# Timer Activation Guidance
- Timer schedule identity, due observation, value, and acknowledgement are
durable plugin state. Wall-clock time is an observation supplied by `Clock`,
never canonical Cymule state.
- `receive` may return only a currently due timer with an exact target selected
from `ParkedWaitIndex`. Missing targets leave the timer pending.
- Acknowledgement occurs only after the activation CAS. Lost acknowledgement
must redeliver the identical activation ID, timer ID, target, and value.
- SQLite contention uses a zero busy timeout and surfaces as a conflict. Tests
use a manual clock; never depend on sleeps or wall-clock races.