diff --git a/crates/fidc-core/src/platform_expr_strategy.rs b/crates/fidc-core/src/platform_expr_strategy.rs
index 298f66d..c1de838 100644
--- a/crates/fidc-core/src/platform_expr_strategy.rs
+++ b/crates/fidc-core/src/platform_expr_strategy.rs
@@ -614,6 +614,13 @@ impl PlatformExprStrategy {
                 lhs / rhs
             }
         });
+        engine.register_fn("safe_div", |lhs: f64, rhs: f64| {
+            if rhs.abs() <= f64::EPSILON {
+                0.0
+            } else {
+                lhs / rhs
+            }
+        });
         engine.register_fn(
             "iff",
             |condition: bool, when_true: Dynamic, when_false: Dynamic| {
@@ -8432,6 +8439,32 @@ mod tests {
         assert!(!rewritten.contains('?'));
     }
 
+    #[test]
+    fn platform_expr_safe_div_supports_two_and_three_arg_forms() {
+        let strategy = PlatformExprStrategy::new(PlatformExprStrategyConfig::microcap_rotation());
+        assert_eq!(
+            strategy
+                .engine
+                .eval::<f64>("safe_div(6.0, 3.0)")
+                .expect("two-arg safe_div should evaluate"),
+            2.0
+        );
+        assert_eq!(
+            strategy
+                .engine
+                .eval::<f64>("safe_div(6.0, 0.0)")
+                .expect("two-arg safe_div should use zero fallback"),
+            0.0
+        );
+        assert_eq!(
+            strategy
+                .engine
+                .eval::<f64>("safe_div(6.0, 0.0, -1.0)")
+                .expect("three-arg safe_div should preserve explicit fallback"),
+            -1.0
+        );
+    }
+
     #[test]
     fn platform_expr_limit_flags_are_directional() {
         assert!(PlatformExprStrategy::price_is_at_or_above_upper_limit(
diff --git a/crates/fidc-core/src/platform_runtime_schema.rs b/crates/fidc-core/src/platform_runtime_schema.rs
index 6270125..cc9fda1 100644
--- a/crates/fidc-core/src/platform_runtime_schema.rs
+++ b/crates/fidc-core/src/platform_runtime_schema.rs
@@ -140,6 +140,7 @@ const RESERVED_SCOPE_NAMES: &[&str] = &[
     "ask1_volume",
     "turnover_ratio",
     "effective_turnover_ratio",
+    "up_days_stock",
     "open",
     "high",
     "low",
@@ -328,6 +329,7 @@ mod tests {
             "avg_cost",
             "current_price",
             "stock_ma_short",
+            "up_days_stock",
         ] {
             assert!(
                 names.contains(required),