[BUG] Claude for PowerPoint Add-in: "input_schema does not support oneOf, allOf, or anyOf at the top level" — completely unusable

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Claude for PowerPoint add-in throws a 400 error immediately on any request. Add-in is completely unusable.

What Should Happen?

Steps to Reproduce

Open PowerPoint (Microsoft 365, Windows)
Open Claude by Anthropic add-in from the side panel
Send any message
Error appears immediately — add-in is unusable

Error Messages/Logs

Claude for Office model error (oauth)
Build: 283afbad17a24ef2c82dff7b5f0df77cb6c44f0c

timestamp: 2026-06-06T17:28:15.222Z
provider: oauth
model: claude-opus-4-8
errorName: Error
status: 400
apiErrorType: invalid_request_error
requestId: req_011CbnQBEsJHogGioq7Hjx9H

Raw error:
tools.66.custom.input_schema: input_schema does not support oneOf, allOf, or anyOf at the top level

Steps to Reproduce

Steps to Reproduce

Open PowerPoint (Microsoft 365, Windows)
Open Claude by Anthropic add-in from the side panel
Send any message
Error appears immediately — add-in is unusable

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

latest

Platform

Other

Operating System

Windows

Terminal/Shell

Other

Additional Information

_No response_