diff --git a/build/bazel/go.MODULE.bazel b/build/bazel/go.MODULE.bazel
index f1e10f5..dfa5b91 100644
--- a/build/bazel/go.MODULE.bazel
+++ b/build/bazel/go.MODULE.bazel
@@ -184,6 +184,10 @@
         ],
     },
     "github.com/bytecodealliance/wasmtime-go/v14": {
+        # wasmtime brings its own BUILD files and for some reason,
+        # Bazel regenerates them in the nixos/nix container but not on
+        # NixOS. We disable replacing the existing directives to fix this.
+        "build_file_generation": "off",
         "directives": [
             "gazelle:go_naming_convention go_default_library",
         ],
diff --git a/build/bazel/toolchain.MODULE.bazel b/build/bazel/toolchain.MODULE.bazel
index f0434f5..f691078 100644
--- a/build/bazel/toolchain.MODULE.bazel
+++ b/build/bazel/toolchain.MODULE.bazel
@@ -3,17 +3,17 @@
 http_archive(
     name = "toolchain-bundle-x86_64-unknown-linux-musl",
     build_file = "//build/toolchain/toolchain-bundle:toolchain-bundle.bzl",
-    integrity = "sha256-tpbvNL5S4t2WLkcj027sghf8tEzVJFL1e5leyx8JkCI=",
+    integrity = "sha256-7wceZhsWdZLXT2KW05NmmbUCYKA+DmudjPqTO3qX29I=",
     urls = [
-        "https://storage.googleapis.com/monogon-infra-public/toolchain/toolchain-bundle-x86_64-unknown-linux-musl-release-25.05.ffdcefdde9a4e540d1c875767da0e382e1ccf460.tar.zst",
+        "https://storage.googleapis.com/monogon-infra-public/toolchain/9iv889bzlsg1dglkmqdnabak5ffbp2km-toolchain/toolchain-bundle-x86_64-unknown-linux-musl.tar.zst",
     ],
 )
 
 http_archive(
     name = "toolchain-bundle-aarch64-unknown-linux-musl",
     build_file = "//build/toolchain/toolchain-bundle:toolchain-bundle.bzl",
-    integrity = "sha256-6caDQ8S+DGXHy2xSAhfRu5EXFLZ7NNqbtkY6o1i33F4=",
+    integrity = "sha256-7ckBNZ5186xDDsDlsUVMNIciY9nECfH70KoB/FUZKRc=",
     urls = [
-        "https://storage.googleapis.com/monogon-infra-public/toolchain/toolchain-bundle-aarch64-unknown-linux-musl-release-25.05.ffdcefdde9a4e540d1c875767da0e382e1ccf460.tar.zst",
+        "https://storage.googleapis.com/monogon-infra-public/toolchain/9iv889bzlsg1dglkmqdnabak5ffbp2km-toolchain/toolchain-bundle-aarch64-unknown-linux-musl.tar.zst",
     ],
 )
diff --git a/build/toolchain/toolchain-bundle/BUILD.bazel b/build/toolchain/toolchain-bundle/BUILD.bazel
index 82437da..66de9f5 100644
--- a/build/toolchain/toolchain-bundle/BUILD.bazel
+++ b/build/toolchain/toolchain-bundle/BUILD.bazel
@@ -1,4 +1,7 @@
 load("@rules_perl//perl:toolchain.bzl", "perl_toolchain")
+load("@rules_python//python:py_exec_tools_toolchain.bzl", "py_exec_tools_toolchain")
+load("@rules_python//python:py_runtime.bzl", "py_runtime")
+load("@rules_python//python:py_runtime_pair.bzl", "py_runtime_pair")
 load(":toolchain.bzl", "SUPPORTED_TARGETS", "TOOLCHAINS", "toolchain_for")
 
 package(default_visibility = ["//visibility:public"])
@@ -11,6 +14,42 @@
     for name, config in TOOLCHAINS.items()
 ]
 
+[
+    [
+        py_runtime(
+            name = "rules_python_%s_python3_12_runtime" % target.tuple,
+            interpreter = "@toolchain-bundle-%s//:python3.12" % target.triple,
+            interpreter_version_info = {
+                "major": str(3),
+                "minor": str(12),
+                "micro": str(0),
+            },
+            python_version = "PY3",
+        ),
+        py_runtime_pair(
+            name = "rules_python_%s_python3_12_runtime_pair" % target.tuple,
+            py3_runtime = ":rules_python_%s_python3_12_runtime" % target.tuple,
+        ),
+        py_exec_tools_toolchain(
+            name = "rules_python_%s_python3_12_exec_tools_toolchain_impl" % target.tuple,
+            exec_interpreter = ":rules_python_%s_python3_12_runtime_pair" % target.tuple,
+        ),
+        toolchain(
+            name = "rules_python_%s_python3_12_runtime_toolchain" % target.tuple,
+            exec_compatible_with = target.constrain,
+            toolchain = ":rules_python_%s_python3_12_runtime_pair" % target.tuple,
+            toolchain_type = "@rules_python//python:toolchain_type",
+        ),
+        toolchain(
+            name = "rules_python_%s_python3_12_exec_tools_toolchain" % target.tuple,
+            exec_compatible_with = target.constrain,
+            toolchain = ":rules_python_%s_python3_12_exec_tools_toolchain_impl" % target.tuple,
+            toolchain_type = "@rules_python//python:exec_tools_toolchain_type",
+        ),
+    ]
+    for target in SUPPORTED_TARGETS
+]
+
 # rules_perl wiring
 
 [
diff --git a/build/toolchain/toolchain-bundle/toolchain-bundle.bzl b/build/toolchain/toolchain-bundle/toolchain-bundle.bzl
index 6ac17fb..c2de9d1 100644
--- a/build/toolchain/toolchain-bundle/toolchain-bundle.bzl
+++ b/build/toolchain/toolchain-bundle/toolchain-bundle.bzl
@@ -4,6 +4,32 @@
     "**/*",
 ]))
 
+filegroup(
+    name = "python3.12",
+    srcs = [
+        ":bin/python3.12",
+    ],
+    data = glob([
+        "lib/python3.12/**",
+    ]),
+)
+
+filegroup(
+    name = "python3.12_headers",
+    srcs = glob([
+        "include/python3.12/**",
+    ]),
+)
+
+filegroup(
+    name = "python3.12_libs",
+    srcs = glob([
+        "lib/python3.12/**",
+    ]) + [
+        ":lib/libpython3.12.a",
+    ],
+)
+
 # rules_perl expects all files as src entry, this does prevent us using
 # $(execpath) which is why we have another filegroup that uses this as
 # data dep.