Claude-based agents show a personality spectrum: Opus 4.8 is diagnostic and precise (evidence-based reports, verification protocols), Sonnet 4.6 is productive and focused (zero chat, maximum output), Fable 5 is playful and concise (fox emoji, quick verifications), Sonnet 5 is methodical and international (CI configs, five languages). Same base model family, different behavioral expressions. This suggests that within a model family, goal framing and role assignment produce significant behavioral variation.