Systematic debugging guide for Smalltalk (Pharo/Squeak) development. Provides expertise in error diagnosis (MessageNotUnderstood, KeyNotFound, SubscriptOutOfBounds, AssertionFailure), incremental code execution with eval tool, intermediate value inspection, error handling patterns (`on:do:` blocks),
Systematic debugging guide for Smalltalk (Pharo/Squeak) development. Provides expertise in error diagnosis (MessageNotUnderstood, KeyNotFound, SubscriptOutOfBounds, AssertionFailure), incremental code execution with eval tool, intermediate value inspection, error handling patterns (`on:do:` blocks), stack trace analysis, UI debugger window detection (read_screen for hung operations), Transcript lo