diff --git a/internal/rosa/builtins.go b/internal/rosa/builtins.go
index 6d457dbd..dbafa397 100644
--- a/internal/rosa/builtins.go
+++ b/internal/rosa/builtins.go
@@ -1,10 +1,13 @@
 package rosa
 
 import (
+	"io/fs"
+	"os"
 	"path"
 	"slices"
 	"strconv"
 	"strings"
+	"time"
 
 	"hakurei.app/internal/pkg"
 )
@@ -115,8 +118,29 @@ func skipGNUTests(tests ...int64) string {
 	return buf.String()
 }
 
-// builtin contains native and embedded [Artifact] registrations.
-var builtin S
+var (
+	// builtin contains native and embedded [Artifact] registrations.
+	builtin S
+
+	// parseTime is the duration of early parsing of built-in azalea expressions.
+	parseTime time.Duration
+)
+
+// ParseTime returns the time taken by early parsing of built-in azalea expressions.
+func ParseTime() time.Duration { return parseTime }
+
+func init() {
+	sub, err := fs.Sub(builtinAzalea, "package")
+	if err != nil {
+		panic(err)
+	}
+	t := time.Now()
+	if err = builtin.RegisterFS(sub); err != nil {
+		println(err.Error())
+		os.Exit(1)
+	}
+	parseTime = time.Since(t)
+}
 
 // New returns the address of a newly populated [S] derived from built-ins.
 func New() *S { return builtin.Clone() }
diff --git a/internal/rosa/builtins_embed.go b/internal/rosa/builtins_embed.go
new file mode 100644
index 00000000..2ef42f00
--- /dev/null
+++ b/internal/rosa/builtins_embed.go
@@ -0,0 +1,11 @@
+//go:build !penv
+
+package rosa
+
+import "embed"
+
+// builtinAzalea is the backing directory of built-in azalea-based [Artifact]
+// implementations.
+//
+//go:embed package
+var builtinAzalea embed.FS
diff --git a/internal/rosa/builtins_env.go b/internal/rosa/builtins_env.go
new file mode 100644
index 00000000..a125e25f
--- /dev/null
+++ b/internal/rosa/builtins_env.go
@@ -0,0 +1,28 @@
+//go:build penv
+
+package rosa
+
+import (
+	"io/fs"
+	"os"
+)
+
+// builtinAzalea is the backing directory of built-in azalea-based [Artifact]
+// implementations.
+var builtinAzalea = func() fs.FS {
+	const name = "ROSA_SOURCE"
+
+	pathname, ok := os.LookupEnv(name)
+	if !ok {
+		println(name + " not set")
+		os.Exit(1)
+	}
+
+	root, err := os.OpenRoot(pathname)
+	if err != nil {
+		println(err.Error())
+		os.Exit(1)
+	}
+
+	return root.FS()
+}()
diff --git a/internal/rosa/rosa.go b/internal/rosa/rosa.go
index 1089ffa1..2a7cd777 100644
--- a/internal/rosa/rosa.go
+++ b/internal/rosa/rosa.go
@@ -2,14 +2,11 @@
 package rosa
 
 import (
-	"embed"
-	"io/fs"
 	"os"
 	"slices"
 	"strconv"
 	"strings"
 	"sync"
-	"time"
 	"unsafe"
 
 	"hakurei.app/fhs"
@@ -623,28 +620,3 @@ func (attr *GenericHelper) script(t Toolchain, _ string) string {
 	script += attr.Install
 	return script
 }
-
-// parseTime is the duration of early parsing of built-in azalea expressions.
-var parseTime time.Duration
-
-// ParseTime returns the time taken by early parsing of built-in azalea expressions.
-func ParseTime() time.Duration { return parseTime }
-
-// builtinAzalea is the backing directory of built-in azalea-based [Artifact]
-// implementations.
-//
-//go:embed package
-var builtinAzalea embed.FS
-
-func init() {
-	sub, err := fs.Sub(builtinAzalea, "package")
-	if err != nil {
-		panic(err)
-	}
-	t := time.Now()
-	if err = builtin.RegisterFS(sub); err != nil {
-		println(err.Error())
-		os.Exit(1)
-	}
-	parseTime = time.Since(t)
-}