Breaking Changes:

• PathEvent is now #[non_exhaustive] and adds PmtuUpdated. Rust applications that exhaustively match path events must add a wildcard arm. C applications should handle QUICHE_PATH_EVENT_PMTU_UPDATED when PMTU discovery is enabled.
• The supported boring range is now >=4.19,<6, so fresh dependency resolution uses 5.x by default while consumers pinned to 4.19 remain supported. Static C applications linking libquiche.a must use a C++ linker driver or otherwise link the C++ runtime. Boring 5 enables post-quantum groups by default, which can split the ClientHello across multiple Initial packets. Applications that need smaller or deterministic ClientHellos can use Config::set_curves_list() or quiche_config_set_curves_list().

Highlights:

• Added Connection::stream_readable_len() to report the contiguous bytes currently readable from a stream, up to a caller-supplied limit, without copying data.
• Fixed connection-level flow-control double counting from zero-length non-FIN STREAM frames, which could close long-running bulk transfers with FLOW_CONTROL_ERROR.
• Fixed handshake callback configuration being lost when early data was accepted during an in-progress 0-RTT handshake.
• Fixed cleanup of unknown and empty HTTP/3 unidirectional streams, and compressed completed-stream tracking into ranges to reduce retained memory.
• Updated intrusive-collections to 0.10.3 for upstream undefined-behavior and atomic-link race fixes affecting stream priority queues.

Full changelog at 0.29.3...0.30.0