diff --git a/runtime/syntax/hare.vim b/runtime/syntax/hare.vim
index 07cf33f..4c7ae92 100644
--- a/runtime/syntax/hare.vim
+++ b/runtime/syntax/hare.vim
@@ -1,119 +1,142 @@
-" PRELUDE {{{1
-" Vim syntax file
-" Language: Hare
-" Maintainer: Amelia Clarke <me@rsaihe.dev>
-" Last Change: 2022-09-21
+" Vim syntax file.
+" Language:    Hare
+" Maintainer:  Amelia Clarke <selene@perilune.dev>
+" Last Change: 2024-05-10
+" Upstream:    https://git.sr.ht/~sircmpwn/hare.vim
 
-if exists("b:current_syntax")
+if exists('b:current_syntax')
   finish
 endif
-let b:current_syntax = "hare"
+syn include @haredoc syntax/haredoc.vim
+let b:current_syntax = 'hare'
 
-" SYNTAX {{{1
+" Syntax {{{1
 syn case match
+syn iskeyword @,48-57,@-@,_
 
-" KEYWORDS {{{2
-syn keyword hareConditional if else match switch
+" Keywords {{{2
+syn keyword hareConditional else if match switch
+syn keyword hareDefine def
+syn keyword hareInclude use
 syn keyword hareKeyword break continue return yield
+syn keyword hareKeyword case
+syn keyword hareKeyword const let
 syn keyword hareKeyword defer
+syn keyword hareKeyword export static
 syn keyword hareKeyword fn
-syn keyword hareKeyword let
-syn keyword hareLabel case
 syn keyword hareOperator as is
 syn keyword hareRepeat for
-syn keyword hareStorageClass const def export nullable static
-syn keyword hareStructure enum struct union
 syn keyword hareTypedef type
 
-" C ABI.
-syn keyword hareKeyword vastart vaarg vaend
+" Attributes.
+syn keyword hareAttribute @fini @init @test
+syn keyword hareAttribute @offset @packed
+syn keyword hareAttribute @symbol
+syn keyword hareAttribute @threadlocal
 
-" BUILTINS {{{2
-syn keyword hareBuiltin abort
+" Builtins.
+syn keyword hareBuiltin abort assert
+syn keyword hareBuiltin align len offset
 syn keyword hareBuiltin alloc free
 syn keyword hareBuiltin append delete insert
-syn keyword hareBuiltin assert
-syn keyword hareBuiltin len offset
+syn keyword hareBuiltin vaarg vaend vastart
 
-" TYPES {{{2
+" Types {{{2
 syn keyword hareType bool
-syn keyword hareType char str
+syn keyword hareType done
 syn keyword hareType f32 f64
-syn keyword hareType u8 u16 u32 u64 i8 i16 i32 i64
-syn keyword hareType uint int
-syn keyword hareType rune
+syn keyword hareType i8 i16 i32 i64 int
+syn keyword hareType never
+syn keyword hareType opaque
+syn keyword hareType rune str
+syn keyword hareType u8 u16 u32 u64 uint
 syn keyword hareType uintptr
+syn keyword hareType valist
 syn keyword hareType void
 
-" C ABI.
-syn keyword hareType valist
+" Other types.
+syn keyword hareStorageClass nullable
+syn keyword hareStructure enum struct union
 
-" LITERALS {{{2
-syn keyword hareBoolean true false
-syn keyword hareNull null
+" Literals {{{2
+syn keyword hareBoolean false true
+syn keyword hareConstant null
 
-" Number literals.
-syn match hareNumber "\v(\.@1<!|\.\.)\zs<\d+([Ee][+-]?\d+)?(z|[iu](8|16|32|64)?)?>" display
-syn match hareNumber "\v(\.@1<!|\.\.)\zs<0b[01]+(z|[iu](8|16|32|64)?)?>" display
-syn match hareNumber "\v(\.@1<!|\.\.)\zs<0o\o+(z|[iu](8|16|32|64)?)?>" display
-syn match hareNumber "\v(\.@1<!|\.\.)\zs<0x\x+(z|[iu](8|16|32|64)?)?>" display
+" Integer literals.
+syn match hareNumber '\v<%(0|[1-9]%(_?\d)*)%([Ee]\+?\d+)?%([iu]%(8|16|32|64)?|z)?>' display
+syn match hareNumber '\v<0b[01]%(_?[01])*%([iu]%(8|16|32|64)?|z)?>' display
+syn match hareNumber '\v<0o\o%(_?\o)*%([iu]%(8|16|32|64)?|z)?>' display
+syn match hareNumber '\v<0x\x%(_?\x)*%([iu]%(8|16|32|64)?|z)?>' display
 
-" Floating-point number literals.
-syn match hareFloat "\v<\d+\.\d+([Ee][+-]?\d+)?(f32|f64)?>" display
-syn match hareFloat "\v<\d+([Ee][+-]?\d+)?(f32|f64)>" display
+" Floating-point literals.
+syn match hareFloat '\v<%(0|[1-9]%(_?\d)*)\.\d%(_?\d)*%([Ee][+-]?\d+)?%(f32|f64)?>' display
+syn match hareFloat '\v<%(0|[1-9]%(_?\d)*)%([Ee][+-]?\d+)?%(f32|f64)>' display
+syn match hareFloat '\v<0x\x%(_?\x)*%(\.\x%(_?\x)*)?[Pp][+-]?\d+%(f32|f64)?>' display
 
-" String and rune literals.
-syn match hareEscape "\\[\\'"0abfnrtv]" contained display
-syn match hareEscape "\v\\(x\x{2}|u\x{4}|U\x{8})" contained display
-syn match hareFormat "\v\{\d*(\%\d*|(:[ 0+-]?\d*(\.\d+)?[Xbox]?))?}" contained display
-syn match hareFormat "\({{\|}}\)" contained display
-syn region hareRune start="'" end="'\|$" skip="\\'" contains=hareEscape display extend
-syn region hareString start=+"+ end=+"\|$+ skip=+\\"+ contains=hareEscape,hareFormat display extend
-syn region hareString start="`" end="`\|$" contains=hareFormat display
+" Rune and string literals.
+syn region hareRune start="'" skip="\\'" end="'" contains=hareEscape
+syn region hareString start='"' skip='\\"' end='"' contains=hareEscape,hareFormat
+syn region hareString start='`' end='`' contains=hareFormat
 
-" MISCELLANEOUS {{{2
-syn keyword hareTodo FIXME TODO XXX contained
+" Escape sequences.
+syn match hareEscape '\\[0abfnrtv\\'"]' contained
+syn match hareEscape '\v\\%(x\x{2}|u\x{4}|U\x{8})' contained display
 
-" Attributes.
-syn match hareAttribute "@[a-z]*"
+" Format sequences.
+syn match hareFormat '\v\{\d*%(:%(\.?\d+|[ +\-=Xbefgox]|F[.2ESUs]|_%(.|\\%([0abfnrtv\\'"]|x\x{2}|u\x{4}|U\x{8})))*)?}' contained contains=hareEscape display
+syn match hareFormat '{\d*%\d*}' contained display
+syn match hareFormat '{{\|}}' contained display
 
-" Blocks.
-syn region hareBlock start="{" end="}" fold transparent
+" Miscellaneous {{{2
 
 " Comments.
-syn region hareComment start="//" end="$" contains=hareCommentDoc,hareTodo,@Spell display keepend
-syn region hareCommentDoc start="\[\[" end="]]\|\ze\_s" contained display
+syn region hareComment start='//' end='$' contains=hareTodo,@haredoc,@Spell display
+syn keyword hareTodo FIXME TODO XXX contained
 
-" The size keyword can be either a builtin or a type.
-syn match hareBuiltin "\v<size>\ze(\_s*//.*\_$)*\_s*\(" contains=hareComment
-syn match hareType "\v<size>((\_s*//.*\_$)*\_s*\()@!" contains=hareComment
+" Identifiers.
+syn match hareDelimiter '::' display
+syn match hareName '\<\h\w*\>' nextgroup=@harePostfix skipempty skipwhite transparent
 
-" Trailing whitespace.
-syn match hareSpaceError "\v\s+$" display excludenl
-syn match hareSpaceError "\v\zs +\ze\t" display
+" Labels.
+syn match hareLabel ':\h\w*\>' display
 
-" Use statement.
-syn region hareUse start="\v^\s*\zsuse>" end=";" contains=hareComment display
+" Match `size` as a type unless it is followed by an open paren.
+syn match hareType '\<size\>' display
+syn match hareBuiltin '\<size\ze(' display
 
-syn match hareErrorAssertion "\v(^([^/]|//@!)*\)\_s*)@<=!\=@!"
-syn match hareQuestionMark "?"
+" Postfix expressions.
+syn cluster harePostfix contains=hareErrorTest,hareField,hareIndex,hareParens
+syn match hareErrorTest '!=\@!' contained nextgroup=@harePostfix skipempty skipwhite
+syn match hareErrorTest '?' nextgroup=@harePostfix skipempty skipwhite
+syn match hareField '\.\w*\>'hs=s+1 contained contains=hareNumber nextgroup=@harePostfix skipempty skipwhite
+syn region hareIndex start='\[' end=']' contained nextgroup=@harePostfix skipempty skipwhite transparent
+syn region hareParens start='(' end=')' nextgroup=@harePostfix skipempty skipwhite transparent
 
-" DEFAULT HIGHLIGHTING {{{1
-hi def link hareAttribute Keyword
+" Whitespace errors.
+syn match hareSpaceError '^ \+\ze\t' display
+syn match hareSpaceError excludenl '\s\+$' containedin=ALL display
+
+" Folding {{{3
+syn region hareBlock start='{' end='}' fold transparent
+
+" Default highlighting {{{1
+hi def link hareAttribute PreProc
 hi def link hareBoolean Boolean
-hi def link hareBuiltin Function
+hi def link hareBuiltin Operator
 hi def link hareComment Comment
-hi def link hareCommentDoc SpecialComment
 hi def link hareConditional Conditional
+hi def link hareConstant Constant
+hi def link hareDefine Define
+hi def link hareDelimiter Delimiter
+hi def link hareErrorTest Special
 hi def link hareEscape SpecialChar
 hi def link hareFloat Float
 hi def link hareFormat SpecialChar
+hi def link hareInclude Include
 hi def link hareKeyword Keyword
-hi def link hareLabel Label
-hi def link hareNull Constant
+hi def link hareLabel Special
 hi def link hareNumber Number
 hi def link hareOperator Operator
-hi def link hareQuestionMark Special
 hi def link hareRepeat Repeat
 hi def link hareRune Character
 hi def link hareStorageClass StorageClass
@@ -122,12 +145,13 @@
 hi def link hareTodo Todo
 hi def link hareType Type
 hi def link hareTypedef Typedef
-hi def link hareUse PreProc
 
-hi def link hareSpaceError Error
-autocmd InsertEnter * hi link hareSpaceError NONE
-autocmd InsertLeave * hi link hareSpaceError Error
+" Highlight embedded haredoc references.
+hi! def link haredocRefValid SpecialComment
 
-hi def hareErrorAssertion ctermfg=red cterm=bold guifg=red gui=bold
+" Highlight whitespace errors by default.
+if get(g:, 'hare_space_error', 1)
+  hi def link hareSpaceError Error
+endif
 
-" vim: tabstop=8 shiftwidth=2 expandtab
+" vim: et sts=2 sw=2 ts=8