An ordinary Session's composer now uploads each image draft through the
background upload queue as soon as it is added. The raw upload route stages
the body as a prompt image when the request names its media type: the Host
reads at most the per-image byte limit, then validates, normalizes, and
stores the image as prompt admission would. The prompt cites the receipt in
a file part; prompt admission resolves it to the stored image, applies the
image-input check, and counts stored images toward maxImagesPerMessage.
Send waits for every image receipt, and a failed image upload turns its
thumbnail into a retry control. Commands and subagent continuations keep
encoding images inline.
A steer or follow-up accepted while a turn is closing is now claimed by a
fresh turn at the driver's clean exit instead of stranding in the inbox;
cancellation and pre-step rejection still park accepted work. Continuable
subagent follow-ups accept image parts: the wire is upload-shaped, the Host
admits and persists each batch before inbox acceptance, and delivery is
refused when the child model declines image input. The queue dock renders
durable image thumbnails instead of an [image] text marker.
Fixes#3186
Yichen Jiang