diff --git a/news/python-ext-os-arch-dependent.fixed.md b/news/python-ext-os-arch-dependent.fixed.md
new file mode 100644
index 0000000000..ea17098e84
--- /dev/null
+++ b/news/python-ext-os-arch-dependent.fixed.md
@@ -0,0 +1,3 @@
+(toolchains) The `python` extension is re-evaluated when the host OS or CPU
+changes, so an output base shared between hosts no longer fails to fetch the
+`*_host` interpreter repo.
diff --git a/python/private/python.bzl b/python/private/python.bzl
index 05334c3da1..19db885e57 100644
--- a/python/private/python.bzl
+++ b/python/private/python.bzl
@@ -1624,6 +1624,8 @@ python = module_extension(
         "toolchain": _toolchain,
     },
     environ = ["RULES_PYTHON_BZLMOD_DEBUG"],
+    os_dependent = True,
+    arch_dependent = True,
 )
 
 _DEBUG_BUILD_CONTENT = """