diff --git a/src/kiri/mode/cam/op-area.js b/src/kiri/mode/cam/op-area.js
index 20b7df99..e02d81d7 100644
--- a/src/kiri/mode/cam/op-area.js
+++ b/src/kiri/mode/cam/op-area.js
@@ -37,8 +37,8 @@ class OpArea extends CamOp {
         let smoothVal = (smooth ?? 0) / 10;
         let toolDiam = areaTool.fluteDiameter();
         let toolOver = areaTool.getStepSize(over);
-        let zTop = ov_topz ? workarea.bottom_stock + ov_topz : workarea.top_z;
-        let zBottom = ov_botz ? workarea.bottom_stock + ov_botz : Math.max(workarea.bottom_z, workarea.bottom_part) + workarea.bottom_cut;
+        let zTop = workarea.top_z;
+        let zBottom = Math.max(workarea.bottom_z, workarea.bottom_part) + workarea.bottom_cut;
         let shadowBase = state.shadow.base;
         let thruHoles = state.shadow.holes;
 
@@ -181,7 +181,7 @@ class OpArea extends CamOp {
                         outs = omitInner(outs);
                     }
                     // add tabs to travel boundaries
-                    if (tabs) {
+                    if (tabs.length) {
                         let tab_shadows = tabs.filter(t => t.top >= z).map(t => t.poly);
                         if (tab_shadows) tool_shadow.push(...tab_shadows);
                     }
@@ -244,7 +244,7 @@ class OpArea extends CamOp {
                     // add dogbones when specified
                     if (op.dogbones) outs.forEach(out => out.addDogbones(toolDiam / 5, op.revbones));
                     // cut tabs when present
-                    if (tabs) outs = cutTabs(tabs, outs);
+                    if (tabs.length) outs = cutTabs(tabs, outs);
                     // support legacy outline features
                     if (op.omitouter) {
                         outs = omitOuter(outs);
diff --git a/src/kiri/mode/cam/slice.js b/src/kiri/mode/cam/slice.js
index efae5041..5a181643 100644
--- a/src/kiri/mode/cam/slice.js
+++ b/src/kiri/mode/cam/slice.js
@@ -21,7 +21,28 @@ import { util } from '../../../geo/base.js';
 export async function cam_slice(settings, widget, onupdate, ondone) {
     if (widget.track.synth) return ondone();
 
+    // get tab widgets
     let tabW = widget.group.filter(w => w != widget);
+    // merge overlapping tabs
+    for (let i=0; i<tabW.length; i++) {
+        for (let j=i+1; j<tabW.length; j++) {
+            let t1 = tabW[i];
+            let t2 = tabW[j];
+            let b1 = t1.mesh.getBoundingBox();
+            let b2 = t2.mesh.getBoundingBox();
+            if (b1.intersectsBox(b2)) {
+                let a = t1.getVertices().array;
+                let b = t2.getVertices().array;
+                let arr = new Float32Array(a.length + b.length);
+                arr.set(a, 0);
+                arr.set(b, a.length);
+                t1.loadVertices(arr);
+                t2.del = true;
+            }
+        }
+    }
+    // filter merged tabs
+    tabW = tabW.filter(tw => !tw.del);
 
     let proc = settings.process,
         camOps = widget.camops = [],
@@ -41,7 +62,7 @@ export async function cam_slice(settings, widget, onupdate, ondone) {
     color = dark ? 0xbbbbbb : 0;
     minToolDiam = Infinity;
     maxToolDiam = -Infinity;
-    tabs = widget.anno.tab;
+    tabs = widget.anno.tab ?? [];
     unsafe = proc.camExpertFast;
     units = settings.controller.units === 'in' ? 25.4 : 1;