> This page is for SDK, version Legacy.
> For other versions, use one of these documentation indexes:
> - Current (default): https://buildwithfern.com/learn/sdks/current/llms.txt
> - Legacy: https://buildwithfern.com/learn/sdks/legacy/llms.txt

> For clean Markdown content of this page, append .md to this URL. For the complete documentation index, see https://buildwithfern.com/learn/llms.txt. For task-scoped instructions for coding agents working in a Fern project, see https://buildwithfern.com/learn/home/fern-instructions.md.

## 1.39.4

**`(fix):`** XML (TwiML) serialization drops characters outside the XML 1.0 `Char` production (e.g. `\x01`) from text and attribute values instead of emitting XML that no parser accepts.

## 1.39.3

**`(fix):`** XML (TwiML) types accept the declaration flag positionally, like the legacy TwiML gem:
`response.to_s(false)` and `response.to_xml(false)` omit `<?xml ...?>`; the `xml_declaration:`
keyword still works.