[BUG] Claude for Excel (Office add-in) OTLP telemetry fails with CORS error

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?

Description :
I need observability for Claude Office agents (eg. Claude in Excel, Claude in Powerpoint, etc...). I configured it correctly in the admin console : https://claude.ai/admin-settings/office-agents

The Excel add-in sends OTLP telemetry directly from the WebView (https://pivot.claude.ai) to the configured OTLP endpoint, and it fails with:

Failed to load resource: Request header field dd-api-key is not allowed by Access-Control-Allow-Headers

The add-in should either route telemetry through the pivot.claude.ai backend, or the OTLP endpoint needs CORS headers that allow dd-api-key.

What Should Happen?

• No network errors, traces collected successfully
• Traces or logs of Claude in Excel user interaction should be visible in Datadog with a query such as @otel.service.name:office-agent or @service.name:office-agent

Error Messages/Logs

Failed to load resource: Request header field dd-api-key is not allowed by Access-Control-Allow-Headers https://otlp.datadoghq.eu/v1/traces

Failed to load resource: Request header field dd-api-key is not allowed by Access-Control-Allow-Headers https://otlp.datadoghq.eu/v1/logs

Steps to Reproduce

1. Configure OTLP endpoint in admin console : https://claude.ai/admin-settings/office-agents

• OTLP endpoint: https://otlp.datadoghq.eu
• OTLP protocol: http/protobuf
• OLTP headers: dd-api-key=******...**

(I'm sure the config is ok as I used the button "copy settings from Cowork", and Cowork telemetry does appear in my Datadog tenant)

1. Use the add-in in Excel on macOS, in Safari
2. Open Safari DevTools/inspector
3. Prompt anything to Claude in Excel
4. Observe CORS error on POST /v1/logs in Network tab and console

<img width="1491" height="860" alt="Image" src="https://github.com/user-attachments/assets/de08d120-a4b0-4784-879e-0989acca89fe" />

Claude Model

Sonnet (default)

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

Claude by Anthropic for Excel Version 1.0.0.8

Platform

Other

Operating System

macOS

Terminal/Shell

Other

Additional Information

<img width="474" height="301" alt="Image" src="https://github.com/user-attachments/assets/c95d001b-4bd8-4939-9587-a31bad6b0a6c" />
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<img width="1491" height="860" alt="Image" src="https://github.com/user-attachments/assets/de08d120-a4b0-4784-879e-0989acca89fe" />