agent-skills-vrc-udon

Name: agent-skills-vrc-udon
Author: niaka3dayo

Verified

Skills, rules, and validation hooks that teach AI coding agents to generate correct UdonSharp code

315stars

4forks

Shell

Installation

# Add to your Claude Code skills
git clone https://github.com/niaka3dayo/agent-skills-vrc-udon

Getting Started

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Security ReportVerified

Last scanned: 5/30/2026

{
  "issues": [],
  "status": "PASSED",
  "scannedAt": "2026-05-30T15:53:48.654Z",
  "npmAuditRan": true,
  "pipAuditRan": true
}

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README.md

Frequently Asked Questions

What is agent-skills-vrc-udon?

agent-skills-vrc-udon is an open-source ai agents skill for AI coding assistants such as Claude Code, Codex CLI, and ChatGPT, built by niaka3dayo. Skills, rules, and validation hooks that teach AI coding agents to generate correct UdonSharp code. It has 315 GitHub stars.

Is agent-skills-vrc-udon safe to use?

Yes. agent-skills-vrc-udon passed SkillsLLM's automated security scan — a dependency vulnerability audit plus prompt-injection heuristics — with no high-severity issues. You can read the full report in the Security Report section on this page.

How do I install agent-skills-vrc-udon?

Clone the repository with "git clone https://github.com/niaka3dayo/agent-skills-vrc-udon" and add it to your Claude Code skills directory (see the Installation section above).

What programming language is agent-skills-vrc-udon written in?

agent-skills-vrc-udon is primarily written in Shell. It is open-source under niaka3dayo on GitHub, so you can review or fork the full source.

Are there alternatives to agent-skills-vrc-udon?

Yes. SkillsLLM lists many other AI Agents skills you can browse and compare side by side. Open the AI Agents category from the badge at the top of this page, or use the Related Skills and comparison links further down to weigh agent-skills-vrc-udon against similar tools.

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⚠️ Third-Party Software Notice

This skill is third-party open-source software developed and hosted independently on GitHub. SkillsLLM is an informational directory and does not control or maintain the underlying repository.

Any security checks, ratings, or warnings displayed by SkillsLLM are automated and limited in scope. They do not constitute a security certification or guarantee that the software is safe, error-free, or free from malicious code, vulnerabilities, compromised dependencies, or prompt-injection risks.

Review the source code, permissions, dependencies, and configuration before installing or running any third-party skill. Use is at your own risk. To the maximum extent permitted by applicable law, SkillsLLM is not liable for losses arising from third-party software.

Read the Terms of Service

English | 日本語 | 简体中文 | 繁體中文 | 한국어

VRChat world development with UdonSharp (C# → Udon Assembly) has strict compile constraints that differ significantly from standard C#. In Udon runtime code, features like List<T>, async/await, try/catch, LINQ, and lambdas cause compile errors. Editor-evaluated field initializers are a separate C# context and may use some of these features to generate a final field value that Udon supports.

This repository provides AI coding agents with the knowledge to generate correct UdonSharp code from the start.

Problem	Solution
AI generates Udon-incompatible `List<T>`, `async/await`, etc. in runtime code	Rules + hooks auto-detect and warn
Sync variable bloat	Decision tree + data budget
Incorrect networking patterns	Pattern library + anti-patterns
SDK version feature differences	Version table with feature mapping
Late Joiner state inconsistency	Sync pattern selection framework

This is NOT:

A VRChat SDK or UdonSharp distribution
A Unity project (no executable code)
A replacement for official VRChat documentation
A guarantee of all AI behaviors

Issues: Bug reports and knowledge requests are welcome via GitHub Issues. PRs: Pull Requests are not accepted. See CONTRIBUTING.md for details.

Migrating from fork/clone? — Since v1.0.0, this project is distributed as an npm package. You no longer need to fork or clone the repository. Simply run one of the install commands below inside your VRChat Unity project. If you previously cloned this repo, you can safely delete the cloned directory and switch to the npm-based install.

Method 1: skills CLI (recommended)

npx skills add niaka3dayo/agent-skills-vrc-udon

This uses the skills.sh ecosystem to install skills into your project.

Method 2: Claude Code plugin

claude plugin add niaka3dayo/agent-skills-vrc-udon

Method 3: git clone

git clone https://github.com/niaka3dayo/agent-skills-vrc-udon.git

Installing a specific version

All published versions remain permanently available on npm and as git tags — nothing is ever removed.

# npm (any published version, v1.0.0 and later)
npm install agent-skills-vrc-udon@2.3.0

# git tag
git clone --branch v2.3.0 https://github.com/niaka3dayo/agent-skills-vrc-udon.git

skills/                                  # All skills
  unity-vrc-udon-sharp/                 # UdonSharp core skill
    SKILL.md                              # Skill definition + frontmatter
    LICENSE.txt                           # MIT License
    CHEATSHEET.md                         # Quick reference (1 page)
    rules/                               # Constraint rules
      udonsharp-constraints.md
      udonsharp-networking.md
      udonsharp-sync-selection.md
    hooks/                               # PostToolUse validation
      validate-udonsharp.sh
      validate-udonsharp.ps1
    assets/templates/                    # Code templates (17 files)
    references/                          # Detailed documentation (25 files)
  unity-vrc-world-sdk-3/                # VRC World SDK skill
    SKILL.md, LICENSE.txt, CHEATSHEET.md, references/ (8 files)
templates/                               # AI tool config templates
  CLAUDE.md  AGENTS.md  GEMINI.md        # Distributed to users via installer
.claude-plugin/marketplace.json         # Claude Code plugin registration
CLAUDE.md                               # Development guide (this repo only)

unity-vrc-udon-sharp

UdonSharp scripting core skill. Covers compile constraints, networking, events, and templates.

Area	Content
Constraints	C# features blocked in Udon runtime, their alternatives (`List<T>` → `DataList`, `async` → `SendCustomEventDelayedSeconds`), and the Editor-evaluated initializer boundary
Networking	Ownership model, Manual/Continuous sync, FieldChangeCallback, anti-patterns
NetworkCallable	Introduced in SDK 3.8.1: parameterized network events (up to 8 args)
Persistence	Introduced in SDK 3.7.4: PlayerData/PlayerObject API
Dynamics	Introduced in SDK 3.10.0: PhysBones, Contacts, VRC Constraints for Worlds
Web Loading	String/Image download, VRCJson, VRCUrl constraints
Templates	17 templates (interactions, sync patterns, persistence, editor utilities, and more)

unity-vrc-world-sdk-3

World-level scene setup, component placement, and optimization.

Area	Content
Scene Setup	VRC_SceneDescriptor, spawn points, Reference Camera
Components	VRC_Pickup, Station, ObjectSync, Mirror, Portal, CameraDolly
Layers	VRChat reserved layers and collision matrix
Performance	FPS targets, Quest/Android limits, optimization checklist
Lighting	Baked lighting best practices
Audio/Video	Spatial audio, video player selection (AVPro vs Unity)
Upload	Build and upload workflow, pre-upload checklist

Rules are constraint files that guide AI agents before code generation.

Rule File	Content
`udonsharp-constraints`	Blocked C# features, code generation rules, attributes, syncable types
`udonsharp-networking`	Ownership model, sync modes, anti-patterns, NetworkCallable constraints
`udonsharp-sync-selection`	Sync decision tree, data budget targets, 6 minimization principles

Networking rule: A parameterless public method without a leading _ is a legacy network entry. Prefix local-only/custom public methods with _, and use [NetworkCallable] to expose only intentional entries. Confirm NetworkCalling.InNetworkCall before reading NetworkCalling.CallingPlayer; authorize the caller separately from receiver ownership. Never use instance master as a security or access-control boundary.

Sync Decision Tree

Q1: Visible to other players?
    No  --> No sync (0 bytes)
    Yes --> Q2

Q2: Late Joiner needs current state?
    No  --> Events only (0 bytes)
    Yes --> Q3

Q3: Continuous change? (position/rotation)
    Yes --> Continuous sync
    No  --> Manual sync (minimal [UdonSynced])

Target: < 50 bytes per behaviour. Small-medium worlds: < 100 bytes total.

PostToolUse hooks that auto-run when .cs files are edited.

Category	Check	Severity
Context-sensitive Features	`List<T>`, LINQ, lambdas (blocked in Udon runtime; may be valid in Editor-evaluated field initializers)	WARNING
Blocked Runtime Features	`async/await`, `try/catch`, coroutines	ERROR
Blocked Patterns	`AddListener()`, `StartCoroutine()`	ERROR
Networking	`[UdonSynced]` without `RequestSerialization()`	WARNING
Networking	`[UdonSynced]` without `Networking.SetOwner()`	WARNING
Sync Bloat	6+ synced variables per behaviour	WARNING
Sync Bloat	`int[]`/`float[]` sync (recommend smaller types)	WARNING
Config Mismatch	`NoVariableSync` mode with `[UdonSynced]` fields	ERROR

Supports both Bash (validate-udonsharp.sh) and PowerShell (validate-udonsharp.ps1).

The Bash validator requires jq. If jq is unavailable, it passes the input through unchanged and emits VALIDATOR-WARNING: validation skipped (JQ_UNAVAILABLE); it does not silently claim that validation succeeded.

SDK Versions

Active support / last verified: VRChat SDK 3.10.5

From v4.0.0 onward, the support policy is latest stable SDK only; the support target moves to a new stable release only after this repository verifies it. A new stable release is not supported automatically. Current last verified target: 3.10.5.

The table below keeps historical feature-introduction notes for migration reference. SDK 3.7.1-3.10.4 entries are historical information only; they are not active support or validation targets for this Skill. This is the Skill's support boundary, not a statement about VRChat's own SDK policy.