Run an Anthropic computer loop

Connect the Anthropic Messages API computer tool to a placed Modal desktop.

Your application owns the Anthropic client, message history, limits, and approval policy. AnthropicAdapter only converts provider actions to SDK actions.

Install the provider extra

uv add "modal-computer-use[modal,anthropic]==2.0.2"

Store ANTHROPIC_API_KEY in the placed Function. Keep it out of the desktop Sandbox.

Select matching tool versions

Tool	Beta header	Use
computer_20251124	computer-use-2025-11-24	Current integration with optional zoom
computer_20250124	computer-use-2025-01-24	Compatible older integration
computer_20241022	computer-use-2024-10-22	Adapter compatibility

The adapter defaults to computer_20251124. Set enable_zoom=True when you want zoom with that version.

Keep the loop inside the placed Function

Follow the session handoff guide. Borrow once around the complete Messages API loop.

async with handle.borrow_async(
    run_id=run_id,
    function_region=REGION,
) as computer:
    response = await run_anthropic_computer_loop(
        client=anthropic_client,
        computer=computer,
        task=task,
        display_width_px=1280,
        display_height_px=800,
    )

Keep the complete assistant content in message history. Continue only when stop_reason is tool_use. Return all matching tool results in the next user message.

Preserve hosted-tool order

Execute hosted computer calls in response order. Use computer.step() for actions that need an immediate screenshot.

step = await computer.step(
    [normalized_action],
    continue_on_error=False,
    call_id=tool_use.id,
)

Keep these provider semantics:

• Return cursor coordinates as text for cursor_position.
• Reuse the native image from screenshot or zoom when present.
• Avoid a duplicate trailing image after a native image action.
• Keep separate hosted calls separate.

Use a custom batch tool only for a fixed sequence that needs no intermediate model decision. Send its ordered actions in one computer.step() call.

Use the maintained example

The Anthropic loop example contains reviewed schemas, the placed Function, provider ordering, batch handling, limits, result conversion, cancellation, and cleanup.

Treat tasks, page content, screenshots, provider output, typed text, and clipboard text as untrusted. Ask for approval before an action creates an external effect. Anthropic safety checks do not cover an application-owned batch tool.