diff --git a/src/bundled/agents/AgentsPage.test.tsx b/src/bundled/agents/AgentsPage.test.tsx
index d1f5f21a5a..cb29da7b90 100644
--- a/src/bundled/agents/AgentsPage.test.tsx
+++ b/src/bundled/agents/AgentsPage.test.tsx
@@ -2504,6 +2504,27 @@ it("offers New team again when the team being edited disappears", async () => {
   expect(screen.getByRole("button", { name: "New team" })).toBeInTheDocument();
 });
 
+it("explains an unavailable harness without claiming the key is on another device", async () => {
+  const user = userEvent.setup();
+  setup([
+    {
+      ...agent("Starf", 3),
+      type: "block.builderlab/builderlab",
+      place: "elsewhere",
+    },
+  ]);
+  const grid = screen.getByRole("grid", { name: "Agents" });
+  expect(within(grid).getByText("Harness unavailable")).toBeInTheDocument();
+  expect(screen.queryByText("On another device")).not.toBeInTheDocument();
+
+  await user.click(within(grid).getByText("Starf"));
+  expect(screen.getByText(/Check Settings → Plugins/)).toBeInTheDocument();
+  expect(screen.queryByText(/another of your devices/)).not.toBeInTheDocument();
+  expect(
+    screen.queryByRole("button", { name: "Delete agent" }),
+  ).not.toBeInTheDocument();
+});
+
 it("shows an agent on another device read-only, and offers only Finish setup and Delete for an unfinished hosted one", async () => {
   const user = userEvent.setup();
   const far: Agent = {
diff --git a/src/bundled/agents/AgentsPage.tsx b/src/bundled/agents/AgentsPage.tsx
index 3aec0afb28..1575648112 100644
--- a/src/bundled/agents/AgentsPage.tsx
+++ b/src/bundled/agents/AgentsPage.tsx
@@ -120,7 +120,8 @@ const importReminderKey = "agent-community-import:dismissed";
 
 /** The type's one-line summary of an agent; its title when it has none. */
 function summaryOf(agent: Agent, type: RegisteredAgentType | undefined) {
-  if (agent.place === "elsewhere") return "On another device";
+  if (agent.place === "elsewhere")
+    return type && !type.remote ? "On another device" : "Harness unavailable";
   if (agent.unfinished) return "Setup unfinished";
   if (!type) return "Type unavailable";
   try {
@@ -1186,8 +1187,17 @@ function AgentPeek({
       />
       {agent.place === "elsewhere" ? (
         <p className="m-0 text-body-sm text-secondary">
-          Its key is on another of your devices, which runs it. Open Agents
-          there to change or delete it.
+          {type && !type.remote ? (
+            <>
+              Its key is on another of your devices, which runs it. Open Agents
+              there to change or delete it.
+            </>
+          ) : (
+            <>
+              This agent’s harness is unavailable in this client. Check Settings
+              → Plugins or use a build with this harness configured.
+            </>
+          )}
         </p>
       ) : (
         <>