diff --git a/clients/web/src/components/views/InspectorView/InspectorView.test.tsx b/clients/web/src/components/views/InspectorView/InspectorView.test.tsx
index 4b1f999a..18e1be16 100644
--- a/clients/web/src/components/views/InspectorView/InspectorView.test.tsx
+++ b/clients/web/src/components/views/InspectorView/InspectorView.test.tsx
@@ -920,6 +920,76 @@ describe("InspectorView", () => {
     ).toBeInTheDocument();
   });
 
+  it("dims the other server cards while a connection is live", () => {
+    const betaServer: ServerEntry = {
+      id: "beta",
+      name: "Beta",
+      config: { type: "stdio", command: "echo" },
+      connection: { status: "disconnected" },
+    };
+    renderWithMantine(
+      <InspectorView
+        {...makeProps({
+          servers: [sampleServer, betaServer],
+          activeServer: "alpha",
+          connectionStatus: "connected",
+          initializeResult: connectedInit,
+        })}
+      />,
+    );
+    // The non-active card is inert while alpha holds a live session, so the
+    // user can't start a second connection mid-session.
+    const betaCard = screen.getByText("Beta").closest(".mantine-Card-root");
+    expect(betaCard?.getAttribute("aria-disabled")).toBe("true");
+  });
+
+  it("re-enables the other server cards when the active connection goes to error (#1521)", () => {
+    const betaServer: ServerEntry = {
+      id: "beta",
+      name: "Beta",
+      config: { type: "stdio", command: "echo" },
+      connection: { status: "disconnected" },
+    };
+    // Live session on alpha → beta starts out dimmed/inert.
+    const { rerender } = renderWithMantine(
+      <InspectorView
+        {...makeProps({
+          servers: [sampleServer, betaServer],
+          activeServer: "alpha",
+          connectionStatus: "connected",
+          initializeResult: connectedInit,
+        })}
+      />,
+    );
+    expect(
+      screen
+        .getByText("Beta")
+        .closest(".mantine-Card-root")
+        ?.getAttribute("aria-disabled"),
+    ).toBe("true");
+
+    // alpha's connection errors. App does NOT clear `activeServer` here — a
+    // terminal `error` fires no InspectorClient `disconnect` event — so the
+    // id still points at alpha. The other cards must re-enable anyway; only a
+    // *live* session should dim them.
+    rerender(
+      <InspectorView
+        {...makeProps({
+          servers: [sampleServer, betaServer],
+          activeServer: "alpha",
+          connectionStatus: "error",
+          initializeResult: undefined,
+        })}
+      />,
+    );
+    expect(
+      screen
+        .getByText("Beta")
+        .closest(".mantine-Card-root")
+        ?.getAttribute("aria-disabled"),
+    ).toBeNull();
+  });
+
   describe("listChanged indicator wiring (#1402)", () => {
     // The indicator only mounts on the active screen, so each case connects,
     // navigates to the target tab, and asserts the "List updated" affordance.
diff --git a/clients/web/src/components/views/InspectorView/InspectorView.tsx b/clients/web/src/components/views/InspectorView/InspectorView.tsx
index 3ed89b6b..98195c54 100644
--- a/clients/web/src/components/views/InspectorView/InspectorView.tsx
+++ b/clients/web/src/components/views/InspectorView/InspectorView.tsx
@@ -18,6 +18,7 @@ import type {
   MessageEntry,
   ServerEntry,
 } from "@inspector/core/mcp/types.js";
+import { isTerminalStatus } from "@inspector/core/mcp/types.js";
 import { isAppTool } from "@inspector/core/mcp/apps.js";
 import { ViewHeader } from "../../groups/ViewHeader/ViewHeader";
 import { ServerListScreen } from "../../screens/ServerListScreen/ServerListScreen";
@@ -576,6 +577,24 @@ export function InspectorView({
     [serversInput, activeServer, connectionStatus, initializeResult],
   );
 
+  // The other server cards are dimmed/`inert` only while a connection is
+  // actively live (connecting or connected), so the user can't kick off a
+  // second connection mid-session. Once the active session settles into a
+  // terminal state — `disconnected` or `error` — the rest must re-enable
+  // (#1521). A connect-time handshake failure (and a mid-session transport
+  // `onerror`) resolves to `error` *without* firing the InspectorClient
+  // `disconnect` event that App uses to clear `activeServerId`, so the id
+  // lingers; gating the dim source on liveness here is what un-dims the
+  // others. The errored card itself still shows its real status via the
+  // merged `servers` list above (keyed off the real `activeServer`), so
+  // passing `undefined` here lifts only the *other* cards' dimming, not the
+  // error indicator on the active one. `isTerminalStatus` (the #1490 teardown
+  // convention) is the single source of truth for "session is over" so this
+  // gate can't silently desync from a future status addition.
+  const dimCardsAgainst = isTerminalStatus(connectionStatus)
+    ? undefined
+    : activeServer;
+
   return (
     // padding={0}: each screen fills `calc(100dvh - header)` and supplies its
     // own `xl` padding, so Main must contribute only the fixed-header offset.
@@ -612,7 +631,7 @@ export function InspectorView({
             <ServerListScreen
               servers={servers}
               writable={serverListWritable}
-              activeServer={activeServer}
+              activeServer={dimCardsAgainst}
               onAddManually={onServerAdd}
               onImportConfig={onServerImportConfig}
               onImportServerJson={onServerImportJson}