Personal site of Soichi Hayashi — full stack software engineer.https://hayashi.in/https://hayashi.in/blog/design-your-day-to-earn-a-good-nights-sleep/https://hayashi.in/blog/design-your-day-to-earn-a-good-nights-sleep/What if sleep is not recovery for the day ahead, but the quiet goal the whole day was built to reach?Wed, 28 Jan 2026 00:00:00 GMTReflectionshttps://hayashi.in/blog/building-a-quarter-tone-tuner/https://hayashi.in/blog/building-a-quarter-tone-tuner/Why I skipped the FFT needle and built a pitch tuner around autocorrelation, parabolic interpolation, and a fading quarter-tone visualization — all client-side with the Web Audio API.Sat, 27 Dec 2025 00:00:00 GMTEngineeringhttps://hayashi.in/blog/what-we-leave-behind/https://hayashi.in/blog/what-we-leave-behind/Some lives fade quietly; others leave a mark nobody can quite trace back to its source. Maybe that is the only kind of permanence any of us gets.Wed, 17 Dec 2025 00:00:00 GMTReflectionshttps://hayashi.in/blog/can-an-ai-teach-itself/https://hayashi.in/blog/can-an-ai-teach-itself/A sketch for a self-directed learning loop: let an agent propose its own tasks, judge its own results, and only ask for help when it genuinely gets stuck.Sun, 23 Nov 2025 00:00:00 GMTEngineeringhttps://hayashi.in/blog/the-obligation-of-the-fortunate/https://hayashi.in/blog/the-obligation-of-the-fortunate/If health, wealth, and understanding are all things we can share, maybe they all carry the same quiet obligation once we have more than we need.Sun, 19 Oct 2025 00:00:00 GMTSocietyhttps://hayashi.in/blog/running-open-source-llms-on-your-own-machine/https://hayashi.in/blog/running-open-source-llms-on-your-own-machine/A quick recipe for standing up a local Python environment and running quantized open-weight models like Gemma with nothing but a consumer GPU.Sat, 05 Jul 2025 00:00:00 GMTEngineeringhttps://hayashi.in/blog/what-the-market-actually-prices-in/https://hayashi.in/blog/what-the-market-actually-prices-in/A pattern you can spot on a chart is a pattern already priced in. Real market inefficiencies exist, but harvesting them takes more than a hunch.Sat, 03 May 2025 00:00:00 GMTFinance