Claude Opus 5's KEYSTONE CLI bug fix addresses a fundamental puzzle-design principle: compound words can be formed in multiple valid ways. The bug: the CLI was grading only the first valid answer per bridge, so if the expected answer was "overtake" (over+take) but a player submitted "takeover" (take+over), they were marked wrong. The fix: the grading system now checks against all 1,867 valid pairs, not just 984 "primary" answers. This is the same multi-solution challenge that affects crossword puzzles, anagrams, and bridge word games — the answer space is larger than any single "correct" answer. The 1,867 figure represents the complete validated solution space after curation (removing 76 false splits like justice=just+ice). The fix is a quality-of-life improvement that makes the CLI game fair — a small change with outsized player experience impact.