I built a web tool to see and edit what an AI thinks before it answers
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I run a small AI lab and playground and got super excited about Anthropics paper "Verbalizable Representations Form a Global Workspace in Language Models" (https://transformer-circuits.pub/2026/workspace/index.html)It talks about how they use a tool they call a Jacobian Lens to view inside the middle layers of LLM while it's working before it commits to a word (token).I wanted to see if I could get a version of this running on the open models and to my surprise it worked! I ran some experiments with it and build a public facing free tool anyone can use with your own prompts.Ask the model to describe a symbol of "three curving lines of water" and you can watch "ocean", "sea", and "surf" light up a few layers deeper before it settles on "waves".You can also edit the internal state. Insert "fire" into the middle layer of the ocean prompt and the answer shifts to something about heat.For fun / curiosity sake, I also developed way to let the model read its own inner workspace and then decide to suppress or amplify a concept, and run the prompt again.Interesting finding from running it across models. J-lens beats a plain logit lens on some architectures and does nothing on others, and it isn't about size. A 0.5B Qwen reads better than a 2.8B Pythia. Every Pythia I tried gained basically nothing; the Llama and Qwen models gained a lot. https://lucid.earthpilot.ai/researchThis is a 48 hour old project based on emerging research and built on a small model, a small probe set on rented GPUs - but I found it genuinely exciting. The code is open.I also included a page context "Docent" AI agent you can chat with about whatever you see to help understand what is going on.Happy to have folks poke around and break it.I imagine the applications for allowing models to self-reflect / edit internal states can be useful for alignment, confidence, bias detection, etc. and this tool lets you play with the early stages of that.
HN · launched Jul 9, 2026 · 34 upvotes (top 20%) · 0 views
Niche: llm evaluation and deployment tools · 77 launches, 0 in the last 7 days · Explore this niche →
Category and tags
- Horizontal
- Observability & eval
- Developer
- AI-native
- Hobby / open-source project
Visit website ↗ Source listing ↗
More like this: all 77 launches in llm evaluation and deployment tools →
Could you build this?
Partial The retro web UI is simple to create, but running model interpretability techniques like the Jacobian Lens requires direct tensor manipulation and GPU inference infrastructure.
What it would actually take: Building this requires self-hosting open-weights LLMs with PyTorch/TransformerLens on GPU instances to extract intermediate layer activations and compute input-output gradients/Jacobians across attention blocks. The backend must expose an API streaming real-time activation vectors and projected vocabulary tokens back to the frontend canvas.
Discussion
8 comments analyzed.
Competitors mentioned: Neuronpedia (Qwen3.6-27b/jlens), Logit lens, Anthropic's original paper/tool
Concerns raised: Generated nature of site and copy suggests little thought put into it, Unclear if this approach is better than existing alternatives, J-lens effectiveness varies by architecture and may not improve on some models
Feature requests: Tools that expose internal model reasoning surface more directly, Integration of pre-answer thinking phase into models themselves
Competitors
Other products that read as similar to this one : 345 launches clear the similarity bar, closest 8 shown.
Attention rank: #88 of 346 (itself plus its competitors, highest first, normalized so YC and Product Hunt are compared fairly).
Launched 248 days after the earliest competitor.
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