Caspian

Overview

The Caspian SDK is an open-source agent communication SDK from Caspian (SaaSDen, Inc.). You write one message handler, and it answers on Slack, Discord, Telegram, email, X, Linear, SMS and more, either self-hosted with your own platform tokens or through Caspian's hosted gateway. iMessage, WhatsApp and voice adapters ship for self-hosting. The repo is github.com/TryCaspian/caspian-sdk: the root license is AGPL-3.0, the site describes MIT clients and an AGPL server, and the README says Apache-2.0. Version 1.0 shipped in August 2026; the last commit was on 25 August.

Key features

• Python and TypeScript SDKs with the same handler model, plus a CLI
• Self-host adapters for iMessage through a BlueBubbles-style relay on your own Mac, Twilio SMS and voice, and Meta WhatsApp
• Hosted gateway with email inboxes, Slack, Discord, Telegram, X, Bluesky, Zulip, Linear, and SMS on your own Twilio or Telnyx number
• Streaming replies that post once and edit as text arrives, on channels that can edit
• HMAC-signed event webhooks or cursor-based polling
• Hosted MCP server that mints a free sandbox key
• Setup guides for OpenAI Agents SDK, LangChain, LangGraph, CrewAI, Mastra and Vercel AI SDK

Pricing

Self-hosting is free. The hosted gateway runs on prepaid credit and has no pricing page; the open-source gateway code bills paid channels per message at provider cost, such as $0.01 per outbound iMessage and $0.005 per WhatsApp message. Your own Twilio number, Telegram, Slack and Discord cost nothing.

How it compares to Linq

Linq runs managed iMessage, RCS and SMS lines for you. Caspian's iMessage path is self-hosted: you run the relay on your own Mac. Its site lists iMessage, WhatsApp, voice and RCS on the hosted gateway, but the gateway's live channel list on 25 October 2026 did not include them. Caspian covers Slack, Discord, Telegram and email, which Linq does not offer, and its code is open source while Linq's platform is closed.

Best for

Teams whose agent must answer on chat apps and email from one handler, and who can run a Mac relay for iMessage.

Sources

• trycaspianai.com
• trycaspianai.com/llms.txt
• trycaspianai.com/docs/index.html
• trycaspianai.com/docs/channels.html
• trycaspianai.com/docs/messaging.html
• trycaspianai.com/docs/webhooks.html
• trycaspianai.com/docs/api-rest.html
• trycaspianai.com/docs/serverless.html
• trycaspianai.com/docs/streaming.html
• trycaspianai.com/docs/mcp.html
• api.trycaspianai.com/SKILL.md
• api.trycaspianai.com/v1/channels
• github.com/TryCaspian/caspian-sdk
• github.com/TryCaspian/caspian-sdk/tree/main/examples/imessage
• github.com/TryCaspian/caspian-sdk/blob/main/packages/python/src/caspian/adapters/imessage/init.py
• github.com/TryCaspian/caspian-sdk/blob/main/server/src/comm_gateway/providers/macmini_imessage.py
• github.com/TryCaspian/caspian-sdk/blob/main/server/src/comm_gateway/routes/usage.py
• github.com/TryCaspian/caspian-sdk/blob/main/LICENSE
• npmjs.com/package/caspian-sdk
• pypi.org/project/caspian-sdk