QUIC stream resets do not guarantee delivery of stream data sent before the reset. This is a problem for HTTP/3 when the correct protocol outcome is an abrupt stream termination, but the sender still has a bounded prefix worth delivering, such as response headers, a short diagnostic response body, or a partial response received from an upstream host. RESET_STREAM_AT provides reliable delivery of that prefix and is already used by WebTransport over HTTP/3 when resetting streams. The same mechanism also fits HTTP/3 CONNECT tunnels, intermediary failures after response commitment, malformed decoded HTTP messages, and requests rejected before application processing.