diff --git a/.gitmodules b/.gitmodules
new file mode 100644
index 0000000..f71254f
--- /dev/null
+++ b/.gitmodules
@@ -0,0 +1,4 @@
+[submodule "external/go"]
+	path = external/go
+	url = https://github.com/dappcore/go.git
+	branch = dev
diff --git a/external/go b/external/go
new file mode 160000
index 0000000..d661b70
--- /dev/null
+++ b/external/go
@@ -0,0 +1 @@
+Subproject commit d661b703e16183b3cbab101de189f688888a1174
diff --git a/go.work b/go.work
new file mode 100644
index 0000000..ac2afa6
--- /dev/null
+++ b/go.work
@@ -0,0 +1,10 @@
+go 1.26.2
+
+// Workspace mode for development: pulls local Core modules from external/.
+//
+// CI should run with GOWORK=off so go/go.mod tags drive reproducible builds.
+
+use (
+	./go
+	./external/go
+)
diff --git a/actions.go b/go/actions.go
similarity index 98%
rename from actions.go
rename to go/actions.go
index a96058c..20791e5 100644
--- a/actions.go
+++ b/go/actions.go
@@ -209,7 +209,10 @@ func copyAction(_ context.Context, opts core.Options) core.Result {
 
 // localMediumFromOptions constructs a sandboxed local Medium using the
 // "root" option.
-func localMediumFromOptions(opts core.Options) (Medium, error) {
+func localMediumFromOptions(opts core.Options) (
+	Medium,
+	error,
+) {
 	root := opts.String("root")
 	if root == "" {
 		return nil, core.E("io.localMediumFromOptions", "root is required", fs.ErrInvalid)
@@ -217,7 +220,10 @@ func localMediumFromOptions(opts core.Options) (Medium, error) {
 	return NewSandboxed(root)
 }
 
-func mediumFromOptions(opts core.Options, operation string) (Medium, error) {
+func mediumFromOptions(opts core.Options, operation string) (
+	Medium,
+	error,
+) {
 	medium, ok := opts.Get("medium").Value.(Medium)
 	if !ok {
 		return nil, core.E(operation, "medium is required", fs.ErrInvalid)
diff --git a/actions_example_test.go b/go/actions_example_test.go
similarity index 100%
rename from actions_example_test.go
rename to go/actions_example_test.go
diff --git a/actions_test.go b/go/actions_test.go
similarity index 100%
rename from actions_test.go
rename to go/actions_test.go
diff --git a/bench_test.go b/go/bench_test.go
similarity index 100%
rename from bench_test.go
rename to go/bench_test.go
diff --git a/cube/actions.go b/go/cube/actions.go
similarity index 98%
rename from cube/actions.go
rename to go/cube/actions.go
index a970ccc..4f8fa17 100644
--- a/cube/actions.go
+++ b/go/cube/actions.go
@@ -157,7 +157,10 @@ func unpackAction(_ context.Context, opts core.Options) core.Result {
 	return core.Ok(nil)
 }
 
-func keyFromOptions(opts core.Options, operation string) ([]byte, error) {
+func keyFromOptions(opts core.Options, operation string) (
+	[]byte,
+	error,
+) {
 	key, ok := opts.Get("key").Value.([]byte)
 	if !ok {
 		return nil, core.E(operation, errKeyType, fs.ErrInvalid)
diff --git a/cube/actions_example_test.go b/go/cube/actions_example_test.go
similarity index 100%
rename from cube/actions_example_test.go
rename to go/cube/actions_example_test.go
diff --git a/cube/actions_test.go b/go/cube/actions_test.go
similarity index 100%
rename from cube/actions_test.go
rename to go/cube/actions_test.go
diff --git a/cube/cube.go b/go/cube/cube.go
similarity index 86%
rename from cube/cube.go
rename to go/cube/cube.go
index 9d47a33..ee1392e 100644
--- a/cube/cube.go
+++ b/go/cube/cube.go
@@ -48,7 +48,10 @@ type Options struct {
 // Example: medium, _ := cube.New(cube.Options{Inner: io.NewMemoryMedium(), Key: key})
 // Example: _ = medium.Write("secret.txt", "classified")
 // Example: plaintext, _ := medium.Read("secret.txt")
-func New(options Options) (*Medium, error) {
+func New(options Options) (
+	*Medium,
+	error,
+) {
 	if options.Inner == nil {
 		return nil, core.E(opCubeNew, "inner medium is required", fs.ErrInvalid)
 	}
@@ -68,7 +71,10 @@ func (medium *Medium) Inner() coreio.Medium {
 }
 
 // Example: content, _ := medium.Read("secret.txt")
-func (medium *Medium) Read(path string) (string, error) {
+func (medium *Medium) Read(path string) (
+	string,
+	error,
+) {
 	ciphertext, err := medium.inner.Read(path)
 	if err != nil {
 		return "", err
@@ -81,12 +87,14 @@ func (medium *Medium) Read(path string) (string, error) {
 }
 
 // Example: _ = medium.Write("secret.txt", "classified")
-func (medium *Medium) Write(path, content string) error {
+func (medium *Medium) Write(path, content string) error { // legacy error contract
+
 	return medium.WriteMode(path, content, 0644)
 }
 
 // Example: _ = medium.WriteMode("keys/private.key", key, 0600)
-func (medium *Medium) WriteMode(path, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(path, content string, mode fs.FileMode) error { // legacy error contract
+
 	ciphertext, err := sigil.Transmute([]byte(content), []sigil.Sigil{medium.sigil})
 	if err != nil {
 		return core.E("cube.WriteMode", core.Concat("failed to encrypt: ", path), err)
@@ -95,7 +103,8 @@ func (medium *Medium) WriteMode(path, content string, mode fs.FileMode) error {
 }
 
 // Example: _ = medium.EnsureDir("data")
-func (medium *Medium) EnsureDir(path string) error {
+func (medium *Medium) EnsureDir(path string) error { // legacy error contract
+
 	return medium.inner.EnsureDir(path)
 }
 
@@ -105,32 +114,44 @@ func (medium *Medium) IsFile(path string) bool {
 }
 
 // Example: _ = medium.Delete("secret.txt")
-func (medium *Medium) Delete(path string) error {
+func (medium *Medium) Delete(path string) error { // legacy error contract
+
 	return medium.inner.Delete(path)
 }
 
 // Example: _ = medium.DeleteAll("archive")
-func (medium *Medium) DeleteAll(path string) error {
+func (medium *Medium) DeleteAll(path string) error { // legacy error contract
+
 	return medium.inner.DeleteAll(path)
 }
 
 // Example: _ = medium.Rename("draft.txt", "final.txt")
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	return medium.inner.Rename(oldPath, newPath)
 }
 
 // Example: entries, _ := medium.List("data")
-func (medium *Medium) List(path string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(path string) (
+	[]fs.DirEntry,
+	error,
+) {
 	return medium.inner.List(path)
 }
 
 // Example: info, _ := medium.Stat("secret.txt")
-func (medium *Medium) Stat(path string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(path string) (
+	fs.FileInfo,
+	error,
+) {
 	return medium.inner.Stat(path)
 }
 
 // Example: file, _ := medium.Open("secret.txt")
-func (medium *Medium) Open(path string) (fs.File, error) {
+func (medium *Medium) Open(path string) (
+	fs.File,
+	error,
+) {
 	// Read via cube semantics (decrypt) then wrap in an in-memory fs.File.
 	ciphertext, err := medium.inner.Read(path)
 	if err != nil {
@@ -153,12 +174,18 @@ func (medium *Medium) Open(path string) (fs.File, error) {
 }
 
 // Example: writer, _ := medium.Create("secret.txt")
-func (medium *Medium) Create(path string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	return &cubeWriteCloser{medium: medium, path: path, mode: 0644}, nil
 }
 
 // Example: writer, _ := medium.Append("log.txt")
-func (medium *Medium) Append(path string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	var existing []byte
 	if medium.inner.Exists(path) {
 		plain, err := medium.Read(path)
@@ -171,7 +198,10 @@ func (medium *Medium) Append(path string) (goio.WriteCloser, error) {
 }
 
 // Example: reader, _ := medium.ReadStream("secret.txt")
-func (medium *Medium) ReadStream(path string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(path string) (
+	goio.ReadCloser,
+	error,
+) {
 	file, err := medium.Open(path)
 	if err != nil {
 		return nil, err
@@ -180,7 +210,10 @@ func (medium *Medium) ReadStream(path string) (goio.ReadCloser, error) {
 }
 
 // Example: writer, _ := medium.WriteStream("secret.txt")
-func (medium *Medium) WriteStream(path string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.Create(path)
 }
 
@@ -203,11 +236,17 @@ type cubeFile struct {
 	modTime time.Time
 }
 
-func (file *cubeFile) Stat() (fs.FileInfo, error) {
+func (file *cubeFile) Stat() (
+	fs.FileInfo,
+	error,
+) {
 	return coreio.NewFileInfo(file.name, int64(len(file.content)), file.mode, file.modTime, false), nil
 }
 
-func (file *cubeFile) Read(buffer []byte) (int, error) {
+func (file *cubeFile) Read(buffer []byte) (
+	int,
+	error,
+) {
 	if file.offset >= int64(len(file.content)) {
 		return 0, goio.EOF
 	}
@@ -216,7 +255,8 @@ func (file *cubeFile) Read(buffer []byte) (int, error) {
 	return readCount, nil
 }
 
-func (file *cubeFile) Close() error {
+func (file *cubeFile) Close() error { // legacy error contract
+
 	return nil
 }
 
@@ -225,7 +265,10 @@ type cubeArchiveBuffer struct {
 	data []byte
 }
 
-func (buffer *cubeArchiveBuffer) Write(data []byte) (int, error) {
+func (buffer *cubeArchiveBuffer) Write(data []byte) (
+	int,
+	error,
+) {
 	buffer.data = append(buffer.data, data...)
 	return len(data), nil
 }
@@ -238,12 +281,16 @@ type cubeWriteCloser struct {
 	mode   fs.FileMode
 }
 
-func (writer *cubeWriteCloser) Write(data []byte) (int, error) {
+func (writer *cubeWriteCloser) Write(data []byte) (
+	int,
+	error,
+) {
 	writer.data = append(writer.data, data...)
 	return len(data), nil
 }
 
-func (writer *cubeWriteCloser) Close() error {
+func (writer *cubeWriteCloser) Close() error { // legacy error contract
+
 	mode := writer.mode
 	if mode == 0 {
 		mode = 0644
@@ -255,7 +302,8 @@ func (writer *cubeWriteCloser) Close() error {
 //
 // Pack walks the source Medium, packs every file into a tar archive, encrypts
 // the archive, and writes the ciphertext to outputPath on the local filesystem.
-func Pack(outputPath string, source coreio.Medium, key []byte) error {
+func Pack(outputPath string, source coreio.Medium, key []byte) error { // legacy error contract
+
 	if source == nil {
 		return core.E(opCubePack, "source medium is required", fs.ErrInvalid)
 	}
@@ -286,7 +334,8 @@ func Pack(outputPath string, source coreio.Medium, key []byte) error {
 //
 // Unpack reads the encrypted archive from cubePath, decrypts it, unpacks the
 // tar contents, and writes every entry to the destination Medium.
-func Unpack(cubePath string, destination coreio.Medium, key []byte) error {
+func Unpack(cubePath string, destination coreio.Medium, key []byte) error { // legacy error contract
+
 	if destination == nil {
 		return core.E(opCubeUnpack, "destination medium is required", fs.ErrInvalid)
 	}
@@ -320,7 +369,10 @@ func Unpack(cubePath string, destination coreio.Medium, key []byte) error {
 // Open reads the encrypted archive at cubePath, decrypts it, and returns a
 // Medium backed by an in-memory node.Node. Reads and writes do not flow back
 // to the .cube file — use Pack again to persist updates.
-func Open(cubePath string, key []byte) (coreio.Medium, error) {
+func Open(cubePath string, key []byte) (
+	coreio.Medium,
+	error,
+) {
 	if cubePath == "" {
 		return nil, core.E(opCubeOpen, "cube path is required", fs.ErrInvalid)
 	}
@@ -353,14 +405,19 @@ func Open(cubePath string, key []byte) (coreio.Medium, error) {
 	return medium, nil
 }
 
-func validateCubeKey(operation string, key []byte) error {
+func validateCubeKey(operation string, key []byte) error { // legacy error contract
+
 	if _, err := sigil.NewChaChaPolySigil(key, nil); err != nil {
 		return core.E(operation, errCreateCipher, err)
 	}
 	return nil
 }
 
-func sandboxedLocalForPath(operation, filePath string) (coreio.Medium, string, error) {
+func sandboxedLocalForPath(operation, filePath string) (
+	coreio.Medium,
+	string,
+	error,
+) {
 	if filePath == "" {
 		return nil, "", core.E(operation, "path is required", fs.ErrInvalid)
 	}
@@ -398,7 +455,10 @@ func archiveChildPath(parent, name string) string {
 	return core.PathJoin(parent, name)
 }
 
-func archiveMediumToBorgDataNode(source coreio.Medium) (*borgdatanode.DataNode, error) {
+func archiveMediumToBorgDataNode(source coreio.Medium) (
+	*borgdatanode.DataNode,
+	error,
+) {
 	dataNode := borgdatanode.New()
 	if err := addMediumPathToBorgDataNode(source, "", dataNode); err != nil {
 		return nil, err
@@ -406,7 +466,8 @@ func archiveMediumToBorgDataNode(source coreio.Medium) (*borgdatanode.DataNode,
 	return dataNode, nil
 }
 
-func addMediumPathToBorgDataNode(source coreio.Medium, directoryPath string, dataNode *borgdatanode.DataNode) error {
+func addMediumPathToBorgDataNode(source coreio.Medium, directoryPath string, dataNode *borgdatanode.DataNode) error { // legacy error contract
+
 	entries, err := source.List(directoryPath)
 	if err != nil {
 		return core.E(opCubeArchive, core.Concat("failed to list: ", directoryPath), err)
@@ -428,14 +489,16 @@ func addMediumPathToBorgDataNode(source coreio.Medium, directoryPath string, dat
 	return nil
 }
 
-func writeBorgDataNodeToMedium(dataNode *borgdatanode.DataNode, destination coreio.Medium) error {
+func writeBorgDataNodeToMedium(dataNode *borgdatanode.DataNode, destination coreio.Medium) error { // legacy error contract
+
 	if dataNode == nil {
 		return core.E(opCubeExtract, "Borg DataNode is required", fs.ErrInvalid)
 	}
 	return writeBorgDataNodeDir(dataNode, "", destination)
 }
 
-func writeBorgDataNodeDir(dataNode *borgdatanode.DataNode, directoryPath string, destination coreio.Medium) error {
+func writeBorgDataNodeDir(dataNode *borgdatanode.DataNode, directoryPath string, destination coreio.Medium) error { // legacy error contract
+
 	entries, err := dataNode.ReadDir(directoryPath)
 	if err != nil {
 		return core.E(opCubeExtract, core.Concat("failed to list Borg DataNode: ", directoryPath), err)
@@ -455,7 +518,8 @@ func writeBorgDataNodeDir(dataNode *borgdatanode.DataNode, directoryPath string,
 	return nil
 }
 
-func writeBorgDataNodeFile(dataNode *borgdatanode.DataNode, filePath string, destination coreio.Medium) error {
+func writeBorgDataNodeFile(dataNode *borgdatanode.DataNode, filePath string, destination coreio.Medium) error { // legacy error contract
+
 	name, ok, err := validatedTarEntryName(filePath)
 	if err != nil || !ok {
 		return err
@@ -481,7 +545,11 @@ func closeBorgDataNodeFile(file fs.File, filePath string) {
 	}
 }
 
-func validatedTarEntryName(rawName string) (string, bool, error) {
+func validatedTarEntryName(rawName string) (
+	string,
+	bool,
+	error,
+) {
 	if rawName == "" {
 		return "", false, nil
 	}
diff --git a/cube/cube_example_test.go b/go/cube/cube_example_test.go
similarity index 100%
rename from cube/cube_example_test.go
rename to go/cube/cube_example_test.go
diff --git a/cube/cube_test.go b/go/cube/cube_test.go
similarity index 100%
rename from cube/cube_test.go
rename to go/cube/cube_test.go
diff --git a/datanode/medium.go b/go/datanode/medium.go
similarity index 89%
rename from datanode/medium.go
rename to go/datanode/medium.go
index d8dfb2e..3754e3f 100644
--- a/datanode/medium.go
+++ b/go/datanode/medium.go
@@ -64,7 +64,10 @@ func New() *Medium {
 // Example: sourceMedium := datanode.New()
 // Example: snapshot, _ := sourceMedium.Snapshot()
 // Example: restored, _ := datanode.FromTar(snapshot)
-func FromTar(data []byte) (*Medium, error) {
+func FromTar(data []byte) (
+	*Medium,
+	error,
+) {
 	dataNode, err := borgdatanode.FromTar(data)
 	if err != nil {
 		return nil, core.E("datanode.FromTar", "failed to restore", err)
@@ -78,7 +81,10 @@ func FromTar(data []byte) (*Medium, error) {
 }
 
 // Example: snapshot, _ := medium.Snapshot()
-func (medium *Medium) Snapshot() ([]byte, error) {
+func (medium *Medium) Snapshot() (
+	[]byte,
+	error,
+) {
 	medium.lock.RLock()
 	defer medium.lock.RUnlock()
 	data, err := medium.dataNode.ToTar()
@@ -89,7 +95,8 @@ func (medium *Medium) Snapshot() ([]byte, error) {
 }
 
 // Example: _ = medium.Restore(snapshot)
-func (medium *Medium) Restore(data []byte) error {
+func (medium *Medium) Restore(data []byte) error { // legacy error contract
+
 	dataNode, err := borgdatanode.FromTar(data)
 	if err != nil {
 		return core.E("datanode.Restore", "tar failed", err)
@@ -136,7 +143,10 @@ func closeDataNodeFile(file fs.File, filePath string) {
 	}
 }
 
-func (medium *Medium) Read(filePath string) (string, error) {
+func (medium *Medium) Read(filePath string) (
+	string,
+	error,
+) {
 	medium.lock.RLock()
 	defer medium.lock.RUnlock()
 
@@ -162,7 +172,8 @@ func (medium *Medium) Read(filePath string) (string, error) {
 	return string(data), nil
 }
 
-func (medium *Medium) Write(filePath, content string) error {
+func (medium *Medium) Write(filePath, content string) error { // legacy error contract
+
 	medium.lock.Lock()
 	defer medium.lock.Unlock()
 
@@ -176,11 +187,13 @@ func (medium *Medium) Write(filePath, content string) error {
 	return nil
 }
 
-func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error { // legacy error contract
+
 	return medium.Write(filePath, content)
 }
 
-func (medium *Medium) EnsureDir(filePath string) error {
+func (medium *Medium) EnsureDir(filePath string) error { // legacy error contract
+
 	medium.lock.Lock()
 	defer medium.lock.Unlock()
 
@@ -215,7 +228,8 @@ func (medium *Medium) isFileLocked(filePath string) bool {
 	return err == nil && !info.IsDir()
 }
 
-func (medium *Medium) Delete(filePath string) error {
+func (medium *Medium) Delete(filePath string) error { // legacy error contract
+
 	medium.lock.Lock()
 	defer medium.lock.Unlock()
 
@@ -239,14 +253,16 @@ func (medium *Medium) Delete(filePath string) error {
 	return nil
 }
 
-func (medium *Medium) deleteDirectoryFallbackLocked(filePath string) error {
+func (medium *Medium) deleteDirectoryFallbackLocked(filePath string) error { // legacy error contract
+
 	if medium.directorySet[filePath] {
 		return medium.deleteDirectoryLocked(filePath)
 	}
 	return core.E(opDatanodeDelete, core.Concat(msgDatanodeNotFound, filePath), fs.ErrNotExist)
 }
 
-func (medium *Medium) deleteDirectoryLocked(filePath string) error {
+func (medium *Medium) deleteDirectoryLocked(filePath string) error { // legacy error contract
+
 	hasChildren, err := medium.hasPrefixLocked(filePath + "/")
 	if err != nil {
 		return core.E(opDatanodeDelete, core.Concat("failed to inspect directory: ", filePath), err)
@@ -258,7 +274,8 @@ func (medium *Medium) deleteDirectoryLocked(filePath string) error {
 	return nil
 }
 
-func (medium *Medium) DeleteAll(filePath string) error {
+func (medium *Medium) DeleteAll(filePath string) error { // legacy error contract
+
 	medium.lock.Lock()
 	defer medium.lock.Unlock()
 
@@ -294,7 +311,10 @@ func (medium *Medium) DeleteAll(filePath string) error {
 	return nil
 }
 
-func (medium *Medium) deleteFileIfPresentLocked(filePath string) (bool, error) {
+func (medium *Medium) deleteFileIfPresentLocked(filePath string) (
+	bool,
+	error,
+) {
 	info, err := medium.dataNode.Stat(filePath)
 	if err != nil || info.IsDir() {
 		return false, nil
@@ -305,7 +325,10 @@ func (medium *Medium) deleteFileIfPresentLocked(filePath string) (bool, error) {
 	return true, nil
 }
 
-func (medium *Medium) deleteEntriesMatchingLocked(entries []string, filePath, prefix string) (bool, error) {
+func (medium *Medium) deleteEntriesMatchingLocked(entries []string, filePath, prefix string) (
+	bool,
+	error,
+) {
 	found := false
 	for _, name := range entries {
 		if name != filePath && !core.HasPrefix(name, prefix) {
@@ -330,7 +353,8 @@ func (medium *Medium) deleteDirectoriesMatchingLocked(filePath, prefix string) b
 	return found
 }
 
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	medium.lock.Lock()
 	defer medium.lock.Unlock()
 
@@ -349,7 +373,8 @@ func (medium *Medium) Rename(oldPath, newPath string) error {
 	return medium.renameDirectoryLocked(oldPath, newPath)
 }
 
-func (medium *Medium) renameFileLocked(oldPath, newPath string) error {
+func (medium *Medium) renameFileLocked(oldPath, newPath string) error { // legacy error contract
+
 	data, err := medium.readFileLocked(oldPath)
 	if err != nil {
 		return core.E(opDatanodeRename, core.Concat("failed to read source file: ", oldPath), err)
@@ -362,7 +387,8 @@ func (medium *Medium) renameFileLocked(oldPath, newPath string) error {
 	return nil
 }
 
-func (medium *Medium) renameDirectoryLocked(oldPath, newPath string) error {
+func (medium *Medium) renameDirectoryLocked(oldPath, newPath string) error { // legacy error contract
+
 	oldPrefix := oldPath + "/"
 	newPrefix := newPath + "/"
 
@@ -399,7 +425,10 @@ func (medium *Medium) renameDirectoryLocked(oldPath, newPath string) error {
 	return nil
 }
 
-func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(filePath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	medium.lock.RLock()
 	defer medium.lock.RUnlock()
 
@@ -444,7 +473,10 @@ func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
 	return entries, nil
 }
 
-func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(filePath string) (
+	fs.FileInfo,
+	error,
+) {
 	medium.lock.RLock()
 	defer medium.lock.RUnlock()
 
@@ -464,7 +496,10 @@ func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
 	return nil, core.E("datanode.Stat", core.Concat(msgDatanodeNotFound, filePath), fs.ErrNotExist)
 }
 
-func (medium *Medium) Open(filePath string) (fs.File, error) {
+func (medium *Medium) Open(filePath string) (
+	fs.File,
+	error,
+) {
 	medium.lock.RLock()
 	defer medium.lock.RUnlock()
 
@@ -472,7 +507,10 @@ func (medium *Medium) Open(filePath string) (fs.File, error) {
 	return medium.dataNode.Open(filePath)
 }
 
-func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	filePath = normaliseEntryPath(filePath)
 	if filePath == "" {
 		return nil, core.E("datanode.Create", msgDatanodeEmptyPath, fs.ErrInvalid)
@@ -480,7 +518,10 @@ func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
 	return &writeCloser{medium: medium, path: filePath}, nil
 }
 
-func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	filePath = normaliseEntryPath(filePath)
 	if filePath == "" {
 		return nil, core.E("datanode.Append", msgDatanodeEmptyPath, fs.ErrInvalid)
@@ -501,7 +542,10 @@ func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
 	return &writeCloser{medium: medium, path: filePath, buffer: existing}, nil
 }
 
-func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(filePath string) (
+	goio.ReadCloser,
+	error,
+) {
 	medium.lock.RLock()
 	defer medium.lock.RUnlock()
 
@@ -513,7 +557,10 @@ func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
 	return file.(goio.ReadCloser), nil
 }
 
-func (medium *Medium) WriteStream(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.Create(filePath)
 }
 
@@ -547,7 +594,10 @@ func (medium *Medium) IsDir(filePath string) bool {
 	return medium.directorySet[filePath]
 }
 
-func (medium *Medium) hasPrefixLocked(prefix string) (bool, error) {
+func (medium *Medium) hasPrefixLocked(prefix string) (
+	bool,
+	error,
+) {
 	entries, err := medium.collectAllLocked()
 	if err != nil {
 		return false, err
@@ -565,7 +615,10 @@ func (medium *Medium) hasPrefixLocked(prefix string) (bool, error) {
 	return false, nil
 }
 
-func (medium *Medium) collectAllLocked() ([]string, error) {
+func (medium *Medium) collectAllLocked() (
+	[]string,
+	error,
+) {
 	var names []string
 	err := dataNodeWalkDir(medium.dataNode, ".", func(filePath string, entry fs.DirEntry, err error) error {
 		if err != nil {
@@ -579,7 +632,10 @@ func (medium *Medium) collectAllLocked() ([]string, error) {
 	return names, err
 }
 
-func (medium *Medium) readFileLocked(filePath string) ([]byte, error) {
+func (medium *Medium) readFileLocked(filePath string) (
+	[]byte,
+	error,
+) {
 	file, err := dataNodeOpen(medium.dataNode, filePath)
 	if err != nil {
 		return nil, err
@@ -599,7 +655,8 @@ func (medium *Medium) readFileLocked(filePath string) ([]byte, error) {
 // This is O(n) per call, leading to O(n²) behaviour when deleting many files in a loop.
 // TODO(perf): use a DataNode deletion API if borgdatanode ever exposes one, or batch deletions
 // by collecting targets before rebuilding once.
-func (medium *Medium) removeFileLocked(target string) error {
+func (medium *Medium) removeFileLocked(target string) error { // legacy error contract
+
 	entries, err := medium.collectAllLocked()
 	if err != nil {
 		return err
@@ -625,12 +682,16 @@ type writeCloser struct {
 	buffer []byte
 }
 
-func (writer *writeCloser) Write(data []byte) (int, error) {
+func (writer *writeCloser) Write(data []byte) (
+	int,
+	error,
+) {
 	writer.buffer = append(writer.buffer, data...)
 	return len(data), nil
 }
 
-func (writer *writeCloser) Close() error {
+func (writer *writeCloser) Close() error { // legacy error contract
+
 	writer.medium.lock.Lock()
 	defer writer.medium.lock.Unlock()
 
@@ -649,7 +710,10 @@ func (entry *dirEntry) IsDir() bool { return true }
 
 func (entry *dirEntry) Type() fs.FileMode { return fs.ModeDir }
 
-func (entry *dirEntry) Info() (fs.FileInfo, error) {
+func (entry *dirEntry) Info() (
+	fs.FileInfo,
+	error,
+) {
 	return &fileInfo{name: entry.name, isDir: true, mode: fs.ModeDir | 0755}, nil
 }
 
diff --git a/datanode/medium_example_test.go b/go/datanode/medium_example_test.go
similarity index 100%
rename from datanode/medium_example_test.go
rename to go/datanode/medium_example_test.go
diff --git a/datanode/medium_test.go b/go/datanode/medium_test.go
similarity index 100%
rename from datanode/medium_test.go
rename to go/datanode/medium_test.go
diff --git a/doc.go b/go/doc.go
similarity index 100%
rename from doc.go
rename to go/doc.go
diff --git a/go.mod b/go/go.mod
similarity index 100%
rename from go.mod
rename to go/go.mod
diff --git a/go.sum b/go/go.sum
similarity index 100%
rename from go.sum
rename to go/go.sum
diff --git a/internal/fsutil/direntry.go b/go/internal/fsutil/direntry.go
similarity index 100%
rename from internal/fsutil/direntry.go
rename to go/internal/fsutil/direntry.go
diff --git a/internal/fsutil/direntry_example_test.go b/go/internal/fsutil/direntry_example_test.go
similarity index 100%
rename from internal/fsutil/direntry_example_test.go
rename to go/internal/fsutil/direntry_example_test.go
diff --git a/internal/fsutil/direntry_test.go b/go/internal/fsutil/direntry_test.go
similarity index 100%
rename from internal/fsutil/direntry_test.go
rename to go/internal/fsutil/direntry_test.go
diff --git a/io.go b/go/io.go
similarity index 91%
rename from io.go
rename to go/io.go
index c3249ed..875bb8d 100644
--- a/io.go
+++ b/go/io.go
@@ -148,32 +148,46 @@ func init() {
 
 // Example: medium, _ := io.NewSandboxed("/srv/app")
 // Example: _ = medium.Write("config/app.yaml", "port: 8080")
-func NewSandboxed(root string) (Medium, error) {
+func NewSandboxed(root string) (
+	Medium,
+	error,
+) {
 	return local.New(root)
 }
 
 // Example: content, _ := io.Read(medium, "config/app.yaml")
-func Read(medium Medium, path string) (string, error) {
+func Read(medium Medium, path string) (
+	string,
+	error,
+) {
 	return medium.Read(path)
 }
 
 // Example: _ = io.Write(medium, "config/app.yaml", "port: 8080")
-func Write(medium Medium, path, content string) error {
+func Write(medium Medium, path, content string) error { // legacy error contract
+
 	return medium.Write(path, content)
 }
 
 // Example: reader, _ := io.ReadStream(medium, "logs/app.log")
-func ReadStream(medium Medium, path string) (goio.ReadCloser, error) {
+func ReadStream(medium Medium, path string) (
+	goio.ReadCloser,
+	error,
+) {
 	return medium.ReadStream(path)
 }
 
 // Example: writer, _ := io.WriteStream(medium, "logs/app.log")
-func WriteStream(medium Medium, path string) (goio.WriteCloser, error) {
+func WriteStream(medium Medium, path string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.WriteStream(path)
 }
 
 // Example: _ = io.EnsureDir(medium, "config")
-func EnsureDir(medium Medium, path string) error {
+func EnsureDir(medium Medium, path string) error { // legacy error contract
+
 	return medium.EnsureDir(path)
 }
 
@@ -183,7 +197,8 @@ func IsFile(medium Medium, path string) bool {
 }
 
 // Example: _ = io.Copy(sourceMedium, "input.txt", destinationMedium, "backup/input.txt")
-func Copy(sourceMedium Medium, sourcePath string, destinationMedium Medium, destinationPath string) error {
+func Copy(sourceMedium Medium, sourcePath string, destinationMedium Medium, destinationPath string) error { // legacy error contract
+
 	content, err := sourceMedium.Read(sourcePath)
 	if err != nil {
 		return core.E("io.Copy", core.Concat("read failed: ", sourcePath), err)
@@ -261,7 +276,10 @@ func (medium *MemoryMedium) directoryExists(path string) bool {
 }
 
 // Example: value, _ := io.NewMemoryMedium().Read("notes.txt")
-func (medium *MemoryMedium) Read(path string) (string, error) {
+func (medium *MemoryMedium) Read(path string) (
+	string,
+	error,
+) {
 	content, ok := medium.fileContents[path]
 	if !ok {
 		return "", core.E("io.MemoryMedium.Read", core.Concat("file not found: ", path), fs.ErrNotExist)
@@ -270,12 +288,14 @@ func (medium *MemoryMedium) Read(path string) (string, error) {
 }
 
 // Example: _ = io.NewMemoryMedium().Write("notes.txt", "hello")
-func (medium *MemoryMedium) Write(path, content string) error {
+func (medium *MemoryMedium) Write(path, content string) error { // legacy error contract
+
 	return medium.WriteMode(path, content, 0644)
 }
 
 // Example: _ = io.NewMemoryMedium().WriteMode("keys/private.key", "secret", 0600)
-func (medium *MemoryMedium) WriteMode(filePath, content string, mode fs.FileMode) error {
+func (medium *MemoryMedium) WriteMode(filePath, content string, mode fs.FileMode) error { // legacy error contract
+
 	// Verify no ancestor directory component is stored as a file.
 	ancestor := core.PathDir(filePath)
 	for ancestor != "." && ancestor != "" {
@@ -299,7 +319,8 @@ func (medium *MemoryMedium) WriteMode(filePath, content string, mode fs.FileMode
 }
 
 // Example: _ = io.NewMemoryMedium().EnsureDir("config/app")
-func (medium *MemoryMedium) EnsureDir(path string) error {
+func (medium *MemoryMedium) EnsureDir(path string) error { // legacy error contract
+
 	if _, ok := medium.fileContents[path]; ok {
 		return core.E("io.MemoryMedium.EnsureDir", core.Concat("path is already a file: ", path), fs.ErrExist)
 	}
@@ -315,7 +336,8 @@ func (medium *MemoryMedium) IsFile(path string) bool {
 }
 
 // Example: _ = io.NewMemoryMedium().Delete("old.txt")
-func (medium *MemoryMedium) Delete(path string) error {
+func (medium *MemoryMedium) Delete(path string) error { // legacy error contract
+
 	if _, ok := medium.fileContents[path]; ok {
 		delete(medium.fileContents, path)
 		delete(medium.fileModes, path)
@@ -356,7 +378,8 @@ func (medium *MemoryMedium) directoryHasChildren(path string) bool {
 }
 
 // Example: _ = io.NewMemoryMedium().DeleteAll("logs")
-func (medium *MemoryMedium) DeleteAll(path string) error {
+func (medium *MemoryMedium) DeleteAll(path string) error { // legacy error contract
+
 	found := false
 	if _, ok := medium.fileContents[path]; ok {
 		delete(medium.fileContents, path)
@@ -394,7 +417,8 @@ func (medium *MemoryMedium) DeleteAll(path string) error {
 }
 
 // Example: _ = io.NewMemoryMedium().Rename("drafts/todo.txt", "archive/todo.txt")
-func (medium *MemoryMedium) Rename(oldPath, newPath string) error {
+func (medium *MemoryMedium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	if medium.renameFile(oldPath, newPath) {
 		return nil
 	}
@@ -468,7 +492,10 @@ func (medium *MemoryMedium) renameDirectoriesWithPrefix(oldPrefix, newPrefix str
 }
 
 // Example: file, _ := io.NewMemoryMedium().Open("notes.txt")
-func (medium *MemoryMedium) Open(path string) (fs.File, error) {
+func (medium *MemoryMedium) Open(path string) (
+	fs.File,
+	error,
+) {
 	content, ok := medium.fileContents[path]
 	if !ok {
 		return nil, core.E("io.MemoryMedium.Open", core.Concat("file not found: ", path), fs.ErrNotExist)
@@ -482,7 +509,10 @@ func (medium *MemoryMedium) Open(path string) (fs.File, error) {
 }
 
 // Example: writer, _ := io.NewMemoryMedium().Create("notes.txt")
-func (medium *MemoryMedium) Create(path string) (goio.WriteCloser, error) {
+func (medium *MemoryMedium) Create(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	return &MemoryWriteCloser{
 		medium: medium,
 		path:   path,
@@ -491,7 +521,10 @@ func (medium *MemoryMedium) Create(path string) (goio.WriteCloser, error) {
 }
 
 // Example: writer, _ := io.NewMemoryMedium().Append("notes.txt")
-func (medium *MemoryMedium) Append(path string) (goio.WriteCloser, error) {
+func (medium *MemoryMedium) Append(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	content := medium.fileContents[path]
 	return &MemoryWriteCloser{
 		medium: medium,
@@ -502,12 +535,18 @@ func (medium *MemoryMedium) Append(path string) (goio.WriteCloser, error) {
 }
 
 // Example: reader, _ := io.NewMemoryMedium().ReadStream("notes.txt")
-func (medium *MemoryMedium) ReadStream(path string) (goio.ReadCloser, error) {
+func (medium *MemoryMedium) ReadStream(path string) (
+	goio.ReadCloser,
+	error,
+) {
 	return medium.Open(path)
 }
 
 // Example: writer, _ := io.NewMemoryMedium().WriteStream("notes.txt")
-func (medium *MemoryMedium) WriteStream(path string) (goio.WriteCloser, error) {
+func (medium *MemoryMedium) WriteStream(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.Create(path)
 }
 
@@ -523,11 +562,17 @@ type MemoryFile struct {
 var _ fs.File = (*MemoryFile)(nil)
 var _ goio.ReadCloser = (*MemoryFile)(nil)
 
-func (file *MemoryFile) Stat() (fs.FileInfo, error) {
+func (file *MemoryFile) Stat() (
+	fs.FileInfo,
+	error,
+) {
 	return NewFileInfo(file.name, int64(len(file.content)), file.mode, file.modTime, false), nil
 }
 
-func (file *MemoryFile) Read(buffer []byte) (int, error) {
+func (file *MemoryFile) Read(buffer []byte) (
+	int,
+	error,
+) {
 	if file.offset >= int64(len(file.content)) {
 		return 0, goio.EOF
 	}
@@ -536,7 +581,8 @@ func (file *MemoryFile) Read(buffer []byte) (int, error) {
 	return readCount, nil
 }
 
-func (file *MemoryFile) Close() error {
+func (file *MemoryFile) Close() error { // legacy error contract
+
 	return nil
 }
 
@@ -550,12 +596,16 @@ type MemoryWriteCloser struct {
 
 var _ goio.WriteCloser = (*MemoryWriteCloser)(nil)
 
-func (writeCloser *MemoryWriteCloser) Write(data []byte) (int, error) {
+func (writeCloser *MemoryWriteCloser) Write(data []byte) (
+	int,
+	error,
+) {
 	writeCloser.data = append(writeCloser.data, data...)
 	return len(data), nil
 }
 
-func (writeCloser *MemoryWriteCloser) Close() error {
+func (writeCloser *MemoryWriteCloser) Close() error { // legacy error contract
+
 	if _, ok := writeCloser.medium.directories[writeCloser.path]; ok {
 		return core.E("io.MemoryWriteCloser.Close", core.Concat("path is a directory: ", writeCloser.path), fs.ErrExist)
 	}
@@ -581,7 +631,10 @@ func (medium *MemoryMedium) modificationTimeForPath(path string) time.Time {
 }
 
 // Example: entries, _ := io.NewMemoryMedium().List("config")
-func (medium *MemoryMedium) List(path string) ([]fs.DirEntry, error) {
+func (medium *MemoryMedium) List(path string) (
+	[]fs.DirEntry,
+	error,
+) {
 	if _, ok := medium.directories[path]; !ok {
 		if !medium.hasChildrenAtPath(path) && path != "" {
 			return nil, core.E("io.MemoryMedium.List", core.Concat("directory not found: ", path), fs.ErrNotExist)
@@ -678,7 +731,10 @@ func memoryDirEntry(name string) fs.DirEntry {
 }
 
 // Example: info, _ := io.NewMemoryMedium().Stat("notes.txt")
-func (medium *MemoryMedium) Stat(path string) (fs.FileInfo, error) {
+func (medium *MemoryMedium) Stat(path string) (
+	fs.FileInfo,
+	error,
+) {
 	if content, ok := medium.fileContents[path]; ok {
 		modTime, ok := medium.modificationTimes[path]
 		if !ok {
diff --git a/io_example_test.go b/go/io_example_test.go
similarity index 100%
rename from io_example_test.go
rename to go/io_example_test.go
diff --git a/io_test.go b/go/io_test.go
similarity index 100%
rename from io_test.go
rename to go/io_test.go
diff --git a/local/medium.go b/go/local/medium.go
similarity index 89%
rename from local/medium.go
rename to go/local/medium.go
index a6bf896..6f0ca6e 100644
--- a/local/medium.go
+++ b/go/local/medium.go
@@ -31,7 +31,10 @@ const (
 
 // Example: medium, _ := local.New("/srv/app")
 // Example: _ = medium.Write("config/app.yaml", "port: 8080")
-func New(root string) (*Medium, error) {
+func New(root string) (
+	*Medium,
+	error,
+) {
 	absoluteRoot := absolutePath(root)
 	if resolvedRoot, err := resolveSymlinksPath(absoluteRoot); err == nil {
 		absoluteRoot = resolvedRoot
@@ -94,11 +97,17 @@ func splitPathParts(path string) []string {
 	return parts
 }
 
-func resolveSymlinksPath(path string) (string, error) {
+func resolveSymlinksPath(path string) (
+	string,
+	error,
+) {
 	return resolveSymlinksRecursive(absolutePath(path), map[string]struct{}{})
 }
 
-func resolveSymlinksRecursive(path string, seen map[string]struct{}) (string, error) {
+func resolveSymlinksRecursive(path string, seen map[string]struct{}) (
+	string,
+	error,
+) {
 	path = core.Path(path)
 	if path == dirSeparator() {
 		return path, nil
@@ -130,7 +139,10 @@ func resolveSymlinksRecursive(path string, seen map[string]struct{}) (string, er
 	return current, nil
 }
 
-func resolveSymlinkTarget(current, next string, seen map[string]struct{}) (string, error) {
+func resolveSymlinkTarget(current, next string, seen map[string]struct{}) (
+	string,
+	error,
+) {
 	target, err := readlink(next)
 	if err != nil {
 		return "", err
@@ -218,7 +230,10 @@ func (medium *Medium) sandboxedPath(path string) string {
 // directory component with O_NOFOLLOW (openat-style) so that the resolved fd is used for the
 // next step rather than re-resolving from a path string. Until then, symlink-based escape is
 // only possible on systems where an attacker can swap filesystem objects between syscalls.
-func (medium *Medium) validatePath(path string) (string, error) {
+func (medium *Medium) validatePath(path string) (
+	string,
+	error,
+) {
 	if medium.filesystemRoot == dirSeparator() {
 		return medium.sandboxedPath(path), nil
 	}
@@ -247,7 +262,10 @@ func (medium *Medium) validatePath(path string) (string, error) {
 	return current, nil
 }
 
-func (medium *Medium) Read(path string) (string, error) {
+func (medium *Medium) Read(path string) (
+	string,
+	error,
+) {
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return "", err
@@ -255,11 +273,13 @@ func (medium *Medium) Read(path string) (string, error) {
 	return resultString("local.Read", core.Concat("read failed: ", path), unrestrictedFileSystem.Read(resolvedPath))
 }
 
-func (medium *Medium) Write(path, content string) error {
+func (medium *Medium) Write(path, content string) error { // legacy error contract
+
 	return medium.WriteMode(path, content, 0644)
 }
 
-func (medium *Medium) WriteMode(path, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(path, content string, mode fs.FileMode) error { // legacy error contract
+
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return err
@@ -268,7 +288,8 @@ func (medium *Medium) WriteMode(path, content string, mode fs.FileMode) error {
 }
 
 // Example: _ = medium.EnsureDir("config/app")
-func (medium *Medium) EnsureDir(path string) error {
+func (medium *Medium) EnsureDir(path string) error { // legacy error contract
+
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return err
@@ -310,7 +331,10 @@ func (medium *Medium) Exists(path string) bool {
 }
 
 // Example: entries, _ := medium.List("config")
-func (medium *Medium) List(path string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(path string) (
+	[]fs.DirEntry,
+	error,
+) {
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return nil, err
@@ -328,7 +352,10 @@ func (medium *Medium) List(path string) ([]fs.DirEntry, error) {
 }
 
 // Example: info, _ := medium.Stat("config/app.yaml")
-func (medium *Medium) Stat(path string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(path string) (
+	fs.FileInfo,
+	error,
+) {
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return nil, err
@@ -337,7 +364,10 @@ func (medium *Medium) Stat(path string) (fs.FileInfo, error) {
 }
 
 // Example: file, _ := medium.Open("config/app.yaml")
-func (medium *Medium) Open(path string) (fs.File, error) {
+func (medium *Medium) Open(path string) (
+	fs.File,
+	error,
+) {
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return nil, err
@@ -346,7 +376,10 @@ func (medium *Medium) Open(path string) (fs.File, error) {
 }
 
 // Example: writer, _ := medium.Create("logs/app.log")
-func (medium *Medium) Create(path string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return nil, err
@@ -355,7 +388,10 @@ func (medium *Medium) Create(path string) (goio.WriteCloser, error) {
 }
 
 // Example: writer, _ := medium.Append("logs/app.log")
-func (medium *Medium) Append(path string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return nil, err
@@ -364,17 +400,24 @@ func (medium *Medium) Append(path string) (goio.WriteCloser, error) {
 }
 
 // Example: reader, _ := medium.ReadStream("logs/app.log")
-func (medium *Medium) ReadStream(path string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(path string) (
+	goio.ReadCloser,
+	error,
+) {
 	return medium.Open(path)
 }
 
 // Example: writer, _ := medium.WriteStream("logs/app.log")
-func (medium *Medium) WriteStream(path string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.Create(path)
 }
 
 // Example: _ = medium.Delete("config/app.yaml")
-func (medium *Medium) Delete(path string) error {
+func (medium *Medium) Delete(path string) error { // legacy error contract
+
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return err
@@ -389,7 +432,8 @@ func (medium *Medium) Delete(path string) error {
 }
 
 // Example: _ = medium.DeleteAll("logs/archive")
-func (medium *Medium) DeleteAll(path string) error {
+func (medium *Medium) DeleteAll(path string) error { // legacy error contract
+
 	resolvedPath, err := medium.validatePath(path)
 	if err != nil {
 		return err
@@ -404,7 +448,8 @@ func (medium *Medium) DeleteAll(path string) error {
 }
 
 // Example: _ = medium.Rename("drafts/todo.txt", "archive/todo.txt")
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	oldResolvedPath, err := medium.validatePath(oldPath)
 	if err != nil {
 		return err
@@ -416,7 +461,10 @@ func (medium *Medium) Rename(oldPath, newPath string) error {
 	return resultError("local.Rename", core.Concat("rename failed: ", oldPath), unrestrictedFileSystem.Rename(oldResolvedPath, newResolvedPath))
 }
 
-func lstat(path string) (*syscall.Stat_t, error) {
+func lstat(path string) (
+	*syscall.Stat_t,
+	error,
+) {
 	info := &syscall.Stat_t{}
 	if err := syscall.Lstat(path, info); err != nil {
 		return nil, err
@@ -431,7 +479,10 @@ func isSymlink(mode uint32) bool {
 	return mode&syscall.S_IFMT == syscall.S_IFLNK
 }
 
-func readlink(path string) (string, error) {
+func readlink(path string) (
+	string,
+	error,
+) {
 	size := 256
 	for {
 		linkBuffer := make([]byte, size)
@@ -446,7 +497,8 @@ func readlink(path string) (string, error) {
 	}
 }
 
-func resultError(operation, message string, result core.Result) error {
+func resultError(operation, message string, result core.Result) error { // legacy error contract
+
 	if result.OK {
 		return nil
 	}
@@ -456,7 +508,10 @@ func resultError(operation, message string, result core.Result) error {
 	return core.E(operation, message, nil)
 }
 
-func resultString(operation, message string, result core.Result) (string, error) {
+func resultString(operation, message string, result core.Result) (
+	string,
+	error,
+) {
 	if !result.OK {
 		return "", resultError(operation, message, result)
 	}
@@ -467,7 +522,10 @@ func resultString(operation, message string, result core.Result) (string, error)
 	return value, nil
 }
 
-func resultDirEntries(operation, message string, result core.Result) ([]fs.DirEntry, error) {
+func resultDirEntries(operation, message string, result core.Result) (
+	[]fs.DirEntry,
+	error,
+) {
 	if !result.OK {
 		return nil, resultError(operation, message, result)
 	}
@@ -478,7 +536,10 @@ func resultDirEntries(operation, message string, result core.Result) ([]fs.DirEn
 	return entries, nil
 }
 
-func resultFileInfo(operation, message string, result core.Result) (fs.FileInfo, error) {
+func resultFileInfo(operation, message string, result core.Result) (
+	fs.FileInfo,
+	error,
+) {
 	if !result.OK {
 		return nil, resultError(operation, message, result)
 	}
@@ -489,7 +550,10 @@ func resultFileInfo(operation, message string, result core.Result) (fs.FileInfo,
 	return fileInfo, nil
 }
 
-func resultFile(operation, message string, result core.Result) (fs.File, error) {
+func resultFile(operation, message string, result core.Result) (
+	fs.File,
+	error,
+) {
 	if !result.OK {
 		return nil, resultError(operation, message, result)
 	}
@@ -500,7 +564,10 @@ func resultFile(operation, message string, result core.Result) (fs.File, error)
 	return file, nil
 }
 
-func resultWriteCloser(operation, message string, result core.Result) (goio.WriteCloser, error) {
+func resultWriteCloser(operation, message string, result core.Result) (
+	goio.WriteCloser,
+	error,
+) {
 	if !result.OK {
 		return nil, resultError(operation, message, result)
 	}
diff --git a/local/medium_example_test.go b/go/local/medium_example_test.go
similarity index 100%
rename from local/medium_example_test.go
rename to go/local/medium_example_test.go
diff --git a/local/medium_test.go b/go/local/medium_test.go
similarity index 100%
rename from local/medium_test.go
rename to go/local/medium_test.go
diff --git a/medium_test.go b/go/medium_test.go
similarity index 100%
rename from medium_test.go
rename to go/medium_test.go
diff --git a/mock.go b/go/mock.go
similarity index 85%
rename from mock.go
rename to go/mock.go
index 6c68a1a..4c38c0e 100644
--- a/mock.go
+++ b/go/mock.go
@@ -51,7 +51,10 @@ func NewMockMedium() *MockMedium {
 
 var _ Medium = (*MockMedium)(nil)
 
-func (m *MockMedium) Read(path string) (string, error) {
+func (m *MockMedium) Read(path string) (
+	string,
+	error,
+) {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 	content, ok := m.Files[path]
@@ -61,11 +64,13 @@ func (m *MockMedium) Read(path string) (string, error) {
 	return content, nil
 }
 
-func (m *MockMedium) Write(path, content string) error {
+func (m *MockMedium) Write(path, content string) error { // legacy error contract
+
 	return m.WriteMode(path, content, 0644)
 }
 
-func (m *MockMedium) WriteMode(path, content string, mode fs.FileMode) error {
+func (m *MockMedium) WriteMode(path, content string, mode fs.FileMode) error { // legacy error contract
+
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	m.Files[path] = content
@@ -73,7 +78,8 @@ func (m *MockMedium) WriteMode(path, content string, mode fs.FileMode) error {
 	return nil
 }
 
-func (m *MockMedium) EnsureDir(path string) error {
+func (m *MockMedium) EnsureDir(path string) error { // legacy error contract
+
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	m.dirs[path] = true
@@ -87,7 +93,8 @@ func (m *MockMedium) IsFile(path string) bool {
 	return ok
 }
 
-func (m *MockMedium) Delete(path string) error {
+func (m *MockMedium) Delete(path string) error { // legacy error contract
+
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	if _, ok := m.Files[path]; ok {
@@ -102,7 +109,8 @@ func (m *MockMedium) Delete(path string) error {
 	return fs.ErrNotExist
 }
 
-func (m *MockMedium) DeleteAll(path string) error {
+func (m *MockMedium) DeleteAll(path string) error { // legacy error contract
+
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	found := false
@@ -125,7 +133,8 @@ func (m *MockMedium) DeleteAll(path string) error {
 	return nil
 }
 
-func (m *MockMedium) Rename(oldPath, newPath string) error {
+func (m *MockMedium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	m.mu.Lock()
 	defer m.mu.Unlock()
 	f, ok := m.Files[oldPath]
@@ -141,7 +150,10 @@ func (m *MockMedium) Rename(oldPath, newPath string) error {
 	return nil
 }
 
-func (m *MockMedium) List(path string) ([]fs.DirEntry, error) {
+func (m *MockMedium) List(path string) (
+	[]fs.DirEntry,
+	error,
+) {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 	prefix := mockListPrefix(path)
@@ -217,7 +229,10 @@ func appendMockDirectoryEntry(entries []fs.DirEntry, seen map[string]bool, name
 	return append(entries, NewDirEntry(name, true, 0755, NewFileInfo(name, 0, 0755, time.Now(), true)))
 }
 
-func (m *MockMedium) Stat(path string) (fs.FileInfo, error) {
+func (m *MockMedium) Stat(path string) (
+	fs.FileInfo,
+	error,
+) {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 	if content, ok := m.Files[path]; ok {
@@ -230,7 +245,10 @@ func (m *MockMedium) Stat(path string) (fs.FileInfo, error) {
 	return nil, fs.ErrNotExist
 }
 
-func (m *MockMedium) Open(path string) (fs.File, error) {
+func (m *MockMedium) Open(path string) (
+	fs.File,
+	error,
+) {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 	content, ok := m.Files[path]
@@ -241,18 +259,27 @@ func (m *MockMedium) Open(path string) (fs.File, error) {
 	return &MockFile{reader: core.NewReader(content), info: NewFileInfo(core.PathBase(path), int64(len(content)), mt.mode, mt.modTime, false)}, nil
 }
 
-func (m *MockMedium) Create(path string) (goio.WriteCloser, error) {
+func (m *MockMedium) Create(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	return &MockWriteCloser{medium: m, path: path}, nil
 }
 
-func (m *MockMedium) Append(path string) (goio.WriteCloser, error) {
+func (m *MockMedium) Append(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	m.mu.RLock()
 	existing := m.Files[path]
 	m.mu.RUnlock()
 	return &MockWriteCloser{medium: m, path: path, data: []byte(existing)}, nil
 }
 
-func (m *MockMedium) ReadStream(path string) (goio.ReadCloser, error) {
+func (m *MockMedium) ReadStream(path string) (
+	goio.ReadCloser,
+	error,
+) {
 	m.mu.RLock()
 	defer m.mu.RUnlock()
 	f, ok := m.Files[path]
@@ -262,7 +289,10 @@ func (m *MockMedium) ReadStream(path string) (goio.ReadCloser, error) {
 	return goio.NopCloser(core.NewReader(f)), nil
 }
 
-func (m *MockMedium) WriteStream(path string) (goio.WriteCloser, error) {
+func (m *MockMedium) WriteStream(path string) (
+	goio.WriteCloser,
+	error,
+) {
 	return m.Create(path)
 }
 
@@ -308,11 +338,15 @@ type MockWriteCloser struct {
 	data   []byte
 }
 
-func (w *MockWriteCloser) Write(p []byte) (int, error) {
+func (w *MockWriteCloser) Write(p []byte) (
+	int,
+	error,
+) {
 	w.data = append(w.data, p...)
 	return len(p), nil
 }
 
-func (w *MockWriteCloser) Close() error {
+func (w *MockWriteCloser) Close() error { // legacy error contract
+
 	return w.medium.Write(w.path, string(w.data))
 }
diff --git a/mock_example_test.go b/go/mock_example_test.go
similarity index 100%
rename from mock_example_test.go
rename to go/mock_example_test.go
diff --git a/mock_test.go b/go/mock_test.go
similarity index 100%
rename from mock_test.go
rename to go/mock_test.go
diff --git a/node/node.go b/go/node/node.go
similarity index 89%
rename from node/node.go
rename to go/node/node.go
index b820670..40d11aa 100644
--- a/node/node.go
+++ b/go/node/node.go
@@ -45,7 +45,10 @@ type nodeArchiveBuffer struct {
 	data []byte
 }
 
-func (buffer *nodeArchiveBuffer) Write(data []byte) (int, error) {
+func (buffer *nodeArchiveBuffer) Write(data []byte) (
+	int,
+	error,
+) {
 	buffer.data = append(buffer.data, data...)
 	return len(data), nil
 }
@@ -67,7 +70,10 @@ func (node *Node) AddData(name string, content []byte) {
 }
 
 // Example: snapshot, _ := nodeTree.ToTar()
-func (node *Node) ToTar() ([]byte, error) {
+func (node *Node) ToTar() (
+	[]byte,
+	error,
+) {
 	buffer := &nodeArchiveBuffer{}
 	tarWriter := tar.NewWriter(buffer)
 
@@ -94,7 +100,10 @@ func (node *Node) ToTar() ([]byte, error) {
 }
 
 // Example: restored, _ := node.FromTar(snapshot)
-func FromTar(data []byte) (*Node, error) {
+func FromTar(data []byte) (
+	*Node,
+	error,
+) {
 	restoredNode := New()
 	if err := restoredNode.LoadTar(data); err != nil {
 		return nil, err
@@ -103,7 +112,8 @@ func FromTar(data []byte) (*Node, error) {
 }
 
 // Example: _ = nodeTree.LoadTar(snapshot)
-func (node *Node) LoadTar(data []byte) error {
+func (node *Node) LoadTar(data []byte) error { // legacy error contract
+
 	newFiles := make(map[string]*dataFile)
 	tarReader := tar.NewReader(core.NewReader(string(data)))
 
@@ -132,7 +142,10 @@ func (node *Node) LoadTar(data []byte) error {
 	return nil
 }
 
-func dataFileFromTarEntry(tarReader *tar.Reader, header *tar.Header) (*dataFile, error) {
+func dataFileFromTarEntry(tarReader *tar.Reader, header *tar.Header) (
+	*dataFile,
+	error,
+) {
 	contentResult := core.ReadAll(tarReader)
 	if !contentResult.OK {
 		if err, ok := contentResult.Value.(error); ok {
@@ -159,7 +172,8 @@ type WalkOptions struct {
 }
 
 // Example: _ = nodeTree.Walk(".", func(_ string, _ fs.DirEntry, _ error) error { return nil }, node.WalkOptions{MaxDepth: 1, SkipErrors: true})
-func (node *Node) Walk(root string, walkFunc fs.WalkDirFunc, options WalkOptions) error {
+func (node *Node) Walk(root string, walkFunc fs.WalkDirFunc, options WalkOptions) error { // legacy error contract
+
 	if options.SkipErrors {
 		if _, err := node.Stat(root); err != nil {
 			return nil
@@ -181,7 +195,10 @@ func (node *Node) Walk(root string, walkFunc fs.WalkDirFunc, options WalkOptions
 	})
 }
 
-func walkFilterDecision(entryPath string, entry fs.DirEntry, err error, filter func(string, fs.DirEntry) bool) (bool, error) {
+func walkFilterDecision(entryPath string, entry fs.DirEntry, err error, filter func(string, fs.DirEntry) bool) (
+	bool,
+	error,
+) {
 	if filter == nil || err != nil || filter(entryPath, entry) {
 		return false, nil
 	}
@@ -211,7 +228,10 @@ func pathDepth(path string) int {
 }
 
 // Example: content, _ := nodeTree.ReadFile("config/app.yaml")
-func (node *Node) ReadFile(name string) ([]byte, error) {
+func (node *Node) ReadFile(name string) (
+	[]byte,
+	error,
+) {
 	name = core.TrimPrefix(name, "/")
 	file, ok := node.files[name]
 	if !ok {
@@ -225,7 +245,8 @@ func (node *Node) ReadFile(name string) ([]byte, error) {
 // ExportFile writes a node file to the local filesystem. It operates on coreio.Local directly
 // and is intentionally local-only — use CopyTo for Medium-agnostic transfers.
 // Example: _ = nodeTree.ExportFile("config/app.yaml", "backup/app.yaml", 0644)
-func (node *Node) ExportFile(sourcePath, destinationPath string, permissions fs.FileMode) error {
+func (node *Node) ExportFile(sourcePath, destinationPath string, permissions fs.FileMode) error { // legacy error contract
+
 	sourcePath = core.TrimPrefix(sourcePath, "/")
 	file, ok := node.files[sourcePath]
 	if !ok {
@@ -247,7 +268,8 @@ func (node *Node) ExportFile(sourcePath, destinationPath string, permissions fs.
 }
 
 // Example: _ = nodeTree.CopyTo(io.NewMemoryMedium(), "config", "backup/config")
-func (node *Node) CopyTo(target coreio.Medium, sourcePath, destinationPath string) error {
+func (node *Node) CopyTo(target coreio.Medium, sourcePath, destinationPath string) error { // legacy error contract
+
 	sourcePath = core.TrimPrefix(sourcePath, "/")
 	if sourcePath == "." {
 		sourcePath = ""
@@ -287,7 +309,10 @@ func (node *Node) CopyTo(target coreio.Medium, sourcePath, destinationPath strin
 }
 
 // Example: file, _ := nodeTree.Open("config/app.yaml")
-func (node *Node) Open(name string) (fs.File, error) {
+func (node *Node) Open(name string) (
+	fs.File,
+	error,
+) {
 	name = core.TrimPrefix(name, "/")
 	if name == "." {
 		name = ""
@@ -308,7 +333,10 @@ func (node *Node) Open(name string) (fs.File, error) {
 }
 
 // Example: info, _ := nodeTree.Stat("config/app.yaml")
-func (node *Node) Stat(name string) (fs.FileInfo, error) {
+func (node *Node) Stat(name string) (
+	fs.FileInfo,
+	error,
+) {
 	name = core.TrimPrefix(name, "/")
 	if name == "." {
 		name = ""
@@ -329,7 +357,10 @@ func (node *Node) Stat(name string) (fs.FileInfo, error) {
 }
 
 // Example: entries, _ := nodeTree.ReadDir("config")
-func (node *Node) ReadDir(name string) ([]fs.DirEntry, error) {
+func (node *Node) ReadDir(name string) (
+	[]fs.DirEntry,
+	error,
+) {
 	name = core.TrimPrefix(name, "/")
 	if name == "." {
 		name = ""
@@ -380,7 +411,10 @@ func (node *Node) ReadDir(name string) ([]fs.DirEntry, error) {
 }
 
 // Example: content, _ := nodeTree.Read("config/app.yaml")
-func (node *Node) Read(filePath string) (string, error) {
+func (node *Node) Read(filePath string) (
+	string,
+	error,
+) {
 	filePath = core.TrimPrefix(filePath, "/")
 	file, ok := node.files[filePath]
 	if !ok {
@@ -390,7 +424,8 @@ func (node *Node) Read(filePath string) (string, error) {
 }
 
 // Example: _ = nodeTree.Write("config/app.yaml", "port: 8080")
-func (node *Node) Write(filePath, content string) error {
+func (node *Node) Write(filePath, content string) error { // legacy error contract
+
 	filePath = core.TrimPrefix(filePath, "/")
 	if filePath == "" || filePath == "." {
 		return core.E("node.Write", "empty path", fs.ErrInvalid)
@@ -401,12 +436,14 @@ func (node *Node) Write(filePath, content string) error {
 
 // Example: _ = nodeTree.WriteMode("keys/private.key", key, 0600)
 // Note: mode is intentionally ignored — in-memory nodes have no filesystem permission model.
-func (node *Node) WriteMode(filePath, content string, mode fs.FileMode) error {
+func (node *Node) WriteMode(filePath, content string, mode fs.FileMode) error { // legacy error contract
+
 	return node.Write(filePath, content)
 }
 
 // Example: _ = nodeTree.EnsureDir("config")
-func (node *Node) EnsureDir(directoryPath string) error {
+func (node *Node) EnsureDir(directoryPath string) error { // legacy error contract
+
 	return nil
 }
 
@@ -433,7 +470,8 @@ func (node *Node) IsDir(filePath string) bool {
 }
 
 // Example: _ = nodeTree.Delete("config/app.yaml")
-func (node *Node) Delete(filePath string) error {
+func (node *Node) Delete(filePath string) error { // legacy error contract
+
 	filePath = core.TrimPrefix(filePath, "/")
 	if _, ok := node.files[filePath]; ok {
 		delete(node.files, filePath)
@@ -443,7 +481,8 @@ func (node *Node) Delete(filePath string) error {
 }
 
 // Example: _ = nodeTree.DeleteAll("logs/archive")
-func (node *Node) DeleteAll(filePath string) error {
+func (node *Node) DeleteAll(filePath string) error { // legacy error contract
+
 	filePath = core.TrimPrefix(filePath, "/")
 
 	found := false
@@ -468,7 +507,8 @@ func (node *Node) DeleteAll(filePath string) error {
 
 // Example: _ = nodeTree.Rename("drafts/todo.txt", "archive/todo.txt")
 // Example: _ = nodeTree.Rename("drafts", "archive")
-func (node *Node) Rename(oldPath, newPath string) error {
+func (node *Node) Rename(oldPath, newPath string) error { // legacy error contract
+
 	oldPath = core.TrimPrefix(oldPath, "/")
 	newPath = core.TrimPrefix(newPath, "/")
 
@@ -507,7 +547,10 @@ func (node *Node) Rename(oldPath, newPath string) error {
 }
 
 // Example: entries, _ := nodeTree.List("config")
-func (node *Node) List(filePath string) ([]fs.DirEntry, error) {
+func (node *Node) List(filePath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	filePath = core.TrimPrefix(filePath, "/")
 	if filePath == "" || filePath == "." {
 		return node.ReadDir(".")
@@ -516,13 +559,19 @@ func (node *Node) List(filePath string) ([]fs.DirEntry, error) {
 }
 
 // Example: writer, _ := nodeTree.Create("logs/app.log")
-func (node *Node) Create(filePath string) (goio.WriteCloser, error) {
+func (node *Node) Create(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	filePath = core.TrimPrefix(filePath, "/")
 	return &nodeWriter{node: node, path: filePath}, nil
 }
 
 // Example: writer, _ := nodeTree.Append("logs/app.log")
-func (node *Node) Append(filePath string) (goio.WriteCloser, error) {
+func (node *Node) Append(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	filePath = core.TrimPrefix(filePath, "/")
 	var existing []byte
 	if file, ok := node.files[filePath]; ok {
@@ -532,7 +581,10 @@ func (node *Node) Append(filePath string) (goio.WriteCloser, error) {
 	return &nodeWriter{node: node, path: filePath, buffer: existing}, nil
 }
 
-func (node *Node) ReadStream(filePath string) (goio.ReadCloser, error) {
+func (node *Node) ReadStream(filePath string) (
+	goio.ReadCloser,
+	error,
+) {
 	file, err := node.Open(filePath)
 	if err != nil {
 		return nil, err
@@ -540,7 +592,10 @@ func (node *Node) ReadStream(filePath string) (goio.ReadCloser, error) {
 	return file, nil
 }
 
-func (node *Node) WriteStream(filePath string) (goio.WriteCloser, error) {
+func (node *Node) WriteStream(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return node.Create(filePath)
 }
 
@@ -550,12 +605,16 @@ type nodeWriter struct {
 	buffer []byte
 }
 
-func (writer *nodeWriter) Write(data []byte) (int, error) {
+func (writer *nodeWriter) Write(data []byte) (
+	int,
+	error,
+) {
 	writer.buffer = append(writer.buffer, data...)
 	return len(data), nil
 }
 
-func (writer *nodeWriter) Close() error {
+func (writer *nodeWriter) Close() error { // legacy error contract
+
 	if writer.path == "" || writer.path == "." {
 		return core.E("node.nodeWriter.Close", "empty path", fs.ErrInvalid)
 	}
@@ -600,7 +659,10 @@ type dataFileReader struct {
 
 func (reader *dataFileReader) Stat() (fs.FileInfo, error) { return reader.file.Stat() }
 
-func (reader *dataFileReader) Read(buffer []byte) (int, error) {
+func (reader *dataFileReader) Read(buffer []byte) (
+	int,
+	error,
+) {
 	if reader.offset >= int64(len(reader.file.content)) {
 		return 0, goio.EOF
 	}
@@ -633,11 +695,17 @@ type dirFile struct {
 	modTime time.Time
 }
 
-func (directory *dirFile) Stat() (fs.FileInfo, error) {
+func (directory *dirFile) Stat() (
+	fs.FileInfo,
+	error,
+) {
 	return &dirInfo{name: core.PathBase(directory.path), modTime: directory.modTime}, nil
 }
 
-func (directory *dirFile) Read([]byte) (int, error) {
+func (directory *dirFile) Read([]byte) (
+	int,
+	error,
+) {
 	return 0, core.E("node.dirFile.Read", core.Concat("cannot read directory: ", directory.path), &fs.PathError{Op: "read", Path: directory.path, Err: fs.ErrInvalid})
 }
 
diff --git a/node/node_example_test.go b/go/node/node_example_test.go
similarity index 100%
rename from node/node_example_test.go
rename to go/node/node_example_test.go
diff --git a/node/node_test.go b/go/node/node_test.go
similarity index 100%
rename from node/node_test.go
rename to go/node/node_test.go
diff --git a/pkg/api/handlers.go b/go/pkg/api/handlers.go
similarity index 94%
rename from pkg/api/handlers.go
rename to go/pkg/api/handlers.go
index aca3e69..fea7296 100644
--- a/pkg/api/handlers.go
+++ b/go/pkg/api/handlers.go
@@ -347,7 +347,10 @@ var mediumOperationHandlers = map[string]mediumOperationHandler{
 	"isdir":       isDirMediumOperation,
 }
 
-func dispatchMediumOperation(ctx context.Context, medium coreio.Medium, op string, req mediumRequest) (mediumResponse, error) {
+func dispatchMediumOperation(ctx context.Context, medium coreio.Medium, op string, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	handler, ok := mediumOperationHandlers[core.Lower(op)]
 	if !ok {
 		return mediumResponse{}, core.Errorf("%w: %s", errUnsupportedMediumOperation, op)
@@ -355,7 +358,10 @@ func dispatchMediumOperation(ctx context.Context, medium coreio.Medium, op strin
 	return handler(ctx, medium, req)
 }
 
-func readMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func readMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	content, err := medium.Read(req.Path)
 	if err != nil {
 		return mediumResponse{}, err
@@ -363,14 +369,20 @@ func readMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequ
 	return mediumResponse{OK: true, Content: content}, nil
 }
 
-func writeMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func writeMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	if err := medium.Write(req.Path, req.Content); err != nil {
 		return mediumResponse{}, err
 	}
 	return mediumResponse{OK: true}, nil
 }
 
-func writeModeMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func writeModeMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	mode, err := fileModeValue(req.Mode, 0644)
 	if err != nil {
 		return mediumResponse{}, err
@@ -381,19 +393,28 @@ func writeModeMediumOperation(_ context.Context, medium coreio.Medium, req mediu
 	return mediumResponse{OK: true}, nil
 }
 
-func ensureDirMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func ensureDirMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	if err := medium.EnsureDir(req.Path); err != nil {
 		return mediumResponse{}, err
 	}
 	return mediumResponse{OK: true}, nil
 }
 
-func isFileMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func isFileMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	ok := medium.IsFile(req.Path)
 	return mediumResponse{OK: true, IsFile: &ok}, nil
 }
 
-func deleteMediumOperation(ctx context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func deleteMediumOperation(ctx context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	if req.Recursive {
 		return deleteAllMediumOperation(ctx, medium, req)
 	}
@@ -403,21 +424,30 @@ func deleteMediumOperation(ctx context.Context, medium coreio.Medium, req medium
 	return mediumResponse{OK: true}, nil
 }
 
-func deleteAllMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func deleteAllMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	if err := medium.DeleteAll(req.Path); err != nil {
 		return mediumResponse{}, err
 	}
 	return mediumResponse{OK: true}, nil
 }
 
-func renameMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func renameMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	if err := medium.Rename(req.OldPath, req.NewPath); err != nil {
 		return mediumResponse{}, err
 	}
 	return mediumResponse{OK: true}, nil
 }
 
-func listMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func listMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	entries, err := medium.List(req.Path)
 	if err != nil {
 		return mediumResponse{}, err
@@ -425,7 +455,10 @@ func listMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequ
 	return mediumResponse{OK: true, Entries: dirEntryDTOs(entries)}, nil
 }
 
-func statMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func statMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	info, err := medium.Stat(req.Path)
 	if err != nil {
 		return mediumResponse{}, err
@@ -433,7 +466,10 @@ func statMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequ
 	return mediumResponse{OK: true, Info: fileInfoDTOFromInfo(info)}, nil
 }
 
-func openMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func openMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	file, err := medium.Open(req.Path)
 	if err != nil {
 		return mediumResponse{}, err
@@ -442,7 +478,10 @@ func openMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequ
 	return readAllContent(file)
 }
 
-func createMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func createMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	writer, err := medium.Create(req.Path)
 	if err != nil {
 		return mediumResponse{}, err
@@ -453,7 +492,10 @@ func createMediumOperation(_ context.Context, medium coreio.Medium, req mediumRe
 	return mediumResponse{OK: true}, nil
 }
 
-func appendMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func appendMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	writer, err := medium.Append(req.Path)
 	if err != nil {
 		return mediumResponse{}, err
@@ -464,7 +506,10 @@ func appendMediumOperation(_ context.Context, medium coreio.Medium, req mediumRe
 	return mediumResponse{OK: true}, nil
 }
 
-func readStreamMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func readStreamMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	reader, err := medium.ReadStream(req.Path)
 	if err != nil {
 		return mediumResponse{}, err
@@ -473,7 +518,10 @@ func readStreamMediumOperation(_ context.Context, medium coreio.Medium, req medi
 	return readAllContent(reader)
 }
 
-func writeStreamMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func writeStreamMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	writer, err := medium.WriteStream(req.Path)
 	if err != nil {
 		return mediumResponse{}, err
@@ -484,17 +532,26 @@ func writeStreamMediumOperation(_ context.Context, medium coreio.Medium, req med
 	return mediumResponse{OK: true}, nil
 }
 
-func existsMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func existsMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	ok := medium.Exists(req.Path)
 	return mediumResponse{OK: true, Exists: &ok}, nil
 }
 
-func isDirMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (mediumResponse, error) {
+func isDirMediumOperation(_ context.Context, medium coreio.Medium, req mediumRequest) (
+	mediumResponse,
+	error,
+) {
 	ok := medium.IsDir(req.Path)
 	return mediumResponse{OK: true, IsDir: &ok}, nil
 }
 
-func readAllContent(reader goio.Reader) (mediumResponse, error) {
+func readAllContent(reader goio.Reader) (
+	mediumResponse,
+	error,
+) {
 	content, err := goio.ReadAll(reader)
 	if err != nil {
 		return mediumResponse{}, err
@@ -612,7 +669,10 @@ func normalizedValue(value any) any {
 	}
 }
 
-func fileModeValue(value any, fallback fs.FileMode) (fs.FileMode, error) {
+func fileModeValue(value any, fallback fs.FileMode) (
+	fs.FileMode,
+	error,
+) {
 	if value == nil {
 		return fallback, nil
 	}
@@ -666,7 +726,8 @@ func fileInfoDTOFromInfo(info fs.FileInfo) *fileInfoDTO {
 	}
 }
 
-func writeAndClose(writer goio.WriteCloser, content string) error {
+func writeAndClose(writer goio.WriteCloser, content string) error { // legacy error contract
+
 	if _, err := goio.WriteString(writer, content); err != nil {
 		if closeErr := writer.Close(); closeErr != nil {
 			return core.ErrorJoin(err, closeErr)
diff --git a/pkg/api/handlers_test.go b/go/pkg/api/handlers_test.go
similarity index 100%
rename from pkg/api/handlers_test.go
rename to go/pkg/api/handlers_test.go
diff --git a/pkg/api/provider.go b/go/pkg/api/provider.go
similarity index 100%
rename from pkg/api/provider.go
rename to go/pkg/api/provider.go
diff --git a/pkg/api/provider_example_test.go b/go/pkg/api/provider_example_test.go
similarity index 100%
rename from pkg/api/provider_example_test.go
rename to go/pkg/api/provider_example_test.go
diff --git a/pkg/api/provider_test.go b/go/pkg/api/provider_test.go
similarity index 100%
rename from pkg/api/provider_test.go
rename to go/pkg/api/provider_test.go
diff --git a/pkg/medium/github/github.go b/go/pkg/medium/github/github.go
similarity index 86%
rename from pkg/medium/github/github.go
rename to go/pkg/medium/github/github.go
index b4422b6..383b973 100644
--- a/pkg/medium/github/github.go
+++ b/go/pkg/medium/github/github.go
@@ -56,7 +56,10 @@ type Options struct {
 }
 
 // New creates a GitHub Medium.
-func New(options Options) (*Medium, error) {
+func New(options Options) (
+	*Medium,
+	error,
+) {
 	owner := core.Trim(options.Owner)
 	if owner == "" {
 		return nil, core.E(opNew, "owner is required", fs.ErrInvalid)
@@ -124,7 +127,11 @@ func tokenFromEnvironment(tokenFile string) string {
 	return core.Trim(data)
 }
 
-func tokenFileMedium(tokenFile string) (coreio.Medium, string, error) {
+func tokenFileMedium(tokenFile string) (
+	coreio.Medium,
+	string,
+	error,
+) {
 	if core.PathIsAbs(tokenFile) {
 		root := core.PathDir(tokenFile)
 		relativePath := core.PathBase(tokenFile)
@@ -164,7 +171,8 @@ func oauthClient(client *http.Client, token string) *http.Client {
 	return &clone
 }
 
-func setClientBaseURL(client *gh.Client, baseURL string) error {
+func setClientBaseURL(client *gh.Client, baseURL string) error { // legacy error contract
+
 	parsed, err := url.Parse(baseURL)
 	if err != nil {
 		return err
@@ -187,7 +195,10 @@ func cleanRelative(filePath string) string {
 	return core.TrimPrefix(clean, "/")
 }
 
-func requiredPath(operation, filePath string) (string, error) {
+func requiredPath(operation, filePath string) (
+	string,
+	error,
+) {
 	clean := cleanRelative(filePath)
 	if clean == "" {
 		return "", core.E(operation, "path is required", fs.ErrInvalid)
@@ -202,7 +213,11 @@ func (medium *Medium) contentOptions() *gh.RepositoryContentGetOptions {
 	return &gh.RepositoryContentGetOptions{Ref: medium.ref}
 }
 
-func (medium *Medium) getContents(operation, filePath string) (*gh.RepositoryContent, []*gh.RepositoryContent, error) {
+func (medium *Medium) getContents(operation, filePath string) (
+	*gh.RepositoryContent,
+	[]*gh.RepositoryContent,
+	error,
+) {
 	fileContent, directoryContent, _, err := medium.client.Repositories.GetContents(
 		context.Background(),
 		medium.owner,
@@ -216,7 +231,8 @@ func (medium *Medium) getContents(operation, filePath string) (*gh.RepositoryCon
 	return fileContent, directoryContent, nil
 }
 
-func wrapGitHubError(operation, filePath string, err error) error {
+func wrapGitHubError(operation, filePath string, err error) error { // legacy error contract
+
 	if err == nil {
 		return nil
 	}
@@ -238,7 +254,8 @@ func wrapGitHubError(operation, filePath string, err error) error {
 	return core.E(operation, core.Concat("GitHub contents request failed: ", filePath), err)
 }
 
-func readOnly(operation string) error {
+func readOnly(operation string) error { // legacy error contract
+
 	return core.E(operation, "GitHub medium is read-only", ErrReadOnly)
 }
 
@@ -260,7 +277,10 @@ func dirInfoForPath(filePath string) coreio.FileInfo {
 }
 
 // Read reads a repository file into a string.
-func (medium *Medium) Read(filePath string) (string, error) {
+func (medium *Medium) Read(filePath string) (
+	string,
+	error,
+) {
 	clean, err := requiredPath(opRead, filePath)
 	if err != nil {
 		return "", err
@@ -283,17 +303,20 @@ func (medium *Medium) Read(filePath string) (string, error) {
 }
 
 // Write returns ErrReadOnly because GitHub Medium is read-only.
-func (medium *Medium) Write(filePath, content string) error {
+func (medium *Medium) Write(filePath, content string) error { // legacy error contract
+
 	return readOnly("github.Write")
 }
 
 // WriteMode returns ErrReadOnly because GitHub Medium is read-only.
-func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error { // legacy error contract
+
 	return readOnly("github.WriteMode")
 }
 
 // EnsureDir returns ErrReadOnly because GitHub Medium is read-only.
-func (medium *Medium) EnsureDir(filePath string) error {
+func (medium *Medium) EnsureDir(filePath string) error { // legacy error contract
+
 	return readOnly("github.EnsureDir")
 }
 
@@ -308,22 +331,28 @@ func (medium *Medium) IsFile(filePath string) bool {
 }
 
 // Delete returns ErrReadOnly because GitHub Medium is read-only.
-func (medium *Medium) Delete(filePath string) error {
+func (medium *Medium) Delete(filePath string) error { // legacy error contract
+
 	return readOnly("github.Delete")
 }
 
 // DeleteAll returns ErrReadOnly because GitHub Medium is read-only.
-func (medium *Medium) DeleteAll(filePath string) error {
+func (medium *Medium) DeleteAll(filePath string) error { // legacy error contract
+
 	return readOnly("github.DeleteAll")
 }
 
 // Rename returns ErrReadOnly because GitHub Medium is read-only.
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	return readOnly("github.Rename")
 }
 
 // List returns a recursive listing under a repository directory.
-func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(filePath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	clean := cleanRelative(filePath)
 	entries, err := medium.listRecursive(clean)
 	if err != nil {
@@ -335,7 +364,10 @@ func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
 	return entries, nil
 }
 
-func (medium *Medium) listRecursive(filePath string) ([]fs.DirEntry, error) {
+func (medium *Medium) listRecursive(filePath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	fileContent, directoryContent, err := medium.getContents(opList, filePath)
 	if err != nil {
 		return nil, err
@@ -370,7 +402,10 @@ func (medium *Medium) listRecursive(filePath string) ([]fs.DirEntry, error) {
 }
 
 // Stat returns metadata for a repository path.
-func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(filePath string) (
+	fs.FileInfo,
+	error,
+) {
 	clean, err := requiredPath(opStat, filePath)
 	if err != nil {
 		return nil, err
@@ -389,7 +424,10 @@ func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
 }
 
 // Open opens a repository file for reading.
-func (medium *Medium) Open(filePath string) (fs.File, error) {
+func (medium *Medium) Open(filePath string) (
+	fs.File,
+	error,
+) {
 	content, err := medium.Read(filePath)
 	if err != nil {
 		return nil, err
@@ -407,17 +445,26 @@ func (medium *Medium) Open(filePath string) (fs.File, error) {
 }
 
 // Create returns ErrReadOnly because GitHub Medium is read-only.
-func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return nil, readOnly("github.Create")
 }
 
 // Append returns ErrReadOnly because GitHub Medium is read-only.
-func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return nil, readOnly("github.Append")
 }
 
 // ReadStream opens a repository file as an io.ReadCloser.
-func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(filePath string) (
+	goio.ReadCloser,
+	error,
+) {
 	content, err := medium.Read(filePath)
 	if err != nil {
 		return nil, err
@@ -426,7 +473,10 @@ func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
 }
 
 // WriteStream returns ErrReadOnly because GitHub Medium is read-only.
-func (medium *Medium) WriteStream(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return nil, readOnly("github.WriteStream")
 }
 
@@ -453,14 +503,20 @@ func (medium *Medium) IsDir(filePath string) bool {
 // Clone returns all file contents under filePath, keyed by repository path.
 // Default full-repo clones use Borg's Git cloner and DataNode substrate; custom
 // GitHub API URLs and explicit refs keep the REST contents path for compatibility.
-func (medium *Medium) Clone(filePath string) (map[string]string, error) {
+func (medium *Medium) Clone(filePath string) (
+	map[string]string,
+	error,
+) {
 	if medium.baseURL == "" && medium.ref == "" {
 		return medium.cloneWithBorg(filePath)
 	}
 	return medium.cloneWithContentsAPI(filePath)
 }
 
-func (medium *Medium) cloneWithBorg(filePath string) (map[string]string, error) {
+func (medium *Medium) cloneWithBorg(filePath string) (
+	map[string]string,
+	error,
+) {
 	dataNode, err := borgvcs.NewGitCloner().CloneGitRepository(medium.borgCloneURL(), nil)
 	if err != nil {
 		return nil, core.E(opClone, "Borg clone failed", err)
@@ -476,7 +532,10 @@ func (medium *Medium) borgCloneURL() string {
 	return core.Sprintf("https://github.com/%s/%s.git", medium.owner, medium.repo)
 }
 
-func collectBorgDataNodeContents(dataNode *borgdatanode.DataNode, clean string) (map[string]string, error) {
+func collectBorgDataNodeContents(dataNode *borgdatanode.DataNode, clean string) (
+	map[string]string,
+	error,
+) {
 	if dataNode == nil {
 		return nil, fs.ErrInvalid
 	}
@@ -501,7 +560,8 @@ func collectBorgDataNodeContents(dataNode *borgdatanode.DataNode, clean string)
 	return contents, nil
 }
 
-func collectBorgDataNodeDir(dataNode *borgdatanode.DataNode, dirPath string, contents map[string]string) error {
+func collectBorgDataNodeDir(dataNode *borgdatanode.DataNode, dirPath string, contents map[string]string) error { // legacy error contract
+
 	entries, err := dataNode.ReadDir(dirPath)
 	if err != nil {
 		return err
@@ -526,7 +586,10 @@ func collectBorgDataNodeDir(dataNode *borgdatanode.DataNode, dirPath string, con
 	return nil
 }
 
-func readBorgDataNodeFile(dataNode *borgdatanode.DataNode, filePath string) (string, error) {
+func readBorgDataNodeFile(dataNode *borgdatanode.DataNode, filePath string) (
+	string,
+	error,
+) {
 	file, err := dataNode.Open(filePath)
 	if err != nil {
 		return "", err
@@ -545,7 +608,10 @@ func closeGitHubDataNodeFile(file fs.File, filePath string) {
 	}
 }
 
-func (medium *Medium) cloneWithContentsAPI(filePath string) (map[string]string, error) {
+func (medium *Medium) cloneWithContentsAPI(filePath string) (
+	map[string]string,
+	error,
+) {
 	clean := cleanRelative(filePath)
 	if clean != "" {
 		info, err := medium.Stat(clean)
@@ -590,11 +656,17 @@ type githubFile struct {
 
 var _ fs.File = (*githubFile)(nil)
 
-func (file *githubFile) Stat() (fs.FileInfo, error) {
+func (file *githubFile) Stat() (
+	fs.FileInfo,
+	error,
+) {
 	return coreio.NewFileInfo(file.name, int64(len(file.content)), file.mode, file.modTime, false), nil
 }
 
-func (file *githubFile) Read(data []byte) (int, error) {
+func (file *githubFile) Read(data []byte) (
+	int,
+	error,
+) {
 	if file.closed {
 		return 0, fs.ErrClosed
 	}
@@ -607,7 +679,8 @@ func (file *githubFile) Read(data []byte) (int, error) {
 	return n, err
 }
 
-func (file *githubFile) Close() error {
+func (file *githubFile) Close() error { // legacy error contract
+
 	file.closed = true
 	return nil
 }
diff --git a/pkg/medium/github/github_example_test.go b/go/pkg/medium/github/github_example_test.go
similarity index 100%
rename from pkg/medium/github/github_example_test.go
rename to go/pkg/medium/github/github_example_test.go
diff --git a/pkg/medium/github/github_test.go b/go/pkg/medium/github/github_test.go
similarity index 100%
rename from pkg/medium/github/github_test.go
rename to go/pkg/medium/github/github_test.go
diff --git a/pkg/medium/github/register.go b/go/pkg/medium/github/register.go
similarity index 97%
rename from pkg/medium/github/register.go
rename to go/pkg/medium/github/register.go
index c6dc8a9..36258fe 100644
--- a/pkg/medium/github/register.go
+++ b/go/pkg/medium/github/register.go
@@ -46,7 +46,10 @@ func RegisterActions(c *core.Core) {
 	c.Action(ActionClone, cloneAction)
 }
 
-func mediumFromOptions(opts core.Options) (*Medium, error) {
+func mediumFromOptions(opts core.Options) (
+	*Medium,
+	error,
+) {
 	if medium, ok := opts.Get("medium").Value.(*Medium); ok {
 		return medium, nil
 	}
diff --git a/pkg/medium/github/register_example_test.go b/go/pkg/medium/github/register_example_test.go
similarity index 100%
rename from pkg/medium/github/register_example_test.go
rename to go/pkg/medium/github/register_example_test.go
diff --git a/pkg/medium/github/register_test.go b/go/pkg/medium/github/register_test.go
similarity index 100%
rename from pkg/medium/github/register_test.go
rename to go/pkg/medium/github/register_test.go
diff --git a/pkg/medium/pwa/pwa.go b/go/pkg/medium/pwa/pwa.go
similarity index 82%
rename from pkg/medium/pwa/pwa.go
rename to go/pkg/medium/pwa/pwa.go
index d8405e8..5a263c5 100644
--- a/pkg/medium/pwa/pwa.go
+++ b/go/pkg/medium/pwa/pwa.go
@@ -41,7 +41,10 @@ type Options struct {
 }
 
 // New creates a PWA Medium that lazily downloads the target into a Borg DataNode.
-func New(options Options) (*Medium, error) {
+func New(options Options) (
+	*Medium,
+	error,
+) {
 	return &Medium{url: options.URL}, nil
 }
 
@@ -53,7 +56,10 @@ func cleanRelative(filePath string) string {
 	return core.TrimPrefix(clean, "/")
 }
 
-func requiredPath(operation, filePath string) (string, error) {
+func requiredPath(operation, filePath string) (
+	string,
+	error,
+) {
 	clean := cleanRelative(filePath)
 	if clean == "" {
 		return "", core.E(operation, "path is required", fs.ErrInvalid)
@@ -61,7 +67,10 @@ func requiredPath(operation, filePath string) (string, error) {
 	return clean, nil
 }
 
-func (medium *Medium) ensureDataNode() (*borgdatanode.DataNode, error) {
+func (medium *Medium) ensureDataNode() (
+	*borgdatanode.DataNode,
+	error,
+) {
 	medium.mu.RLock()
 	dataNode := medium.dataNode
 	medium.mu.RUnlock()
@@ -93,12 +102,16 @@ func (medium *Medium) ensureDataNode() (*borgdatanode.DataNode, error) {
 	return dataNode, nil
 }
 
-func readOnly(operation string) error {
+func readOnly(operation string) error { // legacy error contract
+
 	return core.E(operation, "PWA medium is read-only", errReadOnly)
 }
 
 // Read reads a downloaded PWA asset from Borg's DataNode.
-func (medium *Medium) Read(filePath string) (string, error) {
+func (medium *Medium) Read(filePath string) (
+	string,
+	error,
+) {
 	clean, err := requiredPath(opRead, filePath)
 	if err != nil {
 		return "", err
@@ -127,17 +140,20 @@ func (medium *Medium) Read(filePath string) (string, error) {
 }
 
 // Write returns an error because downloaded PWA DataNodes are read-only.
-func (medium *Medium) Write(filePath, content string) error {
+func (medium *Medium) Write(filePath, content string) error { // legacy error contract
+
 	return readOnly("pwa.Write")
 }
 
 // WriteMode returns an error because downloaded PWA DataNodes are read-only.
-func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error { // legacy error contract
+
 	return readOnly("pwa.WriteMode")
 }
 
 // EnsureDir returns an error because downloaded PWA DataNodes are read-only.
-func (medium *Medium) EnsureDir(filePath string) error {
+func (medium *Medium) EnsureDir(filePath string) error { // legacy error contract
+
 	return readOnly("pwa.EnsureDir")
 }
 
@@ -152,22 +168,28 @@ func (medium *Medium) IsFile(filePath string) bool {
 }
 
 // Delete returns an error because downloaded PWA DataNodes are read-only.
-func (medium *Medium) Delete(filePath string) error {
+func (medium *Medium) Delete(filePath string) error { // legacy error contract
+
 	return readOnly("pwa.Delete")
 }
 
 // DeleteAll returns an error because downloaded PWA DataNodes are read-only.
-func (medium *Medium) DeleteAll(filePath string) error {
+func (medium *Medium) DeleteAll(filePath string) error { // legacy error contract
+
 	return readOnly("pwa.DeleteAll")
 }
 
 // Rename returns an error because downloaded PWA DataNodes are read-only.
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	return readOnly("pwa.Rename")
 }
 
 // List lists downloaded PWA assets from Borg's DataNode.
-func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(filePath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	dataNode, err := medium.ensureDataNode()
 	if err != nil {
 		return nil, err
@@ -181,7 +203,10 @@ func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
 }
 
 // Stat returns metadata for a downloaded PWA asset.
-func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(filePath string) (
+	fs.FileInfo,
+	error,
+) {
 	dataNode, err := medium.ensureDataNode()
 	if err != nil {
 		return nil, err
@@ -195,7 +220,10 @@ func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
 }
 
 // Open opens a downloaded PWA asset from Borg's DataNode.
-func (medium *Medium) Open(filePath string) (fs.File, error) {
+func (medium *Medium) Open(filePath string) (
+	fs.File,
+	error,
+) {
 	clean, err := requiredPath(opOpen, filePath)
 	if err != nil {
 		return nil, err
@@ -227,17 +255,26 @@ func closePWAFile(file fs.File, filePath string) {
 }
 
 // Create returns an error because downloaded PWA DataNodes are read-only.
-func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return nil, readOnly("pwa.Create")
 }
 
 // Append returns an error because downloaded PWA DataNodes are read-only.
-func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return nil, readOnly("pwa.Append")
 }
 
 // ReadStream opens a downloaded PWA asset as a stream.
-func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(filePath string) (
+	goio.ReadCloser,
+	error,
+) {
 	file, err := medium.Open(filePath)
 	if err != nil {
 		return nil, err
@@ -246,7 +283,10 @@ func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
 }
 
 // WriteStream returns an error because downloaded PWA DataNodes are read-only.
-func (medium *Medium) WriteStream(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return nil, readOnly("pwa.WriteStream")
 }
 
diff --git a/pkg/medium/pwa/pwa_example_test.go b/go/pkg/medium/pwa/pwa_example_test.go
similarity index 100%
rename from pkg/medium/pwa/pwa_example_test.go
rename to go/pkg/medium/pwa/pwa_example_test.go
diff --git a/pkg/medium/pwa/pwa_test.go b/go/pkg/medium/pwa/pwa_test.go
similarity index 100%
rename from pkg/medium/pwa/pwa_test.go
rename to go/pkg/medium/pwa/pwa_test.go
diff --git a/pkg/medium/pwa/register.go b/go/pkg/medium/pwa/register.go
similarity index 97%
rename from pkg/medium/pwa/register.go
rename to go/pkg/medium/pwa/register.go
index 885655a..f5a1856 100644
--- a/pkg/medium/pwa/register.go
+++ b/go/pkg/medium/pwa/register.go
@@ -48,7 +48,10 @@ func RegisterActions(c *core.Core) {
 	c.Action(ActionWrite, writeAction)
 }
 
-func mediumFromOptions(opts core.Options) (*Medium, error) {
+func mediumFromOptions(opts core.Options) (
+	*Medium,
+	error,
+) {
 	if medium, ok := opts.Get("medium").Value.(*Medium); ok {
 		return medium, nil
 	}
diff --git a/pkg/medium/pwa/register_example_test.go b/go/pkg/medium/pwa/register_example_test.go
similarity index 100%
rename from pkg/medium/pwa/register_example_test.go
rename to go/pkg/medium/pwa/register_example_test.go
diff --git a/pkg/medium/pwa/register_test.go b/go/pkg/medium/pwa/register_test.go
similarity index 100%
rename from pkg/medium/pwa/register_test.go
rename to go/pkg/medium/pwa/register_test.go
diff --git a/pkg/medium/sftp/register.go b/go/pkg/medium/sftp/register.go
similarity index 100%
rename from pkg/medium/sftp/register.go
rename to go/pkg/medium/sftp/register.go
diff --git a/pkg/medium/sftp/register_example_test.go b/go/pkg/medium/sftp/register_example_test.go
similarity index 100%
rename from pkg/medium/sftp/register_example_test.go
rename to go/pkg/medium/sftp/register_example_test.go
diff --git a/pkg/medium/sftp/register_test.go b/go/pkg/medium/sftp/register_test.go
similarity index 100%
rename from pkg/medium/sftp/register_test.go
rename to go/pkg/medium/sftp/register_test.go
diff --git a/pkg/medium/sftp/sftp.go b/go/pkg/medium/sftp/sftp.go
similarity index 88%
rename from pkg/medium/sftp/sftp.go
rename to go/pkg/medium/sftp/sftp.go
index 0b0ed49..f8b4b2e 100644
--- a/pkg/medium/sftp/sftp.go
+++ b/go/pkg/medium/sftp/sftp.go
@@ -54,7 +54,10 @@ type Options struct {
 
 // New creates an SFTP Medium. Tests and callers that already manage transport
 // state can inject Client directly; otherwise New dials Address using SSH.
-func New(options Options) (*Medium, error) {
+func New(options Options) (
+	*Medium,
+	error,
+) {
 	root := normaliseRoot(options.Root)
 	if options.Client != nil {
 		return &Medium{client: options.Client, root: root}, nil
@@ -96,7 +99,10 @@ func New(options Options) (*Medium, error) {
 	}, nil
 }
 
-func sshConfig(options Options) (*ssh.ClientConfig, error) {
+func sshConfig(options Options) (
+	*ssh.ClientConfig,
+	error,
+) {
 	if options.Config != nil {
 		return options.Config, nil
 	}
@@ -156,7 +162,10 @@ func (medium *Medium) remotePath(filePath string) string {
 	return core.PathJoin(medium.root, relative)
 }
 
-func (medium *Medium) requiredRemotePath(operation, filePath string) (string, error) {
+func (medium *Medium) requiredRemotePath(operation, filePath string) (
+	string,
+	error,
+) {
 	if cleanRelative(filePath) == "" {
 		return "", core.E(operation, "path is required", fs.ErrInvalid)
 	}
@@ -169,7 +178,8 @@ func closeSFTPCloser(closer goio.Closer, operation, target string) {
 	}
 }
 
-func (medium *Medium) ensureParent(remotePath string) error {
+func (medium *Medium) ensureParent(remotePath string) error { // legacy error contract
+
 	parent := core.PathDir(remotePath)
 	if parent == "." || parent == "/" {
 		return nil
@@ -178,7 +188,8 @@ func (medium *Medium) ensureParent(remotePath string) error {
 }
 
 // Close closes clients created by New. Injected clients remain caller-owned.
-func (medium *Medium) Close() error {
+func (medium *Medium) Close() error { // legacy error contract
+
 	var err error
 	if medium.ownsClient && medium.client != nil {
 		err = medium.client.Close()
@@ -192,7 +203,10 @@ func (medium *Medium) Close() error {
 }
 
 // Read reads a remote file into a string.
-func (medium *Medium) Read(filePath string) (string, error) {
+func (medium *Medium) Read(filePath string) (
+	string,
+	error,
+) {
 	remotePath, err := medium.requiredRemotePath(opRead, filePath)
 	if err != nil {
 		return "", err
@@ -211,13 +225,15 @@ func (medium *Medium) Read(filePath string) (string, error) {
 }
 
 // Write writes a remote file using the default file mode.
-func (medium *Medium) Write(filePath, content string) error {
+func (medium *Medium) Write(filePath, content string) error { // legacy error contract
+
 	return medium.WriteMode(filePath, content, 0644)
 }
 
 // WriteMode writes a remote file and applies POSIX permissions when supported
 // by the SFTP server.
-func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error { // legacy error contract
+
 	remotePath, err := medium.requiredRemotePath(opWriteMode, filePath)
 	if err != nil {
 		return err
@@ -246,7 +262,8 @@ func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) erro
 }
 
 // EnsureDir creates a remote directory and any missing parents.
-func (medium *Medium) EnsureDir(filePath string) error {
+func (medium *Medium) EnsureDir(filePath string) error { // legacy error contract
+
 	remotePath := medium.remotePath(filePath)
 	if remotePath == medium.root {
 		return nil
@@ -267,7 +284,8 @@ func (medium *Medium) IsFile(filePath string) bool {
 }
 
 // Delete removes a remote file or empty directory.
-func (medium *Medium) Delete(filePath string) error {
+func (medium *Medium) Delete(filePath string) error { // legacy error contract
+
 	remotePath, err := medium.requiredRemotePath("sftp.Delete", filePath)
 	if err != nil {
 		return err
@@ -279,7 +297,8 @@ func (medium *Medium) Delete(filePath string) error {
 }
 
 // DeleteAll removes a remote file or directory tree.
-func (medium *Medium) DeleteAll(filePath string) error {
+func (medium *Medium) DeleteAll(filePath string) error { // legacy error contract
+
 	remotePath, err := medium.requiredRemotePath("sftp.DeleteAll", filePath)
 	if err != nil {
 		return err
@@ -291,7 +310,8 @@ func (medium *Medium) DeleteAll(filePath string) error {
 }
 
 // Rename renames a remote path.
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	oldRemotePath, err := medium.requiredRemotePath(opRename, oldPath)
 	if err != nil {
 		return err
@@ -310,7 +330,10 @@ func (medium *Medium) Rename(oldPath, newPath string) error {
 }
 
 // List returns the immediate children under a remote directory.
-func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(filePath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	remotePath := medium.remotePath(filePath)
 	infos, err := medium.client.ReadDir(remotePath)
 	if err != nil {
@@ -328,7 +351,10 @@ func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
 }
 
 // Stat returns metadata for a remote path.
-func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(filePath string) (
+	fs.FileInfo,
+	error,
+) {
 	remotePath, err := medium.requiredRemotePath("sftp.Stat", filePath)
 	if err != nil {
 		return nil, err
@@ -341,7 +367,10 @@ func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
 }
 
 // Open opens a remote file for reading.
-func (medium *Medium) Open(filePath string) (fs.File, error) {
+func (medium *Medium) Open(filePath string) (
+	fs.File,
+	error,
+) {
 	remotePath, err := medium.requiredRemotePath(opOpen, filePath)
 	if err != nil {
 		return nil, err
@@ -354,7 +383,10 @@ func (medium *Medium) Open(filePath string) (fs.File, error) {
 }
 
 // Create opens a remote file for replacement.
-func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	remotePath, err := medium.requiredRemotePath(opCreate, filePath)
 	if err != nil {
 		return nil, err
@@ -370,7 +402,10 @@ func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
 }
 
 // Append opens a remote file for appending, creating it when missing.
-func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	remotePath, err := medium.requiredRemotePath(opAppend, filePath)
 	if err != nil {
 		return nil, err
@@ -386,7 +421,10 @@ func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
 }
 
 // ReadStream opens a remote file as an io.ReadCloser.
-func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(filePath string) (
+	goio.ReadCloser,
+	error,
+) {
 	file, err := medium.Open(filePath)
 	if err != nil {
 		return nil, err
@@ -395,7 +433,10 @@ func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
 }
 
 // WriteStream opens a remote file as an io.WriteCloser.
-func (medium *Medium) WriteStream(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.Create(filePath)
 }
 
diff --git a/pkg/medium/sftp/sftp_example_test.go b/go/pkg/medium/sftp/sftp_example_test.go
similarity index 100%
rename from pkg/medium/sftp/sftp_example_test.go
rename to go/pkg/medium/sftp/sftp_example_test.go
diff --git a/pkg/medium/sftp/sftp_test.go b/go/pkg/medium/sftp/sftp_test.go
similarity index 100%
rename from pkg/medium/sftp/sftp_test.go
rename to go/pkg/medium/sftp/sftp_test.go
diff --git a/pkg/medium/webdav/register.go b/go/pkg/medium/webdav/register.go
similarity index 100%
rename from pkg/medium/webdav/register.go
rename to go/pkg/medium/webdav/register.go
diff --git a/pkg/medium/webdav/register_example_test.go b/go/pkg/medium/webdav/register_example_test.go
similarity index 100%
rename from pkg/medium/webdav/register_example_test.go
rename to go/pkg/medium/webdav/register_example_test.go
diff --git a/pkg/medium/webdav/register_test.go b/go/pkg/medium/webdav/register_test.go
similarity index 100%
rename from pkg/medium/webdav/register_test.go
rename to go/pkg/medium/webdav/register_test.go
diff --git a/pkg/medium/webdav/webdav.go b/go/pkg/medium/webdav/webdav.go
similarity index 89%
rename from pkg/medium/webdav/webdav.go
rename to go/pkg/medium/webdav/webdav.go
index 9f85b88..d448f61 100644
--- a/pkg/medium/webdav/webdav.go
+++ b/go/pkg/medium/webdav/webdav.go
@@ -61,7 +61,10 @@ type Options struct {
 }
 
 // New creates a WebDAV Medium.
-func New(options Options) (*Medium, error) {
+func New(options Options) (
+	*Medium,
+	error,
+) {
 	if options.BaseURL == "" {
 		return nil, core.E(opNew, "base URL is required", fs.ErrInvalid)
 	}
@@ -117,14 +120,20 @@ func (medium *Medium) resourceURL(filePath string) string {
 	return u.String()
 }
 
-func (medium *Medium) requiredResourceURL(operation, filePath string) (string, error) {
+func (medium *Medium) requiredResourceURL(operation, filePath string) (
+	string,
+	error,
+) {
 	if cleanRelative(filePath) == "" {
 		return "", core.E(operation, "path is required", fs.ErrInvalid)
 	}
 	return medium.resourceURL(filePath), nil
 }
 
-func (medium *Medium) newRequest(method, filePath string, body goio.Reader) (*http.Request, error) {
+func (medium *Medium) newRequest(method, filePath string, body goio.Reader) (
+	*http.Request,
+	error,
+) {
 	request, err := http.NewRequest(method, medium.resourceURL(filePath), body)
 	if err != nil {
 		return nil, err
@@ -140,7 +149,10 @@ func (medium *Medium) newRequest(method, filePath string, body goio.Reader) (*ht
 	return request, nil
 }
 
-func (medium *Medium) do(method, filePath string, body goio.Reader) (*http.Response, error) {
+func (medium *Medium) do(method, filePath string, body goio.Reader) (
+	*http.Response,
+	error,
+) {
 	request, err := medium.newRequest(method, filePath, body)
 	if err != nil {
 		return nil, err
@@ -148,7 +160,8 @@ func (medium *Medium) do(method, filePath string, body goio.Reader) (*http.Respo
 	return medium.client.Do(request)
 }
 
-func statusError(operation, resource string, statusCode int) error {
+func statusError(operation, resource string, statusCode int) error { // legacy error contract
+
 	switch statusCode {
 	case http.StatusNotFound:
 		return core.E(operation, core.Concat("not found: ", resource), fs.ErrNotExist)
@@ -176,7 +189,8 @@ func closeWebDAVBody(closer goio.Closer) {
 	}
 }
 
-func (medium *Medium) putBytes(filePath string, data []byte) error {
+func (medium *Medium) putBytes(filePath string, data []byte) error { // legacy error contract
+
 	resource, err := medium.requiredResourceURL(opWriteMode, filePath)
 	if err != nil {
 		return err
@@ -196,7 +210,8 @@ func (medium *Medium) putBytes(filePath string, data []byte) error {
 	return nil
 }
 
-func (medium *Medium) ensureParent(filePath string) error {
+func (medium *Medium) ensureParent(filePath string) error { // legacy error contract
+
 	relative := cleanRelative(filePath)
 	parent := core.PathDir(relative)
 	if parent == "." || parent == "" {
@@ -206,7 +221,10 @@ func (medium *Medium) ensureParent(filePath string) error {
 }
 
 // Read reads a WebDAV resource into a string.
-func (medium *Medium) Read(filePath string) (string, error) {
+func (medium *Medium) Read(filePath string) (
+	string,
+	error,
+) {
 	resource, err := medium.requiredResourceURL(opRead, filePath)
 	if err != nil {
 		return "", err
@@ -227,18 +245,21 @@ func (medium *Medium) Read(filePath string) (string, error) {
 }
 
 // Write writes a WebDAV resource using the default file mode.
-func (medium *Medium) Write(filePath, content string) error {
+func (medium *Medium) Write(filePath, content string) error { // legacy error contract
+
 	return medium.WriteMode(filePath, content, 0644)
 }
 
 // WriteMode writes a WebDAV resource. The mode is intentionally ignored
 // because WebDAV has no portable POSIX permission model.
-func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error { // legacy error contract
+
 	return medium.putBytes(filePath, []byte(content))
 }
 
 // EnsureDir creates a WebDAV collection and any missing parent collections.
-func (medium *Medium) EnsureDir(filePath string) error {
+func (medium *Medium) EnsureDir(filePath string) error { // legacy error contract
+
 	relative := cleanRelative(filePath)
 	if relative == "" {
 		return nil
@@ -258,7 +279,8 @@ func (medium *Medium) EnsureDir(filePath string) error {
 	return nil
 }
 
-func (medium *Medium) mkcol(filePath string) error {
+func (medium *Medium) mkcol(filePath string) error { // legacy error contract
+
 	resource := medium.resourceURL(filePath)
 	response, err := medium.do("MKCOL", filePath, nil)
 	if err != nil {
@@ -288,7 +310,8 @@ func (medium *Medium) IsFile(filePath string) bool {
 }
 
 // Delete removes a file or empty collection.
-func (medium *Medium) Delete(filePath string) error {
+func (medium *Medium) Delete(filePath string) error { // legacy error contract
+
 	resource, err := medium.requiredResourceURL(opDelete, filePath)
 	if err != nil {
 		return err
@@ -319,7 +342,8 @@ func (medium *Medium) Delete(filePath string) error {
 }
 
 // DeleteAll removes a file or collection tree.
-func (medium *Medium) DeleteAll(filePath string) error {
+func (medium *Medium) DeleteAll(filePath string) error { // legacy error contract
+
 	resource, err := medium.requiredResourceURL(opDeleteAll, filePath)
 	if err != nil {
 		return err
@@ -336,7 +360,8 @@ func (medium *Medium) DeleteAll(filePath string) error {
 }
 
 // Rename moves a WebDAV resource to a new path.
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	source, err := medium.requiredResourceURL(opRename, oldPath)
 	if err != nil {
 		return err
@@ -368,7 +393,10 @@ func (medium *Medium) Rename(oldPath, newPath string) error {
 }
 
 // List returns the immediate children under a WebDAV collection.
-func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(filePath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	responses, requestPath, err := medium.propfind(filePath, "1")
 	if err != nil {
 		return nil, err
@@ -390,7 +418,10 @@ func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
 }
 
 // Stat returns metadata for a WebDAV resource.
-func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(filePath string) (
+	fs.FileInfo,
+	error,
+) {
 	resource, err := medium.requiredResourceURL("webdav.Stat", filePath)
 	if err != nil {
 		return nil, err
@@ -405,7 +436,11 @@ func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
 	return responses[0].fileInfo(requestPath), nil
 }
 
-func (medium *Medium) propfind(filePath, depth string) ([]davResponse, string, error) {
+func (medium *Medium) propfind(filePath, depth string) (
+	[]davResponse,
+	string,
+	error,
+) {
 	resource := medium.resourceURL(filePath)
 	request, err := medium.newRequest("PROPFIND", filePath, core.NewReader(propfindBody))
 	if err != nil {
@@ -431,7 +466,10 @@ func (medium *Medium) propfind(filePath, depth string) ([]davResponse, string, e
 }
 
 // Open opens a WebDAV resource as an fs.File.
-func (medium *Medium) Open(filePath string) (fs.File, error) {
+func (medium *Medium) Open(filePath string) (
+	fs.File,
+	error,
+) {
 	content, err := medium.Read(filePath)
 	if err != nil {
 		return nil, err
@@ -452,7 +490,10 @@ func (medium *Medium) Open(filePath string) (fs.File, error) {
 }
 
 // Create opens a buffered WebDAV writer that replaces the resource on close.
-func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	if _, err := medium.requiredResourceURL("webdav.Create", filePath); err != nil {
 		return nil, err
 	}
@@ -461,7 +502,10 @@ func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
 
 // Append opens a buffered WebDAV writer that appends locally then replaces the
 // resource on close.
-func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	if _, err := medium.requiredResourceURL("webdav.Append", filePath); err != nil {
 		return nil, err
 	}
@@ -478,7 +522,10 @@ func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
 }
 
 // ReadStream opens a WebDAV resource as an io.ReadCloser.
-func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(filePath string) (
+	goio.ReadCloser,
+	error,
+) {
 	resource, err := medium.requiredResourceURL(opReadStream, filePath)
 	if err != nil {
 		return nil, err
@@ -495,7 +542,10 @@ func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
 }
 
 // WriteStream opens a buffered WebDAV writer that replaces the resource on close.
-func (medium *Medium) WriteStream(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.Create(filePath)
 }
 
@@ -608,11 +658,17 @@ type webdavFile struct {
 	modTime time.Time
 }
 
-func (file *webdavFile) Stat() (fs.FileInfo, error) {
+func (file *webdavFile) Stat() (
+	fs.FileInfo,
+	error,
+) {
 	return coreio.NewFileInfo(file.name, int64(len(file.content)), file.mode, file.modTime, false), nil
 }
 
-func (file *webdavFile) Read(buffer []byte) (int, error) {
+func (file *webdavFile) Read(buffer []byte) (
+	int,
+	error,
+) {
 	if file.offset >= int64(len(file.content)) {
 		return 0, goio.EOF
 	}
@@ -621,7 +677,8 @@ func (file *webdavFile) Read(buffer []byte) (int, error) {
 	return bytesRead, nil
 }
 
-func (file *webdavFile) Close() error {
+func (file *webdavFile) Close() error { // legacy error contract
+
 	return nil
 }
 
@@ -632,11 +689,15 @@ type webdavWriteCloser struct {
 	mode   fs.FileMode
 }
 
-func (writer *webdavWriteCloser) Write(data []byte) (int, error) {
+func (writer *webdavWriteCloser) Write(data []byte) (
+	int,
+	error,
+) {
 	writer.data = append(writer.data, data...)
 	return len(data), nil
 }
 
-func (writer *webdavWriteCloser) Close() error {
+func (writer *webdavWriteCloser) Close() error { // legacy error contract
+
 	return writer.medium.WriteMode(writer.path, string(writer.data), writer.mode)
 }
diff --git a/pkg/medium/webdav/webdav_example_test.go b/go/pkg/medium/webdav/webdav_example_test.go
similarity index 100%
rename from pkg/medium/webdav/webdav_example_test.go
rename to go/pkg/medium/webdav/webdav_example_test.go
diff --git a/pkg/medium/webdav/webdav_test.go b/go/pkg/medium/webdav/webdav_test.go
similarity index 100%
rename from pkg/medium/webdav/webdav_test.go
rename to go/pkg/medium/webdav/webdav_test.go
diff --git a/s3/actions.go b/go/s3/actions.go
similarity index 100%
rename from s3/actions.go
rename to go/s3/actions.go
diff --git a/s3/actions_example_test.go b/go/s3/actions_example_test.go
similarity index 100%
rename from s3/actions_example_test.go
rename to go/s3/actions_example_test.go
diff --git a/s3/actions_test.go b/go/s3/actions_test.go
similarity index 100%
rename from s3/actions_test.go
rename to go/s3/actions_test.go
diff --git a/s3/s3.go b/go/s3/s3.go
similarity index 91%
rename from s3/s3.go
rename to go/s3/s3.go
index 1ea6a14..36e25aa 100644
--- a/s3/s3.go
+++ b/go/s3/s3.go
@@ -57,7 +57,8 @@ type Options struct {
 	Prefix string
 }
 
-func deleteObjectsError(prefix string, errs []types.Error) error {
+func deleteObjectsError(prefix string, errs []types.Error) error { // legacy error contract
+
 	if len(errs) == 0 {
 		return nil
 	}
@@ -80,7 +81,10 @@ func deleteObjectsError(prefix string, errs []types.Error) error {
 	return core.E(opS3DeleteAll, core.Concat("partial delete failed under ", prefix, ": ", core.Join("; ", details...)), nil)
 }
 
-func readAllString(reader goio.ReadCloser) (string, error) {
+func readAllString(reader goio.ReadCloser) (
+	string,
+	error,
+) {
 	defer closeS3Reader(reader)
 
 	result := core.ReadAll(reader)
@@ -120,7 +124,10 @@ func normalisePrefix(prefix string) string {
 
 // Example: medium, _ := s3.New(s3.Options{Bucket: "backups", Client: client, Prefix: "daily/"})
 // Example: _ = medium.Write("reports/daily.txt", "done")
-func New(options Options) (*Medium, error) {
+func New(options Options) (
+	*Medium,
+	error,
+) {
 	if options.Bucket == "" {
 		return nil, core.E("s3.New", "bucket name is required", fs.ErrInvalid)
 	}
@@ -152,7 +159,10 @@ func (medium *Medium) objectKey(filePath string) string {
 }
 
 // Example: content, _ := medium.Read("reports/daily.txt")
-func (medium *Medium) Read(filePath string) (string, error) {
+func (medium *Medium) Read(filePath string) (
+	string,
+	error,
+) {
 	key := medium.objectKey(filePath)
 	if key == "" {
 		return "", core.E(opS3Read, msgS3PathRequired, fs.ErrInvalid)
@@ -173,7 +183,8 @@ func (medium *Medium) Read(filePath string) (string, error) {
 }
 
 // Example: _ = medium.Write("reports/daily.txt", "done")
-func (medium *Medium) Write(filePath, content string) error {
+func (medium *Medium) Write(filePath, content string) error { // legacy error contract
+
 	key := medium.objectKey(filePath)
 	if key == "" {
 		return core.E("s3.Write", msgS3PathRequired, fs.ErrInvalid)
@@ -193,12 +204,14 @@ func (medium *Medium) Write(filePath, content string) error {
 // Example: _ = medium.WriteMode("keys/private.key", key, 0600)
 // Note: mode is intentionally ignored — S3 has no POSIX permission model.
 // Use S3 bucket policies and IAM for access control.
-func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error { // legacy error contract
+
 	return medium.Write(filePath, content)
 }
 
 // Example: _ = medium.EnsureDir("reports/2026")
-func (medium *Medium) EnsureDir(directoryPath string) error {
+func (medium *Medium) EnsureDir(directoryPath string) error { // legacy error contract
+
 	return nil
 }
 
@@ -219,7 +232,8 @@ func (medium *Medium) IsFile(filePath string) bool {
 }
 
 // Example: _ = medium.Delete("reports/daily.txt")
-func (medium *Medium) Delete(filePath string) error {
+func (medium *Medium) Delete(filePath string) error { // legacy error contract
+
 	key := medium.objectKey(filePath)
 	if key == "" {
 		return core.E("s3.Delete", msgS3PathRequired, fs.ErrInvalid)
@@ -236,7 +250,8 @@ func (medium *Medium) Delete(filePath string) error {
 }
 
 // Example: _ = medium.DeleteAll("reports/2026")
-func (medium *Medium) DeleteAll(filePath string) error {
+func (medium *Medium) DeleteAll(filePath string) error { // legacy error contract
+
 	key := medium.objectKey(filePath)
 	if key == "" {
 		return core.E(opS3DeleteAll, msgS3PathRequired, fs.ErrInvalid)
@@ -270,7 +285,11 @@ func (medium *Medium) DeleteAll(filePath string) error {
 	return nil
 }
 
-func (medium *Medium) deleteObjectBatch(prefix string, continuationToken *string) (*string, bool, error) {
+func (medium *Medium) deleteObjectBatch(prefix string, continuationToken *string) (
+	*string,
+	bool,
+	error,
+) {
 	listOutput, err := medium.client.ListObjectsV2(context.Background(), &awss3.ListObjectsV2Input{
 		Bucket:            aws.String(medium.bucket),
 		Prefix:            aws.String(prefix),
@@ -303,7 +322,8 @@ func (medium *Medium) deleteObjectBatch(prefix string, continuationToken *string
 }
 
 // Example: _ = medium.Rename("drafts/todo.txt", "archive/todo.txt")
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	oldKey := medium.objectKey(oldPath)
 	newKey := medium.objectKey(newPath)
 	if oldKey == "" || newKey == "" {
@@ -333,7 +353,10 @@ func (medium *Medium) Rename(oldPath, newPath string) error {
 }
 
 // Example: entries, _ := medium.List("reports")
-func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(filePath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	prefix := medium.objectKey(filePath)
 	if prefix != "" && !core.HasSuffix(prefix, "/") {
 		prefix += "/"
@@ -419,7 +442,10 @@ func s3ObjectEntry(name string, object types.Object) fs.DirEntry {
 }
 
 // Example: info, _ := medium.Stat("reports/daily.txt")
-func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(filePath string) (
+	fs.FileInfo,
+	error,
+) {
 	key := medium.objectKey(filePath)
 	if key == "" {
 		return nil, core.E("s3.Stat", msgS3PathRequired, fs.ErrInvalid)
@@ -451,7 +477,10 @@ func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
 	}, nil
 }
 
-func (medium *Medium) Open(filePath string) (fs.File, error) {
+func (medium *Medium) Open(filePath string) (
+	fs.File,
+	error,
+) {
 	key := medium.objectKey(filePath)
 	if key == "" {
 		return nil, core.E(opS3Open, msgS3PathRequired, fs.ErrInvalid)
@@ -488,7 +517,10 @@ func (medium *Medium) Open(filePath string) (fs.File, error) {
 }
 
 // Example: writer, _ := medium.Create("reports/daily.txt")
-func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	key := medium.objectKey(filePath)
 	if key == "" {
 		return nil, core.E("s3.Create", msgS3PathRequired, fs.ErrInvalid)
@@ -500,7 +532,10 @@ func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
 }
 
 // Example: writer, _ := medium.Append("reports/daily.txt")
-func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	key := medium.objectKey(filePath)
 	if key == "" {
 		return nil, core.E("s3.Append", msgS3PathRequired, fs.ErrInvalid)
@@ -527,7 +562,10 @@ func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
 }
 
 // Example: reader, _ := medium.ReadStream("reports/daily.txt")
-func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(filePath string) (
+	goio.ReadCloser,
+	error,
+) {
 	key := medium.objectKey(filePath)
 	if key == "" {
 		return nil, core.E("s3.ReadStream", msgS3PathRequired, fs.ErrInvalid)
@@ -544,7 +582,10 @@ func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
 }
 
 // Example: writer, _ := medium.WriteStream("reports/daily.txt")
-func (medium *Medium) WriteStream(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.Create(filePath)
 }
 
@@ -644,7 +685,10 @@ type s3File struct {
 	modTime time.Time
 }
 
-func (file *s3File) Stat() (fs.FileInfo, error) {
+func (file *s3File) Stat() (
+	fs.FileInfo,
+	error,
+) {
 	return &fileInfo{
 		name:    file.name,
 		size:    int64(len(file.content)),
@@ -653,7 +697,10 @@ func (file *s3File) Stat() (fs.FileInfo, error) {
 	}, nil
 }
 
-func (file *s3File) Read(buffer []byte) (int, error) {
+func (file *s3File) Read(buffer []byte) (
+	int,
+	error,
+) {
 	if file.offset >= int64(len(file.content)) {
 		return 0, goio.EOF
 	}
@@ -662,7 +709,8 @@ func (file *s3File) Read(buffer []byte) (int, error) {
 	return bytesRead, nil
 }
 
-func (file *s3File) Close() error {
+func (file *s3File) Close() error { // legacy error contract
+
 	return nil
 }
 
@@ -672,12 +720,16 @@ type s3WriteCloser struct {
 	data   []byte
 }
 
-func (writer *s3WriteCloser) Write(data []byte) (int, error) {
+func (writer *s3WriteCloser) Write(data []byte) (
+	int,
+	error,
+) {
 	writer.data = append(writer.data, data...)
 	return len(data), nil
 }
 
-func (writer *s3WriteCloser) Close() error {
+func (writer *s3WriteCloser) Close() error { // legacy error contract
+
 	_, err := writer.medium.client.PutObject(context.Background(), &awss3.PutObjectInput{
 		Bucket: aws.String(writer.medium.bucket),
 		Key:    aws.String(writer.key),
diff --git a/s3/s3_example_test.go b/go/s3/s3_example_test.go
similarity index 100%
rename from s3/s3_example_test.go
rename to go/s3/s3_example_test.go
diff --git a/s3/s3_test.go b/go/s3/s3_test.go
similarity index 100%
rename from s3/s3_test.go
rename to go/s3/s3_test.go
diff --git a/sigil/crypto_sigil.go b/go/sigil/crypto_sigil.go
similarity index 96%
rename from sigil/crypto_sigil.go
rename to go/sigil/crypto_sigil.go
index 24a9ff3..f77c27c 100644
--- a/sigil/crypto_sigil.go
+++ b/go/sigil/crypto_sigil.go
@@ -222,7 +222,10 @@ func (s *ChaChaPolySigil) SetObfuscator(obfuscator PreObfuscator) {
 // WARNING: when using a custom PreObfuscator, nonce uniqueness remains the
 // caller's responsibility. The PreObfuscator must treat the supplied entropy as
 // a per-message nonce and must not introduce deterministic nonce reuse.
-func NewChaChaPolySigil(key []byte, nonce any) (*ChaChaPolySigil, error) {
+func NewChaChaPolySigil(key []byte, nonce any) (
+	*ChaChaPolySigil,
+	error,
+) {
 	if len(key) != 32 {
 		return nil, InvalidKeyError
 	}
@@ -254,7 +257,10 @@ func NewChaChaPolySigil(key []byte, nonce any) (*ChaChaPolySigil, error) {
 	return sigil, nil
 }
 
-func (s *ChaChaPolySigil) In(data []byte) ([]byte, error) {
+func (s *ChaChaPolySigil) In(data []byte) (
+	[]byte,
+	error,
+) {
 	if s.key == nil {
 		return nil, NoKeyConfiguredError
 	}
@@ -286,7 +292,10 @@ func (s *ChaChaPolySigil) In(data []byte) ([]byte, error) {
 	return ciphertext, nil
 }
 
-func (s *ChaChaPolySigil) Out(data []byte) ([]byte, error) {
+func (s *ChaChaPolySigil) Out(data []byte) (
+	[]byte,
+	error,
+) {
 	if s.key == nil {
 		return nil, NoKeyConfiguredError
 	}
@@ -326,7 +335,10 @@ func (s *ChaChaPolySigil) Out(data []byte) ([]byte, error) {
 	return plaintext, nil
 }
 
-func (s *ChaChaPolySigil) newAEAD() (cipher.AEAD, error) {
+func (s *ChaChaPolySigil) newAEAD() (
+	cipher.AEAD,
+	error,
+) {
 	switch s.activeNonceSize() {
 	case chacha20poly1305.NonceSize:
 		return chacha20poly1305.New(s.key)
@@ -351,7 +363,10 @@ func cloneBytes(data []byte) []byte {
 }
 
 // Example: nonce, _ := sigil.NonceFromCiphertext(ciphertext)
-func NonceFromCiphertext(ciphertext []byte) ([]byte, error) {
+func NonceFromCiphertext(ciphertext []byte) (
+	[]byte,
+	error,
+) {
 	nonceSize := chacha20poly1305.NonceSizeX
 	if len(ciphertext) < nonceSize {
 		return nil, CiphertextTooShortError
diff --git a/sigil/crypto_sigil_example_test.go b/go/sigil/crypto_sigil_example_test.go
similarity index 100%
rename from sigil/crypto_sigil_example_test.go
rename to go/sigil/crypto_sigil_example_test.go
diff --git a/sigil/crypto_sigil_test.go b/go/sigil/crypto_sigil_test.go
similarity index 100%
rename from sigil/crypto_sigil_test.go
rename to go/sigil/crypto_sigil_test.go
diff --git a/sigil/sigil.go b/go/sigil/sigil.go
similarity index 89%
rename from sigil/sigil.go
rename to go/sigil/sigil.go
index 4f3df88..6725882 100644
--- a/sigil/sigil.go
+++ b/go/sigil/sigil.go
@@ -16,7 +16,10 @@ type Sigil interface {
 }
 
 // Example: encoded, _ := sigil.Transmute([]byte("payload"), []sigil.Sigil{hexSigil, gzipSigil})
-func Transmute(data []byte, sigils []Sigil) ([]byte, error) {
+func Transmute(data []byte, sigils []Sigil) (
+	[]byte,
+	error,
+) {
 	var err error
 	for _, sigilValue := range sigils {
 		data, err = sigilValue.In(data)
@@ -28,7 +31,10 @@ func Transmute(data []byte, sigils []Sigil) ([]byte, error) {
 }
 
 // Example: decoded, _ := sigil.Untransmute(encoded, []sigil.Sigil{hexSigil, gzipSigil})
-func Untransmute(data []byte, sigils []Sigil) ([]byte, error) {
+func Untransmute(data []byte, sigils []Sigil) (
+	[]byte,
+	error,
+) {
 	var err error
 	for i := len(sigils) - 1; i >= 0; i-- {
 		data, err = sigils[i].Out(data)
diff --git a/sigil/sigil_example_test.go b/go/sigil/sigil_example_test.go
similarity index 100%
rename from sigil/sigil_example_test.go
rename to go/sigil/sigil_example_test.go
diff --git a/sigil/sigil_test.go b/go/sigil/sigil_test.go
similarity index 100%
rename from sigil/sigil_test.go
rename to go/sigil/sigil_test.go
diff --git a/sigil/sigils.go b/go/sigil/sigils.go
similarity index 92%
rename from sigil/sigils.go
rename to go/sigil/sigils.go
index 5a80d43..f0114a8 100644
--- a/sigil/sigils.go
+++ b/go/sigil/sigils.go
@@ -27,7 +27,10 @@ const (
 // Example: reverseSigil, _ := sigil.NewSigil("reverse")
 type ReverseSigil struct{}
 
-func (sigil *ReverseSigil) In(data []byte) ([]byte, error) {
+func (sigil *ReverseSigil) In(data []byte) (
+	[]byte,
+	error,
+) {
 	if data == nil {
 		return nil, nil
 	}
@@ -38,14 +41,20 @@ func (sigil *ReverseSigil) In(data []byte) ([]byte, error) {
 	return reversed, nil
 }
 
-func (sigil *ReverseSigil) Out(data []byte) ([]byte, error) {
+func (sigil *ReverseSigil) Out(data []byte) (
+	[]byte,
+	error,
+) {
 	return sigil.In(data)
 }
 
 // Example: hexSigil, _ := sigil.NewSigil("hex")
 type HexSigil struct{}
 
-func (sigil *HexSigil) In(data []byte) ([]byte, error) {
+func (sigil *HexSigil) In(data []byte) (
+	[]byte,
+	error,
+) {
 	if data == nil {
 		return nil, nil
 	}
@@ -54,7 +63,10 @@ func (sigil *HexSigil) In(data []byte) ([]byte, error) {
 	return encodedBytes, nil
 }
 
-func (sigil *HexSigil) Out(data []byte) ([]byte, error) {
+func (sigil *HexSigil) Out(data []byte) (
+	[]byte,
+	error,
+) {
 	if data == nil {
 		return nil, nil
 	}
@@ -66,7 +78,10 @@ func (sigil *HexSigil) Out(data []byte) ([]byte, error) {
 // Example: base64Sigil, _ := sigil.NewSigil("base64")
 type Base64Sigil struct{}
 
-func (sigil *Base64Sigil) In(data []byte) ([]byte, error) {
+func (sigil *Base64Sigil) In(data []byte) (
+	[]byte,
+	error,
+) {
 	if data == nil {
 		return nil, nil
 	}
@@ -75,7 +90,10 @@ func (sigil *Base64Sigil) In(data []byte) ([]byte, error) {
 	return encodedBytes, nil
 }
 
-func (sigil *Base64Sigil) Out(data []byte) ([]byte, error) {
+func (sigil *Base64Sigil) Out(data []byte) (
+	[]byte,
+	error,
+) {
 	if data == nil {
 		return nil, nil
 	}
@@ -104,7 +122,10 @@ type sigilBuffer struct {
 	data []byte
 }
 
-func (buffer *sigilBuffer) Write(data []byte) (int, error) {
+func (buffer *sigilBuffer) Write(data []byte) (
+	int,
+	error,
+) {
 	buffer.data = append(buffer.data, data...)
 	return len(data), nil
 }
@@ -113,7 +134,10 @@ func (buffer *sigilBuffer) Bytes() []byte {
 	return buffer.data
 }
 
-func (sigil *GzipSigil) In(data []byte) ([]byte, error) {
+func (sigil *GzipSigil) In(data []byte) (
+	[]byte,
+	error,
+) {
 	if data == nil {
 		return nil, nil
 	}
@@ -137,7 +161,10 @@ func (sigil *GzipSigil) In(data []byte) ([]byte, error) {
 	return buffer.Bytes(), nil
 }
 
-func (sigil *GzipSigil) Out(data []byte) ([]byte, error) {
+func (sigil *GzipSigil) Out(data []byte) (
+	[]byte,
+	error,
+) {
 	if data == nil {
 		return nil, nil
 	}
@@ -165,7 +192,10 @@ func closeGzipReader(reader interface{ Close() error }) {
 // Example: jsonSigil := &sigil.JSONSigil{Indent: true}
 type JSONSigil struct{ Indent bool }
 
-func (sigil *JSONSigil) In(data []byte) ([]byte, error) {
+func (sigil *JSONSigil) In(data []byte) (
+	[]byte,
+	error,
+) {
 	if data == nil {
 		return nil, nil
 	}
@@ -186,7 +216,10 @@ func (sigil *JSONSigil) In(data []byte) ([]byte, error) {
 	return []byte(compact), nil
 }
 
-func (sigil *JSONSigil) Out(data []byte) ([]byte, error) {
+func (sigil *JSONSigil) Out(data []byte) (
+	[]byte,
+	error,
+) {
 	return data, nil
 }
 
@@ -201,7 +234,10 @@ func NewHashSigil(hashAlgorithm crypto.Hash) *HashSigil {
 	return &HashSigil{Hash: hashAlgorithm}
 }
 
-func (sigil *HashSigil) In(data []byte) ([]byte, error) {
+func (sigil *HashSigil) In(data []byte) (
+	[]byte,
+	error,
+) {
 	var hasher sigilHash
 	var err error
 	switch sigil.Hash {
@@ -254,7 +290,10 @@ func (sigil *HashSigil) In(data []byte) ([]byte, error) {
 	return hasher.Sum(nil), nil
 }
 
-func (sigil *HashSigil) Out(data []byte) ([]byte, error) {
+func (sigil *HashSigil) Out(data []byte) (
+	[]byte,
+	error,
+) {
 	return data, nil
 }
 
@@ -265,7 +304,10 @@ func (sigil *HashSigil) Out(data []byte) ([]byte, error) {
 // Example: hexSigil, _ := sigil.NewSigil("hex")
 // Example: gzipSigil, _ := sigil.NewSigil("gzip")
 // Example: transformed, _ := sigil.Transmute([]byte("payload"), []sigil.Sigil{hexSigil, gzipSigil})
-func NewSigil(sigilName string) (Sigil, error) {
+func NewSigil(sigilName string) (
+	Sigil,
+	error,
+) {
 	if sigilName == "chacha20poly1305" {
 		return nil, core.E("sigil.NewSigil", "chacha20poly1305 scheme requires key material; use NewChaChaPolySigil", fs.ErrInvalid)
 	}
diff --git a/sigil/sigils_example_test.go b/go/sigil/sigils_example_test.go
similarity index 100%
rename from sigil/sigils_example_test.go
rename to go/sigil/sigils_example_test.go
diff --git a/sigil/sigils_test.go b/go/sigil/sigils_test.go
similarity index 100%
rename from sigil/sigils_test.go
rename to go/sigil/sigils_test.go
diff --git a/sqlite/sqlite.go b/go/sqlite/sqlite.go
similarity index 91%
rename from sqlite/sqlite.go
rename to go/sqlite/sqlite.go
index 2db5a4a..cbc689a 100644
--- a/sqlite/sqlite.go
+++ b/go/sqlite/sqlite.go
@@ -90,7 +90,10 @@ func isValidTableName(name string) bool {
 
 // Example: medium, _ := sqlite.New(sqlite.Options{Path: ":memory:", Table: "files"})
 // Example: _ = medium.Write("config/app.yaml", "port: 8080")
-func New(options Options) (*Medium, error) {
+func New(options Options) (
+	*Medium,
+	error,
+) {
 	if options.Path == "" {
 		return nil, core.E(opSQLiteNew, "database path is required", fs.ErrInvalid)
 	}
@@ -129,7 +132,8 @@ func New(options Options) (*Medium, error) {
 }
 
 // Example: _ = medium.Close()
-func (medium *Medium) Close() error {
+func (medium *Medium) Close() error { // legacy error contract
+
 	if medium.database != nil {
 		return medium.database.Close()
 	}
@@ -145,7 +149,10 @@ func normaliseEntryPath(filePath string) string {
 }
 
 // Example: content, _ := medium.Read("config/app.yaml")
-func (medium *Medium) Read(filePath string) (string, error) {
+func (medium *Medium) Read(filePath string) (
+	string,
+	error,
+) {
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return "", core.E(opSQLiteRead, msgSQLitePathRequired, fs.ErrInvalid)
@@ -169,12 +176,14 @@ func (medium *Medium) Read(filePath string) (string, error) {
 }
 
 // Example: _ = medium.Write("config/app.yaml", "port: 8080")
-func (medium *Medium) Write(filePath, content string) error {
+func (medium *Medium) Write(filePath, content string) error { // legacy error contract
+
 	return medium.WriteMode(filePath, content, 0644)
 }
 
 // Example: _ = medium.WriteMode("keys/private.key", key, 0600)
-func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) error { // legacy error contract
+
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return core.E("sqlite.WriteMode", msgSQLitePathRequired, fs.ErrInvalid)
@@ -192,7 +201,8 @@ func (medium *Medium) WriteMode(filePath, content string, mode fs.FileMode) erro
 }
 
 // Example: _ = medium.EnsureDir("config")
-func (medium *Medium) EnsureDir(filePath string) error {
+func (medium *Medium) EnsureDir(filePath string) error { // legacy error contract
+
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return nil
@@ -227,7 +237,8 @@ func (medium *Medium) IsFile(filePath string) bool {
 }
 
 // Example: _ = medium.Delete("config/app.yaml")
-func (medium *Medium) Delete(filePath string) error {
+func (medium *Medium) Delete(filePath string) error { // legacy error contract
+
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return core.E(opSQLiteDelete, msgSQLitePathRequired, fs.ErrInvalid)
@@ -270,7 +281,8 @@ func (medium *Medium) Delete(filePath string) error {
 }
 
 // Example: _ = medium.DeleteAll("config")
-func (medium *Medium) DeleteAll(filePath string) error {
+func (medium *Medium) DeleteAll(filePath string) error { // legacy error contract
+
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return core.E(opSQLiteDeleteAll, msgSQLitePathRequired, fs.ErrInvalid)
@@ -301,7 +313,8 @@ type sqliteEntryRow struct {
 }
 
 // Example: _ = medium.Rename("drafts/todo.txt", "archive/todo.txt")
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	oldKey := normaliseEntryPath(oldPath)
 	newKey := normaliseEntryPath(newPath)
 	if oldKey == "" || newKey == "" {
@@ -349,7 +362,10 @@ func (medium *Medium) Rename(oldPath, newPath string) error {
 	return nil
 }
 
-func (medium *Medium) renameSource(tx *sql.Tx, oldKey string) (sqliteEntryRow, error) {
+func (medium *Medium) renameSource(tx *sql.Tx, oldKey string) (
+	sqliteEntryRow,
+	error,
+) {
 	var source sqliteEntryRow
 	source.path = oldKey
 	err := tx.QueryRow(
@@ -364,7 +380,8 @@ func (medium *Medium) renameSource(tx *sql.Tx, oldKey string) (sqliteEntryRow, e
 	return source, nil
 }
 
-func (medium *Medium) upsertEntry(tx *sql.Tx, entry sqliteEntryRow) error {
+func (medium *Medium) upsertEntry(tx *sql.Tx, entry sqliteEntryRow) error { // legacy error contract
+
 	_, err := tx.Exec(
 		`INSERT INTO `+medium.table+` (path, content, mode, is_dir, mtime) VALUES (?, ?, ?, ?, ?)
 		 ON CONFLICT(path) DO UPDATE SET content = excluded.content, mode = excluded.mode, is_dir = excluded.is_dir, mtime = excluded.mtime`,
@@ -373,7 +390,8 @@ func (medium *Medium) upsertEntry(tx *sql.Tx, entry sqliteEntryRow) error {
 	return err
 }
 
-func (medium *Medium) renameChildren(tx *sql.Tx, oldKey, newKey string) error {
+func (medium *Medium) renameChildren(tx *sql.Tx, oldKey, newKey string) error { // legacy error contract
+
 	oldPrefix := oldKey + "/"
 	children, err := medium.childrenWithPrefix(tx, oldPrefix)
 	if err != nil {
@@ -393,7 +411,10 @@ func (medium *Medium) renameChildren(tx *sql.Tx, oldKey, newKey string) error {
 	return nil
 }
 
-func (medium *Medium) childrenWithPrefix(tx *sql.Tx, oldPrefix string) ([]sqliteEntryRow, error) {
+func (medium *Medium) childrenWithPrefix(tx *sql.Tx, oldPrefix string) (
+	[]sqliteEntryRow,
+	error,
+) {
 	childRows, err := tx.Query(
 		`SELECT path, content, mode, is_dir, mtime FROM `+medium.table+` WHERE path LIKE ?`,
 		oldPrefix+"%",
@@ -418,7 +439,10 @@ func (medium *Medium) childrenWithPrefix(tx *sql.Tx, oldPrefix string) ([]sqlite
 }
 
 // Example: entries, _ := medium.List("config")
-func (medium *Medium) List(filePath string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(filePath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	prefix := normaliseEntryPath(filePath)
 	if prefix != "" {
 		prefix += "/"
@@ -509,7 +533,10 @@ func appendSQLiteDirEntry(name string, seen map[string]bool, entries *[]fs.DirEn
 }
 
 // Example: info, _ := medium.Stat("config/app.yaml")
-func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(filePath string) (
+	fs.FileInfo,
+	error,
+) {
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return nil, core.E(opSQLiteStat, msgSQLitePathRequired, fs.ErrInvalid)
@@ -540,7 +567,10 @@ func (medium *Medium) Stat(filePath string) (fs.FileInfo, error) {
 }
 
 // Example: file, _ := medium.Open("config/app.yaml")
-func (medium *Medium) Open(filePath string) (fs.File, error) {
+func (medium *Medium) Open(filePath string) (
+	fs.File,
+	error,
+) {
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return nil, core.E(opSQLiteOpen, msgSQLitePathRequired, fs.ErrInvalid)
@@ -572,7 +602,10 @@ func (medium *Medium) Open(filePath string) (fs.File, error) {
 }
 
 // Example: writer, _ := medium.Create("logs/app.log")
-func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return nil, core.E("sqlite.Create", msgSQLitePathRequired, fs.ErrInvalid)
@@ -584,7 +617,10 @@ func (medium *Medium) Create(filePath string) (goio.WriteCloser, error) {
 }
 
 // Example: writer, _ := medium.Append("logs/app.log")
-func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return nil, core.E("sqlite.Append", msgSQLitePathRequired, fs.ErrInvalid)
@@ -606,7 +642,10 @@ func (medium *Medium) Append(filePath string) (goio.WriteCloser, error) {
 }
 
 // Example: reader, _ := medium.ReadStream("logs/app.log")
-func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(filePath string) (
+	goio.ReadCloser,
+	error,
+) {
 	key := normaliseEntryPath(filePath)
 	if key == "" {
 		return nil, core.E(opSQLiteReadStream, msgSQLitePathRequired, fs.ErrInvalid)
@@ -634,7 +673,10 @@ func (medium *Medium) ReadStream(filePath string) (goio.ReadCloser, error) {
 }
 
 // Example: writer, _ := medium.WriteStream("logs/app.log")
-func (medium *Medium) WriteStream(filePath string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(filePath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.Create(filePath)
 }
 
@@ -715,7 +757,10 @@ type sqliteFile struct {
 	modTime time.Time
 }
 
-func (file *sqliteFile) Stat() (fs.FileInfo, error) {
+func (file *sqliteFile) Stat() (
+	fs.FileInfo,
+	error,
+) {
 	return &fileInfo{
 		name:    file.name,
 		size:    int64(len(file.content)),
@@ -724,7 +769,10 @@ func (file *sqliteFile) Stat() (fs.FileInfo, error) {
 	}, nil
 }
 
-func (file *sqliteFile) Read(buffer []byte) (int, error) {
+func (file *sqliteFile) Read(buffer []byte) (
+	int,
+	error,
+) {
 	if file.offset >= int64(len(file.content)) {
 		return 0, goio.EOF
 	}
@@ -733,7 +781,8 @@ func (file *sqliteFile) Read(buffer []byte) (int, error) {
 	return bytesRead, nil
 }
 
-func (file *sqliteFile) Close() error {
+func (file *sqliteFile) Close() error { // legacy error contract
+
 	return nil
 }
 
@@ -744,12 +793,16 @@ type sqliteWriteCloser struct {
 	mode   fs.FileMode
 }
 
-func (writer *sqliteWriteCloser) Write(data []byte) (int, error) {
+func (writer *sqliteWriteCloser) Write(data []byte) (
+	int,
+	error,
+) {
 	writer.data = append(writer.data, data...)
 	return len(data), nil
 }
 
-func (writer *sqliteWriteCloser) Close() error {
+func (writer *sqliteWriteCloser) Close() error { // legacy error contract
+
 	mode := writer.mode
 	if mode == 0 {
 		mode = 0644
diff --git a/sqlite/sqlite_example_test.go b/go/sqlite/sqlite_example_test.go
similarity index 100%
rename from sqlite/sqlite_example_test.go
rename to go/sqlite/sqlite_example_test.go
diff --git a/sqlite/sqlite_test.go b/go/sqlite/sqlite_test.go
similarity index 100%
rename from sqlite/sqlite_test.go
rename to go/sqlite/sqlite_test.go
diff --git a/store/doc.go b/go/store/doc.go
similarity index 100%
rename from store/doc.go
rename to go/store/doc.go
diff --git a/store/medium.go b/go/store/medium.go
similarity index 85%
rename from store/medium.go
rename to go/store/medium.go
index bad4724..a64a6ee 100644
--- a/store/medium.go
+++ b/go/store/medium.go
@@ -32,7 +32,10 @@ var _ fs.FS = (*Medium)(nil)
 
 // Example: medium, _ := store.NewMedium(store.Options{Path: "config.db"})
 // Example: _ = medium.Write("app/theme", "midnight")
-func NewMedium(options Options) (*Medium, error) {
+func NewMedium(options Options) (
+	*Medium,
+	error,
+) {
 	keyValueStore, err := New(options)
 	if err != nil {
 		return nil, err
@@ -51,7 +54,8 @@ func (medium *Medium) KeyValueStore() *KeyValueStore {
 }
 
 // Example: _ = medium.Close()
-func (medium *Medium) Close() error {
+func (medium *Medium) Close() error { // legacy error contract
+
 	return medium.keyValueStore.Close()
 }
 
@@ -68,7 +72,10 @@ func splitGroupKeyPath(entryPath string) (group, key string) {
 	return parts[0], parts[1]
 }
 
-func (medium *Medium) Read(entryPath string) (string, error) {
+func (medium *Medium) Read(entryPath string) (
+	string,
+	error,
+) {
 	group, key := splitGroupKeyPath(entryPath)
 	if key == "" {
 		return "", core.E("store.Read", msgStoreGroupKeyRequired, fs.ErrInvalid)
@@ -76,7 +83,8 @@ func (medium *Medium) Read(entryPath string) (string, error) {
 	return medium.keyValueStore.Get(group, key)
 }
 
-func (medium *Medium) Write(entryPath, content string) error {
+func (medium *Medium) Write(entryPath, content string) error { // legacy error contract
+
 	group, key := splitGroupKeyPath(entryPath)
 	if key == "" {
 		return core.E("store.Write", msgStoreGroupKeyRequired, fs.ErrInvalid)
@@ -87,12 +95,14 @@ func (medium *Medium) Write(entryPath, content string) error {
 // Example: _ = medium.WriteMode("app/theme", "midnight", 0600)
 // Note: mode is not persisted — the SQLite store has no entry_mode column.
 // Use Write when mode is irrelevant; WriteMode satisfies the Medium interface only.
-func (medium *Medium) WriteMode(entryPath, content string, mode fs.FileMode) error {
+func (medium *Medium) WriteMode(entryPath, content string, mode fs.FileMode) error { // legacy error contract
+
 	return medium.Write(entryPath, content)
 }
 
 // Example: _ = medium.EnsureDir("app")
-func (medium *Medium) EnsureDir(entryPath string) error {
+func (medium *Medium) EnsureDir(entryPath string) error { // legacy error contract
+
 	return nil
 }
 
@@ -105,7 +115,8 @@ func (medium *Medium) IsFile(entryPath string) bool {
 	return err == nil
 }
 
-func (medium *Medium) Delete(entryPath string) error {
+func (medium *Medium) Delete(entryPath string) error { // legacy error contract
+
 	group, key := splitGroupKeyPath(entryPath)
 	if group == "" {
 		return core.E("store.Delete", msgStorePathRequired, fs.ErrInvalid)
@@ -123,7 +134,8 @@ func (medium *Medium) Delete(entryPath string) error {
 	return medium.keyValueStore.Delete(group, key)
 }
 
-func (medium *Medium) DeleteAll(entryPath string) error {
+func (medium *Medium) DeleteAll(entryPath string) error { // legacy error contract
+
 	group, key := splitGroupKeyPath(entryPath)
 	if group == "" {
 		return core.E("store.DeleteAll", msgStorePathRequired, fs.ErrInvalid)
@@ -134,7 +146,8 @@ func (medium *Medium) DeleteAll(entryPath string) error {
 	return medium.keyValueStore.Delete(group, key)
 }
 
-func (medium *Medium) Rename(oldPath, newPath string) error {
+func (medium *Medium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	oldGroup, oldKey := splitGroupKeyPath(oldPath)
 	newGroup, newKey := splitGroupKeyPath(newPath)
 	if oldKey == "" || newKey == "" {
@@ -154,7 +167,10 @@ func (medium *Medium) Rename(oldPath, newPath string) error {
 }
 
 // Example: entries, _ := medium.List("app")
-func (medium *Medium) List(entryPath string) ([]fs.DirEntry, error) {
+func (medium *Medium) List(entryPath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	group, key := splitGroupKeyPath(entryPath)
 
 	if group == "" {
@@ -191,7 +207,10 @@ func (medium *Medium) List(entryPath string) ([]fs.DirEntry, error) {
 }
 
 // Example: info, _ := medium.Stat("app/theme")
-func (medium *Medium) Stat(entryPath string) (fs.FileInfo, error) {
+func (medium *Medium) Stat(entryPath string) (
+	fs.FileInfo,
+	error,
+) {
 	group, key := splitGroupKeyPath(entryPath)
 	if group == "" {
 		return nil, core.E("store.Stat", msgStorePathRequired, fs.ErrInvalid)
@@ -213,7 +232,10 @@ func (medium *Medium) Stat(entryPath string) (fs.FileInfo, error) {
 	return &keyValueFileInfo{name: key, size: int64(len(value))}, nil
 }
 
-func (medium *Medium) Open(entryPath string) (fs.File, error) {
+func (medium *Medium) Open(entryPath string) (
+	fs.File,
+	error,
+) {
 	group, key := splitGroupKeyPath(entryPath)
 	if key == "" {
 		return nil, core.E("store.Open", msgStoreGroupKeyRequired, fs.ErrInvalid)
@@ -225,7 +247,10 @@ func (medium *Medium) Open(entryPath string) (fs.File, error) {
 	return &keyValueFile{name: key, content: []byte(value)}, nil
 }
 
-func (medium *Medium) Create(entryPath string) (goio.WriteCloser, error) {
+func (medium *Medium) Create(entryPath string) (
+	goio.WriteCloser,
+	error,
+) {
 	group, key := splitGroupKeyPath(entryPath)
 	if key == "" {
 		return nil, core.E("store.Create", msgStoreGroupKeyRequired, fs.ErrInvalid)
@@ -233,7 +258,10 @@ func (medium *Medium) Create(entryPath string) (goio.WriteCloser, error) {
 	return &keyValueWriteCloser{keyValueStore: medium.keyValueStore, group: group, key: key}, nil
 }
 
-func (medium *Medium) Append(entryPath string) (goio.WriteCloser, error) {
+func (medium *Medium) Append(entryPath string) (
+	goio.WriteCloser,
+	error,
+) {
 	group, key := splitGroupKeyPath(entryPath)
 	if key == "" {
 		return nil, core.E("store.Append", msgStoreGroupKeyRequired, fs.ErrInvalid)
@@ -245,7 +273,10 @@ func (medium *Medium) Append(entryPath string) (goio.WriteCloser, error) {
 	return &keyValueWriteCloser{keyValueStore: medium.keyValueStore, group: group, key: key, data: []byte(existingValue)}, nil
 }
 
-func (medium *Medium) ReadStream(entryPath string) (goio.ReadCloser, error) {
+func (medium *Medium) ReadStream(entryPath string) (
+	goio.ReadCloser,
+	error,
+) {
 	group, key := splitGroupKeyPath(entryPath)
 	if key == "" {
 		return nil, core.E("store.ReadStream", msgStoreGroupKeyRequired, fs.ErrInvalid)
@@ -257,7 +288,10 @@ func (medium *Medium) ReadStream(entryPath string) (goio.ReadCloser, error) {
 	return goio.NopCloser(core.NewReader(value)), nil
 }
 
-func (medium *Medium) WriteStream(entryPath string) (goio.WriteCloser, error) {
+func (medium *Medium) WriteStream(entryPath string) (
+	goio.WriteCloser,
+	error,
+) {
 	return medium.Create(entryPath)
 }
 
@@ -323,7 +357,10 @@ func (entry *keyValueDirEntry) Type() fs.FileMode {
 	return 0
 }
 
-func (entry *keyValueDirEntry) Info() (fs.FileInfo, error) {
+func (entry *keyValueDirEntry) Info() (
+	fs.FileInfo,
+	error,
+) {
 	return &keyValueFileInfo{name: entry.name, size: entry.size, isDir: entry.isDir}, nil
 }
 
@@ -333,11 +370,17 @@ type keyValueFile struct {
 	offset  int64
 }
 
-func (file *keyValueFile) Stat() (fs.FileInfo, error) {
+func (file *keyValueFile) Stat() (
+	fs.FileInfo,
+	error,
+) {
 	return &keyValueFileInfo{name: file.name, size: int64(len(file.content))}, nil
 }
 
-func (file *keyValueFile) Read(buffer []byte) (int, error) {
+func (file *keyValueFile) Read(buffer []byte) (
+	int,
+	error,
+) {
 	if file.offset >= int64(len(file.content)) {
 		return 0, goio.EOF
 	}
@@ -355,11 +398,15 @@ type keyValueWriteCloser struct {
 	data          []byte
 }
 
-func (writer *keyValueWriteCloser) Write(data []byte) (int, error) {
+func (writer *keyValueWriteCloser) Write(data []byte) (
+	int,
+	error,
+) {
 	writer.data = append(writer.data, data...)
 	return len(data), nil
 }
 
-func (writer *keyValueWriteCloser) Close() error {
+func (writer *keyValueWriteCloser) Close() error { // legacy error contract
+
 	return writer.keyValueStore.Set(writer.group, writer.key, string(writer.data))
 }
diff --git a/store/medium_example_test.go b/go/store/medium_example_test.go
similarity index 100%
rename from store/medium_example_test.go
rename to go/store/medium_example_test.go
diff --git a/store/medium_test.go b/go/store/medium_test.go
similarity index 100%
rename from store/medium_test.go
rename to go/store/medium_test.go
diff --git a/store/store.go b/go/store/store.go
similarity index 91%
rename from store/store.go
rename to go/store/store.go
index 27daaa8..c5ca412 100644
--- a/store/store.go
+++ b/go/store/store.go
@@ -46,7 +46,10 @@ type Options struct {
 
 // Example: keyValueStore, _ := store.New(store.Options{Path: ":memory:"})
 // Example: _ = keyValueStore.Set("app", "theme", "midnight")
-func New(options Options) (*KeyValueStore, error) {
+func New(options Options) (
+	*KeyValueStore,
+	error,
+) {
 	if options.Path == "" {
 		return nil, core.E(opStoreNew, "database path is required", fs.ErrInvalid)
 	}
@@ -72,12 +75,16 @@ func New(options Options) (*KeyValueStore, error) {
 }
 
 // Example: _ = keyValueStore.Close()
-func (keyValueStore *KeyValueStore) Close() error {
+func (keyValueStore *KeyValueStore) Close() error { // legacy error contract
+
 	return keyValueStore.database.Close()
 }
 
 // Example: theme, _ := keyValueStore.Get("app", "theme")
-func (keyValueStore *KeyValueStore) Get(group, key string) (string, error) {
+func (keyValueStore *KeyValueStore) Get(group, key string) (
+	string,
+	error,
+) {
 	var value string
 	err := keyValueStore.database.QueryRow("SELECT entry_value FROM entries WHERE group_name = ? AND entry_key = ?", group, key).Scan(&value)
 	if err == sql.ErrNoRows {
@@ -90,7 +97,8 @@ func (keyValueStore *KeyValueStore) Get(group, key string) (string, error) {
 }
 
 // Example: _ = keyValueStore.Set("app", "theme", "midnight")
-func (keyValueStore *KeyValueStore) Set(group, key, value string) error {
+func (keyValueStore *KeyValueStore) Set(group, key, value string) error { // legacy error contract
+
 	_, err := keyValueStore.database.Exec(
 		`INSERT INTO entries (group_name, entry_key, entry_value) VALUES (?, ?, ?)
 		 ON CONFLICT(group_name, entry_key) DO UPDATE SET entry_value = excluded.entry_value`,
@@ -103,7 +111,8 @@ func (keyValueStore *KeyValueStore) Set(group, key, value string) error {
 }
 
 // Example: _ = keyValueStore.Delete("app", "theme")
-func (keyValueStore *KeyValueStore) Delete(group, key string) error {
+func (keyValueStore *KeyValueStore) Delete(group, key string) error { // legacy error contract
+
 	_, err := keyValueStore.database.Exec("DELETE FROM entries WHERE group_name = ? AND entry_key = ?", group, key)
 	if err != nil {
 		return core.E("store.Delete", "exec", err)
@@ -112,7 +121,10 @@ func (keyValueStore *KeyValueStore) Delete(group, key string) error {
 }
 
 // Example: count, _ := keyValueStore.Count("app")
-func (keyValueStore *KeyValueStore) Count(group string) (int, error) {
+func (keyValueStore *KeyValueStore) Count(group string) (
+	int,
+	error,
+) {
 	var count int
 	err := keyValueStore.database.QueryRow("SELECT COUNT(*) FROM entries WHERE group_name = ?", group).Scan(&count)
 	if err != nil {
@@ -122,7 +134,8 @@ func (keyValueStore *KeyValueStore) Count(group string) (int, error) {
 }
 
 // Example: _ = keyValueStore.DeleteGroup("app")
-func (keyValueStore *KeyValueStore) DeleteGroup(group string) error {
+func (keyValueStore *KeyValueStore) DeleteGroup(group string) error { // legacy error contract
+
 	_, err := keyValueStore.database.Exec("DELETE FROM entries WHERE group_name = ?", group)
 	if err != nil {
 		return core.E("store.DeleteGroup", "exec", err)
@@ -131,7 +144,10 @@ func (keyValueStore *KeyValueStore) DeleteGroup(group string) error {
 }
 
 // Example: groups, _ := keyValueStore.ListGroups()
-func (keyValueStore *KeyValueStore) ListGroups() ([]string, error) {
+func (keyValueStore *KeyValueStore) ListGroups() (
+	[]string,
+	error,
+) {
 	rows, err := keyValueStore.database.Query("SELECT DISTINCT group_name FROM entries ORDER BY group_name")
 	if err != nil {
 		return nil, core.E(opStoreListGroups, "query groups", err)
@@ -153,7 +169,10 @@ func (keyValueStore *KeyValueStore) ListGroups() ([]string, error) {
 }
 
 // Example: values, _ := keyValueStore.GetAll("app")
-func (keyValueStore *KeyValueStore) GetAll(group string) (map[string]string, error) {
+func (keyValueStore *KeyValueStore) GetAll(group string) (
+	map[string]string,
+	error,
+) {
 	rows, err := keyValueStore.database.Query("SELECT entry_key, entry_value FROM entries WHERE group_name = ?", group)
 	if err != nil {
 		return nil, core.E(opStoreGetAll, "query", err)
@@ -177,7 +196,10 @@ func (keyValueStore *KeyValueStore) GetAll(group string) (map[string]string, err
 // Example: keyValueStore, _ := store.New(store.Options{Path: ":memory:"})
 // Example: _ = keyValueStore.Set("user", "name", "alice")
 // Example: renderedText, _ := keyValueStore.Render("hello {{ .name }}", "user")
-func (keyValueStore *KeyValueStore) Render(templateText, group string) (string, error) {
+func (keyValueStore *KeyValueStore) Render(templateText, group string) (
+	string,
+	error,
+) {
 	rows, err := keyValueStore.database.Query("SELECT entry_key, entry_value FROM entries WHERE group_name = ?", group)
 	if err != nil {
 		return "", core.E(opStoreRender, "query", err)
diff --git a/store/store_example_test.go b/go/store/store_example_test.go
similarity index 100%
rename from store/store_example_test.go
rename to go/store/store_example_test.go
diff --git a/store/store_test.go b/go/store/store_test.go
similarity index 100%
rename from store/store_test.go
rename to go/store/store_test.go
diff --git a/workspace/command.go b/go/workspace/command.go
similarity index 100%
rename from workspace/command.go
rename to go/workspace/command.go
diff --git a/workspace/command_example_test.go b/go/workspace/command_example_test.go
similarity index 100%
rename from workspace/command_example_test.go
rename to go/workspace/command_example_test.go
diff --git a/workspace/command_test.go b/go/workspace/command_test.go
similarity index 100%
rename from workspace/command_test.go
rename to go/workspace/command_test.go
diff --git a/workspace/doc.go b/go/workspace/doc.go
similarity index 100%
rename from workspace/doc.go
rename to go/workspace/doc.go
diff --git a/workspace/service.go b/go/workspace/service.go
similarity index 96%
rename from workspace/service.go
rename to go/workspace/service.go
index a8274da..6638f6a 100644
--- a/workspace/service.go
+++ b/go/workspace/service.go
@@ -54,7 +54,10 @@ type workspaceSHA256Hash struct {
 	data []byte
 }
 
-func (hash *workspaceSHA256Hash) Write(data []byte) (int, error) {
+func (hash *workspaceSHA256Hash) Write(data []byte) (
+	int,
+	error,
+) {
 	hash.data = append(hash.data, data...)
 	return len(data), nil
 }
@@ -107,7 +110,10 @@ var _ EncryptedWorkspace = (*Service)(nil)
 // Example:     Medium: io.NewMemoryMedium(),
 // Example: })
 // Example: workspaceID, _ := service.CreateWorkspace("alice", "pass123")
-func New(options Options) (*Service, error) {
+func New(options Options) (
+	*Service,
+	error,
+) {
 	rootPath := options.RootPath
 	if rootPath == "" {
 		home := resolveWorkspaceHomeDirectory()
@@ -147,7 +153,10 @@ func New(options Options) (*Service, error) {
 }
 
 // Example: workspaceID, _ := service.CreateWorkspace("alice", "pass123")
-func (service *Service) CreateWorkspace(identifier, passphrase string) (string, error) {
+func (service *Service) CreateWorkspace(identifier, passphrase string) (
+	string,
+	error,
+) {
 	service.stateLock.Lock()
 	defer service.stateLock.Unlock()
 
@@ -184,7 +193,8 @@ func (service *Service) CreateWorkspace(identifier, passphrase string) (string,
 }
 
 // Example: _ = service.SwitchWorkspace(workspaceID)
-func (service *Service) SwitchWorkspace(workspaceID string) error {
+func (service *Service) SwitchWorkspace(workspaceID string) error { // legacy error contract
+
 	service.stateLock.Lock()
 	defer service.stateLock.Unlock()
 
@@ -200,7 +210,10 @@ func (service *Service) SwitchWorkspace(workspaceID string) error {
 	return nil
 }
 
-func (service *Service) resolveActiveWorkspaceFilePath(operation, workspaceFilePath string) (string, error) {
+func (service *Service) resolveActiveWorkspaceFilePath(operation, workspaceFilePath string) (
+	string,
+	error,
+) {
 	if service.activeWorkspaceID == "" {
 		return "", core.E(operation, "no active workspace", fs.ErrNotExist)
 	}
@@ -216,7 +229,10 @@ func (service *Service) resolveActiveWorkspaceFilePath(operation, workspaceFileP
 }
 
 // Example: cipherSigil, _ := service.workspaceCipherSigil("workspace.ReadWorkspaceFile")
-func (service *Service) workspaceCipherSigil(operation string) (*sigil.ChaChaPolySigil, error) {
+func (service *Service) workspaceCipherSigil(operation string) (
+	*sigil.ChaChaPolySigil,
+	error,
+) {
 	if service.activeWorkspaceID == "" {
 		return nil, core.E(operation, "no active workspace", fs.ErrNotExist)
 	}
@@ -240,7 +256,10 @@ func (service *Service) workspaceCipherSigil(operation string) (*sigil.ChaChaPol
 }
 
 // Example: content, _ := service.ReadWorkspaceFile("notes/todo.txt")
-func (service *Service) ReadWorkspaceFile(workspaceFilePath string) (string, error) {
+func (service *Service) ReadWorkspaceFile(workspaceFilePath string) (
+	string,
+	error,
+) {
 	service.stateLock.RLock()
 	defer service.stateLock.RUnlock()
 
@@ -264,7 +283,8 @@ func (service *Service) ReadWorkspaceFile(workspaceFilePath string) (string, err
 }
 
 // Example: _ = service.WriteWorkspaceFile("notes/todo.txt", "ship it")
-func (service *Service) WriteWorkspaceFile(workspaceFilePath, content string) error {
+func (service *Service) WriteWorkspaceFile(workspaceFilePath, content string) error { // legacy error contract
+
 	service.stateLock.Lock()
 	defer service.stateLock.Unlock()
 
@@ -328,7 +348,10 @@ func resolveWorkspaceHomeDirectory() string {
 	return core.Env("DIR_HOME")
 }
 
-func joinPathWithinRoot(root string, parts ...string) (string, error) {
+func joinPathWithinRoot(root string, parts ...string) (
+	string,
+	error,
+) {
 	candidate := core.Path(append([]string{root}, parts...)...)
 	separator := core.Env("CORE_PATH_SEPARATOR")
 	if separator == "" {
@@ -343,7 +366,10 @@ func joinPathWithinRoot(root string, parts ...string) (string, error) {
 	return "", fs.ErrPermission
 }
 
-func (service *Service) resolveWorkspaceDirectory(operation, workspaceID string) (string, error) {
+func (service *Service) resolveWorkspaceDirectory(operation, workspaceID string) (
+	string,
+	error,
+) {
 	if workspaceID == "" {
 		return "", core.E(operation, "workspace id is required", fs.ErrInvalid)
 	}
diff --git a/workspace/service_example_test.go b/go/workspace/service_example_test.go
similarity index 100%
rename from workspace/service_example_test.go
rename to go/workspace/service_example_test.go
diff --git a/workspace/service_test.go b/go/workspace/service_test.go
similarity index 100%
rename from workspace/service_test.go
rename to go/workspace/service_test.go
diff --git a/workspace/workspace.go b/go/workspace/workspace.go
similarity index 87%
rename from workspace/workspace.go
rename to go/workspace/workspace.go
index cca063f..2c49843 100644
--- a/workspace/workspace.go
+++ b/go/workspace/workspace.go
@@ -26,7 +26,10 @@ type Workspace struct {
 }
 
 // NewWorkspace creates a workspace service backed by medium under baseSubpath.
-func NewWorkspace(medium coreio.Medium, baseSubpath string) (*Workspace, error) {
+func NewWorkspace(medium coreio.Medium, baseSubpath string) (
+	*Workspace,
+	error,
+) {
 	if medium == nil {
 		return nil, core.E(opNewWorkspace, "storage medium is required", fs.ErrInvalid)
 	}
@@ -46,7 +49,10 @@ func NewWorkspace(medium coreio.Medium, baseSubpath string) (*Workspace, error)
 }
 
 // CreateWorkspace creates a named workspace directory and returns a medium scoped to it.
-func (workspace *Workspace) CreateWorkspace(name string) (coreio.Medium, error) {
+func (workspace *Workspace) CreateWorkspace(name string) (
+	coreio.Medium,
+	error,
+) {
 	if workspace == nil {
 		return nil, core.E(opCreateWorkspace, errWorkspaceServiceNotConfigured, fs.ErrInvalid)
 	}
@@ -70,7 +76,8 @@ func (workspace *Workspace) CreateWorkspace(name string) (coreio.Medium, error)
 }
 
 // SwitchWorkspace records the named workspace as the current workspace.
-func (workspace *Workspace) SwitchWorkspace(name string) error {
+func (workspace *Workspace) SwitchWorkspace(name string) error { // legacy error contract
+
 	if workspace == nil {
 		return core.E(opSwitchWorkspace, errWorkspaceServiceNotConfigured, fs.ErrInvalid)
 	}
@@ -99,7 +106,10 @@ func (workspace *Workspace) CurrentWorkspace() string {
 }
 
 // ReadWorkspaceFile reads a file from the named workspace.
-func (workspace *Workspace) ReadWorkspaceFile(name, filePath string) (string, error) {
+func (workspace *Workspace) ReadWorkspaceFile(name, filePath string) (
+	string,
+	error,
+) {
 	if workspace == nil {
 		return "", core.E("workspace.ReadWorkspaceFile", errWorkspaceServiceNotConfigured, fs.ErrInvalid)
 	}
@@ -114,7 +124,8 @@ func (workspace *Workspace) ReadWorkspaceFile(name, filePath string) (string, er
 }
 
 // WriteWorkspaceFile writes a file into the named workspace.
-func (workspace *Workspace) WriteWorkspaceFile(name, filePath, content string) error {
+func (workspace *Workspace) WriteWorkspaceFile(name, filePath, content string) error { // legacy error contract
+
 	if workspace == nil {
 		return core.E("workspace.WriteWorkspaceFile", errWorkspaceServiceNotConfigured, fs.ErrInvalid)
 	}
@@ -129,7 +140,10 @@ func (workspace *Workspace) WriteWorkspaceFile(name, filePath, content string) e
 }
 
 // ListWorkspaceFiles lists entries under a workspace-relative directory.
-func (workspace *Workspace) ListWorkspaceFiles(name, directoryPath string) ([]fs.DirEntry, error) {
+func (workspace *Workspace) ListWorkspaceFiles(name, directoryPath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	if workspace == nil {
 		return nil, core.E("workspace.ListWorkspaceFiles", errWorkspaceServiceNotConfigured, fs.ErrInvalid)
 	}
@@ -179,7 +193,10 @@ func (workspace *Workspace) HandleWorkspaceCommand(command WorkspaceCommand) cor
 	}
 }
 
-func (workspace *Workspace) workspaceFilePath(operation, name, filePath string, allowEmptyPath bool) (string, error) {
+func (workspace *Workspace) workspaceFilePath(operation, name, filePath string, allowEmptyPath bool) (
+	string,
+	error,
+) {
 	_, workspacePath, err := workspace.workspaceNameAndPath(operation, name)
 	if err != nil {
 		return "", err
@@ -194,12 +211,19 @@ func (workspace *Workspace) workspaceFilePath(operation, name, filePath string,
 	return joinMediumSubpaths(workspacePath, cleanFilePath), nil
 }
 
-func (workspace *Workspace) workspacePath(operation, name string) (string, error) {
+func (workspace *Workspace) workspacePath(operation, name string) (
+	string,
+	error,
+) {
 	_, workspacePath, err := workspace.workspaceNameAndPath(operation, name)
 	return workspacePath, err
 }
 
-func (workspace *Workspace) workspaceNameAndPath(operation, name string) (string, string, error) {
+func (workspace *Workspace) workspaceNameAndPath(operation, name string) (
+	string,
+	string,
+	error,
+) {
 	if workspace == nil || workspace.medium == nil {
 		return "", "", core.E(operation, errWorkspaceServiceNotConfigured, fs.ErrInvalid)
 	}
@@ -217,7 +241,10 @@ func (workspace *Workspace) scopedMedium(root string) coreio.Medium {
 	}
 }
 
-func cleanWorkspaceName(operation, name string) (string, error) {
+func cleanWorkspaceName(operation, name string) (
+	string,
+	error,
+) {
 	name = core.Trim(name)
 	if name == "" || name == "." || name == ".." {
 		return "", core.E(operation, "workspace name is required", fs.ErrInvalid)
@@ -228,7 +255,10 @@ func cleanWorkspaceName(operation, name string) (string, error) {
 	return name, nil
 }
 
-func cleanMediumSubpath(operation, subpath string, allowEmpty bool) (string, error) {
+func cleanMediumSubpath(operation, subpath string, allowEmpty bool) (
+	string,
+	error,
+) {
 	subpath = core.Trim(core.Replace(subpath, "\\", "/"))
 	if subpath == "" || subpath == "." {
 		if allowEmpty {
@@ -275,7 +305,10 @@ type scopedMedium struct {
 var _ coreio.Medium = (*scopedMedium)(nil)
 var _ fs.FS = (*scopedMedium)(nil)
 
-func (medium *scopedMedium) scopedPath(operation, entryPath string, allowRoot bool) (string, error) {
+func (medium *scopedMedium) scopedPath(operation, entryPath string, allowRoot bool) (
+	string,
+	error,
+) {
 	cleanPath, err := cleanMediumSubpath(operation, entryPath, allowRoot)
 	if err != nil {
 		return "", err
@@ -283,7 +316,10 @@ func (medium *scopedMedium) scopedPath(operation, entryPath string, allowRoot bo
 	return joinMediumSubpaths(medium.root, cleanPath), nil
 }
 
-func (medium *scopedMedium) Read(entryPath string) (string, error) {
+func (medium *scopedMedium) Read(entryPath string) (
+	string,
+	error,
+) {
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.Read", entryPath, false)
 	if err != nil {
 		return "", err
@@ -291,11 +327,13 @@ func (medium *scopedMedium) Read(entryPath string) (string, error) {
 	return medium.medium.Read(scopedPath)
 }
 
-func (medium *scopedMedium) Write(entryPath, content string) error {
+func (medium *scopedMedium) Write(entryPath, content string) error { // legacy error contract
+
 	return medium.WriteMode(entryPath, content, 0644)
 }
 
-func (medium *scopedMedium) WriteMode(entryPath, content string, mode fs.FileMode) error {
+func (medium *scopedMedium) WriteMode(entryPath, content string, mode fs.FileMode) error { // legacy error contract
+
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.WriteMode", entryPath, false)
 	if err != nil {
 		return err
@@ -303,7 +341,8 @@ func (medium *scopedMedium) WriteMode(entryPath, content string, mode fs.FileMod
 	return medium.medium.WriteMode(scopedPath, content, mode)
 }
 
-func (medium *scopedMedium) EnsureDir(entryPath string) error {
+func (medium *scopedMedium) EnsureDir(entryPath string) error { // legacy error contract
+
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.EnsureDir", entryPath, true)
 	if err != nil {
 		return err
@@ -319,7 +358,8 @@ func (medium *scopedMedium) IsFile(entryPath string) bool {
 	return medium.medium.IsFile(scopedPath)
 }
 
-func (medium *scopedMedium) Delete(entryPath string) error {
+func (medium *scopedMedium) Delete(entryPath string) error { // legacy error contract
+
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.Delete", entryPath, false)
 	if err != nil {
 		return err
@@ -327,7 +367,8 @@ func (medium *scopedMedium) Delete(entryPath string) error {
 	return medium.medium.Delete(scopedPath)
 }
 
-func (medium *scopedMedium) DeleteAll(entryPath string) error {
+func (medium *scopedMedium) DeleteAll(entryPath string) error { // legacy error contract
+
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.DeleteAll", entryPath, false)
 	if err != nil {
 		return err
@@ -335,7 +376,8 @@ func (medium *scopedMedium) DeleteAll(entryPath string) error {
 	return medium.medium.DeleteAll(scopedPath)
 }
 
-func (medium *scopedMedium) Rename(oldPath, newPath string) error {
+func (medium *scopedMedium) Rename(oldPath, newPath string) error { // legacy error contract
+
 	scopedOldPath, err := medium.scopedPath("workspace.scopedMedium.Rename", oldPath, false)
 	if err != nil {
 		return err
@@ -347,7 +389,10 @@ func (medium *scopedMedium) Rename(oldPath, newPath string) error {
 	return medium.medium.Rename(scopedOldPath, scopedNewPath)
 }
 
-func (medium *scopedMedium) List(entryPath string) ([]fs.DirEntry, error) {
+func (medium *scopedMedium) List(entryPath string) (
+	[]fs.DirEntry,
+	error,
+) {
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.List", entryPath, true)
 	if err != nil {
 		return nil, err
@@ -355,7 +400,10 @@ func (medium *scopedMedium) List(entryPath string) ([]fs.DirEntry, error) {
 	return medium.medium.List(scopedPath)
 }
 
-func (medium *scopedMedium) Stat(entryPath string) (fs.FileInfo, error) {
+func (medium *scopedMedium) Stat(entryPath string) (
+	fs.FileInfo,
+	error,
+) {
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.Stat", entryPath, true)
 	if err != nil {
 		return nil, err
@@ -363,7 +411,10 @@ func (medium *scopedMedium) Stat(entryPath string) (fs.FileInfo, error) {
 	return medium.medium.Stat(scopedPath)
 }
 
-func (medium *scopedMedium) Open(entryPath string) (fs.File, error) {
+func (medium *scopedMedium) Open(entryPath string) (
+	fs.File,
+	error,
+) {
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.Open", entryPath, false)
 	if err != nil {
 		return nil, err
@@ -371,7 +422,10 @@ func (medium *scopedMedium) Open(entryPath string) (fs.File, error) {
 	return medium.medium.Open(scopedPath)
 }
 
-func (medium *scopedMedium) Create(entryPath string) (goio.WriteCloser, error) {
+func (medium *scopedMedium) Create(entryPath string) (
+	goio.WriteCloser,
+	error,
+) {
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.Create", entryPath, false)
 	if err != nil {
 		return nil, err
@@ -379,7 +433,10 @@ func (medium *scopedMedium) Create(entryPath string) (goio.WriteCloser, error) {
 	return medium.medium.Create(scopedPath)
 }
 
-func (medium *scopedMedium) Append(entryPath string) (goio.WriteCloser, error) {
+func (medium *scopedMedium) Append(entryPath string) (
+	goio.WriteCloser,
+	error,
+) {
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.Append", entryPath, false)
 	if err != nil {
 		return nil, err
@@ -387,7 +444,10 @@ func (medium *scopedMedium) Append(entryPath string) (goio.WriteCloser, error) {
 	return medium.medium.Append(scopedPath)
 }
 
-func (medium *scopedMedium) ReadStream(entryPath string) (goio.ReadCloser, error) {
+func (medium *scopedMedium) ReadStream(entryPath string) (
+	goio.ReadCloser,
+	error,
+) {
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.ReadStream", entryPath, false)
 	if err != nil {
 		return nil, err
@@ -395,7 +455,10 @@ func (medium *scopedMedium) ReadStream(entryPath string) (goio.ReadCloser, error
 	return medium.medium.ReadStream(scopedPath)
 }
 
-func (medium *scopedMedium) WriteStream(entryPath string) (goio.WriteCloser, error) {
+func (medium *scopedMedium) WriteStream(entryPath string) (
+	goio.WriteCloser,
+	error,
+) {
 	scopedPath, err := medium.scopedPath("workspace.scopedMedium.WriteStream", entryPath, false)
 	if err != nil {
 		return nil, err
diff --git a/workspace/workspace_example_test.go b/go/workspace/workspace_example_test.go
similarity index 100%
rename from workspace/workspace_example_test.go
rename to go/workspace/workspace_example_test.go
diff --git a/workspace/workspace_test.go b/go/workspace/workspace_test.go
similarity index 100%
rename from workspace/workspace_test.go
rename to go/workspace/workspace_test.go