Reforecasting Mid-Year

multiple reforecast versions may coexist (e.g., Q2 reforecast, Q3 reforecast) without overwriting each other

negative) when a Finance Lead attempts to modify an H1 actual period then 403 with error_code: actuals_immutable.

Reforecast version must lock prior-period actuals as immutable and open only future periods for editing;
the system must clearly label which periods are actuals versus forecast in all reports;
multiple reforecast versions may coexist (e.g., Q2 reforecast, Q3 reforecast) without overwriting each other;
full-year projected vs. original budget comparison must be a standard report view;
approved reforecast must replace the prior forecast as the default comparison in budget-vs-actual reports (configurable);
commentary fields must be required on accounts with a configurable variance threshold versus the original budget.

Given H1 actuals locked in the reforecast version;
when Business Unit Finance Leads revise H2 estimates and FP&A Manager approves the reforecast;
then system displays H1 actuals as immutable, H2 as editable, full-year projected P&L as H1 actuals + H2 reforecast, and commentary is required on accounts with variance versus original budget exceeding threshold;
(negative) when a Finance Lead attempts to modify an H1 actual period then 403 with error_code: actuals_immutable.

reforecast_version { id: rfv_*, budget_version_id: string, name: string, lock_through_period: date, status: enum(OPEN/APPROVED), external_id: string };
reforecast_line { id: rfl_*, version_id: string, account_code: string, entity_id: string, period: date, amount_minor: int64, currency_code: char(3), is_actual: bool, commentary: string, external_id: string };
(reference, product may differ).

POST /v1/reforecast-versions { budget_version_id, name, lock_through_period, external_id } -> 201 { id, status: OPEN };
PUT /v1/reforecast-versions/{id}/lines/{line_id} { amount_minor, commentary };
POST /v1/reforecast-versions/{id}/approve;
emits reforecast.approved event;
idempotent via external_id.

OPEN -> APPROVED;
guard: APPROVED replaces prior forecast as default comparison in budget-vs-actual reports (configurable);
H1 actual periods are immutable;
multiple reforecast versions coexist without overwriting.