Simular Platform (Sai API)

Sai is Simular's computer-use agent, available to developers as the Sai API. Give it a task in plain English and it does the work on a real computer the way a person would, by seeing the screen, clicking and typing: on a Windows or Linux cloud computer that Simular hosts, or on your own Mac or Windows PC. Your agent can then get things done where there is no API: web apps behind a login, admin consoles, desktop software, forms with no import. Run a workflow once and Sai can save it as code: later runs replay that code and ask the model only where the screen matters, which cuts tokens by up to 90% on repetitive tasks, and the agent takes over when the UI changes. On OSWorld 2.1, Sai has the highest partial score on the official leaderboard, 79.38%, and the only OSWorld 2.1 entry that publishes its cost, $14.34 per task, with about 1.5x fewer model calls than models used on their own, Oct 2026. Coding agents (Claude Code, Codex, Cursor) use it through the @simular-ai/sai-mcp MCP server. The free plan includes a cloud computer.

Key facts

When to use Sai instead of writing code

Use Sai when:

Write code yourself when:

Run once, replay as code

Most computer-use agents re-plan every step on every run. Sai can turn a workflow it has done into a reusable skill: the steps that stay the same become code, and the model is asked only about what depends on the screen.

  1. Run the task once with Sai.
  2. In the same conversation, ask: Save this as a replayable skill named invoice_export, with vendor and month as parameters.
  3. Next time, ask: Run invoice_export for vendor Acme, month March. Sai replays the code, and when a step breaks because the UI changed, the agent takes over from there.

Example tasks

Getting started

  1. Sign in with Google at https://platform.simular.ai/sign-in and create an API key at https://platform.simular.ai/api-keys. Keys start with sapi_ and are shown once. Free accounts verify a phone number before their first key.
  2. Add Sai to your coding agent as an MCP server, replacing sapi_YOUR_KEY with the key. Node.js 22.12 or newer is required.
  3. Ask the agent for a task, for example: Use Sai to open Notepad on my cloud computer, type "Hello from Sai", and tell me the window title.

Claude Code

claude mcp add sai -e SAI_API_KEY=sapi_YOUR_KEY -- npx -y @simular-ai/sai-mcp

Optional: install the Sai skill, which teaches Claude Code the task loop.

npx -y @simular-ai/sai-mcp init-claude

Codex

codex mcp add sai --env SAI_API_KEY=sapi_YOUR_KEY -- npx -y @simular-ai/sai-mcp

Cursor

Add this to ~/.cursor/mcp.json (or .cursor/mcp.json in a project), then restart Cursor. The same block works for any stdio MCP client.

{
  "mcpServers": {
    "sai": {
      "command": "npx",
      "args": [
        "-y",
        "@simular-ai/sai-mcp"
      ],
      "env": {
        "SAI_API_KEY": "sapi_YOUR_KEY"
      }
    }
  }
}

Notes for coding agents

Debug with curl

The raw request behind every task. It streams events until finish. If Sai asks before a step, the stream sends data-approval-request and waits: when isLinkOnly is false, answer it from another terminal with POST /v1/agents/approve ({ "approvalId": "…", "response": "yes" }, or "task" to allow the rest of the task). Only link-only approvals are completed at approvalUrl.

curl -N https://api.simular.ai/v1/agents/message \
  -H "Authorization: Bearer $SAI_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"message": "Open Notepad, type Hello from the Sai API, and tell me the window title"}'

FAQ

What is the Sai API?

The Sai API lets a program or a coding agent hand a task to Sai, Simular's computer-use agent, in plain English. Sai does the task on a real computer by seeing the screen, clicking and typing, and returns the result.

How is Sai different from a browser automation API?

A browser automation API drives a web browser. Sai operates the whole computer, so one task can move between websites, desktop apps and file dialogs, on Windows, Linux or macOS.

Which computers does Sai run on?

A Windows or Linux cloud computer that Simular hosts, or your own Mac or Windows PC. On Pay as you go, up to 5 cloud computers can run at the same time.

How does Sai cut the cost of repeated tasks?

Run a workflow once, then ask Sai to save it as a replayable skill. Later runs execute the saved code and ask the model only where the screen matters, which cuts tokens by up to 90% on repetitive tasks.

How does Sai handle sign-ins and other sensitive steps?

Sai pauses for approval before sensitive steps. Sign-ins, credentials and phone checks are link-only approvals: Sai sends the person an approval link, and they complete the step themselves.

How does Sai score on OSWorld?

On the official OSWorld 2.1 leaderboard, Sai has the highest partial score, 79.38%, at $14.34 per task, the only published cost on the leaderboard. On binary accuracy it is second, at 41.67%. Details: Sai on OSWorld 2.1.

How much does the Sai API cost?

Explore is free, with daily credits and limited access to a Windows cloud computer. Pay as you go is $50 a month, Sai Unlimited $500 a month, and Enterprise is custom. See pricing.

Does Sai work with Claude Code, Codex and Cursor?

Yes, through the @simular-ai/sai-mcp MCP server. One command adds it; see Getting started above.

Docs

Research

Optional