The bound summed only packets still awaiting an ack. Once frames above a lost
packet were acknowledged they stopped counting, so a receiver could be made to
hold more than 4 MiB behind one loss, and its hold buffer ended the session.
The sender now keeps the payload size of each acknowledged sequence above the
lowest pending one until the lowest advances past it, in Rust, TypeScript,
Python and C#. Tests per runtime: one lost packet, four acknowledged 1 MiB
frames, the fifth refused until the gap closes; and the floor moving to a new
lowest sequence.
Co-Authored-By: Claude Sonnet 5.5 <noreply@anthropic.com>