diff --git a/.binder/postBuild b/.binder/postBuild
index acd468f..2d5b161 100755
--- a/.binder/postBuild
+++ b/.binder/postBuild
@@ -4,12 +4,17 @@ set -euo pipefail
 echo "[postBuild] Editable install of local package"
 pip install -e .
 
+echo "[postBuild] Prune heavy, non-notebook files"
+rm -rf rcpchgrowth/tests || true
+rm -f  rcpchgrowth/data_tables/bayley-pineau.pdf || true
+rm -f  rcpchgrowth/data_tables/uk-who_resources/GrowthCharts.xls || true
+rm -f  rcpchgrowth/data_tables/uk-who_resources/*.bas || true
+rm -f  rcpchgrowth/data_tables/fenton/*.* || true
+
 echo "[postBuild] Warm up matplotlib font cache"
 python - <<'PY'
-import matplotlib.pyplot as plt  # triggers font cache build
+import matplotlib.pyplot as plt
 print("Matplotlib imported; font cache built.")
 PY
 
-echo "[postBuild] Warm up JupyterLab (pre-build static if needed)"
-jupyter lab build --minimize=False >/dev/null 2>&1 || true
 echo "[postBuild] Done"
\ No newline at end of file
diff --git a/.binder/runtime.txt b/.binder/runtime.txt
new file mode 100755
index 0000000..f31904f
--- /dev/null
+++ b/.binder/runtime.txt
@@ -0,0 +1 @@
+python-3.10
\ No newline at end of file