Required(ErrorMessageResourceName = "Required", ErrorMessageResourceType = typeof(ErrorsResource)),
+			StringLength(32, MinimumLength = 3, ErrorMessageResourceName = "StringLengthMinMax", ErrorMessageResourceType = typeof(ErrorsResource)),
+			RegularExpression(Constants.UserNameRegex, ErrorMessageResourceName = "InvalidUserName", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string AvatarUserName { get; set; }
+
+		[StringLength(64, ErrorMessageResourceName = "MaxLengthString", ErrorMessageResourceType = typeof(ErrorsResource))]
+		public string AvatarName { get; set; }
+	}
+}

PrivaPub.ClientModels/User/ViewServerSetup.cs

@@ -0,0 +1,8 @@
+namespace PrivaPub.ClientModels.User
+{
+	public class ViewServerSetup
+	{
+		// no administrator yet: the first login made through /clientapi/user/setup becomes it
+		public bool IsPending { get; set; } = false;
+	}
+}

PrivaPub.Tests/Http/ServerSetupTests.cs

@@ -0,0 +1,156 @@
+using Microsoft.AspNetCore.Hosting;
+using Microsoft.AspNetCore.Mvc.Testing;
+
+using MongoDB.Entities;
+
+using PrivaPub.ClientModels;
+using PrivaPub.Infrastructure;
+using PrivaPub.Infrastructure.Cli;
+using PrivaPub.Models;
+using PrivaPub.Tests.Support;
+using PrivaPub.Tests.Support.Host;
+
+using System.Net;
+using System.Net.Http.Headers;
+
+namespace PrivaPub.Tests.Http
+{
+	// Setup is server-wide, so each test opens it again by removing the seal, and seals it once done.
+	[Xunit.Collection(nameof(Exclusive))]
+	[Trait("Category", "Integration")]
+	public sealed class ServerSetupTests : IAsyncLifetime
+	{
+		PrivaPubHost _host;
+		WebApplicationFactory<Program> _closed;
+
+		public async ValueTask InitializeAsync()
+		{
+			Assert.SkipUnless(MongoFixture.Enabled, MongoFixture.Skip);
+			_host = await PrivaPubHost.Shared();
+			// production's mode: sign-up closed, invitations only
+			_closed = _host.WithWebHostBuilder(builder => builder.UseSetting("Registrations:Mode", nameof(RegistrationMode.Invitations)));
+			await DB.Default.DeleteAsync<ServerSetup>(ServerSetup.Name);
+		}
+
+		public async ValueTask DisposeAsync()
+		{
+			if (_closed == default)
+				return;
+			await ServerSetup.Seal("tests", default);
+			await _closed.DisposeAsync();
+		}
+
+		HttpClient Client(string jwt = default)
+		{
+			var client = _closed.CreateClient(new WebApplicationFactoryClientOptions { BaseAddress = new Uri(PrivaPubHost.Base + "/"), AllowAutoRedirect = false });
+			client.DefaultRequestHeaders.Remove(PrivaPubHost.ClientHeader);
+			client.DefaultRequestHeaders.Add(PrivaPubHost.ClientHeader, $"10.{Random.Shared.Next(256)}.{Random.Shared.Next(256)}.{Random.Shared.Next(1, 255)}");
+			if (jwt != default)
+				client.DefaultRequestHeaders.Authorization = new AuthenticationHeaderValue("Bearer", jwt);
+			return client;
+		}
+
+		static string Name(string prefix) => $"{prefix}{Guid.NewGuid():N}"[..20];
+
+		static object Form(string userName, string avatarUserName, string avatarName = default) =>
+			new { userName, password = Accounts.Password, avatarUserName, avatarName };
+
+		async Task<bool> Pending()
+		{
+			using var client = Client();
+			return (await client.Get("/clientapi/user/setup")).Ok().Body.Flag("isPending");
+		}
+
+		static async Task<string> Message(HttpResponseMessage response)
+		{
+			var body = await response.JsonBody();
+			return body["errorMessage"]?.GetValue<string>() ?? body["title"]?.GetValue<string>();
+		}
+
+		[Fact]
+		public async Task Setup_makes_the_first_login_the_administrator_with_its_persona_and_closes()
+		{
+			var token = TestContext.Current.CancellationToken;
+			var userName = Name("first");
+			var avatarUserName = Name("founder");
+			Assert.True(await Pending());
+			using var client = Client();
+
+			var response = await client.PostJson("/clientapi/user/setup", Form(userName, avatarUserName, "The Founder"));
+
+			Assert.Equal(HttpStatusCode.OK, response.StatusCode);
+			var jwt = await response.JsonBody();
+			var policies = jwt["policies"]!.AsArray().Select(p => p!.GetValue<string>()).Order();
+			Assert.Equal(new[] { Policies.IsAdmin, Policies.IsModerator, Policies.IsUser }.Order(), policies);
+			using var admin = Client(jwt["token"]!.GetValue<string>());
+			Assert.Equal(HttpStatusCode.OK, (await admin.GetAsync("/clientapi/admin/domainblocks/list", token)).StatusCode);
+			var persona = Assert.Single(await (await admin.GetAsync("/clientapi/avatar/private/list", token)).JsonItems())!;
+			Assert.Equal(avatarUserName, persona["userName"]!.GetValue<string>());
+			Assert.Equal("The Founder", persona["name"]!.GetValue<string>());
+			var seal = await DB.Default.Find<ServerSetup>().OneAsync(ServerSetup.Name, token);
+			Assert.Equal(jwt["userId"]!.GetValue<string>(), seal.AdminId);
+
+			Assert.False(await Pending());
+			var again = await client.PostJson("/clientapi/user/setup", Form(Name("second"), Name("latecomer")));
+			Assert.Equal(HttpStatusCode.Forbidden, again.StatusCode);
+			Assert.Contains("already set up", await Message(again));
+		}
+
+		[Fact]
+		public async Task Two_setups_at_once_make_one_administrator()
+		{
+			using var first = Client();
+			using var second = Client();
+
+			var answers = await Task.WhenAll(
+				first.PostJson("/clientapi/user/setup", Form(Name("racea"), Name("racera"))),
+				second.PostJson("/clientapi/user/setup", Form(Name("raceb"), Name("racerb"))));
+
+			Assert.Equal(new[] { HttpStatusCode.OK, HttpStatusCode.Forbidden }, answers.Select(a => a.StatusCode).Order());
+			Assert.False(await Pending());
+		}
+
+		[Fact]
+		public async Task A_setup_that_fails_leaves_the_server_to_set_up()
+		{
+			var taken = await _host.SignUp("taken");
+			var userName = Name("same");
+			using var client = Client();
+
+			var samePersona = await client.PostJson("/clientapi/user/setup", Form(userName, userName));
+			var noPersona = await client.PostJson("/clientapi/user/setup", new { userName = Name("bare"), password = Accounts.Password });
+			var takenLogin = await client.PostJson("/clientapi/user/setup", Form(taken.UserName, Name("takenp")));
+
+			Assert.Equal(HttpStatusCode.BadRequest, samePersona.StatusCode);
+			Assert.Contains("must differ", await Message(samePersona));
+			Assert.Equal(HttpStatusCode.BadRequest, noPersona.StatusCode);
+			Assert.Equal(HttpStatusCode.BadRequest, takenLogin.StatusCode);
+			Assert.Contains("already taken", await Message(takenLogin));
+			Assert.True(await Pending());
+		}
+
+		[Fact]
+		public async Task While_setup_waits_sign_up_stays_closed()
+		{
+			using var client = Client();
+
+			var signUp = await client.PostJson("/clientapi/user/signup", new { userName = Name("outsider"), password = Accounts.Password });
+
+			Assert.Equal(HttpStatusCode.Forbidden, signUp.StatusCode);
+			Assert.True(await Pending());
+			Assert.False((await client.Get("/nodeinfo/2.1")).Ok().Body.Flag("openRegistrations"));
+		}
+
+		[Fact]
+		public async Task Promoting_an_administrator_with_the_cli_closes_setup()
+		{
+			var root = await _host.SignUp("promoted");
+			Assert.True(await Pending());
+
+			Assert.Equal(0, await AdminCommands.Run(new[] { "promote", root.UserName }, _host.Services));
+
+			Assert.False(await Pending());
+			Assert.Equal(root.Id, (await DB.Default.Find<ServerSetup>().OneAsync(ServerSetup.Name, TestContext.Current.CancellationToken)).AdminId);
+		}
+	}
+}

PrivaPub.Tests/Infrastructure/MigrationTests.cs

@@ -246,5 +246,21 @@ namespace PrivaPub.Tests.Infrastructure
 			}
 			Assert.Equal(new DateTime(2026, 6, 10, 0, 0, 0, DateTimeKind.Utc), (await DB.Default.Find<Avatar>().OneAsync(dated.ID, token)).PublishedOn);
 		}
+
+		[Fact]
+		public async Task A_server_with_an_administrator_is_set_up()
+		{
+			Assert.SkipUnless(MongoFixture.Enabled, MongoFixture.Skip);
+			var token = TestContext.Current.CancellationToken;
+			await DB.Default.DeleteAsync<PrivaPub.Models.ServerSetup>(PrivaPub.Models.ServerSetup.Name);
+			var admin = new RootUser { UserName = $"admin{Guid.NewGuid():N}"[..20] };
+			admin.SetAdmin(true);
+			await DB.Default.SaveAsync(admin, token);
+			Assert.True(await PrivaPub.Models.ServerSetup.IsPending(token));
+
+			await new _018_a_server_with_an_administrator_is_set_up().UpgradeAsync();
+
+			Assert.False(await PrivaPub.Models.ServerSetup.IsPending(token));
+		}
 	}
 }

PrivaPub/Controllers/ClientToServer/RootUserController.cs

@@ -5,6 +5,8 @@ using Microsoft.AspNetCore.RateLimiting;
 using Microsoft.Extensions.Localization;
 using Microsoft.Extensions.Options;
 
+using MongoDB.Entities;
+
 using PrivaPub.ClientModels;
 using PrivaPub.ClientModels.Resources;
 using PrivaPub.ClientModels.Group;
@@ -135,13 +137,7 @@ namespace PrivaPub.Controllers.ClientToServer
 					return StatusCode(result.StatusCode, result);
 				var (user, userSettings) = ((RootUser, ViewUserSettings))result.Data;
 
-				var avatar = await AvatarUsersService.InsertAvatar(new InsertAvatarForm
-				{
-					RootId = user.ID,
-					Name = string.IsNullOrWhiteSpace(signUpForm.AvatarName) ? avatarUserName : signUpForm.AvatarName.Trim(),
-					UserName = avatarUserName,
-					Biography = string.Empty
-				});
+				var avatar = await InsertPersona(user.ID, avatarUserName, signUpForm.AvatarName);
 				if (!avatar.IsValid)
 					return StatusCode(avatar.StatusCode, avatar);
 
@@ -190,13 +186,7 @@ namespace PrivaPub.Controllers.ClientToServer
 					var personaProblem = await PersonaProblem(avatarUserName, user.UserName, token);
 					if (personaProblem != default)
 						return BadRequest(new WebResult().Invalidate(personaProblem));
-					var inserted = await AvatarUsersService.InsertAvatar(new InsertAvatarForm
-					{
-						RootId = user.ID,
-						Name = string.IsNullOrWhiteSpace(loginForm.AvatarName) ? avatarUserName : loginForm.AvatarName.Trim(),
-						UserName = avatarUserName,
-						Biography = string.Empty
-					});
+					var inserted = await InsertPersona(user.ID, avatarUserName, loginForm.AvatarName);
 					if (!inserted.IsValid)
 						return StatusCode(inserted.StatusCode, inserted);
 					avatar = (ViewAvatar)inserted.Data;
@@ -220,6 +210,77 @@ namespace PrivaPub.Controllers.ClientToServer
 			}
 		}
 
+		[HttpGet, Route("/clientapi/user/setup"), AllowAnonymous]
+		public async Task<IActionResult> Setup(CancellationToken token) =>
+			Ok(new ViewServerSetup { IsPending = await ServerSetup.IsPending(token) });
+
+		// The server's first login, made while it has no administrator (owner decision 2026-10-16: first come, first served):
+		// it is made the administrator, with its first persona, and setup closes for good. Sign-up stays closed to everyone
+		// else (Registrations), so NodeInfo and the instance API don't change.
+		[HttpPost, Route("/clientapi/user/setup"), EnableRateLimiting(RateLimiting.Accounts), AllowAnonymous]
+		public async Task<IActionResult> SetUp(SetupForm setupForm, CancellationToken token)
+		{
+			if (User.Identity?.IsAuthenticated ?? false) return Redirect("/");
+			var result = new WebResult();
+			if (!ModelState.IsValid)
+				return BadRequest(result.Invalidate(Localizer["Invalid model."]));
+			var claimed = false;
+			var adminId = default(string);
+			try
+			{
+				if (!await ServerSetup.IsPending(token))
+					return SetUpAlready();
+
+				var avatarUserName = setupForm.AvatarUserName?.Trim().ToLowerInvariant();
+				var personaProblem = await PersonaProblem(avatarUserName, setupForm.UserName, token);
+				if (personaProblem != default)
+					return BadRequest(result.Invalidate(personaProblem));
+
+				claimed = await ServerSetup.Claim(token);
+				if (!claimed)
+					return SetUpAlready();
+
+				result = await UsersService.SignUpAsync(setupForm);
+				if (!result.IsValid)
+				{
+					await ServerSetup.Release();
+					return StatusCode(result.StatusCode, result);
+				}
+				var (user, userSettings) = ((RootUser, ViewUserSettings))result.Data;
+				user.SetAdmin(true);
+				await DB.Default.SaveAsync(user, CancellationToken.None);
+				adminId = user.ID;
+				await ServerSetup.Claimed(adminId, CancellationToken.None);
+
+				// set up from here, whatever happens to the persona: it can be made in the client's settings
+				var avatar = await InsertPersona(user.ID, avatarUserName, setupForm.AvatarName);
+				if (!avatar.IsValid)
+					return StatusCode(avatar.StatusCode, avatar);
+
+				return Ok(AuthTokenManager.GenerateToken(user, userSettings));
+			}
+			catch (Exception ex)
+			{
+				Logger.LogError(ex, $"{nameof(User)}.{nameof(SetUp)}()");
+				if (claimed && adminId == default)
+					await ServerSetup.Release();
+				return BadRequest(result.Invalidate(Localizer["Something went wrong."]));
+			}
+		}
+
+		IActionResult SetUpAlready() =>
+			StatusCode(StatusCodes.Status403Forbidden,
+				new WebResult().Invalidate(Localizer["This server is already set up: joining it takes a group invitation."], StatusCodes.Status403Forbidden));
+
+		Task<WebResult> InsertPersona(string rootId, string avatarUserName, string avatarName) =>
+			AvatarUsersService.InsertAvatar(new InsertAvatarForm
+			{
+				RootId = rootId,
+				Name = string.IsNullOrWhiteSpace(avatarName) ? avatarUserName : avatarName.Trim(),
+				UserName = avatarUserName,
+				Biography = string.Empty
+			});
+
 		async Task<string> PersonaProblem(string avatarUserName, string rootUserName, CancellationToken token)
 		{
 			if (string.IsNullOrEmpty(avatarUserName))

PrivaPub/Infrastructure/Backup/ServerBackup.cs

@@ -40,7 +40,8 @@ namespace PrivaPub.Infrastructure.Backup
 			[nameof(MaintenanceLock)] = "who is backing up or restoring now",
 			["AppConfiguration"] = "the configuration's copy holds the SMTP password, and is made again from appsettings at boot",
 			[nameof(RestoreRecord)] = "what restores did outlives what they restore",
-			["PersonaArchive"] = "personas' archives being made or imported belong to the moment"
+			["PersonaArchive"] = "personas' archives being made or imported belong to the moment",
+			["ServerSetup"] = "the server is set up once: a restore never opens its setup again"
 		};
 
 		static readonly JsonWriterSettings Json = new() { OutputMode = JsonOutputMode.CanonicalExtendedJson, Indent = false };

PrivaPub/Infrastructure/Cli/AdminCommands.cs

@@ -4,6 +4,7 @@ using PrivaPub.ClientModels;
 using PrivaPub.ClientModels.User;
 using PrivaPub.ClientModels.User.Avatar;
 using PrivaPub.Infrastructure.Backup;
+using PrivaPub.Models;
 using PrivaPub.Models.User;
 using PrivaPub.Services;
 using PrivaPub.Services.ClientToServer.Private;
@@ -194,19 +195,17 @@ namespace PrivaPub.Infrastructure.Cli
 				return 1;
 			}
 
-			user.Policies.RemoveAll(p => p is Policies.IsAdmin or Policies.IsModerator);
-			if (promote)
-				user.Policies.AddRange(new[] { Policies.IsAdmin, Policies.IsModerator });
-			if (!user.Policies.Contains(Policies.IsUser))
-				user.Policies.Add(Policies.IsUser);
-			user.UpdatedAt = DateTime.UtcNow;
+			user.SetAdmin(promote);
 			await DB.Default.SaveAsync(user);
+			if (promote)
+				await ServerSetup.Seal(user.ID, default);//an administrator exists: the client's setup is closed
 
 			output.WriteLine($"{userName}: {string.Join(", ", user.Policies)}");
 			return 0;
 		}
 
-		// With sign-up closed this is how the first root is made; group invitations make the rest.
+		// With sign-up closed, this or the client's setup (while no administrator exists) makes the first root; group invitations
+		// make the rest.
 		static async Task<int> CreateRoot(IServiceProvider services, string login, string password, bool admin, TextWriter output)
 		{
 			var form = new LoginForm { UserName = login, Password = password?.Trim() };

PrivaPub/Infrastructure/Data/Migrations/_018_a_server_with_an_administrator_is_set_up.cs

@@ -0,0 +1,23 @@
+using MongoDB.Entities;
+
+using PrivaPub.ClientModels;
+using PrivaPub.Models;
+using PrivaPub.Models.User;
+
+namespace PrivaPub.Infrastructure.Data.Migrations
+{
+	// the client's setup is open only while no administrator exists (ServerSetup): a server that already has one, made with
+	// the CLI before setup existed, is set up
+	public class _018_a_server_with_an_administrator_is_set_up : IMigration
+	{
+		public async Task UpgradeAsync()
+		{
+			var admin = await DB.Default.Find<RootUser>()
+				.Match(u => u.Policies.Contains(Policies.IsAdmin))
+				.Sort(u => u.CreatedAt, Order.Ascending)
+				.ExecuteFirstAsync();
+			if (admin != default)
+				await ServerSetup.Seal(admin.ID, default);
+		}
+	}
+}

PrivaPub/Models/ServerSetup.cs

@@ -0,0 +1,64 @@
+using MongoDB.Driver;
+using MongoDB.Entities;
+
+namespace PrivaPub.Models
+{
+	// The server's first-time setup (owner decision 2026-10-16): while no administrator exists, the client's setup page makes
+	// the first login, which becomes the administrator; this document then closes setup for good, whoever is demoted or
+	// deleted later (the CLI stays the way back). The first request to insert it wins, so two setups at once make one
+	// administrator. A backup never holds it and a restore never drops it (ServerBackup.Excluded): a restore tombstones an
+	// administrator made after the backup, and setup would otherwise be open to whoever came first.
+	public class ServerSetup : Entity
+	{
+		public const string Name = "setup";
+
+		public string AdminId { get; set; }//null while the claiming request is still making its login
+		public DateTime SealedAt { get; set; }
+
+		public static async Task<bool> IsPending(CancellationToken token) =>
+			!await DB.Default.Find<ServerSetup>().Match(s => s.ID == Name).ExecuteAnyAsync(token);
+
+		/// <summary>Takes the setup for one request: false when it is done, or another request took it first.</summary>
+		public static async Task<bool> Claim(CancellationToken token)
+		{
+			try
+			{
+				await DB.Default.InsertAsync(new ServerSetup { ID = Name, SealedAt = DateTime.UtcNow }, token);
+				return true;
+			}
+			catch (MongoWriteException ex) when (ex.WriteError?.Category == ServerErrorCategory.DuplicateKey)
+			{
+				return false;
+			}
+		}
+
+		/// <summary>Names the administrator the claiming request made.</summary>
+		public static Task Claimed(string adminId, CancellationToken token) =>
+			DB.Default.Update<ServerSetup>().Match(s => s.ID == Name && s.AdminId == null).Modify(s => s.AdminId, adminId).ExecuteAsync(token);
+
+		/// <summary>Gives a claim back when its login couldn't be made; a named administrator is never given back.</summary>
+		public static Task Release() =>
+			DB.Default.DeleteAsync<ServerSetup>(s => s.ID == Name && s.AdminId == null);//a delete takes no token outside a transaction
+
+		/// <summary>Closes setup for an administrator made elsewhere (the CLI, a server that had one already).</summary>
+		public static async Task Seal(string adminId, CancellationToken token)
+		{
+			try
+			{
+				await DB.Default.Update<ServerSetup>().Match(s => s.ID == Name)
+					.Modify(b => b.SetOnInsert(s => s.AdminId, adminId))
+					.Modify(b => b.SetOnInsert(s => s.SealedAt, DateTime.UtcNow))
+					.Option(o => o.IsUpsert = true)
+					.ExecuteAsync(token);
+			}
+			catch (MongoCommandException ex) when (ex.Code == 11000)
+			{
+				//sealed meanwhile
+			}
+			catch (MongoWriteException ex) when (ex.WriteError?.Category == ServerErrorCategory.DuplicateKey)
+			{
+				//sealed meanwhile
+			}
+		}
+	}
+}

PrivaPub/Models/User/RootUser.cs

@@ -25,6 +25,17 @@ namespace PrivaPub.Models.User
 		public DateTime? DeletedAt { get; set; }
 		public DateTime? CredentialsChangedAt { get; set; }//when RootSessions last ended every session
 		public string SessionStamp { get; set; }//carried by every /clientapi token; a new one ends the tokens issued before
+
+		/// <summary>An administrator is a moderator too (IsAdminPolicy asks for both); otherwise a plain user.</summary>
+		public void SetAdmin(bool admin)
+		{
+			Policies.RemoveAll(p => p is ClientModels.Policies.IsAdmin or ClientModels.Policies.IsModerator);
+			if (admin)
+				Policies.AddRange([ClientModels.Policies.IsAdmin, ClientModels.Policies.IsModerator]);
+			if (!Policies.Contains(ClientModels.Policies.IsUser))
+				Policies.Add(ClientModels.Policies.IsUser);
+			UpdatedAt = DateTime.UtcNow;
+		}
 	}
 
 	public class ContactItem

docs/ROADMAP.md

@@ -247,7 +247,7 @@ and circles (see Owner decisions).
 | What runs in production | **Everything that is built is on and checked by the deploy**, and nothing waits on a person running a command. |
 | Geolocation | **The server fetches DB-IP Lite itself** (`GeoUpdater`): it checks daily, installs a new month's databases once they are published, refuses a file that does not open as the right kind of database, and keeps the old one when anything fails. No timer and no root step. The deploy fails if the databases are missing or more than 40 days old. |
 | Crawler | **On in production**, seeded with a handful of large servers of different kinds (`appsettings.Production.json`); the deploy fails if `/stargazing` does not say it is on. |
-| Sign-up | **Closed: invitations only.** A group invitation creates an account; open sign-up answers 403. NodeInfo, `/api/v1/instance` and `/api/v2/instance` read the same switch (`Registrations:Mode`), and the deploy fails if they disagree. The first login on a server is made with `PrivaPub admin create-root`. |
+| Sign-up | **Closed: invitations only.** A group invitation creates an account; open sign-up answers 403. NodeInfo, `/api/v1/instance` and `/api/v2/instance` read the same switch (`Registrations:Mode`), and the deploy fails if they disagree. The first login on a server is made from the client's setup page while no administrator exists (2026-10-16: first come, first served, no setup code); it becomes the administrator with its first persona, and setup closes for good (`ServerSetup`, kept across restores). `PrivaPub admin create-root` remains the way in from the box. |
 | Signed-in smoke check | **`@thepra`, undiscoverable, made and kept by the deploy**: `PrivaPub admin smoke thepra` creates or keeps the root `deploy-smoke` and the persona and gives the root a new password on every deploy; the deploy signs in through the real OAuth flow, checks the signed-in API and revokes its token. No secret is stored. |
 | Signed fetches (SecureMode) | **On in production** once the pasture passes with it on (Phase 2 of the 2026-10-04 plan). |
 | Circles on Mastodon and GoToSocial | **Each member's copy names that member** in `cc`; a member's refetch names the member, an instance actor's refetch the members on its server. Nothing new is revealed to anyone outside the circle. |