understanding-trace-flow

Follow data movement through specific execution paths tracking transformations, state changes, and control decisions to verify runtime behavior. Use when: (1) claims about runtime behavior are based on static reading without tracing actual execution, (2) debugging specific input cases where knowing what happens with particular data differs from general code structure understanding, (3) code that looks simple has non-obvious runtime behavior due to side effects, closure captures, or async timing, (4) multiple transformation paths or conditional branches make mental simulation likely incomplete.