diff --git a/crates/fidc-core/src/engine.rs b/crates/fidc-core/src/engine.rs
index 3ee1506..6042ad6 100644
--- a/crates/fidc-core/src/engine.rs
+++ b/crates/fidc-core/src/engine.rs
@@ -26,6 +26,9 @@ use crate::strategy::{
     TargetPortfolioOrderPricing,
 };
 
+pub const POST_CLOSE_FIXED_PRICE_EFFECTIVE_DATE: NaiveDate =
+    NaiveDate::from_ymd_opt(2026, 7, 6).expect("valid post-close effective date");
+
 #[derive(Debug, Error)]
 pub enum BacktestError {
     #[error(transparent)]
@@ -1970,6 +1973,16 @@ where
             })
             .filter(|date| self.config.end_date.map(|end| *date <= end).unwrap_or(true))
             .collect::<Vec<_>>();
+        if self.broker.matching_type() == MatchingType::PostCloseFixedPrice
+            && calendar_dates
+                .first()
+                .is_some_and(|date| *date < POST_CLOSE_FIXED_PRICE_EFFECTIVE_DATE)
+        {
+            return Err(BacktestError::Execution(format!(
+                "post_close_fixed_price is unavailable before {}",
+                POST_CLOSE_FIXED_PRICE_EFFECTIVE_DATE
+            )));
+        }
         let has_decision_inputs = |date: NaiveDate| {
             !self.data.factor_snapshot_rows_on(date).is_empty()
                 && !self.data.candidate_snapshot_rows_on(date).is_empty()