GroundEffect

Hyper-fast, local Gmail and Google Calendar indexing for Claude Code.

GroundEffect is a local headless IMAP/CalDav client, Claude Code skill, and MCP server built in Rust with LanceDB.

Features

• Hybrid Search: BM25 full-text + vector semantic search with Reciprocal Rank Fusion
• Local Embeddings: Runs nomic-embed-text-v1.5 locally via Candle with Metal acceleration
• Multi-Account: Connect unlimited Gmail/GCal accounts with independent sync
• MCP Integration: Exposes email and calendar tools directly to Claude Code
• Real-time Sync: IMAP IDLE for instant email notifications, CalDAV polling for calendar
• HTML Text Extraction: Automatically converts HTML emails to clean plain text using html2text
• Pluggable Token Storage: File-based (default) or PostgreSQL with AES-256-GCM encryption

Quick Start

1. Install

brew tap jamiequint/groundeffect
brew install groundeffect

This automatically:

• Installs the daemon (starts at login)
• Installs the Claude Code skill
• Adds permissions to run groundeffect commands

2. Configure OAuth

Create a Google Cloud project with OAuth credentials:

1. Go to Google Cloud Console
2. Create a project and enable Gmail API and Google Calendar API
3. Go to APIs & Services > Credentials
4. Create OAuth client ID (Desktop app type)
5. Add your credentials:

echo 'export GROUNDEFFECT_GOOGLE_CLIENT_ID="your-client-id.apps.googleusercontent.com"' >> ~/.zshrc
echo 'export GROUNDEFFECT_GOOGLE_CLIENT_SECRET="your-client-secret"' >> ~/.zshrc
source ~/.zshrc

3. Add an Account

groundeffect account add

This opens a browser for Google OAuth. After authentication, the daemon syncs automatically.

That's it! Ask Claude Code to search your emails and calendar.

CLI Reference

All commands output JSON by default. Add --human for readable output.

Account Commands

Command	Description
account list	List all connected accounts
account show <account>	Show account details and sync status
account add	Add new Google account via OAuth
account reauth <account>	Re-authenticate an existing account via OAuth
account delete <account>	Remove account and all synced data
account configure <account>	Update account settings (alias, attachments)

Parameters for add:

Parameter	Description	Default
--years	Years of email history to sync (1-20 or "all")	1
--attachments	Enable automatic attachment download	off
--alias	Friendly name for the account	-

Email Commands

Command	Description
email search <query>	Hybrid BM25 + semantic search
email list	List recent emails
email show <id>	Show full email content
email thread <thread_id>	Show all emails in a thread
email send	Compose and send email
email attachment <id>	Get attachment content
email folders	List IMAP folders

Parameters for search:

Parameter	Description	Default
--account	Filter to specific account	all
--limit	Max results (max: 100)	10
--from	Filter by sender	-
--to	Filter by recipient	-
--date-from	Filter after date (YYYY-MM-DD)	-
--date-to	Filter before date (YYYY-MM-DD)	-
--has-attachment	Filter emails with attachments	-

Parameters for send:

Parameter	Description
--from	Account to send from (required)
--to	Recipient(s) (required)
--subject	Email subject (required)
--body	Email body (required)
--cc	CC recipients
--bcc	BCC recipients
--reply-to	Email ID to reply to (for threading)
--html	Force HTML format (auto-detected from markdown/URLs)
--save-as-draft	Save as draft instead of sending
--confirm	Send immediately (without: preview only)

Draft Commands

Command	Description
email draft create	Create a new email draft
email draft list	List all drafts for an account
email draft show <id>	Show full draft content
email draft update <id>	Update an existing draft
email draft send <id>	Send a draft
email draft delete <id>	Delete a draft

Parameters for draft create:

Parameter	Description
--from	Account to create draft in (required)
--to	Recipient(s)
--subject	Email subject
--body	Email body
--cc	CC recipients
--bcc	BCC recipients
--html	Force HTML format
--reply-to	Email ID to reply to (for threading)

Calendar Commands

Command	Description
calendar events	List events in a date range (no query required)
calendar search <query>	Search events with semantic search
calendar show <id>	Show event details
calendar create	Create new event

Parameters for events:

Parameter	Description	Default
--from	Start date (YYYY-MM-DD)	today
--to	End date (YYYY-MM-DD)	7 days from start
--account	Filter to specific account(s)	all
--limit	Max results (max: 200)	50
--human	Human-readable output grouped by date	-

Use calendar events to answer questions like "what's on my calendar tomorrow" or "show me my meetings next week" without requiring a search query.

Parameters for create:

Parameter	Description	Default
--account	Account to create event in (required)	-
--summary	Event title (required)	-
--start	Start time (ISO 8601) (required)	-
--end	End time (ISO 8601) (required)	-
--description	Event description	-
--location	Event location	-
--attendees	Attendee emails (repeatable)	-
--calendar	Calendar ID	primary

Sync Commands

Command	Description
sync status	Show sync status for all accounts
sync reset --account <a> --confirm	Clear all synced data
sync extend --account <a> --target-date <d>	Sync older emails back to date
sync resume-from --account <a> --target-date <d>	Force sync to resume from date
sync download-attachments --account <a>	Download pending attachments

Daemon Commands

Command	Description
daemon install	Install launchd agent (auto-start at login)
daemon uninstall	Remove launchd agent
daemon status	Check if daemon is running
daemon restart	Restart the daemon

Config Commands

Command	Description
config settings	View/modify daemon settings
config add-permissions	Add to Claude Code allowlist
config remove-permissions	Remove from Claude Code allowlist

Parameters for settings:

Parameter	Description	Default
--logging	Enable/disable file logging	off
--email-interval	Email poll interval in seconds (60-3600)	300
--calendar-interval	Calendar poll interval in seconds (60-3600)	300
--max-fetches	Max concurrent fetches (1-50)	10
--timezone	User timezone for date parsing (e.g., America/Los_Angeles)	UTC
--embedding-provider	Embedding backend: local, openrouter, remote	local
--embedding-batch-size	Embedding + IMAP fetch batch size (1-1024)	128
--openrouter-model	OpenRouter embedding model ID	openai/text-embedding-3-small
--openrouter-api-key-env	Env var name with OpenRouter API key	OPENROUTER_API_KEY

Embeddings backend examples:

# Use local embeddings (default)
groundeffect config settings --embedding-provider local

# Use OpenRouter embeddings
export OPENROUTER_API_KEY="your-key"
groundeffect config settings --embedding-provider openrouter

# Set embedding + IMAP fetch batch size (128 recommended for Gmail/OpenRouter stability)
groundeffect config settings --embedding-batch-size 128

# Optional: set a different OpenRouter model
groundeffect config settings --openrouter-model "openai/text-embedding-3-large"

MCP Integration (Alternative)

If you prefer MCP over the CLI skill, add to ~/.claude.json:

{
  "mcpServers": {
    "groundeffect": {
      "type": "stdio",
      "command": "groundeffect-mcp",
      "env": {
        "GROUNDEFFECT_GOOGLE_CLIENT_ID": "${GROUNDEFFECT_GOOGLE_CLIENT_ID}",
        "GROUNDEFFECT_GOOGLE_CLIENT_SECRET": "${GROUNDEFFECT_GOOGLE_CLIENT_SECRET}"
      }
    }
  }
}

The skill is faster (direct CLI calls vs MCP JSON-RPC overhead) but MCP works with other MCP-compatible clients.

Build from Source

git clone https://github.com/jamiequint/groundeffect.git
cd groundeffect
cargo build --release

Binaries:

• target/release/groundeffect - CLI
• target/release/groundeffect-daemon - Background sync daemon
• target/release/groundeffect-mcp - MCP server

Install manually:

# Install binaries
sudo cp target/release/groundeffect* /usr/local/bin/

# Install skill
cp -r skill ~/.claude/skills/groundeffect

# Install daemon
groundeffect daemon install

# Add permissions
groundeffect config add-permissions

Data Storage

~/.config/groundeffect/
├── config.toml            # Main configuration
├── daemon.toml            # Daemon configuration
└── tokens/                # OAuth tokens (file provider)

~/.local/share/groundeffect/
├── lancedb/               # LanceDB database
├── attachments/           # Downloaded attachments
├── models/                # Embedding model files
├── logs/                  # Log files
└── cache/
    └── sync_state/        # Sync state

~/.claude/skills/groundeffect/   # Claude Code skill

Token Storage

By default, OAuth tokens are stored in ~/.config/groundeffect/tokens/ as encrypted JSON files.

For server deployments or ephemeral containers, you can store tokens in PostgreSQL instead. This requires the postgres feature.

PostgreSQL Token Storage

1. Build with the postgres feature:

   cargo build --release --features postgres
   

2. Create the tokens table:

   CREATE TABLE IF NOT EXISTS groundeffect_tokens (
       email VARCHAR(255) PRIMARY KEY,
       encrypted_tokens BYTEA NOT NULL,
       created_at TIMESTAMPTZ NOT NULL DEFAULT NOW(),
       updated_at TIMESTAMPTZ NOT NULL DEFAULT NOW()
   );
   

3. Configure in ~/.config/groundeffect/config.toml:

   [tokens]
   provider = "postgres"
   database_url_env = "DATABASE_URL"
   encryption_key_env = "GE_TOKEN_ENCRYPTION_KEY"
   # table_name = "groundeffect_tokens"  # optional
   

4. Set environment variables:

   export DATABASE_URL="postgres://user:pass@localhost/mydb"
   export GE_TOKEN_ENCRYPTION_KEY="your-secret-key-here"
   

Tokens are encrypted at rest using AES-256-GCM with a key derived from your encryption key via HKDF-SHA256.

Troubleshooting

"OAuth token expired"

Re-authenticate:

groundeffect account reauth <email-or-alias>

Daemon not running

Check status and restart:

groundeffect daemon status
groundeffect daemon restart

Or check launchd:

launchctl list | grep groundeffect

View logs

tail -f ~/.local/share/groundeffect/logs/daemon.log

Enable logging if disabled:

groundeffect config settings --logging true
groundeffect daemon restart

High memory usage

Embedding model uses ~500MB-1GB during active embedding. Normal when idle.

Architecture

┌──────────────┐      ┌──────────────────┐
│ Claude Code  │─────►│ groundeffect-mcp │────────┐
│ (MCP Host)   │stdio │                  │        │
└──────────────┘      └──────────────────┘        │
                                                  ▼
┌──────────────┐      ┌──────────────────┐    ┌─────────┐
│ Claude Code  │─────►│ groundeffect     │───►│ LanceDB │
│ (Skill/Bash) │      │ (CLI)            │    └─────────┘
└──────────────┘      └──────────────────┘         ▲
                                                   │
                      ┌──────────────────┐         │
                      │ groundeffect-    │─────────┘
                      │ daemon           │◄──── IMAP/CalDAV
                      └──────────────────┘

License

MIT