YAML alias limits

OmegaConf limits how far YAML anchors and aliases can expand a document. This protects applications from unexpectedly large input, including YAML bombs. If a file from an untrusted source hits the limit, simplify its anchors, aliases, or merge keys rather than disabling the protection.

For trusted YAML that legitimately needs more expansion, set a larger limit at the call site:

cfg = OmegaConf.load("config.yaml", max_yaml_expanded_nodes=50_000)
cfg = OmegaConf.create(yaml_string, max_yaml_expanded_nodes=50_000)

Passing None disables the limit for trusted input. If you do not control the call site, set OMEGACONF_MAX_YAML_EXPANDED_NODES to a positive integer, or none to disable the limit. An explicit function argument takes precedence over the environment variable.

The default is 10,000 expanded nodes. OmegaConf also rejects documents over 1,000 expanded nodes when aliases make them more than 100 times larger than the unexpanded document. Scalar keys and values, mappings, and lists all count. Recursive aliases are rejected even if the expansion limit is disabled.