[BUG] ElevenLabs connector (elevenlabs-player) fails with "fetch failed" despite valid API key and working network

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?

The elevenlabs-player MCP connector consistently fails with Failed to generate speech: fetch failed when using the generate_tts tool (and also generate_sound_effect).

I've ruled out the most common causes:

• The API key is valid and has text_to_speech permission (tested directly against https://api.elevenlabs.io/v1/text-to-speech/... from PowerShell and from native Node.js fetch on the same machine — both respond correctly with status 200).
• No proxy configured on Windows (ProxyEnable = 0).
• No firewall rules blocking outbound traffic for Claude or Node.
• ElevenLabs service is fully operational (status.elevenlabs.io = "fully operational").
• Fully reinstalled the connector (uninstall → reinstall → re-paste API key) and the error persists.

This suggests the connector process inside Claude Desktop is not resolving/connecting correctly to api.elevenlabs.io, even though the rest of the machine can.

Environment: Claude Desktop on Windows 11, running locally (not remote).

What Should Happen?

The generate_tts (and generate_sound_effect) tool should successfully connect to the ElevenLabs API and generate/play audio, the same way a direct request with the same API key succeeds from PowerShell or native Node.js fetch on the same machine.

Error Messages/Logs

Failed to generate speech: fetch failed
Failed to generate sound effect: fetch failed

Steps to Reproduce

1. Install and enable the elevenlabs-player MCP connector with a valid ElevenLabs API key (with text_to_speech permission).
2. Call the generate_tts tool with any text (or generate_sound_effect with any prompt).
3. Observe the error "Failed to generate speech: fetch failed" (or "fetch failed" for sound effects).
4. Confirm the same API key works fine when called directly via PowerShell Invoke-WebRequest or Node.js fetch from the same machine.
5. Uninstall and reinstall the connector, re-enter the API key — error persists.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

2.1.178 (Claude Code)

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

PowerShell

Additional Information

Additional diagnostics performed:

• Windows proxy settings: ProxyEnable = 0 (no system proxy configured)
• No outbound firewall rules blocking Claude or Node processes
• ElevenLabs status page (status.elevenlabs.io) shows "fully operational" — not a service outage
• Direct API call from PowerShell (Invoke-WebRequest) to https://api.elevenlabs.io/v1/text-to-speech/... with the same API key: succeeds (status 200)
• Direct API call using native Node.js fetch() with the same API key: succeeds (status 200/401 depending on endpoint tested)

This strongly suggests the issue is isolated to how the elevenlabs-player connector process makes its network request from within Claude Desktop, since the same machine, same network, and same API key work fine outside of it.