[Bug] AutoClaw Windows: built-in Z.ai model requests return empty HTTP 406 #804

Pre-submission checklist

• I searched existing issues and found no report for AutoClaw model requests returning HTTP 406.
• I read CONTRIBUTING.md.

Category

Model config / model requests

Agent framework

Not framework-specific — AutoClaw Desktop

Severity

Blocking for the built-in model route

Reproducibility

Always in this installation; repeated on multiple attempts

Problem description

On Windows, AutoClaw's built-in Z.ai Auto Mode (zai_auto) fails on ordinary chat prompts. Signing out and signing back in did not resolve it.

The app log reports LLM request failed. rawError=406 status code (no body). The request reaches POST /autoclaw-proxy/proxy/autoclaw/chat/completions, which returns HTTP 406 with an empty response body. This was observed repeatedly on 2026-09-23 and 2026-09-24.

A separate minimal authenticated chat-completion probe also returned 406 with an empty body. Variations tested included streaming/non-streaming and model: auto/model: zai_auto. An unauthenticated control returned 401, not 406. No access token or account identifier is included here.

Steps to reproduce

1. Install/run AutoClaw Desktop 1.17.8.124 on Windows and sign in.
2. Select the built-in Z.ai Auto Mode (zai_auto).
3. Send a short prompt such as Reply with one word: OK.
4. Observe the request fail with HTTP 406 and no response body. Signing out and back in does not change the result.

Expected behavior

The built-in model returns a completion, or the app shows a useful error that identifies the actionable reason for rejection (for example, a model, account, or quota restriction).

Actual behavior

The backend returns HTTP 406 with zero response bytes, and the app surfaces only the generic 406 status code (no body) error. The exact server-side reason is unknown from the response.

Version and environment

• AutoClaw Desktop: 1.17.8.124
• OS: Windows
• Built-in model/provider: zai_auto / Z.ai Auto Mode
• First observed: 2026-09-23; reproduced 2026-09-24

Diagnostics

• AutoClaw request ID from the local trace: af7194d3-ee7b-4369-ba7b-0f5c5940db0c
• Startup auth/profile refresh logs also show getaddrinfo ENOTFOUND autoglm-api.autoglm.ai, followed by cached profile data and has_agent_code=false. This may be related, but is not confirmed as the cause.
• At a later check, DNS resolution and TCP 443 connectivity succeeded while the authenticated model request still returned 406.
• Earlier requests through a separately configured OpenRouter route returned HTTP 200 in the same runtime logs.

Please investigate why authenticated AutoClaw model requests receive an empty 406, and return an actionable diagnostic if the rejection is expected for this account/model/route.