Lobstack vs Sim
An open-source workspace for building, deploying and managing AI agents, on a visual canvas, in chat or in code.
Sim is a hosted or self-hosted place to build agent workflows on a canvas, with cost per run in its logs. Lobstack is a desktop app where bots work on your own computer and stop for your yes before each change.
Ten questions, answered from each side’s own pages.
| Lobstack | Sim | |
|---|---|---|
| What it is | A desktop app where AI bots work in your repos and tools and wait for your yes, plus an API with a receipt on every call. | An open-source AI workspace for building and running AI agents. |
| Where it runs | On your computer: Windows, macOS and Linux. Public beta, not code-signed yet. Prompts go to the model. | Sim's cloud, or your own with Docker or Kubernetes. The desktop app is macOS-only. |
| How you build | Give a bot a job in plain words and it proposes the steps. A finished run can become a routine. There is no visual canvas. | A visual canvas, a chat, or code. |
| Apps and integrations | 36 built-in connectors, plus 2 generic ones that reach any MCP server by URL or command. | 1,000+ integrations and every major model, per its README. |
| Approval before an action | On by default. Every step that changes something waits for your yes, with the exact call in front of you. | A Human in the Loop block you add where a run should pause for a person. |
| Scheduled runs | Routines run on a schedule, but only while the app is running. A closed laptop runs nothing. | A Schedule trigger, on an interval or a cron expression. |
| MCP | Connectors are MCP servers. Add any HTTP or stdio MCP server. | Agents can use MCP tools, and a deployed workflow can answer as one. |
| Your own model key | Yes. Your own provider key or GitHub Copilot work instead of the Lobstack API, with no Lobstack account. | Yes. With your own keys you pay the provider; Sim's base charge per run still applies. |
| How usage is counted | Dollars of model spend. Each call on the Lobstack API returns what it cost, and calls can be tagged by client. | Credits, at $0.005 each. Logs show each run's cost, block by block. |
| Free tier and entry price | Free to download. $5 of credit for 30 days on first sign-in, then $1 a month of model spend. Paid plans from $29 a month. | Free: 1,000 one-time credits. Pro: $25 per user a month. |
As of 2026-09-30. The Sim column is read from Sim’s own pages, each listed with a quote under Sources. Prices and plans change; check them before you decide.
What Sim does that we do not.
Open source, and you can host it
The code is under Apache 2.0 and there is an installer for your own servers. If your rule is that the tool must run inside your own cloud, Sim can.
A canvas you can see
Each agent is a graph of blocks you can read, edit and share. Lobstack has no canvas: a bot proposes steps in a thread.
Runs while you are away
Workflows run on Sim's servers or yours, on a schedule, from a webhook or through an API. Lobstack's routines only run while the app is open.
Cost per run, in the logs
Sim traces every run block by block with its cost. We are not the only ones who show what a run spent.
Built for teams
Workspaces, permission groups and spend limits, and its Trust Center lists SOC 2 Type II. We make no such claim.
Pick the one that fits the job.
Choose Sim if
- You want to build agents on a visual canvas and share them as workflows.
- The work must run on a server, on a schedule or from a webhook, with your computer off.
- You need to host it yourself, from open-source code.
- Your team works on Windows or Linux in the browser. Sim's desktop app is macOS-only.
Choose Lobstack if
- You want bots working on your own computer, in your repos, files and browser.
- Every change should wait for your yes by default, not only where you added a step.
- You want a desktop app on Windows, macOS or Linux.
- You would rather describe a job than wire up blocks.
What people ask.
- Is Lobstack a replacement for Sim?
- Not if you need workflows running on a server. Sim runs agent workflows in its cloud or yours. Lobstack runs bots on your computer and asks before each change, and its routines stop when the app does.
- Both have a desktop app. What is the difference?
- Sim's desktop app is macOS-only and signs in to Sim's cloud or your own Sim server. Lobstack is a desktop app first, on Windows, macOS and Linux, and keeps your bots, notes and history in one folder on your disk.
- Can I bring my own model key to both?
- Yes. On Sim you pay the provider directly and Sim's base charge per run still applies. On Lobstack, your own provider key or GitHub Copilot work without a Lobstack account.
- Which one shows what a run cost?
- Both. Sim's logs show each run's cost block by block. Every call on the Lobstack API returns what it cost, and calls can be tagged by client for a monthly statement.
Every page we read, and when.
- sim.ai/pricing
What it is · Free tier and entry price · read 2026-09-30
“Sim is the open-source AI workspace where teams build, deploy, and manage AI agents.”
“$25 per user/month, billed monthly”
- sim.ai
Where it runs · How you build · Run logs with cost, and the Trust Center listing · read 2026-09-30
“Run Sim in your own cloud with Docker or Kubernetes.”
“Create and deploy agents through chat, a visual canvas, or code.”
“Trace every agent run block by block, including actions, cost, and failures.”
- github.com/simstudioai/sim/blob/main/README.md
Apps and integrations · The licence, and the self-host installer · read 2026-09-30
“Connect 1,000+ integrations and every major LLM”
“This project is licensed under the Apache License 2.0”
- docs.sim.ai/workflows/blocks/human-in-the-loop
Approval before an action · read 2026-09-30
“pauses a run and waits for a person before it continues.”
- docs.sim.ai/workflows/triggers/schedule
Scheduled runs · read 2026-09-30
“on a simple interval or a cron expression”
- docs.sim.ai/llms.txt
MCP · read 2026-09-30
“the same Start block answers calls as an API, a chat, or an MCP tool.”
- docs.sim.ai/platform/costs
Your own model key · How usage is counted · read 2026-09-30
“With your own keys, you pay the provider directly”
“1 credit = $0.005”
- docs.sim.ai/desktop
The desktop app's platforms · read 2026-09-30
“The desktop app is macOS-only today.”
- Lobstack’s column
Each line restates a page on this site: /download, /docs/app, /connectors, /docs/app#approval, /docs/app#routines, /docs/app#connectors, /docs/console/clients, /pricing.
Download Lobstack.
Free for Windows, Mac and Linux, in public beta. Bots work on your computer and wait for your yes before anything that changes something.