# T02: Config Priority & Error Paths (read-only)

Analyze, read-only, how `python3 -m ledger list` chooses the transactions CSV. Trace the default file, the JSON config file, the `LEDGER_DATA_FILE` environment variable, and the global `--data-file` flag; explain the actual priority order, how relative paths resolve, what happens when the config is malformed or the target file is missing, and which module finally reads the data. Back each point with a real relative path and function/class name. Do not modify files; mark anything uncertain explicitly instead of guessing.