diff --git a/nix/checked-candidate.nix b/nix/checked-candidate.nix
index 5af96c9..5033091 100644
--- a/nix/checked-candidate.nix
+++ b/nix/checked-candidate.nix
@@ -407,12 +407,19 @@ pkgs.runCommand (if contractOnly then "qx-contract" else "qx-checked-candidate")
       ${pkgs.nodejs_24}/bin/node ${./check-execution.mjs} \
         ${protocol}/libexec/quixos-protocol/execution-world.mjs \
         "$out/execution-plan.json" "$out/checks.json" "$out"
-      mkdir -p "$out/bin"
-      cat > "$out/bin/run-isolated" <<EOF
-      #!${pkgs.runtimeShell}
-      exec ${runtimePackages.camino-isolated-workspace}/bin/camino-isolated-workspace "$out" "\$@"
-      EOF
-      chmod +x "$out/bin/run-isolated"
+      # The optional development host is acquired only when explicitly run.
+      # Embedding its executable here made every source check build Web Studio
+      # and a full host even when only checked Package outputs were consumed.
+      cp ${
+        pkgs.writeText "qx-isolated-runtime.json" (
+          builtins.toJSON {
+            codec = "quixos-isolated-runtime/1";
+            source = {
+              inherit (root.lock.quixos) repository commit;
+            };
+          }
+        )
+      } "$out/isolated-runtime.json"
     ''}
   ''}
   ${pkgs.lib.optionalString (