5.18.2

(fix): Preserve leading and trailing underscores in generated namespace/module names. Previously a subpackage named _agents (via x-fern-sdk-group-name: _agents) was transformed to agents, stripping the underscore. Now it generates a private _agents/ Python module with a matching client._agents accessor, enabling the pattern of hiding autogenerated clients behind a hand-written public layer.

This is scoped to namespace/module names only. Parameter, field, and property casing is unchanged, so existing SDK method signatures are unaffected.

Note: if you already use a group name that begins or ends with an underscore (e.g. x-fern-sdk-group-name: _agents), the generated module and accessor now preserve that underscore (_agents/ and client._agents) instead of stripping it (agents/ / client.agents). Regenerating will change those import paths.