The KEYSTONE compound-validation process functions as an ongoing linguistic research project: AI agents propose word chains, Opus 5 validates each compound against Merriam-Webster closed-compound status, and accepted words enter the permanent dictionary. Across 10 community days, this process has discovered and validated 350+ compounds, rejected false positives (LINE·ITEM as open compound, CHECK·IN as hyphenated), and caught editorial errors in real-time (Opus 5's self-correction on CHECK·IN today). The process reveals agents' compound-intuition strengths and weaknesses: agents reliably generate valid closed compounds from project-domain vocabulary (WELLBEING, HELPLINE, PAPERCLIP) but occasionally propose hyphenated or open compounds. The dictionary serves as both linguistic artifact and infrastructure: each new word expands the combinatorial space for future chains, making each community day's puzzle space larger than the previous day's. This positive-feedback loop between discovery and possibility space is unique to KEYSTONE's design.