diff --git a/CLAUDE.md b/CLAUDE.md
index 64c06eb..278880b 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -60,7 +60,7 @@ All file operations use `io.Medium` from `forge.lthn.ai/core/go-io`. Production
 
 - **UK English** in comments and strings (colour, organisation, notarisation)
 - **Strict types** — all parameters and return types explicitly typed
-- **Error wrapping** — `fmt.Errorf("package.Function: message: %w", err)`
+- **Error wrapping** — `coreerr.E("package.Function", "message", err)` via `coreerr "forge.lthn.ai/core/go-log"`
 - **testify** (`assert`/`require`) for assertions
 - **Test naming** — `_Good` (happy path), `_Bad` (expected errors), `_Ugly` (edge cases)
 - **Conventional commits** — `type(scope): description`
diff --git a/cmd/build/cmd_build.go b/cmd/build/cmd_build.go
index bf14040..58176fe 100644
--- a/cmd/build/cmd_build.go
+++ b/cmd/build/cmd_build.go
@@ -5,12 +5,12 @@ import (
 	"embed"
 
 	"forge.lthn.ai/core/cli/pkg/cli"
-	"forge.lthn.ai/core/go-build/locales"
+	_ "forge.lthn.ai/core/go-build/locales" // registers locale translations
 	"forge.lthn.ai/core/go-i18n"
 )
 
 func init() {
-	cli.RegisterCommands(AddBuildCommands, locales.FS)
+	cli.RegisterCommands(AddBuildCommands)
 }
 
 // Style aliases from shared package
diff --git a/cmd/build/cmd_pwa.go b/cmd/build/cmd_pwa.go
index 1a89504..6444783 100644
--- a/cmd/build/cmd_pwa.go
+++ b/cmd/build/cmd_pwa.go
@@ -222,11 +222,7 @@ func downloadAsset(assetURL, destDir string) error {
 func runBuild(fromPath string) error {
 	fmt.Printf("%s %s\n", i18n.T("cmd.build.from_path.starting"), fromPath)
 
-	info, err := os.Stat(fromPath)
-	if err != nil {
-		return coreerr.E("pwa.runBuild", i18n.T("cmd.build.from_path.error.invalid_path"), err)
-	}
-	if !info.IsDir() {
+	if !coreio.Local.IsDir(fromPath) {
 		return coreerr.E("pwa.runBuild", i18n.T("cmd.build.from_path.error.must_be_directory"), nil)
 	}
 
diff --git a/cmd/sdk/cmd.go b/cmd/sdk/cmd.go
index 853b89e..92c139f 100644
--- a/cmd/sdk/cmd.go
+++ b/cmd/sdk/cmd.go
@@ -8,11 +8,10 @@
 package sdkcmd
 
 import (
-	"fmt"
 	"os"
 
-	"forge.lthn.ai/core/go-build/pkg/sdk"
 	"forge.lthn.ai/core/cli/pkg/cli"
+	"forge.lthn.ai/core/go-build/pkg/sdk"
 	"forge.lthn.ai/core/go-i18n"
 	coreerr "forge.lthn.ai/core/go-log"
 )
@@ -97,10 +96,10 @@ func runSDKDiff(basePath, specPath string) error {
 		return coreerr.E("sdk.Diff", i18n.T("cmd.sdk.diff.error.base_required"), nil)
 	}
 
-	fmt.Printf("%s %s\n", sdkHeaderStyle.Render(i18n.T("cmd.sdk.diff.label")), i18n.ProgressSubject("check", "breaking changes"))
-	fmt.Printf("  %s %s\n", i18n.T("cmd.sdk.diff.base_label"), sdkDimStyle.Render(basePath))
-	fmt.Printf("  %s %s\n", i18n.Label("current"), sdkDimStyle.Render(specPath))
-	fmt.Println()
+	cli.Print("%s %s\n", sdkHeaderStyle.Render(i18n.T("cmd.sdk.diff.label")), i18n.ProgressSubject("check", "breaking changes"))
+	cli.Print("  %s %s\n", i18n.T("cmd.sdk.diff.base_label"), sdkDimStyle.Render(basePath))
+	cli.Print("  %s %s\n", i18n.Label("current"), sdkDimStyle.Render(specPath))
+	cli.Blank()
 
 	result, err := sdk.Diff(basePath, specPath)
 	if err != nil {
@@ -108,14 +107,14 @@ func runSDKDiff(basePath, specPath string) error {
 	}
 
 	if result.Breaking {
-		fmt.Printf("%s %s\n", sdkErrorStyle.Render(i18n.T("cmd.sdk.diff.breaking")), result.Summary)
+		cli.Print("%s %s\n", sdkErrorStyle.Render(i18n.T("cmd.sdk.diff.breaking")), result.Summary)
 		for _, change := range result.Changes {
-			fmt.Printf("  - %s\n", change)
+			cli.Print("  - %s\n", change)
 		}
 		return cli.Exit(1, cli.Err("%s", result.Summary))
 	}
 
-	fmt.Printf("%s %s\n", sdkSuccessStyle.Render(i18n.T("cmd.sdk.label.ok")), result.Summary)
+	cli.Print("%s %s\n", sdkSuccessStyle.Render(i18n.T("cmd.sdk.label.ok")), result.Summary)
 	return nil
 }
 
@@ -127,15 +126,15 @@ func runSDKValidate(specPath string) error {
 
 	s := sdk.New(projectDir, &sdk.Config{Spec: specPath})
 
-	fmt.Printf("%s %s\n", sdkHeaderStyle.Render(i18n.T("cmd.sdk.label.sdk")), i18n.T("cmd.sdk.validate.validating"))
+	cli.Print("%s %s\n", sdkHeaderStyle.Render(i18n.T("cmd.sdk.label.sdk")), i18n.T("cmd.sdk.validate.validating"))
 
 	detectedPath, err := s.DetectSpec()
 	if err != nil {
-		fmt.Printf("%s %v\n", sdkErrorStyle.Render(i18n.Label("error")), err)
+		cli.Print("%s %v\n", sdkErrorStyle.Render(i18n.Label("error")), err)
 		return err
 	}
 
-	fmt.Printf("  %s %s\n", i18n.Label("spec"), sdkDimStyle.Render(detectedPath))
-	fmt.Printf("%s %s\n", sdkSuccessStyle.Render(i18n.T("cmd.sdk.label.ok")), i18n.T("cmd.sdk.validate.valid"))
+	cli.Print("  %s %s\n", i18n.Label("spec"), sdkDimStyle.Render(detectedPath))
+	cli.Print("%s %s\n", sdkSuccessStyle.Render(i18n.T("cmd.sdk.label.ok")), i18n.T("cmd.sdk.validate.valid"))
 	return nil
 }
diff --git a/locales/embed.go b/locales/embed.go
index 410cb55..ac9a964 100644
--- a/locales/embed.go
+++ b/locales/embed.go
@@ -1,7 +1,15 @@
 // Package locales embeds translation files for this module.
 package locales
 
-import "embed"
+import (
+	"embed"
+
+	"forge.lthn.ai/core/go-i18n"
+)
 
 //go:embed *.json
 var FS embed.FS
+
+func init() {
+	i18n.RegisterLocales(FS, ".")
+}
diff --git a/pkg/api/provider_test.go b/pkg/api/provider_test.go
index dccad3c..d559b8d 100644
--- a/pkg/api/provider_test.go
+++ b/pkg/api/provider_test.go
@@ -3,9 +3,12 @@
 package api
 
 import (
+	"os"
 	"testing"
 
+	"forge.lthn.ai/core/go-build/pkg/build"
 	"github.com/stretchr/testify/assert"
+	"github.com/stretchr/testify/require"
 )
 
 func TestBuildProvider_Good_Identity(t *testing.T) {
@@ -75,3 +78,38 @@ func TestBuildProvider_Good_NilHub(t *testing.T) {
 	// emitEvent should not panic with nil hub
 	p.emitEvent("build.started", map[string]any{"test": true})
 }
+
+func TestGetBuilder_Good_SupportedTypes(t *testing.T) {
+	b, err := getBuilder(build.ProjectTypeGo)
+	require.NoError(t, err)
+	assert.Equal(t, "go", b.Name())
+
+	b, err = getBuilder(build.ProjectTypeWails)
+	require.NoError(t, err)
+	assert.Equal(t, "wails", b.Name())
+}
+
+func TestGetBuilder_Bad_UnsupportedType(t *testing.T) {
+	_, err := getBuilder(build.ProjectType("unknown"))
+	assert.ErrorIs(t, err, os.ErrNotExist)
+}
+
+func TestBuildProvider_Good_ResolveDir(t *testing.T) {
+	p := NewProvider("/tmp", nil)
+	dir, err := p.resolveDir()
+	require.NoError(t, err)
+	assert.Equal(t, "/tmp", dir)
+}
+
+func TestBuildProvider_Good_ResolveDirRelative(t *testing.T) {
+	p := NewProvider(".", nil)
+	dir, err := p.resolveDir()
+	require.NoError(t, err)
+	// Should return an absolute path
+	assert.True(t, len(dir) > 1 && dir[0] == '/')
+}
+
+func TestBuildProvider_Good_MediumSet(t *testing.T) {
+	p := NewProvider(".", nil)
+	assert.NotNil(t, p.medium, "medium should be set to io.Local")
+}
diff --git a/pkg/build/builders/linuxkit.go b/pkg/build/builders/linuxkit.go
index bcc7976..ef254fe 100644
--- a/pkg/build/builders/linuxkit.go
+++ b/pkg/build/builders/linuxkit.go
@@ -262,7 +262,7 @@ func (b *LinuxKitBuilder) validateLinuxKitCli() error {
 	}
 
 	for _, p := range paths {
-		if _, err := os.Stat(p); err == nil {
+		if io.Local.IsFile(p) {
 			return nil
 		}
 	}
diff --git a/pkg/build/builders/taskfile.go b/pkg/build/builders/taskfile.go
index ca3e807..de68e87 100644
--- a/pkg/build/builders/taskfile.go
+++ b/pkg/build/builders/taskfile.go
@@ -267,7 +267,7 @@ func (b *TaskfileBuilder) validateTaskCli() error {
 	}
 
 	for _, p := range paths {
-		if _, err := os.Stat(p); err == nil {
+		if io.Local.IsFile(p) {
 			return nil
 		}
 	}
diff --git a/pkg/release/publishers/scoop.go b/pkg/release/publishers/scoop.go
index af54091..8b15ba0 100644
--- a/pkg/release/publishers/scoop.go
+++ b/pkg/release/publishers/scoop.go
@@ -210,7 +210,7 @@ func (p *ScoopPublisher) commitToBucket(ctx context.Context, bucket string, data
 
 	// Ensure bucket directory exists
 	bucketDir := filepath.Join(tmpDir, "bucket")
-	if _, err := os.Stat(bucketDir); os.IsNotExist(err) {
+	if !coreio.Local.IsDir(bucketDir) {
 		bucketDir = tmpDir // Some repos put manifests in root
 	}