PSI-COMMIT lets you seal a prediction or decision and prove you made it before the outcome — no third party required. Your message is locked with HMAC-SHA256 and a secret key that never leaves your browser. The commitment is anchored to Bitcoin via OpenTimestamps for a permanent, tamper-proof timestamp. Save your .psc, .stamp.txt, and .ots files and your proof is self-contained forever. Free, open source, MIT licensed.​​​​