diff --git a/docs/showcase/run.py b/docs/showcase/run.py
index 8ea6c9fc9..6b680e9f2 100644
--- a/docs/showcase/run.py
+++ b/docs/showcase/run.py
@@ -1,6 +1,16 @@
 #!/usr/bin/env python3
 """lcb.py FILE.jsonl — run control requests from a JSON-lines file ({"method":..., "params":...} or {"sleep": s})."""
 import json, socket, sys, time
+from pathlib import Path
+
+
+def _jsonl_path(arg):
+    """Resolve the CLI file argument; require an existing regular file."""
+    path = Path(arg).resolve()
+    if not path.is_file():
+        sys.exit(f"not a readable file: {arg}")
+    return path
+
 def call(method, params):
     s = socket.create_connection(("127.0.0.1", 7980), timeout=180)
     s.sendall((json.dumps({"id": 1, "method": method, "params": params}) + "\n").encode())
@@ -10,7 +20,7 @@ def call(method, params):
         if not c: break
         buf += c
     return json.loads(buf)
-for line in open(sys.argv[1]):
+for line in open(_jsonl_path(sys.argv[1])):
     line = line.strip()
     if not line or line.startswith("#"): continue
     r = json.loads(line)
diff --git a/tools/spectral_camera_table.py b/tools/spectral_camera_table.py
index b05ac2802..0e6fef7df 100644
--- a/tools/spectral_camera_table.py
+++ b/tools/spectral_camera_table.py
@@ -19,6 +19,23 @@ import sys
 import colour
 import numpy as np
 from scipy.optimize import minimize
+from pathlib import Path
+
+
+def _existing_dir(arg):
+    """Resolve a directory CLI argument; require it to exist."""
+    path = Path(arg).resolve()
+    if not path.is_dir():
+        sys.exit(f"not a directory: {arg}")
+    return str(path)
+
+
+def _out_path(arg):
+    """Resolve an output path CLI argument; require its parent to exist."""
+    path = Path(arg).resolve()
+    if not path.parent.is_dir():
+        sys.exit(f"output directory does not exist: {arg}")
+    return str(path)
 
 WL = np.arange(380, 781, 5)
 D50 = colour.xy_to_XYZ(colour.CCS_ILLUMINANTS["CIE 1931 2 Degree Standard Observer"]["D50"])
@@ -119,4 +136,4 @@ def main(root, out):
 if __name__ == "__main__":
     if len(sys.argv) != 3:
         sys.exit("usage: spectral_camera_table.py <rawtoaces-data checkout> <output .rs>")
-    main(sys.argv[1], sys.argv[2])
+    main(_existing_dir(sys.argv[1]), _out_path(sys.argv[2]))