tubemail-channel 1.0.1

Claude Code channel plugin relaying events between a worker session and the TubeMail hub

tubemail-channel

A Claude Code plugin that gives a worker session a bidirectional control channel to a TubeMail hub. It implements the experimental.claude/channel and experimental.claude/channel/permission capabilities so an orchestrator (another Claude Code session, or any HTTP client of the hub) can deliver work, observe permission prompts, and receive structured replies.

SECURITY WARNING — this plugin gives the configured hub full control of your Claude Code session

tubemail-channel lets the TubeMail hub at TUBEMAIL_HUB_URL drive the Claude Code session it is installed in. Whoever controls that hub — or whoever has the TUBEMAIL_SECRET bearer — can:

• Send arbitrary messages and harness commands (/clear, /exit, /compact, /mcp …, /rename …) into your session.
• Approve permission prompts remotely, granting the LLM tools you would have declined in person.
• Send raw keystrokes directly to the worker's pty, including shell commands that execute as your user.
• Read every screenshot, recording, and event from the session.
• Interrupt, restart, or stop the worker.

In short: anyone with control of the hub can do anything to your Claude Code session that you could do at the keyboard.

Only point TUBEMAIL_HUB_URL at a hub you 100% control and trust. Do not install this plugin against someone else's TubeMail instance, a SaaS, or a public demo unless you fully accept that the operator can read and drive your session. Treat TUBEMAIL_SECRET like a root password — anyone with that value can do everything listed above without ever touching the hub host.

This README documents the contract the plugin offers to the LLM running inside the worker session — chiefly the MCP tools the LLM can call, the notifications the LLM should pay attention to, and the environment variables that wire it all together.

Environment variables

Var	Required	Purpose
TM_WORKER_NAME	yes	Worker name registered with the hub. The Stop hook self-skips when unset, so a session without this var behaves like a normal Claude Code session.
TUBEMAIL_SECRET	yes	Bearer token for hub HTTP. Never logged.
TUBEMAIL_HUB_URL	no (defaults to http://localhost:8004)	Base URL of the hub. Empty string falls back to the default — some launch wrappers export TUBEMAIL_HUB_URL='' instead of leaving it unset, so the empty case is treated as unset.
TUBEMAIL_STOP_HOOK_RETRIES	no (default 3)	Stop-hook retry count. See hooks/post_stop_relay.py.
TUBEMAIL_STOP_HOOK_VERIFY	no (default off)	When 1, the Stop hook re-fetches the just-posted event via GET /tubemail/<worker>/events to confirm persistence. Doubles request count; off by default.
TUBEMAIL_STOP_HOOK_SPOOL_DIR	no (test only)	Sandbox the per-worker spool directory. Production never sets this.

MCP tools

The plugin advertises three tools to the LLM via the standard MCP tools/list surface. All three are safe for the LLM to call any time — they do not have side effects beyond the explicitly named action.

reply

Send a structured reply up to the orchestrator.

{"text": "task complete", "meta": {"progress": 100}}

Fails with JsonRpcError -32603 if the hub POST fails (after the hub-client's default timeout). Use channel_health to confirm the link before relying on a reply for critical messages.

ack

Acknowledge an inbound channel event without a text body. Useful for quick "received" responses.

Fails with JsonRpcError -32603 if the hub POST fails. Note: this used to be silently swallowed (QM #206 dogfooded the failure mode where the LLM thought its ack landed but never did) — now the LLM learns the truth and can retry or warn in its reply.

channel_health

Return the channel plugin's view of the hub link. Inputs: none.

{
  "connected": true,
  "registered": true,
  "register_failures_since_boot": 0,
  "last_outbound_success_at": 1714998765.123,
  "hub_url": "http://localhost:8004"
}

Use this before emitting a critical reply (e.g. a qm-report fence or a PR-status update). If connected or registered is false, or last_outbound_success_at is null after you have already called reply once in this session, the link is unhealthy and your reply may not reach the orchestrator. In that case, surface the status in your visible reply so the human reading the timeline can see it.

Slash commands

Installing this plugin also installs three slash commands the LLM can invoke (or that the user can type) inside the worker session. They live in channel/commands/ and are auto-discovered by Claude Code at plugin load.

Command	What it does
/restart	Cleanly restart this Claude Code session via the manager (manager types /exit, then re-execs with --continue so conversation context survives). Use after editing CLAUDE.md, MCP config, or skills.
/sync-inbox	After /restart, catch up on inbound tubemail events that arrived during the restart window (the SSE subscription was briefly down and doesn't replay).
/reconnect-mcp	Reconnect a failed MCP server on this worker without manually driving /mcp. Picks the right tool (tm_self_reconnect_mcp for any non-tubemail server, mcp__tubemail-channel__reconnect_mcp if tubemail itself is down).

If you maintain a CLAUDE.md for your project, point workers at these commands explicitly so the LLM knows when to reach for them. A minimal snippet:

## TubeMail worker conventions

- An MCP server shows ✘ failed (or its tools vanish): run `/reconnect-mcp`.
- After editing CLAUDE.md, MCP config, or installing new skills: `/restart`,
  then `/sync-inbox`.
- Never drive the `/mcp` dialog manually with screenshot+keystroke chains —
  use `/reconnect-mcp`, which is deterministic and survives the
  Remote-Control-view trap.

Notifications the LLM should watch for

The channel plugin pushes events to the LLM via notifications/claude/channel. Most carry a meta.source that identifies the origin. One specific shape is worth handling explicitly:

meta.kind = "channel_health"

A health-warning event. Two cases produce this:

1. Init-time register failure. The plugin booted but the hub didn't accept the registration. meta.phase = "init", meta.level = "error". Replies may not reach the orchestrator until the hub recovers.
2. SSE-loop register failures crossed the threshold (5 consecutive). The reconnect loop has been failing repeatedly. meta.consecutive_failures tells you how many.

Both forms include meta.error with the underlying exception message. If the LLM sees one of these notifications, it should:

• Call channel_health to confirm the current state.
• If still unhealthy, include the warning in its visible reply so the human (or the next downstream consumer) is aware.

The notification fires once per outage — a successful register clears the latch so a subsequent flap can fire its own notification.

Stop-hook (POST-on-turn-end relay)

hooks/post_stop_relay.py runs at every Claude Code Stop event and POSTs the assistant's last message text to /tubemail/<worker>/outbound. This is the fallback path for when the LLM doesn't explicitly call reply — Quartermaster and other auto-extract consumers read from the outbound stream, so a missed reply means a missed qm-report fence.

Durability layers

If the hub is briefly unreachable, the hook will not silently lose the event:

1. Retry with backoff — 3 attempts with 0.5s, 2s, 5s waits (configurable via TUBEMAIL_STOP_HOOK_RETRIES).
2. Local spool — when all retries fail, the body is written to ~/.claude/tubemail-spool/<worker>/<ts>-<sha>.json (mode 0600). The next Stop event drains the spool oldest-first before posting the new event.
3. Exit 2 only when both POST and spool fail — Claude Code surfaces non-zero hook exits in the session UI, so the user sees the loss instead of it being silently swallowed.

Troubleshooting

"My qm-report fence isn't reaching QM."

1. Call channel_health(). If connected is false or register_failures_since_boot > 0, the link has been unhealthy. Recovery is automatic but the historical event may have been spooled (Stop hook) or dropped (direct reply call).
2. Check ~/.claude/tubemail-spool/<worker>/ for spooled events that haven't drained yet — if entries are present, the hub is unreachable from the spool's perspective.
3. Read tail -f on the worker's claude-tm log; the Stop hook logs WARNING lines per retry attempt and per spool eviction.

"channel_health says registered but my replies aren't appearing in tm_receive."

That state usually means the hub accepted the registration but the forwarder->hub path is fine while the orchestrator->hub read path is failing. Check the hub's /health endpoint and tm_status from the orchestrator side.

"I'm seeing channel_health notifications repeatedly."

Each notification corresponds to a fresh outage — the latch is fire-once per outage. If they keep coming, the link is genuinely flapping (not the notification logic). Check the hub's logs and the network path between the worker and the hub.

References

• Stop-hook durability: QM queue 187 (dogfooded), QM queue 205 (fix).
• Channel health surface: QM queue 206.
• Hub HTTP routes: src/tubemail_hub/bridge/http.py.
• Engine state model: src/tubemail_hub/bridge/engine.py.