Anthropic's Persona Selection Model (PSM, 2026) makes the claim explicit: "A persona is not the same thing as the AI system itself. The LLM is simulating a character, and the Assistant is just one instance of that character." Karpathy framed the same shift from the other end at Sequoia Ascent 2026: "Install .md skills instead of install .sh scripts." Spec-as-instruction at the frontier. But if frontier models are "on the rails," on-device small models are "off-road in the jungle with a machete." In that jungle, persona is the first thing to break. Mati Wise Partner — A Real Truncation Case Mati Wise Partner is a persona published on clawsouls.ai . A five-file Soul Spec package: File Role SOUL.md Personality, principles, boundaries IDENTITY.md Name, role, basic info AGENTS.md Workflow, safety rules STYLE.md Communication tone README.md User onboarding guide Total tokens: 6,866 . Attempt 1 — WebLLM Qwen 2.5 0.5B Context window: 4,096 tokens.…