TL;DR: I shipped FIVE, an open-source MCP server that generates JSON personality constraints for any LLM. Drop the JSON into your system prompt and the character stops drifting. Different approach from typical guardrails — this one filters input via cognitive primitives, not output via moderation. Harness is MIT, constraint generation is $1/call. The unusual part is where the cognitive model came from: a decade of teaching kids in Japan. The problem most builders eventually hit I...