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Equation 44 · Why Coding Agents Fail: Long-Horizon Reliability in OpenAI Codex

What does this equation mean?

diLi>Ki+Fi.d_i L_i > K_i+F_i.

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This equation states a bound: one expression must stay on the indicated side of the other under the article’s assumptions. Read the equation part by part below; each part has a contextual explanation and a link to its mathematical background.

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did_i

Symbol d_i

the detection probability.

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LiL_i

Symbol L_i

LiL_i is a part of this expression. Its role is fixed by the surrounding article and by the operations shown in the formula.

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KiK_i

Symbol K_i

the check cost.

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FiF_i

Symbol F_i

the false-alarm cost.

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addition

addition

Add the term after the plus sign to the term or group before it.

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subscript

subscript

The lower label selects a particular version, component, or indexed member of the quantity. For example, x₀ and xₜ can be values at different positions.

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How to interpret it

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What the article says around this equation

Checkpoint placement is a value-of-information problem. Let an unchecked latent error at stage i create expected downstream loss LiL_i , a check cost KiK_i , detection probability did_i , and false-alarm cost FiF_i . A check is favorable when, approximately, diLi>Ki+Fid_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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