Problem

When using sessions_send to inject orchestration messages into agent sessions (e.g., task instructions, pre-compaction flushes), the messages always render as role: user in the session history. This means client-facing chat UIs display internal system messages as if the end user sent them.

Current Behavior

sessions_send(sessionKey, message) injects the message with role: user, making it visible in chat history alongside real user messages.

Expected Behavior

sessions_send should accept an optional role parameter (e.g., system, developer) so orchestration messages can be injected without appearing in the user-facing conversation history.

Use Case

Multi-agent orchestration where a parent agent sends task instructions to child agents that have client-facing chat UIs. Internal messages like:

• SYSTEM TASK: Continue your deep learning session...
• Pre-compaction memory flush...
• Heartbeat polls

...should not be visible to end users.

Current Workaround

Client-side filtering in chat.html to hide messages matching known system prefixes (/^(SYSTEM|Pre-compaction|HEARTBEAT)/i). This is fragile and requires updating the regex for every new message pattern.