DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.
A new periodic interval-based keepalive mechanism has been added to the WebSocket transport, supplementing the existing activity-triggered keepalive. This should improve connection stability during idle periods in remote sessions.
Evidence
New keepalive interval (search for "WebSocketTransport: Sent keep_alive (interval)" and keepaliveInterval)
Strings lifted out of the shipped bundle, so the claim above can be checked against them.