OpenAI cut Codex CLI’s context window by 27% without warning
OpenAI trimmed the default input context window for GPT-5.6 inside the Codex CLI from 372,000 tokens down to 272,000 tokens. That is a 27% reduction, and it was not announced with any fanfare. Developers caught it through a GitHub pull request to the Codex CLI repo.
Why This Matters for Coding Workflows
The cut surfaced quickly on Reddit and X, where developers started asking why the window shrank. The practical concern: a smaller context forces Codex into compaction mode earlier during long coding sessions. That means the agent starts summarizing or dropping earlier conversation history to make room for new work, before you would want it to.
For shorter scripts or isolated tasks, 272,000 tokens is still substantial. For enterprise workflows that pass in large codebases, long conversation threads, or multi-file context, hitting that ceiling sooner is a real tradeoff.
What to Watch
OpenAI has not publicly explained the reason for the change. If you rely on Codex CLI for extended agentic coding sessions, it is worth testing whether your typical session lengths now trigger compaction at an earlier point than before.
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