diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index 630a9d0a..7d6036e7 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -636,6 +636,7 @@ jobs:
       RELEASE_SHA: ${{ needs.validate.outputs.source_sha }}
       RELEASE_VERSION: ${{ needs.validate.outputs.version }}
       NOTES_PATH: ${{ needs.validate.outputs.notes_path }}
+      PYTHONDONTWRITEBYTECODE: '1'
     steps:
       - uses: actions/checkout@11d5960a326750d5838078e36cf38b85af677262 # v4
         with:
diff --git a/scripts/check_release_workflow.py b/scripts/check_release_workflow.py
index f9cdafa8..a69ce11c 100644
--- a/scripts/check_release_workflow.py
+++ b/scripts/check_release_workflow.py
@@ -190,7 +190,7 @@
     "quality": "43599825f68088f3cc744220227267f77454e2c7ce389a52b8aee5a492491eec",
     "macos_arm64": "f913508e4f041614a967f680515cc0b8779800f0b2a7b4b6ff29f24f4bb1efd2",
     "windows_x64": "5f012278c20843ba1b38cffb27f3c614716bd92e3fec63a11885b41692be78b5",
-    "publish": "dd325630c78f236e972ca425ccc83018d12b4ec35a6b8a80d1af94990c8179a2",
+    "publish": "89192ac021d48cc8c8ef17b612a2da666d96c01d195c4e2b58eec24b2cc24d1b",
 }
 
 
@@ -969,6 +969,9 @@ def validate_workflow(workflow: str) -> list[str]:
         return list(dict.fromkeys(errors))
     if publish.get("permissions") != {"contents": "write"}:
         errors.append("publish-only contents write permission")
+    publish_env = _as_mapping(publish.get("env"))
+    if publish_env is None or publish_env.get("PYTHONDONTWRITEBYTECODE") != "1":
+        errors.append("publish Python helpers cannot write bytecode into the checkout")
     initialize_publish = _structured_step(publish, "Initialize isolated publish root")
     download_macos = _structured_step(publish, "Download macOS artifact")
     download_windows = _structured_step(publish, "Download Windows artifact")
diff --git a/scripts/test_check_release_workflow.py b/scripts/test_check_release_workflow.py
index 1beb6184..7c2198f0 100644
--- a/scripts/test_check_release_workflow.py
+++ b/scripts/test_check_release_workflow.py
@@ -334,6 +334,27 @@ def test_publish_outputs_must_stay_outside_the_worktree(self) -> None:
         )
         self.assert_rejected(mutated, "publish outputs stay outside the worktree")
 
+    def test_publish_python_helpers_cannot_write_bytecode_into_checkout(self) -> None:
+        protected_env = "      PYTHONDONTWRITEBYTECODE: '1'\n"
+        if protected_env in WORKFLOW:
+            protected = WORKFLOW
+        else:
+            protected = self.mutate(
+                "      NOTES_PATH: ${{ needs.validate.outputs.notes_path }}\n",
+                "      NOTES_PATH: ${{ needs.validate.outputs.notes_path }}\n"
+                + protected_env,
+            )
+        unprotected = protected.replace(protected_env, "", 1)
+
+        self.assertNotIn(
+            "publish Python helpers cannot write bytecode into the checkout",
+            contract.validate_workflow(protected),
+        )
+        self.assert_rejected(
+            unprotected,
+            "publish Python helpers cannot write bytecode into the checkout",
+        )
+
     def test_macos_package_command_cannot_be_faked_by_an_echo_string(self) -> None:
         original = (
             "        run: >-\n"