diff --git a/browser/themes/shared/tabbrowser/tabs.css b/browser/themes/shared/tabbrowser/tabs.css
index 5b9ad123d819c6ef068acd427416957a1d0939fe..311caa27ee268c95215d459be02a93d20e129f8b 100644
--- a/browser/themes/shared/tabbrowser/tabs.css
+++ b/browser/themes/shared/tabbrowser/tabs.css
@@ -33,7 +33,7 @@
   --tab-block-margin: 4px;
   --tab-icon-end-margin: 5.5px;
   --tab-label-line-height: 1.7;
-  --tab-loading-fill: #0A84FF;
+  --tab-loading-fill: var(--zen-primary-color);
   --tab-hover-background-color: color-mix(in srgb, currentColor 11%, transparent);
   --tab-selected-textcolor: var(--toolbar-color);
   --tab-selected-bgcolor: var(--toolbar-bgcolor);
@@ -211,8 +211,7 @@
   }
 
   #tabbrowser-tabs[positionpinnedtabs] > #tabbrowser-arrowscrollbox > &[pinned] {
-    position: absolute !important;
-    display: block;
+
   }
 
   #tabbrowser-tabs[movingtab] &:is(:active, [multiselected]) {
@@ -258,7 +257,6 @@
   }
 
   :root:not([uidensity=compact], [sidebar-expand-on-hover]) &[pinned] {
-    padding: 0 10px;
   }
 
   &:is([selected], [multiselected]) {
@@ -272,6 +270,7 @@
     border-radius: inherit;
     position: relative;
     overflow: hidden;
+    display: none;
 
     &::before {
       position: absolute;
@@ -459,14 +458,11 @@
 .tab-icon-image {
   -moz-context-properties: fill, stroke;
   fill: currentColor;
+  border-radius: 4px;
 
   /* stylelint-disable-next-line media-query-no-invalid */
   @media -moz-pref("browser.tabs.fadeOutUnloadedTabs") {
     &[pending] {
-      filter: grayscale(100%);
-      @media (prefers-color-scheme: dark) {
-        filter: grayscale(100%) invert();
-      }
       opacity: 0.5;
       /* Fade the favicon out */
       transition-property: filter, opacity;
@@ -483,10 +479,6 @@
   /* stylelint-disable-next-line media-query-no-invalid */
   @media -moz-pref("browser.tabs.fadeOutExplicitlyUnloadedTabs") {
     &[pending][discarded] {
-      filter: grayscale(100%);
-      @media (prefers-color-scheme: dark) {
-        filter: grayscale(100%) invert();
-      }
       opacity: 0.5;
       /* Fade the favicon out */
       transition-property: filter, opacity;
@@ -559,7 +551,7 @@
   z-index: 1; /* Overlay tab title */
 
   #tabbrowser-tabs[orient=vertical] & {
-    top: 7px;
+    top: -7px;
   }
 
   &[crashed] {
@@ -567,7 +559,7 @@
   }
 
   #tabbrowser-tabs[orient="vertical"]:not([expanded]) &:not([crashed]),
-  &[pinned]:not([crashed]) {
+  &:not([crashed]) {
     &[soundplaying] {
       list-style-image: url("chrome://browser/skin/tabbrowser/tab-audio-playing-small.svg");
     }
@@ -597,7 +589,7 @@
       background-image: linear-gradient(var(--audio-overlay-extra-background)),
                         linear-gradient(var(--toolbox-bgcolor));
       -moz-context-properties: fill;
-      fill: var(--tab-selected-textcolor);
+      fill: var(--tab-selected-textcolor) !important;
       color-scheme: var(--tab-selected-color-scheme);
       border-radius: var(--border-radius-circle);
 
@@ -1365,7 +1357,7 @@ tab-group {
   }
 }
 
-#tabbrowser-arrowscrollbox[orient="vertical"] > #tabbrowser-arrowscrollbox-periphery > #tabs-newtab-button,
+#tabbrowser-arrowscrollbox[orient="vertical"] #tabbrowser-arrowscrollbox-periphery > #tabs-newtab-button,
 #vertical-tabs-newtab-button {
   appearance: none;
   min-height: var(--tab-min-height);
@@ -1376,7 +1368,7 @@ tab-group {
   margin-inline: var(--tab-inner-inline-margin);
 
   #tabbrowser-tabs[orient="vertical"]:not([expanded]) & > .toolbarbutton-text {
-    display: none;
+    display: flex;
   }
 
   &:hover {
@@ -1400,7 +1392,7 @@ tab-group {
  * flex container. #tabs-newtab-button is a child of the arrowscrollbox where
  * we don't want a gap (between tabs), so we have to add some margin.
  */
-#tabbrowser-arrowscrollbox[orient="vertical"] > #tabbrowser-arrowscrollbox-periphery > #tabs-newtab-button {
+#tabbrowser-arrowscrollbox[orient="vertical"] #tabbrowser-arrowscrollbox-periphery > #tabs-newtab-button {
   margin-block: var(--tab-block-margin);
 }
 
@@ -1474,8 +1466,6 @@ tab-group {
   }
 
   :root:not([sidebar-expand-on-hover]) & {
-    --tab-inline-padding: calc((var(--tab-collapsed-background-width) + 2 *
-      var(--tab-pinned-margin-inline-expanded) - var(--icon-size-default)) / 2);
     /* stylelint-disable-next-line media-query-no-invalid */
     @media not -moz-pref("sidebar.visibility", "expand-on-hover") {
       /* We need these rules to apply at all times when the sidebar.visibility
@@ -1585,7 +1575,6 @@ tab-group {
 
   &:not([expanded]) {
     .tabbrowser-tab[pinned] {
-      width: var(--tab-collapsed-width);
     }
 
     .tab-background {
@@ -1716,7 +1705,7 @@ tab-group {
   toolbarbutton:not(#firefox-view-button),
   toolbarpaletteitem:not(#wrapper-firefox-view-button)
 ) ~ #tabbrowser-tabs {
-  border-inline-start: var(--tabstrip-inner-border);
+  border-inline-start: transparent;
   padding-inline-start: calc(var(--tab-overflow-pinned-tabs-width) + 2px);
   margin-inline-start: 2px;
 }
@@ -1750,7 +1739,6 @@ toolbar:not(#TabsToolbar) #firefox-view-button {
   list-style-image: url(chrome://global/skin/icons/plus.svg);
 }
 
-#tabbrowser-tabs[hasadjacentnewtabbutton]:not([overflow]) ~ #new-tab-button,
 #tabbrowser-tabs[orient="horizontal"] > #vertical-tabs-newtab-button,
 #tabbrowser-tabs[orient="vertical"]:not([overflow]) > #vertical-tabs-newtab-button,
 #tabbrowser-arrowscrollbox[overflowing] > #tabbrowser-arrowscrollbox-periphery > #tabs-newtab-button,