Frame delivery

Requirements

Public frame contract

Messages are tagged frame, title, resetTitle, bell or exit. A frame carries subscriptionId, sequence, rows/clusters/styles, cursor, full, viewport, bracketedPaste and focusReporting. Viewports carry generation, columns and screenLines. The shared JSON fixture checks Rust serialization and TypeScript consumption. Exit currently carries no process exit-code payload.

Attachment may deliver its initial frame before the invoke response. The client buffers that bootstrap until it knows the subscription. Resize requests are coalesced and ordered through remounts; repeated observations of the requested size cannot create a frame/readiness feedback loop. Old viewports release only their own frame credit. Old attachment callbacks and errors are inert.

Bootstrap capture and subscription installation MUST exclude concurrent frame offers. Output received during attachment MUST appear in the bootstrap or the successor released by its exact acknowledgement. Publication retains the same one-frame credit and viewport fences; initial output requires no later shell activity to become visible.

Every output capture and its publisher offer MUST be ordered atomically under the publisher-to-engine lock order, including initial resize snapshots and PTY reader snapshots. An older blank capture MUST NOT replace newer initial output while bootstrap credit or viewport readiness is held. The latest pending snapshot must reflect capture order, without requiring a subsequent shell byte.

Subscription replacement includes its output sink. Clearing an old sink MUST remain atomic with faulting that subscription; a concurrent replacement MUST retain its bootstrap channel and subsequent output without requiring new input.