> cascading from an assumption that was incorrect
I have found including this in my AGENTS.md to be quite transformative in this regard:
> Always use an aggressive red/green TDD-approach. It is critical to remember that in the red phase, things like module/exports import failures due to trying to import file paths that don't yet exist, exports that don't yet exist, etc. is not valid TDD. For valid TDD, the test cases must actually run. For this, you must create stubs of the expected modules and exports in the red phase, so that the test cases actually run and fail on the test case assertions themselves. In some cases, when using this approach, once in a while some of the red phase test cases might "incidentally" pass, and this is ok. Before running red phase tests you should always make predictions about the number of test cases you expect to fail/pass -- this count is not the number of test files or test suites, but rather the number of test cases. By performing these red phase expected counts of passing/failing test cases, it will help you catch errors in your prior reasoning quickly and efficiently.
> Always use a proof-driven, scientific method-based approach to validate hypotheses, assumptions, and conclusions: define the smallest falsifiable hypothesis, create or identify a reproducible failing case, gather direct evidence, make the smallest targeted change, and then re-run the same proof to confirm the issue is fixed. Avoid speculative fixes, broad rewrites, or changing multiple variables at once. When possible, preserve the reproduction as a regression test before implementing the fix. Consider that when gathering evidence, additional logging and durable files can be very helpful.
> The strict TDD and proof-driven approaches described above could be described as "proof-driven development". Try to internalize and generalize these concepts, as they are broadly applicable.