Variable Syntax

Variables are defined under vars (or palette) and referenced throughout vars and theme sections using one of three interchangeable reference forms. Palette values have a dedicated alias syntax using $$.

Reference Forms

Form	Syntax	Example
Parenthesised	$(path.to.var)	$(std.bg.panel)
Bare	$path.to.var	$std.bg.panel
Braced	${path.to.var}	${std.bg.panel}

All three resolve identically and can be mixed freely within the same file. The recommended form is $(...) because its explicit terminator makes it safe adjacent to punctuation and other text.

The bare form ($path.to.var) stops at the first character that is not a word character or a dot. This can cause ambiguity when a variable reference is immediately followed by text.

Palette Alias Syntax

The $$ prefix is shorthand for referencing palette.* values. It works with all three reference forms:

Written	Expands to
$$cyan	$palette.cyan
$($cyan)	$(palette.cyan)
${$cyan}	${palette.cyan}

This expansion happens before any variable resolution. After expansion, the reference resolves through the normal variable lookup. The $$ alias works anywhere — in palette, vars, theme.colors, tokenColors, semanticTokenColors, and inside colour function arguments.

yaml

palette:
  cyan: "#56b6c2"
  blue: "#2d5a87"

vars:
  accent: $$cyan                      # expands to $palette.cyan
  bg.accent: darken($$blue, 70)       # palette ref inside function

Dot-Path Hierarchies

Nested objects under vars (and palette) create dot-path variable names automatically:

yaml

vars:
  std:
    bg: "#1a1a2e"        # std.bg
    bg.panel: "#242424"  # std.bg.panel (not a nested object — literal key)

Variable-to-Variable References

Variables may reference other variables, including palette values:

yaml

palette:
  cyan: "#56b6c2"

vars:
  accent: $$cyan

Variables may also contain colour function calls:

yaml

vars:
  base: "#1a1a2e"
  lighter: lighten($(base), 20)

Resolution Order

Resolution happens in three distinct passes to ensure deterministic scoping:

1. Palette pass — every entry under palette is resolved using only the palette set itself. Palette entries cannot reference vars or theme values.
2. Variable pass — every entry under vars is resolved using the fully-resolved palette plus the variable set. Variables never see theme values during this pass.
3. Theme pass — entries under theme (colours, tokenColors, semanticTokenColors) are resolved against the union of the fully-resolved palette, variables, and the theme entries.

Variables never see partially-resolved theme state. This guarantees that a variable always evaluates to the same value regardless of where it is referenced in the theme.

Within each pass, resolution iterates until all tokens are fully resolved or a maximum iteration limit is reached. If circular references prevent resolution, the compiler raises an error listing the unresolved tokens.

Embedding in Strings

Variable references can appear anywhere a string value is expected:

yaml

theme:
  colors:
    editor.background: $(std.bg)
    panel.border: alpha($(std.fg), 0.15)

  semanticTokenColors:
    variable.declaration:
      foreground: $(std.fg)
      fontStyle: italic
    "string:escape": $$yellow

When using the parenthesised or braced forms, the reference is unambiguous even when embedded in a larger expression. The bare form works in most cases but may require switching to $(...) when adjacent to parentheses or other punctuation.

In semanticTokenColors, references work identically whether the value is a string (shorthand for foreground) or a property inside an object form.