diff --git a/cmd/codegen/main.go b/cmd/codegen/main.go
index 00f20dc..85bd76b 100644
--- a/cmd/codegen/main.go
+++ b/cmd/codegen/main.go
@@ -8,7 +8,6 @@ package main
 
 import (
 	"encoding/json"
-	"fmt"
 	goio "io"
 	"os"
 
@@ -19,12 +18,12 @@ import (
 func run(r goio.Reader, w goio.Writer) error {
 	data, err := goio.ReadAll(r)
 	if err != nil {
-		return fmt.Errorf("codegen: reading stdin: %w", err)
+		return log.E("codegen", "reading stdin", err)
 	}
 
 	var slots map[string]string
 	if err := json.Unmarshal(data, &slots); err != nil {
-		return fmt.Errorf("codegen: invalid JSON: %w", err)
+		return log.E("codegen", "invalid JSON", err)
 	}
 
 	js, err := codegen.GenerateBundle(slots)
diff --git a/cmd/wasm/register.go b/cmd/wasm/register.go
index 2146dd0..543a178 100644
--- a/cmd/wasm/register.go
+++ b/cmd/wasm/register.go
@@ -4,7 +4,6 @@ package main
 
 import (
 	"encoding/json"
-	"fmt"
 
 	"forge.lthn.ai/core/go-html/codegen"
 	log "forge.lthn.ai/core/go-log"
@@ -17,7 +16,7 @@ import (
 func buildComponentJS(slotsJSON string) (string, error) {
 	var slots map[string]string
 	if err := json.Unmarshal([]byte(slotsJSON), &slots); err != nil {
-		return "", fmt.Errorf("registerComponents: %w", err)
+		return "", log.E("buildComponentJS", "unmarshal JSON", err)
 	}
 	return codegen.GenerateBundle(slots)
 }
diff --git a/cmd/wasm/size_test.go b/cmd/wasm/size_test.go
index 0017485..5552844 100644
--- a/cmd/wasm/size_test.go
+++ b/cmd/wasm/size_test.go
@@ -11,6 +11,7 @@ import (
 	"path/filepath"
 	"testing"
 
+	coreio "forge.lthn.ai/core/go-io"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
@@ -33,8 +34,9 @@ func TestWASMBinarySize_Good(t *testing.T) {
 	output, err := cmd.CombinedOutput()
 	require.NoError(t, err, "WASM build failed: %s", output)
 
-	raw, err := os.ReadFile(out)
+	rawStr, err := coreio.Local.Read(out)
 	require.NoError(t, err)
+	raw := []byte(rawStr)
 
 	var buf bytes.Buffer
 	gz, err := gzip.NewWriterLevel(&buf, gzip.BestCompression)
diff --git a/codegen/codegen.go b/codegen/codegen.go
index 8c443cf..b2e81f5 100644
--- a/codegen/codegen.go
+++ b/codegen/codegen.go
@@ -4,6 +4,8 @@ import (
 	"fmt"
 	"strings"
 	"text/template"
+
+	log "forge.lthn.ai/core/go-log"
 )
 
 // wcTemplate is the Web Component class template.
@@ -31,7 +33,7 @@ var wcTemplate = template.Must(template.New("wc").Parse(`class {{.ClassName}} ex
 // GenerateClass produces a JS class definition for a custom element.
 func GenerateClass(tag, slot string) (string, error) {
 	if !strings.Contains(tag, "-") {
-		return "", fmt.Errorf("codegen: custom element tag %q must contain a hyphen", tag)
+		return "", log.E("codegen.GenerateClass", "custom element tag must contain a hyphen: "+tag, nil)
 	}
 	var b strings.Builder
 	err := wcTemplate.Execute(&b, struct {
@@ -42,7 +44,7 @@ func GenerateClass(tag, slot string) (string, error) {
 		Slot:      slot,
 	})
 	if err != nil {
-		return "", fmt.Errorf("codegen: template exec: %w", err)
+		return "", log.E("codegen.GenerateClass", "template exec", err)
 	}
 	return b.String(), nil
 }
diff --git a/go.mod b/go.mod
index c2b1dae..a345738 100644
--- a/go.mod
+++ b/go.mod
@@ -4,6 +4,7 @@ go 1.26.0
 
 require (
 	forge.lthn.ai/core/go-i18n v0.1.4
+	forge.lthn.ai/core/go-io v0.1.2
 	forge.lthn.ai/core/go-log v0.0.4
 	github.com/stretchr/testify v1.11.1
 )
diff --git a/go.sum b/go.sum
index e71eb4f..7f1f659 100644
--- a/go.sum
+++ b/go.sum
@@ -2,6 +2,8 @@ forge.lthn.ai/core/go-i18n v0.1.4 h1:zOHUUJDgRo88/3tj++kN+VELg/buyZ4T2OSdG3HBbLQ
 forge.lthn.ai/core/go-i18n v0.1.4/go.mod h1:aDyAfz7MMgWYgLkZCptfFmZ7jJg3ocwjEJ1WkJSvv4U=
 forge.lthn.ai/core/go-inference v0.1.4 h1:fuAgWbqsEDajHniqAKyvHYbRcBrkGEiGSqR2pfTMRY0=
 forge.lthn.ai/core/go-inference v0.1.4/go.mod h1:jfWz+IJX55wAH98+ic6FEqqGB6/P31CHlg7VY7pxREw=
+forge.lthn.ai/core/go-io v0.1.2 h1:q8hj2jtOFqAgHlBr5wsUAOXtaFkxy9gqGrQT/il0WYA=
+forge.lthn.ai/core/go-io v0.1.2/go.mod h1:PbNKW1Q25ywSOoQXeGdQHbV5aiIrTXvHIQ5uhplA//g=
 forge.lthn.ai/core/go-log v0.0.4 h1:KTuCEPgFmuM8KJfnyQ8vPOU1Jg654W74h8IJvfQMfv0=
 forge.lthn.ai/core/go-log v0.0.4/go.mod h1:r14MXKOD3LF/sI8XUJQhRk/SZHBE7jAFVuCfgkXoZPw=
 github.com/davecgh/go-spew v1.1.2-0.20180830191138-d8f796af33cc h1:U9qPSI2PIWSS1VwoXQT9A3Wy9MM3WgvqSxFWenqJduM=