GPT 5.1 Codex High

Codex High increases its internal deliberation for tricky work like framework upgrades, cross-service changes, and performance-sensitive fixes. It verifies intermediate steps, explains choices, and returns deterministic structured outputs that are easy to audit. The model still streams tokens for interactive editing, but prioritizes correctness over raw latency. Teams typically route routine edits to GPT 5.1 Codex for throughput, then reserve Codex High for high-stakes changes, large refactors, and compliance-bound code paths.