Provider API: GPT-5.6 Luna returns 403 "Authentication failed" despite docs listing it as available on GOAT plan

Comece reproduzindo a requisição curl para /provider/v1/chat/completions e compare-a com um modelo funcional usando a mesma chave. Em seguida, leia os caminhos de listagem de modelos da Provider API, validação do plano e tratamento de erros referenciados pelo endpoint, juntamente com a documentação vinculada sobre preços e provedores. O trabalho estará concluído quando os modelos elegíveis retornarem a resposta documentada ou o erro de plano documentado correto, em vez de Authentication failed.

Summary

The Provider API rejects gpt-5.6-luna with 403 permission_error / "Authentication failed. Please check your credentials.", even though the docs state GPT-5.6 Luna is "Available on every plan, including Go" (https://commandcode.ai/docs/resources/pricing-limits). The same API key works fine with GPT-5.6 Sol, DeepSeek V4, Grok, Kimi, Qwen, GLM etc. google/gemini-3.7-flash exhibits the identical wrong error, while models that genuinely require a higher plan (Terra, Gemini 3.5/3.6, Claude family) correctly return MODEL_NOT_IN_PLAN.

Expected Behavior

gpt-5.6-luna works via Provider API on a GOAT plan (or any plan), as documented on https://commandcode.ai/docs/plans/goat (model table + usage estimates) and https://commandcode.ai/docs/resources/pricing-limits ("Available on every plan, including Go").

Actual Behavior

Every request to gpt-5.6-luna returns:

HTTP 403
{"error":{"message":"Authentication failed. Please check your credentials.","type":"permission_error"}}

Note: permission_error / "Authentication failed" is not listed among the documented Provider API error codes (https://commandcode.ai/docs/provider) — the table there only defines 403 upgrade_required. Reproducible over direct connection and via proxy, from multiple regions, repeatedly (also reproduced in earlier weeks, not just today).

Steps to reproduce the issue

curl https://api.commandcode.ai/provider/v1/chat/completions \
  -H "Authorization: Bearer ***" \
  -H "Content-Type: application/json" \
  -d '{"model":"gpt-5.6-luna","messages":[{"role":"user","content":"hi"}],"max_tokens":16}'

The key IS valid (authenticates fine for other models) and GET /provider/v1/models lists gpt-5.6-luna.

Command Code Version

use API KEY

Operating System

Linux

Terminal/IDE

No response

Shell

No response

Session file (optional)

No response

Fix prompt (optional)

No response

Additional context

Docs contradicting observed behavior:

• https://commandcode.ai/docs/plans/goat — Luna in the GOAT model table & usage estimates
• https://commandcode.ai/docs/resources/pricing-limits — "GPT-5.6 Luna … Available on every plan, including Go"; "Gemini 3.7 Flash … Available on GOAT and above"
• https://commandcode.ai/docs/provider — error-code table does not include permission_error