diff --git a/src/simulator/crates/mc-city/src/lib.rs b/src/simulator/crates/mc-city/src/lib.rs
index d4d3c69a..314d6344 100644
--- a/src/simulator/crates/mc-city/src/lib.rs
+++ b/src/simulator/crates/mc-city/src/lib.rs
@@ -102,7 +102,8 @@ pub use recipes::{
 };
 
 pub use yield_fold::{
-    tile_yields_from_collectibles, CollectiblesIndex, ResourceYieldMap, ResourceYields,
+    tile_yields_from_collectibles, tile_yields_from_collectibles_suppressed,
+    CollectiblesIndex, ResourceYieldMap, ResourceYields,
 };
 
 // Re-export biome-yield types
diff --git a/src/simulator/crates/mc-city/src/yield_fold.rs b/src/simulator/crates/mc-city/src/yield_fold.rs
index e33118aa..d8038a3b 100644
--- a/src/simulator/crates/mc-city/src/yield_fold.rs
+++ b/src/simulator/crates/mc-city/src/yield_fold.rs
@@ -149,4 +149,35 @@ mod tests {
         assert_eq!(a.iter().map(|t| t.coord).collect::<Vec<_>>(),
                    b.iter().map(|t| t.coord).collect::<Vec<_>>());
     }
+
+    #[test]
+    fn p2_76_suppressed_tile_yields_zero_collectible() {
+        // Tile (3,3): destroyed deposit / contaminated → zero yield.
+        // Tile (3,4): untouched → normal yield. The CollectiblesIndex is NOT
+        // mutated; suppression is a read-time overlay consult.
+        let mut index = CollectiblesIndex::new();
+        index.insert(
+            (3, 3),
+            vec![CollectibleRoll { resource_id: "iron_ore".into(), quantity: 2, quality: 1 }],
+        );
+        index.insert(
+            (3, 4),
+            vec![CollectibleRoll { resource_id: "iron_ore".into(), quantity: 2, quality: 1 }],
+        );
+        let mut resource_map = ResourceYieldMap::new();
+        resource_map.insert("iron_ore".into(), iron_ore_yields());
+
+        let suppressed = BTreeSet::from([(3, 3)]);
+        let yields = tile_yields_from_collectibles_suppressed(&index, &resource_map, &suppressed);
+
+        // Suppressed tile still present (worked-tile accounting unchanged) but zero.
+        let t33 = yields.iter().find(|t| t.coord == (3, 3)).expect("suppressed tile present");
+        assert_eq!(t33.production, 0.0, "destroyed/contaminated tile yields zero collectible");
+        // Untouched tile keeps its yield.
+        let t34 = yields.iter().find(|t| t.coord == (3, 4)).unwrap();
+        assert!((t34.production - 6.0).abs() < 1e-9, "untouched tile unaffected");
+
+        // The index itself was never mutated.
+        assert_eq!(index[&(3, 3)].len(), 1, "CollectiblesIndex not mutated by suppression");
+    }
 }
diff --git a/src/simulator/crates/mc-worldsim/src/lib.rs b/src/simulator/crates/mc-worldsim/src/lib.rs
index 7d9276ac..b29cc5ad 100644
--- a/src/simulator/crates/mc-worldsim/src/lib.rs
+++ b/src/simulator/crates/mc-worldsim/src/lib.rs
@@ -794,4 +794,112 @@ mod tests {
         );
         assert_eq!(a, b, "same seed must produce an identical succession tier sequence");
     }
+
+    // ── p2-76 — terraforming cascade bridgehead (1b seed / 4b decay) ─────────
+
+    use mc_core::improvement::SurfaceContaminationSpec;
+    use mc_state::game_state::TerraformEvent;
+    use mc_ecology::tile::TileContamination;
+
+    fn bunker_contamination_spec() -> SurfaceContaminationSpec {
+        SurfaceContaminationSpec {
+            duration_basis: "destroyed_deposit_tier".to_string(),
+            turns_per_tier: 10,
+            min_turns: 10,
+            tile_effect: "yields_zeroed_and_unworkable".to_string(),
+        }
+    }
+
+    /// 1b seeds the contamination overlay from a pending TerraformEvent (tier ×
+    /// turns_per_tier), and chronicles it; 4b decays it; the tile self-heals at 0.
+    #[test]
+    fn terraform_seeds_contamination_then_decays_and_self_heals() {
+        let mut sim = make_worldsim();
+        let mut state = make_state();
+        // Enqueue a tier-3 destruction at (8,8) → 30 contamination turns.
+        state.pending_terraform.push(TerraformEvent {
+            col: 8,
+            row: 8,
+            destroyed_tier: 3,
+            contamination: Some(bunker_contamination_spec()),
+        });
+
+        // First step: 1b seeds, 4b decays once (30 → 29).
+        sim.step(&mut state);
+        assert!(state.pending_terraform.is_empty(), "1b drains pending_terraform");
+        let c = sim.contamination_map().get(&(8, 8)).expect("contamination seeded");
+        assert_eq!(c.remaining_turns, 29, "30 seeded, decayed once this turn");
+        assert_eq!(c.source_tier, 3);
+        // Derived unworkable mirror carries the flat index.
+        let h = state.grid.as_ref().unwrap().height as u32;
+        assert!(state.unworkable_tiles.contains(&(8 * h + 8)), "unworkable mirror rebuilt");
+        // Chronicle carries the contamination event.
+        assert!(
+            sim.chronicle.entries().iter().any(|e| matches!(
+                e,
+                ChronicleEntry::WorldEvent { category, kind, .. }
+                    if category == "terraform" && kind == "surface_contamination"
+            )),
+            "contamination chronicle entry pushed"
+        );
+
+        // Run to expiry: 29 more steps → remaining hits 0 and the entry self-heals.
+        for _ in 0..29 {
+            sim.step(&mut state);
+        }
+        assert!(
+            sim.contamination_map().get(&(8, 8)).is_none(),
+            "contamination self-heals at 0 (fixed-duration model)"
+        );
+        assert!(
+            !state.unworkable_tiles.contains(&(8 * h + 8)),
+            "self-healed tile removed from the unworkable mirror"
+        );
+    }
+
+    /// The contamination overlay round-trips losslessly through serde (the
+    /// `worldsim_state` save envelope), restored via `restore_contamination_map`.
+    #[test]
+    fn contamination_map_round_trips_serde() {
+        let mut sim = make_worldsim();
+        let mut state = make_state();
+        state.pending_terraform.push(TerraformEvent {
+            col: 4,
+            row: 5,
+            destroyed_tier: 6,
+            contamination: Some(bunker_contamination_spec()),
+        });
+        sim.step(&mut state);
+        assert!(!sim.contamination_map().is_empty(), "precondition: contamination active");
+
+        // Serialize the overlay as the save layer would (pairs — tuple keys).
+        let pairs: Vec<(&(u16, u16), &TileContamination)> =
+            sim.contamination_map().iter().collect();
+        let json = serde_json::to_string(&pairs).expect("serialize contamination_map");
+        let restored_pairs: Vec<((u16, u16), TileContamination)> =
+            serde_json::from_str(&json).expect("deserialize");
+        let restored: BTreeMap<(u16, u16), TileContamination> =
+            restored_pairs.into_iter().collect();
+
+        let mut sim2 = make_worldsim();
+        sim2.restore_contamination_map(restored);
+        assert_eq!(
+            sim2.contamination_map(),
+            sim.contamination_map(),
+            "contamination overlay survives the save round-trip"
+        );
+    }
+
+    /// Determinism guard: the p2-76 sub-steps do not perturb the worldsim
+    /// trajectory when no terraform is pending (empty 1b/4b are no-ops).
+    #[test]
+    fn p2_76_substeps_are_noop_without_terraform() {
+        let mut sim = make_worldsim();
+        let mut state = make_state();
+        for _ in 0..5 {
+            sim.step(&mut state);
+        }
+        assert!(sim.contamination_map().is_empty(), "no contamination without terraform");
+        assert!(state.unworkable_tiles.is_empty(), "no unworkable tiles without terraform");
+    }
 }