https://jayesh.cv/notes Field notes on building agents: cost, safety, retrieval and the decisions behind them. en Thu, 08 Oct 2026 18:30:00 GMT https://jayesh.cv/notes/unmeasured-is-not-zero https://jayesh.cv/notes/unmeasured-is-not-zero Thu, 08 Oct 2026 18:30:00 GMT What I learned building a per-user ledger for every token, page and image an AI service pays for, and why “we don't know” has to be a value. cost observability https://jayesh.cv/notes/spreadsheets-are-not-documents https://jayesh.cv/notes/spreadsheets-are-not-documents Thu, 08 Oct 2026 18:30:00 GMT Why chunk-and-embed fails on spreadsheets, what replaced it, and the two independent locks on SQL a model writes. retrieval sql safety https://jayesh.cv/notes/never-hand-the-model-the-keys https://jayesh.cv/notes/never-hand-the-model-the-keys Thu, 08 Oct 2026 18:30:00 GMT How an agent can work in someone's mailbox without the model ever holding their credentials, and the four-times “send it?” bug that moved approval out of the tool. agents safety mcp