OpenAI AI Updates: April 16, 2026

1. Agents SDK Gets Sandboxed Execution and Model-Native Harness

OpenAI. OpenAI updated its Agents SDK with native sandbox execution and a model-native harness, enabling developers to build secure, long-running agents that work with files and tools within controlled environments. The new capabilities separate the harness from the compute layer, letting agents operate in siloed workspaces while protecting system integrity. Launching first in Python with TypeScript support planned. Source

2. Codex CLI v0.121.0 Ships Plugin Marketplace and Expanded MCP Support

OpenAI. Codex CLI v0.121.0 introduced a plugin marketplace (codex marketplace add) supporting installation from GitHub, git URLs, and local directories, along with namespaced MCP registration and parallel-call opt-in. The release also added TUI prompt history with Ctrl+R reverse search, memory mode controls, and a secure devcontainer profile with bubblewrap sandboxing. Source