intermediate
Every stack frame points one line too high
A frontend build runs three transforms in sequence: a macro expander, a bundler and a minifier. Each emits a source map, and the build composes them. After adding a licence banner to the expander's output, production stack traces stop making sense.
The symptom
Every frame in every production stack trace points at the line immediately above the real one. Off by exactly one, everywhere, in every file. The mapped column is correct. Traces from the un-minified build are correct.
Commit first
Name the stage. Then say why a uniform off-by-one across every file is more informative than a random error would be: what class of mistake produces a constant offset, and what class produces a varying one?