How many trailing tokens this source needs to see in TokenView.tail.
The session retains the maximum across its sources; a source that needs
more history than that keeps its own copy (see observe()).
Methods
Optionalobserve
observe?(ids:readonlynumber[]):void
Every token that actually entered the sequence — sampled or injected —
in order. Sources that maintain an index grow it here.
Propose the tokens that follow tail, or null. The caller clamps
(EOS / delimiter / max span / budget), so a source may return more than
the budget allows.
How many trailing tokens this source needs to see in
TokenView.tail. The session retains the maximum across its sources; a source that needs more history than that keeps its own copy (see observe()).