fix

packages/manim-mcp-server/package.nix

@@ -34,7 +34,13 @@ stdenv.mkDerivation rec {
     runHook preInstall
 
     mkdir -p $out/bin $out/lib/manim-mcp-server
-    cp src/manim_server.py $out/lib/manim-mcp-server/
+
+    # Patch manim_server.py to use a configurable media directory
+    # The original code uses a path relative to __file__ which fails in the read-only Nix store
+    substitute src/manim_server.py $out/lib/manim-mcp-server/manim_server.py \
+      --replace-fail \
+        'BASE_DIR = os.path.join(os.path.dirname(os.path.abspath(__file__)), "media")' \
+        'BASE_DIR = os.getenv("MANIM_MCP_MEDIA_DIR", os.path.join(os.path.expanduser("~"), ".cache", "manim-mcp-server", "media"))'
 
     makeWrapper ${python}/bin/python $out/bin/manim-mcp-server \
       --add-flags "$out/lib/manim-mcp-server/manim_server.py" \