Coroutine render publication

TerminalSession publishes copied render data for consumers that do not need synchronous access to the live grid. Read a publication with readPublishedFrame and observe renderGeneration for invalidation. Both are described in the session README.

Invalidation and conflation

One session worker uses a conflated channel to process render invalidations. The latest scrollback offset and requested row count share an atomic packed request; a generation counter identifies newer invalidations. No request object or queue entry is created for each viewport change.

The worker extracts the requested viewport under mutation serialization and copies it into TerminalRenderPublisher. It advances renderGeneration only after successful promotion. Generations are opaque invalidation tokens: intermediate generations may be skipped, and the flow is not a log of output.

The first publication after an idle period is immediate. During continuous host output, the worker waits up to a 16 ms display interval before sampling the newest request again, including a trailing frame for the final invalidation. Explicit viewport, resize, palette, and cursor invalidations interrupt that wait. These are scheduling rules, not a frame-latency guarantee; copying, dispatcher load, and reader leases can delay publication.

Incoming output preserves the current requested scrollback offset. A new requestRender replaces it. One session has one published viewport; unrelated scroll positions must not compete for it. Direct readRenderFrame calls can read a requested range without changing the publication request.

Failure and synchronized output

A failed cache copy leaves the previous successful publication readable. The worker returns rather than retrying in a loop; a later invalidation can trigger another attempt. Cancellation propagates.

Synchronized-output mode defers normal publication. A worker-dispatcher timer turns that mode off after the 100 ms safety timeout and invalidates rendering. Normal mode disable cancels the timer. Timer dispatch can be delayed by scheduler load, so this is not a real-time deadline.

Closure cancels render work, finalizes parser EOF under mutation serialization, and attempts synchronous publication of the final requested viewport even when synchronized output was active. Closed is retained after those attempts. Consumers may continue reading a successful final cache but cannot request new session publications. See closed-session presentation.

Ownership and allocation boundary

The worker dispatcher belongs to the caller. Closing the session cancels its jobs without disposing that dispatcher or consumer scopes. renderGeneration is a retained state flow and does not complete on closure.

Published caches and arrays are borrowed only inside readPublishedFrame. A reader lease prevents recycling of its cache while another frame is promoted. Copy promptly and do not mutate or retain borrowed storage, close the session, or reenter session mutation/publication from the callback. Long-lived leases can delay further copying and closure.

Invalidation avoids per-request objects. Parser/core mutation and cell copying do not dispatch a coroutine per cell. Coroutine/channel scheduling, cache growth, and consumer work have separate allocation costs; this is not an allocation-free claim for an entire frame or session. Input output uses the independent writer, not the render worker.