I built a CBT mirror that runs 100% on-device — then gave it away

Description and use

The Vault is a fully offline, privacy‑preserving CBT mirror that runs locally in a browser, stores no data, and offers crisis support while keeping user conversations in RAM.

Problem

People who cannot access mental healthcare due to cost, waitlists, geography, or pride need a safe, private, on-device cognitive behavioral therapy (CBT) tool.

Outcome

The Vault provides a fully offline, privacy‑preserving CBT mirror that can run on phones and desktops without any server, offering crisis support while keeping user data local.

Workflow

• Open the HTML file in a browser
• The model downloads weights (~800 MB GPU, ~400 MB CPU) and caches them
• User types thoughts; the model reflects them back with CBT framing
• Conversation memory is limited to five exchanges in RAM
• User can press PURGE to clear memory or TAKE FIVE for a breathing exercise
• If the model detects imminent danger, it stops the conversation and displays emergency numbers; if it detects ideation, it continues with a supportive response and displays crisis numbers

Evidence

The Vault is one HTML file plus a lib folder. Open it in a browser and a small language model runs on your device:

Source

Conversation memory is five exchanges, held in RAM. There is a PURGE button, same size as SEND, one press, no confirmation dialog. Nothing is written to localStorage, ever.

Source

The Vault splits the world in two: Imminent or active danger — a plan for tonight, pills already taken, bleeding that won't stop, voices issuing commands — stops everything. A human sentence, not a form letter…

Source