Codex picks the skills that fit the request

Game engine maker Unity on Nov. 3 (Nov. 4 Japan time) posted a video on its official X account introducing its official plugin for OpenAI's AI coding tool "Codex." The plugin, released on Sept. 16 (Sept. 17 Japan time), gives Codex task procedures for each Unity feature as "skills" written by Unity engineers. Once installed, Codex chooses the skills that fit the request on its own and proceeds with the work. The video in the post showed four ways to use it.

ICYMI: We launched the official Unity plugin for @OpenAI's Codex, available directly in OpenAI's universal plugin directory.

@unitygames · November 4, 2026

There are 31 skills, covering user interface (UI) components, 2D, rendering, audio, physics, in-app purchases, ads, multiplayer and localization. They also include skills to install Unity Editor from the terminal, create and launch projects, and manage additional components (packages). The plugin supports Unity 6 and later and requires no per-project setup. Unity did not mention pricing, and the plugin is published on GitHub.

OpenAI's plugins bundle skills and mechanisms for connecting to external services. ChatGPT and Codex share the same public list (the universal plugin directory), from which Unity's plugin can be installed in a single step.

Making up for AI's reliance on outdated information

According to The Decoder, Unity explained that general-purpose AI agents tend to rely on forum posts and tutorials written for older versions, and the code they produce often compiles but does not work as intended. In its blog, Unity cited Stack Overflow's 2025 developer survey. 66% of respondents named AI solutions that are almost right, but not quite, as their biggest frustration, and 45% said fixing AI-written code takes time. 46% said they do not trust the accuracy of AI output, outnumbering the 33% who do.

The same skills for 5 AI tools

Unity has been extending the same plugin to various companies' AI agents in turn. The first was for Anthropic's "Claude Code" on Sept. 9, which at that point included 29 skills, and Unity said it would extend the plugin to other agents within the year. The Codex version came out a week later. On Oct. 1, it released a version for xAI's "Grok Build," saying the skills for Claude Code, Codex and Grok Build are "identical."

Unity's developer documentation, updated Oct. 30, lists four supported tools including Google's Antigravity. In October, installation instructions for Microsoft's GitHub Copilot CLI were added to the GitHub repository, and the change was merged on Nov. 3. The README lists five supported tools: Claude Code, Codex, Grok, Antigravity and GitHub Copilot CLI.

How Unity's official plugin spread (U.S. dates)
  1. Official plugin for Claude Code releasedOfficial
  2. Official plugin for Codex releasedOfficial
  3. Version for Grok Build released; version 0.1.8-betaOfficial
  4. Settings for Antigravity added on GitHubOfficial
  5. Video introducing the Codex version posted; Copilot CLI installation instructions addedOfficial

No direct connection to a running Editor

According to an announcement a Unity employee wrote on the forum, the Codex plugin is a bundle of skills and does not include a server for "MCP," a common standard for connecting AI to external tools. As a result, it does not connect to a running Unity Editor. According to the GitHub README, combining it with "Unity CLI," which runs Unity from the terminal, allows C# code to be executed in an open Editor. Because the skills directly rewrite script, scene and asset files, the README asks users to use version control and save before requesting large changes.

Unity's documentation cautions that agents with the plugin installed ask confirmation questions before making changes, so automated pipelines may stall. It also says that depending on the wording, skills may not be selected automatically and the skill name may need to be specified. The version updated on Oct. 1 is numbered "0.1.8-beta," a beta release. On the forum, a user pointed out outdated descriptions, saying the skill for UI Toolkit, used to build interface components, treats CSS gradients as unsupported even though they became available in Unity 6.7.

Epic supports editor control through MCP

Rival Epic Games has added an experimental MCP feature to its game engine "Unreal Engine 5.8" that lets external AI agents operate the editor. In July testing by Puget Systems, simple scenes and lighting setups could be built with Claude with few corrections, but complex mechanisms such as changes to the player character could not be fixed, and each run took 5 to 15 minutes.

Unity reports results on Nov. 5

Unity will report July-September results before the New York market opens on Nov. 5. Its shares closed at $40.48 on Nov. 3, up 4.1% from $38.87 the previous day.

Revenue for April-June was $546.47 million, up 24% from a year earlier. Growth was driven by "Vector," its AI-based advertising system, and the advertising and related business that includes Vector (Strategic Grow) rose 63% to $328.96 million. The development tools business, including the engine (Strategic Create), grew only 5% to $157.46 million. The outlook for July-September is $159 million to $163 million for Strategic Create (up 7% to 10% from a year earlier) and $380 million to $385 million for Strategic Grow (up 68% to 70%). The references to AI in the earnings materials mainly concern Vector, and no revenue from plugins for AI agents is shown.