Label chapter chips by kind, not raw number

Beats, tags, locations, open questions, and character/arc-stage
responses that reference a chapter now carry a ChapterLabel/DisplayNumber
alongside the raw Number, computed via the new
ChapterDisplayNumberLookup. Front/back matter chips show their title;
body chapters show "Chapter N: Title".

src/Novelly.Api/Agent/NovelAgentToolset.cs

@@ -28,6 +28,7 @@ public class NovelAgentToolset(
     CharacterService characters,
     CharacterArcService arcs,
     ChapterService chapters,
+    ChapterDisplayNumberLookup chapterLabels,
     BeatService beats,
     TagService tags,
     LocationService locations,
@@ -359,7 +360,14 @@ public class NovelAgentToolset(
             async (_, input, ct) =>
             {
                 var tagId = JsonInput.RequiredGuid(input, "tag_id");
-                return await OrNotFound(tags.GetReferencesAsync(tagId, ct), t => t.ToReferencesResponse(), "Tag", tagId);
+                var tag = await tags.GetReferencesAsync(tagId, ct);
+                if (tag is null)
+                {
+                    return new ToolNotFound("Tag", tagId);
+                }
+
+                var displayNumbers = await chapterLabels.ForNovelAsync(tag.NovelId, ct);
+                return tag.ToReferencesResponse(displayNumbers);
             });
 
         yield return new AgentTool(
@@ -378,7 +386,14 @@ public class NovelAgentToolset(
             async (_, input, ct) =>
             {
                 var locationId = JsonInput.RequiredGuid(input, "location_id");
-                return await OrNotFound(locations.GetReferencesAsync(locationId, ct), l => l.ToReferencesResponse(), "Location", locationId);
+                var location = await locations.GetReferencesAsync(locationId, ct);
+                if (location is null)
+                {
+                    return new ToolNotFound("Location", locationId);
+                }
+
+                var displayNumbers = await chapterLabels.ForNovelAsync(location.NovelId, ct);
+                return location.ToReferencesResponse(displayNumbers);
             });
 
         yield return new AgentTool(
@@ -503,14 +518,18 @@ public class NovelAgentToolset(
             new JsonSchemaBuilder()
                 .Str("character_id", "Id of the character.", required: true)
                 .Build(),
-            async (_, input, ct) =>
+            async (novelId, input, ct) =>
             {
                 var characterId = JsonInput.RequiredGuid(input, "character_id");
-                return await OrNotFound(
+                var characterBeats = await beats.ListForCharacterAsync(characterId, ct);
-                    beats.ListForCharacterAsync(characterId, ct),
+                if (characterBeats is null)
-                    list => list.Select(b => b.ToCharacterBeatResponse(characterId)),
+                {
-                    "Character",
+                    return new ToolNotFound("Character", characterId);
-                    characterId);
+                }
+
+                var displayNumbers = await chapterLabels.ForNovelAsync(novelId, ct);
+                return characterBeats.Select(b =>
+                    b.ToCharacterBeatResponse(characterId, b.Chapter is null ? null : chapterLabels.LabelFor(b.Chapter, displayNumbers)));
             });
 
         yield return new AgentTool(
@@ -600,12 +619,18 @@ public class NovelAgentToolset(
                 .Str("character_id", "Narrow to questions about one character.")
                 .Bool("include_resolved", "Include questions already settled. Defaults to false.")
                 .Build(),
-            async (novelId, input, ct) => (await questions.ListAsync(
+            async (novelId, input, ct) =>
+            {
+                var list = await questions.ListAsync(
                     novelId,
                     JsonInput.Guid(input, "chapter_id"),
                     JsonInput.Guid(input, "character_id"),
                     JsonInput.Bool(input, "include_resolved") ?? false,
-                ct)).Select(q => q.ToResponse()));
+                    ct);
+
+                var displayNumbers = await chapterLabels.ForNovelAsync(novelId, ct);
+                return list.Select(q => q.ToResponse(displayNumbers));
+            });
 
         yield return new AgentTool(
             "raise_open_question",
@@ -618,13 +643,24 @@ public class NovelAgentToolset(
                 .Str("chapter_id", "The chapter outline this is about, if any.")
                 .Str("character_id", "The character this is about, if any.")
                 .Build(),
-            async (novelId, input, ct) => await OrNotFound(questions.CreateAsync(
+            async (novelId, input, ct) =>
+            {
+                var question = await questions.CreateAsync(
                     novelId,
                     new CreateOpenQuestionRequest(
                         JsonInput.RequiredString(input, "question"),
                         JsonInput.String(input, "detail"),
                         JsonInput.Guid(input, "chapter_id"),
-                    JsonInput.Guid(input, "character_id")), ct), q => q.ToResponse(), "Novel", novelId));
+                        JsonInput.Guid(input, "character_id")), ct);
+
+                if (question is null)
+                {
+                    return new ToolNotFound("Novel", novelId);
+                }
+
+                var displayNumbers = await chapterLabels.ForNovelAsync(novelId, ct);
+                return question.ToResponse(displayNumbers);
+            });
 
         yield return new AgentTool(
             "resolve_open_question",
@@ -638,11 +674,19 @@ public class NovelAgentToolset(
             async (_, input, ct) =>
             {
                 var questionId = JsonInput.RequiredGuid(input, "question_id");
-                return await OrNotFound(questions.ResolveAsync(
+                var question = await questions.ResolveAsync(
                     questionId,
                     new ResolveOpenQuestionRequest(
                         JsonInput.RequiredString(input, "resolution"),
-                        JsonInput.Bool(input, "append_to_notes") ?? false), ct), q => q.ToResponse(), "OpenQuestion", questionId);
+                        JsonInput.Bool(input, "append_to_notes") ?? false), ct);
+
+                if (question is null)
+                {
+                    return new ToolNotFound("OpenQuestion", questionId);
+                }
+
+                var displayNumbers = await chapterLabels.ForNovelAsync(question.NovelId, ct);
+                return question.ToResponse(displayNumbers);
             });
 
         yield return new AgentTool(
@@ -654,7 +698,14 @@ public class NovelAgentToolset(
             async (_, input, ct) =>
             {
                 var questionId = JsonInput.RequiredGuid(input, "question_id");
-                return await OrNotFound(questions.ReopenAsync(questionId, ct), q => q.ToResponse(), "OpenQuestion", questionId);
+                var question = await questions.ReopenAsync(questionId, ct);
+                if (question is null)
+                {
+                    return new ToolNotFound("OpenQuestion", questionId);
+                }
+
+                var displayNumbers = await chapterLabels.ForNovelAsync(question.NovelId, ct);
+                return question.ToResponse(displayNumbers);
             });
 
         yield return new AgentTool(

src/Novelly.Api/Beats/BeatContracts.cs

@@ -81,6 +81,7 @@ public record CharacterBeatResponse(
     Guid ChapterId,
     int ChapterNumber,
     string ChapterTitle,
+    string ChapterLabel,
     int SortOrder,
     string Title,
     string? WhatHappened,
@@ -151,11 +152,12 @@ public static class BeatMapping
         [.. b.Tags.OrderBy(t => t.Name).Select(t => t.ToResponse())],
         b.UpdatedAt);
 
-    public static CharacterBeatResponse ToCharacterBeatResponse(this Beat b, Guid characterId) => new(
+    public static CharacterBeatResponse ToCharacterBeatResponse(this Beat b, Guid characterId, string? chapterLabel = null) => new(
         b.Id,
         b.ChapterId,
         b.Chapter?.Number ?? 0,
         b.Chapter?.Title ?? "(unknown chapter)",
+        chapterLabel ?? b.Chapter?.Title ?? "(unknown chapter)",
         b.SortOrder,
         b.Title,
         b.WhatHappened,

src/Novelly.Api/Beats/BeatEndpoints.cs

@@ -1,3 +1,4 @@
+using Novelly.Api.Chapters;
 using Novelly.Api.Common;
 using Novelly.Api.Common.Validation;
 
@@ -45,8 +46,21 @@ public static class BeatEndpoints
             .WithSummary("Move one or more beats to another chapter, appending them to its end.");
 
         app.MapGet("/api/characters/{characterId:guid}/beats", async (
-                Guid characterId, BeatService service, CancellationToken ct) =>
+                Guid characterId, BeatService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.ListForCharacterAsync(characterId, ct))?.Select(b => b.ToCharacterBeatResponse(characterId)).ToList().ToApiResult())
+            {
+                var characterBeats = await service.ListForCharacterAsync(characterId, ct);
+                if (characterBeats is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = characterBeats.Count > 0
+                    ? await chapterLabels.ForNovelAsync(characterBeats[0].Chapter!.NovelId, ct)
+                    : new Dictionary<Guid, int>();
+
+                return Results.Ok(characterBeats.Select(b =>
+                    b.ToCharacterBeatResponse(characterId, b.Chapter is null ? null : chapterLabels.LabelFor(b.Chapter, displayNumbers))).ToList());
+            })
             .WithTags("Beats")
             .WithSummary("Every beat this character appears in, in manuscript order.");
 

src/Novelly.Api/Chapters/ChapterDisplayNumberLookup.cs

@@ -0,0 +1,38 @@
+using Microsoft.EntityFrameworkCore;
+using Novelly.Api.Data;
+
+namespace Novelly.Api.Chapters;
+
+public class ChapterDisplayNumberLookup(INovelDbContext db)
+{
+    public async Task<IReadOnlyDictionary<Guid, int>> ForNovelAsync(Guid novelId, CancellationToken ct = default)
+    {
+        var chapters = await db.Chapters.AsNoTracking().Where(c => c.NovelId == novelId).ToListAsync(ct);
+        return ChapterNumbering.DisplayNumbers(chapters);
+    }
+
+    public async Task<int?> ForChapterAsync(Chapter chapter, CancellationToken ct = default)
+    {
+        if (chapter.Kind != ChapterKind.Body)
+            return null;
+
+        return await db.Chapters.CountAsync(
+            c => c.NovelId == chapter.NovelId && c.Kind == ChapterKind.Body && c.Number <= chapter.Number, ct);
+    }
+
+    public async Task<IReadOnlyDictionary<Guid, int>> ForChaptersAsync(IEnumerable<Chapter> chapters, CancellationToken ct = default)
+    {
+        var displayNumbers = new Dictionary<Guid, int>();
+
+        foreach (var chapter in chapters.DistinctBy(c => c.Id))
+        {
+            if (await ForChapterAsync(chapter, ct) is { } number)
+                displayNumbers[chapter.Id] = number;
+        }
+
+        return displayNumbers;
+    }
+
+    public string LabelFor(Chapter chapter, IReadOnlyDictionary<Guid, int> displayNumbers) =>
+        ChapterNumbering.Label(chapter.Kind, displayNumbers.TryGetValue(chapter.Id, out var n) ? n : null, chapter.Title);
+}

src/Novelly.Api/Chapters/ChapterService.cs

@@ -14,6 +14,7 @@ public class ChapterService(
     NovelAccessService access,
     TagService tags,
     LocationService locations,
+    ChapterDisplayNumberLookup displayNumbers,
     ActivityLog activity,
     ILogger<ChapterService> logger,
     IModelValidator<CreateChapterRequest> createValidator,
@@ -168,14 +169,8 @@ public class ChapterService(
         return true;
     }
 
-    public async Task<int?> DisplayNumberAsync(Chapter chapter, CancellationToken ct = default)
+    public Task<int?> DisplayNumberAsync(Chapter chapter, CancellationToken ct = default) =>
-    {
+        displayNumbers.ForChapterAsync(chapter, ct);
-        if (chapter.Kind != ChapterKind.Body)
-            return null;
-
-        return await db.Chapters.CountAsync(
-            c => c.NovelId == chapter.NovelId && c.Kind == ChapterKind.Body && c.Number <= chapter.Number, ct);
-    }
 
     private async Task<int> NextChapterNumberAsync(Guid novelId, CancellationToken ct)
     {

src/Novelly.Api/Characters/CharacterContracts.cs

@@ -1,4 +1,5 @@
 using Novelly.Api.Beats;
+using Novelly.Api.Chapters;
 using Novelly.Api.Common.Validation;
 using Novelly.Api.Tags;
 
@@ -25,6 +26,7 @@ public record CharacterResponse(
     string? SameCharacterAsName,
     Guid? RevealedInChapterId,
     int? RevealedInChapterNumber,
+    string? RevealedInChapterLabel,
     string? IdentityNote,
     IReadOnlyList<CharacterIdentityResponse> OtherIdentities,
     IReadOnlyList<RelationshipResponse> Relationships,
@@ -200,6 +202,7 @@ public record ArcStageResponse(
     Guid? ChapterId,
     int? ChapterNumber,
     string? ChapterTitle,
+    string? ChapterLabel,
     IReadOnlyList<CharacterBeatResponse> Beats,
     DateTimeOffset UpdatedAt);
 
@@ -286,7 +289,7 @@ public class SetArcStageBeatsRequestValidator : IModelValidator<SetArcStageBeats
 
 public static class CharacterMapping
 {
-    public static CharacterResponse ToResponse(this Character c) => new(
+    public static CharacterResponse ToResponse(this Character c, IReadOnlyDictionary<Guid, int>? displayNumbers = null) => new(
         c.Id, c.NovelId, c.Name, c.Role, c.Importance, c.Age, c.Pronouns, c.Occupation,
         c.Appearance, c.Personality, c.Backstory, c.Motivation, c.Conflict, c.Voice, c.Notes,
         [.. c.Aliases],
@@ -294,6 +297,7 @@ public static class CharacterMapping
         c.SameCharacterAs?.Name,
         c.RevealedInChapterId,
         c.RevealedInChapter?.Number,
+        c.RevealedInChapter is { } revealedInChapter ? ChapterLabel(revealedInChapter, displayNumbers) : null,
         c.IdentityNote,
         [.. c.OtherIdentities.OrderBy(o => o.Name).Select(o => new CharacterIdentityResponse(o.Id, o.Name))],
         [.. c.Relationships.Select(r => new RelationshipResponse(
@@ -303,10 +307,10 @@ public static class CharacterMapping
             r.RelationshipType,
             r.Description))],
         [.. c.Tags.OrderBy(t => t.Name).Select(t => t.ToResponse())],
-        [.. c.ArcStages.OrderBy(s => s.SortOrder).Select(s => s.ToResponse())],
+        [.. c.ArcStages.OrderBy(s => s.SortOrder).Select(s => s.ToResponse(displayNumbers))],
         c.UpdatedAt);
 
-    public static ArcStageResponse ToResponse(this CharacterArcStage s) => new(
+    public static ArcStageResponse ToResponse(this CharacterArcStage s, IReadOnlyDictionary<Guid, int>? displayNumbers = null) => new(
         s.Id,
         s.CharacterId,
         s.SortOrder,
@@ -315,9 +319,13 @@ public static class CharacterMapping
         s.ChapterId,
         s.Chapter?.Number,
         s.Chapter?.Title,
+        s.Chapter is { } chapter ? ChapterLabel(chapter, displayNumbers) : null,
         [.. s.Beats
             .OrderBy(b => b.Chapter?.Number ?? 0)
             .ThenBy(b => b.SortOrder)
-            .Select(b => b.ToCharacterBeatResponse(s.CharacterId))],
+            .Select(b => b.ToCharacterBeatResponse(s.CharacterId, b.Chapter is { } beatChapter ? ChapterLabel(beatChapter, displayNumbers) : null))],
         s.UpdatedAt);
+
+    private static string ChapterLabel(Chapter chapter, IReadOnlyDictionary<Guid, int>? displayNumbers) =>
+        ChapterNumbering.Label(chapter.Kind, displayNumbers is not null && displayNumbers.TryGetValue(chapter.Id, out var n) ? n : null, chapter.Title);
 }

src/Novelly.Api/Characters/CharacterEndpoints.cs

@@ -1,3 +1,4 @@
+using Novelly.Api.Chapters;
 using Novelly.Api.Common;
 using Novelly.Api.Common.Validation;
 
@@ -5,18 +6,57 @@ namespace Novelly.Api.Characters;
 
 public static class CharacterEndpoints
 {
+    private static IEnumerable<Chapter> ChaptersOf(Character c)
+    {
+        if (c.RevealedInChapter is { } revealed)
+        {
+            yield return revealed;
+        }
+
+        foreach (var chapter in c.ArcStages.SelectMany(ChaptersOf))
+        {
+            yield return chapter;
+        }
+    }
+
+    private static IEnumerable<Chapter> ChaptersOf(CharacterArcStage stage)
+    {
+        if (stage.Chapter is { } chapter)
+        {
+            yield return chapter;
+        }
+
+        foreach (var beat in stage.Beats)
+        {
+            if (beat.Chapter is { } beatChapter)
+            {
+                yield return beatChapter;
+            }
+        }
+    }
+
     public static IEndpointRouteBuilder MapCharacterEndpoints(this IEndpointRouteBuilder app)
     {
         var novelScoped = app.MapGroup("/api/novels/{novelId:guid}/characters").WithTags("Characters")
             .AddEndpointFilter<RequestLoggingEndpointFilter>()
             .AddEndpointFilter<ValidationEndpointFilter>();
 
-        novelScoped.MapGet("/", async (Guid novelId, CharacterService service, CancellationToken ct) =>
+        novelScoped.MapGet("/", async (Guid novelId, CharacterService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                Results.Ok((await service.ListAsync(novelId, ct)).Select(c => c.ToResponse())))
+            {
+                var list = await service.ListAsync(novelId, ct);
+                var responses = new List<CharacterResponse>();
+                foreach (var character in list)
+                {
+                    var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(character), ct);
+                    responses.Add(character.ToResponse(displayNumbers));
+                }
+
+                return Results.Ok(responses);
+            })
             .WithSummary("List a novel's character dossiers.");
 
         novelScoped.MapPost("/", async (
-                Guid novelId, CreateCharacterRequest request, CharacterService service, CancellationToken ct) =>
+                Guid novelId, CreateCharacterRequest request, CharacterService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
             {
                 var character = await service.CreateAsync(novelId, request, ct);
                 if (character is null)
@@ -24,7 +64,8 @@ public static class CharacterEndpoints
                     return Results.NotFound();
                 }
 
-                var created = character.ToResponse();
+                var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(character), ct);
+                var created = character.ToResponse(displayNumbers);
                 return Results.Created($"/api/characters/{created.Id}", created);
             })
             .WithSummary("Add a character dossier.");
@@ -33,13 +74,31 @@ public static class CharacterEndpoints
             .AddEndpointFilter<RequestLoggingEndpointFilter>()
             .AddEndpointFilter<ValidationEndpointFilter>();
 
-        characters.MapGet("/{id:guid}", async (Guid id, CharacterService service, CancellationToken ct) =>
+        characters.MapGet("/{id:guid}", async (Guid id, CharacterService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.GetAsync(id, ct))?.ToResponse().ToApiResult())
+            {
+                var character = await service.GetAsync(id, ct);
+                if (character is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(character), ct);
+                return character.ToResponse(displayNumbers).ToApiResult();
+            })
             .WithSummary("Read a character dossier.");
 
         characters.MapPatch("/{id:guid}", async (
-                Guid id, UpdateCharacterRequest request, CharacterService service, CancellationToken ct) =>
+                Guid id, UpdateCharacterRequest request, CharacterService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.UpdateAsync(id, request, ct))?.ToResponse().ToApiResult())
+            {
+                var character = await service.UpdateAsync(id, request, ct);
+                if (character is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(character), ct);
+                return character.ToResponse(displayNumbers).ToApiResult();
+            })
             .WithSummary("Update a character dossier.");
 
         characters.MapDelete("/{id:guid}", async (Guid id, CharacterService service, CancellationToken ct) =>
@@ -47,8 +106,17 @@ public static class CharacterEndpoints
             .WithSummary("Delete a character.");
 
         characters.MapPost("/{id:guid}/relationships", async (
-                Guid id, CreateRelationshipRequest request, CharacterService service, CancellationToken ct) =>
+                Guid id, CreateRelationshipRequest request, CharacterService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.AddRelationshipAsync(id, request, ct))?.ToResponse().ToApiResult())
+            {
+                var character = await service.AddRelationshipAsync(id, request, ct);
+                if (character is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(character), ct);
+                return character.ToResponse(displayNumbers).ToApiResult();
+            })
             .WithSummary("Relate this character to another in the same novel.");
 
         characters.MapDelete("/relationships/{relationshipId:guid}", async (
@@ -57,8 +125,17 @@ public static class CharacterEndpoints
             .WithSummary("Remove a relationship.");
 
         characters.MapPut("/{id:guid}/identity", async (
-                Guid id, LinkCharacterIdentityRequest request, CharacterService service, CancellationToken ct) =>
+                Guid id, LinkCharacterIdentityRequest request, CharacterService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.LinkIdentityAsync(id, request, ct))?.ToResponse().ToApiResult())
+            {
+                var character = await service.LinkIdentityAsync(id, request, ct);
+                if (character is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(character), ct);
+                return character.ToResponse(displayNumbers).ToApiResult();
+            })
             .WithSummary("Link this character as another identity of a character in the same novel.");
 
         characters.MapDelete("/{id:guid}/identity", async (
@@ -67,12 +144,22 @@ public static class CharacterEndpoints
             .WithSummary("Remove this character's identity link.");
 
         characters.MapGet("/{id:guid}/arc", async (
-                Guid id, CharacterArcService service, CancellationToken ct) =>
+                Guid id, CharacterArcService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                Results.Ok((await service.ListAsync(id, ct)).Select(s => s.ToResponse())))
+            {
+                var stages = await service.ListAsync(id, ct);
+                var responses = new List<ArcStageResponse>();
+                foreach (var stage in stages)
+                {
+                    var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(stage), ct);
+                    responses.Add(stage.ToResponse(displayNumbers));
+                }
+
+                return Results.Ok(responses);
+            })
             .WithSummary("Read a character's arc: its stages, in order.");
 
         characters.MapPost("/{id:guid}/arc", async (
-                Guid id, CreateArcStageRequest request, CharacterArcService service, CancellationToken ct) =>
+                Guid id, CreateArcStageRequest request, CharacterArcService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
             {
                 var stage = await service.CreateAsync(id, request, ct);
                 if (stage is null)
@@ -80,27 +167,61 @@ public static class CharacterEndpoints
                     return Results.NotFound();
                 }
 
-                var created = stage.ToResponse();
+                var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(stage), ct);
+                var created = stage.ToResponse(displayNumbers);
                 return Results.Created($"/api/arc-stages/{created.Id}", created);
             })
             .WithSummary("Add a stage to a character's arc.");
 
         characters.MapPost("/{id:guid}/arc/reorder", async (
-                Guid id, ReorderArcStagesRequest request, CharacterArcService service, CancellationToken ct) =>
+                Guid id, ReorderArcStagesRequest request, CharacterArcService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.ReorderAsync(id, request, ct))?.Select(s => s.ToResponse()).ToList().ToApiResult())
+            {
+                var stages = await service.ReorderAsync(id, request, ct);
+                if (stages is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var responses = new List<ArcStageResponse>();
+                foreach (var stage in stages)
+                {
+                    var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(stage), ct);
+                    responses.Add(stage.ToResponse(displayNumbers));
+                }
+
+                return Results.Ok(responses);
+            })
             .WithSummary("Renumber a character's arc to match the order given.");
 
         var arcStages = app.MapGroup("/api/arc-stages").WithTags("Characters")
             .AddEndpointFilter<RequestLoggingEndpointFilter>()
             .AddEndpointFilter<ValidationEndpointFilter>();
 
-        arcStages.MapGet("/{id:guid}", async (Guid id, CharacterArcService service, CancellationToken ct) =>
+        arcStages.MapGet("/{id:guid}", async (Guid id, CharacterArcService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.GetAsync(id, ct))?.ToResponse().ToApiResult())
+            {
+                var stage = await service.GetAsync(id, ct);
+                if (stage is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(stage), ct);
+                return stage.ToResponse(displayNumbers).ToApiResult();
+            })
             .WithSummary("Read one arc stage.");
 
         arcStages.MapPatch("/{id:guid}", async (
-                Guid id, UpdateArcStageRequest request, CharacterArcService service, CancellationToken ct) =>
+                Guid id, UpdateArcStageRequest request, CharacterArcService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.UpdateAsync(id, request, ct))?.ToResponse().ToApiResult())
+            {
+                var stage = await service.UpdateAsync(id, request, ct);
+                if (stage is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(stage), ct);
+                return stage.ToResponse(displayNumbers).ToApiResult();
+            })
             .WithSummary("Update an arc stage.");
 
         arcStages.MapDelete("/{id:guid}", async (Guid id, CharacterArcService service, CancellationToken ct) =>
@@ -108,8 +229,17 @@ public static class CharacterEndpoints
             .WithSummary("Delete an arc stage.");
 
         arcStages.MapPost("/{id:guid}/beats", async (
-                Guid id, SetArcStageBeatsRequest request, CharacterArcService service, CancellationToken ct) =>
+                Guid id, SetArcStageBeatsRequest request, CharacterArcService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.SetBeatsAsync(id, request, ct))?.ToResponse().ToApiResult())
+            {
+                var stage = await service.SetBeatsAsync(id, request, ct);
+                if (stage is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = await chapterLabels.ForChaptersAsync(ChaptersOf(stage), ct);
+                return stage.ToResponse(displayNumbers).ToApiResult();
+            })
             .WithSummary("Set which beats belong to this arc stage, replacing its current set. "
                          + "A beat moved into this stage leaves any other stage of the same character it was in.");
 

src/Novelly.Api/Common/NovellyServiceRegistration.cs

@@ -86,6 +86,7 @@ public static class NovellyServiceRegistration
         services.AddScoped<LocationService>();
         services.AddScoped<GenreService>();
         services.AddScoped<ChapterService>();
+        services.AddScoped<ChapterDisplayNumberLookup>();
         services.AddScoped<OpenQuestionService>();
         services.AddScoped<NovelAgentToolset>();
         services.AddScoped<NovelAgentService>();

src/Novelly.Api/Locations/LocationContracts.cs

@@ -1,3 +1,4 @@
+using Novelly.Api.Chapters;
 using Novelly.Api.Common.Validation;
 
 namespace Novelly.Api.Locations;
@@ -36,17 +37,20 @@ public class UpdateLocationRequestValidator : IModelValidator<UpdateLocationRequ
 
 public record LocationReferencesResponse(LocationResponse Location, IReadOnlyList<LocatedChapterResponse> Chapters);
 
-public record LocatedChapterResponse(Guid Id, int Number, string Title, string? Summary);
+public record LocatedChapterResponse(Guid Id, int Number, ChapterKind Kind, int? DisplayNumber, string Title, string? Summary);
 
 public static class LocationMapping
 {
     public static LocationResponse ToResponse(this Location l) => new(l.Id, l.Name);
 
-    public static LocationReferencesResponse ToReferencesResponse(this Location location) => new(
+    public static LocationReferencesResponse ToReferencesResponse(this Location location, IReadOnlyDictionary<Guid, int>? displayNumbers = null) => new(
         location.ToResponse(),
         [.. location.Chapters
             .OrderBy(c => c.Number)
-            .Select(c => new LocatedChapterResponse(c.Id, c.Number, c.Title, c.Summary))]);
+            .Select(c => new LocatedChapterResponse(
+                c.Id, c.Number, c.Kind,
+                displayNumbers is not null && displayNumbers.TryGetValue(c.Id, out var n) ? n : null,
+                c.Title, c.Summary))]);
 
     public static string Normalise(string name) => name.Trim();
 }

src/Novelly.Api/Locations/LocationEndpoints.cs

@@ -1,3 +1,4 @@
+using Novelly.Api.Chapters;
 using Novelly.Api.Common;
 using Novelly.Api.Common.Validation;
 
@@ -33,8 +34,17 @@ public static class LocationEndpoints
             .AddEndpointFilter<RequestLoggingEndpointFilter>()
             .AddEndpointFilter<ValidationEndpointFilter>();
 
-        locations.MapGet("/{id:guid}/references", async (Guid id, LocationService service, CancellationToken ct) =>
+        locations.MapGet("/{id:guid}/references", async (Guid id, LocationService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.GetReferencesAsync(id, ct))?.ToReferencesResponse().ToApiResult())
+            {
+                var location = await service.GetReferencesAsync(id, ct);
+                if (location is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = await chapterLabels.ForNovelAsync(location.NovelId, ct);
+                return location.ToReferencesResponse(displayNumbers).ToApiResult();
+            })
             .WithSummary("Cross-reference: every chapter set at this location.");
 
         locations.MapPatch("/{id:guid}", async (

src/Novelly.Api/Questions/OpenQuestionContracts.cs

@@ -1,3 +1,4 @@
+using Novelly.Api.Chapters;
 using Novelly.Api.Common.Validation;
 
 namespace Novelly.Api.Questions;
@@ -10,6 +11,7 @@ public record OpenQuestionResponse(
     Guid? ChapterId,
     int? ChapterNumber,
     string? ChapterTitle,
+    string? ChapterLabel,
     Guid? CharacterId,
     string? CharacterName,
     string? Resolution,
@@ -74,7 +76,7 @@ public class ResolveOpenQuestionRequestValidator : IModelValidator<ResolveOpenQu
 
 public static class OpenQuestionMapping
 {
-    public static OpenQuestionResponse ToResponse(this OpenQuestion q) => new(
+    public static OpenQuestionResponse ToResponse(this OpenQuestion q, IReadOnlyDictionary<Guid, int>? displayNumbers = null) => new(
         q.Id,
         q.NovelId,
         q.Question,
@@ -82,6 +84,9 @@ public static class OpenQuestionMapping
         q.ChapterId,
         q.Chapter?.Number,
         q.Chapter?.Title,
+        q.Chapter is { } chapter
+            ? ChapterNumbering.Label(chapter.Kind, displayNumbers is not null && displayNumbers.TryGetValue(chapter.Id, out var n) ? n : null, chapter.Title)
+            : null,
         q.CharacterId,
         q.Character?.Name,
         q.Resolution,

src/Novelly.Api/Questions/OpenQuestionEndpoints.cs

@@ -1,3 +1,4 @@
+using Novelly.Api.Chapters;
 using Novelly.Api.Common;
 using Novelly.Api.Common.Validation;
 
@@ -14,15 +15,20 @@ public static class OpenQuestionEndpoints
         novelScoped.MapGet("/", async (
                 Guid novelId,
                 OpenQuestionService service,
+                ChapterDisplayNumberLookup chapterLabels,
                 CancellationToken ct,
                 Guid? chapterId = null,
                 Guid? characterId = null,
                 bool includeResolved = false) =>
-                Results.Ok((await service.ListAsync(novelId, chapterId, characterId, includeResolved, ct)).Select(q => q.ToResponse())))
+            {
+                var list = await service.ListAsync(novelId, chapterId, characterId, includeResolved, ct);
+                var displayNumbers = await chapterLabels.ForNovelAsync(novelId, ct);
+                return Results.Ok(list.Select(q => q.ToResponse(displayNumbers)));
+            })
             .WithSummary("List a novel's open questions, optionally narrowed to one chapter or character.");
 
         novelScoped.MapPost("/", async (
-                Guid novelId, CreateOpenQuestionRequest request, OpenQuestionService service, CancellationToken ct) =>
+                Guid novelId, CreateOpenQuestionRequest request, OpenQuestionService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
             {
                 var question = await service.CreateAsync(novelId, request, ct);
                 if (question is null)
@@ -30,7 +36,8 @@ public static class OpenQuestionEndpoints
                     return Results.NotFound();
                 }
 
-                var created = question.ToResponse();
+                var displayNumbers = await chapterLabels.ForNovelAsync(novelId, ct);
+                var created = question.ToResponse(displayNumbers);
                 return Results.Created($"/api/questions/{created.Id}", created);
             })
             .WithSummary("Raise an open question, optionally against a chapter outline and/or a character.");
@@ -39,22 +46,22 @@ public static class OpenQuestionEndpoints
             .AddEndpointFilter<RequestLoggingEndpointFilter>()
             .AddEndpointFilter<ValidationEndpointFilter>();
 
-        questions.MapGet("/{id:guid}", async (Guid id, OpenQuestionService service, CancellationToken ct) =>
+        questions.MapGet("/{id:guid}", async (Guid id, OpenQuestionService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.GetAsync(id, ct))?.ToResponse().ToApiResult())
+                await WithLabel(await service.GetAsync(id, ct), chapterLabels, ct))
             .WithSummary("Read one question.");
 
         questions.MapPatch("/{id:guid}", async (
-                Guid id, UpdateOpenQuestionRequest request, OpenQuestionService service, CancellationToken ct) =>
+                Guid id, UpdateOpenQuestionRequest request, OpenQuestionService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.UpdateAsync(id, request, ct))?.ToResponse().ToApiResult())
+                await WithLabel(await service.UpdateAsync(id, request, ct), chapterLabels, ct))
             .WithSummary("Update a question or change what it is attached to.");
 
         questions.MapPost("/{id:guid}/resolve", async (
-                Guid id, ResolveOpenQuestionRequest request, OpenQuestionService service, CancellationToken ct) =>
+                Guid id, ResolveOpenQuestionRequest request, OpenQuestionService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.ResolveAsync(id, request, ct))?.ToResponse().ToApiResult())
+                await WithLabel(await service.ResolveAsync(id, request, ct), chapterLabels, ct))
             .WithSummary("Settle a question, optionally appending the resolution to the notes it hangs off.");
 
-        questions.MapPost("/{id:guid}/reopen", async (Guid id, OpenQuestionService service, CancellationToken ct) =>
+        questions.MapPost("/{id:guid}/reopen", async (Guid id, OpenQuestionService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.ReopenAsync(id, ct))?.ToResponse().ToApiResult())
+                await WithLabel(await service.ReopenAsync(id, ct), chapterLabels, ct))
             .WithSummary("Put a resolved question back on the list.");
 
         questions.MapDelete("/{id:guid}", async (Guid id, OpenQuestionService service, CancellationToken ct) =>
@@ -63,4 +70,15 @@ public static class OpenQuestionEndpoints
 
         return app;
     }
+
+    private static async Task<IResult> WithLabel(OpenQuestion? question, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct)
+    {
+        if (question is null)
+        {
+            return Results.NotFound();
+        }
+
+        var displayNumbers = await chapterLabels.ForNovelAsync(question.NovelId, ct);
+        return Results.Ok(question.ToResponse(displayNumbers));
+    }
 }

src/Novelly.Api/Tags/TagContracts.cs

@@ -1,3 +1,4 @@
+using Novelly.Api.Chapters;
 using Novelly.Api.Common.Validation;
 
 namespace Novelly.Api.Tags;
@@ -53,13 +54,14 @@ public record TagReferencesResponse(
 
 public record TaggedCharacterResponse(Guid Id, string Name, string Role);
 
-public record TaggedChapterResponse(Guid Id, int Number, string Title, string? Summary);
+public record TaggedChapterResponse(Guid Id, int Number, ChapterKind Kind, int? DisplayNumber, string Title, string? Summary);
 
 public record TaggedBeatResponse(
     Guid Id,
     Guid ChapterId,
     int ChapterNumber,
     string ChapterTitle,
+    string ChapterLabel,
     int SortOrder,
     string Title,
     string? CharacterName,
@@ -69,14 +71,17 @@ public static class TagMapping
 {
     public static TagResponse ToResponse(this Tag t) => new(t.Id, t.Name, t.Color);
 
-    public static TagReferencesResponse ToReferencesResponse(this Tag tag) => new(
+    public static TagReferencesResponse ToReferencesResponse(this Tag tag, IReadOnlyDictionary<Guid, int>? displayNumbers = null) => new(
         tag.ToResponse(),
         [.. tag.Characters
             .OrderBy(c => c.Name)
             .Select(c => new TaggedCharacterResponse(c.Id, c.Name, c.Role.ToString()))],
         [.. tag.Chapters
             .OrderBy(c => c.Number)
-            .Select(c => new TaggedChapterResponse(c.Id, c.Number, c.Title, c.Summary))],
+            .Select(c => new TaggedChapterResponse(
+                c.Id, c.Number, c.Kind,
+                displayNumbers is not null && displayNumbers.TryGetValue(c.Id, out var n) ? n : null,
+                c.Title, c.Summary))],
         [.. tag.Beats
             .OrderBy(b => b.Chapter?.Number ?? 0)
             .ThenBy(b => b.SortOrder)
@@ -85,6 +90,9 @@ public static class TagMapping
                 b.ChapterId,
                 b.Chapter?.Number ?? 0,
                 b.Chapter?.Title ?? "(unknown chapter)",
+                b.Chapter is { } chapter
+                    ? ChapterNumbering.Label(chapter.Kind, displayNumbers is not null && displayNumbers.TryGetValue(chapter.Id, out var bn) ? bn : null, chapter.Title)
+                    : "(unknown chapter)",
                 b.SortOrder,
                 b.Title,
                 b.Characters.Count > 0 ? string.Join(", ", b.Characters.OrderBy(c => c.Name).Select(c => c.Name)) : null,

src/Novelly.Api/Tags/TagEndpoints.cs

@@ -1,3 +1,4 @@
+using Novelly.Api.Chapters;
 using Novelly.Api.Common;
 using Novelly.Api.Common.Validation;
 
@@ -33,8 +34,17 @@ public static class TagEndpoints
             .AddEndpointFilter<RequestLoggingEndpointFilter>()
             .AddEndpointFilter<ValidationEndpointFilter>();
 
-        tags.MapGet("/{id:guid}/references", async (Guid id, TagService service, CancellationToken ct) =>
+        tags.MapGet("/{id:guid}/references", async (Guid id, TagService service, ChapterDisplayNumberLookup chapterLabels, CancellationToken ct) =>
-                (await service.GetReferencesAsync(id, ct))?.ToReferencesResponse().ToApiResult())
+            {
+                var tag = await service.GetReferencesAsync(id, ct);
+                if (tag is null)
+                {
+                    return Results.NotFound();
+                }
+
+                var displayNumbers = await chapterLabels.ForNovelAsync(tag.NovelId, ct);
+                return tag.ToReferencesResponse(displayNumbers).ToApiResult();
+            })
             .WithSummary("Cross-reference: every character, chapter and beat carrying this tag.");
 
         tags.MapPatch("/{id:guid}", async (

tests/Novelly.Api.Tests/ListingTests.cs

@@ -85,7 +85,7 @@ public class ListingTests : ServiceTestFixture
         var agent = new NovelAgentService(
             Db.Context,
             new ScriptedModelClient([[new AgentTextBlock("Reply.")]]),
-            new NovelAgentToolset(Novels, Characters, Arcs, Chapters, Beats, Tags, Locations, Questions, NullLogger<NovelAgentToolset>.Instance),
+            new NovelAgentToolset(Novels, Characters, Arcs, Chapters, ChapterLabels, Beats, Tags, Locations, Questions, NullLogger<NovelAgentToolset>.Instance),
             Options.Create(new AgentOptions()),
             NullLogger<NovelAgentService>.Instance,
             new SendAgentMessageRequestValidator());

tests/Novelly.Api.Tests/NovelAgentServiceTests.cs

@@ -12,7 +12,7 @@ public class NovelAgentServiceTests : ServiceTestFixture
     private NovelAgentToolset _toolset = null!;
 
     protected override void OnSetUp() =>
-        _toolset = new NovelAgentToolset(Novels, Characters, Arcs, Chapters, Beats, Tags, Locations, Questions, NullLogger<NovelAgentToolset>.Instance);
+        _toolset = new NovelAgentToolset(Novels, Characters, Arcs, Chapters, ChapterLabels, Beats, Tags, Locations, Questions, NullLogger<NovelAgentToolset>.Instance);
 
     private NovelAgentService BuildAgent(ScriptedModelClient model) => new(
         Db.Context,

tests/Novelly.Api.Tests/ServiceTestFixture.cs

@@ -23,6 +23,7 @@ public abstract class ServiceTestFixture
     protected NovelService Novels { get; private set; } = null!;
     protected CharacterService Characters { get; private set; } = null!;
     protected ChapterService Chapters { get; private set; } = null!;
+    protected ChapterDisplayNumberLookup ChapterLabels { get; private set; } = null!;
     protected BeatService Beats { get; private set; } = null!;
     protected CharacterArcService Arcs { get; private set; } = null!;
     protected OpenQuestionService Questions { get; private set; } = null!;
@@ -75,7 +76,8 @@ public abstract class ServiceTestFixture
             Db.Context, Access, Tags, ActivityLog, CharacterLogs,
             new CreateCharacterRequestValidator(), new UpdateCharacterRequestValidator(), new CreateRelationshipRequestValidator(),
             new LinkCharacterIdentityRequestValidator());
-        Chapters = new ChapterService(Db.Context, Access, Tags, Locations, ActivityLog, ChapterLogs, new CreateChapterRequestValidator(), new UpdateChapterRequestValidator());
+        ChapterLabels = new ChapterDisplayNumberLookup(Db.Context);
+        Chapters = new ChapterService(Db.Context, Access, Tags, Locations, ChapterLabels, ActivityLog, ChapterLogs, new CreateChapterRequestValidator(), new UpdateChapterRequestValidator());
         Beats = new BeatService(
             Db.Context, Access, Tags, ActivityLog, BeatLogs,
             new CreateBeatRequestValidator(), new UpdateBeatRequestValidator(), new ReorderBeatsRequestValidator(),

tests/Novelly.Api.Tests/TagServiceTests.cs

@@ -103,6 +103,29 @@ public class TagServiceTests : ServiceTestFixture
         });
     }
 
+    [Test]
+    public async Task Cross_reference_labels_front_matter_by_title_not_chapter_number()
+    {
+        var foreword = await Chapters.CreateAsync(
+            _novelId, new CreateChapterRequest("Foreword", Number: 1, Kind: ChapterKind.FrontMatter, Tags: ["betrayal"]));
+        var chapter = await Chapters.CreateAsync(
+            _novelId, new CreateChapterRequest("Landfall", Number: 2, Tags: ["betrayal"]));
+
+        var tagId = (await Tags.ListAsync(_novelId)).Single().Id;
+        var tag = (await Tags.GetReferencesAsync(tagId))!;
+        var displayNumbers = await ChapterLabels.ForNovelAsync(_novelId);
+        var references = tag.ToReferencesResponse(displayNumbers);
+
+        var forewordResponse = references.Chapters.Single(c => c.Id == foreword.Id);
+        var chapterResponse = references.Chapters.Single(c => c.Id == chapter.Id);
+
+        Assert.Multiple(() =>
+        {
+            Assert.That(forewordResponse.DisplayNumber, Is.Null);
+            Assert.That(chapterResponse.DisplayNumber, Is.EqualTo(1));
+        });
+    }
+
     [Test]
     public async Task Usage_counts_are_reported_per_kind()
     {