diff --git a/apps/web/src/components/BranchToolbar.tsx b/apps/web/src/components/BranchToolbar.tsx
index 95c7351b09..f2ba1d3db3 100644
--- a/apps/web/src/components/BranchToolbar.tsx
+++ b/apps/web/src/components/BranchToolbar.tsx
@@ -186,29 +186,58 @@ const MobileRunContextSelector = memo(function MobileRunContextSelector({
 
   if (isLocked) {
     return (
-      <span
-        className="inline-flex h-7 min-w-0 max-w-[48%] flex-initial items-center justify-start gap-1 rounded-md border border-transparent px-[calc(--spacing(2)-1px)] font-normal text-muted-foreground/70 text-xs sm:h-6"
-        data-composer-context-control
-      >
-        {triggerContent}
-      </span>
+      <Tooltip>
+        <TooltipTrigger
+          render={<span tabIndex={0} />}
+          className="inline-flex h-7 min-w-0 max-w-[48%] flex-initial items-center justify-start gap-1 rounded-md border border-transparent px-[calc(--spacing(2)-1px)] font-normal text-muted-foreground/70 text-xs sm:h-6"
+          data-composer-context-control
+          aria-label={
+            showEnvironmentIndicator
+              ? `Run on ${autoEnvironmentLabel ?? activeEnvironment?.label ?? "Run on"}; Workspace ${workspaceLabel}`
+              : `Workspace ${workspaceLabel}`
+          }
+        >
+          {triggerContent}
+        </TooltipTrigger>
+        <TooltipPopup>
+          {showEnvironmentIndicator
+            ? `${autoEnvironmentLabel ?? activeEnvironment?.label ?? "Run on"} · ${workspaceLabel}`
+            : workspaceLabel}
+        </TooltipPopup>
+      </Tooltip>
     );
   }
 
   return (
     <Menu>
-      <MenuTrigger
-        render={<Button variant="ghost" size="xs" />}
-        className="min-w-0 max-w-[48%] flex-initial justify-start font-normal text-muted-foreground/70 text-xs! hover:text-foreground/80"
-        data-composer-context-control
-        data-composer-shortcut={[
-          showEnvironmentPicker && !envLocked ? "composer.host" : "",
-          !envModeLocked ? "composer.workspace" : "",
-        ].join(" ")}
-      >
-        {triggerContent}
-        <ChevronDownIcon className="size-3 shrink-0 opacity-50" />
-      </MenuTrigger>
+      <Tooltip>
+        <TooltipTrigger
+          render={
+            <MenuTrigger
+              render={<Button variant="ghost" size="xs" />}
+              className="min-w-0 max-w-[48%] flex-initial justify-start font-normal text-muted-foreground/70 text-xs! hover:text-foreground/80"
+              data-composer-context-control
+              aria-label={
+                showEnvironmentIndicator
+                  ? `Run on ${autoEnvironmentLabel ?? activeEnvironment?.label ?? "Run on"}; Workspace ${workspaceLabel}`
+                  : `Workspace ${workspaceLabel}`
+              }
+              data-composer-shortcut={[
+                showEnvironmentPicker && !envLocked ? "composer.host" : "",
+                !envModeLocked ? "composer.workspace" : "",
+              ].join(" ")}
+            />
+          }
+        >
+          {triggerContent}
+          <ChevronDownIcon className="size-3 shrink-0 opacity-50" />
+        </TooltipTrigger>
+        <TooltipPopup>
+          {showEnvironmentIndicator
+            ? `${autoEnvironmentLabel ?? activeEnvironment?.label ?? "Run on"} · ${workspaceLabel}`
+            : workspaceLabel}
+        </TooltipPopup>
+      </Tooltip>
       <MenuPopup align="start" side="top" className="w-64" {...composerFloatingLayerProps}>
         {showEnvironmentPicker && availableEnvironments && onEnvironmentChange ? (
           <>
diff --git a/apps/web/src/components/BranchToolbarContextTooltips.test.tsx b/apps/web/src/components/BranchToolbarContextTooltips.test.tsx
new file mode 100644
index 0000000000..2d1505288c
--- /dev/null
+++ b/apps/web/src/components/BranchToolbarContextTooltips.test.tsx
@@ -0,0 +1,39 @@
+import { EnvironmentId, ProjectId } from "@t3tools/contracts";
+import { renderToStaticMarkup } from "react-dom/server";
+import { describe, expect, it } from "vite-plus/test";
+
+import { BranchToolbarEnvironmentSelector } from "./BranchToolbarEnvironmentSelector";
+import { BranchToolbarEnvModeSelector } from "./BranchToolbarEnvModeSelector";
+
+describe("locked composer context labels", () => {
+  it("keeps clipped environment and workspace labels keyboard reachable", () => {
+    const environment = renderToStaticMarkup(
+      <BranchToolbarEnvironmentSelector
+        envLocked
+        environmentId={EnvironmentId.make("remote")}
+        availableEnvironments={[
+          {
+            environmentId: EnvironmentId.make("remote"),
+            projectId: ProjectId.make("project"),
+            label: "Remote build host",
+            machine: "server",
+            isPrimary: false,
+          },
+        ]}
+      />,
+    );
+    const workspace = renderToStaticMarkup(
+      <BranchToolbarEnvModeSelector
+        envLocked
+        effectiveEnvMode="local"
+        activeWorktreePath="/projects/pylon/worktrees/task"
+        onEnvModeChange={() => {}}
+      />,
+    );
+
+    expect(environment).toContain('tabindex="0"');
+    expect(environment).toContain('aria-label="Run on Remote build host"');
+    expect(workspace).toContain('tabindex="0"');
+    expect(workspace).toContain('aria-label="Workspace');
+  });
+});
diff --git a/apps/web/src/components/BranchToolbarEnvModeSelector.tsx b/apps/web/src/components/BranchToolbarEnvModeSelector.tsx
index a350931fbf..b39089d705 100644
--- a/apps/web/src/components/BranchToolbarEnvModeSelector.tsx
+++ b/apps/web/src/components/BranchToolbarEnvModeSelector.tsx
@@ -17,6 +17,7 @@ import {
   SelectTrigger,
   SelectValue,
 } from "./ui/select";
+import { Tooltip, TooltipPopup, TooltipTrigger } from "./ui/tooltip";
 
 const PREVIOUS_WORKTREE_SELECT_VALUE = "previous-worktree";
 
@@ -51,27 +52,36 @@ export const BranchToolbarEnvModeSelector = memo(function BranchToolbarEnvModeSe
 
   if (envLocked) {
     return (
-      <span
-        className="inline-flex h-7 min-w-0 items-center gap-1 border border-transparent px-[calc(--spacing(2)-1px)] font-normal text-muted-foreground/70 text-xs sm:h-6"
-        data-composer-context-control
-      >
-        {activeWorktreePath ? (
-          <FolderGitIcon className="size-3 shrink-0" />
-        ) : (
-          <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"
+      <Tooltip>
+        <TooltipTrigger
+          render={
+            <span
+              tabIndex={0}
+              aria-label={`Workspace ${resolveLockedWorkspaceLabel(activeWorktreePath)}`}
+            />
+          }
+          className="inline-flex h-7 min-w-0 items-center gap-1 border border-transparent px-[calc(--spacing(2)-1px)] font-normal text-muted-foreground/70 text-xs sm:h-6"
+          data-composer-context-control
         >
+          {activeWorktreePath ? (
+            <FolderGitIcon className="size-3 shrink-0" />
+          ) : (
+            <FolderIcon className="size-3 shrink-0" />
+          )}
           <span
-            data-composer-label-motion
-            className="block w-full min-w-0 max-w-[240px] truncate transition-opacity duration-180 ease-[cubic-bezier(0.32,0.72,0,1)] group-data-[compact]/composer-context:opacity-0 motion-reduce:transition-none"
+            data-composer-label
+            className="min-w-0 max-w-[240px] group-data-[compact]/composer-context:max-w-0"
           >
-            {resolveLockedWorkspaceLabel(activeWorktreePath)}
+            <span
+              data-composer-label-motion
+              className="block w-full min-w-0 max-w-[240px] truncate transition-opacity duration-180 ease-[cubic-bezier(0.32,0.72,0,1)] group-data-[compact]/composer-context:opacity-0 motion-reduce:transition-none"
+            >
+              {resolveLockedWorkspaceLabel(activeWorktreePath)}
+            </span>
           </span>
-        </span>
-      </span>
+        </TooltipTrigger>
+        <TooltipPopup>{resolveLockedWorkspaceLabel(activeWorktreePath)}</TooltipPopup>
+      </Tooltip>
     );
   }
 
@@ -88,33 +98,49 @@ export const BranchToolbarEnvModeSelector = memo(function BranchToolbarEnvModeSe
       }}
       items={envModeItems}
     >
-      <SelectTrigger
-        variant="ghost"
-        size="xs"
-        className="min-w-0 shrink font-normal text-xs!"
-        aria-label="Workspace"
-        data-composer-shortcut="composer.workspace"
-        data-composer-context-control
-      >
-        {effectiveEnvMode === "worktree" ? (
-          <FolderGit2Icon className="size-3" />
-        ) : activeWorktreePath ? (
-          <FolderGitIcon className="size-3" />
-        ) : (
-          <FolderIcon className="size-3" />
-        )}
-        <span
-          data-composer-label
-          className="min-w-0 max-w-[240px] group-data-[compact]/composer-context:max-w-0"
+      <Tooltip>
+        <TooltipTrigger
+          render={
+            <SelectTrigger
+              variant="ghost"
+              size="xs"
+              className="min-w-0 shrink font-normal text-xs!"
+              aria-label="Workspace"
+              aria-description={
+                effectiveEnvMode === "worktree"
+                  ? resolveEnvModeLabel("worktree")
+                  : resolveCurrentWorkspaceLabel(activeWorktreePath)
+              }
+              data-composer-shortcut="composer.workspace"
+              data-composer-context-control
+            />
+          }
         >
+          {effectiveEnvMode === "worktree" ? (
+            <FolderGit2Icon className="size-3" />
+          ) : activeWorktreePath ? (
+            <FolderGitIcon className="size-3" />
+          ) : (
+            <FolderIcon className="size-3" />
+          )}
           <span
-            data-composer-label-motion
-            className="block w-full min-w-0 max-w-[240px] truncate transition-opacity duration-180 ease-[cubic-bezier(0.32,0.72,0,1)] group-data-[compact]/composer-context:opacity-0 motion-reduce:transition-none"
+            data-composer-label
+            className="min-w-0 max-w-[240px] group-data-[compact]/composer-context:max-w-0"
           >
-            <SelectValue />
+            <span
+              data-composer-label-motion
+              className="block w-full min-w-0 max-w-[240px] truncate transition-opacity duration-180 ease-[cubic-bezier(0.32,0.72,0,1)] group-data-[compact]/composer-context:opacity-0 motion-reduce:transition-none"
+            >
+              <SelectValue />
+            </span>
           </span>
-        </span>
-      </SelectTrigger>
+        </TooltipTrigger>
+        <TooltipPopup>
+          {effectiveEnvMode === "worktree"
+            ? resolveEnvModeLabel("worktree")
+            : resolveCurrentWorkspaceLabel(activeWorktreePath)}
+        </TooltipPopup>
+      </Tooltip>
       <SelectPopup alignItemWithTrigger={false} {...composerFloatingLayerProps}>
         <SelectGroup>
           <SelectGroupLabel>Workspace</SelectGroupLabel>
diff --git a/apps/web/src/components/BranchToolbarEnvironmentSelector.tsx b/apps/web/src/components/BranchToolbarEnvironmentSelector.tsx
index e18948310b..de4e4da9cc 100644
--- a/apps/web/src/components/BranchToolbarEnvironmentSelector.tsx
+++ b/apps/web/src/components/BranchToolbarEnvironmentSelector.tsx
@@ -14,6 +14,7 @@ import {
   SelectTrigger,
   SelectValue,
 } from "./ui/select";
+import { Tooltip, TooltipPopup, TooltipTrigger } from "./ui/tooltip";
 
 interface BranchToolbarEnvironmentSelectorProps {
   autoEnvironmentLabel?: string | undefined;
@@ -58,26 +59,32 @@ export const BranchToolbarEnvironmentSelector = memo(function BranchToolbarEnvir
   // only thing in the strip.
   if (envLocked || onEnvironmentChange === undefined) {
     return (
-      <span
-        className="inline-flex h-7 min-w-0 max-w-full items-center gap-1 border border-transparent px-[calc(--spacing(2)-1px)] font-normal text-muted-foreground/70 text-xs sm:h-6"
-        data-composer-context-control
-      >
-        <EnvironmentMachineIcon
-          kind={activeEnvironment?.machine ?? "server"}
-          className="size-3 shrink-0"
-        />
-        <span
-          data-composer-label
-          className="min-w-0 max-w-[240px] group-data-[compact]/composer-context:max-w-0"
+      <Tooltip>
+        <TooltipTrigger
+          render={
+            <span tabIndex={0} aria-label={`Run on ${activeEnvironment?.label ?? "Run on"}`} />
+          }
+          className="inline-flex h-7 min-w-0 max-w-full items-center gap-1 border border-transparent px-[calc(--spacing(2)-1px)] font-normal text-muted-foreground/70 text-xs sm:h-6"
+          data-composer-context-control
         >
+          <EnvironmentMachineIcon
+            kind={activeEnvironment?.machine ?? "server"}
+            className="size-3 shrink-0"
+          />
           <span
-            data-composer-label-motion
-            className="block w-full min-w-0 max-w-[240px] truncate transition-opacity duration-180 ease-[cubic-bezier(0.32,0.72,0,1)] group-data-[compact]/composer-context:opacity-0 motion-reduce:transition-none"
+            data-composer-label
+            className="min-w-0 max-w-[240px] group-data-[compact]/composer-context:max-w-0"
           >
-            {activeEnvironment?.label ?? "Run on"}
+            <span
+              data-composer-label-motion
+              className="block w-full min-w-0 max-w-[240px] truncate transition-opacity duration-180 ease-[cubic-bezier(0.32,0.72,0,1)] group-data-[compact]/composer-context:opacity-0 motion-reduce:transition-none"
+            >
+              {activeEnvironment?.label ?? "Run on"}
+            </span>
           </span>
-        </span>
-      </span>
+        </TooltipTrigger>
+        <TooltipPopup>{activeEnvironment?.label ?? "Run on"}</TooltipPopup>
+      </Tooltip>
     );
   }
 
@@ -90,34 +97,42 @@ export const BranchToolbarEnvironmentSelector = memo(function BranchToolbarEnvir
       }
       items={environmentItems}
     >
-      <SelectTrigger
-        variant="ghost"
-        size="xs"
-        className="min-w-0 max-w-full font-normal text-xs!"
-        aria-label="Run on"
-        data-composer-shortcut="composer.host"
-        data-composer-context-control
-      >
-        {autoEnvironmentLabel ? (
-          <ScaleIcon className="size-3 shrink-0" aria-hidden="true" />
-        ) : (
-          <EnvironmentMachineIcon
-            kind={activeEnvironment?.machine ?? "server"}
-            className="size-3 shrink-0"
-          />
-        )}
-        <span
-          data-composer-label
-          className="min-w-0 max-w-[240px] group-data-[compact]/composer-context:max-w-0"
+      <Tooltip>
+        <TooltipTrigger
+          render={
+            <SelectTrigger
+              variant="ghost"
+              size="xs"
+              className="min-w-0 max-w-full font-normal text-xs!"
+              aria-label="Run on"
+              aria-description={autoEnvironmentLabel ?? activeEnvironment?.label ?? "Run on"}
+              data-composer-shortcut="composer.host"
+              data-composer-context-control
+            />
+          }
         >
+          {autoEnvironmentLabel ? (
+            <ScaleIcon className="size-3 shrink-0" aria-hidden="true" />
+          ) : (
+            <EnvironmentMachineIcon
+              kind={activeEnvironment?.machine ?? "server"}
+              className="size-3 shrink-0"
+            />
+          )}
           <span
-            data-composer-label-motion
-            className="block w-full min-w-0 max-w-[240px] truncate transition-opacity duration-180 ease-[cubic-bezier(0.32,0.72,0,1)] group-data-[compact]/composer-context:opacity-0 motion-reduce:transition-none"
+            data-composer-label
+            className="min-w-0 max-w-[240px] group-data-[compact]/composer-context:max-w-0"
           >
-            <SelectValue />
+            <span
+              data-composer-label-motion
+              className="block w-full min-w-0 max-w-[240px] truncate transition-opacity duration-180 ease-[cubic-bezier(0.32,0.72,0,1)] group-data-[compact]/composer-context:opacity-0 motion-reduce:transition-none"
+            >
+              <SelectValue />
+            </span>
           </span>
-        </span>
-      </SelectTrigger>
+        </TooltipTrigger>
+        <TooltipPopup>{autoEnvironmentLabel ?? activeEnvironment?.label ?? "Run on"}</TooltipPopup>
+      </Tooltip>
       <SelectPopup alignItemWithTrigger={false} {...composerFloatingLayerProps}>
         <SelectGroup>
           <SelectGroupLabel>Run on</SelectGroupLabel>