FA-61413 / Options payoff and settlement / Member archive

Contract adjustment for splits and special dividends: integral splits adjust the strike but not the contract count · case 03

Holders lose exposure after a 2-for-1 split.

Member previewVariant 3 · 3 implementations · 8 checks per implementation

Case contract

Inputs strike, contracts, deliverable, action and value. split [new, old]: if new is a multiple of old (ratio r), strike becomes strike/r rounded half-up to cents and contracts become contracts*r; otherwise the deliverable becomes floor(deliverable*new/old) with strike and contracts unchanged. special_div of at least 0.125 per share reduces the strike by the amount (rounded half-up to cents). Other actions, including ordinary_div, change nothing. Return [strike, contracts, deliverable].

Why this case matters

Option expiry, exercise and settlement engines move cash and shares; a wrong branch misstates obligations.

One recorded failure

Sample boundary fixture

This sample comes from the broken implementation of a controlled reproducer.

Boundary fixture	Actual	Expected	Outcome
regression split contract scaling 1	`[11.11, 3, 100]`	`[11.11, 9, 100]`	Failed

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