Today I Learned
The small stuff that quietly makes you a better dev — one note at a time.Das kleine Zeug, das dich nebenbei zum besseren Dev macht — Notiz für Notiz.
29 notes29 Notizen~108 min to read all~108 Min. Lesezeit26 tagssince June 2026seit Juni 2026
A test that reads your docs
An ordinary failing test whose subject is a sentence. The mechanism is three lines: read the fact out of the code, look for it in the document, complain when it is missing.
My biggest CLAUDE.md was 224 KB
Nine agent instruction files went from 455,530 characters to 88,584 — and the split that actually saves context is a plain markdown link, not an `@path` import.
Don't read what the agent did — read what it decided
A long AI task leaves behind a wall of output. Having it finish with a one-page report instead means you can judge the thinking before you check the work.
Stop watching the terminal — let it text you
A Telegram bot can report when a long job finishes; the useful decision is what is safe to put in the message.
The port took a day; getting the game right took four
An archived Java card game became a web and Android app in five days; most of the work was validating the rules and interface.
The cleanup that never ran
Firestore TTL needs a policy, not just a date; one shared document can also throttle every write.
One missing line, and all of GitHub can deploy to your project
Passwordless CI needs two scopes: the identity provider names the repository, and IAM limits who may impersonate the deploy account.
Good app, no public API — so I gave it one
An undocumented mobile API returned a convincing empty success; comparing it with the app exposed the real data path.
On a small tip, the 5% isn't the fee that hurts
On a $3 tip, the fixed card fee matters more than the platform's advertised 5% cut.
You can add a backend to a static site without running one
A "who else is here" room and per-post likes on two sites that have no server at all — and nothing at all connects until the visitor asks it to.
Signing in almost ate twenty books
Verso works before you ever sign in — which is exactly why signing in can make twenty books vanish from the screen with nothing deleted. What I built instead.
I locked myself out of my own app with one toggle
A static site can protect signup without its own server, but enabling enforcement before the client update locks everyone out.