[Bug]: Azure Foundry + Codex gpt-5.6-luna fails in T3 Code with X-OpenAI-Internal-Codex-Responses-Lite unsupported_value

[devjoca]

Before submitting

• I searched existing issues and did not find a duplicate.
• I included enough detail to reproduce or investigate the problem.

Area

apps/desktop

Steps to reproduce

1. Open the T3 Code desktop app.
2. Configure the Codex provider for Azure Foundry / Azure OpenAI.
3. Add AZURE_OPENAI_API_KEY in Settings -> Providers -> Codex -> Environment variables and save it as sensitive.
4. Select gpt-5.6-luna.
5. Start a new full-access thread.
6. Send a trivial prompt such as Hello, Luna.

Expected behavior

Once the provider env var is configured, the thread should run normally against Azure.
If the selected model or transport is unsupported, T3 Code should detect that before dispatch and show a clear actionable message.

Actual behavior

The earlier Missing environment variable: AZURE_OPENAI_API_KEY error goes away, which suggests the provider secret is being picked up.
The next failure is:

{
  "error": {
    "message": "X-OpenAI-Internal-Codex-Responses-Lite only supports function tools, custom tools, and client-executed tool search.",
    "type": "invalid_request_error",
    "param": "tools",
    "code": "unsupported_value"
  }
}

In the desktop UI this error may also render clipped / partially cut off, but that appears to be a separate issue.

Impact

Blocks work completely

Version or commit

No response

Environment

macOS desktop app, Azure OpenAI via Codex provider

Logs or stack traces

{
  "error": {
    "message": "X-OpenAI-Internal-Codex-Responses-Lite only supports function tools, custom tools, and client-executed tool search.",
    "type": "invalid_request_error",
    "param": "tools",
    "code": "unsupported_value"
  }
}

Related upstream reports
- openai/codex#31870
- openai/codex#31875
- openai/codex#31882

Screenshots, recordings, or supporting files

No response

Workaround

I have not found a reliable workaround in T3 Code yet.
Older non-5.6 Codex models may avoid this, but I have not confirmed that here.
5.4 is working good for me.