diff --git a/.flake8 b/.flake8
index c7b5cf7f80..d908f846ad 100644
--- a/.flake8
+++ b/.flake8
@@ -5,8 +5,8 @@ exclude =
     # Do not traverse examples and tools
     examples,
     tools,
-    # Reference scripts for skills
-    skills,
+    # Do not traverse .venv directories
+    .venv*,
     # Do not include package initializers
     __init__.py,
     # No need to traverse our git directory
diff --git a/skills/slice-model/slice_model.py b/skills/slice-model/slice_model.py
index 88d696a5ed..3707a38836 100644
--- a/skills/slice-model/slice_model.py
+++ b/skills/slice-model/slice_model.py
@@ -223,6 +223,7 @@ def patch_config(cfg: dict, families: dict[str, Family], new_vocab: int | None,
                 lfam = next((f for f in families.values() if f.kind == "layer"), None)
                 if lfam is None:
                     continue
+                assert lfam.kept is not None
                 d[key] = sum(1 for i in lfam.kept if i < val)
             elif "expert" in key and fam is not None and fam.kind == "expert" and not any(x in key for x in EXPERT_KEY_EXCLUDE):
                 d[key] = fam.new_count
@@ -236,6 +237,7 @@ def patch_config(cfg: dict, families: dict[str, Family], new_vocab: int | None,
             # per-layer lists, e.g. layer_types
             fam = by_card.get(len(val))
             if fam is not None and fam.kind == "layer" and len(val) in (fam.card, fam.regular_total):
+                assert fam.kept is not None
                 d[key] = [val[i] for i in fam.kept if i < len(val)]
                 log.append(f"{key}: list[{len(val)}] -> list[{len(d[key])}]")
     return log
diff --git a/ty.toml b/ty.toml
index e2036cd2ed..340b0649d3 100644
--- a/ty.toml
+++ b/ty.toml
@@ -8,7 +8,6 @@ deprecated = "warn"
 [src]
 exclude = [
     "./tools/mtmd/legacy-models/**",
-    "./skills/**",
 ]
 
 [[overrides]]