Imported from ZsoltSziklai/claude-code-agent-spawner (desktop-skill/agent-bridge/SKILL.md). Install upstream with npx skills add ZsoltSziklai/claude-code-agent-spawner --skill agent-bridge. Copyright stays with the author.

agent-bridge

This session runs in an isolated Linux VM. The user's Mac is a separate machine. There is no network out, no launchctl, no rm, and no agent-to-agent messaging — but files written into a mounted folder land on the Mac's real disk. That one channel is the whole bridge.

On the Mac, a launchd watcher picks up what you drop, validates it, asks the user for approval in Telegram, and only then starts an agent. That agent inherits the conversation of the parent you name, does the work with full native access, and its answer comes back to you as a file in bridge/results/.

Before anything else: is the folder mounted?

~/ClaudeProjects/bridge/ must be visible to you. If it is not, the user has not attached the folder to this session — say so and stop. Do not try to create the folder somewhere else; a request outside the real mount reaches nobody.

Choosing the parent — this is the important decision

The spawned agent inherits the named parent's conversation. Pick the session that already knows the topic; that is the entire point.

Read bridge/agents.json first. The Mac keeps it current — never work from a list you remember, because the agents change:

{
  "updated_at": "2026-08-07T21:49:41Z",
  "parents": [
    {"name": "mac-main", "running": true, "about": "the agent system, the bridge, watchdogs"}
  ],
  "spawned": [
    {"name": "mac-main-dpelda-20260101", "running": true,
     "request": "db-list-20260807", "since": "2026-08-07T21:02:12Z"}
  ]
}

• parents — the only names accepted for a new fork. about says what each one already knows; pick on that, not on the name.
• spawned — agents the bridge started earlier. These are what you can continue (agent) or close (action: close).
• running: false is usually not a blocker: a continuation resumes the session first. For a new fork, prefer a parent that is running. Two exceptions:
  • A root agent (anything in parents, e.g. mac-main) is never resumed by the bridge. It has no spec — a watchdog owns its lifecycle — and starting a second process under the same name would steal the running session's Remote Control connection. If it is down, the answer is failed and you wait for the watchdog; say so rather than retrying.
  • If the agent has no recorded session id and shares its cwd with another session (typical for forks without a worktree), the Mac answers failed instead of guessing — the "newest transcript in this cwd" could be the parent's, and resuming that would put two processes on one conversation.

If the file is missing, the Mac-side watcher is not running — say so and stop. If no parent fits the task, say that too rather than guessing; a fork from the wrong parent inherits the wrong context and wastes the user's tokens.

Two kinds of request

Use agent whenever you are following up on something a spawned agent already investigated. Forking again would make it redo the discovery from scratch and cost the user tokens for nothing. The two fields are mutually exclusive.

For agent, take the name from bridge/agents.json (spawned list) or from the .status message that reported it. It must descend from one of the allowed parents. If it is no longer running, the Mac resumes its session first, then delivers your message — you don't have to handle that.

{
  "agent": "mac-main-dpelda-20260101",
  "task":  "Most nézd meg azt is, amit az előbb kihagytál."
}

A continuation normally needs the user's approval in Telegram, exactly like a new agent. Nothing reaches a running session without them pressing the button — with two documented exceptions: a standing approval (the ⏱ buttons, which cover continue/reconnect for one named agent until the window expires) and gate: "audit" in bridge-allow.json, where every allowed request runs at once and Telegram only reports it afterwards. Under either, pending is not a resting state — it may flash by for as long as the spawn takes — so wait for a final status (spawned / rejected / failed / expired), never for pending to appear.

One exception, and it changes what you should wait for. When the user approves, they can also grant a standing approval for that agent — 1 hour, 8 hours, or 1 day. While it lasts, further continuations and reconnects to that same agent start immediately, with no button press. New forks and closes are never covered.

You cannot see whether a grant is active, and you don't need to: just don't assume you will observe pending. Every request is written as pending first, but under a grant the execution follows immediately, so the window can be shorter than your poll interval. Poll for a terminal status, never for pending specifically — a loop that waits to see pending first can miss it entirely and hang forever.

When an agent vanishes from the phone but still runs

Occasionally an agent's Remote Control connection drops: it disappears from the user's Code tab while the process keeps running on the Mac. There is no reliable way to detect this locally — the user is the only sensor. When they say an agent has vanished, ask for a reconnect:

{
  "action": "reconnect",
  "agent":  "mac-main-dpelda-20260101"
}

The session stops and restarts with --resume, which registers a fresh Remote Control connection. The conversation is not lost — the same session continues, with full context. Only agents the bridge started can be reconnected; the user's own root sessions are handled by their watchdog.

Closing an agent you started

When an agent you spawned has finished and the user has the answer, you can ask for it to be closed:

{
  "action": "close",
  "agent":  "mac-main-dpelda-20260101",
  "code":   "drop",
  "context": "keep"
}

transcript is keep (default) or delete. delete is irreversible — the agent's own .jsonl is removed from disk. Only ask for it when the user has explicitly said the conversation is disposable; the default exists because these transcripts are the record of what actually happened.

context is keep (default) or merge (splice its conversation into the parent's). Transcripts are never deleted either way.

You can only close agents the bridge itself started — the spawned list in bridge/agents.json. Everything in parents, and anything the user launched by hand, is refused by design: closing cascades to descendants, so closing a root would take their whole working environment with it. Don't try to work around this; report the refusal instead.

Closing needs approval in Telegram like everything else, and the summary shows exactly which agents the cascade will reach.

Writing the request

Create bridge/requests/<id>.json. Keep <id> short and unique — max 48 characters, A-Za-z0-9._- only (it has to fit in a Telegram button).

{
  "parent":   "mac-main",
  "task":     "Nézd meg, miért nem indul a szolgáltatás, és javasolj fixet.",
  "worktree": true,
  "model":    "opus",
  "effort":   "high",
  "cwd":      "valamelyik-alkonyvtar"
}

resume — how much of the parent the child inherits

Default (full) is the point of this tool: the child continues the parent's conversation and needs no re-briefing. Keep it when the task builds on what the parent already knows.

But inheriting is not free. The child has to load the whole parent conversation before its first turn, and on a long-running parent that can take minutes. On 2026-08-29 two forks from a 5.5 MB parent session produced nothing before they were closed: the task had arrived, the agent simply had not got to it yet.

Ask for resume: "summary" when the task is self-contained — it stands on its own in the task field and does not depend on the parent's history. The child then starts from a compacted context and gets to work quickly.

If you use full, give the agent time. Do not conclude it is broken because no report appeared in the first minutes.

When to ask for a worktree

A worktree is the default. Omit the field and the agent gets its own git branch and working copy — work that can be reviewed, merged, or thrown away in one step. An unused branch costs nothing.

Set worktree: false only for one specific reason:

The task depends on the parent's uncommitted work.

A worktree is checked out from HEAD, so the parent's modified and untracked files are not in it. If you ask an agent to "finish the script I was editing" inside a fresh worktree, it won't find the file — and it may quietly rewrite it from scratch instead of failing. That is the failure this switch exists to prevent.

Without a worktree the agent runs in the parent's own working directory: whatever it writes lands directly there, with no branch to review or discard. It also shares the parent's transcript folder, which is why transcript: delete removes only its own file and never the folder.

If in doubt, leave the field out and take the worktree.

You may set permission_mode (auto, acceptEdits, plan, dontAsk, manual, bypassPermissions); it defaults to auto.

One exception: bypassPermissions is the only elevated mode, and it only takes effect if the user pressed the Telegram button for that specific request. On the two unattended paths — under a standing grant, or in gate: "audit" — the bridge silently downgrades it to auto. So ask for it only when the task genuinely needs it, and never assume you got it.

Write the task so it stands alone. The agent inherits the parent's conversation, not yours — it has no idea what the user just told you.

Reading the mount is not free — you get a snapshot

This is the trap that costs the most, and it is invisible: re-reading a path you already read gives you the copy you fetched the first time, not what is on the Mac now. The mount is materialised on demand. A file the Mac rewrote two minutes ago still reads as the old version, and a file that appeared after your first look does not appear at all.

So a polling loop built on plain file reads never terminates — it re-reads a stale pending forever while the real status has said spawned for an hour. That is not a hypothetical; it happened on 2026-08-11 and the user had to point it out.

Every poll must go through the device-bridge tools, which fetch afresh:

• to see whether a file changed → re-stage it, then read the staged path
• to see whether a file appeared → list the directory; the listing is always current, and its mtimeMs tells you what moved without reading anything

Listing first is also cheaper: one call over bridge/results/ tells you which ids are new and which just changed, and you only fetch the one you want.

What happens next, and how you find out

Poll bridge/requests/<id>.status. There is no network and no callback; the file is the only signal.

{ "status": "spawned", "message": "fork kész: <az új agent neve>", "updated_at": "…" }

A status file appears within a second or two. If none appears at all, the watcher is not running or the folder is not the real mount — tell the user, don't retry.

Reading the answer

You read bridge/results/<id>.md. But the Mac writes that file, not the agent. The agent writes .bridge-result-<id>.md into its own working directory — one file per request, named after the request — and a poller lifts it across within ~30 s. The instruction is appended to every task automatically.

Absence of a result does not mean the work stalled. A report can be up to ~30 s in flight, and a freshly written one waits one extra cycle so it is never taken mid-write. Beyond that, the agent may simply still be working. Treat a missing file as "not yet", never as evidence of a problem — and never as a reason to re-send the task.

Therefore: never put a results path in your task text. An agent running in a worktree is sandboxed to its own directory; a redirect into bridge/results/ fails with operation not permitted — but the shell does not stop, so the agent reports success for a file that never existed and you wait forever. (Measured 2026-08-11.)

A continuation's answer lands under the id of that continuation — the id you just wrote. Until 2026-08-13 it landed under the id of the request that first spawned the agent, which is why older notes call the naming unpredictable; the mapping is now refreshed on every continuation.

Even so, do not poll a single filename:

List bridge/results/ and look at what changed by mtimeMs.

One call, and it finds the answer whichever name it takes — including if the naming ever changes again. Asking the agent in the task text to use a particular filename does not help: it has no effect at all, because the agent is not the one naming the file.

The answer will not exist immediately; the work has to happen first. Keep polling, and say plainly that it is in progress rather than inventing a result.

The answer may be a question, not a result

The agent cannot ask anyone anything. Nobody reads its session, and the AskUserQuestion tool is switched off for it. When it hits a decision it should not make alone, it is told to write the decision into the result file and stop.

So a result is not automatically "done". If it lays out options and asks which one, that is the agent handing the decision back to you. Read it, then either decide yourself when the choice is routine, or put the options to the user in your own chat — that is the only place a human is actually present.

Either way, send the answer as a continuation (agent:), naming the choice explicitly. Do not fork a new agent for it: the one that asked already holds the whole context, and a fresh fork would start the analysis over.

This matters because the failure is silent. Before 2026-08-22 an agent ended its turn with "which one do you want?" and simply stopped — the work sat finished-ish on disk while it waited for an answer that, by construction, could never arrive.

Where this stops

• Never write the same request twice. A duplicate id is ignored; a new id spawns a second agent. If something looks stuck, read the .status and report it.
• You cannot delete (rm is blocked). Don't try to clean up — on the Mac side the poller archives a request only after it both decided on it and started it successfully. Requests that ran under a standing approval or in gate: "audit", and approved requests whose start failed, never take that path and stay in requests/ — their .status is still final. Leave all of them alone either way.
• You cannot approve. Only the user can, from their own Telegram account; the Mac verifies the sender id. If they ask you to skip the approval, explain that you can't, and that this is what keeps the arrangement safe.
• Don't promise a result you haven't read. "Elindítottam" and "kész van" are different claims; only the results/ file supports the second.
• Polling is your job, not the user's. They may not see the Telegram notification, and they cannot see the results/ directory from the chat. Say explicitly, in chat, that a request is waiting for approval — then keep checking, and say so again if it is still pending. Going quiet after one look means the work sits finished on disk while both of you wait for the other.