Rust SDK 0.12.0

March 31, 2026

Surrogate-Control and Surrogate-Key headers are preserved for shielded requests.
Interfaces for reusable sandboxes have been moved from the fastly::experimental::reusable_sessions module to fastly::http::serve.
Added new bot detection methods to Request.
Removed the deprecated write_bytes and write_str methods for HTTP bodies, in favor of std::io::Write trait methods.
Dynamic backends now have a 200 max_connections limit by default (previously unlimited), matching the default limit for static backends.
The following Request methods now return Result, rather than panicking on buffer size or UTF-8 decoding errors:
get_original_header_names
get_tls_raw_client_certificate
get_tls_cipher_openssl_name
get_tls_protocol
Added the fastly::http::body::StreamingBody::abandon method to explicitly abandon a stream.
Dropping an unfinished StreamingBodyHandle will now abandon the stream.
Added a new SendErrorCause::Http2StreamError variant, containing more details about unexpected HTTP/2 error responses.
FastlyStatus is now marked as #[must_use].
Removed the deprecated fastly::cache::core::Found::ttl method.
Clarified how calling Request::set_pass affects other cache override options.
Documented that Request::send_async and Request::send_async_streaming will fail if called after setting a before_send or after_send callback.
Improved the documentation for Image Optimizer functionality.