Thanks for the insight on prompt drift. You're right — flat prose breaks down fast across iterations. We ended up with a similar solution: a modular spec system where the engine rules (shared across all brands) and theme files (brand-specific: colors, fonts, narrative structure) are separate named documents. The LLM reads both before generating, so roles never bleed across runs. Essentially named blocks, just at the file level instead of XML tags. Will check out flompt — the visual decomposition could be useful for auditing where drift starts.