diff --git a/tools/robostack.py b/tools/robostack.py
index c8eccf1a..cc45e86a 100644
--- a/tools/robostack.py
+++ b/tools/robostack.py
@@ -114,11 +114,7 @@ def run_tee(cmd: list[str], cwd: Path) -> tuple[int, bytes]:
 
 # a build job's recipes side by side, with a shared jobserver keeping them at the runner's
 # cores in total; Windows has no jobserver, and was no faster with two (#154)
-# Temporarily one at a time everywhere: rattler-build 0.77 gives two variants of a recipe
-# started in the same second the same build directory, and they fail ("Path ... already
-# exists", prefix-dev/rattler-build#2898, e.g. beluga's hdf5 variants). Back to
-# f"3:{os.cpu_count()}" off Windows once prefix-dev/rattler-build#2899 is released.
-PARALLEL_BUILDS = "1"
+PARALLEL_BUILDS = "1" if sys.platform == "win32" else f"3:{os.cpu_count()}"
 
 
 def build_ci_parallel(distro: str, recipes: list[str], args: list[str], cwd: Path) -> int: