The "signed transaction, not a log stream" framing is exactly right. Logs are optimistic - you assume they're complete and unmodified. Receipts are pessimistic - you verify before trusting.

We've been thinking about a related problem at toran.sh: capturing what an agent actually sent to external APIs (and what came back) without trusting the agent's self-reported logs. Different angle - we focus on the API request/response level rather than the decision/action level - but the same underlying insight: the source of truth needs to be outside the agent's control.

The Ed25519 + canonical JSON approach is clean. Question: how are you handling schema evolution? If the receipt format changes, older receipts still need to verify but newer tooling might expect different fields.