OpenAI Codex 0.151.0 Stops `/cd` From Weakening the Sandbox

OpenAI released Codex CLI 0.151.0 on August 29, 2026. It preserves restored permission profiles across TUI turns, prevents /cd from weakening sandbox restrictions, and adds a configurable grace period for optional MCP servers.

OpenAI Codex AI-coding-tools MCP sandbox

OpenAI released 0.151.0 of the Codex CLI on August 29, 2026¹.

Preserved restored permission profiles across TUI turns and prevented /cd from weakening sandbox restrictions¹
Prevented stale Guardian classifications from authorizing actions after permission state changes¹
Improved remote sandbox enforcement using the executor’s actual home directory, operating system, and path conventions¹
On the feature side, made the startup grace period for discovering tools from optional MCP servers configurable, and let extensions inspect or replace MCP tool results before they reach the model¹

Most of the fixes cluster around how the boundary of what an agent may do is decided. The release also counts nested subagent token usage toward root goal budgets¹, which changes how usage appears if you lean on subagents. Keeping tool availability and reasoning effort correct when switching models or falling back to another one¹ matters too if you run more than one model in the same workflow.

Sources

Codex 0.151.0 release notes - OpenAI official repository (released August 29, 2026)