Constant SSA_TEARDOWN_SWEEP_WINDOW 

const SSA_TEARDOWN_SWEEP_WINDOW: u32 = 64;

How many of a session’s most recent SSA cycles teardown sweeps.

Only unrecovered cycles hold reconstructor state — a recovered one removes itself. The live set is bounded by the batch size: pipelining runs at most one batch ahead of the active one, so at most 2 × MAX_SSA_BATCH_SIZE indices can be unrecovered at once, which this window covers with room to spare. It is deliberately well above even that, because the cost of being wrong is asymmetric in one direction only: a cycle missed here is still reclaimed by unused_verifier_lifetime, whereas sweeping every index a session ever used is unbounded work on the eviction listener, and leaves a tombstone per index behind it.