From b93d19b873d2c6000fa0b4af9869c8234e62653a Mon Sep 17 00:00:00 2001
From: "mr. m" <91018726+mr-cheffy@users.noreply.github.com>
Date: Tue, 25 Aug 2026 22:05:54 +0200
Subject: [PATCH] gh-15088: Fixed syncing essentials with different containers
 (gh-15105)

---
 src/zen/sessionstore/ZenWindowSync.sys.mjs | 4 +++-
 src/zen/sync/ZenSpacesSyncApplier.sys.mjs  | 4 ++--
 src/zen/tabs/ZenPinnedTabManager.mjs       | 8 ++++++--
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/src/zen/sessionstore/ZenWindowSync.sys.mjs b/src/zen/sessionstore/ZenWindowSync.sys.mjs
index 51816e88b..f19316ab4 100644
--- a/src/zen/sessionstore/ZenWindowSync.sys.mjs
+++ b/src/zen/sessionstore/ZenWindowSync.sys.mjs
@@ -606,7 +606,9 @@ class nsZenWindowSync {
     if (isTab) {
       if (originalIsEssential !== targetIsEssential) {
         if (originalIsEssential) {
-          gZenPinnedTabManager.addToEssentials(aTargetItem);
+          gZenPinnedTabManager.addToEssentials(aTargetItem, {
+            replicating: true,
+          });
         } else {
           gZenPinnedTabManager.removeEssentials(
             aTargetItem,
diff --git a/src/zen/sync/ZenSpacesSyncApplier.sys.mjs b/src/zen/sync/ZenSpacesSyncApplier.sys.mjs
index 16a171734..b75e22a95 100644
--- a/src/zen/sync/ZenSpacesSyncApplier.sys.mjs
+++ b/src/zen/sync/ZenSpacesSyncApplier.sys.mjs
@@ -498,7 +498,7 @@ class nsZenSpacesSyncApplier {
     tab._zenContentsVisible = true;
     this.#updateTabIdentity(win, tab, data);
     if (data.essential) {
-      win.gZenPinnedTabManager.addToEssentials(tab);
+      win.gZenPinnedTabManager.addToEssentials(tab, { replicating: true });
     } else {
       if (data.workspaceUuid) {
         tab.setAttribute("zen-workspace-id", data.workspaceUuid);
@@ -658,7 +658,7 @@ class nsZenSpacesSyncApplier {
 
     const isEssential = tab.hasAttribute("zen-essential");
     if (data.essential && !isEssential) {
-      win.gZenPinnedTabManager.addToEssentials(tab);
+      win.gZenPinnedTabManager.addToEssentials(tab, { replicating: true });
       return;
     }
     if (!data.essential && isEssential) {
diff --git a/src/zen/tabs/ZenPinnedTabManager.mjs b/src/zen/tabs/ZenPinnedTabManager.mjs
index 7f4c48cf5..3364a100a 100644
--- a/src/zen/tabs/ZenPinnedTabManager.mjs
+++ b/src/zen/tabs/ZenPinnedTabManager.mjs
@@ -503,7 +503,7 @@ class nsZenPinnedTabManager extends nsZenDOMOperatedFeature {
     }
   }
 
-  addToEssentials(tab) {
+  addToEssentials(tab, { replicating = false } = {}) {
     // eslint-disable-next-line no-nested-ternary
     const tabs = tab
       ? // if it's already an array, dont make it [tab]
@@ -518,7 +518,11 @@ class nsZenPinnedTabManager extends nsZenDOMOperatedFeature {
       // eslint-disable-next-line no-shadow
       let tab = tabs[i];
       const section = gZenWorkspaces.getEssentialsSection(tab);
-      if (!this.canEssentialBeAdded(tab)) {
+      // canEssentialBeAdded gates user-initiated adds on the *active* space's
+      // container. A replicated add mirrors a decision already made in another
+      // window or on another device, always into the tab's own container
+      // section.
+      if (!replicating && !this.canEssentialBeAdded(tab)) {
         movedAll = false;
         continue;
       }