Symbol d_i

The passage around this formula

Checkpoint placement is a value-of-information problem. Let an unchecked latent error at stage i create expected downstream loss $L_i$ , a check cost $K_i$ , detection probability $d_i$ , and false-alarm cost $F_i$ . A check is favorable when, approximately, $d_i L_i > K_i+F_i$. High-value checkpoints occur before expensive or irreversible transitions: after specification, before schema migration, after dependency changes, before broad refactors, before network or credential escalation, and before merge or deployment. Cheap deterministic checks should run earlier and more often than expensive human review.

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