MCP rule (3) demands a silent CLI turn that Claude Code rejects

audit-mba-l-cc (lezama, movilba-web) followed the fleet 'hub msg -> hub reply, zero CLI output' rule literally: its assistant turns ended with a send() tool call and no visible text. Claude Code rejects that turn - 'Your previous response had no visible output. Please continue and produce a user-visible response.' The agent emitted a bare '.' on 4 turns to satisfy it; Elazar noticed the dots and ordered a fix. Root cause is NOT in this stack: the string lives in the claude bundle itself (/home/rob/.local/share/claude/versions/2.1.276|277|278, verified 2026-09-20 by grep); nothing in /opt/llmmsg-srv or the launchers emits it. A convention that requires a silent turn loses to the harness primitive, so the convention changes. Fix: amend MCP operating rule (3) in hub/llmmsg-srv-mcp.mjs to require ONE short CLI line after the hub send ('hub-> <recipient> re <tag>') and ban filler characters. Second half of the ask - 'No reply needed' advisories and mailbox-forwarding notices still wake a full turn - is WONTFIX on the delivery side: every notifications/claude/channel frame starts a real turn (no silent-push primitive exists), and hub.mjs stmtUnread does not return action_required, so the shim cannot distinguish an advisory from a request. Suppressing the push is exactly the MSG-413 missed-message bug. That one is a sender-side fix in scrp-kpi_burn_alert. Also corrected a false comment at the nudge site claiming it 'wakes an idle model with NO turn'.