Obsidian Claude Multivault Access

Connect multiple Obsidian vaults to Claude Desktop at the same time, using the REST-API-based mcp-obsidian MCP server — with Obsidian free to stay open.

If you've tried this and hit persistent 401 Unauthorized / Error 40101: Authorization required on your second vault even though the key is correct, this repo explains exactly why and fixes it.

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TL;DR — why a second vault fails out of the box

mcp-obsidian reads your API key but ignores OBSIDIAN_PORT and OBSIDIAN_HOST. Every vault's server process connects to the hardcoded default https://127.0.0.1:27124. So your second vault sends its key to the first vault's REST server, which rejects the unknown key with a 401.

It looks like an auth problem. It's actually a port-routing bug. The key was never wrong — it was being delivered to the wrong server. Full write-up in docs/ROOT_CAUSE.md.

Two things are needed to run multiple vaults:

1. Give each vault's Local REST API plugin a unique port (they all default to 27124 too).
2. Patch mcp-obsidian so it actually honours the port you configure — run patch_mcp_obsidian.py.

Separately: if every vault stops working at once with no 401 involved — servers absent entirely rather than erroring — that's a different bug: mcp-obsidian has no version ceiling on its mcp SDK dependency, so a new major mcp release can silently break it. See docs/MCP_VERSION_BUG.md and the version pin in the config example below.

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Prerequisites

• Obsidian with the "Local REST API" community plugin by Adam Coddington (displayed as "Local REST API with MCP", id obsidian-local-rest-api — GitHub) installed and enabled in each vault you want to connect.
• Claude Desktop (this uses claude_desktop_config.json; local MCP servers do not work in the claude.ai web app or mobile).
• uv installed (provides uvx), which runs mcp-obsidian. Verify with uvx --version.
• Python 3.9+ on PATH (to run the patch script).

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Setup

Example below uses three vaults on ports 27124 / 27125 / 27126. Use as many as you like — just keep each port unique.

1. Enable the Local REST API plugin in every vault

In each vault: Settings → Community plugins → Browse, search "Local REST API", install the one by Adam Coddington (shows as "Local REST API with MCP", id obsidian-local-rest-api) → Install → Enable. Then open its settings and copy the API key — you'll need one per vault.

2. Give each vault a unique port

In each vault's Local REST API settings, set a different HTTPS port:

Vault	Port
Vault A	27124
Vault B	27125
Vault C	27126

(Equivalently, edit port in each vault's .obsidian/plugins/obsidian-local-rest-api/data.json. If you edit the file directly, reload that vault so the plugin re-reads it.)

Verify each port is actually listening (each vault must be open in Obsidian for its server to run):

• Windows: netstat -ano | findstr "2712"
• macOS/Linux: lsof -iTCP -sTCP:LISTEN | grep 2712

3. Patch mcp-obsidian

Run mcp-obsidian once so it's downloaded (uvx mcp-obsidian — Ctrl-C after it prints that it's running), then:

python patch_mcp_obsidian.py

It finds every installed copy, backs each up as tools.py.bak, and makes them honour OBSIDIAN_HOST / OBSIDIAN_PORT / OBSIDIAN_PROTOCOL. Safe to re-run.

4. Add one server entry per vault to Claude Desktop

Edit claude_desktop_config.json and add a server per vault, each with its own port and its own key. See examples/claude_desktop_config.example.json.

"mcp-obsidian-vault-a": {
  "command": "uvx",
  "args": ["--with", "mcp<2.0.0", "mcp-obsidian"],
  "env": {
    "OBSIDIAN_API_KEY": "<vault A key>",
    "OBSIDIAN_HOST": "127.0.0.1",
    "OBSIDIAN_PORT": "27124"
  }
},
"mcp-obsidian-vault-b": {
  "command": "uvx",
  "args": ["--with", "mcp<2.0.0", "mcp-obsidian"],
  "env": {
    "OBSIDIAN_API_KEY": "<vault B key>",
    "OBSIDIAN_HOST": "127.0.0.1",
    "OBSIDIAN_PORT": "27125"
  }
}

Why --with "mcp<2.0.0": mcp-obsidian places no upper bound on its mcp SDK dependency, so uv can silently install a newer, incompatible mcp major version and crash the server on startup. This flag pins it to a known-working range. See docs/MCP_VERSION_BUG.md for the full analysis — safe to drop once mcp-obsidian itself caps this dependency upstream.

Config file location:

• Windows: %APPDATA%\Claude\claude_desktop_config.json
• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

Windows note: if uvx isn't found, use the absolute path to uvx.exe as "command", e.g. "C:\\Users\\<you>\\AppData\\Roaming\\Python\\Python3xx\\Scripts\\uvx.exe". Back up the config before editing, and keep the JSON valid.

5. Open the vaults and restart Claude Desktop

• Open each vault in its own Obsidian window (vault switcher → Open in new window), so every REST server is listening on its port at the same time.
• Fully quit Claude Desktop (tray → Quit; confirm no Claude process remains) and relaunch, so it re-reads the config.

6. Verify

Ask Claude to list files in each vault, or test a port directly:

curl -sk https://127.0.0.1:27125/vault/ -H "Authorization: Bearer <vault B key>"

A JSON file list = success. A 401 = the key doesn't match the server on that port (see Troubleshooting).

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Troubleshooting

Symptom	Likely cause	Fix
401 / Error 40101 on some vaults	mcp-obsidian ignoring the port → key sent to wrong vault's server	Run patch_mcp_obsidian.py, restart Claude Desktop
401 even after patching	Two config entries share a port, or a key is pasted to the wrong entry	Ensure each entry has a unique port + its matching key
Read timeout / connection refused	That vault isn't open in Obsidian, or nothing is listening on the port	Open the vault; confirm the port with netstat/lsof
Only one vault ever works	All plugins still on default port 27124	Give each vault a unique port (Step 2)
Worked, then broke after an update	uv re-extracted a fresh, unpatched copy	Re-run patch_mcp_obsidian.py
Tools appear but every call fails	tools/list is local; only real calls hit Obsidian	It's a connection issue — check port/key/patch
All vaults vanish at once, no 401, patch script says already-patched	A new major mcp SDK release broke mcp-obsidian (unbounded dependency)	Add "--with", "mcp<2.0.0" before "mcp-obsidian" in args; see docs/MCP_VERSION_BUG.md

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How it works / root cause

The 401 is a port-routing bug, not an auth bug, and it is not an HTTP-vs-HTTPS mismatch (the package always uses HTTPS). Each Obsidian vault runs its own REST server on its own port and accepts only its own key; the key says "am I allowed?" while the port decides "which server am I talking to?". Because the package hardcoded the port, every key was mailed to the same address. Full analysis: docs/ROOT_CAUSE.md.

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Notes & caveats

• The patch edits files in uv's cache. uv cache clean or a package update can replace them — just re-run the patch script (it's idempotent).
• Each vault must be open in Obsidian for its REST server to run. This is the trade-off of the REST-API approach; in exchange, Obsidian can stay open while you work with Claude.
• mcp-obsidian has no upper version bound on its mcp SDK dependency — a new major mcp release can break it with no warning, on every configured vault at once. The --with "mcp<2.0.0" pin in the config example guards against this; see docs/MCP_VERSION_BUG.md.
• Consider contributing the fix upstream so patching is eventually unnecessary.

Built on / Credits

This project is a setup guide and a patch — it does not include or redistribute the tools below. It only helps you configure them and fixes a bug in one of them. All credit for the underlying software goes to their authors:

• mcp-obsidian by Markus Pfundstein (MIT) — the MCP server this project configures and patches.
• Obsidian Local REST API by Adam Coddington (MIT) — the Obsidian plugin that exposes each vault over REST.
• Obsidian and Claude Desktop — the apps this connects together.

Both mcp-obsidian and the Local REST API plugin are MIT-licensed, which is what makes it fine to reference them and to patch a locally-installed copy. If you find this useful, consider starring their repos too — and ideally the port fix here gets contributed back upstream so patching is no longer needed.

License

Released under the MIT License — you're free to use, modify, and share the guide, the analysis, and the patch script. The tools this builds on (mcp-obsidian and the Local REST API plugin) are MIT-licensed separately by their own authors.