> 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.

## 5.41.8

**`(fix):`** Fix SDKs generated with `tcp_keepalive.enabled: true` ignoring the `HTTP_PROXY`, `HTTPS_PROXY`,
`ALL_PROXY` and `NO_PROXY` environment variables. httpx skips environment proxies whenever a
custom `transport` is passed, so the default sync and async clients now also pass `mounts`
built from the environment proxies, each carrying the keepalive socket options.

## 5.41.7

**`(fix):`** Add the `http_client_extra` option. When set (e.g. `http_client_extra: client`), `httpx` is
declared as an optional dependency exposed under that extra (`pip install <pkg>[client]`), so a
plain install of a package used for its models only (e.g. TwiML) does not pull in the HTTP stack.
Off by default; existing SDKs are unchanged.

## 5.41.6

**`(fix):`** Respect the `retry-after-ms` response header when computing retry delays. The header value was
compared to `0` before being converted to a number, raising a `TypeError` that was silently
swallowed, so the client always fell back to `Retry-After` or exponential backoff.