Cassidy AI vs Vellum (2026): which should you pick?

Pick Cassidy AI if

• Fits if you want agents that read your company documents inside Slack or Teams
• Works for small teams on Starter's 3 seats

Look elsewhere if

• Skip it if you want a price, since both plans are behind a demo
• Tight if you grow past Starter: 3 seats, 5 agents and 5 workflows
• Watch out: SSO, audit logs and retention controls are on Business only
• Skip it if you want desktop or phone apps, because there aren't any

Pick Vellum if

• Fits if you want one assistant that keeps your preferences across devices and chat apps
• Works for people who want to read the code or host the open-source runtime themselves

Look elsewhere if

• Skip it if you want free to mean free, as every reply, search and image draws on credits at $1 each
• Not for you if you bank what you don't use: included usage doesn't roll over and bought credits expire after 12 months
• Tight if you're on Windows or Linux, since the Windows app is a dev build and there's no Linux desktop client
• Watch out: the iPhone and Android apps are clients for the cloud assistant and can't run it on the phone
• Pricey if you want a custom subdomain, static IP or priority support, which start at Super for $100 a month

Cassidy AI

• No price is published. Both the Starter and Business plans are reached through Book a demo.
• Starter is listed with 3 seats, 1 workspace, 5 agents, 5 workflows, 10,000 AI credits a month and 30,000 pages of storage.
• SSO, audit logs and data retention controls are listed under Business only.
• Only the browser extension and add-ins run outside the web app; there are no desktop or mobile apps listed.

Vellum

• The Base plan is free to host, but model usage, web search and image generation are paid for in prepaid credits at $1 per credit.
• Included monthly usage does not roll over, and pay-as-you-go credits expire twelve months after purchase.
• The docs describe the Windows app as a dev build tied to Vellum's development environment, and no Linux desktop client is shipped.
• The iOS and Android apps are clients for a cloud assistant; they do not run a local assistant on the phone.

Cassidy AI

Agents

Agents are created in plain language and connected to company sources. They can be used in Slack, Microsoft Teams, Google Chat, a browser extension, Office add-ins, or through an API.

Workflows

Multi-step automations with scheduled and custom triggers, conditional logic, human-in-the-loop approval steps, retries and bulk runs.

Knowledge base

Stores company documents as pages and keeps them in step with sources such as Google Drive and SharePoint. Sync is every 24 hours on Starter and instant on Business.

Meeting recorder

Captures and transcribes meetings so the transcript can feed agents and trigger workflows. Starter gets limited hours.

Model choice

The pricing page lists OpenAI models, Claude models and Google Gemini, with a limited choice on Starter.

Vellum

Long-term memory

The assistant keeps facts, preferences and people in a personal knowledge base and recalls them across conversations. On your own machine the workspace is plain-text files plus a SQLite database.

Skills for your work tools

Built-in skills and OAuth integrations cover Google Workspace, Outlook, Slack, Notion, Linear, GitHub, HubSpot, Asana and Todoist. More skills come from a catalog or are written yourself.

Permission prompts

Sensitive actions such as file access, shell commands or emailing a new contact show an Allow or Deny prompt with a risk badge until you create a trust rule for them.

One assistant on every channel

The same identity, memory and schedules are available from the web, Mac, Windows, iOS and Android apps, a CLI, Telegram, Slack, email, voice and phone calls.

Computer and browser control

The desktop app adds voice input and computer control, and a Chrome extension lets the assistant read open tabs, fill in forms and act on the page in front of you.

Cloud, local or self-hosted

Run it in Vellum Cloud, locally on a Mac or Windows PC, or self-hosted on a Linux host or your own Google Cloud project, bringing your own model API key.

Cassidy AI

Pricing could not be confirmed. See cassidyai.com.

Vellum

• Base$0

  Free forever: a Small cloud machine (1 vCPU, 2 GiB RAM), 6 GiB of storage and managed model access paid for with pay-as-you-go credits.

• Self-hosted$0

  The open-source runtime on your own Mac, Windows PC, Linux host or GCP project, with your own model API key and no platform or machine fees.

• Mighty$30

  per month

  Small machine, 10 GiB of storage and a monthly Mighty Usage allowance. Leaves out the custom subdomain, static IP and priority support.

• CustomFrom $50

  per month

  Pick a machine size, storage tier and optional usage bundle yourself. The minimum is a Medium machine with 10 GiB and no usage bundle.

• Super$100

  per month

  Medium machine (2.5 vCPU, 5 GiB), 30 GiB of storage and Super Usage, plus an assistant email, custom subdomain, static IP and priority support.

• Ultra$200

  per month

  Large machine (4 vCPU, 8 GiB), 60 GiB of storage and Ultra Usage, with the same assistant email, subdomain and support as Super.