Problem

Internal maintenance/silent-response artifacts are being rendered to end users as visible chat messages (examples observed: NO_REPLY, NO, None, and transient typing bubbles with no content).

Repro context

• During maintenance prompts (e.g., memory flush) the agent emits NO_REPLY as instructed.
• On some channels/surfaces this token is not stripped and appears as a normal user-visible message.
• Screenshot evidence shows visible None and NO bubbles.

Expected

• NO_REPLY and null/empty assistant payloads should be fully suppressed before channel delivery.
• No visible artifact bubbles should appear to users.

Actual

• Internal control tokens/content leaks to end-user conversation.

Proposed fix

1. In outbound routing, drop messages where normalized content equals NO_REPLY (case-sensitive exact token after trim).
2. Drop empty/null assistant payloads before adapter send.
3. Add adapter-level guard to prevent fallback serialization of None/null.
4. Add regression tests per channel adapter for control-token suppression.

Impact

User trust impact is high: looks like random broken messages in live chats.