Runtime
also: runtimes, runtime environment
The time when your app is actually running, as opposed to being written or prepared. The word also names the program that runs your code, like Node.js.
Either the period during which a program executes, or the execution environment that runs it, such as Node.js, Bun or the Python interpreter. A "runtime error" happens while the program runs, rather than during the build.
Writing a play is one thing; performing it is another. Runtime is the live performance. Some problems only show up once the actors are on stage.
Agents separate problems that happen "at build time" from those "at runtime". Runtime problems slip past the build and only appear when someone uses the app, so they need real testing to catch.
This is a runtime error, not a build error. It only happens when the cart is empty, so the build didn't catch it.
Which runtime and version does this project use? Make sure any new code works on that version.
Thinking a successful build means the app works. The build can pass while runtime problems still appear the moment real people use it.