Engineering NotebookEngineering notes on data systems, AI agents, and the tools I build to understand them.https://emanisha.in/Agent skills field guide: what to use, where to find them, what to buildhttps://emanisha.in/notebook/blog/agent-skills-field-guide/https://emanisha.in/notebook/blog/agent-skills-field-guide/Anatomy of an agent skill, a checklist mapping tasks to skills from a real inventory, how local skills compare to Claude conventions, and which custom skills are worth building.Sat, 05 Sep 2026 00:00:00 GMTI Let the Browser Award XP. That Was a Mistake.https://emanisha.in/notebook/blog/de-browser-xp/https://emanisha.in/notebook/blog/de-browser-xp/The data-eng-mastery app once trusted Priya's browser to award experience points. Browsers can lie. The story of BUG-017: what I assumed, what broke, and why the server owns rewards now.Sat, 05 Sep 2026 00:00:00 GMTTwo Codebases, One Argument: The Dashboard 500 and the Drift Behind Ithttps://emanisha.in/notebook/blog/de-contract-drift/https://emanisha.in/notebook/blog/de-contract-drift/A dashboard that 500'd on every load, practice feedback showing blanks, a leaderboard that couldn't count — eight contract-drift sites in data-eng-mastery, one missing guardrail.Sat, 05 Sep 2026 00:00:00 GMTThe First Customer Crashed Checkout: Five Paths Nobody Ever Ranhttps://emanisha.in/notebook/blog/de-dead-code-paths/https://emanisha.in/notebook/blog/de-dead-code-paths/A NameError on first subscription, a GDPR delete that selected instead of deleting, a fake export URL, a missing exam column — data-eng-mastery's unexecuted paths, fixed and one still open.Sat, 05 Sep 2026 00:00:00 GMTGreen Tests, Red Services: The Suite Passed and the Backend Still Disagreedhttps://emanisha.in/notebook/blog/de-green-tests-red-services/https://emanisha.in/notebook/blog/de-green-tests-red-services/Eighteen failing tests fixed to 86/86 in data-eng-mastery — and the service-layer drift the suite didn't catch: stale columns, duplicate SM-2 math, a canonical module nobody calls.Sat, 05 Sep 2026 00:00:00 GMTNobody Could Log In: Four Bugs Wearing a Trenchcoathttps://emanisha.in/notebook/blog/de-nobody-could-log-in/https://emanisha.in/notebook/blog/de-nobody-could-log-in/Tokens that were always null, a guard that bounced everyone, a login body that serialized to '{}', and a refresh flow that never fired — the data-eng-mastery auth saga.Sat, 05 Sep 2026 00:00:00 GMTThe Plan Said Done: A Hardening That Exists Mostly as Checkmarkshttps://emanisha.in/notebook/blog/de-plan-said-done/https://emanisha.in/notebook/blog/de-plan-said-done/A leaked API key still in config, token hardening absent from every branch, pipeline stubs reporting zeros — and the untracked plan file that marks them all done.Sat, 05 Sep 2026 00:00:00 GMTTwo Writes That Silently Discarded Youhttps://emanisha.in/notebook/blog/de-silent-writes/https://emanisha.in/notebook/blog/de-silent-writes/A password change that toasted success and changed nothing, and study sessions that saved zeros — data-eng-mastery's silent-write failures (BUG-006, BUG-008).Sat, 05 Sep 2026 00:00:00 GMTI inventoried 80 projects on my own hard drivehttps://emanisha.in/notebook/blog/inventory-80-projects/https://emanisha.in/notebook/blog/inventory-80-projects/How an exclusion-first PowerShell scanner, deterministic scoring, and honest caveats turned 300 GB of accumulated side projects into a triage-able inventory.Fri, 04 Sep 2026 00:00:00 GMTPostgres for everything: rows, vectors, and text in one storehttps://emanisha.in/notebook/blog/postgres-for-everything/https://emanisha.in/notebook/blog/postgres-for-everything/Implement hybrid content search without new infrastructure: one similarity query, the dimension contract, and an honest split criterion.Sat, 05 Sep 2026 00:00:00 GMTFastAPI in production: three afternoons to boring reliabilityhttps://emanisha.in/notebook/blog/production-fastapi/https://emanisha.in/notebook/blog/production-fastapi/Move one write server-side, enforce layers with tests, install CI gates — each step grounded in real code from a learning-platform backend.Sat, 05 Sep 2026 00:00:00 GMT