diff --git a/crates/fidc-core/src/platform_expr_strategy.rs b/crates/fidc-core/src/platform_expr_strategy.rs
index 76af552..ba01a91 100644
--- a/crates/fidc-core/src/platform_expr_strategy.rs
+++ b/crates/fidc-core/src/platform_expr_strategy.rs
@@ -27,6 +27,7 @@ use crate::numeric_expr_vm::{
     self, EvalError as NumericVmEvalError, Program as NumericVmProgram,
     Scratch as NumericVmScratch, Value as NumericVmValue, ValueType as NumericVmValueType,
 };
+use crate::numeric_factors::NumericFactorMap;
 use crate::portfolio::PortfolioState;
 use crate::holding_policy::{AutomaticTradeProtection, AutomaticTradePermission, HoldingLifecycleEvidence};
 
@@ -1010,7 +1011,7 @@ struct StockExpressionState {
     stock_volume_ma60: f64,
     stock_volume_ma100: f64,
     current_series_end: Option<usize>,
-    extra_factors: BTreeMap<String, f64>,
+    extra_factors: NumericFactorMap,
     extra_text_factors: BTreeMap<String, String>,
 }
 
@@ -4390,11 +4391,14 @@ impl PlatformExprStrategy {
                     .factor_snapshot_rows_on(date)
                     .iter()
                     .flat_map(|row| {
-                        row.extra_factors.keys().map(|key| key.to_string()).chain(
+                        row.extra_factors.keys().map(|key| key.as_ref()).chain(
                             row.adjustment_factor_backward1
-                                .map(|_| BACKWARD_ADJUSTMENT_FACTOR_FIELD.to_string()),
+                                .map(|_| BACKWARD_ADJUSTMENT_FACTOR_FIELD),
                         )
                     })
+                    .collect::<BTreeSet<_>>()
+                    .into_iter()
+                    .map(str::to_owned)
                     .collect()
             } else {
                 BTreeSet::new()
@@ -4403,7 +4407,10 @@ impl PlatformExprStrategy {
                 ctx.data
                     .factor_text_rows_on(date)
                     .iter()
-                    .map(|row| row.field.clone())
+                    .map(|row| row.field.as_str())
+                    .collect::<BTreeSet<_>>()
+                    .into_iter()
+                    .map(str::to_owned)
                     .collect()
             } else {
                 BTreeSet::new()
@@ -4896,10 +4903,10 @@ impl PlatformExprStrategy {
                     self.stock_extra_factor_map_required
                         || self.stock_extra_factor_identifiers.contains(field.as_ref())
                 })
-                .map(|(field, value)| (field.to_string(), *value))
+                .map(|(field, value)| (field.clone(), *value))
                 .collect()
         } else {
-            BTreeMap::new()
+            NumericFactorMap::new()
         };
         if !self.config.completed_session_factor_fields.is_empty() {
             let visible_date = completed_session_factor_date(
@@ -4914,7 +4921,7 @@ impl PlatformExprStrategy {
                         .and_then(|row| row.extra_factors.get(field.as_str()))
                         .copied()
                         .unwrap_or(f64::NAN);
-                    extra_factors.insert(field.clone(), value);
+                    extra_factors.insert(field.clone().into(), value);
                 }
             }
         }
@@ -4925,7 +4932,7 @@ impl PlatformExprStrategy {
                     .contains(BACKWARD_ADJUSTMENT_FACTOR_FIELD))
             && let Some(value) = factor.adjustment_factor_backward1
         {
-            extra_factors.insert(BACKWARD_ADJUSTMENT_FACTOR_FIELD.to_string(), value);
+            extra_factors.insert(BACKWARD_ADJUSTMENT_FACTOR_FIELD.into(), value);
         }
 
         let state = StockExpressionState {
@@ -5642,7 +5649,7 @@ impl PlatformExprStrategy {
                     Dynamic::from(stock.stock_volume_ma100),
                 );
                 for (key, value) in &stock.extra_factors {
-                    factors.insert(key.clone().into(), Dynamic::from(*value));
+                    factors.insert(key.as_ref().into(), Dynamic::from(*value));
                 }
                 for (key, value) in &stock.extra_text_factors {
                     factors.insert(key.clone().into(), Dynamic::from(value.clone()));
@@ -14546,6 +14553,7 @@ mod tests {
     use std::sync::Arc;
 
     use chrono::{NaiveDate, NaiveTime};
+    use rhai::{Dynamic, Map};
 
     use super::{
         CompiledRuntimeHelperArgs, PlatformAccountActionKind, PlatformExplicitActionStage,
@@ -17542,6 +17550,18 @@ mod tests {
             .stock_state_with_factor_date(&ctx, date, date, present_symbol)
             .expect("factor map stock state");
         assert!(map_stock.extra_factors.contains_key("unused_factor"));
+        let mut numeric_state = (*map_stock).clone();
+        numeric_state.extra_factors.insert("negative_zero".into(), -0.0);
+        numeric_state.extra_factors.insert("undefined_value".into(), f64::NAN);
+        let copied_state = numeric_state.clone();
+        assert_eq!(copied_state.extra_factors["negative_zero"].to_bits(), (-0.0_f64).to_bits());
+        assert!(copied_state.extra_factors["undefined_value"].is_nan());
+        let exposed = copied_state.extra_factors.iter()
+            .map(|(key, value)| (key.as_ref().into(), Dynamic::from(*value)))
+            .collect::<Map>();
+        assert_eq!(exposed["negative_zero"].as_float().unwrap().to_bits(), (-0.0_f64).to_bits());
+        assert!(exposed["undefined_value"].as_float().unwrap().is_nan());
+        assert!(!exposed.contains_key("missing_factor"));
         let map_day = map_strategy
             .day_state(&ctx, date)
             .expect("factor map day state");