TsukimiSharp Reference

TsukimiSharp is a subset of C# that compiles to Udon, which runs inside VRChat worlds.

Getting started

Page	Contents
Quick start	From installing to your first Behaviour running

Lookup

Page	Contents
Finding it by what you want to do	From what you want to do, jump to the page that shows how
Features UdonSharp does not have	Ways of writing and tools this language has that UdonSharp does not

Runtime

Page	Contents
Udon’s execution model	How it runs on Udon, and the reasons behind the restrictions
File layout and namespaces	File layout, namespaces, visibility, name resolution
Events	List of events the runtime calls
Field initialization and defaults	Field initializers, and the value when you write none

Syntax

Page	Contents
Lexical elements and literals	All forms of numeric and string literals
List of types	Types you can use (section below)
Expressions and operators	Operators, strings, null handling, primary expressions
Type conversions	Which conversions are supported, type tests, and boxing
Numeric overflow and conversion	Values on overflow, and conversions that halt
Null and references	Sources of null and how to handle it safely
Statements and control flow	Branching, loops, statement structure
Pattern matching	All pattern forms and exhaustiveness
Member declarations	All forms of members you can declare
Variables and passing arguments	Kinds of variables, ref / out / in, definite assignment
Extension methods	How to write static helpers
Attributes	List of attributes that have meaning to the runtime
Reactive programming	Writing work that runs when a value changes, on the dependent side
Preprocessor	Directives you can use

Async

Page	Contents
async / await	Split work that does not fit in one frame and advance it piece by piece
Constructs allowed in an async method	Loops, branches and calls allowed in the body of an async method
GPU kernels and await	Bound GPU work by how many times it runs per frame

GPU

Page	Contents
GPU kernel	Making the GPU compute: the kernel’s shape, types, cells and coordinates
Kernel statements and expressions	Statements, operators, and per-type operations available inside a kernel
Functions callable from a kernel	Built-ins and helper functions callable from a kernel
Running a GPU kernel	Buffers, execution, retrieving results
Surface shaders (experimental)	Describe what a Renderer draws in C# (experimental)

Machine learning models

Page	Contents
ONNX models (experimental)	Bake a trained model in at compile time instead of loading it (experimental)
ONNX models on Udon (experimental)	Pass the input and output as arrays and read the result back as numbers (experimental)
ONNX models on the GPU (experimental)	Pass images in buffers; floating-point models; which models are accepted (experimental)
ONNX model operators (experimental)	The operators that are accepted, and their conditions (experimental)

Working with Unity and VRChat

Page	Contents
Getting and calling components	Getting, calling, referencing
Calling Unity and VRChat types	Common calls, and members you cannot call
Sync	Synced variables, ownership, events
Sync design	What is guaranteed, the failures, and patterns to write

MoCHI (experimental)

Page	Contents
MoCHI Reference (experimental)	Describe the objects placed in a world in .mochi.xml, and generate a prefab when you save in Unity (experimental)
Syntax overview	Categories of elements, how tags map to GameObjects, parts and props, values fixed at generation time and values that change at runtime, expansion order, name scope
Element reference	For each element: syntax, where it can be placed, allowed children, attributes, what it creates, the name when name is omitted, errors
Value grammar	EBNF and diagnostic numbers for numbers, Vector3, Color, bool, paths, bindings, data, static, and enumerations
Setup and generation	Files and parts, entry points, generation on save, handling of generated files, checks before Play and upload
Props and identity	How props are passed, identity and key
Components and prefabs	Components, material copies, changes inside a prefab, <Slot> content, mount points
Component list	Categories of components you can write, value types, asset references, and components you can’t write
Physics components	Attributes of Rigidbody, colliders, joints, and more
Rendering components	Attributes of renderers, Light, Camera, particles, and more
Audio components	Attributes of AudioSource, reverb, and Audio Filters
UI components	Attributes of Canvas, Image, Button, layout groups, and more
TextMeshPro components	Attributes of TextMeshPro, TextMeshProUGUI, and more
VRChat components	Attributes of VRCPickup, VRCObjectSync, VRCMirrorReflection, and more
Other components	Attributes of Animator, constraints, NavMesh, and more
Layout	size and pivot, how <Row> and <Grid> arrange children, part size
Part with a T# script	Generated <Name>.Mochi.cs, runtime props, two-stage generation
inspect	Arguments when passing mochi to the MCP inspect tool, and the JSON it returns
Errors	List of diagnostic codes, and examples that are errors

Tools

Page	Contents
Testing	Running a Behaviour and checking it without launching Unity
Profiler	See the weight of the programs placed in your scene, as static counts and measured counts, in your browser
Exporting to UdonSharp	Export a Behaviour written in T# as C# that UdonSharp reads
MCP server	A server for calling the compiler from outside, used from AI clients
Skills	The instructions an AI client reads, and how to write them out

Other lists

Page	Contents
Error	Looking things up by error number