diff --git a/plugin-designs/plugin-studio/plugin-studio.vue b/plugin-designs/plugin-studio/plugin-studio.vue
index 80c34bf33..5dcd8acbb 100644
--- a/plugin-designs/plugin-studio/plugin-studio.vue
+++ b/plugin-designs/plugin-studio/plugin-studio.vue
@@ -52,6 +52,7 @@
        panes with their direct-element mount + heavy-row teardown machinery. -->
   <VerticalTabsLayout
     :title="heading || tr('title')"
+    :dir="uiDir"
     :nav-label="tr('navLabel')"
     :labels="{ toggleList: tr('toggleList'), openViews: tr('openViews'), expandList: tr('expandList'), collapseList: tr('collapseList'), collapse: tr('collapse') }"
     :header="true"
@@ -547,7 +548,11 @@ export default defineComponent({
       const nb = new Set(this.rows.map(r => r.bundle)).size
       return this.tr('countLabel', { bundles: nb, elements: this.rows.length })
     },
-    activeLang() { return getLanguage(this.locale) || { code: this.locale, flag: '🌐', nativeName: this.locale } }
+    activeLang() { return getLanguage(this.locale) || { code: this.locale, flag: '🌐', nativeName: this.locale } },
+    // Right-to-left for a right-to-left language (languages.js marks Arabic dir:'rtl'), which is what
+    // switches on VerticalTabsLayout's :dir(rtl) mirror — rega's 5e7f73d0, which doxa-maps-spa turns on
+    // the same way. Without this the mirror compiled into the studio but never applied.
+    uiDir() { return (this.activeLang && this.activeLang.dir) === 'rtl' ? 'rtl' : 'ltr' }
   },
   mounted() {
     this.loadManifest()
diff --git a/plugin-designs/plugin-studio/src/StudioTree.vue b/plugin-designs/plugin-studio/src/StudioTree.vue
index 46c66b4e7..ead63c0c7 100644
--- a/plugin-designs/plugin-studio/src/StudioTree.vue
+++ b/plugin-designs/plugin-studio/src/StudioTree.vue
@@ -106,11 +106,11 @@ const ST_CSS = '' +
   '.st-tool:hover { background:#f3f3f1; color:#3b463d; } .st-tool:focus-visible { outline:2px solid #92b195; outline-offset:-2px; }' +
   '.st-tool svg { width:16px; height:16px; }' +
   '.st-tree { display:flex; flex-direction:column; padding:0 0 8px; outline:0; }' +
-  '.st-row { position:relative; display:flex; align-items:center; gap:6px; height:28px; box-sizing:border-box; padding:0 10px 0 calc(8px + var(--st-depth) * 14px); font-size:13px; color:#3b463d; cursor:pointer; white-space:nowrap; user-select:none; outline:0; }' +
+  '.st-row { position:relative; display:flex; align-items:center; gap:6px; height:28px; box-sizing:border-box; padding-block:0; padding-inline:calc(8px + var(--st-depth) * 14px) 10px; font-size:13px; color:#3b463d; cursor:pointer; white-space:nowrap; user-select:none; outline:0; }' +
   '.st-row:hover { background:#f3f3f1; }' +
   '.st-row:focus-visible { box-shadow:inset 0 0 0 1px #92b195; }' +
   '.st-row.active { background:rgba(146,177,149,.24); }' +
-  '.st-row.active::after { content:""; position:absolute; left:0; top:4px; bottom:4px; width:3px; border-radius:0 3px 3px 0; background:#92b195; }' +
+  '.st-row.active::after { content:""; position:absolute; inset-inline-start:0; top:4px; bottom:4px; width:3px; border-start-end-radius:3px; border-end-end-radius:3px; background:#92b195; }' +
   '.st-row.alias.active { background:rgba(146,177,149,.12); }' +
   '.st-sec { position:sticky; top:46px; z-index:2; height:30px; margin-top:6px; background:#ffffff; font-size:11px; font-weight:600; letter-spacing:.06em; text-transform:uppercase; color:#6d766e; border-top:1px solid #eceee9; }' +
   '.st-sec:first-child { margin-top:0; border-top:0; }' +
@@ -120,6 +120,7 @@ const ST_CSS = '' +
   '.st-twisty, .st-twisty-sp { flex:0 0 16px; width:16px; height:16px; display:inline-flex; align-items:center; justify-content:center; color:#6d766e; }' +
   '.st-twisty svg { width:14px; height:14px; transition:transform .12s ease; }' +
   '.st-row[aria-expanded="true"] > .st-twisty svg { transform:rotate(90deg); }' +
+  '.st:dir(rtl) .st-twisty svg { transform:scaleX(-1); } .st:dir(rtl) .st-row[aria-expanded="true"] > .st-twisty svg { transform:rotate(90deg); }' +
   '.st-ic { flex:0 0 16px; display:inline-flex; color:#6d766e; } .st-ic svg { width:16px; height:16px; }' +
   '.st-row.active .st-ic { color:#5f8a63; }' +
   '.st-label { flex:0 1 auto; min-width:0; overflow:hidden; text-overflow:ellipsis; }' +
@@ -127,12 +128,12 @@ const ST_CSS = '' +
   // ellipsised to make room for the tag (VS Code truncates the description first, too).
   '.st-desc { flex:1 1 0; min-width:0; overflow:hidden; text-overflow:ellipsis; font:11px/1 ui-monospace,Menlo,monospace; color:#8a928b; }' +
   '.st-part { flex:0 0 auto; font:600 9px/1 system-ui,sans-serif; text-transform:uppercase; letter-spacing:.3px; padding:2px 4px; border:1px solid #92b195; border-radius:4px; color:#5f8a63; }' +
-  '.st-count { flex:0 0 auto; margin-left:auto; min-width:18px; text-align:right; font-size:11px; font-weight:500; letter-spacing:0; color:#6d766e; }' +
-  '.st-guide { position:absolute; top:0; bottom:0; left:calc(15px + var(--st-g) * 14px); border-left:1px solid #dfe2db; pointer-events:none; }' +
-  '.st-row:hover > .st-guide { border-left-color:#c4c8c0; }' +
+  '.st-count { flex:0 0 auto; margin-inline-start:auto; min-width:18px; text-align:right; font-size:11px; font-weight:500; letter-spacing:0; color:#6d766e; }' +
+  '.st-guide { position:absolute; top:0; bottom:0; inset-inline-start:calc(15px + var(--st-g) * 14px); border-inline-start:1px solid #dfe2db; pointer-events:none; }' +
+  '.st-row:hover > .st-guide { border-inline-start-color:#c4c8c0; }' +
   '.st-empty { margin:12px; font-size:13px; color:#6d766e; }' +
   '.st-activity { display:flex; flex-direction:column; gap:4px; }' +
-  '.st-act { position:relative; display:flex; align-items:center; justify-content:center; width:48px; height:44px; margin-left:172px; padding:0; border:0; border-radius:10px; background:none; color:#6d766e; cursor:pointer; }' +
+  '.st-act { position:relative; display:flex; align-items:center; justify-content:center; width:48px; height:44px; margin-inline-start:172px; padding:0; border:0; border-radius:10px; background:none; color:#6d766e; cursor:pointer; }' +
   '.st-act:hover, .st-act.active { background:#f3f3f1; color:#3b463d; }' +
   '.st-act:focus-visible { outline:2px solid #92b195; outline-offset:-2px; }' +
   '.st-act-ic { display:inline-flex; } .st-act-ic svg { width:20px; height:20px; }' +
@@ -352,11 +353,11 @@ export default defineComponent({
 .st-tool:hover { background:#f3f3f1; color:#3b463d; } .st-tool:focus-visible { outline:2px solid #92b195; outline-offset:-2px; }
 .st-tool svg { width:16px; height:16px; }
 .st-tree { display:flex; flex-direction:column; padding:0 0 8px; outline:0; }
-.st-row { position:relative; display:flex; align-items:center; gap:6px; height:28px; box-sizing:border-box; padding:0 10px 0 calc(8px + var(--st-depth) * 14px); font-size:13px; color:#3b463d; cursor:pointer; white-space:nowrap; user-select:none; outline:0; }
+.st-row { position:relative; display:flex; align-items:center; gap:6px; height:28px; box-sizing:border-box; padding-block:0; padding-inline:calc(8px + var(--st-depth) * 14px) 10px; font-size:13px; color:#3b463d; cursor:pointer; white-space:nowrap; user-select:none; outline:0; }
 .st-row:hover { background:#f3f3f1; }
 .st-row:focus-visible { box-shadow:inset 0 0 0 1px #92b195; }
 .st-row.active { background:rgba(146,177,149,.24); }
-.st-row.active::after { content:""; position:absolute; left:0; top:4px; bottom:4px; width:3px; border-radius:0 3px 3px 0; background:#92b195; }
+.st-row.active::after { content:""; position:absolute; inset-inline-start:0; top:4px; bottom:4px; width:3px; border-start-end-radius:3px; border-end-end-radius:3px; background:#92b195; }
 .st-row.alias.active { background:rgba(146,177,149,.12); }
 .st-sec { position:sticky; top:46px; z-index:2; height:30px; margin-top:6px; background:#ffffff; font-size:11px; font-weight:600; letter-spacing:.06em; text-transform:uppercase; color:#6d766e; border-top:1px solid #eceee9; }
 .st-sec:first-child { margin-top:0; border-top:0; }
@@ -366,17 +367,18 @@ export default defineComponent({
 .st-twisty, .st-twisty-sp { flex:0 0 16px; width:16px; height:16px; display:inline-flex; align-items:center; justify-content:center; color:#6d766e; }
 .st-twisty svg { width:14px; height:14px; transition:transform .12s ease; }
 .st-row[aria-expanded="true"] > .st-twisty svg { transform:rotate(90deg); }
+.st:dir(rtl) .st-twisty svg { transform:scaleX(-1); } .st:dir(rtl) .st-row[aria-expanded="true"] > .st-twisty svg { transform:rotate(90deg); }
 .st-ic { flex:0 0 16px; display:inline-flex; color:#6d766e; } .st-ic svg { width:16px; height:16px; }
 .st-row.active .st-ic { color:#5f8a63; }
 .st-label { flex:0 1 auto; min-width:0; overflow:hidden; text-overflow:ellipsis; }
 .st-desc { flex:1 1 0; min-width:0; overflow:hidden; text-overflow:ellipsis; font:11px/1 ui-monospace,Menlo,monospace; color:#8a928b; }
 .st-part { flex:0 0 auto; font:600 9px/1 system-ui,sans-serif; text-transform:uppercase; letter-spacing:.3px; padding:2px 4px; border:1px solid #92b195; border-radius:4px; color:#5f8a63; }
-.st-count { flex:0 0 auto; margin-left:auto; min-width:18px; text-align:right; font-size:11px; font-weight:500; letter-spacing:0; color:#6d766e; }
-.st-guide { position:absolute; top:0; bottom:0; left:calc(15px + var(--st-g) * 14px); border-left:1px solid #dfe2db; pointer-events:none; }
-.st-row:hover > .st-guide { border-left-color:#c4c8c0; }
+.st-count { flex:0 0 auto; margin-inline-start:auto; min-width:18px; text-align:right; font-size:11px; font-weight:500; letter-spacing:0; color:#6d766e; }
+.st-guide { position:absolute; top:0; bottom:0; inset-inline-start:calc(15px + var(--st-g) * 14px); border-inline-start:1px solid #dfe2db; pointer-events:none; }
+.st-row:hover > .st-guide { border-inline-start-color:#c4c8c0; }
 .st-empty { margin:12px; font-size:13px; color:#6d766e; }
 .st-activity { display:flex; flex-direction:column; gap:4px; }
-.st-act { position:relative; display:flex; align-items:center; justify-content:center; width:48px; height:44px; margin-left:172px; padding:0; border:0; border-radius:10px; background:none; color:#6d766e; cursor:pointer; }
+.st-act { position:relative; display:flex; align-items:center; justify-content:center; width:48px; height:44px; margin-inline-start:172px; padding:0; border:0; border-radius:10px; background:none; color:#6d766e; cursor:pointer; }
 .st-act:hover, .st-act.active { background:#f3f3f1; color:#3b463d; }
 .st-act:focus-visible { outline:2px solid #92b195; outline-offset:-2px; }
 .st-act-ic { display:inline-flex; } .st-act-ic svg { width:20px; height:20px; }