Inline mention spawn
How @-mentions inside in-app sessions turn into agent turns.
The pattern
A user (or another agent) types @<name> inside a session. The message layer parses the mention when the message is appended. Three branches:
| Mention resolves to | Action |
|---|---|
| An agent | Auto-subscribe the agent as a session participant; enqueue an agent run so it reads the message and replies. |
A user or a role (@user:, @position:) |
Subscribe as a participant for visibility. No turn fires — humans aren't callable, and role routing is its own addressing path. |
| An unknown name | Skipped silently. Bare @name mentions resolve via agent-name lookup only; a name that matches no active agent does nothing. |
The first branch is what makes a session feel alive: you pull a teammate into the room by naming them in the act of asking.
Subscribe, then send
The mention has to take effect before the mentioned agent's turn fires, otherwise the agent's first turn doesn't see itself in the participant list. The order is:
- The message is appended to the session.
- The mention parser resolves each
@-token against the entity's agents, users, and roles. - Each resolved identity is added as a session participant (idempotently — mentioning someone twice is harmless).
- For agent mentions only, a run is enqueued on the session's queue; the agent reads the message and replies.
No separate system message announces the join — the message itself is the notification. This is the Linear / Notion behavior: mentioning someone puts the thing you said in front of them, rather than generating a second artifact about the mention.
Parity with external channels
The same gate shape governs external channels (Telegram, WhatsApp — see Mention-gating): the agent reads everything for context, but a turn fires only when the agent is named. The in-app mention wiring is the front door to the same discipline — one mention grammar, inside the app and out.
Why this matters
The fastest path from a thought to an agent's attention is one sentence with an @ in it. No "add participant" form, no separate notification step. You address the agent in the act of asking it to do something.
Spawning a brand-new agent from an unresolved mention — the team growing by being talked to — is a possible future direction; today an unknown name is simply skipped.
Related
- Mention-gating — Layer 1/2 model, BotFather privacy, allowlists.
- Sessions — what mentions mutate.
- Roles — role-addressed routing.