buzz-acp subscribe=all delivers typing/presence events to agents: token burn per keystroke and false typing badge

[pat-dubois]

Summary

When buzz-acp runs with BUZZ_ACP_SUBSCRIBE=all and no BUZZ_ACP_KINDS override, ephemeral events are delivered to the agent session. Every typing indicator (kind 20002) and presence update (kind 20001) wakes the agent and starts a turn. Two effects:

1. Token cost per keystroke. Each wake-up is a model call even when the agent decides to do nothing. A human composing one message produces dozens of typing events, so the agent pays for dozens of no-op turns.
2. A confusing feedback loop in Desktop. While the agent processes the wake-up, Desktop shows it as typing (the working badge in desktop/src/features/agents/agentWorkingSignal.ts falls back to bot typing signals and active turns). The human sees "agent is typing" whenever they themselves type, before the agent has anything to say.

Reproduction

1. Run buzz-acp with BUZZ_ACP_SUBSCRIBE=all (the documented way to make an agent respond to un-mentioned channel messages) and leave BUZZ_ACP_KINDS unset.
2. Open the channel in Desktop as a human member and start typing a long message.
3. Watch the agent flip to "typing..." while you type, and watch the harness logs record a turn per typing event.

Expected

Ephemeral kinds (20001, 20002, and arguably 24200 observer frames) should never reach the agent subprocess, or at minimum should be excluded by default when subscribe=all resolves with no kinds override. Mentions mode already ships a curated default (resolve_channel_filters in crates/buzz-acp/src/config.rs uses KIND_STREAM_MESSAGE, KIND_WORKFLOW_APPROVAL_REQUESTED, KIND_STREAM_REMINDER); All mode passes kinds: None and subscribes to everything.

Workaround

Set an explicit allowlist, for example:

BUZZ_ACP_KINDS=9,40002,40003,5,7,1059,40100,40007,46010,46020

This keeps messages, edits, deletions, reactions, DMs, canvas updates, reminders, and workflow events while dropping the keystroke echoes. Confirmed working on a self-hosted deploy (compose stack from deploy/compose).

Suggested fix

In resolve_channel_filters, give SubscribeMode::All a default exclusion of ephemeral kinds when kinds_override is None, or introduce a small default allowlist mirroring the mentions-mode one plus reactions and canvas. Happy to send a PR if maintainers agree on the direction.

[okhan1980]

Your BUZZ_ACP_KINDS allowlist also works for a Desktop-managed agent, not just a self-hosted compose deploy — worth noting since the two config paths differ.

Setup: Buzz Desktop 0.5.2 on macOS, hosted relay, agent started by Desktop under the Claude Code harness. Set both variables in the per-agent box (agent settings → Advanced → Environment variables):

BUZZ_ACP_SUBSCRIBE=all
BUZZ_ACP_KINDS=9,40002,40003,5,7,1059,40100,40007,46010,46020

Desktop restarted the agent on save and it came up clean. A remote human member's plain, un-mentioned message got a substantive reply 22 seconds later, and no turn fired while she was composing.

Context for why this pairing matters: subscribe=all is currently the only way to make an agent reachable from another machine at all, because of #3204 / #3277 / #2508 — the mention picker draws its candidates from the local managed-agent list, so an agent hosted elsewhere can never be @-mentioned. That makes subscribe=all the standard workaround rather than a niche mode, and this issue the tax on it: without the kinds allowlist, every keystroke the human types costs a model call, so the workaround for one bug lands you in another.

Given that, a sensible default exclusion of ephemeral kinds when subscribe=all resolves with no override (your suggested fix, #3675) seems worth taking on its own merits — the mode is going to see a lot more use than it was probably designed for.