Addendum to GPT-5 system card: GPT-5-Codex
What changed
This addendum to the GPT-5 system card shares a new model: GPT-5-Codex, a version of GPT-5 further optimized for agentic coding in Codex. GPT-5-Codex adjusts its thinking effort more dynamically based on task complexity, responding quickly to simple conversational queries or small tasks, while independently working for longer on more complex tasks.
Why it matters
A concrete addition to Practical AI: Tools, Models & Frameworks: it changes what's available to builders today rather than being general commentary.
How it compares
Related prior coverage to compare against:
- Introducing Codex
- Introducing GPT-5.3-Codex
- Building more with GPT-5.1-Codex-Max
Sources
- Addendum to GPT-5 system card: GPT-5-Codex (openai-blog)primary