Caspian vs Linq

Caspian supports 33 of the 77 features compared here, and Linq supports 63.

Feature comparison

Feature	Caspian	Linq
iMessage messaging
iMessage	PartialSelf-host only, through a BlueBubbles-style relay on your own Mac; not live on the hosted gateway	Supported
Group chats	PartialPython adapter can send to a group chat GUID; inbound messages are keyed to the sender as DMs	SupportedPro plan. Up to 31 recipients. No read or delivery receipts in groups.
Group management	Not listed	SupportedAdd and remove participants and leave a group, iMessage groups only, 3-member minimum.
Group name and photo	Not listed	SupportedSet display_name and group_chat_icon on group chats.
Mentions	Not listed	SupportedGroup chats only. Notifies iMessage recipients even in a muted chat.
Tapbacks	PartialPython adapter sends reactions through the relay; the TypeScript adapter sends text only	SupportedSix classic tapbacks or any emoji, send and receive via reaction webhooks.
Threaded replies	PartialPython adapter replies to a message GUID through the relay	Supportedreply_to with optional part_index. iMessage only.
Typing indicators	Not supportediMessage example says no typing, edit, delete, buttons or pins	SupportedSend and receive, in direct and group chats. iMessage only.
Read receipts	Not listed	SupportedMark chats read and receive message.read. One-to-one chats only.
Edit and unsend	Not supportediMessage example says no edit or delete	PartialEdit text up to 5 times within 15 minutes. Delete does not unsend from the recipient's device.
Message effects	Not listed	Supported11 screen and 4 bubble effects.
Animated text effects	Not listed	Supportedtext_decorations animations: big, small, shake, nod, explode, ripple, bloom, jitter.
Stickers	Not listed	SupportedPeel emoji or images onto messages, send stickers, or place them inline in text.
Formatted text	Not supportedThe iMessage adapter treats iMessage as plain text	SupportedBold, italic, underline and strikethrough ranges, plus animated text. iMessage only.
Attachments	PartialPython adapter sends media by URL; inbound attachments are not parsed	SupportedUp to 10MB by URL, 100MB with pre-upload.
Live Photos	Not listed	Not listed
Rich link previews	Not listed	Supportedlink parts render as rich previews on iMessage and RCS.
Voice messages	Not listed	SupportedDedicated voice memo endpoint renders the native iMessage voice bubble.
Contact cards	Not listed	SupportedSend .vcf files as media parts.
Polls	Not listed	SupportedCreate, add options, vote and read tallies, with poll webhooks. Not as a chat's first message.
Chat backgrounds	Not listed	SupportedColor, animated or photo backgrounds, in direct and group chats.
Location sharing	Not listed	SupportedRequest, read and stop Find My shares. Live location is a $79/mo add-on on Pro.
iMessage apps	Not listed	SupportedPro plan. Cards from your own Messages extension, or Linq-hosted cards (Experiences).
Live app cards	Not listed	SupportedUpdate App Card replaces a delivered iMessage app or Experience card in place.
Sender name and photo	Not listed	SupportedContact card API sets name and photo, shared per chat via Name and Photo Sharing.
FaceTime calls	Not listed	Not supportedDocs say the API does not place or answer calls.
Delivery status	Not listed	Supportedsent, delivered, read and failed webhooks. Groups report sent only.
iMessage availability check	Not listed	Supportedcheck_imessage and check_rcs endpoints.
Focus and Notify Anyway	Not listed	Not listed
Numbers and delivery
Managed lines	Not listedSite lists iMessage on the hosted gateway; the live channel list (Oct 2026) does not include it	Supported
Dedicated numbers	Not listedHosted SMS uses your own Twilio or Telnyx number; no Caspian numbers in the live list	SupportedPaid lines are dedicated. Provisioned by Linq, no self-serve number API.
Shared numbers	Not listed	SupportedFree Hobby tier uses a Shared Line, inbound-first, 20 contacts.
Bring your own number	SupportedYour own Twilio or Telnyx number for SMS, and your own Mac and Apple ID for iMessage	Not listed
Line pooling	Not listed	SupportedManaged load balancing (Pro): send without from and Linq picks and fails over lines.
SMS fallback	Not listed	Supported
RCS fallback	Not listed	SupportedOrder is iMessage, then RCS, then SMS.
Outbound-first messaging	Supportedinitiate and send start conversations on channels that allow it, SMS included	SupportedFree Hobby tier is inbound-first. Docs recommend inbound-first flows to avoid flagging.
Calls on the iMessage number	Not listed	PartialAPI forwards inbound calls on the line; outbound needs caller-ID masking via another provider.
Other channels
SMS	SupportedBring your own Twilio or Telnyx number, hosted or self-hosted	Supported
RCS	Not listedSite lists RCS on the hosted gateway; not in the live channel list or the SDK catalog	Supported
WhatsApp	PartialSelf-host adapter with your own Meta WhatsApp Business app; not live on the hosted gateway	BetaSeparate WhatsApp API in beta. Access by request, no SLA.
Telegram	SupportedYour own BotFather token, hosted or self-hosted	Not supportedNot offered
Slack	SupportedShared Caspian app install on hosted, or your own tokens self-hosted	Not supported
Email	SupportedInstant hosted inboxes at agents.trycaspianai.com, or self-hosted	Not supportedNot offered. iMessage can be sent to Apple ID email handles.
Phone calls	PartialSelf-host Twilio voice adapter with TwiML; not live on the hosted gateway	PartialAPI does not place or answer calls; it forwards inbound calls. Calling lives in the Linq Blue app.
Apple Messages for Business	Not supportedNot offered	Not listedAI context page mentions it, but no product page or docs were found.
Unified channel API	SupportedOne handler and one Thread and Message model across all channels	PartialiMessage, RCS and SMS share one API. WhatsApp is a separate API with its own keys and SDKs.
Developer tools
REST API	SupportedHosted gateway /v1 API with bearer auth	Supported
TypeScript SDK	Supportedcaspian-sdk on npm (MIT)	Supported@linqapp/sdk
Python SDK	Supportedcaspian-sdk on PyPI	Supportedlinq-python
Other SDKs	Not supportedPython and TypeScript only	SupportedOfficial Go SDK.
CLI	Supportedcaspian CLI: init, channels add, catalog, call, threads tail	Supported@linqapp/cli: signup, sending, and a local webhook listener.
Webhooks	SupportedHosted gateway POSTs events to your URL, or your process polls them	Supported
Signed webhooks	SupportedHMAC-SHA256 in X-Caspian-Signature; platform signatures are verified too	SupportedHMAC-SHA256, Standard Webhooks format, with replay protection.
MCP server	SupportedHosted at api.trycaspianai.com/mcp; get_started mints a free sandbox key	Supported@linqapp/sdk-mcp with docs search and code execution tools.
Open source	SupportedSite says MIT clients and AGPL server; root LICENSE is AGPL-3.0, README says Apache-2.0	PartialSDKs, CLI and adapters are Apache-2.0 or MIT on GitHub. The messaging platform is closed.
Self-hosting	SupportedAdapters run in your own process; the AGPL gateway server is in the repo	Not supportedLinq describes itself as fully managed, in contrast to self-hosted options.
Local testing	SupportedOffline fakes for every channel; handler rules are testable with no network	Not listedThe CLI streams webhooks locally, but tests still use a real phone.
Custom channel providers	SupportedSmall adapter interface for new channels; contributed adapters are invited	Not listed
Event replay	PartialHosted events are polled by cursor; docs say to persist your own cursor across restarts	PartialRetries for 30 minutes; after that, re-fetch chats or ask Linq for a manual replay.
OpenTelemetry	Not listed	PartialW3C trace IDs on every response and webhook for OTel backends. No export of Linq spans by default.
No-code integrations	Not listed	SupportedLinq Blue works as a GoHighLevel messaging provider. No n8n, Make or Zapier found for the API.
CRM integrations	Not listed	SupportedVia Linq Blue: GoHighLevel, HubSpot and Salesforce.
Built for AI agents
Agent framework	SupportedDeclarative on_message rules, overlap policies, acks and thread replies	PartialNo own framework. Maintains a Vercel Chat SDK adapter and OpenClaw and Hermes plugins.
Agent framework integrations	SupportedGuides for OpenAI Agents SDK, LangChain, LangGraph, CrewAI, Mastra, Vercel AI and more	SupportedLinq-maintained Vercel Chat SDK adapter, plus OpenClaw and Hermes Agent plugins.
Streaming replies	PartialPosts then edits as text arrives; one final post where a channel cannot edit, as on iMessage	Not supportedDocs say the Chat SDK adapter buffers streams into one final message.
Agent group chats	Not listed	Not listed
Human handoff	Not listed	Not listed
Audit logs	Not listed	SupportedDashboard Activity page plus account-change webhooks with actor and origin.
Message history API	Supportedread_conversation MCP tool returns the full thread; threads tail in the CLI	Supported
Plans and compliance
Free plan	SupportedSelf-hosting is free; the MCP get_started tool mints a free sandbox key	SupportedHobby: $0, up to 20 contacts, through the CLI.
Public pricing	PartialNo pricing page; per-message costs appear in the open-source gateway code	SupportedPro from $260/mo. Enterprise is custom.
No per-message fees	Not supportedPaid channels are billed per message from prepaid credit	Supported
Uptime SLA	Not listed	SupportedContractual SLAs on the Enterprise plan; marketing cites 99.95%
Isolated infrastructure	SupportedSelf-host mode runs every adapter in your own process	SupportedDedicated lines across 4 data centers on paid plans; Hobby uses a shared line
SOC 2 Type II	Not listed	SupportedType I and Type II, reports for 2022, 2024, 2025 and 2026.
GDPR	Not listed	SupportedDPA covers GDPR and UK GDPR, with Standard Contractual Clauses.

Checked on each provider's own site and docs on 2026-10-25. “Not listed” means the provider does not mention it.

Pricing

Which should you choose?

Choose Caspian if you need bring your own number, Telegram, Slack and email.

Choose Linq if you need group management, group name and photo, mentions and typing indicators.

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