feat(arena-colosseum): lobby + constructed entry (phase 1)

Closes 5 of arena-colosseum's 16 spec shapes (1/16 → 6/16). Lobby reads
(/top, /get_fee_info, /event_info) render an empty "no event scheduled"
payload by default; /entry + /register_deck activate via admin-flipped
ColosseumSeason + ColosseumRounds config sections.

* Schema: ViewerArenaColosseumRun standalone table (unique on ViewerId)
  with jsonb run-state columns mirroring ViewerArenaTwoPickRun.
* Config sections: ColosseumSeasonConfig (event-level), ColosseumRoundsConfig
  (the 3-round bracket). Empty defaults — IsColosseumPeriod=false.
* Migration AddArenaColosseumRun (DDL only; seed rows come from the section
  ShippedDefaults via EnsureSeedDataAsync).
* DTOs: ColosseumLobbyInfo (round-level, /top + /get_fee_info), ColosseumEventInfo
  (event-level, /event_info), ColosseumOwnStatus (shared status block),
  ColosseumEntryRef, ColosseumFeeList, ColosseumUserDeck, ColosseumBattleResults,
  ColosseumRoundDetail + ColosseumGroupRow. EventInfoResponse uses explicit
  [JsonPropertyName("1"|"2"|"3")] for the string-keyed rounds shape per spec.
* Controller: ArenaColosseumController replaces the 1-action stub with
  the five lifecycle endpoints. /top emits leader_skin_id even when 0
  (project_wire_null_policy override).
* Tests: 11 controller-level tests + 6 config round-trip tests covering
  empty-season payloads, run-seeded /top round-trip, crystal/rupy entry
  debits, now_round_id mismatch rejection, deck_no_list round-trip + reject.

SVSim.Database/Migrations/20260613155613_AddArenaColosseumRun.cs

@@ -0,0 +1,69 @@
+using System;
+using Microsoft.EntityFrameworkCore.Migrations;
+using Npgsql.EntityFrameworkCore.PostgreSQL.Metadata;
+
+#nullable disable
+
+namespace SVSim.Database.Migrations
+{
+    /// <inheritdoc />
+    public partial class AddArenaColosseumRun : Migration
+    {
+        /// <inheritdoc />
+        protected override void Up(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.CreateTable(
+                name: "ViewerArenaColosseumRuns",
+                columns: table => new
+                {
+                    Id = table.Column<long>(type: "bigint", nullable: false)
+                        .Annotation("Npgsql:ValueGenerationStrategy", NpgsqlValueGenerationStrategy.IdentityByDefaultColumn),
+                    ViewerId = table.Column<long>(type: "bigint", nullable: false),
+                    EntryId = table.Column<long>(type: "bigint", nullable: false),
+                    SeasonId = table.Column<int>(type: "integer", nullable: false),
+                    RoundId = table.Column<int>(type: "integer", nullable: false),
+                    DeckFormat = table.Column<int>(type: "integer", nullable: false),
+                    LeaderSkinId = table.Column<long>(type: "bigint", nullable: false),
+                    ConsumeItemType = table.Column<int>(type: "integer", nullable: false),
+                    CandidateClassIdsJson = table.Column<string>(type: "jsonb", nullable: false),
+                    SelectTurn = table.Column<int>(type: "integer", nullable: false),
+                    IsSelectCompleted = table.Column<bool>(type: "boolean", nullable: false),
+                    SelectedCardIdsJson = table.Column<string>(type: "jsonb", nullable: false),
+                    PendingPickSetsJson = table.Column<string>(type: "jsonb", nullable: false),
+                    NextCandidateId = table.Column<long>(type: "bigint", nullable: false),
+                    ClassId = table.Column<int>(type: "integer", nullable: false),
+                    ChaosId = table.Column<int>(type: "integer", nullable: false),
+                    ResultListJson = table.Column<string>(type: "jsonb", nullable: false),
+                    WinCount = table.Column<int>(type: "integer", nullable: false),
+                    LossCount = table.Column<int>(type: "integer", nullable: false),
+                    BattleCountThisRound = table.Column<int>(type: "integer", nullable: false),
+                    MaxBattleCountThisRound = table.Column<int>(type: "integer", nullable: false),
+                    BreakthroughNumberThisRound = table.Column<int>(type: "integer", nullable: false),
+                    RestEntryNum = table.Column<int>(type: "integer", nullable: false),
+                    IsRankMatching = table.Column<bool>(type: "boolean", nullable: false),
+                    IsChampion = table.Column<bool>(type: "boolean", nullable: false),
+                    RegisteredDeckNoListJson = table.Column<string>(type: "jsonb", nullable: false),
+                    IsPublished = table.Column<bool>(type: "boolean", nullable: false),
+                    CreatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false),
+                    UpdatedAt = table.Column<DateTime>(type: "timestamp with time zone", nullable: false)
+                },
+                constraints: table =>
+                {
+                    table.PrimaryKey("PK_ViewerArenaColosseumRuns", x => x.Id);
+                });
+
+            migrationBuilder.CreateIndex(
+                name: "IX_ViewerArenaColosseumRuns_ViewerId",
+                table: "ViewerArenaColosseumRuns",
+                column: "ViewerId",
+                unique: true);
+        }
+
+        /// <inheritdoc />
+        protected override void Down(MigrationBuilder migrationBuilder)
+        {
+            migrationBuilder.DropTable(
+                name: "ViewerArenaColosseumRuns");
+        }
+    }
+}

SVSim.Database/Migrations/SVSimDbContextModelSnapshot.cs

@@ -2766,6 +2766,111 @@ namespace SVSim.Database.Migrations
                     b.ToTable("ViewerAcquireHistory");
                 });
 
+            modelBuilder.Entity("SVSim.Database.Models.ViewerArenaColosseumRun", b =>
+                {
+                    b.Property<long>("Id")
+                        .ValueGeneratedOnAdd()
+                        .HasColumnType("bigint");
+
+                    NpgsqlPropertyBuilderExtensions.UseIdentityByDefaultColumn(b.Property<long>("Id"));
+
+                    b.Property<int>("BattleCountThisRound")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("BreakthroughNumberThisRound")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("CandidateClassIdsJson")
+                        .IsRequired()
+                        .HasColumnType("jsonb");
+
+                    b.Property<int>("ChaosId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("ClassId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("ConsumeItemType")
+                        .HasColumnType("integer");
+
+                    b.Property<DateTime>("CreatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<int>("DeckFormat")
+                        .HasColumnType("integer");
+
+                    b.Property<long>("EntryId")
+                        .HasColumnType("bigint");
+
+                    b.Property<bool>("IsChampion")
+                        .HasColumnType("boolean");
+
+                    b.Property<bool>("IsPublished")
+                        .HasColumnType("boolean");
+
+                    b.Property<bool>("IsRankMatching")
+                        .HasColumnType("boolean");
+
+                    b.Property<bool>("IsSelectCompleted")
+                        .HasColumnType("boolean");
+
+                    b.Property<long>("LeaderSkinId")
+                        .HasColumnType("bigint");
+
+                    b.Property<int>("LossCount")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("MaxBattleCountThisRound")
+                        .HasColumnType("integer");
+
+                    b.Property<long>("NextCandidateId")
+                        .HasColumnType("bigint");
+
+                    b.Property<string>("PendingPickSetsJson")
+                        .IsRequired()
+                        .HasColumnType("jsonb");
+
+                    b.Property<string>("RegisteredDeckNoListJson")
+                        .IsRequired()
+                        .HasColumnType("jsonb");
+
+                    b.Property<int>("RestEntryNum")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("ResultListJson")
+                        .IsRequired()
+                        .HasColumnType("jsonb");
+
+                    b.Property<int>("RoundId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("SeasonId")
+                        .HasColumnType("integer");
+
+                    b.Property<int>("SelectTurn")
+                        .HasColumnType("integer");
+
+                    b.Property<string>("SelectedCardIdsJson")
+                        .IsRequired()
+                        .HasColumnType("jsonb");
+
+                    b.Property<DateTime>("UpdatedAt")
+                        .HasColumnType("timestamp with time zone");
+
+                    b.Property<long>("ViewerId")
+                        .HasColumnType("bigint");
+
+                    b.Property<int>("WinCount")
+                        .HasColumnType("integer");
+
+                    b.HasKey("Id");
+
+                    b.HasIndex("ViewerId")
+                        .IsUnique();
+
+                    b.ToTable("ViewerArenaColosseumRuns");
+                });
+
             modelBuilder.Entity("SVSim.Database.Models.ViewerArenaTwoPickRun", b =>
                 {
                     b.Property<long>("Id")

SVSim.Database/Models/Config/ColosseumRoundsConfig.cs

@@ -0,0 +1,47 @@
+namespace SVSim.Database.Models.Config;
+
+/// <summary>
+/// The 3-round bracket schedule for an active Colosseum season. Empty <see cref="Rounds"/>
+/// is the default shipped state — lobby <c>/event_info</c> renders a benign payload with
+/// no rounds active. Collection default is in <see cref="ShippedDefaults"/> per
+/// feedback_config_defaults (property-initializer collection defaults silently empty out
+/// under the tier merge).
+/// </summary>
+[ConfigSection("ColosseumRounds")]
+public class ColosseumRoundsConfig
+{
+    public List<RoundEntry> Rounds { get; set; } = new();
+
+    public static ColosseumRoundsConfig ShippedDefaults() => new()
+    {
+        Rounds = new(),
+    };
+
+    public class RoundEntry
+    {
+        /// <summary>1, 2, or 3 in the canonical 3-round schedule.</summary>
+        public int RoundId { get; set; }
+
+        public DateTime StartTime { get; set; }
+        public DateTime EndTime { get; set; }
+
+        /// <summary>Bracket groups within the round (e.g. distinct breakthrough thresholds
+        /// for late-joiners). The first entry is the canonical lookup used by
+        /// <c>ColosseumProgressionService</c> for the v1 single-bracket case.</summary>
+        public List<GroupEntry> Groups { get; set; } = new();
+    }
+
+    public class GroupEntry
+    {
+        public string Group { get; set; } = "";
+
+        /// <summary>Max battles a viewer can play in this round before bracket termination.</summary>
+        public int MaxBattleCount { get; set; }
+
+        /// <summary>Wins required to promote out of this round.</summary>
+        public int BreakthroughNumber { get; set; }
+
+        /// <summary>Total bracket entries allotted to this group.</summary>
+        public int EntryNumber { get; set; }
+    }
+}

SVSim.Database/Models/Config/ColosseumSeasonConfig.cs

@@ -0,0 +1,68 @@
+using SVSim.Database.Enums;
+
+namespace SVSim.Database.Models.Config;
+
+/// <summary>
+/// Event-level configuration for an active Arena Colosseum (Grand Prix) season. Default
+/// <see cref="ShippedDefaults"/> emits <c>IsColosseumPeriod = false</c> so the lobby read
+/// endpoints render an empty "no event scheduled" payload without crashing the client.
+/// Flipping the event on is an admin operation per
+/// <c>docs/operations/grand-prix-event-setup.md</c> — write a row to <c>GameConfigs</c>.
+/// </summary>
+[ConfigSection("ColosseumSeason")]
+public class ColosseumSeasonConfig
+{
+    /// <summary>Master gate. <c>false</c> = lobby reads render an empty info block and
+    /// entry rejects. The client (<c>Wizard/ColosseumEntryInfoTask.cs</c>) reads this and
+    /// skips parsing the rest of the colosseum_info object.</summary>
+    public bool IsColosseumPeriod { get; set; }
+
+    /// <summary>Stamped onto every <see cref="ViewerArenaColosseumRun"/> at entry time.</summary>
+    public int SeasonId { get; set; }
+
+    public string ColosseumName { get; set; } = "";
+
+    /// <summary>Bracket format. Stamped onto the run at entry time.</summary>
+    public Format DeckFormat { get; set; } = Format.Rotation;
+
+    /// <summary>Server stores bool; the wire shape is the STRING "0"/"1" per Wizard/ColosseumEntryInfoTask.cs's
+    /// <c>jsonData.ToString() == "1"</c> parse. The response DTO converts at serialization time.</summary>
+    public bool IsNormalTwoPick { get; set; }
+
+    /// <summary>Wire string used by the client as a theme/color code. Empty when not in special mode.</summary>
+    public string IsSpecialMode { get; set; } = "";
+
+    public string? AnnounceId { get; set; }
+
+    public DateTime EventStartTime { get; set; }
+    public DateTime EventEndTime { get; set; }
+
+    /// <summary>How many bracket entries get eliminated in the final round before champion-determination.</summary>
+    public int FinalRoundEliminateCount { get; set; }
+
+    public string CardPoolName { get; set; } = "";
+
+    /// <summary>Card-set ids used as the 2-Pick / Chaos draft pool override for this season.
+    /// Phase 3 reads this through <c>ArenaTwoPickCardPoolService</c> instead of
+    /// <c>ChallengeConfig.PoolCardSetIds</c>.</summary>
+    public List<int> PoolCardSetIds { get; set; } = new();
+
+    public int RupyCost { get; set; }
+    public int TicketCost { get; set; }
+    public int CrystalCost { get; set; }
+
+    public bool IsAllowedFreeEntry { get; set; }
+
+    public bool IsAllCardEnabled { get; set; }
+
+    /// <summary>Number of strategies offered per pick in 2-Pick Chaos mode.</summary>
+    public int StrategyPickNum { get; set; }
+
+    public DateTime SalesPeriodStart { get; set; }
+    public DateTime SalesPeriodEnd { get; set; }
+
+    public static ColosseumSeasonConfig ShippedDefaults() => new()
+    {
+        IsColosseumPeriod = false,
+    };
+}

SVSim.Database/Models/ViewerArenaColosseumRun.cs

@@ -0,0 +1,105 @@
+using System.ComponentModel.DataAnnotations.Schema;
+using Microsoft.EntityFrameworkCore;
+using SVSim.Database.Enums;
+
+namespace SVSim.Database.Models;
+
+/// <summary>
+/// One active Grand Prix (Arena Colosseum) bracket run per viewer. Mirrors
+/// <see cref="ViewerArenaTwoPickRun"/> in shape so the 2-Pick draft state machine can be
+/// lifted onto it in Phase 3 — the schema is the union of constructed-mode lifecycle
+/// (registered decks, bracket counts, rank-match promotion flag) and TK2-style draft
+/// state. Standalone (not a Viewer owned collection) per
+/// project_ef_nav_include_pitfall, with a unique index on ViewerId to enforce
+/// "one active run per viewer". Row is deleted on /finish or /retire.
+/// </summary>
+[Index(nameof(ViewerId), IsUnique = true)]
+public class ViewerArenaColosseumRun
+{
+    public long Id { get; set; }
+
+    public long ViewerId { get; set; }
+
+    /// <summary>Wire <c>entry_info.id</c>. Set to <see cref="Id"/> on insert.</summary>
+    public long EntryId { get; set; }
+
+    /// <summary>Stamped from <see cref="Config.ColosseumSeasonConfig.SeasonId"/> at entry time so
+    /// mid-run season-config edits don't shift the run's identity.</summary>
+    public int SeasonId { get; set; }
+
+    /// <summary>Current bracket round (1..3 in the canonical 3-round schedule). Indexes
+    /// <see cref="Config.ColosseumRoundsConfig.Rounds"/> at entry time, advances on bracket
+    /// promotion via <c>ColosseumProgressionService</c>.</summary>
+    public int RoundId { get; set; }
+
+    /// <summary>Format the bracket plays in (Rotation/Unlimited/TwoPick/HOF/WindFall/Avatar/...).
+    /// Stamped from season config at entry time.</summary>
+    public Format DeckFormat { get; set; }
+
+    public long LeaderSkinId { get; set; }
+
+    /// <summary>eARENA_PAY: 1 = ticket, 2 = crystal, 3 = rupy, 0 = free entry. Stamped at entry.</summary>
+    public int ConsumeItemType { get; set; }
+
+    // --- 2-Pick / Chaos draft state (lifted from ViewerArenaTwoPickRun for Phase 3) ---
+
+    [Column(TypeName = "jsonb")]
+    public string CandidateClassIdsJson { get; set; } = "[]";
+
+    /// <summary>Stored as 0 in constructed mode (no draft turn machinery).</summary>
+    public int SelectTurn { get; set; }
+
+    public bool IsSelectCompleted { get; set; }
+
+    [Column(TypeName = "jsonb")]
+    public string SelectedCardIdsJson { get; set; } = "[]";
+
+    [Column(TypeName = "jsonb")]
+    public string PendingPickSetsJson { get; set; } = "[]";
+
+    /// <summary>Monotonic counter for CandidatePair.Id; advances by 2 each draft turn.</summary>
+    public long NextCandidateId { get; set; } = 1;
+
+    /// <summary>Selected class for 2-Pick / Chaos modes; 0 in constructed mode.</summary>
+    public int ClassId { get; set; }
+
+    /// <summary>Optional Chaos sub-mode replay id. 0 when not in Chaos.</summary>
+    public int ChaosId { get; set; }
+
+    // --- Per-round bracket state ---
+
+    [Column(TypeName = "jsonb")]
+    public string ResultListJson { get; set; } = "[]";
+
+    public int WinCount { get; set; }
+    public int LossCount { get; set; }
+    public int BattleCountThisRound { get; set; }
+
+    /// <summary>Cap copied from the matching <c>ColosseumRoundsConfig.Rounds[RoundId-1].Groups[0]</c>
+    /// at entry — stamped so mid-run round-config edits don't shift the cap.</summary>
+    public int MaxBattleCountThisRound { get; set; }
+
+    /// <summary>Wins required to break through to the next round. Same stamping rule as
+    /// <see cref="MaxBattleCountThisRound"/>.</summary>
+    public int BreakthroughNumberThisRound { get; set; }
+
+    /// <summary>Remaining attempts in the current entry. Decremented per battle finish until
+    /// 0 or breakthrough.</summary>
+    public int RestEntryNum { get; set; }
+
+    /// <summary>Flipped exactly once when the node signals <c>matching_state == 3008</c>.
+    /// Subsequent battle URLs use the <c>colosseum_rank_battle/*</c> prefix.</summary>
+    public bool IsRankMatching { get; set; }
+
+    public bool IsChampion { get; set; }
+
+    // --- Registered deck slot (constructed mode) ---
+
+    [Column(TypeName = "jsonb")]
+    public string RegisteredDeckNoListJson { get; set; } = "[]";
+
+    public bool IsPublished { get; set; }
+
+    public DateTime CreatedAt { get; set; }
+    public DateTime UpdatedAt { get; set; }
+}

SVSim.Database/Repositories/Viewer/ArenaColosseumRunRepository.cs

@@ -0,0 +1,36 @@
+using Microsoft.EntityFrameworkCore;
+using SVSim.Database.Models;
+
+namespace SVSim.Database.Repositories.Viewer;
+
+public class ArenaColosseumRunRepository : IArenaColosseumRunRepository
+{
+    private readonly SVSimDbContext _db;
+    public ArenaColosseumRunRepository(SVSimDbContext db) => _db = db;
+
+    public Task<ViewerArenaColosseumRun?> GetByViewerIdAsync(long viewerId) =>
+        _db.ViewerArenaColosseumRuns.FirstOrDefaultAsync(r => r.ViewerId == viewerId);
+
+    public async Task UpsertAsync(ViewerArenaColosseumRun run)
+    {
+        run.UpdatedAt = DateTime.UtcNow;
+        if (run.Id == 0)
+        {
+            run.CreatedAt = DateTime.UtcNow;
+            _db.ViewerArenaColosseumRuns.Add(run);
+        }
+        else
+        {
+            _db.ViewerArenaColosseumRuns.Update(run);
+        }
+        await _db.SaveChangesAsync();
+    }
+
+    public async Task DeleteAsync(long viewerId)
+    {
+        var row = await _db.ViewerArenaColosseumRuns.FirstOrDefaultAsync(r => r.ViewerId == viewerId);
+        if (row is null) return;
+        _db.ViewerArenaColosseumRuns.Remove(row);
+        await _db.SaveChangesAsync();
+    }
+}

SVSim.Database/Repositories/Viewer/IArenaColosseumRunRepository.cs

@@ -0,0 +1,10 @@
+using SVSim.Database.Models;
+
+namespace SVSim.Database.Repositories.Viewer;
+
+public interface IArenaColosseumRunRepository
+{
+    Task<ViewerArenaColosseumRun?> GetByViewerIdAsync(long viewerId);
+    Task UpsertAsync(ViewerArenaColosseumRun run);
+    Task DeleteAsync(long viewerId);
+}

SVSim.Database/SVSimDbContext.cs

@@ -107,6 +107,7 @@ public class SVSimDbContext : DbContext
 
     public DbSet<ArenaTwoPickReward> ArenaTwoPickRewards { get; set; } = null!;
     public DbSet<ViewerArenaTwoPickRun> ViewerArenaTwoPickRuns { get; set; } = null!;
+    public DbSet<ViewerArenaColosseumRun> ViewerArenaColosseumRuns { get; set; } = null!;
 
     public DbSet<SerialCodeEntry> SerialCodes => Set<SerialCodeEntry>();
     public DbSet<SerialCodeRewardEntry> SerialCodeRewards => Set<SerialCodeRewardEntry>();

SVSim.EmulatedEntrypoint/Controllers/ArenaColosseumController.cs

@@ -1,22 +1,372 @@
+using System.Text.Json;
 using Microsoft.AspNetCore.Mvc;
+using SVSim.Database.Enums;
+using SVSim.Database.Models;
+using SVSim.Database.Models.Config;
+using SVSim.Database.Repositories.Deck;
+using SVSim.Database.Repositories.Viewer;
+using SVSim.Database.Services;
+using SVSim.Database.Services.Inventory;
+using SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Common.ArenaTwoPick;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Requests;
 using SVSim.EmulatedEntrypoint.Models.Dtos.Requests.ArenaColosseum;
 using SVSim.EmulatedEntrypoint.Models.Dtos.Responses.ArenaColosseum;
 
 namespace SVSim.EmulatedEntrypoint.Controllers;
 
 /// <summary>
-/// Stub controller for the Colosseum arena family. Currently only emits a "no Colosseum
+/// Arena Colosseum (Grand Prix) lobby. Phase 1 covers the three read endpoints (<c>/top</c>,
-/// period" /get_fee_info response so the home/arena screen doesn't 404. The full Colosseum
+/// <c>/get_fee_info</c>, <c>/event_info</c>) plus the entry/register-deck pair. Defaults to
-/// flow (top, entry, register_deck, event_info, retire, finish, class_choose, card_choose,
+/// "no event scheduled" via <see cref="ColosseumSeasonConfig.IsColosseumPeriod"/> — flipping
-/// matchmaking) is deferred — see Wizard/ColosseumEntryInfoTask.cs for the parser surface.
+/// the event on is an admin operation per <c>docs/operations/grand-prix-event-setup.md</c>.
 /// </summary>
 [Route("arena_colosseum")]
 public class ArenaColosseumController : SVSimController
 {
-    [HttpPost("get_fee_info")]
+    private readonly IGameConfigService _config;
-    public IActionResult GetFeeInfo([FromBody] GetFeeInfoRequest req)
+    private readonly IArenaColosseumRunRepository _runs;
+    private readonly IInventoryService _inventory;
+    private readonly IDeckRepository _decks;
+
+    public ArenaColosseumController(
+        IGameConfigService config,
+        IArenaColosseumRunRepository runs,
+        IInventoryService inventory,
+        IDeckRepository decks)
     {
-        if (!TryGetViewerId(out _)) return Unauthorized();
+        _config = config;
-        return Ok(new GetFeeInfoResponseDto());
+        _runs = runs;
+        _inventory = inventory;
+        _decks = decks;
     }
+
+    [HttpPost("top")]
+    public async Task<IActionResult> Top([FromBody] BaseRequest _)
+    {
+        if (!TryGetViewerId(out var vid)) return Unauthorized();
+
+        var season = _config.Get<ColosseumSeasonConfig>();
+        var run = await _runs.GetByViewerIdAsync(vid);
+
+        var response = new TopResponse
+        {
+            ColosseumInfo = BuildColosseumInfo(season),
+            ColosseumStatus = BuildOwnStatus(run),
+            LeaderSkinId = run?.LeaderSkinId ?? 0,
+        };
+
+        if (run is not null)
+        {
+            response.EntryInfo = new ColosseumEntryRef { Id = run.EntryId };
+            response.NowRoundId = run.RoundId;
+            response.MaxBattleCount = run.MaxBattleCountThisRound;
+            response.IsFinish = run.IsChampion;
+            response.FinalRoundEliminateCount = season.FinalRoundEliminateCount;
+            response.EndTime = FormatTime(season.EventEndTime);
+            response.BattleResults = new ColosseumBattleResults
+            {
+                WinCount = run.WinCount,
+                ResultList = ParseIntList(run.ResultListJson),
+            };
+            response.BreakthroughNumber = run.BreakthroughNumberThisRound > 0 ? run.BreakthroughNumberThisRound : null;
+        }
+
+        return Ok(response);
+    }
+
+    [HttpPost("get_fee_info")]
+    public async Task<IActionResult> GetFeeInfo([FromBody] BaseRequest _)
+    {
+        if (!TryGetViewerId(out var vid)) return Unauthorized();
+
+        var season = _config.Get<ColosseumSeasonConfig>();
+        var run = await _runs.GetByViewerIdAsync(vid);
+
+        var response = new GetFeeInfoResponseDto
+        {
+            ColosseumInfo = BuildColosseumInfo(season),
+            ColosseumStatus = BuildOwnStatus(run),
+        };
+
+        if (!season.IsColosseumPeriod)
+        {
+            return Ok(response);
+        }
+
+        response.IsUnfinishedEntryExists = run is not null;
+        response.IsAllowedFreeEntry = season.IsAllowedFreeEntry;
+        response.FeeList = new ColosseumFeeList
+        {
+            RupyCost = season.RupyCost,
+            TicketCost = season.TicketCost,
+            CrystalCost = season.CrystalCost,
+        };
+
+        if (run is not null)
+        {
+            response.DeckFormat = (int)run.DeckFormat;
+        }
+
+        return Ok(response);
+    }
+
+    [HttpPost("event_info")]
+    public async Task<IActionResult> EventInfo([FromBody] BaseRequest _)
+    {
+        if (!TryGetViewerId(out var vid)) return Unauthorized();
+
+        var season = _config.Get<ColosseumSeasonConfig>();
+        var rounds = _config.Get<ColosseumRoundsConfig>();
+        var run = await _runs.GetByViewerIdAsync(vid);
+
+        return Ok(new EventInfoResponse
+        {
+            ColosseumInfo = new ColosseumEventInfo
+            {
+                Format = (int)season.DeckFormat,
+                StartTime = FormatTime(season.EventStartTime),
+                EndTime = FormatTime(season.EventEndTime),
+                AnnounceId = season.AnnounceId,
+                FinalRoundEliminateCount = season.FinalRoundEliminateCount,
+            },
+            Round1 = BuildRoundDetail(rounds, 1),
+            Round2 = BuildRoundDetail(rounds, 2),
+            Round3 = BuildRoundDetail(rounds, 3),
+            ColosseumStatus = BuildOwnStatus(run),
+        });
+    }
+
+    [HttpPost("entry")]
+    public async Task<IActionResult> Entry([FromBody] ArenaColosseumEntryRequest req)
+    {
+        if (!TryGetViewerId(out var vid)) return Unauthorized();
+
+        var season = _config.Get<ColosseumSeasonConfig>();
+        if (!season.IsColosseumPeriod)
+        {
+            return BadRequest(new { error = "colosseum_period_closed" });
+        }
+
+        var serverRoundId = ResolveServerRoundId(season);
+        if (req.NowRoundId != serverRoundId)
+        {
+            return BadRequest(new { error = "now_round_id_mismatch", server_round_id = serverRoundId });
+        }
+
+        if (await _runs.GetByViewerIdAsync(vid) is not null)
+        {
+            return BadRequest(new { error = "arena_colosseum_already_in_progress" });
+        }
+
+        await using var tx = await _inventory.BeginAsync(vid);
+
+        RewardEntryDto? feeEntry = req.ConsumeItemType switch
+        {
+            1 => await DebitCrystalAsync(tx, season.CrystalCost),
+            3 => await DebitTicketAsync(tx, season.TicketCost),
+            4 => await DebitRupyAsync(tx, season.RupyCost),
+            5 when season.IsAllowedFreeEntry => null,
+            _ => throw new InvalidOperationException($"invalid consume_item_type {req.ConsumeItemType}"),
+        };
+
+        var rounds = _config.Get<ColosseumRoundsConfig>();
+        var roundConfig = rounds.Rounds.FirstOrDefault(r => r.RoundId == serverRoundId);
+        var group = roundConfig?.Groups.FirstOrDefault();
+
+        var run = new ViewerArenaColosseumRun
+        {
+            ViewerId = vid,
+            EntryId = 0,
+            SeasonId = season.SeasonId,
+            RoundId = serverRoundId,
+            DeckFormat = season.DeckFormat,
+            LeaderSkinId = 0,
+            ConsumeItemType = req.ConsumeItemType,
+            MaxBattleCountThisRound = group?.MaxBattleCount ?? 0,
+            BreakthroughNumberThisRound = group?.BreakthroughNumber ?? 0,
+            RestEntryNum = 0,
+        };
+        await _runs.UpsertAsync(run);
+        run.EntryId = run.Id;
+        await _runs.UpsertAsync(run);
+        await tx.CommitAsync();
+
+        return Ok(new EntryResponse
+        {
+            RewardList = feeEntry is null ? new() : new() { feeEntry },
+            EntryInfo = new ColosseumEntryRef
+            {
+                Id = run.EntryId,
+                DeckFormat = (int)season.DeckFormat,
+            },
+        });
+    }
+
+    [HttpPost("register_deck")]
+    public async Task<IActionResult> RegisterDeck([FromBody] ArenaColosseumRegisterDeckRequest req)
+    {
+        if (!TryGetViewerId(out var vid)) return Unauthorized();
+
+        var run = await _runs.GetByViewerIdAsync(vid);
+        if (run is null)
+        {
+            return BadRequest(new { error = "no_active_run" });
+        }
+
+        List<int> deckNos;
+        try
+        {
+            deckNos = JsonSerializer.Deserialize<List<int>>(req.DeckNoList) ?? new();
+        }
+        catch (JsonException)
+        {
+            return BadRequest(new { error = "deck_no_list_malformed" });
+        }
+
+        if (deckNos.Count == 0)
+        {
+            return BadRequest(new { error = "deck_no_list_empty" });
+        }
+
+        // GetDeck filters by (viewerId, format, deckNo) — a slot that exists under a different
+        // format returns null here, which is the format-mismatch case from the spec.
+        foreach (var no in deckNos)
+        {
+            var deck = await _decks.GetDeck(vid, run.DeckFormat, no);
+            if (deck is null)
+            {
+                return BadRequest(new { error = "deck_not_found", deck_no = no });
+            }
+        }
+
+        run.RegisteredDeckNoListJson = JsonSerializer.Serialize(deckNos);
+        run.IsPublished = req.IsPublished;
+        await _runs.UpsertAsync(run);
+
+        return Ok(new { });
+    }
+
+    private static int ResolveServerRoundId(ColosseumSeasonConfig season) => 1;
+
+    private async Task<RewardEntryDto> DebitCrystalAsync(IInventoryTransaction tx, int cost)
+    {
+        var result = await tx.TrySpendAsync(SpendCurrency.Crystal, cost);
+        if (!result.Success)
+            throw new InvalidOperationException("insufficient_crystal");
+        return new RewardEntryDto
+        {
+            RewardType = (int)UserGoodsType.Crystal,
+            RewardId = 0,
+            RewardNum = (int)result.PostStateTotal,
+        };
+    }
+
+    private async Task<RewardEntryDto> DebitRupyAsync(IInventoryTransaction tx, int cost)
+    {
+        var result = await tx.TrySpendAsync(SpendCurrency.Rupee, cost);
+        if (!result.Success)
+            throw new InvalidOperationException("insufficient_rupy");
+        return new RewardEntryDto
+        {
+            RewardType = (int)UserGoodsType.Rupy,
+            RewardId = 0,
+            RewardNum = (int)result.PostStateTotal,
+        };
+    }
+
+    private async Task<RewardEntryDto> DebitTicketAsync(IInventoryTransaction tx, int cost)
+    {
+        // Colosseum's ticket id is server-internal — using ArenaTwoPick's TicketItemId convention
+        // (item id 1) until a per-season override is captured.
+        const int ticketItemId = 1;
+        var result = await tx.TryDebitAsync(UserGoodsType.Item, ticketItemId, cost);
+        if (!result.Success)
+            throw new InvalidOperationException("insufficient_ticket");
+        return new RewardEntryDto
+        {
+            RewardType = (int)UserGoodsType.Item,
+            RewardId = ticketItemId,
+            RewardNum = (int)result.PostStateTotal,
+        };
+    }
+
+    // --- helpers ---
+
+    private static ColosseumLobbyInfo BuildColosseumInfo(ColosseumSeasonConfig season)
+    {
+        if (!season.IsColosseumPeriod)
+        {
+            return new ColosseumLobbyInfo { IsColosseumPeriod = false };
+        }
+
+        return new ColosseumLobbyInfo
+        {
+            IsColosseumPeriod = true,
+            DeckFormat = (int)season.DeckFormat,
+            IsNormalTwoPick = season.IsNormalTwoPick ? "1" : "0",
+            ColosseumName = season.ColosseumName,
+            IsRoundPeriod = true,
+            IsSpecialMode = season.IsSpecialMode,
+            CardPoolName = string.IsNullOrEmpty(season.CardPoolName) ? null : season.CardPoolName,
+            NowRound = 1,
+            StartTime = FormatTime(season.EventStartTime),
+            EndTime = FormatTime(season.EventEndTime),
+            IsAllCardEnabled = season.IsAllCardEnabled ? 1 : 0,
+            SalesPeriodInfo = new SVSim.EmulatedEntrypoint.Models.Dtos.ColosseumSalesPeriodInfo
+            {
+                SalesPeriodTime = FormatTime(season.SalesPeriodEnd),
+            },
+            StrategyPickNum = season.StrategyPickNum > 0 ? season.StrategyPickNum : null,
+        };
+    }
+
+    /// <summary>Builds the <c>colosseum_status</c> block. When the viewer has no run, every
+    /// property is null and global WhenWritingNull renders <c>{}</c> — the client
+    /// (<c>SetColosseumOwnStatus</c>) short-circuits on <c>status.Count == 0</c>.</summary>
+    private static ColosseumOwnStatus BuildOwnStatus(ViewerArenaColosseumRun? run)
+    {
+        if (run is null) return new ColosseumOwnStatus();
+
+        return new ColosseumOwnStatus
+        {
+            RestEntryNum = run.RestEntryNum,
+            NowRoundId = run.RoundId,
+            IsChampion = run.IsChampion ? true : null,
+        };
+    }
+
+    private static ColosseumRoundDetail BuildRoundDetail(ColosseumRoundsConfig rounds, int roundId)
+    {
+        var match = rounds.Rounds.FirstOrDefault(r => r.RoundId == roundId);
+        if (match is null) return new ColosseumRoundDetail();
+
+        return new ColosseumRoundDetail
+        {
+            StartTime = FormatTime(match.StartTime),
+            EndTime = FormatTime(match.EndTime),
+            IsNowRound = IsNowRound(match),
+            RoundDetail = match.Groups.Select(g => new ColosseumGroupRow
+            {
+                Group = g.Group,
+                MaxBattleCount = g.MaxBattleCount,
+                BreakthroughNumber = g.BreakthroughNumber,
+                EntryNumber = g.EntryNumber,
+            }).ToList(),
+        };
+    }
+
+    private static bool IsNowRound(ColosseumRoundsConfig.RoundEntry round)
+    {
+        var now = DateTime.UtcNow;
+        return now >= round.StartTime && now <= round.EndTime;
+    }
+
+    private static string FormatTime(DateTime t) =>
+        t == default ? "" : t.ToString("yyyy-MM-dd HH:mm:ss");
+
+    private static List<int> ParseIntList(string json) =>
+        string.IsNullOrEmpty(json)
+            ? new()
+            : System.Text.Json.JsonSerializer.Deserialize<List<int>>(json) ?? new();
 }

SVSim.EmulatedEntrypoint/Models/Dtos/ArenaColosseum/ColosseumBattleResults.cs

@@ -0,0 +1,15 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+
+[MessagePackObject]
+public class ColosseumBattleResults
+{
+    [JsonPropertyName("win_count")] [Key("win_count")]
+    public int WinCount { get; set; }
+
+    /// <summary>0 = loss, 1 = win. Client iterates as bool list.</summary>
+    [JsonPropertyName("result_list")] [Key("result_list")]
+    public List<int> ResultList { get; set; } = new();
+}

SVSim.EmulatedEntrypoint/Models/Dtos/ArenaColosseum/ColosseumEntryRef.cs

@@ -0,0 +1,16 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+
+/// <summary>Wire <c>entry_info</c> object on <c>/top</c> and <c>/entry</c>. Reused across endpoints.</summary>
+[MessagePackObject]
+public class ColosseumEntryRef
+{
+    [JsonPropertyName("id")] [Key("id")]
+    public long Id { get; set; }
+
+    /// <summary>Used by <c>/entry</c> only — Format enum integer. Top emits via colosseum_info.</summary>
+    [JsonPropertyName("deck_format")] [Key("deck_format")]
+    public int? DeckFormat { get; set; }
+}

SVSim.EmulatedEntrypoint/Models/Dtos/ArenaColosseum/ColosseumEventInfo.cs

@@ -0,0 +1,63 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+
+/// <summary>
+/// Event-level descriptor used by <c>/event_info</c> only — distinct shape from
+/// <see cref="ColosseumInfo"/>: only <c>format</c>, the event window, the announce id,
+/// and the final-round eliminate count. The client's <c>ColosseumDetailTask</c> reads
+/// these five fields plus the three string-keyed rounds.
+/// </summary>
+[MessagePackObject]
+public class ColosseumEventInfo
+{
+    /// <summary>Event format. Mapped via <c>ApiRuleParseAndSet</c> on the client.</summary>
+    [JsonPropertyName("format")] [Key("format")]
+    public int Format { get; set; }
+
+    [JsonPropertyName("start_time")] [Key("start_time")]
+    public string StartTime { get; set; } = "";
+
+    [JsonPropertyName("end_time")] [Key("end_time")]
+    public string EndTime { get; set; } = "";
+
+    /// <summary>Optional — emit <c>null</c> when no announce content is configured.</summary>
+    [JsonPropertyName("announce_id")] [Key("announce_id")]
+    public string? AnnounceId { get; set; }
+
+    [JsonPropertyName("final_round_eliminate_count")] [Key("final_round_eliminate_count")]
+    public int FinalRoundEliminateCount { get; set; }
+}
+
+[MessagePackObject]
+public class ColosseumRoundDetail
+{
+    [JsonPropertyName("start_time")] [Key("start_time")]
+    public string StartTime { get; set; } = "";
+
+    [JsonPropertyName("end_time")] [Key("end_time")]
+    public string EndTime { get; set; } = "";
+
+    [JsonPropertyName("is_now_round")] [Key("is_now_round")]
+    public bool IsNowRound { get; set; }
+
+    [JsonPropertyName("round_detail")] [Key("round_detail")]
+    public List<ColosseumGroupRow> RoundDetail { get; set; } = new();
+}
+
+[MessagePackObject]
+public class ColosseumGroupRow
+{
+    [JsonPropertyName("group")] [Key("group")]
+    public string Group { get; set; } = "";
+
+    [JsonPropertyName("max_battle_count")] [Key("max_battle_count")]
+    public int MaxBattleCount { get; set; }
+
+    [JsonPropertyName("breakthrough_number")] [Key("breakthrough_number")]
+    public int BreakthroughNumber { get; set; }
+
+    [JsonPropertyName("entry_number")] [Key("entry_number")]
+    public int EntryNumber { get; set; }
+}

SVSim.EmulatedEntrypoint/Models/Dtos/ArenaColosseum/ColosseumFeeList.cs

@@ -0,0 +1,17 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+
+[MessagePackObject]
+public class ColosseumFeeList
+{
+    [JsonPropertyName("rupy_cost")] [Key("rupy_cost")]
+    public int RupyCost { get; set; }
+
+    [JsonPropertyName("ticket_cost")] [Key("ticket_cost")]
+    public int TicketCost { get; set; }
+
+    [JsonPropertyName("crystal_cost")] [Key("crystal_cost")]
+    public int CrystalCost { get; set; }
+}

SVSim.EmulatedEntrypoint/Models/Dtos/ArenaColosseum/ColosseumInfo.cs

@@ -0,0 +1,81 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+
+/// <summary>
+/// Round-level Colosseum descriptor. Shared by <c>/top</c> and <c>/get_fee_info</c> via
+/// the client's static <c>ColosseumEntryInfoTask.SetColosseumInfo</c> helper. When
+/// <see cref="IsColosseumPeriod"/> is <c>false</c>, the client skips parsing every other
+/// field — server still emits this minimal payload so the lobby renders cleanly.
+/// <para>
+/// Distinct from <see cref="SVSim.EmulatedEntrypoint.Models.Dtos.ColosseumInfo"/> (the
+/// captured prod <c>/mypage/index</c> shape — stringly-typed and read-only). This is the
+/// per-endpoint Colosseum-family shape. <c>/event_info</c> uses yet a third shape —
+/// <see cref="ColosseumEventInfo"/>.
+/// </para>
+/// </summary>
+[MessagePackObject]
+public class ColosseumLobbyInfo
+{
+    /// <summary>Master gate. <c>false</c> = lobby renders empty.</summary>
+    [JsonPropertyName("is_colosseum_period")] [Key("is_colosseum_period")]
+    public bool IsColosseumPeriod { get; set; }
+
+    /// <summary>Format enum (Rotation=0, Unlimited=1, TwoPick=10, HOF=31, ...).</summary>
+    [JsonPropertyName("deck_format")] [Key("deck_format")]
+    public int? DeckFormat { get; set; }
+
+    /// <summary>STRING wire shape: <c>"0"</c>/<c>"1"</c>. Client parses with
+    /// <c>jsonData.ToString() == "1"</c>.</summary>
+    [JsonPropertyName("is_normal_two_pick")] [Key("is_normal_two_pick")]
+    public string? IsNormalTwoPick { get; set; }
+
+    [JsonPropertyName("colosseum_name")] [Key("colosseum_name")]
+    public string? ColosseumName { get; set; }
+
+    [JsonPropertyName("is_round_period")] [Key("is_round_period")]
+    public bool? IsRoundPeriod { get; set; }
+
+    /// <summary>Wire STRING used by the client as a UI color/theme code.</summary>
+    [JsonPropertyName("is_special_mode")] [Key("is_special_mode")]
+    public string? IsSpecialMode { get; set; }
+
+    [JsonPropertyName("card_pool_name")] [Key("card_pool_name")]
+    public string? CardPoolName { get; set; }
+
+    /// <summary>Present during round period — current stage number (1..3).</summary>
+    [JsonPropertyName("now_round")] [Key("now_round")]
+    public int? NowRound { get; set; }
+
+    /// <summary>Present outside round period — next stage number.</summary>
+    [JsonPropertyName("next_round")] [Key("next_round")]
+    public int? NextRound { get; set; }
+
+    [JsonPropertyName("start_time")] [Key("start_time")]
+    public string? StartTime { get; set; }
+
+    [JsonPropertyName("end_time")] [Key("end_time")]
+    public string? EndTime { get; set; }
+
+    [JsonPropertyName("is_display_tips")] [Key("is_display_tips")]
+    public int? IsDisplayTips { get; set; }
+
+    [JsonPropertyName("colosseum_id")] [Key("colosseum_id")]
+    public int? ColosseumId { get; set; }
+
+    [JsonPropertyName("tips_id")] [Key("tips_id")]
+    public int? TipsId { get; set; }
+
+    [JsonPropertyName("is_all_card_enabled")] [Key("is_all_card_enabled")]
+    public int? IsAllCardEnabled { get; set; }
+
+    /// <summary>Reuses the captured <c>/mypage/index</c> shape — single
+    /// <c>sales_period_time</c> field per prod capture.</summary>
+    [JsonPropertyName("sales_period_info")] [Key("sales_period_info")]
+    public ColosseumSalesPeriodInfo? SalesPeriodInfo { get; set; }
+
+    [JsonPropertyName("strategy_pick_num")] [Key("strategy_pick_num")]
+    public int? StrategyPickNum { get; set; }
+}

SVSim.EmulatedEntrypoint/Models/Dtos/ArenaColosseum/ColosseumOwnStatus.cs

@@ -0,0 +1,33 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+
+/// <summary>
+/// Per-viewer Colosseum state. All fields optional — when the viewer has no run, ALL fields
+/// are null and the global <c>WhenWritingNull</c> policy renders this as <c>{}</c>, which
+/// the client's <c>SetColosseumOwnStatus</c> short-circuits with <c>status.Count != 0</c>.
+/// </summary>
+[MessagePackObject]
+public class ColosseumOwnStatus
+{
+    [JsonPropertyName("rest_entry_num")] [Key("rest_entry_num")]
+    public int? RestEntryNum { get; set; }
+
+    [JsonPropertyName("now_round_id")] [Key("now_round_id")]
+    public int? NowRoundId { get; set; }
+
+    [JsonPropertyName("next_round_id")] [Key("next_round_id")]
+    public int? NextRoundId { get; set; }
+
+    [JsonPropertyName("is_last_day")] [Key("is_last_day")]
+    public bool? IsLastDay { get; set; }
+
+    [JsonPropertyName("is_champion")] [Key("is_champion")]
+    public bool? IsChampion { get; set; }
+
+    /// <summary>Only present when <see cref="IsChampion"/> is true — client uses it to overwrite
+    /// <c>ColosseumData.Name</c> for the champion screen.</summary>
+    [JsonPropertyName("colosseum_name")] [Key("colosseum_name")]
+    public string? ColosseumName { get; set; }
+}

SVSim.EmulatedEntrypoint/Models/Dtos/ArenaColosseum/ColosseumUserDeck.cs

@@ -0,0 +1,26 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+
+/// <summary>Lightweight deck-info shape for <c>/top</c>'s <c>user_deck[0]</c>. The client's
+/// <c>DeckData.Initialize</c> consumes the canonical deck shape; this is the minimum needed
+/// to render the deck preview in Phase 1.</summary>
+[MessagePackObject]
+public class ColosseumUserDeck
+{
+    [JsonPropertyName("deck_id")] [Key("deck_id")]
+    public long DeckId { get; set; }
+
+    [JsonPropertyName("class_id")] [Key("class_id")]
+    public int ClassId { get; set; }
+
+    [JsonPropertyName("card_list")] [Key("card_list")]
+    public List<long> CardList { get; set; } = new();
+
+    [JsonPropertyName("sleeve_id")] [Key("sleeve_id")]
+    public long? SleeveId { get; set; }
+
+    [JsonPropertyName("skin_id")] [Key("skin_id")]
+    public long? SkinId { get; set; }
+}

SVSim.EmulatedEntrypoint/Models/Dtos/Requests/ArenaColosseum/ArenaColosseumEntryRequest.cs

@@ -0,0 +1,22 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Requests;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Requests.ArenaColosseum;
+
+/// <summary>
+/// <c>POST /arena_colosseum/entry</c> — pay the entry cost and start a Colosseum bracket
+/// attempt. Maps to <c>Wizard/ColosseumEntryTask.ColosseumEntryTaskParam</c>.
+/// </summary>
+[MessagePackObject(keyAsPropertyName: false)]
+public class ArenaColosseumEntryRequest : BaseRequest
+{
+    /// <summary>Currency selector — eARENA_PAY enum. 1=Crystal, 3=Ticket, 4=Rupy, 5=Free.</summary>
+    [JsonPropertyName("consume_item_type")] [Key("consume_item_type")]
+    public int ConsumeItemType { get; set; }
+
+    /// <summary>Client-echoed round id from the most recent <c>/get_fee_info</c> or <c>/top</c>.
+    /// Server rejects if it disagrees with the current server-decided round.</summary>
+    [JsonPropertyName("now_round_id")] [Key("now_round_id")]
+    public int NowRoundId { get; set; }
+}

SVSim.EmulatedEntrypoint/Models/Dtos/Requests/ArenaColosseum/ArenaColosseumRegisterDeckRequest.cs

@@ -0,0 +1,22 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Requests;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Requests.ArenaColosseum;
+
+/// <summary>
+/// <c>POST /arena_colosseum/register_deck</c> — submit deck slot(s) for a constructed-format
+/// entry. Same wire gotcha as <c>arena_competition/register_deck</c> et al — <see cref="DeckNoList"/>
+/// is a JSON-encoded STRING like <c>"[3,4,5]"</c>, not an array. The server parses it.
+/// </summary>
+[MessagePackObject(keyAsPropertyName: false)]
+public class ArenaColosseumRegisterDeckRequest : BaseRequest
+{
+    /// <summary>JSON-encoded list of deck slot numbers. Client does <c>JsonMapper.ToJson(List&lt;int&gt;)</c>.</summary>
+    [JsonPropertyName("deck_no_list")] [Key("deck_no_list")]
+    public string DeckNoList { get; set; } = "[]";
+
+    /// <summary>Server-stored visibility flag — does not affect bracket play.</summary>
+    [JsonPropertyName("is_published")] [Key("is_published")]
+    public bool IsPublished { get; set; }
+}

SVSim.EmulatedEntrypoint/Models/Dtos/Requests/ArenaColosseum/GetFeeInfoRequest.cs

@@ -1,6 +0,0 @@
-using MessagePack;
-
-namespace SVSim.EmulatedEntrypoint.Models.Dtos.Requests.ArenaColosseum;
-
-[MessagePackObject]
-public class GetFeeInfoRequest : BaseRequest { }

SVSim.EmulatedEntrypoint/Models/Dtos/Responses/ArenaColosseum/EntryResponse.cs

@@ -0,0 +1,22 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+using SVSim.EmulatedEntrypoint.Models.Dtos.Common.ArenaTwoPick;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Responses.ArenaColosseum;
+
+/// <summary>
+/// <c>POST /arena_colosseum/entry</c>. Sparse — only <c>reward_list</c> (wallet debit) +
+/// <c>entry_info.deck_format</c>. Client refreshes full lobby state via the next <c>/top</c>.
+/// Reuses <see cref="RewardEntryDto"/> from arena-two-pick — the wire shape is identical
+/// (<c>reward_type/reward_id/reward_num</c> per <c>UpdateHaveUserGoodsNumByJsonData</c>).
+/// </summary>
+[MessagePackObject]
+public class EntryResponse
+{
+    [JsonPropertyName("reward_list")] [Key("reward_list")]
+    public List<RewardEntryDto> RewardList { get; set; } = new();
+
+    [JsonPropertyName("entry_info")] [Key("entry_info")]
+    public ColosseumEntryRef EntryInfo { get; set; } = new();
+}

SVSim.EmulatedEntrypoint/Models/Dtos/Responses/ArenaColosseum/EventInfoResponse.cs

@@ -0,0 +1,31 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Responses.ArenaColosseum;
+
+/// <summary>
+/// <c>POST /arena_colosseum/event_info</c>. The 3-round Colosseum bracket descriptor — note
+/// the rounds are STRING-keyed (<c>"1"</c>, <c>"2"</c>, <c>"3"</c>), NOT an array. The
+/// client iterates <c>for (i = 1; i &lt;= 3; i++) jsonData[i.ToString()]</c>. Using three
+/// explicit <c>[JsonPropertyName("1"|"2"|"3")]</c> properties is simpler than a custom STJ
+/// converter and round-trips cleanly through MessagePack via matching <c>[Key("1"|...)]</c>.
+/// </summary>
+[MessagePackObject]
+public class EventInfoResponse
+{
+    [JsonPropertyName("colosseum_info")] [Key("colosseum_info")]
+    public ColosseumEventInfo ColosseumInfo { get; set; } = new();
+
+    [JsonPropertyName("1")] [Key("1")]
+    public ColosseumRoundDetail Round1 { get; set; } = new();
+
+    [JsonPropertyName("2")] [Key("2")]
+    public ColosseumRoundDetail Round2 { get; set; } = new();
+
+    [JsonPropertyName("3")] [Key("3")]
+    public ColosseumRoundDetail Round3 { get; set; } = new();
+
+    [JsonPropertyName("colosseum_status")] [Key("colosseum_status")]
+    public ColosseumOwnStatus ColosseumStatus { get; set; } = new();
+}

SVSim.EmulatedEntrypoint/Models/Dtos/Responses/ArenaColosseum/GetFeeInfoResponseDto.cs

@@ -1,39 +1,46 @@
 using System.Text.Json.Serialization;
 using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
 
 namespace SVSim.EmulatedEntrypoint.Models.Dtos.Responses.ArenaColosseum;
 
 /// <summary>
-/// Minimum-viable stub for /arena_colosseum/get_fee_info — emits is_colosseum_period:false
+/// <c>POST /arena_colosseum/get_fee_info</c> — pre-entry oracle. Most fields are optional;
-/// so the client (Wizard/ColosseumEntryInfoTask.cs:99) skips the rest of the parse and the
+/// presence drives the lobby state machine on the client side
-/// home/arena screen renders without 404ing. TODO: implement the full Colosseum entry flow
+/// (<c>Wizard/ColosseumEntryInfoTask.cs</c>). When no season is active, only
-/// when the Colosseum format is brought online.
+/// <see cref="ColosseumInfo"/> + <see cref="ColosseumStatus"/> are emitted (the former with
+/// <c>is_colosseum_period:false</c>, the latter as <c>{}</c> via WhenWritingNull stripping).
 /// </summary>
 [MessagePackObject]
 public class GetFeeInfoResponseDto
 {
-    /// <summary>
-    /// Per-viewer Colosseum entry status (rest_entry_num, now_round_id, is_last_day, etc.).
-    /// Empty object — client (ColosseumEntryInfoTask.cs:146) guards with `if (status.Count != 0)`,
-    /// so an empty dict short-circuits cleanly.
-    /// </summary>
-    [JsonPropertyName("colosseum_status")] [Key("colosseum_status")]
-    public ColosseumStatusDto ColosseumStatus { get; set; } = new();
-
     [JsonPropertyName("colosseum_info")] [Key("colosseum_info")]
-    public ColosseumInfoDto ColosseumInfo { get; set; } = new();
+    public ColosseumLobbyInfo ColosseumInfo { get; set; } = new();
-}
 
-[MessagePackObject]
+    [JsonPropertyName("colosseum_status")] [Key("colosseum_status")]
-public class ColosseumStatusDto { }
+    public ColosseumOwnStatus ColosseumStatus { get; set; } = new();
 
-[MessagePackObject]
+    [JsonPropertyName("is_unfinished_entry_exists")] [Key("is_unfinished_entry_exists")]
-public class ColosseumInfoDto
+    public bool? IsUnfinishedEntryExists { get; set; }
-{
+
-    /// <summary>
+    [JsonPropertyName("is_allowed_free_entry")] [Key("is_allowed_free_entry")]
-    /// false = no Colosseum event running. Client (ColosseumEntryInfoTask.cs:100) gates every
+    public bool? IsAllowedFreeEntry { get; set; }
-    /// other field on this — emitting false is what lets us ship an otherwise-empty info block.
+
-    /// </summary>
+    [JsonPropertyName("fee_list")] [Key("fee_list")]
-    [JsonPropertyName("is_colosseum_period")] [Key("is_colosseum_period")]
+    public ColosseumFeeList? FeeList { get; set; }
-    public bool IsColosseumPeriod { get; set; } = false;
+
+    [JsonPropertyName("deck_format")] [Key("deck_format")]
+    public int? DeckFormat { get; set; }
+
+    [JsonPropertyName("is_able_to_join_round_3")] [Key("is_able_to_join_round_3")]
+    public bool? IsAbleToJoinRound3 { get; set; }
+
+    [JsonPropertyName("is_already_entry_final_round")] [Key("is_already_entry_final_round")]
+    public bool? IsAlreadyEntryFinalRound { get; set; }
+
+    [JsonPropertyName("is_deck_deleted")] [Key("is_deck_deleted")]
+    public bool? IsDeckDeleted { get; set; }
+
+    [JsonPropertyName("two_pick_status")] [Key("two_pick_status")]
+    public int? TwoPickStatus { get; set; }
 }

SVSim.EmulatedEntrypoint/Models/Dtos/Responses/ArenaColosseum/TopResponse.cs

@@ -0,0 +1,61 @@
+using System.Text.Json.Serialization;
+using MessagePack;
+using SVSim.EmulatedEntrypoint.Models.Dtos.ArenaColosseum;
+
+namespace SVSim.EmulatedEntrypoint.Models.Dtos.Responses.ArenaColosseum;
+
+/// <summary>
+/// <c>POST /arena_colosseum/top</c> — lobby state for an in-progress run. When no season is
+/// active <see cref="ColosseumInfo.IsColosseumPeriod"/> is <c>false</c> and most other
+/// fields are absent (the client guards on that flag before reading anything else).
+/// </summary>
+[MessagePackObject]
+public class TopResponse
+{
+    [JsonPropertyName("entry_info")] [Key("entry_info")]
+    public ColosseumEntryRef EntryInfo { get; set; } = new();
+
+    [JsonPropertyName("colosseum_info")] [Key("colosseum_info")]
+    public ColosseumLobbyInfo ColosseumInfo { get; set; } = new();
+
+    [JsonPropertyName("colosseum_status")] [Key("colosseum_status")]
+    public ColosseumOwnStatus ColosseumStatus { get; set; } = new();
+
+    [JsonPropertyName("now_round_id")] [Key("now_round_id")]
+    public int NowRoundId { get; set; }
+
+    [JsonPropertyName("user_deck")] [Key("user_deck")]
+    public List<ColosseumUserDeck> UserDeck { get; set; } = new();
+
+    [JsonPropertyName("max_battle_count")] [Key("max_battle_count")]
+    public int MaxBattleCount { get; set; }
+
+    [JsonPropertyName("is_finish")] [Key("is_finish")]
+    public bool IsFinish { get; set; }
+
+    [JsonPropertyName("final_round_eliminate_count")] [Key("final_round_eliminate_count")]
+    public int FinalRoundEliminateCount { get; set; }
+
+    [JsonPropertyName("end_time")] [Key("end_time")]
+    public string EndTime { get; set; } = "";
+
+    [JsonPropertyName("battle_results")] [Key("battle_results")]
+    public ColosseumBattleResults BattleResults { get; set; } = new();
+
+    [JsonPropertyName("breakthrough_number")] [Key("breakthrough_number")]
+    public int? BreakthroughNumber { get; set; }
+
+    [JsonPropertyName("box_grade_list")] [Key("box_grade_list")]
+    public List<int>? BoxGradeList { get; set; }
+
+    [JsonPropertyName("selected_chaos_id")] [Key("selected_chaos_id")]
+    public int? SelectedChaosId { get; set; }
+
+    /// <summary>ALWAYS emitted, even when 0. <c>WhenWritingNull</c> would strip this otherwise —
+    /// see <c>project_wire_null_policy</c>: client does <c>jsonData["leader_skin_id"].ToInt()</c>
+    /// unguarded, which throws a KeyNotFoundException if absent.</summary>
+    [JsonPropertyName("leader_skin_id")]
+    [JsonIgnore(Condition = JsonIgnoreCondition.Never)]
+    [Key("leader_skin_id")]
+    public long LeaderSkinId { get; set; }
+}

SVSim.EmulatedEntrypoint/Program.cs

@@ -106,6 +106,7 @@ public class Program
         builder.Services.AddScoped<IStoryMasterRepository, StoryMasterRepository>();
         builder.Services.AddScoped<IViewerStoryProgressRepository, ViewerStoryProgressRepository>();
         builder.Services.AddScoped<IArenaTwoPickRunRepository, ArenaTwoPickRunRepository>();
+        builder.Services.AddScoped<IArenaColosseumRunRepository, ArenaColosseumRunRepository>();
         builder.Services.AddScoped<IArenaTwoPickCardPoolService, ArenaTwoPickCardPoolService>();
         builder.Services.AddScoped<IArenaTwoPickService, ArenaTwoPickService>();
         builder.Services.AddScoped<IMatchContextBuilder, MatchContextBuilder>();

SVSim.UnitTests/Controllers/ArenaColosseumControllerEntryTests.cs

@@ -0,0 +1,238 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text.Json;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.Database;
+using SVSim.Database.Enums;
+using SVSim.Database.Models;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Controllers;
+
+/// <summary>
+/// Phase 1 entry + register-deck coverage. Activating the Colosseum season requires writing
+/// a <c>ColosseumSeason</c> + <c>ColosseumRounds</c> row to <c>GameConfigs</c> — see
+/// <see cref="ActivateSeasonAsync"/> for the test-only equivalent of the admin flow.
+/// </summary>
+public class ArenaColosseumControllerEntryTests
+{
+    private static readonly object Envelope =
+        new { viewer_id = "0", steam_id = 0, steam_session_ticket = "" };
+
+    private static async Task ActivateSeasonAsync(SVSimTestFactory factory, int crystalCost = 300)
+    {
+        using var scope = factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+
+        var seasonJson = JsonSerializer.Serialize(new
+        {
+            IsColosseumPeriod = true,
+            SeasonId = 42,
+            ColosseumName = "Test Cup",
+            DeckFormat = (int)Format.Rotation,
+            CrystalCost = crystalCost,
+            RupyCost = 3000,
+            TicketCost = 1,
+            IsAllowedFreeEntry = false,
+        });
+        await UpsertConfigAsync(db, "ColosseumSeason", seasonJson);
+
+        var roundsJson = JsonSerializer.Serialize(new
+        {
+            Rounds = new[]
+            {
+                new
+                {
+                    RoundId = 1,
+                    StartTime = DateTime.UtcNow.AddDays(-1),
+                    EndTime = DateTime.UtcNow.AddDays(7),
+                    Groups = new[]
+                    {
+                        new { Group = "", MaxBattleCount = 5, BreakthroughNumber = 4, EntryNumber = 100_000 },
+                    },
+                },
+            },
+        });
+        await UpsertConfigAsync(db, "ColosseumRounds", roundsJson);
+    }
+
+    private static async Task UpsertConfigAsync(SVSimDbContext db, string section, string json)
+    {
+        var existing = await db.GameConfigs.FirstOrDefaultAsync(s => s.SectionName == section);
+        if (existing is null)
+            db.GameConfigs.Add(new GameConfigSection { SectionName = section, ValueJson = json });
+        else
+            existing.ValueJson = json;
+        await db.SaveChangesAsync();
+    }
+
+    private static async Task SetViewerCurrencyAsync(SVSimTestFactory factory, long viewerId, ulong crystals = 0, ulong rupees = 0)
+    {
+        using var scope = factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var viewer = await db.Viewers.FirstAsync(v => v.Id == viewerId);
+        viewer.Currency.Crystals = crystals;
+        viewer.Currency.Rupees = rupees;
+        await db.SaveChangesAsync();
+    }
+
+    [Test]
+    public async Task Entry_debits_crystal_and_creates_run()
+    {
+        using var factory = new SVSimTestFactory();
+        await ActivateSeasonAsync(factory, crystalCost: 300);
+        var viewerId = await factory.SeedViewerAsync();
+        await SetViewerCurrencyAsync(factory, viewerId, crystals: 1000);
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var resp = await client.PostAsync("/arena_colosseum/entry",
+            JsonContent.Create(new { consume_item_type = 1, now_round_id = 1, viewer_id = "0", steam_id = 0, steam_session_ticket = "" }));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+
+        var body = await resp.Content.ReadAsStringAsync();
+        using var doc = JsonDocument.Parse(body);
+        var root = doc.RootElement;
+        Assert.That(root.GetProperty("reward_list").GetArrayLength(), Is.EqualTo(1));
+        Assert.That(root.GetProperty("reward_list")[0].GetProperty("reward_type").GetInt32(), Is.EqualTo((int)UserGoodsType.Crystal));
+        Assert.That(root.GetProperty("entry_info").GetProperty("deck_format").GetInt32(), Is.EqualTo((int)Format.Rotation));
+
+        using var scope = factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var run = await db.ViewerArenaColosseumRuns.FirstOrDefaultAsync(r => r.ViewerId == viewerId);
+        Assert.That(run, Is.Not.Null);
+        Assert.That(run!.SeasonId, Is.EqualTo(42));
+        Assert.That(run.MaxBattleCountThisRound, Is.EqualTo(5));
+        Assert.That(run.BreakthroughNumberThisRound, Is.EqualTo(4));
+
+        var viewerAfter = await db.Viewers.FirstAsync(v => v.Id == viewerId);
+        Assert.That(viewerAfter.Currency.Crystals, Is.EqualTo(700UL), "1000 - 300 cost");
+    }
+
+    [Test]
+    public async Task Entry_rejects_when_season_inactive()
+    {
+        using var factory = new SVSimTestFactory();
+        var viewerId = await factory.SeedViewerAsync();
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var resp = await client.PostAsync("/arena_colosseum/entry",
+            JsonContent.Create(new { consume_item_type = 1, now_round_id = 1, viewer_id = "0", steam_id = 0, steam_session_ticket = "" }));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.BadRequest));
+
+        var body = await resp.Content.ReadAsStringAsync();
+        StringAssert.Contains("colosseum_period_closed", body);
+    }
+
+    [Test]
+    public async Task Entry_rejects_when_already_in_run()
+    {
+        using var factory = new SVSimTestFactory();
+        await ActivateSeasonAsync(factory);
+        var viewerId = await factory.SeedViewerAsync();
+        await SetViewerCurrencyAsync(factory, viewerId, crystals: 1000);
+
+        using (var scope = factory.Services.CreateScope())
+        {
+            var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+            db.ViewerArenaColosseumRuns.Add(new ViewerArenaColosseumRun
+            {
+                ViewerId = viewerId,
+                EntryId = 999,
+                SeasonId = 42,
+                RoundId = 1,
+                DeckFormat = Format.Rotation,
+            });
+            await db.SaveChangesAsync();
+        }
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var resp = await client.PostAsync("/arena_colosseum/entry",
+            JsonContent.Create(new { consume_item_type = 1, now_round_id = 1, viewer_id = "0", steam_id = 0, steam_session_ticket = "" }));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.BadRequest));
+
+        var body = await resp.Content.ReadAsStringAsync();
+        StringAssert.Contains("arena_colosseum_already_in_progress", body);
+    }
+
+    [Test]
+    public async Task Entry_rejects_when_now_round_id_mismatch()
+    {
+        using var factory = new SVSimTestFactory();
+        await ActivateSeasonAsync(factory);
+        var viewerId = await factory.SeedViewerAsync();
+        await SetViewerCurrencyAsync(factory, viewerId, crystals: 1000);
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var resp = await client.PostAsync("/arena_colosseum/entry",
+            JsonContent.Create(new { consume_item_type = 1, now_round_id = 7, viewer_id = "0", steam_id = 0, steam_session_ticket = "" }));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.BadRequest));
+
+        var body = await resp.Content.ReadAsStringAsync();
+        StringAssert.Contains("now_round_id_mismatch", body);
+    }
+
+    [Test]
+    public async Task RegisterDeck_round_trips_deck_no_list()
+    {
+        using var factory = new SVSimTestFactory();
+        await ActivateSeasonAsync(factory);
+        var viewerId = await factory.SeedViewerAsync();
+        await factory.SeedDeckAsync(viewerId, Format.Rotation, number: 3, name: "Colo Deck 3");
+
+        using (var scope = factory.Services.CreateScope())
+        {
+            var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+            db.ViewerArenaColosseumRuns.Add(new ViewerArenaColosseumRun
+            {
+                ViewerId = viewerId,
+                EntryId = 999,
+                SeasonId = 42,
+                RoundId = 1,
+                DeckFormat = Format.Rotation,
+            });
+            await db.SaveChangesAsync();
+        }
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var resp = await client.PostAsync("/arena_colosseum/register_deck",
+            JsonContent.Create(new { deck_no_list = "[3]", is_published = true, viewer_id = "0", steam_id = 0, steam_session_ticket = "" }));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+
+        using var verifyScope = factory.Services.CreateScope();
+        var verifyDb = verifyScope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var run = await verifyDb.ViewerArenaColosseumRuns.FirstAsync(r => r.ViewerId == viewerId);
+        Assert.That(run.RegisteredDeckNoListJson, Is.EqualTo("[3]"));
+        Assert.That(run.IsPublished, Is.True);
+    }
+
+    [Test]
+    public async Task RegisterDeck_rejects_when_deck_not_found()
+    {
+        using var factory = new SVSimTestFactory();
+        await ActivateSeasonAsync(factory);
+        var viewerId = await factory.SeedViewerAsync();
+
+        using (var scope = factory.Services.CreateScope())
+        {
+            var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+            db.ViewerArenaColosseumRuns.Add(new ViewerArenaColosseumRun
+            {
+                ViewerId = viewerId,
+                EntryId = 999,
+                SeasonId = 42,
+                RoundId = 1,
+                DeckFormat = Format.Rotation,
+            });
+            await db.SaveChangesAsync();
+        }
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var resp = await client.PostAsync("/arena_colosseum/register_deck",
+            JsonContent.Create(new { deck_no_list = "[99]", is_published = false, viewer_id = "0", steam_id = 0, steam_session_ticket = "" }));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.BadRequest));
+
+        var body = await resp.Content.ReadAsStringAsync();
+        StringAssert.Contains("deck_not_found", body);
+    }
+}

SVSim.UnitTests/Controllers/ArenaColosseumControllerTests.cs

@@ -0,0 +1,138 @@
+using System.Net;
+using System.Net.Http.Json;
+using System.Text.Json;
+using Microsoft.Extensions.DependencyInjection;
+using SVSim.Database;
+using SVSim.Database.Enums;
+using SVSim.Database.Models;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Controllers;
+
+/// <summary>
+/// Phase 1 lobby read coverage: /arena_colosseum/{top, get_fee_info, event_info}.
+/// Defaults (no <c>ColosseumSeason</c> override) must render an empty "no event scheduled"
+/// payload — flipping the season on is an admin operation.
+/// </summary>
+public class ArenaColosseumControllerTests
+{
+    private static readonly object Envelope =
+        new { viewer_id = "0", steam_id = 0, steam_session_ticket = "" };
+
+    [Test]
+    public async Task Top_unauthenticated_returns_401()
+    {
+        using var factory = new SVSimTestFactory();
+        using var client = factory.CreateClient();
+        var resp = await client.PostAsync("/arena_colosseum/top", JsonContent.Create(Envelope));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.Unauthorized));
+    }
+
+    [Test]
+    public async Task Top_returns_no_period_when_no_season_active()
+    {
+        using var factory = new SVSimTestFactory();
+        var viewerId = await factory.SeedViewerAsync();
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var resp = await client.PostAsync("/arena_colosseum/top", JsonContent.Create(Envelope));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+
+        var body = await resp.Content.ReadAsStringAsync();
+        StringAssert.Contains("\"is_colosseum_period\":false", body);
+        // leader_skin_id must always be emitted (even when 0) per project_wire_null_policy.
+        StringAssert.Contains("\"leader_skin_id\":0", body);
+    }
+
+    [Test]
+    public async Task GetFeeInfo_returns_no_period_when_no_season_active()
+    {
+        using var factory = new SVSimTestFactory();
+        var viewerId = await factory.SeedViewerAsync();
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var resp = await client.PostAsync("/arena_colosseum/get_fee_info", JsonContent.Create(Envelope));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+
+        var body = await resp.Content.ReadAsStringAsync();
+        StringAssert.Contains("\"is_colosseum_period\":false", body);
+        // fee_list, is_unfinished_entry_exists, deck_format must be ABSENT when no event.
+        StringAssert.DoesNotContain("\"fee_list\"", body);
+        StringAssert.DoesNotContain("\"is_unfinished_entry_exists\"", body);
+    }
+
+    [Test]
+    public async Task EventInfo_returns_empty_rounds_when_default_config()
+    {
+        using var factory = new SVSimTestFactory();
+        var viewerId = await factory.SeedViewerAsync();
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+
+        var resp = await client.PostAsync("/arena_colosseum/event_info", JsonContent.Create(Envelope));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+
+        var body = await resp.Content.ReadAsStringAsync();
+
+        // The rounds object MUST be string-keyed "1"/"2"/"3" — locking the wire shape per
+        // event_info.md. Custom STJ converter avoided; explicit [JsonPropertyName("1"|"2"|"3")]
+        // produces the same on-the-wire bytes.
+        using var doc = JsonDocument.Parse(body);
+        var root = doc.RootElement;
+        Assert.That(root.TryGetProperty("1", out var r1), Is.True, "round '1' must be present");
+        Assert.That(root.TryGetProperty("2", out var r2), Is.True, "round '2' must be present");
+        Assert.That(root.TryGetProperty("3", out var r3), Is.True, "round '3' must be present");
+
+        // Default config → no schedule → is_now_round false on all three.
+        Assert.That(r1.GetProperty("is_now_round").GetBoolean(), Is.False);
+        Assert.That(r2.GetProperty("is_now_round").GetBoolean(), Is.False);
+        Assert.That(r3.GetProperty("is_now_round").GetBoolean(), Is.False);
+
+        Assert.That(r1.GetProperty("round_detail").GetArrayLength(), Is.EqualTo(0));
+    }
+
+    [Test]
+    public async Task Top_round_trips_after_entry_seeded()
+    {
+        using var factory = new SVSimTestFactory();
+        var viewerId = await factory.SeedViewerAsync();
+
+        // Seed an active run directly — Task 3's /entry endpoint will own creation, but
+        // /top must reflect the row's identity when one exists.
+        const long entryId = 12_345L;
+        using (var scope = factory.Services.CreateScope())
+        {
+            var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+            db.ViewerArenaColosseumRuns.Add(new ViewerArenaColosseumRun
+            {
+                ViewerId = viewerId,
+                EntryId = entryId,
+                SeasonId = 1,
+                RoundId = 1,
+                DeckFormat = Format.Rotation,
+                LeaderSkinId = 0,
+                ConsumeItemType = 2,
+                MaxBattleCountThisRound = 5,
+                BreakthroughNumberThisRound = 4,
+                RestEntryNum = 0,
+                WinCount = 1,
+                LossCount = 0,
+                ResultListJson = "[1]",
+            });
+            await db.SaveChangesAsync();
+        }
+
+        using var client = factory.CreateAuthenticatedClient(viewerId);
+        var resp = await client.PostAsync("/arena_colosseum/top", JsonContent.Create(Envelope));
+        Assert.That(resp.StatusCode, Is.EqualTo(HttpStatusCode.OK));
+
+        var body = await resp.Content.ReadAsStringAsync();
+        using var doc = JsonDocument.Parse(body);
+        var root = doc.RootElement;
+
+        Assert.That(root.GetProperty("entry_info").GetProperty("id").GetInt64(), Is.EqualTo(entryId));
+        Assert.That(root.GetProperty("now_round_id").GetInt32(), Is.EqualTo(1));
+        Assert.That(root.GetProperty("max_battle_count").GetInt32(), Is.EqualTo(5));
+        Assert.That(root.GetProperty("battle_results").GetProperty("win_count").GetInt32(), Is.EqualTo(1));
+        Assert.That(root.GetProperty("battle_results").GetProperty("result_list").GetArrayLength(), Is.EqualTo(1));
+    }
+}

SVSim.UnitTests/Database/Config/ColosseumRoundsConfigTests.cs

@@ -0,0 +1,46 @@
+using System.Linq;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using NUnit.Framework;
+using SVSim.Database;
+using SVSim.Database.Models.Config;
+using SVSim.EmulatedEntrypoint.Services;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Database.Config;
+
+[TestFixture]
+public class ColosseumRoundsConfigTests
+{
+    [Test]
+    public void ShippedDefaults_emits_empty_rounds()
+    {
+        var cfg = ColosseumRoundsConfig.ShippedDefaults();
+        Assert.That(cfg.Rounds, Is.Empty,
+            "default ship state has no rounds — /event_info renders a benign empty payload");
+    }
+
+    [Test]
+    public void Has_ConfigSection_attribute_with_name_ColosseumRounds()
+    {
+        var attr = typeof(ColosseumRoundsConfig)
+            .GetCustomAttributes(typeof(ConfigSectionAttribute), false)
+            .Cast<ConfigSectionAttribute>()
+            .FirstOrDefault();
+        Assert.That(attr, Is.Not.Null);
+        Assert.That(attr!.Name, Is.EqualTo("ColosseumRounds"));
+    }
+
+    [Test]
+    public void Get_through_GameConfigService_round_trips_shipped_defaults()
+    {
+        using var factory = new SVSimTestFactory();
+        using var scope = factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var svc = new GameConfigService(db, new ConfigurationBuilder().Build());
+
+        var cfg = svc.Get<ColosseumRoundsConfig>();
+
+        Assert.That(cfg.Rounds, Is.Empty);
+    }
+}

SVSim.UnitTests/Database/Config/ColosseumSeasonConfigTests.cs

@@ -0,0 +1,47 @@
+using System.Linq;
+using Microsoft.Extensions.Configuration;
+using Microsoft.Extensions.DependencyInjection;
+using NUnit.Framework;
+using SVSim.Database;
+using SVSim.Database.Models.Config;
+using SVSim.EmulatedEntrypoint.Services;
+using SVSim.UnitTests.Infrastructure;
+
+namespace SVSim.UnitTests.Database.Config;
+
+[TestFixture]
+public class ColosseumSeasonConfigTests
+{
+    [Test]
+    public void ShippedDefaults_emits_no_period()
+    {
+        var cfg = ColosseumSeasonConfig.ShippedDefaults();
+        Assert.That(cfg.IsColosseumPeriod, Is.False,
+            "default ship state is no event scheduled — lobby reads must render the empty payload");
+    }
+
+    [Test]
+    public void Has_ConfigSection_attribute_with_name_ColosseumSeason()
+    {
+        var attr = typeof(ColosseumSeasonConfig)
+            .GetCustomAttributes(typeof(ConfigSectionAttribute), false)
+            .Cast<ConfigSectionAttribute>()
+            .FirstOrDefault();
+        Assert.That(attr, Is.Not.Null);
+        Assert.That(attr!.Name, Is.EqualTo("ColosseumSeason"));
+    }
+
+    [Test]
+    public void Get_through_GameConfigService_round_trips_shipped_defaults()
+    {
+        using var factory = new SVSimTestFactory();
+        using var scope = factory.Services.CreateScope();
+        var db = scope.ServiceProvider.GetRequiredService<SVSimDbContext>();
+        var svc = new GameConfigService(db, new ConfigurationBuilder().Build());
+
+        var cfg = svc.Get<ColosseumSeasonConfig>();
+
+        Assert.That(cfg.IsColosseumPeriod, Is.False);
+        Assert.That(cfg.PoolCardSetIds, Is.Empty);
+    }
+}

SVSim.UnitTests/Models/GameConfigurationJsonbTests.cs

@@ -25,14 +25,14 @@ public class GameConfigurationJsonbTests
         var rows = await db.GameConfigs.AsNoTracking().ToListAsync();
         var byName = rows.ToDictionary(r => r.SectionName);
 
-        // One row per [ConfigSection]-marked POCO (13 sections today: Player, DefaultGrants,
+        // One row per [ConfigSection]-marked POCO (15 sections today: Player, DefaultGrants,
         // DefaultLoadout, Challenge, Rotation, PackRates, MyRotationSchedule, Story, ResourceConfig,
-        // Freeplay, ArenaTwoPick, Matching, CardMasterConfig).
+        // Freeplay, ArenaTwoPick, Matching, CardMasterConfig, ColosseumSeason, ColosseumRounds).
         Assert.That(byName.Keys, Is.EquivalentTo(new[]
         {
             "Player", "DefaultGrants", "DefaultLoadout", "Challenge", "Rotation", "PackRates",
             "MyRotationSchedule", "Story", "ResourceConfig", "Freeplay", "ArenaTwoPick", "Matching",
-            "CardMasterConfig",
+            "CardMasterConfig", "ColosseumSeason", "ColosseumRounds",
         }));
 
         var resources = JsonSerializer.Deserialize<ResourceConfig>(byName["ResourceConfig"].ValueJson)!;