GPT-5.1-Codex-Max Released: Faster, Smarter Coding

TL;DR

• GPT-5.1-Codex-Max is now the default model for CLI and IDE Extension users
• Faster, more intelligent, and more token-efficient than previous versions
• New "Extra High" reasoning effort for non-latency-sensitive tasks

New

• GPT-5.1-Codex-Max — New frontier agentic coding model trained on software engineering, math, and research tasks. Now default for signed-in ChatGPT users in CLI and IDE Extension.
• Extra High reasoning effort — New xhigh reasoning level lets the model think longer for better answers on non-time-critical tasks. Medium remains recommended for daily work.

How to Use

• CLI: Run codex --model gpt-5.1-codex-max or use the /model slash command
• IDE Extension: Select GPT-5.1-Codex-Max from the dropdown menu
• Persistent: Update your config.toml with model = "gpt-5.1-codex-max"

API access for GPT-5.1-Codex-Max coming soon. See GPT-5.1-Codex and GPT-5.1-Codex-Mini Now Available for context on the broader model lineup.

Source: Codex