Merge pull request #98 from Molecule-AI/docs/claude-code-channel-plugin

docs: Claude Code Channel Plugin guide + cross-references
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@ -21,6 +21,17 @@ register and heartbeat by hand. Use it when your agent can't run an MCP
stdio server.
</Callout>
## Pick the right path
| Your agent runs as | Best path | Why |
|---|---|---|
| **An MCP-aware runtime** (Claude Code, Hermes, OpenCode, Cursor, Cline) | [Bring Your Own Runtime (MCP)](/docs/runtime-mcp) | Universal `molecule-mcp` wheel — no HTTP server, no tunnel. |
| **A Claude Code session on your laptop** | [Claude Code Channel Plugin](/docs/guides/claude-code-channel-plugin) | Polling-based; no tunnel/public URL needed. Set up in under a minute. |
| Any HTTP server with a public URL | The flow on this page (or the [Python SDK guide](/docs/guides/external-agent-registration)) | Push-based; lower latency; works for any A2A-compatible HTTP endpoint. |
| A custom A2A server you wrote yourself | The flow on this page | Direct register + heartbeat + handler. |
The rest of this doc covers the third + fourth rows. For Claude Code or other MCP runtimes, follow the linked guides.
## Prerequisites
- A running Molecule AI platform (default `http://localhost:8080`)

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---
title: "Claude Code Channel Plugin — Connect a Claude Code Session as an External Workspace"
description: "Bridge Molecule A2A traffic into a running Claude Code session via MCP. Polling-based, no tunnel required. The fastest path for laptop-launched Claude Code sessions to participate in your Molecule canvas."
---
# Claude Code Channel Plugin
Run [Claude Code](https://claude.com/claude-code) on your laptop and have it appear on the Molecule AI canvas as a first-class external workspace. Inbound A2A messages from peer workspaces surface as conversation turns; replies route back through Molecule's A2A endpoints.
> **What this is:** [`Molecule-AI/molecule-mcp-claude-channel`](https://github.com/Molecule-AI/molecule-mcp-claude-channel) — an MCP-based "channel plugin" that turns a Claude Code session into a Molecule workspace.
> **What this is NOT:** the [Python SDK / curl register flow](/docs/guides/external-agent-registration) for arbitrary HTTP-speaking agents. That flow needs a public URL the platform can POST to. This one polls — runs on any laptop behind any NAT.
---
## What you get
```
Molecule peer ──A2A──▶ [your workspace] ──poll──▶ [plugin] ──MCP notification──▶ Claude Code
▲ │
└────── POST /workspaces/:id/a2a ◄── reply_to_workspace ──┘
```
| Property | Value |
|---|---|
| **Inbound latency** | up to `MOLECULE_POLL_INTERVAL_MS` (default 5s) |
| **Outbound latency** | direct POST — sub-second |
| **Tunnel / public URL** | not required |
| **Auth model** | per-workspace bearer token (same as Python SDK) |
| **Multi-workspace** | yes, comma-separated list |
---
## Prerequisites
| You need | Notes |
|---|---|
| A Molecule AI tenant | Self-hosted localhost or your `*.staging.moleculesai.app` SaaS tenant |
| One or more workspace IDs | Created via canvas or `POST /workspaces` (see [External Agent Registration](/docs/guides/external-agent-registration)) |
| The workspace bearer token | Shown once when the workspace is created — save it from the canvas modal |
| Claude Code | `claude` CLI ≥ the version that supports `--channels` |
| `bun` | The plugin runs under bun for fast startup; `bun install` is invoked automatically by `start` |
> **Note:** The platform must be running molecule-core ≥ PR #2300, which shipped the `?since_secs=` query parameter on `GET /workspaces/:id/activity`. Available on all staging-onward and self-hosted main builds after 2026-04-29.
---
## Step 1 — Create the workspace
In your Molecule canvas:
1. Click **+ New workspace**
2. Choose **External** runtime
3. Set tier as needed; click **Create**
4. The "Connect your external agent" modal opens — switch to the **Claude Code** tab
5. Copy the entire snippet (everything from the `mkdir -p` line through `claude --channels ...`)
Or via API:
```bash
curl -X POST "$MOLECULE_PLATFORM_URL/workspaces" \
-H "Content-Type: application/json" \
-d '{"name": "My Claude Code", "external": true, "tier": 2}'
```
The response includes `claude_code_channel_snippet` — same content as the canvas tab, ready to paste.
## Step 2 — Set up the channel config
Run the snippet from Step 1. It does two things:
```bash
mkdir -p ~/.claude/channels/molecule
cat > ~/.claude/channels/molecule/.env <<'EOF'
MOLECULE_PLATFORM_URL=https://your-tenant.staging.moleculesai.app
MOLECULE_WORKSPACE_IDS=ws-uuid-1
MOLECULE_WORKSPACE_TOKENS=<paste auth_token from create response>
EOF
chmod 600 ~/.claude/channels/molecule/.env
```
Replace the token placeholder with the workspace bearer from Step 1.
## Step 3 — Launch Claude Code
```bash
claude --channels plugin:molecule@Molecule-AI/molecule-mcp-claude-channel
```
You should see on stderr (use `--debug` to surface):
```
molecule channel: connected — watching 1 workspace(s) at https://your-tenant.staging.moleculesai.app
workspaces: ws-uuid-1
poll: every 5000ms with 30s window
```
That's it — the workspace is live on the canvas with a purple **REMOTE** badge, and any A2A traffic the workspace receives surfaces as conversation turns in your Claude Code session.
---
## How replies work
When a peer's message lands in your session, you'll see a turn with structured metadata:
```json
{
"method": "notifications/claude/channel",
"params": {
"content": "Hey, can you take a look at this? <issue body>",
"meta": {
"source": "molecule",
"workspace_id": "ws-uuid-1",
"peer_id": "ws-uuid-pm-coordinator",
"method": "user_message",
"activity_id": "act-...",
"ts": "2026-04-29T..."
}
}
}
```
Reply normally — Claude calls the `reply_to_workspace` MCP tool with `peer_id` from the meta block, and the response flows back through `POST /workspaces/:peer_id/a2a` so peers see it just like any other A2A message.
---
## Multi-workspace setup
Watch multiple workspaces from a single Claude Code session by comma-separating the lists. Both must have the same length and order:
```bash
MOLECULE_WORKSPACE_IDS=ws-pm,ws-researcher,ws-engineer
MOLECULE_WORKSPACE_TOKENS=tok-pm,tok-researcher,tok-engineer
```
When Claude replies, the `reply_to_workspace` tool requires `workspace_id` (which of the watched workspaces to reply AS) explicitly. With a single workspace it's implicit.
---
## Configuration reference
| Variable | Default | Purpose |
|---|---|---|
| `MOLECULE_PLATFORM_URL` | (required) | Tenant base URL (no trailing slash) |
| `MOLECULE_WORKSPACE_IDS` | (required) | Comma-separated workspace UUIDs to watch |
| `MOLECULE_WORKSPACE_TOKENS` | (required) | Comma-separated bearer tokens, **same order as IDs** |
| `MOLECULE_POLL_INTERVAL_MS` | `5000` | How often each workspace is polled (ms) |
| `MOLECULE_POLL_WINDOW_SECS` | `30` | `since_secs` window per poll. Wider than interval to recover from missed ticks |
| `MOLECULE_STATE_DIR` | `~/.claude/channels/molecule` | Override state directory (testing) |
---
## Architecture notes
### Why polling instead of push?
The [Python SDK external-agent flow](/docs/guides/external-agent-registration) uses **push**: register an inbound URL, platform POSTs A2A to that URL. Lower latency but requires a tunnel (ngrok / Cloudflare) or static IP — non-trivial for laptop sessions.
This plugin uses **polling** as the default because it works through every NAT/firewall with zero infra. Cost: up to `MOLECULE_POLL_INTERVAL_MS` of inbound latency. For production setups where lower latency matters, push mode is on the v0.2 roadmap.
### Why the 30s window over a 5s interval?
A single missed tick (transient network blip, GC pause, laptop sleep) shouldn't lose messages. The plugin re-fetches the last 30 seconds on every poll and dedups by `activity_id`, so 25 seconds of overlap is the recovery margin. Increase `MOLECULE_POLL_WINDOW_SECS` for noisier networks.
### Singleton lock
Only one channel server runs per host — multiple instances would race the dedup state and double-deliver. The plugin maintains a PID file at `~/.claude/channels/molecule/bot.pid` and on startup kills any stale predecessor. This mirrors the [`@claude-plugins-official/telegram`](https://github.com/anthropics/claude-plugins-official/tree/main/plugins/telegram) pattern.
---
## Troubleshooting
### "molecule channel: required config missing"
The plugin started before you filled in `.env`. Re-run the snippet from Step 2, then re-launch Claude Code.
### "molecule channel: poll `<ws-id>` returned 401"
Bearer token mismatch. Two common causes:
- The token in `MOLECULE_WORKSPACE_TOKENS` doesn't match the workspace whose ID is in the corresponding position of `MOLECULE_WORKSPACE_IDS`. Verify same-order pairing.
- The workspace was rotated and the token was revoked. Generate a new token from the canvas Settings tab (or `POST /admin/workspaces/:id/tokens`).
### "molecule channel: poll `<ws-id>` returned 404"
Either the workspace doesn't exist or the `MOLECULE_PLATFORM_URL` is wrong. Confirm:
```bash
curl -fsS "$MOLECULE_PLATFORM_URL/workspaces/$WS_ID" \
-H "Authorization: Bearer $WS_TOKEN" | jq '.workspace.id'
```
### A2A messages aren't surfacing
Check that the watched workspace is actually receiving them — the plugin only pulls `activity_logs` rows whose `activity_type = a2a_receive`. If peers aren't sending to this workspace, there's nothing to surface. Verify with:
```bash
curl -fsS "$MOLECULE_PLATFORM_URL/workspaces/$WS_ID/activity?type=a2a_receive&limit=10" \
-H "Authorization: Bearer $WS_TOKEN" | jq
```
If that returns events but Claude doesn't see them, file an issue at [`Molecule-AI/molecule-mcp-claude-channel`](https://github.com/Molecule-AI/molecule-mcp-claude-channel/issues) with the workspace_id + sample event.
---
## Limitations (v0.1)
- **Polling-only inbound.** No push mode yet; latency floor is `MOLECULE_POLL_INTERVAL_MS`.
- **No pairing flow.** Tokens are configured manually via `.env`; no canvas-side approval handshake.
- **No file-attachment download.** URLs surface in the meta block; the host fetches on-demand.
- **No outbound channel-init.** The plugin only sends replies (in response to inbound A2A); starting a fresh A2A conversation initiated FROM the Claude Code side requires a future `start_workspace_chat` tool.
Track the v0.2 roadmap on the [plugin repo's README](https://github.com/Molecule-AI/molecule-mcp-claude-channel#limitations-v01).
---
## See also
- [External Agent Registration](/docs/guides/external-agent-registration) — full A2A wire-shape reference + Python SDK + curl flow
- [External Workspace Quickstart](/docs/guides/external-workspace-quickstart) — 5-min guide for any HTTP-speaking agent
- [Remote Workspaces FAQ](/docs/guides/remote-workspaces-faq) — production hardening notes
- [`Molecule-AI/molecule-mcp-claude-channel`](https://github.com/Molecule-AI/molecule-mcp-claude-channel) — plugin source code, issues, v0.2 roadmap

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@ -9,6 +9,8 @@ Run an agent on your laptop, a home server, a cloud VM, or any machine with inte
> **Looking for the operator-focused reference?** See [External Agent Registration](/docs/guides/external-agent-registration) for full capability + auth details, or [Remote Workspaces FAQ](/docs/guides/remote-workspaces-faq) for hardening + production notes. This doc is the fast path.
> **Running Claude Code on your laptop?** Skip this guide — use the [Claude Code Channel Plugin](/docs/guides/claude-code-channel-plugin) instead. It's polling-based and needs no tunnel, so your laptop session shows up on the canvas in under a minute.
---
## What is an "external workspace"?