[BUG] prompt.id unflattens into a nested prompt object and overwrites prompt attribute in telemetry

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?

This depends on the observability platform but I believe you should make the change instead to conform to HTML specs.

When prompt logging is enabled, the following fields are logged:

"prompt": "If you see this, you are awesome",
"prompt.id": "123456",
"prompt_length": "32",

Depending on the platform, this will break the prompt attribute since prompt.id unflattens into a nested prompt object with just an id - overwriting prompt in the process.

What Should Happen?

Every observability platform should behave the same and render all 3 fields per HTML specs. prompt.id should be renamed to prompt_id to remain consistent or a single prompt object with id, text and length should be included.

Error Messages/Logs

Steps to Reproduce

Enable logging with OTEL_LOG_USER_PROMPTS set to 1.

Log to observability platform of your choice, this was tested with CloudWatch and DataDog

Claude Model

Other

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.191

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

Terminal.app (macOS)

Additional Information

_No response_