diff --git a/src/App.tsx b/src/App.tsx
index 4f6374d..276bd4b 100644
--- a/src/App.tsx
+++ b/src/App.tsx
@@ -1265,14 +1265,18 @@ export default function App() {
         case "spawn_pane": {
           const a = args as { spec?: SpawnSpec };
           const summary = a.spec ? `Spawn ${describeSpec(a.spec)} pane` : "Spawn pane";
-          const ssh =
-            a.spec && a.spec.kind === "ssh"
-              ? {
-                  hostLabel: a.spec.hostId
-                    ? hosts.find((h) => h.id === a.spec!.hostId)?.label ?? a.spec.host
-                    : a.spec.host,
-                }
-              : undefined;
+          // Bind the narrowed SSH variant to a local so the closure inside
+          // hosts.find() doesn't lose the discriminant. Using a.spec! here
+          // would compile under tsc --noEmit but fail under tsc -b.
+          let ssh: { hostLabel: string } | undefined;
+          if (a.spec && a.spec.kind === "ssh") {
+            const sshSpec = a.spec;
+            ssh = {
+              hostLabel: sshSpec.hostId
+                ? hosts.find((h) => h.id === sshSpec.hostId)?.label ?? sshSpec.host
+                : sshSpec.host,
+            };
+          }
           return { summary, ssh };
         }
         case "connect_host": {