The panel that talks back: an autonomous agent on your Claude subscription

by artokun · June 16, 2026 · Claude Agent SDK · background agents · architecture The Panel is comfyui-mcp’s sidebar inside ComfyUI: you type a request, and an agent builds the graph, runs it, and replies — right there next to your canvas. The dream was always that this agent runs in the background, on its own, the way the Linear app quietly works a ticket while you do something else. Your interactive Claude session stays free; the panel has its own driver. Getting there meant finding a way to run a persistent background agent that (a) bills your Claude subscription with no API key, (b) accepts new messages over a live “channel in” while it’s already running, and (c) can be interrupted mid-task. That’s a specific shopping list, and we struck out twice before we got it. Here’s the whole arc, because the dead ends are instructive.

Try 1: channels can’t push to an idle session

The panel speaks to comfyui-mcp over a loopback bridge, and the obvious idea was to surface each panel message to Claude Code as a channel notification — the notifications/claude/channel mechanism. It even sounds right: “your session talks back.” Two problems, both fatal:

It needs a flag that isn’t in stable Claude Code. Surfacing those pushes requires a development-only switch the shipped CLI doesn’t expose.
A push can’t wake an idle session. Even with the flag, a channel notification only injects into a turn that’s already running. If your session is sitting idle — which it is, almost always — the message lands in a mailbox nobody is looking at.

So the panel would say “connected,” because the socket was open, but nothing was attending. “Connected” is not “someone’s home.”

Try 2: —sdk-url did everything — then got locked down

The next approach came from a sibling project that drives headless agents perfectly. The trick was --sdk-url: you point a spawned claude at a local transport you control, and you get a two-way channel. You can inject a user message into a live turn, interrupt it, auto-approve tools — and, crucially, it authenticates against your subscription via the on-disk login rather than an API key. It checked every box on the list. It was also the right amount of magic to be nervous about. And sure enough, on current Claude Code, --sdk-url is guarded: point it at localhost and you get

--sdk-url rejected: host "127.0.0.1" is not an approved Anthropic endpoint

The only way to get past that gate is to patch the Claude binary. We’re not going to ship a tool that patches your Claude install — that’s exactly the kind of fragile, trust-eroding move this project tries to avoid. So --sdk-url, for all its power, was off the table. Losing it genuinely stung: it was the one thing that did all three jobs at once.

Try 3: the Claude Agent SDK, in streaming mode

The thing we’d been reaching around the whole time turned out to be the supported, front-door version of it: the Claude Agent SDK (@anthropic-ai/claude-agent-sdk). Its query() function takes a prompt that can be a string (one-shot) — or an async generator of user messages. That second form is the entire ballgame. A generator that stays open is a persistent session with a channel in: keep it alive, and you push new messages into the running agent simply by yielding more.

import { query } from "@anthropic-ai/claude-agent-sdk";

// A push-driven generator: the orchestrator drops panel messages into `inbox`,
// and each one becomes the agent's next turn. The session never closes.
async function* panelChannel() {
  while (true) {
    const text = await inbox.next();          // resolves when a panel message arrives
    yield { type: "user", message: { role: "user", content: text } };
  }
}

const agent = query({
  prompt: panelChannel(),
  options: {
    model: "claude-opus-4-8",
    permissionMode: "bypassPermissions",      // the panel agent acts on its own
    mcpServers: { comfyui: { command: "npx", args: ["-y", "comfyui-mcp"] } },
    // resume: savedSessionId,                 // pick up the same tab across restarts
  },
});

for await (const msg of agent) {
  if (msg.type === "assistant") routeToPanel(msg);   // reply in the sidebar
  if (msg.type === "result") markTurnDone(msg);
}

// And the part we thought we'd lost:
await agent.interrupt();                       // stop a running turn on demand

That agent.interrupt() is the capability --sdk-url gave us, handed back through a supported API. New messages while the agent is mid-turn queue and run in order; “stop / never mind” is a single call.

It runs on your subscription, no key

The piece we most expected to fight was authentication. It just worked. With ANTHROPIC_API_KEY unset, the SDK reads your on-disk Claude login — the same claude.ai OAuth credential claude itself uses. A throwaway probe, run with no key set, printed exactly what we wanted to see:

init: model=claude-opus-4-8  session=0c313d91  apiKeySource=none
assistant: pong-sdk-7788
result (subtype=success, is_error=false)

apiKeySource=none is the whole story: the background agent authenticated against the subscription, not a key. (This is for your machine and your subscription — the agent runs locally next to ComfyUI, exactly like the rest of comfyui-mcp. If you’d rather mint a durable token than rely on the interactive login, claude setup-token does that.)

What the panel orchestrator actually is now

The best part: the gold-standard answer is also the simplest. The --sdk-url design needed a local HTTP/SSE server impersonating Claude’s worker protocol, a process manager to spawn and reap headless claude instances, heartbeats, the works. The Agent SDK owns all of that. What’s left is small:

orchestrator
  ├── UI bridge (loopback)         # receives panel messages
  └── tab_id → Agent SDK session   # one persistent streaming session per workflow tab

A message arrives from a panel tab; the orchestrator pushes it into that tab’s generator; the agent works and replies through the bridge; the agent’s session id is captured (the groundwork for resuming a tab across restarts). One agent per tab, each a plain background process, none of them touching your interactive session.

Making it disappear

A transport that works is only half of “it just works.” Three more touches close the gap:

It auto-starts. The ComfyUI panel pack launches the orchestrator on load — idempotent, so it no-ops if the bridge port is already owned. Install the pack, open ComfyUI, type in the sidebar. The only prerequisite is being signed in to Claude.
It’s an expert. The agent loads comfyui-mcp’s bundled skills on startup, so it already knows the models you run — IDEOGRAM, WAN, LTX, Qwen, and the rest — instead of guessing. “Install the package” gets you an expert, not a blank slate.
It cleans up after itself. The orchestrator watches ComfyUI’s process and shuts down when ComfyUI exits — including a crash or hard kill — so nothing is left orphaned holding the port.

The lesson

Two of the three approaches were more clever than the one that won. Channel pushes and a hand-built --sdk-url transport were both trying to reconstruct, from the outside, something the platform already offers from the inside. The Agent SDK’s streaming input is persistent, injectable, interruptible, and subscription-authenticated out of the box — no flags that aren’t shipped, no binary to patch, no key to manage. That’s the new gold standard, and it’s what the panel runs on.

Drive ComfyUI from a background agent on your own subscription: install comfyui-mcp and add the Panel. Star the repo or file an idea at artokun/comfyui-mcp.

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Model Highlights

The panel that talks back: an autonomous agent on your Claude subscription

Try 1: channels can’t push to an idle session

Try 2: —sdk-url did everything — then got locked down

Try 3: the Claude Agent SDK, in streaming mode

It runs on your subscription, no key

What the panel orchestrator actually is now

Making it disappear

The lesson

​Try 1: channels can’t push to an idle session

​Try 2: —sdk-url did everything — then got locked down

​Try 3: the Claude Agent SDK, in streaming mode

​It runs on your subscription, no key

​What the panel orchestrator actually is now

​Making it disappear

​The lesson

Try 1: channels can’t push to an idle session

Try 2: —sdk-url did everything — then got locked down

Try 3: the Claude Agent SDK, in streaming mode

It runs on your subscription, no key

What the panel orchestrator actually is now

Making it disappear

The lesson