Diagnostics

Every message AUI can produce. Codes are stable: one is never renumbered or reused.

Messages look like this in the console, and are clickable:

[AUI] Assets/UI/Shop.aui:14:23 error AUI201: unknown style property 'colour'

Range	Area
0xx	markup syntax
1xx	markup semantics
2xx	stylesheet
3xx	languages
4xx	layout
5xx	build and codegen (editor only)
6xx	fonts (editor only)

AUI/Validate compiles every view and prints all of them, including warnings a successful build would not stop for.

0xx Markup syntax

Code	Meaning and fix
AUI001	Unexpected character. Usually a stray < or > in text; escape it as &lt; / &gt;
AUI002	A tag was never closed. Close it, or make it self-closing (<text ... />)
AUI003	Closing tag does not match the open one
AUI004	More than one root element. A .aui has exactly one <view>
AUI005	Attribute value is not quoted. Write max="8", not max=8
AUI006	The same attribute twice on one element
AUI007	The file has no content
AUI008	A bare & that is not an entity. Write &amp;
AUI009	Unknown entity. Supported: &lt; &gt; &amp; &quot; &apos; &nbsp; &#NN; &#xHH;
AUI010	Text outside the root element
AUI011	A <!-- with no -->
AUI012	An attribute quote was never closed

1xx Markup semantics

Code	Meaning and fix
AUI100	Unknown tag, and no .aui of that name exists. Check spelling; the message suggests a near match
AUI101	That attribute is not allowed on this element. See elements
AUI102	Two elements share an id, or two ids, bindings or nested views produce the same generated C# member (save-all and saveall both become E_SAVEALL; two <Card/> without ids both become childCard; {itemsCount} next to <repeat id="items">). Rename one
AUI103	name does not equal the file stem. Rename one of them
AUI104	The root element is not <view>
AUI105	A <repeat> must have exactly one template child, plus an optional <empty>
AUI106	A <tab>'s page names no page in the group
AUI107	A nested view was used but Name.aui does not exist
AUI108	One binding name used with two different types. Rename one
AUI109	A handler value is not a C# identifier
AUI110	A required attribute is missing (a <view> without name, for instance)
AUI111	An attribute value does not parse for that attribute (a literal passed to a typed nested-view prop included). As a warning: hidden on an element with icon= or key=, which bakes at the wrong size; use if="{flag}"
AUI112	The element is not allowed there. See where each element may go. Also select, pages and tabs inside a <repeat> or <template>: their runtime tables are per element, not per row
AUI113	Views nest each other in a cycle
AUI114	A <pages> group nothing drives. Add a <tabs>, or select pages from code
AUI115	A <text> has more than one of key, text and literal content. Pick one
AUI116	Malformed {binding}, or a binding whose name collides with an AuiView member
AUI117	Literal, untranslated text. Informational, so you can find every string that will stay English
AUI118	{item.x} used outside a <repeat> or <template>
AUI119	No such icon. See icons
AUI120	A repeat's max is outside 1 to 64
AUI121	An attribute that is not a declared <prop> on a child that declares props
AUI122	Malformed <prop> declaration

2xx Stylesheet

Code	Meaning and fix
AUI200	Stylesheet syntax error, including a --variable declared outside :root (variables are sheet-wide, so that is the only place they may be written)
AUI201	Unknown property. See style properties
AUI202	The value does not parse for that property's kind, an unterminated ( in a value, or a negative grow, opacity, scale or line-height
AUI203	var(--x) with no :root declaration. Define it, or use var(--x, fallback); the fallback may itself be a var()
AUI204	Unknown pseudo-state. Only hover, pressed, selected, disabled
AUI205	Unsupported selector, usually a descendant combinator (.card text). Give the child its own class
AUI206	A rule no element matches. Warning; often a typo or a leftover
AUI207	A class used in markup that no sheet defines
AUI208	<link href> points at a file that does not exist
AUI209	Malformed transition value
AUI210	A state rule sets a property that cannot be animated. Only color, background, border, icon-color, opacity, scale, offset are allowed
AUI211	More than 64 regular classes visible to one view. Move one-off looks into style="" or star classes
AUI212	A bake-only property on a class only reachable at runtime. radius, font-weight, page-transition and show cannot change in-world
AUI213	A bound style value mixing bindings with literal text (width: {n}mm), or an unbindable property
AUI214	More than 256 star classes

3xx Languages

Code	Meaning and fix
AUI300	Key missing in some languages. Warning, and it lists which
AUI301	Key missing in the default language. An error; the view will not build
AUI302	Language JSON syntax error. Arrays and nulls are not allowed
AUI303	key= names a key no language file defines
AUI304	A {placeholder} in the string with no matching args binding
AUI305	No language files found. Create at least the default one
AUI306	The same flattened key defined twice
AUI307	Placeholders differ between languages, or from what args supplies

See languages.

4xx Layout

Code	Meaning and fix
AUI400	Content overflows even after proportional shrinking. Enlarge the view, or give the text a max-width and wrap="true"
AUI401	A solved rectangle has negative size
AUI402	position: absolute with no edge set
AUI403	An explicit size and the opposite edge. The size wins
AUI404	An edge on a non-absolute element. Ignored
AUI405	display or position on the root view

5xx Build and codegen

These come from the build queue rather than a compile, so they carry no file position; the message names the view.

Code	Meaning and fix
AUI500	The class in Name.g.cs is not available yet. Normal once right after the source is written; otherwise a compile error elsewhere. Fix it and save again
AUI501	UdonSharp produced no program for the view. A handler named in markup with no method (or the wrong signature) is the usual cause; read the UdonSharp errors above it
AUI502	Reserved for a handler check at codegen time; today a missing handler surfaces as AUI501 plus the C# error
AUI503	The prefab builder failed, or a view was given up on after four attempts. The message says which step it was stuck on and, for a nested view, which child prefab it waited for
AUI504	A required table was not exported to the Udon heap. Rebuild; if it persists, the runtime package did not compile

6xx Fonts

Code	Meaning and fix
AUI600	The character set changed since the last bake (checked whenever the language table is rebaked). Run AUI/Bake Fonts
AUI601	A character has no glyph in any source font. This is what boxes in-world look like at build time
AUI602	A source font under Fonts/src is missing

Next

• Troubleshooting for symptoms rather than codes.
• The VS Code extension, which shows these as you type and offers quick fixes for many of them.