diff --git a/.gitignore b/.gitignore
index 2b76d7c..b97fd73 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,6 +6,26 @@ Thumbs.db
 # hyf
 .hyf/score.json
 
+# Python virtual environments
+.venv/
+venv/
+env/
+ENV/
+
+# Python bytecode and caches
+__pycache__/
+*.pyc
+*.pyo
+*.pyd
+.pytest_cache/
+.ruff_cache/
+.mypy_cache/
+
+# Python build / dist artifacts
+*.egg-info/
+build/
+dist/
+
 # Editor and IDE settings
 .vscode/
 .idea/
diff --git a/.hyf/grader_lib.sh b/.hyf/grader_lib.sh
index 1871010..bed5074 100755
--- a/.hyf/grader_lib.sh
+++ b/.hyf/grader_lib.sh
@@ -101,7 +101,7 @@ check_gitignore_python() {
   # Warns when Python cache patterns are absent from .gitignore.
   local gi="${1:-.gitignore}"
   if [[ ! -f "$gi" ]]; then
-    warn ".gitignore is missing — add one so __pycache__/ and *.pyc are not committed"
+    warn ".gitignore is missing — add one so __pycache__/, *.pyc, and .venv/ are not committed"
     return 0
   fi
   local ok=true
@@ -117,7 +117,54 @@ check_gitignore_python() {
     warn ".gitignore missing .env — secret files should not be committed"
     ok=false
   fi
-  if [[ "$ok" = true ]]; then pass ".gitignore correctly excludes __pycache__/, *.pyc, and .env"; fi
+  # Either .venv/ or venv/ must be excluded (the two common conventions).
+  if ! grep -qE "^\.?venv/?$" "$gi"; then
+    warn ".gitignore missing .venv/ (or venv/) — virtual environment folder must not be committed"
+    ok=false
+  fi
+  if [[ "$ok" = true ]]; then pass ".gitignore correctly excludes __pycache__/, *.pyc, .env, and .venv/"; fi
+  return 0
+}
+
+check_no_venv_committed() {
+  # Usage: check_no_venv_committed
+  # Fails when a virtual-environment folder is tracked by git. The venv is a
+  # per-machine artefact: committing it bloats the repo, leaks local paths,
+  # and breaks the moment a teammate on another OS clones the repo.
+  # Detection prefers `git ls-files` (only flags tracked entries); falls back
+  # to a filesystem check when git is unavailable.
+  local found=""
+  if command -v git &>/dev/null && git rev-parse --is-inside-work-tree &>/dev/null; then
+    found=$(git ls-files | grep -E "^(\.venv|venv|env|ENV)/" | head -3 || true)
+  else
+    for d in .venv venv env ENV; do
+      [[ -d "$d" ]] && found="$d/"
+    done
+  fi
+  if [[ -n "$found" ]]; then
+    fail "virtual environment folder is committed — add .venv/ to .gitignore and 'git rm -r --cached .venv' to remove it from history. Tracked entries:
+    ${found}"
+  else
+    pass "no virtual environment folder committed"
+  fi
+  return 0
+}
+
+check_lockfile_present() {
+  # Usage: check_lockfile_present
+  # Warns when neither requirements.txt nor uv.lock nor pyproject.toml exists
+  # at the repo root. The lockfile is the *recipe* a fresh venv needs to
+  # reproduce the student's environment — without it CI cannot install
+  # whatever the student's code imports.
+  if [[ -f requirements.txt ]] || [[ -f uv.lock ]] || [[ -f pyproject.toml ]]; then
+    local seen=()
+    [[ -f requirements.txt ]] && seen+=("requirements.txt")
+    [[ -f uv.lock ]]          && seen+=("uv.lock")
+    [[ -f pyproject.toml ]]   && seen+=("pyproject.toml")
+    pass "lockfile present: ${seen[*]}"
+  else
+    warn "no requirements.txt / uv.lock / pyproject.toml at repo root — run 'pip freeze > requirements.txt' inside your activated venv and commit it (see Week 1 Ch1)"
+  fi
   return 0
 }
 
diff --git a/.hyf/test.sh b/.hyf/test.sh
index fcedee8..f6a9eff 100755
--- a/.hyf/test.sh
+++ b/.hyf/test.sh
@@ -167,9 +167,17 @@ if [ -s task-2/AI_DEBUG.md ]; then
     fi
 fi
 
-# .gitignore should exclude Python cache files.
+# .gitignore should exclude Python cache files + the venv folder.
 check_gitignore_python ".gitignore"
 
+# Virtual environment folders (.venv/, venv/) must not be committed.
+# Curriculum: Week 1 Ch1 "Don't commit the venv folder".
+check_no_venv_committed
+
+# A lockfile (requirements.txt / uv.lock / pyproject.toml) must exist at the
+# repo root so a fresh venv can be reproduced from it.
+check_lockfile_present
+
 print_results "Week 1 Autograder"
 
 # ── Final score ──────────────────────────────────────────────────────────────