GPT-5-Codex fails with 400 error when sending prompts in Zed's Copilot integration.

Description

The new GPT-5-Codex model errors out on message submission in the Agent panel, despite selection succeeding.

Steps to trigger the problem:

1. Sign in to GitHub Copilot in Zed settings.
2. Open Agent panel.
3. Select "GPT-5-Codex" from model dropdown.
4. Type and send a prompt.

Expected Behavior:
Model responds to the prompt.

Actual Behavior:
400 Bad Request: {"error":{"message":"model gpt-5-codex is not accessible via the /chat/completions endpoint","code":"unsupported_api_for_model"}}.

Model Provider Details

• Provider: Copilot Chat
• Model Name: gpt-5-codex
• Mode: Agent Panel
• Other Details (MCPs, other settings, etc): Copilot Pro+; model enabled in GitHub settings. Zed 0.205.4 on macOS 15.7.

Zed Version and System Specs

Zed 0.205.4
a588f85