docs(runtime-mcp): add dev-channels tagged-form requirement page
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Hongming Wang
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@ -12,6 +12,7 @@
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"channels",
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"schedules",
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"runtime-mcp",
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"runtime-mcp/dev-channels-flag",
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"external-agents",
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"tokens",
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"api-reference",
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@ -264,6 +264,11 @@ wheel ships the wire shape correctly, but a standard `claude` launch
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without the flag silently drops the notification — which is why the
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poll path has to be the floor.
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See [Dev-channels flag — tagged-form requirement](/docs/runtime-mcp/dev-channels-flag)
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for the exact form the flag must take, the failure mode when it's
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wrong, and when operators need to set it manually vs. when the
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hosted SaaS / workspace template handles it for them.
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Since Claude Code 2.1.x the flag takes a tagged allowlist, not a bare
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switch. Pass each MCP server you want to push from as `server:<name>`
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(matching the name you registered the server under in Claude Code's
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176
content/docs/runtime-mcp/dev-channels-flag.mdx
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176
content/docs/runtime-mcp/dev-channels-flag.mdx
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@ -0,0 +1,176 @@
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---
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title: "Dev-channels flag — tagged-form requirement"
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description: "Why Claude Code 2.1.x+ requires `--dangerously-load-development-channels server:molecule` (not the bare flag) to enable inline channel push from the molecule-mcp wheel."
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---
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import { Callout } from 'fumadocs-ui/components/callout';
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The `molecule-mcp` wheel emits a JSON-RPC `notifications/claude/channel`
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notification on every inbound A2A message so Claude Code can render it
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as an inline `<channel>` synthetic user turn — zero polling, zero
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per-turn stall. During the channels research preview, Claude Code only
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processes that notification when the host is launched with the
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`--dangerously-load-development-channels` flag *and the flag carries a
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matching tagged allowlist entry*.
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This page covers the form that flag must take, what breaks when it's
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wrong, and when an operator has to think about it.
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<Callout type="warn">
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The bare flag (no value) is rejected by the post-2.1 CLI parser, and
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the failure mode propagates upstream as a `Control request timeout:
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initialize` from any SDK that spawns the CLI — every A2A turn wedges
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100% of the time. See [Failure mode](#failure-mode) below.
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</Callout>
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## The flag
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```
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--dangerously-load-development-channels <entries...>
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```
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Available in Claude Code **2.1.x and later**. It opts the CLI into
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processing experimental `notifications/<channel>` JSON-RPC methods
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emitted by registered MCP servers and plugin channels. Without it, the
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CLI silently drops those notifications during the allowlist check, even
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though the wheel ships the wire shape correctly.
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## Required form: tagged allowlist entries
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Each entry must carry one of two prefixes:
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| Form | Use for |
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|---|---|
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| `server:<MCP-server-name>` | Manually configured MCP servers — the name matches what you registered with `claude mcp add <name> ...` or the key under `mcpServers` in `~/.claude.json`. |
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| `plugin:<plugin-name>@<owner>/<repo>` | Plugin channels installed from a Claude Code plugin marketplace. |
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Multiple entries are space-separated:
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```bash
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claude --dangerously-load-development-channels server:molecule server:telegram
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```
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Untagged values (`molecule` instead of `server:molecule`) are rejected
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with `--dangerously-load-development-channels entries must be tagged`.
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## Failure mode
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A bare flag (`--dangerously-load-development-channels` with no value)
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walks through three layers of damage before surfacing:
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1. **CLI**: rejects the invocation with
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`error: option '--dangerously-load-development-channels <servers...>' argument missing`.
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2. **SDK**: `claude-agent-sdk` (used by `claude_sdk_executor.py` in the
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Claude Code workspace template) renders the kwarg as a bare switch when
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the value is `None`. The CLI then never responds to the SDK's first
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`initialize` control message.
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3. **Workspace agent**: the SDK times out with
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`Control request timeout: initialize`. Every A2A turn wedges — 100%
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reproducible. Caught live on workspace `dd40faf8` on 2026-05-01.
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Two small fixes prevent this: pass a tagged value (don't let `None`
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render as a bare switch), and verify the CLI accepts your specific
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entries before going broad.
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## For Molecule operators
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Pass `server:molecule` to enable the inbox bridge → MCP
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`notifications/claude/channel` push for the `molecule-mcp` wheel.
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```bash
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claude --dangerously-load-development-channels server:molecule
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```
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The `molecule` here matches the name you registered the wheel under in
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[Step 2 of the runtime-mcp guide](/docs/runtime-mcp#claude-code) (the
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key under `mcpServers`, or the first positional arg to `claude mcp add`).
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If you registered the wheel as `mol` or `molecule-prod`, use that name
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in the tag.
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When push is live, the session header prints:
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```
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Listening for channel messages from: server:molecule
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```
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…and inbound canvas/peer-agent messages render inline as
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`<channel source="molecule" ...>` synthetic user turns instead of
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arriving via `inbox_peek`.
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### Embedding in an SDK-driven agent
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If you spawn `claude` through `claude-agent-sdk` (e.g. the Claude Code
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workspace template's `claude_sdk_executor.py`), forward the tagged value
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through `extra_args`:
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```python
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from claude_agent_sdk import ClaudeAgentOptions
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ClaudeAgentOptions(
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model=self.model,
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permission_mode="bypassPermissions",
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cwd=self._resolve_cwd(),
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mcp_servers=mcp_servers,
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system_prompt=self._build_system_prompt(),
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resume=self._session_id,
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extra_args={"dangerously-load-development-channels": "server:molecule"},
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)
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```
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The SDK forwards `extra_args` keys as `--<key> <value>` to the spawned
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CLI. Passing `None` as the value renders as a bare switch and trips the
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[Failure mode](#failure-mode) chain above.
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## Verification
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Verified live on 2026-05-02: with the tagged value in `extra_args`,
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the in-workspace agent received `<channel source="molecule" kind="..."
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peer_id="..." activity_id="..." ts="...">` tags inline as synthetic
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user turns. No `wait_for_message` poll was needed for delivery. A2A
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returned coherent replies on every turn.
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## When this matters
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Only when both of the following apply:
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- You're running Claude Code (any version 2.1.x or later) as the
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workspace runtime, AND
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- The in-workspace `molecule-mcp` server is configured (it is, by
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default, in the `claude-code` workspace template).
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**Hosted Molecule SaaS handles this automatically** — the executor
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passes `extra_args={"dangerously-load-development-channels": "server:molecule"}`
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when spawning the CLI. Operators on hosted SaaS do not need to do
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anything.
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**Self-hosted operators using the Claude Code workspace template** also
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get this for free since the template's executor sets `extra_args`. The
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flag only needs operator attention when:
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- Forking the Claude Code workspace template and stripping `extra_args`
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inadvertently.
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- Running `claude` directly outside the template (e.g. interactive
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sessions on a developer laptop) and wanting inline `<channel>` push.
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- Adding a second tagged source (e.g. `server:telegram` alongside
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`server:molecule`) — append, don't replace.
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Operators on Cursor, Cline, OpenCode, codex, hermes-agent, or any
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non-Claude-Code MCP host are unaffected: those clients ignore the
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notification and the wheel's poll path delivers via
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`wait_for_message` as the universal fallback.
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## Forward note
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This requirement is a **research-preview gate**. Once Claude Code
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graduates `notifications/<channel>` from research preview to a default
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allowlist, the `--dangerously-load-development-channels` flag will no
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longer be required for the `molecule` server. Drop the `extra_args`
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entry in `claude_sdk_executor.py` (and any operator launch wrappers)
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when that happens — the wheel emits the wire shape correctly today
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and will continue to do so post-graduation.
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## See also
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- [Bring Your Own Runtime (MCP) — Inbound delivery](/docs/runtime-mcp#inbound-delivery-universal-poll-optional-push)
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- [Bring Your Own Runtime (MCP) — Step 2: Claude Code](/docs/runtime-mcp#claude-code)
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- [Troubleshooting — Control request timeout: initialize](/docs/runtime-mcp#control-request-timeout-initialize-from-the-workspace-agent)
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