AP3
Learning OS

Notebook / reverse chronological

Weekly log.

No metrics. Just the questions, mistakes, products, and small discoveries that are worth carrying forward.

Week 31

Things learned

The runtime is part of the interface. Before changing a component, I need to understand what owns its data, subscription, and recovery path.

Mistakes

I described existing Casset runtime work as if it still needed to be built. The better exercise is to profile it, prove it, and harden the remaining seams.

Products studied

Casset, Apple Music, Linear

Books / notes

React docs on effects · TypeScript notes on discriminated unions

Questions

Which product states are still being collapsed into empty or unavailable?

Older entry

Week 30

Things learned

An event vocabulary is a product model written in verbs. Instrumentation is only useful when the question and the data-quality boundary are explicit.

Mistakes

I reached for a new analytics name before checking the canonical event system already in the product.

Products studied

PostHog, Arc, Are.na

Books / notes

Notes on product analytics, request tracing, and observability

Questions

What is the smallest trustworthy funnel for a Profile World?

Older entry

Week 29

Things learned

A feature is not complete at merge. Release verification, monitoring, and recovery are part of the designed experience.

Mistakes

I treated operational evidence as follow-up work instead of part of the original definition of done.

Products studied

Vercel, Sentry, Apple Weather

Books / notes

On Writing Well · opening chapters

Questions

Which intervention needs an interface, and which only needs a clear runbook?