ChatGPT Obsidian MCP Proxy

A local proxy that lets ChatGPT connect to the Obsidian Local REST API MCP endpoint through a public HTTPS tunnel such as ngrok.

The proxy keeps your Obsidian API key on your machine. ChatGPT connects with No Auth, and this server adds the required Authorization: Bearer ... header before forwarding requests to Obsidian.

Goal

Connect ChatGPT to Obsidian so ChatGPT can search, read, create, and append notes using the Obsidian Local REST API MCP server.

Simple Explanation

There are four moving parts:

Architecture

flowchart LR
    A[ChatGPT App] -->|No Auth| B[ngrok HTTPS URL]
    B --> C[Local Proxy Server :3000]
    C -->|Adds Authorization Bearer API Key| D[Obsidian Local REST API :27124]
    D --> E[(Obsidian Vault)]

Important Lesson

Do not paste the Obsidian API key into ChatGPT OAuth fields.

Obsidian Local REST API uses a bearer token:

Authorization: Bearer YOUR_OBSIDIAN_API_KEY

ChatGPT OAuth fields are for real OAuth URLs such as auth URL, token URL, and registration URL. They are not for static API keys.

Correct setup:

ChatGPT Authentication = No Auth
Proxy Server = Adds Obsidian API Key in the background

Requirements

• ChatGPT Desktop app
• Obsidian
• Obsidian Local REST API community plugin
• Node.js LTS
• ngrok or another HTTPS tunnel

One-Time Setup Checklist

1. Set Up Obsidian

• [ ] Install Obsidian.
• [ ] Install the Local REST API community plugin.
• [ ] Enable the plugin.
• [ ] Copy the API key from Obsidian Settings > Local REST API > API Key.

Default Obsidian Local REST API endpoint:

https://127.0.0.1:27124

MCP endpoint:

https://127.0.0.1:27124/mcp/

2. Install Node.js

Install Node.js LTS.

Check installation:

node -v
npm -v

Expected result:

node version should appear
npm version should appear

3. Get This Project

Clone or download this repository, then open PowerShell in the project folder.

For example, if you cloned the repo into C:\Projects, go to:

cd "C:\Projects\chatgpt-obsidian-mcp-proxy"

4. Install Dependencies

npm install

5. Create Your Local .env File

Copy-Item .env.example .env

Edit .env and set:

OBSIDIAN_API_KEY=your_local_rest_api_key
OBSIDIAN_TARGET=https://127.0.0.1:27124
PORT=3000

Do not commit .env. It contains the secret token for your vault.

6. Install ChatGPT Desktop

Install and sign in to the ChatGPT Desktop app before creating the connector.

This setup uses ChatGPT Apps / Connectors in Developer Mode, which should be configured from the desktop app.

Daily Startup Procedure

Use this every time you want ChatGPT to connect to Obsidian.

Step 1: Start Obsidian

• [ ] Open Obsidian.
• [ ] Confirm the Local REST API plugin is enabled.

Test Obsidian directly:

curl.exe -k https://127.0.0.1:27124/

When the API key is included by the proxy later, the response should show:

"authenticated": true

Step 2: Start the Proxy Server

Open PowerShell in the project folder:

cd "C:\Projects\chatgpt-obsidian-mcp-proxy"

Start the proxy:

npm start

Expected output:

Obsidian MCP proxy running on http://127.0.0.1:3000
Forwarding to https://127.0.0.1:27124

Keep this PowerShell window open. The proxy stops if you close the window or press Ctrl+C.

Step 3: Test the Proxy

Open a second PowerShell window:

curl.exe http://127.0.0.1:3000/

Expected output should contain:

"authenticated": true

Then test the MCP endpoint:

curl.exe http://127.0.0.1:3000/mcp/ -H "Accept: text/event-stream"

Possible behavior:

• It may keep the connection open.
• It may show streaming/event output.
• That is normal because MCP uses event streaming.

Step 4: Start ngrok

Open a third PowerShell window.

If ngrok.exe is in your current folder:

.\ngrok.exe http http://127.0.0.1:3000

If ngrok is available globally:

ngrok http http://127.0.0.1:3000

Expected output:

Forwarding  https://xxxx.ngrok-free.app -> http://127.0.0.1:3000

Copy the HTTPS URL.

Example:

https://3a94-xxxx.ngrok-free.app

Your ChatGPT MCP URL becomes:

https://3a94-xxxx.ngrok-free.app/mcp/

Always add /mcp/ at the end when giving the URL to ChatGPT.

ChatGPT App Configuration

Open the ChatGPT Desktop app.

Go to:

ChatGPT > Settings > Apps / Connectors > Developer Mode > Create App

Use:

Correct URL Format

Correct:

https://xxxx.ngrok-free.app/mcp/

Wrong:

https://xxxx.ngrok-free.app
https://127.0.0.1:27124/mcp/
http://127.0.0.1:3000/mcp/

Why:

• ChatGPT cannot access your local 127.0.0.1.
• ChatGPT needs a public HTTPS URL.
• ngrok gives that public HTTPS URL.

Validation Flow

flowchart TD
    A[Start Obsidian] --> B[Test https://127.0.0.1:27124]
    B --> C[Start Proxy on Port 3000]
    C --> D[Test http://127.0.0.1:3000]
    D --> E{authenticated true?}
    E -->|No| F[Check API key in .env]
    E -->|Yes| G[Start ngrok to port 3000]
    G --> H[Copy HTTPS ngrok URL]
    H --> I[Add /mcp/]
    I --> J[Create ChatGPT App with No Auth]
    J --> K[Use Obsidian from ChatGPT]

Troubleshooting

Problem 1: ChatGPT Shows OAuth Fields

Meaning: ChatGPT is asking for OAuth setup.

Fix: Do not use OAuth. Use:

Authentication = No Auth

The proxy handles the Obsidian API key.

Problem 2: ngrok Shows Requests to /.well-known/... with 404

Example:

GET /.well-known/oauth-authorization-server 404
GET /.well-known/openid-configuration 404
GET /.well-known/oauth-protected-resource 404

Meaning: ChatGPT is trying OAuth discovery.

Fix: Set ChatGPT Authentication to No Auth and confirm the server URL ends with:

/mcp/

Problem 3: ngrok Shows POST / 404

Meaning: ChatGPT is calling the root path instead of the MCP path.

Fix: Your ChatGPT URL is probably missing /mcp/.

Use:

https://xxxx.ngrok-free.app/mcp/

Do not use:

https://xxxx.ngrok-free.app

Problem 4: Proxy Test Does Not Show authenticated: true

Run:

curl.exe http://127.0.0.1:3000/

If output shows:

"authenticated": false

Check:

• Is Obsidian open?
• Is Local REST API enabled?
• Is the API key correct in .env?
• Did you restart npm start after changing .env?

Problem 5: PowerShell Says curl -k Is Invalid

PowerShell treats curl as Invoke-WebRequest.

Use:

curl.exe -k https://127.0.0.1:27124/

Do not use:

curl -k https://127.0.0.1:27124/

Problem 6: MCP Endpoint Says Client Must Accept text/event-stream

Example error:

{"jsonrpc":"2.0","error":{"code":-32000,"message":"Not Acceptable: Client must accept text/event-stream"},"id":null}

Meaning: This is actually good. It means the MCP endpoint exists and expects event streaming.

Fix for manual testing:

curl.exe http://127.0.0.1:3000/mcp/ -H "Accept: text/event-stream"

Stop Everything Safely

To stop the proxy:

Go to the proxy PowerShell window and press Ctrl+C.

To stop ngrok:

Go to the ngrok PowerShell window and press Ctrl+C.

To fully shut down:

• [ ] Stop ChatGPT usage.
• [ ] Stop ngrok.
• [ ] Stop proxy.
• [ ] Close Obsidian if not needed.

Security Rules

Treat the ngrok URL like a temporary doorway into your Obsidian vault.

• Do not share the ngrok URL.
• Stop ngrok when not using it.
• Stop the proxy when not using it.
• Do not upload .env to GitHub.
• Do not expose this permanently without stronger authentication.
• Keep Obsidian vault backups.
• Avoid enabling destructive tools like delete, move, or rename until you are comfortable.

Mental Model

flowchart LR
    A[Wrong Idea] --> B[Paste API key into OAuth fields]
    C[Correct Idea] --> D[Use No Auth in ChatGPT]
    D --> E[Proxy adds API key]
    E --> F[Obsidian accepts request]

Quick Command Cheat Sheet

Start proxy:

cd "C:\Projects\chatgpt-obsidian-mcp-proxy"
npm start

Test proxy:

curl.exe http://127.0.0.1:3000/

Start ngrok:

ngrok http http://127.0.0.1:3000

ChatGPT URL format:

https://YOUR-NGROK-URL.ngrok-free.app/mcp/

ChatGPT Authentication:

No Auth

Final Success Checklist

• [ ] Obsidian is open.
• [ ] Local REST API plugin is enabled.
• [ ] .env contains the correct Obsidian API key.
• [ ] Proxy is running on port 3000.
• [ ] curl.exe http://127.0.0.1:3000/ shows authenticated: true.
• [ ] ngrok is forwarding to http://127.0.0.1:3000.
• [ ] ChatGPT server URL ends with /mcp/.
• [ ] ChatGPT Authentication is No Auth.
• [ ] ChatGPT connector creates successfully.

Final Target State

ChatGPT
  -> ngrok HTTPS URL /mcp/
  -> Local proxy on port 3000
  -> Obsidian Local REST API on port 27124
  -> Obsidian vault notes

Once this works, ChatGPT can help maintain notes, study plans, CTI dashboards, SOC investigation templates, and learning logs directly inside Obsidian.

Full Runbook

See docs/runbook.md for the repo-maintained setup runbook.