otaku — an LLM frontend for roleplay

Otaku is an LLM frontend for roleplay (similar to SillyTavern, Janitor AI, etc.).

It's free, works on your machine, and lets you play either in a web UI or in the terminal. LLMs can be local (via llama.cpp, KoboldCpp, Ollama, and others) or accessed via an API service (OpenRouter, NanoGPT). Otaku needs no infrastructure — no Docker, no database server — installs in one command, and requires minimal configuration.

Demo

Demos are available on the website:

• Web UI demo: https://otaku.sh/demo-web/
• Terminal demo: https://otaku.sh/demo-terminal/

Both demos include two sample stories and a scripted "model", so you can actually send prompts and see how the UI works.

Features

Main features:

• consistent prose: the first 20 and the last 150 messages are always sent to the LLM as they are, to make it maintain the style;
• context control: as the number of messages grows, intermediate messages are split into scenes and are automatically replaced by scene summaries;
• character recognition: characters you introduce in your story are extracted automatically; each character keeps their own journal of what they've seen and experienced;
• no fixed persona: you are free to play any character during the story and hint to the LLM who is playing whom (the /me and /you commands);
• transparent context: you can see what will be sent to the LLM with the /context command.

Import your content:

• character cards — into a story you've already started (the /card command);
• SillyTavern chats — this creates a new story that you can continue (the /import command);
• a text file — will be split into turns, and you can play with the characters in it (also the /import command);
• lorebooks or world info have no equivalent in otaku, but they can be imported from a file into the system message (the /system command).

Requirements

• Platform: macOS / Linux / Windows.
• Local LLM provider(s) or an API key for cloud provider(s).

Backends and providers supported: llama.cpp, KoboldCpp, Ollama, oMLX, LM Studio; OpenRouter and NanoGPT; and any other OpenAI-compatible server through the Generic OpenAI provider, by URL and key.

Installation

The script first installs the uv package manager — if you don't have it yet — and then installs otaku with it.

macOS and Linux:

curl -LsSf https://otaku.sh/install.sh | sh

Windows:

irm https://otaku.sh/install.ps1 | iex

Other ways to install:

# directly with uv
uv tool install otaku

# alternatively, via Homebrew
brew trust enclavum/tap
brew install enclavum/tap/otaku

Updating

otaku update

The command detects how otaku was installed (uv, brew, etc.) and runs that installer's own upgrade.

User guide

Both the web UI and the terminal share the same functions; the difference is that in the terminal you execute them with slash commands (the reference is available with /help), while in the web UI the operations are available from the menu. In the description below, all commands are given as they are called from the terminal.

Launching

otaku      # for terminal
otaku web  # for web UI; default URL is http://localhost:9600

On first start, you choose a provider and a model: otaku automatically detects local LLM backends and lets you pick from their models. Cloud providers (OpenRouter, NanoGPT) are also in the picker — enter an API key and their catalogs appear — and the Generic OpenAI provider, first in the picker's panel, takes any other OpenAI-compatible server's URL and key. After you've chosen (or cancelled with Esc), you land at the prompt. The model picker is available later with the /model (Ctrl+O) command.

To give you an idea of the features and what play looks like, two sample stories are imported on first start. /stories lets you choose one or the other, and /lore, /cast, and /context show what otaku has built from each.

The command cheatsheet is available with /help.

Starting a story

From there, you can start your own story with the /new command. You can also import a SillyTavern chat with /import. Note that importing takes time, because it not only imports the messages but also extracts characters and scenes from them (more on that below), though you can cancel the extraction. You can also import a plain text file the same way; it will be split into messages.

Playing

You send messages as usual, as your persona; the LLM infers which character to play from the dialogue. There are helper commands — /you, /me, and /ooc — which only frame your prompt with minimal injections like "you play as …" (you can see and configure these templates in ~/.otaku/configs/prompts.toml).

Mid-prompt, there are also two helper commands: /ooc and /cue. Both wrap the text after them in an OOC block; the difference is that the /ooc block persists — right for a standing note to the LLM — while the /cue block is sent only once — right for one-time story steering.

A few example prompts:

• I follow the keeper deeper into the vault. — plain play
• /ooc Keep replies under three paragraphs. — out of character, a standing note
• "Who goes there?" I whisper. /ooc the keeper does not know me yet — play with an aside
• "Come away with me," I tell the keeper. /cue she refuses — play with a one-time steer
• /me Keeper: You are late again. — hint to the LLM that you are playing Keeper now
• /you Keeper — tell the LLM to play as Keeper
• /you Keeper: she is furious — the same but with a direction

For D&D roleplay, there is the /roll command: /roll 1d20+5 I search the alcove rolls the dice, shows you what fell, and sends the result together with your action; /regen re-tells the same roll rather than re-rolling it. Dice examples: 2d6+3, d20, 2d20kh1/2d20kl1.

During play, you can /undo (Ctrl+U) the last exchange and /regen (Ctrl+R) the last reply.

Importing character cards

You can import character cards into the story you are playing with the /card command, where you specify a card file to load (either PNG or JSON). The command automatically creates a character in the lore (see below), and the character greets you. The card is treated as a normal prompt — it's just that you are sending the card content as your message. The imported card can later be edited in the /cast browser, and the context will change accordingly.

Managing and forking stories

You can browse the stories you've played with the /stories (Ctrl+T) command. From the stories picker, you can choose a story to continue from any message, or fork from there to another story. You can also fork a new version of the story you are playing with the /fork command. Forking copies all scenes, characters, journals, etc. to the new branch. Note that you can edit messages in the stories picker with the e key.

Extracting summaries and lore

After you've sent around 50 messages, a summary pass starts automatically in the background once you've been idle for 5 minutes, so it doesn't disturb your roleplay. You can also run it on demand with /extract. You'll see a notification and its progress in the status bar, and you can keep playing meanwhile — replies will just be slower while it runs.

Once the extraction completes, you can browse and edit the extracted summaries and characters with the /lore and /cast commands. Summaries are editable, so you can correct them however you like.

Understanding the context

The summaries only kick in once you have more than around 200 messages in the chat. The first 20 and the last 150 messages (both configurable) are always sent as is, to preserve maximum detail of recent story development and your prose style; everything in between is replaced with scene summaries. Even though summaries may exist up to the latest message, only the older ones are actually used. Nothing is included in the context by a condition or a trigger word.

The exact context composition, case by case, is described in context_design.md. You can use the /context command to see what exactly will be sent to the LLM.

Customizing the web UI

To restyle the web UI, create ~/.otaku/web/custom.css; it overrides styles in the bundled design. The custom properties it can set are listed in docs/web_tokens.md.

Configuration and environments

Everything lives in the state dir, ~/.otaku by default:

• configs/config.toml — context shape, extraction thresholds, encryption, backups, and web settings.
• configs/providers.toml — one section per provider (URL, API key). The model picker edits it for you, and API keys are stored sealed.
• configs/prompts.toml — every template otaku ever sends, editable.
• configs/state.toml, configs/models.toml — the app's own memory of your session and per-model settings.
• web/custom.css and web/fonts/ — web UI customization, if needed.

The config files are written on first run and after that edited only surgically — line by line, never rewritten as a whole: version migrations at launch and the picker's provider edits, each keeping the pre-edit file in configs/backups/. prompts.toml migrates the same way: a template you left unedited follows a new release's built-in, and one you've edited is never touched.

Set OTAKU_CONFIG_DIR to run a completely separate environment: OTAKU_CONFIG_DIR=~/.otaku-alt otaku.

Storage and privacy

Stories live in a local SQLite database; the database is snapshotted daily into the state dir, the last seven kept (configurable).

Encryption at rest is disabled by default but is one config switch away (AES-256-GCM, sealed client-side): the key can live in your OS keychain, come from a command of your choice (a password manager, a hardware token), derive from a passphrase, or sit on disk. The request log is sealed with the same cipher.

Provider API keys are always stored sealed, their key in the OS keychain.

Details in SECURITY.md.

Contributing

See CONTRIBUTING.md — a small, focused project; contributions that keep it sharp are very welcome.

License

MIT.