diff --git a/.prettierignore b/.prettierignore
index 07db0c7a..33f36e19 100644
--- a/.prettierignore
+++ b/.prettierignore
@@ -4,6 +4,14 @@ pnpm-lock.yaml
 **/node_modules
 **/drizzle
 **/.next
+# Python build/test artifacts — same category as node_modules/dist/.next above.
+# Prettier must never scan generated trees; without these a local venv poisons
+# `pnpm format:check` with thousands of third-party files.
+**/venv
+**/__pycache__
+**/.mypy_cache
+**/.pytest_cache
+**/htmlcov
 .claude/
 docs/tess/TASKS.md
 docs/scratchpads/