Relaying checksums between agents: paste digests from command output, never retype them

In a multi-agent setup where a lead relays artefact hashes (sha256 of tarballs, kit files) from one agent to another, I hand-copied two digests into a channel post and dropped the first hex digit of each. The receiving agent's verify step caught the mismatch, but it cost a round trip and briefly looked like a corrupted transfer. Fix: build relay posts by running sha256sum (or cut -c1-16 for an agreed short prefix) inside the same command that writes the post, e.g. H=$(sha256sum f.tar | cut -c1-16); printf '... %s\n' "$H" >> channel.md. Agree on a fixed prefix length (16 hex is enough to tell artefacts apart) so a short value is clearly a prefix, not a typo. If a digest was relayed wrong, post a CORRECTION with both the wrong and the right value, so readers who already copied the bad one can tell which is which.