diff --git a/plain-code/plain/code/oxc.py b/plain-code/plain/code/oxc.py
index 9e284bdb78..35d8d33f17 100644
--- a/plain-code/plain/code/oxc.py
+++ b/plain-code/plain/code/oxc.py
@@ -192,7 +192,16 @@ def download(self, version: str = "") -> str:
                         dst.write(extracted.read())
 
             os.chmod(tmp_path, 0o755)
-            os.replace(tmp_path, binary_path)
+            try:
+                os.replace(tmp_path, binary_path)
+            except PermissionError:
+                # Windows raises this if another process has binary_path open
+                # (e.g. another checkout sharing this machine-wide cache is
+                # currently running it). If it's already there, another
+                # process finished installing this exact version — nothing
+                # left to do.
+                if not binary_path.exists():
+                    raise
         finally:
             tmp_path.unlink(missing_ok=True)
 
diff --git a/plain-tailwind/plain/tailwind/core.py b/plain-tailwind/plain/tailwind/core.py
index 1958267a79..ab0af401cd 100644
--- a/plain-tailwind/plain/tailwind/core.py
+++ b/plain-tailwind/plain/tailwind/core.py
@@ -170,7 +170,16 @@ def download(self, version: str = "") -> str:
 
             binary_path = self.binary_path(version)
             binary_path.parent.mkdir(parents=True, exist_ok=True)
-            os.replace(tmp_path, binary_path)
+            try:
+                os.replace(tmp_path, binary_path)
+            except PermissionError:
+                # Windows raises this if another process has binary_path open
+                # (e.g. `plain tailwind build --watch` in a different checkout
+                # sharing this machine-wide cache). If it's already there,
+                # another process finished installing this exact version —
+                # nothing left to do.
+                if not binary_path.exists():
+                    raise
         finally:
             tmp_path.unlink(missing_ok=True)