[Bug]: 400 Bad Request on Codex API call with gpt-5.3-codex in Headless Device Auth mode

[nhh0718]

Quick Summary

PicoClaw fails to execute LLM calls with gpt-5.3-codex using Device Code authentication (Headless mode). The backend returns a 400 Bad Request error specifically targeting model compatibility or missing/mismatched account-id headers.

Environment & Tools

• PicoClaw Version: v0.1.2 (or current main branch)
• Go Version: go 1.25
• AI Model & Provider: gpt-5.3-codex via OpenAI Codex (Headless Device Auth)
• Operating System: Ubuntu 24.04
• Channels: CLI

📸 Steps to Reproduce

1. Authenticate using the headless device flow: picoclaw auth login --provider openai --device-code
2. Complete the verification process via the provided URL and code.
3. Configure the agent to use gpt-5.3-codex as the primary model.
4. Trigger an agent task (e.g., via cli:cron or a simple prompt like "hello").
5. Observe the logs during the LLM provider call.

❌ Actual Behavior

The agent initializes correctly, but the LLM call fails immediately with the following error:

[ERROR] provider.codex: Codex API call failed {
  resolved_model=gpt-5.3-codex, 
  account_id_present=true, 
  error=POST "https://chatgpt.com/backend-api/codex/responses": 400 Bad Request, 
  status_code=400, 
  hint=verify account id header and model compatibility for codex backend
}

✅ Expected Behavior

The request should be successfully authorized and processed by the OpenAI Codex backend, returning the generated code or response to the PicoClaw agent.

💬 Additional Context

• The authentication itself reports as successful, and account_id_present is flagged as true in the logs.
• The error "400 Bad Request" with the hint about "model compatibility" suggests that the gpt-5.3-codex model might require specific headers or a slightly different endpoint structure in the 2026 API update compared to previous GPT-4 based Codex models.
• This might be related to the recent ChatGPT Plus session token management changes for high-tier models.

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[gitprivclaude]

Same problem here!

[brunorassat]

+1 for reach

2026/02/27 12:22:17 [2026-02-27T05:22:17Z] [INFO] agent: Processing message from cli:cron: hello {channel=cli, chat_id=direct, sender_id=cron, session_key=cli:default}
2026/02/27 12:22:23 [2026-02-27T05:22:23Z] [ERROR] provider.codex: Codex API call failed {requested_model=gpt-5.2-codex, api_code=, api_param=, hint=verify account id header and model compatibility for codex backend, request_id=, resolved_model=gpt-5.2-codex, messages_count=2, tools_count=13, account_id_present=true, error=POST "https://chatgpt.com/backend-api/codex/responses": 400 Bad Request , status_code=400, api_type=, api_message=}
2026/02/27 12:22:23 [2026-02-27T05:22:23Z] [ERROR] agent: LLM call failed {error=codex API call: POST "https://chatgpt.com/backend-api/codex/responses": 400 Bad Request , iteration=1}