Novelly

Software for planning and writing a novel. You outline the book, keep character dossiers, break chapters into scenes, and draft prose — with a Claude-powered agent embedded in the app that can read and edit the same data you can, and an MCP server that exposes that data to Claude Code, Claude Desktop, or any other MCP client.

The point of the three-way arrangement is that there is exactly one source of truth. The React UI, the embedded agent, and the MCP server all go through the same REST API, so an edit made from a chat in Claude Code and an edit made by typing in the browser are the same edit.

Stack

Piece	Built with
Novelly.Api	ASP.NET Core 10 minimal APIs, EF Core 10 + SQLite, Anthropic SDK, OpenAPI
Novelly.AppHost	.NET Aspire orchestration for the API and the web client
Novelly.ServiceDefaults	Shared OpenTelemetry, health checks and service discovery
Novelly.Mcp	MCP stdio server (ModelContextProtocol)
Novelly.Web	React 19, TypeScript, Vite, TanStack Query, Tailwind v4

The back end is one project organised by feature, not by layer. Each feature folder — Projects/, Characters/, Chapters/, Beats/, Scenes/, Tags/, Agent/ — holds its entity, DTOs, service and endpoints together, so adding a capability means touching one folder rather than four. Common/ holds what genuinely crosses features and Data/ holds the DbContext and migrations.

Running it

Prerequisites: .NET 10 SDK and Node 20+.

Everything at once, through Aspire:

cd src/Novelly.Web && npm install && cd -
dotnet run --project src/Novelly.AppHost

That starts the API on :5080 and the Vite dev server on :5173, and opens the Aspire dashboard for logs, traces and metrics across both.

Or run the two halves separately:

# 1. API — creates and migrates novel.db on first run, listens on :5080
ASPNETCORE_URLS=http://localhost:5080 dotnet run --project src/Novelly.Api

# 2. Web — dev server on :5173, proxies /api to :5080
cd src/Novelly.Web && npm install && npm run dev

Open http://localhost:5173.

The app is fully usable without an Anthropic key — only the Agent tab needs one. To turn the agent on:

export ANTHROPIC_API_KEY=sk-ant-...

Without it, agent endpoints return 503 Agent unavailable with an explanatory message and everything else keeps working.

Tests

dotnet test                             # 44 tests
cd src/Novelly.Web && npm run build     # typecheck + bundle

git push runs both through a Husky pre-push hook (scripts/ci/prepush.sh). Install the hook once with npm install at the repo root.

Tests run against real in-memory SQLite rather than the EF in-memory provider, so they exercise the cascade deletes and query translation the app actually ships with.

Configuration

src/Novelly.Api/appsettings.json:

{
  "ConnectionStrings": { "Novel": "Data Source=novel.db" },
  "Cors": { "Origins": [ "http://localhost:5173" ] },
  "Agent": {
    "Model": "claude-opus-5",
    "MaxTokens": 16000,
    "Effort": "high",        // low | medium | high | max
    "MaxIterations": 12      // tool-call ceiling per user turn
  }
}

The API key is read from ANTHROPIC_API_KEY or, if you prefer, Agent:ApiKey — keep it out of appsettings.json and use user-secrets or the environment.

The data model

Project ──┬── Character ── CharacterRelationship
          ├── Chapter ──┬── Beat   (the outline: flat, ordered)
          │             └── Scene  (the prose)
          ├── Tag  (applied to characters, chapters and beats)
          └── AgentConversation ── AgentMessage

A chapter outline is a paragraph plus a table. The paragraph is the chapter's Summary; the table is its beats. Each beat is one row:

Column	What goes in it
Beat	A three-to-five word handle — "she burns the atlas", not a sentence
Character	Whose beat it is. Optional; not every beat belongs to one person
What happened	The event itself
What's next	What it sets in motion — the hook into the following beat
Scene	Optional grouping: which scene will carry this beat's prose

Beats are flat and ordered by SortOrder within their chapter. There is no nesting and no tree — reordering is one call that takes the beat ids in the order wanted.

Beats plan; scenes carry prose. The two layers are deliberately separate: an outline is for working out what happens, and a scene is where you write it. A beat's SceneId is the optional link between them, and it is nullable in both directions — deleting a scene ungroups its beats rather than deleting the plan.

Tags cross-reference the book. A tag is scoped to one project, unique by name (case-insensitively), and can be attached to any character, chapter or beat. Applying an unknown tag by name creates it, so tagging is one action rather than two. GET /api/tags/{id}/references returns everything carrying a tag, which is how you trace a motif or a thread across all three kinds at once.

The embedded agent

NovelAgentService runs the tool-use loop: it calls the Messages API, executes any tools Claude asks for, feeds every result back in a single user turn, and repeats until Claude stops asking. It has 18 tools covering the brief, characters, chapter outlines (beats), scenes and tags — all of them going through the same application services the REST API uses.

A few deliberate choices worth knowing about:

• Conversation history replays as text only. Tool calls are not replayed into the transcript. The agent re-reads current state through its tools instead, which is more reliable than trusting a record of edits that may since have changed in the UI.
• The user's turn is persisted before the loop runs, so a question is recorded even if the model call fails.
• Tool failures come back as is_error results, not exceptions — the model reads the message and corrects itself.
• MaxIterations caps tool calls per turn. On hitting it the agent says so rather than silently truncating.
• The system prompt is cached (cache_control: ephemeral), so every turn after the first reads it back at a fraction of the input price.

The MCP server

A stdio MCP server exposing 26 tools over the same REST API. It holds no domain logic of its own — it is a second front end, not a second implementation.

Build it, then point your MCP client at the produced binary:

dotnet publish src/Novelly.Mcp -c Release -o ./mcp-server

.mcp.json (or Claude Desktop's config):

{
  "mcpServers": {
    "novelly": {
      "command": "/absolute/path/to/mcp-server/Novelly.Mcp",
      "env": { "NOVELLY_API_URL": "http://localhost:5080" }
    }
  }
}

The API must be running. If it is not, the tools say so in a message the model can act on rather than failing opaquely.

API surface

GET /api/health, plus:

Resource	Routes
Projects	GET|POST /api/projects, GET|PATCH|DELETE /api/projects/{id}
Characters	GET|POST /api/projects/{id}/characters, GET|PATCH|DELETE /api/characters/{id}, POST /api/characters/{id}/relationships
Chapters	GET|POST /api/projects/{id}/chapters, GET|PATCH|DELETE /api/chapters/{id}
Beats	GET|POST /api/chapters/{id}/beats, POST /api/chapters/{id}/beats/reorder, GET|PATCH|DELETE /api/beats/{id}
Scenes	GET|POST /api/chapters/{id}/scenes, GET|PATCH|DELETE /api/scenes/{id}
Tags	GET|POST /api/projects/{id}/tags, GET /api/tags/{id}/references, PATCH|DELETE /api/tags/{id}
Agent	GET /api/projects/{id}/agent/conversations, POST /api/projects/{id}/agent/messages, GET|DELETE /api/conversations/{id}

PATCH bodies are partial: an omitted field is left alone, an empty string clears it. A tags array replaces that item's tags outright and creates any names the project has not seen; omitting it leaves tags untouched. Enums travel as names ("Protagonist", "Drafted"), never ordinals. In development the OpenAPI document is at /openapi/v1.json.

Known issues

• react-router-dom 7.18.2 carries GHSA-qwww-vcr4-c8h2 (CSRF bypass in RSC mode). No patched release exists yet, and every version below the affected range carries 14 worse advisories. This app is a client-only SPA and does not use RSC mode, so the advisory does not apply — but npm audit will flag it until a fix ships. Upgrade when one does.

Where this could go next

The vertical slice is complete but thin in places. The obvious next steps:

• Stream agent responses over SSE instead of returning the finished turn.
• Drag-and-drop beat reordering (the reorder endpoint is already there; the UI uses up/down buttons).
• Filter chapters and characters by tag from the list views, not just the Tags tab.
• A manuscript export (Markdown, DOCX) built from chapters and scenes in order.
• Revision history for scene prose.
• Authentication, if this is ever going to run anywhere but localhost.