OpenAI Codex CLI

Codex CLI v0.80: Agentic Terminal Evolution

As of January 2026, the Codex CLI has completed its transition to a standalone Rust architecture, integrating the Model Context Protocol (MCP) for deep environment awareness. The system now utilizes GPT-5.2-Codex, featuring native context compaction for long-horizon engineering tasks 📑.

Orchestration & Sandbox Architecture

The CLI functions as a local coordinator, proposing multi-step execution plans in a sandboxed Terminal User Interface (TUI) before applying any changes to the disk 📑.

• Native Isolation: Secure execution is enforced via Landlock and seccomp on Linux, and sandbox-exec on macOS, providing a hardware-level barrier during automated tests and scripts 📑.
• Responses API Integration: Utilizes the 2026 'responses' endpoint, which supports server-side session persistence and semantic event streaming for real-time code diffs 📑.
• Agent Skills (agentskills.io): Implements the cross-platform skills standard, allowing developers to share modular automation scripts (e.g., CI/CD hardening, SQL migrations) across team environments 📑.

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Contextual Intelligence & Privacy

By leveraging MCP, Codex CLI pulls metadata from local documentation, Jira tickets, and database schemas to ground its reasoning without transmitting sensitive raw data to the cloud 🧠.

• Context Compaction: GPT-5.2-Codex uses recursive summarization of the KV-cache, maintaining reasoning logic for 400K+ context windows with 30% lower token overhead 📑.
• Local History Management: Encrypted session transcripts are stored in ~/.codex/sessions/, ensuring state recovery even after terminal crashes 📑.

Evaluation Guidance

Technical leads should enforce approval_mode = "manual" in config.toml for all production-adjacent repositories. Verify that custom Agent Skills are signed to prevent the execution of malicious automation logic. Organizations using local LLM gateways must ensure compatibility with the event-driven Responses API schema 📑.