@@ -0,0 +1,172 @@
+//nolint:wrapcheck
+package envvar
+
+import (
+	"bytes"
+
+	"github.com/yuin/goldmark"
+	"github.com/yuin/goldmark/ast"
+	"github.com/yuin/goldmark/parser"
+	"github.com/yuin/goldmark/renderer"
+	"github.com/yuin/goldmark/renderer/html"
+	"github.com/yuin/goldmark/text"
+	"github.com/yuin/goldmark/util"
+)
+
+// Node represents an environment variable reference node in markdown AST.
+type Node struct {
+	ast.BaseInline
+	EnvVar []byte
+}
+
+// Inline implements ast.Inline interface.
+func (n *Node) Inline() bool {
+	return true
+}
+
+// Kind implements ast.Node.Kind interface.
+func (n *Node) Kind() ast.NodeKind {
+	return KindEnv
+}
+
+// Dump implements ast.Node.Dump interface.
+func (n *Node) Dump(source []byte, level int) {
+	ast.DumpHelper(n, source, level, map[string]string{
+		"EnvVar": string(n.EnvVar),
+	}, nil)
+}
+
+// KindEnv is a NodeKind for environment variable nodes.
+var KindEnv = ast.NewNodeKind("Env")
+
+// Parser is a Goldmark inline parser for parsing environment variable nodes.
+//
+// Environment variable references have the format {env}`XDG_DATA_DIRS` which will be rendered as
+// a span with the environment variable name.
+type Parser struct{}
+
+var _ parser.InlineParser = (*Parser)(nil)
+
+// Trigger reports characters that trigger this parser.
+func (*Parser) Trigger() []byte {
+	return []byte{'{'}
+}
+
+// Parse parses an environment variable node.
+func (p *Parser) Parse(_ ast.Node, block text.Reader, _ parser.Context) ast.Node {
+	line, segment := block.PeekLine()
+
+	// Check if we have enough characters for {env}`
+	if len(line) < 6 || line[0] != '{' {
+		return nil
+	}
+
+	// Check for {env}` prefix
+	if !bytes.HasPrefix(line, []byte("{env}`")) {
+		return nil
+	}
+
+	// Skip the {env}` prefix
+	line = line[6:]
+	start := segment.Start + 6
+
+	// Find the closing backtick
+	endPos := bytes.IndexByte(line, '`')
+	if endPos < 0 {
+		return nil
+	}
+
+	// Extract the environment variable name
+	envVarName := line[:endPos]
+	if len(envVarName) == 0 {
+		return nil
+	}
+
+	// Create the node
+	n := &Node{
+		EnvVar: envVarName,
+	}
+
+	// Set the text segment to include the entire {env}`name` text
+	textSegment := text.NewSegment(segment.Start, start+endPos+1)
+	n.AppendChild(n, ast.NewTextSegment(textSegment))
+
+	// Advance the reader past this node
+	block.Advance(6 + endPos + 1) // {env}` + name + `
+
+	return n
+}
+
+// HTMLRenderer is a renderer for environment variable nodes.
+type HTMLRenderer struct {
+	html.Config
+}
+
+// NewHTMLRenderer returns a new HTMLRenderer.
+func NewHTMLRenderer(opts ...html.Option) renderer.NodeRenderer {
+	r := &HTMLRenderer{
+		Config: html.NewConfig(),
+	}
+	for _, opt := range opts {
+		opt.SetHTMLOption(&r.Config)
+	}
+
+	return r
+}
+
+// RegisterFuncs implements renderer.NodeRenderer.RegisterFuncs.
+func (r *HTMLRenderer) RegisterFuncs(reg renderer.NodeRendererFuncRegisterer) {
+	reg.Register(KindEnv, r.renderEnv)
+}
+
+func (r *HTMLRenderer) renderEnv(
+	w util.BufWriter,
+	source []byte, //nolint:revive
+	node ast.Node,
+	entering bool,
+) (ast.WalkStatus, error) {
+	if !entering {
+		return ast.WalkContinue, nil
+	}
+
+	n := node.(*Node)
+
+	if _, err := w.WriteString(`<span class="envvar">`); err != nil {
+		return ast.WalkStop, err
+	}
+
+	if _, err := w.Write(n.EnvVar); err != nil {
+		return ast.WalkStop, err
+	}
+
+	if _, err := w.WriteString("</span>"); err != nil {
+		return ast.WalkStop, err
+	}
+
+	return ast.WalkSkipChildren, nil
+}
+
+// Extension is a goldmark extension for environment variable references.
+type Extension struct{}
+
+// Extend implements goldmark.Extender.Extend.
+func (e *Extension) Extend(m goldmark.Markdown) {
+	// Register the parser
+	m.Parser().AddOptions(
+		parser.WithInlineParsers(
+			util.Prioritized(new(Parser), 100),
+		),
+	)
+
+	// Register the renderer
+	m.Renderer().AddOptions(
+		renderer.WithNodeRenderers(
+			util.Prioritized(NewHTMLRenderer(), 500),
+		),
+	)
+}
+
+// New returns a new environment variable extension.
+func New() goldmark.Extender {
+	return &Extension{}
+}

@@ -0,0 +1,78 @@
+package envvar
+
+import (
+	"bytes"
+	"testing"
+
+	"github.com/yuin/goldmark"
+)
+
+func TestEnvExtension(t *testing.T) {
+	markdown := goldmark.New(
+		goldmark.WithExtensions(
+			New(),
+		),
+	)
+
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "basic env variable reference",
+			input:    "{env}`XDG_DATA_DIRS`",
+			expected: "<p><span class=\"envvar\">XDG_DATA_DIRS</span></p>\n",
+		},
+		{
+			name:     "env variable reference in sentence",
+			input:    "The environment variable {env}`PATH` contains a list of directories.",
+			expected: "<p>The environment variable <span class=\"envvar\">PATH</span> contains a list of directories.</p>\n",
+		},
+		{
+			name:  "multiple env variable references",
+			input: "Both {env}`HOME` and {env}`XDG_CONFIG_HOME` define user directories.",
+			expected: "<p>Both <span class=\"envvar\">HOME</span> and <span class=\"envvar\">" +
+				"XDG_CONFIG_HOME</span> define user directories.</p>\n",
+		},
+		{
+			name:     "incomplete env variable reference - no closing backtick",
+			input:    "{env}`MISSING_BACKTICK",
+			expected: "<p>{env}`MISSING_BACKTICK</p>\n",
+		},
+		{
+			name:     "incomplete env variable reference - empty variable name",
+			input:    "{env}``",
+			expected: "<p>{env}``</p>\n",
+		},
+		{
+			name:  "env variable reference with code block",
+			input: "Set {env}`GOPATH` in your `~/.bashrc` file.",
+			expected: "<p>Set <span class=\"envvar\">GOPATH</span> " +
+				"in your <code>~/.bashrc</code> file.</p>\n",
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			var buf bytes.Buffer
+			if err := markdown.Convert([]byte(test.input), &buf); err != nil {
+				t.Fatalf("Failed to convert markdown: %v", err)
+			}
+
+			if got := buf.String(); got != test.expected {
+				t.Errorf("Expected:\n%q\nGot:\n%q", test.expected, got)
+			}
+		})
+	}
+}
+
+func TestEnvNodeKind(t *testing.T) {
+	n := &Node{}
+	if kind := n.Kind(); kind != KindEnv {
+		t.Errorf("Expected node kind %v, got %v", KindEnv, kind)
+	}
+	if !n.Inline() {
+		t.Error("Expected node to be inline")
+	}
+}

@@ -0,0 +1,36 @@
+package main
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+
+	"go.alanpearce.eu/searchix/internal/nixdocs/envvar"
+
+	"github.com/yuin/goldmark"
+)
+
+func main() {
+	// Create a new markdown parser with the environment variable extension
+	md := goldmark.New(
+		goldmark.WithExtensions(
+			envvar.New(),
+		),
+	)
+
+	// Example markdown text with environment variable references
+	markdown := "You need to set {env}`XDG_DATA_DIRS` to include your custom data directories.\n\n" +
+		"Other important environment variables are {env}`HOME` and {env}`PATH`."
+
+	// Convert markdown to HTML
+	var buf bytes.Buffer
+	if err := md.Convert([]byte(markdown), &buf); err != nil {
+		fmt.Fprintf(os.Stderr, "Error converting markdown: %v\n", err)
+		os.Exit(1)
+	}
+
+	// Print the resulting HTML
+	fmt.Println("HTML Output:")
+	fmt.Println("===========")
+	fmt.Println(buf.String())
+}

@@ -6,6 +6,7 @@ "github.com/yuin/goldmark"
 	"github.com/yuin/goldmark/extension"
 
 	"go.alanpearce.eu/searchix/internal/nixdocs/command"
+	"go.alanpearce.eu/searchix/internal/nixdocs/envvar"
 	"go.alanpearce.eu/searchix/internal/nixdocs/option"
 	"go.alanpearce.eu/searchix/internal/nixdocs/optlink"
 )
@@ -17,5 +18,6 @@ &fences.Extender{},
 		optlink.New(),
 		option.New(),
 		command.New(),
+		envvar.New(),
 	)
 }