[loganj]

What

Agents that use only the in-app Buzz tools can now make an announce channel: an open channel where anyone can join and read, but only members can post.

• channel_update takes join_role: "member" | "guest". It sends ["join_role", ...] on kind:9002, the same tag the buzz channels update --join-role CLI and the channel details UI (feat(channels): control participation and preserve guest reading #1882) send.
• channel_create takes the same join_role. The relay accepts join_role only on kind:9002, not on kind:9007, so the tool sets it with a second event once the channel exists.
• channel_get shows join as guest for such a channel, so an agent can check the result.
• members: an add with no role gets the channel's join_role, so on an announce channel that person becomes a guest. The answer now says added <key> as guest instead of a bare added <key>.
• join_role: guest is refused on a private channel, as the channel details UI does not offer it there.

Why

The relay (block/buzz#8143) and the app UI (#1882) support announce channels, and the buzz CLI can set them, but channel_create and channel_update had no way to set join_role. Agents running on the in-app MCP tools could not make one.

Details

• On create, join_role is set last, after the template's agents are added. A kind:9000 add with no role tag gives the channel's join_role, so if the channel were an announce channel first, the template's agents would join as guests and could not post.
• member is the default, so channel_create with join_role: "member" sends no second event.
• If the relay refuses the join_role event, the channel still exists; the answer says created <id> and then join_role not set: <reason>.
• Values other than member and guest are refused before anything is published, matching the relay's own validation.

Testing

• pnpm exec vitest run src/buzz-mcp at 0d06af4: 154 passed. New tests cover update to guest and back; create with a template (event order 9007, 9000, 9002, and the template agent stays a member); a later no-role add reported as guest; guest with a refused Canvas and with an unreadable channel; a refused 9002 on create; and invalid or private-channel values. The test relay now gives a no-role add the channel's join_role, as the relay does.
• pnpm run typecheck and biome check pass.
• Live, against a relay built from block/buzz main (ghcr.io/block/buzz:main, revision 75854111b, run locally), through the real tool handlers with the standalone nodeClient at 0d06af4:
  • channel_create {visibility: open, join_role: guest} → created <id> / new people join as guests; the relay's kind:39000 has ["restricted"] and ["join_role","guest"], and channel_get shows join as guest.
  • A second agent's channel_join → you: guest; its send is refused: restricted: only members can post in this channel. The owner's send succeeds.
  • members {add, role: member} → added <key> as member, and that agent can then post. members {add} with no role → added <key> as guest.
  • channel_update {join_role: member} → updated, and join as guest is gone; back to guest → updated. A non-admin's channel_update {join_role} is refused by the relay (actor not authorized ... join_role).
  • channel_create with a template agent and join_role: guest → the agent is added first and is you: member, and it can post. The channel then shows join as guest.
  • channel_create {visibility: private, join_role: guest} → refused before publishing.
  • Not exercised live: the desktop host's signer path (app_agent_publish). It signs and posts the same events without a kind or tag allowlist.

🤖 Generated with Claude Code

[kalvinnchau]

🤖 Code review at 0d06af4: no findings. join_role is validated before anything is published, set after template agents are added so they stay members, and the relay always publishes an explicit join_role tag so the update read-back check holds for member too. vitest src/buzz-mcp (154 passed) and biome check pass locally.