Anthropic 400 on computer use after a model upgrade: the tool type is now computer_toolset_20260801

400 on computer use: migrate the tool type

Symptom

Computer use calls that worked before return 400 invalid_request_error on Opus 5.5. The message names the rejected tool type, then lists accepted types after "Did you mean one of".

Confirm the cause

Opus 5.5 supports computer use only as the computer_toolset_20260801 toolset on the Claude API and Google Cloud. The earlier computer_20251124 type (with its beta header) is rejected. The same 400 pattern applies to any Anthropic-defined tool type the requested model does not support.

Fix

1. Declare the tool as type computer_toolset_20260801 and drop the beta header.
2. Update the agent loop for the toolset as described in the migrate guide; it is not a drop-in rename.
3. Note the platform split: earlier models keep accepting computer_20251124, and Opus 5.5 on Bedrock does too.

Verify

The request succeeds on Opus 5.5 and the tool loop handles the toolset's action format. Keep the old type only for the models and platforms that still accept it.

The computer use tool version 400, the computertoolset20260801 requirement, and the platform exceptions are documented on the errors page. Verified live at https://docs.anthropic.com/en/api/errors.