diff --git a/lang/ast/structs.go b/lang/ast/structs.go
index 90510916..85e29944 100644
--- a/lang/ast/structs.go
+++ b/lang/ast/structs.go
@@ -3474,7 +3474,7 @@ func (obj *StmtProg) importSystemScope(name string) (*interfaces.Scope, error) {
 // importScopeWithInputs returns a local or remote scope from an inputs string.
 // The inputs string is the common frontend for a lot of our parsing decisions.
 func (obj *StmtProg) importScopeWithInputs(s string, scope *interfaces.Scope, parentVertex *pgraph.SelfVertex) (*interfaces.Scope, error) {
-	output, err := inputs.ParseInput(s, obj.data.Fs)
+	input, err := inputs.ParseInput(s, obj.data.Fs)
 	if err != nil {
 		return nil, errwrap.Wrapf(err, "could not activate an input parser")
 	}
@@ -3484,12 +3484,12 @@ func (obj *StmtProg) importScopeWithInputs(s string, scope *interfaces.Scope, pa
 	// run recursion detection by checking for duplicates in the seen files
 	// TODO: do the paths need to be cleaned for "../", etc before compare?
 	//for _, name := range obj.data.Files { // existing seen files
-	//	if util.StrInList(name, output.Files) {
+	//	if util.StrInList(name, input.Files) {
 	//		return nil, fmt.Errorf("recursive import of: `%s`", name)
 	//	}
 	//}
 
-	reader := bytes.NewReader(output.Main)
+	reader := bytes.NewReader(input.Main)
 
 	// nested logger
 	logf := func(format string, v ...interface{}) {
@@ -3498,11 +3498,11 @@ func (obj *StmtProg) importScopeWithInputs(s string, scope *interfaces.Scope, pa
 
 	// build new list of files
 	files := []string{}
-	files = append(files, output.Files...)
+	files = append(files, input.Files...)
 	files = append(files, obj.data.Files...)
 
 	// store a reference to the parent metadata
-	metadata := output.Metadata
+	metadata := input.Metadata
 	metadata.Metadata = obj.data.Metadata
 
 	// now run the lexer/parser to do the import
@@ -3518,9 +3518,9 @@ func (obj *StmtProg) importScopeWithInputs(s string, scope *interfaces.Scope, pa
 	// init and validate the structure of the AST
 	data := &interfaces.Data{
 		// TODO: add missing fields here if/when needed
-		Fs:       obj.data.Fs,
-		FsURI:    obj.data.FsURI,
-		Base:     output.Base, // new base dir (absolute path)
+		Fs:       input.FS,       // formerly: obj.data.Fs,
+		FsURI:    input.FS.URI(), // formerly: obj.data.FsURI,
+		Base:     input.Base,     // new base dir (absolute path)
 		Files:    files,
 		Imports:  parentVertex, // the parent vertex that imported me
 		Metadata: metadata,
@@ -3593,7 +3593,7 @@ func (obj *StmtProg) importScopeWithInputs(s string, scope *interfaces.Scope, pa
 	obj.importProgs = append(obj.importProgs, prog)
 
 	// collecting these here is more elegant (and possibly more efficient!)
-	obj.importFiles = append(obj.importFiles, output.Files...) // save for CollectFiles
+	obj.importFiles = append(obj.importFiles, input.Files...) // save for CollectFiles
 
 	return prog.scope, nil
 }
diff --git a/lang/gapi/gapi.go b/lang/gapi/gapi.go
index a85774a1..fb952a99 100644
--- a/lang/gapi/gapi.go
+++ b/lang/gapi/gapi.go
@@ -263,9 +263,9 @@ func (obj *GAPI) Cli(cliInfo *gapi.CliInfo) (*gapi.Deploy, error) {
 	// init and validate the structure of the AST
 	data := &interfaces.Data{
 		// TODO: add missing fields here if/when needed
-		Fs:       localFs,       // the local fs!
-		FsURI:    localFs.URI(), // TODO: is this right?
-		Base:     output.Base,   // base dir (absolute path) that this is rooted in
+		Fs:       output.FS,       // formerly: localFs // the local fs!
+		FsURI:    output.FS.URI(), // formerly: localFs.URI() // TODO: is this right?
+		Base:     output.Base,     // base dir (absolute path) that this is rooted in
 		Files:    output.Files,
 		Imports:  importVertex,
 		Metadata: output.Metadata,
@@ -770,9 +770,9 @@ func (obj *GAPI) Get(getInfo *gapi.GetInfo) error {
 	// init and validate the structure of the AST
 	data := &interfaces.Data{
 		// TODO: add missing fields here if/when needed
-		Fs:       localFs,       // the local fs!
-		FsURI:    localFs.URI(), // TODO: is this right?
-		Base:     output.Base,   // base dir (absolute path) that this is rooted in
+		Fs:       output.FS,       // formerly: localFs // the local fs!
+		FsURI:    output.FS.URI(), // formerly: localFs.URI() // TODO: is this right?
+		Base:     output.Base,     // base dir (absolute path) that this is rooted in
 		Files:    output.Files,
 		Imports:  importVertex,
 		Metadata: output.Metadata,
diff --git a/lang/inputs/inputs.go b/lang/inputs/inputs.go
index 6717956f..def251f4 100644
--- a/lang/inputs/inputs.go
+++ b/lang/inputs/inputs.go
@@ -66,9 +66,10 @@ var (
 // ParsedInput is the output struct which contains all the information we need.
 type ParsedInput struct {
 	//activated bool // if struct is not nil we're activated
-	Base     string   // base path (abs path with trailing slash)
-	Main     []byte   // contents of main entry mcl code
-	Files    []string // files and dirs to copy to fs (abs paths)
+	FS       engine.Fs // reference to the engine.Fs used to call the parse
+	Base     string    // base path (abs path with trailing slash)
+	Main     []byte    // contents of main entry mcl code
+	Files    []string  // files and dirs to copy to fs (abs paths)
 	Metadata *interfaces.Metadata
 	Workers  []func(engine.Fs) error // copy files here that aren't listed!
 }
@@ -214,6 +215,7 @@ func inputMetadata(s string, fs engine.Fs) (*ParsedInput, error) {
 		return nil, errwrap.Wrapf(err, "could not build metadata")
 	}
 	return &ParsedInput{
+		FS:       fs,
 		Base:     basePath,
 		Main:     b,
 		Files:    files,
@@ -261,6 +263,7 @@ func inputMcl(s string, fs engine.Fs) (*ParsedInput, error) {
 		},
 	}
 	return &ParsedInput{
+		FS:   fs,
 		Base: dirify(filepath.Dir(s)), // base path with trailing slash
 		Main: b,
 		Files: []string{
@@ -363,6 +366,7 @@ func inputCode(s string, fs engine.Fs) (*ParsedInput, error) {
 	}
 
 	return &ParsedInput{
+		FS:       fs,
 		Base:     dirify(wd),
 		Main:     b,
 		Files:    []string{}, // they're already copied in
diff --git a/lang/interpret_test.go b/lang/interpret_test.go
index 790b6b1a..e8cdc4d8 100644
--- a/lang/interpret_test.go
+++ b/lang/interpret_test.go
@@ -374,10 +374,10 @@ func TestAstFunc1(t *testing.T) {
 
 			data := &interfaces.Data{
 				// TODO: add missing fields here if/when needed
-				Fs:       fs,
-				FsURI:    fs.URI(),     // TODO: is this right?
-				Base:     output.Base,  // base dir (absolute path) the metadata file is in
-				Files:    output.Files, // no really needed here afaict
+				Fs:       output.FS,       // formerly: fs
+				FsURI:    output.FS.URI(), // formerly: fs.URI() // TODO: is this right?
+				Base:     output.Base,     // base dir (absolute path) the metadata file is in
+				Files:    output.Files,    // no really needed here afaict
 				Imports:  importVertex,
 				Metadata: output.Metadata,
 				Modules:  "/" + interfaces.ModuleDirectory, // not really needed here afaict
@@ -904,10 +904,10 @@ func TestAstFunc2(t *testing.T) {
 
 			data := &interfaces.Data{
 				// TODO: add missing fields here if/when needed
-				Fs:       fs,
-				FsURI:    "memmapfs:///", // we're in standalone mode
-				Base:     output.Base,    // base dir (absolute path) the metadata file is in
-				Files:    output.Files,   // no really needed here afaict
+				Fs:       output.FS, // formerly: fs
+				FsURI:    output.FS.URI(),
+				Base:     output.Base,  // base dir (absolute path) the metadata file is in
+				Files:    output.Files, // no really needed here afaict
 				Imports:  importVertex,
 				Metadata: output.Metadata,
 				Modules:  "/" + interfaces.ModuleDirectory, // not really needed here afaict
@@ -1706,10 +1706,10 @@ func TestAstFunc3(t *testing.T) {
 
 			data := &interfaces.Data{
 				// TODO: add missing fields here if/when needed
-				Fs:       fs,
-				FsURI:    "memmapfs:///", // we're in standalone mode
-				Base:     output.Base,    // base dir (absolute path) the metadata file is in
-				Files:    output.Files,   // no really needed here afaict
+				Fs:       output.FS, // formerly: fs
+				FsURI:    output.FS.URI(),
+				Base:     output.Base,  // base dir (absolute path) the metadata file is in
+				Files:    output.Files, // no really needed here afaict
 				Imports:  importVertex,
 				Metadata: output.Metadata,
 				Modules:  "/" + interfaces.ModuleDirectory, // not really needed here afaict
diff --git a/lang/lang.go b/lang/lang.go
index da4c5184..e99c271a 100644
--- a/lang/lang.go
+++ b/lang/lang.go
@@ -139,9 +139,9 @@ func (obj *Lang) Init() error {
 	// init and validate the structure of the AST
 	data := &interfaces.Data{
 		// TODO: add missing fields here if/when needed
-		Fs:       obj.Fs,
-		FsURI:    obj.FsURI,
-		Base:     output.Base, // base dir (absolute path) the metadata file is in
+		Fs:       output.FS,       // formerly: obj.Fs
+		FsURI:    output.FS.URI(), // formerly: obj.FsURI
+		Base:     output.Base,     // base dir (absolute path) the metadata file is in
 		Files:    output.Files,
 		Imports:  importVertex,
 		Metadata: output.Metadata,