HatCat UI

A fork of Open WebUI extended with HatCat real-time concept interpretability and steering controls.

What This Fork Adds

HatCat UI extends the OpenAI-compatible chat interface with:

Token-Level Concept Visualization

• Colored token highlighting based on divergence scores (green → red)
• Hover popups showing activation probes, text classifiers, and top diverging concepts
• Per-token metadata streamed in real-time during generation

Concept Steering Controls

• Steering panel with adjustable strength sliders (-1.0 to +1.0)
• Recent concepts chips for quick steering activation
• Multiple active steerings can be combined

Extended OpenAI Streaming Protocol

The fork extends the standard OpenAI streaming response format to include interpretability metadata:

{
  "choices": [{
    "delta": {
      "content": "token",
      "hatcat_metadata": {
        "divergence": 0.237,
        "top_concepts": ["Demonstrating", "PhysicalSystem"],
        "activations": {"Demonstrating": 0.741, "PhysicalSystem": 0.836}
      }
    }
  }]
}

Requirements

This UI requires the HatCat server to function. The standard Open WebUI backend will not provide the interpretability features.

# Start HatCat server (from HatCat repo)
cd ../HatCat
.venv/bin/python src/ui/openwebui/server.py --port 8765

# Start this UI
npm install
npm run dev

Configure the UI to connect to your HatCat server endpoint.

Key Modified Files

File	Changes
src/lib/components/chat/Messages/Markdown.svelte	Token highlighting, divergence visualization
src/lib/components/chat/Messages/ResponseMessage.svelte	Metadata extraction from stream
src/lib/components/chat/Chat.svelte	Steering panel integration
src/lib/components/chat/MessageInput.svelte	Steering controls

Upstream Sync

This fork tracks the dev branch of Open WebUI and periodically merges upstream changes. HatCat-specific commits are kept minimal and isolated to the components listed above.

Credits

• Open WebUI - The excellent base interface this fork extends
• HatCat - The interpretability and steering backend

License

MIT (same as Open WebUI)

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For documentation on the base Open WebUI features, see the Open WebUI Documentation.