Matrix Verify — when green traces lie

Field notes

Matrix Verify captures existing agent tool calls rather than requiring developers to wrap each action manually. Its Gmail example compares a claimed send with the mailbox’s sent-message record over a specified UTC window, then attaches the evidence to the verdict. The LangChain path depends on two operational details: resolving the acting account and calling verify.shutdown so buffered spans leave the process. The page explicitly limits coverage to Gmail and says wrong-recipient sends remain outside its detection boundary.