> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://buildwithfern.com/learn/llms.txt.

## 2.20.2

**`(fix):`** Global headers typed as a `literal<"...">` with an `env` fallback no longer throw when
neither the constructor parameter nor the environment variable is set. The literal is
known at compile time, so it is now used as the header's default value.