diff --git a/cmd/cbconvert-gui/settings.go b/cmd/cbconvert-gui/settings.go
index b1e0254..91377c5 100644
--- a/cmd/cbconvert-gui/settings.go
+++ b/cmd/cbconvert-gui/settings.go
@@ -148,6 +148,8 @@ func settingsApply(group string) {
 		}
 	}
 
+	userLossless = iup.GetHandle("Lossless").GetAttribute("VALUE") == "ON"
+
 	syncLabels()
 	setActive()
 	previewPost()
diff --git a/cmd/cbconvert-gui/state.go b/cmd/cbconvert-gui/state.go
index bd26511..392f618 100644
--- a/cmd/cbconvert-gui/state.go
+++ b/cmd/cbconvert-gui/state.go
@@ -1,10 +1,40 @@
 package main
 
 import (
+	"runtime/debug"
+	"strings"
+
 	"github.com/gen2brain/cbconvert/cmd/cbconvert-gui/i18n"
 	"github.com/gen2brain/iup-go/iup"
 )
 
+// jxlLosslessBuild reports whether wasm2go and nodynamic leave zune-jpegxl (lossless-only) as the only jxl encoder.
+var jxlLosslessBuild = func() bool {
+	info, ok := debug.ReadBuildInfo()
+	if !ok {
+		return false
+	}
+	var wasm2go, nodynamic bool
+	for _, kv := range info.Settings {
+		if kv.Key != "-tags" {
+			continue
+		}
+		for _, t := range strings.Split(kv.Value, ",") {
+			switch t {
+			case "wasm2go":
+				wasm2go = true
+			case "nodynamic":
+				nodynamic = true
+			}
+		}
+	}
+	return wasm2go && nodynamic
+}()
+
+// userLossless is the user's Lossless preference, tracked separately because a jxl
+// wasm2go build force-sets the widget on.
+var userLossless bool
+
 func setActive() {
 	if busy {
 		return
@@ -68,7 +98,15 @@ func setActive() {
 	}
 
 	canLossless := opts.Format == "webp" || opts.Format == "avif" || opts.Format == "jxl"
-	losslessOn := canLossless && opts.Lossless
+	jxlLossless := jxlLosslessBuild && opts.Format == "jxl"
+
+	// jxl wasm2go forces lossless on; otherwise show the user's preference so it doesn't stay stuck on.
+	losslessVal := "OFF"
+	if jxlLossless || userLossless {
+		losslessVal = "ON"
+	}
+	iup.GetHandle("Lossless").SetAttribute("VALUE", losslessVal)
+	losslessOn := jxlLossless || (canLossless && userLossless)
 
 	if (opts.Format == "jpeg" || canLossless) && !opts.NoConvert && !losslessOn {
 		iup.GetHandle("VboxQuality").SetAttribute("ACTIVE", "YES")
@@ -84,6 +122,11 @@ func setActive() {
 		iup.GetHandle("Lossless").SetAttribute("ACTIVE", "NO")
 	}
 
+	if jxlLossless {
+		iup.GetHandle("Lossless").SetAttribute("ACTIVE", "NO")
+		iup.GetHandle("VboxEffort").SetAttribute("ACTIVE", "NO")
+	}
+
 	if opts.Width != 0 && opts.Height != 0 && !opts.NoConvert {
 		iup.GetHandle("Fit").SetAttribute("ACTIVE", "YES")
 	} else {
diff --git a/cmd/cbconvert-gui/widgets.go b/cmd/cbconvert-gui/widgets.go
index 1ade73b..2714cea 100644
--- a/cmd/cbconvert-gui/widgets.go
+++ b/cmd/cbconvert-gui/widgets.go
@@ -60,7 +60,7 @@ func list() iup.Ihandle {
 		"TITLE1":         i18n.Lng(i18n.ColTitle),
 		"TITLE2":         i18n.Lng(i18n.ColType),
 		"TITLE3":         i18n.Lng(i18n.ColSize),
-		"WIDTH1":         "300",
+		"WIDTH1":         "250",
 		"WIDTH2":         "50",
 		"WIDTH3":         "100",
 		"ALIGNMENT2":     "ACENTER",
@@ -568,6 +568,7 @@ func tabImage() iup.Ihandle {
 				iup.Toggle(i18n.Lng(i18n.TglLossless)).SetHandle("Lossless").
 					SetAttribute("TIP", i18n.Lng(i18n.TipLossless)).
 					SetCallback("VALUECHANGED_CB", iup.ValueChangedFunc(func(ih iup.Ihandle) int {
+						userLossless = ih.GetAttribute("VALUE") == "ON"
 						setActive()
 						previewPost()