diff --git a/apps/web/src/components/BranchToolbar.tsx b/apps/web/src/components/BranchToolbar.tsx
index 8a4dc581992325a5f17c86468d567a88bcb51cf5..b0b1440587ea40379402116c08009b814b7e4e89 100644
--- a/apps/web/src/components/BranchToolbar.tsx
+++ b/apps/web/src/components/BranchToolbar.tsx
@@ -265,8 +265,10 @@ function useLabelsOverflow(element: HTMLDivElement | null): boolean {
     let needed = 0;
     let groups = 0;
     for (const child of current.children) {
-      if (!(child instanceof HTMLElement) || child.offsetWidth <= 1) continue;
-      needed += contentWidth(child);
+      if (!(child instanceof HTMLElement)) continue;
+      const width = contentWidth(child);
+      if (width <= 1) continue;
+      needed += width;
       groups += 1;
     }
     needed += stripGap * Math.max(0, groups - 1);
@@ -356,7 +358,7 @@ function useLabelsOverflow(element: HTMLDivElement | null): boolean {
   // Label widths can change without the strip box moving (font family or
   // size preferences), so re-measure on every render as well as on resize
   // and font loads.
-  useEffect(() => {
+  useLayoutEffect(() => {
     measure();
   });
 
@@ -487,7 +489,7 @@ export const BranchToolbar = memo(function BranchToolbar({
           onUsePreviousWorktree={onUsePreviousWorktree}
         />
       ) : (
-        <div className="flex min-w-0 flex-1 items-center gap-1">
+        <div className="flex min-w-10 flex-1 items-center gap-1">
           {showEnvironmentIndicator && availableEnvironments && (
             <>
               <BranchToolbarEnvironmentSelector
@@ -520,7 +522,7 @@ export const BranchToolbar = memo(function BranchToolbar({
 
       {showGitControls ? (
         <BranchToolbarBranchSelector
-          className="min-w-0 flex-1 justify-end md:ml-auto md:flex-none"
+          className="min-w-0 flex-1 justify-end md:ml-auto md:flex-initial"
           environmentId={environmentId}
           threadId={threadId}
           {...(draftId ? { draftId } : {})}
diff --git a/apps/web/src/components/BranchToolbarEnvModeSelector.tsx b/apps/web/src/components/BranchToolbarEnvModeSelector.tsx
index 9fc2d4892e27727bcc66c3ed7b2caa1bb8abba88..23589d62bd954bde06597ea0ec369f30371dbfb2 100644
--- a/apps/web/src/components/BranchToolbarEnvModeSelector.tsx
+++ b/apps/web/src/components/BranchToolbarEnvModeSelector.tsx
@@ -51,20 +51,25 @@ export const BranchToolbarEnvModeSelector = memo(function BranchToolbarEnvModeSe
   if (envLocked) {
     return (
       <span
-        className="inline-flex h-7 shrink-0 items-center gap-1 border border-transparent px-[calc(--spacing(3)-1px)] text-sm font-medium text-muted-foreground/70 sm:h-6 sm:text-xs"
+        className="inline-flex h-7 min-w-0 items-center gap-1 border border-transparent px-[calc(--spacing(3)-1px)] text-sm font-medium text-muted-foreground/70 sm:h-6 sm:text-xs"
         data-composer-context-control
       >
         {activeWorktreePath ? (
-          <>
-            <FolderGitIcon className="size-3" />
-            {resolveLockedWorkspaceLabel(activeWorktreePath)}
-          </>
+          <FolderGitIcon className="size-3 shrink-0" />
         ) : (
-          <>
-            <FolderIcon className="size-3" />
-            {resolveLockedWorkspaceLabel(activeWorktreePath)}
-          </>
+          <FolderIcon className="size-3 shrink-0" />
         )}
+        <span
+          data-composer-label
+          className="min-w-0 max-w-[240px] group-data-[compact]/composer-context:max-w-0"
+        >
+          <span
+            data-composer-label-motion
+            className="block w-full min-w-0 max-w-[240px] origin-left truncate transition-[opacity,transform] duration-180 ease-[cubic-bezier(0.32,0.72,0,1)] group-data-[compact]/composer-context:[transform:translateX(-0.25rem)_scaleX(0.95)] group-data-[compact]/composer-context:opacity-0 motion-reduce:transform-none motion-reduce:transition-opacity"
+          >
+            {resolveLockedWorkspaceLabel(activeWorktreePath)}
+          </span>
+        </span>
       </span>
     );
   }
diff --git a/apps/web/src/components/chat/ChatHeader.tsx b/apps/web/src/components/chat/ChatHeader.tsx
index dbba327489ac17e69d67924a524596d0042b44a2..c9c733e10f19ab295934784d6122b0bbfd1562f4 100644
--- a/apps/web/src/components/chat/ChatHeader.tsx
+++ b/apps/web/src/components/chat/ChatHeader.tsx
@@ -288,13 +288,16 @@ export const ChatHeader = memo(function ChatHeader({
       className="@container/header-actions flex min-w-0 flex-1 items-center gap-2 sm:gap-3"
       onContextMenu={handleHeaderContextMenu}
     >
-      <WorkspaceBreadcrumb ariaLabel="Thread breadcrumb" className="flex-1">
+      <WorkspaceBreadcrumb
+        ariaLabel="Thread breadcrumb"
+        className="flex-1 overflow-clip [overflow-clip-margin:2px]"
+      >
         {/* The project always leads the header: knowing which project a
             thread lives in is priority zero, and the thread title alone
             doesn't answer it. */}
         {activeProjectName ? (
           <>
-            <WorkspaceBreadcrumbItem>
+            <WorkspaceBreadcrumbItem className="shrink">
               <Tooltip>
                 <TooltipTrigger
                   render={
@@ -302,7 +305,7 @@ export const ChatHeader = memo(function ChatHeader({
                       type="button"
                       aria-label={`New thread in ${activeProjectName}`}
                       onClick={onNewThreadInProject}
-                      className="inline-flex min-w-0 cursor-pointer items-center gap-1.5 rounded-sm text-muted-foreground transition-colors hover:text-foreground focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-ring"
+                      className="inline-flex min-w-0 max-w-full cursor-pointer items-center gap-1.5 rounded-sm text-muted-foreground transition-colors hover:text-foreground focus-visible:outline-hidden focus-visible:ring-2 focus-visible:ring-ring"
                     />
                   }
                 >
@@ -320,7 +323,7 @@ export const ChatHeader = memo(function ChatHeader({
             <WorkspaceBreadcrumbSeparator />
           </>
         ) : null}
-        <WorkspaceBreadcrumbItem current className="flex-1">
+        <WorkspaceBreadcrumbItem current className="min-w-10 flex-1">
           {renamingTitle !== null ? (
             <input
               autoFocus