obsidian-vault-mcp

Multi-tenant remote MCP server that exposes any GitHub-backed Obsidian vault to any MCP client (Claude iOS, Claude Code, Hermes, etc.). Users authenticate with their own GitHub account via OAuth and pick which repo to use as their vault — no per-user secrets are baked into the server.

How it works

1. User adds the server URL to their MCP client.

2. First request returns 401 with a WWW-Authenticate pointing at /.well-known/oauth-protected-resource.

3. Client discovers the OAuth Authorization Server metadata, registers itself (Dynamic Client Registration, RFC 7591), and starts an Authorization Code flow with PKCE.

4. The Lambda redirects the user to GitHub's OAuth consent screen.

5. After GitHub callback, the Lambda renders a small page where the user picks which of their repos to use as the vault.

6. The Lambda issues an MCP access + refresh token; the GitHub user token and repo selection are stored in DynamoDB keyed by the access token.

7. MCP calls then operate against that repo using the user's GitHub token.

Token lifetimes: access 1h, refresh 30d, auth codes 10m, repo picker 30m.

Tools exposed

• list_files — list a directory in the vault

• read_file — read a markdown file (text) or image (MCP image content)

• write_file — create or update a file; encoding: "utf-8" | "base64"

• search — GitHub code search scoped to the user's selected vault repo

One-time setup: GitHub OAuth App

1. github.com → Settings → Developer settings → OAuth Apps → New OAuth App.

2. Homepage URL: anything (e.g. the repo URL).

3. Authorization callback URL: leave as a placeholder for now; you'll set the real value after the first cdk deploy (it's printed as a stack output).

4. Save. Note the Client ID (public) and generate a new Client secret (treat as sensitive).

Deploy

npm install
cd lambda && npm install && cd ..

export GITHUB_OAUTH_CLIENT_ID=Iv1.xxxxxxxxxxxx
npx cdk bootstrap   # first time per account/region
npx cdk deploy

The stack prints:

• McpEndpoint — the URL clients connect to

• GitHubCallbackUrl — paste this back into the OAuth App's "Authorization callback URL" field

• GitHubOAuthClientSecretParam — the SSM Parameter Store name where the OAuth App's client secret must be stored

• SessionTableName — the DynamoDB table holding sessions, codes, and tokens

Set the OAuth App client secret in SSM Parameter Store:

aws ssm put-parameter \
  --name /obsidian-vault-mcp/github-oauth-client-secret \
  --value 'your_oauth_app_client_secret' \
  --type SecureString

(Use --overwrite if you ever need to rotate it.)

Continuous deploy via GitHub Actions

The repo ships with .github/workflows/deploy.yml which runs cdk deploy on every push to main, authenticating to AWS via GitHub OIDC (no long-lived access keys in GitHub secrets).

One-time setup:

1. Deploy the OIDC stack with local credentials:

   npx cdk deploy ObsidianVaultMcpOidcStack

   If your account already has a GitHub Actions OIDC provider, pass the existing ARN:

   npx cdk deploy ObsidianVaultMcpOidcStack \
     -c existingGitHubOidcProviderArn=arn:aws:iam::<acct>:oidc-provider/token.actions.githubusercontent.com

2. Copy the DeployRoleArn output.

3. In the GitHub repo's Settings → Secrets and variables → Actions:

   • Secret AWS_DEPLOY_ROLE_ARN = the role ARN from step 2

   • Variable AWS_REGION = the region you're deploying to

   • Variable OAUTH_CLIENT_ID = your OAuth App's Client ID

After that, every push to main triggers a deploy.

Client setup

In any MCP client that supports remote MCP + OAuth, add the McpEndpoint URL (or its /mcp sub-path) as a server. The client handles the rest of the OAuth dance and pops a browser for GitHub login and repo selection.

Repo permissions

The OAuth flow requests the repo scope so users can pick public or private repos. Tokens are stored encrypted at rest in DynamoDB (AWS-managed KMS). Each user only ever sees their own data; the server has no global vault.