[BUG] Claude code generate an incorrect "additionalProperties": {} field for ExitPlanMode tool

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?

as state in https://platform.claude.com/docs/en/build-with-claude/structured-outputs#json-schema-limitations

additionalProperties set to anything other than false is not supported

but new version of claude code generated a tool with. "additionalProperties": {}

{ "name": "ExitPlanMode", "description": "xxxxx", "input_schema": { "$schema": "https://json-schema.org/draft/2020-12/schema", "type": "object", "properties": {}, "additionalProperties": {} } },

What Should Happen?

additionalProperties can only be false or omitted

Error Messages/Logs

Steps to Reproduce

use claude code with a private anthropic api provider

Claude Model

None

Is this a regression?

Yes, this worked in a previous version

Last Working Version

_No response_

Claude Code Version

2.1.2

Platform

Other

Operating System

Windows

Terminal/Shell

Windows Terminal

Additional Information

_No response_