which-cairn

name	which-cairn
description	Use when the user asks "which cairn am I using?", "what server is this?", "am I on local or remote?", "how do I switch cairns?", or similar questions about the current cairn MCP connection. Calls `whoami` to read transport, endpoint, and the list of registered cairns; explains how to switch.

Which cairn server is this?

When the user asks any of:

• "Which cairn am I using?" / "What cairn is this?"
• "Which server am I connected to?" / "Is this local or remote?"
• "What's the endpoint?" / "What URL am I pointing at?"
• "How do I switch to a different cairn server?"
• "Why don't I see my decisions from the other project here?"

…this is the skill.

What to do

1. Call whoami (no cairn parameter needed if there's only one registered). The response includes a server block:

   {
     "server": {
       "transport": "stdio" | "streamable-http" | "sse",
       "endpoint": "http://127.0.0.1:8765/mcp" | null,
       "registered_cairns": ["coral-bleach", "lit-monitor"]
     },
     "cairn": "coral-bleach",
     "cairn_path": "/home/kyle/cairns/coral-bleach",
     ...
   }
   

   • transport: "stdio" + endpoint: null → the server is running locally as a subprocess of Claude Code; the cairns it serves are on this machine's disk.
   • transport: "streamable-http" (or "sse") + an endpoint URL → the server is a long-lived HTTP service somewhere; cairns live on that host's disk, not the user's.

2. Summarize plainly for the user. Three pieces of information:

   • Which cairn the current write would go to (cairn field).
   • Whether the server is local or remote (transport and endpoint).
   • Which other cairns this server knows about (registered_cairns).

   Sample reply:

   "You're currently writing to coral-bleach (local stdio server; cairn directory /home/kyle/cairns/coral-bleach). This server also knows about lit-monitor — pass cairn=\"lit-monitor\" on any tool call to write there instead."

   For a remote-HTTP setup:

   "You're connected to the group's HTTP cairn server at https://cairn.lab.example.org/mcp, currently writing to shared-physics-paper. The server has just this one cairn registered."

When the user asks how to switch

The answer depends on what kind of switch they mean:

"Write to a different cairn the same server knows about"

No switch needed. The MCP tool's cairn parameter selects which one. Pass cairn="<name>" on the next write:

add_finding(cairn="lit-monitor", author="kyle", title="...", body="...")

The names in whoami's server.registered_cairns are valid values.

"Switch which server Claude Code talks to"

That's a Claude Code config change, not something the MCP server can do for itself. Tell the user:

"Claude Code's MCP-server set is controlled by claude mcp commands. Run claude mcp list to see what's registered; claude mcp remove <name> to drop one; claude mcp add ... to add another. After changes, restart any open Claude Code sessions to pick up the new set."

If the user wants both local and remote available at the same time, both can be registered (typically under different names like cairn and cairn-remote); the agent then has access to mcp__cairn__* AND mcp__cairn-remote__* tools and the user picks which one in conversation.

"Pair my project repo with a different cairn"

This is a cairn.toml change. Direct the user at:

# In their project repo:
cairn link --name <other-cairn>                    # different local cairn
cairn link --endpoint <url> --name <handle>        # switch to a remote one
cairn link --force ...                             # overwrite an existing pairing

After re-linking, agents working in that project repo route to the newly-paired cairn automatically.

Do not

• Do not edit the user's ~/.claude.json, ~/.config/cairn/server.toml, or cairn.toml files on their behalf to "switch" things. These are config files the user owns — surface the commands and let them run.
• Do not invent server endpoints or cairn names. If whoami returns a list, the names in it are the only ones this server knows about.
• Do not assume cwd determines the cairn at the MCP layer — it determines the cairn at the CLI layer. For MCP tools, the cairn parameter is what discriminates.

Acceptance criteria

• The user gets a one-paragraph answer to "which cairn am I using?" that names the cairn, the server, and the alternatives.
• If they ask "how do I switch?", they get the command shape relevant to the kind of switch they mean (cairn vs server vs project pairing).
• No silent edits to user-owned config files.