graham.systems
Encrypted, ephemeral, private memos on atproto
docs(mcp): add README
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README.md
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README.md
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## Architecture
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Cistern is a Deno monorepo consisting of five packages:
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Cistern is a Deno monorepo consisting of six packages:
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### `@cistern/crypto`
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locally, retrieves memos via polling or real-time streaming (Jetstream), and
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handles memo deletion after consumption.
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### `@cistern/mcp`
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Model Context Protocol server that exposes Cistern as MCP tools for AI
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assistants. Supports stdio transport for local integrations (Claude Desktop) and
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HTTP transport for remote deployments. Automatically generates and persists
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keypairs in Deno KV.
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## Security Model
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Private keys never leave the consumer device. Public keys are stored in the PDS
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as records, while private keys remain off-protocol. Only the holder of the
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matching private key can decrypt memos encrypted with the corresponding public
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key.
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## Quick Start
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### Using the MCP Server with Claude Desktop
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1. Generate an [app password](https://bsky.app/settings/app-passwords) for your Bluesky account
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2. Add to Claude Desktop config (`~/Library/Application Support/Claude/claude_desktop_config.json`):
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```json
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{
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"mcpServers": {
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"cistern": {
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"command": "deno",
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"args": ["task", "--cwd", "/path/to/cistern/packages/mcp", "stdio"],
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"env": {
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"CISTERN_MCP_HANDLE": "yourname.bsky.social",
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"CISTERN_MCP_APP_PASSWORD": "xxxx-xxxx-xxxx-xxxx"
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}
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}
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}
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}
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```
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3. Restart Claude Desktop
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4. Create memos using the Cistern Producer from any device
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5. Ask Claude to retrieve and process your memos
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See [`packages/mcp/README.md`](./packages/mcp/README.md) for detailed usage.
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## Testing
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# @cistern/mcp
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Model Context Protocol (MCP) server for Cistern, enabling AI assistants to retrieve and manage encrypted memos.
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## Features
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- **Dual Transport Support**: stdio for local integrations (Claude Desktop) and HTTP for remote deployments
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- **Automatic Keypair Management**: Generates and persists keypairs in Deno KV on first launch
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- **Two MCP Tools**:
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- `next_memo`: Retrieve the next outstanding memo
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- `delete_memo`: Delete a memo after handling it
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## Installation
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### Prerequisites
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- Deno 2.0+
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- AT Protocol account with app password
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- Bluesky handle (e.g., `yourname.bsky.social`)
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### Environment Variables
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**Required:**
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```bash
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CISTERN_MCP_HANDLE=yourname.bsky.social
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CISTERN_MCP_APP_PASSWORD=xxxx-xxxx-xxxx-xxxx
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```
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**Optional (for existing keypair):**
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```bash
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CISTERN_MCP_PRIVATE_KEY=base64-encoded-private-key
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CISTERN_MCP_PUBLIC_KEY_URI=at://did:plc:abc.../app.cistern.pubkey/xyz
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```
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**Required for HTTP mode:**
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```bash
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CISTERN_MCP_BEARER_TOKEN=your-secret-bearer-token
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```
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## Usage
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### stdio Mode (Claude Desktop)
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Run the server in stdio mode for local integrations:
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```bash
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cd packages/mcp
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deno task stdio
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```
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Add to Claude Desktop configuration (`~/Library/Application Support/Claude/claude_desktop_config.json`):
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```json
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{
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"mcpServers": {
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"cistern": {
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"command": "deno",
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"args": [
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"task",
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"--cwd",
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"/path/to/cistern/packages/mcp",
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"stdio"
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],
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"env": {
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"CISTERN_MCP_HANDLE": "yourname.bsky.social",
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"CISTERN_MCP_APP_PASSWORD": "xxxx-xxxx-xxxx-xxxx"
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}
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}
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}
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}
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```
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### HTTP Mode (Remote Deployment)
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Run the server in HTTP mode for remote access:
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```bash
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cd packages/mcp
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deno task http
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```
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The server listens on port 8000 by default. Configure your MCP client to connect via HTTP:
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```json
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{
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"url": "http://localhost:8000/mcp",
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"headers": {
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"Authorization": "Bearer your-secret-bearer-token"
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}
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}
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```
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## Keypair Management
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On first launch without `CISTERN_MCP_PRIVATE_KEY` and `CISTERN_MCP_PUBLIC_KEY_URI`, the server will:
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1. Check Deno KV for a stored keypair (keyed by handle)
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2. If not found, generate a new X-Wing keypair
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3. Upload the public key to your PDS as an `app.cistern.pubkey` record
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4. Store the keypair in Deno KV at `./cistern-mcp.db`
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5. Log the public key URI for reference
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The keypair persists across restarts and is isolated per handle.
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### Example First Launch Log
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```
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[cistern:mcp] starting in stdio mode
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[cistern:mcp] no keypair found; generating new keypair for yourname.bsky.social
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[cistern:mcp] generated new keypair with public key URI: at://did:plc:abc123.../app.cistern.pubkey/xyz789
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[cistern:mcp] stored keypair for yourname.bsky.social
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```
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### Example Subsequent Launch Log
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```
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[cistern:mcp] starting in stdio mode
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[cistern:mcp] using stored keypair for yourname.bsky.social
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```
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## MCP Tools
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### `next_memo`
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Retrieves the next outstanding memo from your PDS.
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**Output:**
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```json
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{
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"key": "3kbxyz789abc",
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"tid": "3kbxyz789abc",
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"text": "Remember to buy milk"
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}
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```
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Returns `"no memos remaining"` when all memos have been retrieved.
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### `delete_memo`
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Deletes a memo by record key after it has been handled.
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**Input:**
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```json
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{
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"key": "3kbxyz789abc"
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}
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```
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**Output:**
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```json
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{
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"success": true
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}
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```
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## Development
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### Testing with MCP Inspector
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```bash
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deno task stdio:inspect
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```
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This launches the MCP Inspector UI for interactive testing of the stdio server.
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### Logs
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The server uses LogTape for structured logging:
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- **`[cistern:mcp]`**: Server lifecycle, keypair operations
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- **`[cistern:http]`**: HTTP request/response logs (HTTP mode only)
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## Security
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- **Bearer Authentication**: Required for HTTP mode
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- **Private Keys**: Never transmitted; stored locally in Deno KV
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- **Session Isolation**: Each HTTP session gets its own Consumer instance
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- **CORS**: Configured for MCP protocol headers
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## Limitations
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- **No Keypair Deletion**: The Consumer SDK doesn't currently support deleting public keys from the PDS. If you want to use a different keypair, you can either set `CISTERN_MCP_PRIVATE_KEY` and `CISTERN_MCP_PUBLIC_KEY_URI` environment variables, or delete the `cistern-mcp.db` SQLite files to force regeneration. You'll need to manually delete the old public key record from your PDS using a tool like [pdsls.dev](https://pdsls.dev).