Project 5 Whole-Share Execution and Split-Entitlement Boundary

2026-10-14. The target at the signal close is still rounded toward zero and then converted to the share units on the execution date. Actual executions remain whole-share only. This note adds no broker fractional-share execution or cash-in-lieu mechanism.

Split entitlement is calculated by exact decimal multiplication of the input float's current text representation. For example, 100 shares × 0.29 gives 29 shares. The same conversion is used for holdings, targets, parent exit orders, carried orders across days, and superseded order quantities, avoiding truncation of 28.999… to 28 shares. If an integer entitlement cannot be represented exactly in the current float ledger, the system raises an explicit error. The ratio field is the actual decimal value supplied as input; 0.3333333333333333 does not mean the exact fraction 1/3.

The mathematical ledger retains 5 × 1.5 = 7.5 shares and the corresponding dividend entitlement. If an actual holding is about to become a non-integer share count, the whole-share execution simulator rejects the entire path before that day's overnight accrual and corporate action are booked. The error lists the pair, security, date, prior share count, and ratio. Do not remove the failed window and continue reporting a fixed sample. A CLI exception path may leave an empty directory or intermediate files from earlier steps; only a complete successful summary and run status count as evidence of completion.

A non-integer split ratio does not itself trigger rejection: 4 × 1.5 = 6 and 5 × 0.2 = 1 are supported; a split event on a flat position still has 0 shares. When flat, a 5-share target multiplied by 1.5 creates a 7.5-share order; under the existing whole-share execution rule, 7 shares actually fill and the entry remainder is canceled. This differs from an existing 5-share holding receiving a 7.5-share entitlement.

Exit remainders are worked over day by day, subject to capacity, finite sample length, and the support domain. At the sample end, any unfilled portion is recorded under the existing protocol as opportunity cost and an open episode. The current simulator does not silently mark a half-share residual position as closed. If a real sample produces fractional entitlements, an actual fractional-execution rule or a documented cash-in-lieu basis for quantity, amount, timing, and fees is required, followed by separate acceptance of the corresponding protocol.

This revision accepts only the explicit execution support domain and consistency of share-count conversion. Historical constructed data, preregistration v1/v2, cost and threshold grids, and negative results retain their historical identity. The 14 boundary checks and 52 related regressions passed in that historical round; this does not mean that the full CLI grid, Notebook, or market research was rerun. Real empirical work remains blocked, and the complete Project 5 is not verified.