When the onprogress option is passed, the _meta object in the request params was being overwritten, causing any existing _meta content to be lost.

Motivation and Context

this is right，the _meta could be passed to the svr

client?.callTool({
        name: toolName,
        arguments: input as Record<string, unknown>,
        _meta: {
          __test: 'test',
        },
      }, CallToolResultSchema, {}})

however:

client?.callTool({
        name: toolName,
        arguments: input as Record<string, unknown>,
        _meta: {
          __test: 'test',
        },
      }, CallToolResultSchema, {

onprogress: (progress: any) => {
}
}})

_meta disappeared...

How Has This Been Tested?

yes

Breaking Changes

no

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation update

Checklist

• I have read the MCP Documentation
• My code follows the repository's style guidelines
• New and existing tests pass locally
• I have added appropriate error handling
• I have added or updated documentation as needed

Additional context