diff --git a/aocsync.py b/aocsync.py
index 71898d8..663f30a 100755
--- a/aocsync.py
+++ b/aocsync.py
@@ -631,7 +631,7 @@ class CargoAOCRunner:
                 '--cpus', str(docker_config.get('cpus', '2')),  # Limit CPU
                 '--read-only',  # Read-only root filesystem
                 '--tmpfs', '/tmp:rw,noexec,nosuid,size=1g',  # Writable /tmp for cargo
-                '-v', f'{repo_root}:/repo:ro',  # Mount repo read-only
+                '-v', f'{repo_root}:/repo:rw',  # Mount repo read-write (cargo-aoc needs to write metadata files)
                 '-v', f'{build_cache_path}:/build:rw',  # Writable build directory
                 '-w', f'/repo/{work_dir_rel}',  # Working directory in container
             ]