diff --git a/apexchainx_calculator/src/lib.rs b/apexchainx_calculator/src/lib.rs
index a8d11bd..764c8ed 100644
--- a/apexchainx_calculator/src/lib.rs
+++ b/apexchainx_calculator/src/lib.rs
@@ -546,6 +546,71 @@ impl SLACalculatorContract {
         Ok(())
     }
 
+    // Initialise any storage keys that may be missing from older schema
+    // versions. This is intentionally conservative: only set a value when
+    // the key is absent so migration is idempotent and does not overwrite
+    // existing state.
+    fn init_missing_storage_defaults(env: &Env) {
+        let inst = env.storage().instance();
+
+        if !inst.has(&PAUSED_KEY) {
+            inst.set(&PAUSED_KEY, &false);
+        }
+
+        if !inst.has(&STATS_KEY) {
+            inst.set(
+                &STATS_KEY,
+                &SLAStats {
+                    total_calculations: 0,
+                    total_violations: 0,
+                    total_rewards: 0,
+                    total_penalties: 0,
+                },
+            );
+        }
+
+        if !inst.has(&HISTORY_KEY) {
+            inst.set(&HISTORY_KEY, &Vec::<SLAResult>::new(env));
+        }
+
+        if !inst.has(&CONFIG_KEY) {
+            let mut configs = Map::<Symbol, SLAConfig>::new(env);
+            configs.set(
+                symbol_short!("critical"),
+                SLAConfig {
+                    threshold_minutes: 15,
+                    penalty_per_minute: 100,
+                    reward_base: 750,
+                },
+            );
+            configs.set(
+                symbol_short!("high"),
+                SLAConfig {
+                    threshold_minutes: 30,
+                    penalty_per_minute: 50,
+                    reward_base: 750,
+                },
+            );
+            configs.set(
+                symbol_short!("medium"),
+                SLAConfig {
+                    threshold_minutes: 60,
+                    penalty_per_minute: 25,
+                    reward_base: 750,
+                },
+            );
+            configs.set(
+                symbol_short!("low"),
+                SLAConfig {
+                    threshold_minutes: 120,
+                    penalty_per_minute: 10,
+                    reward_base: 600,
+                },
+            );
+            inst.set(&CONFIG_KEY, &configs);
+        }
+    }
+
     // -------------------------------------------------------------------
     // #61 – Storage migration harness
     // -------------------------------------------------------------------
@@ -593,6 +658,11 @@ impl SLACalculatorContract {
 
         // v0 → v1: stamp the version; all other fields were set by initialize
         if current == 0 {
+            // Ensure any storage keys that might be missing from older
+            // deployments are initialised to deterministic defaults before
+            // we mark the storage version as migrated. This codifies the
+            // contract: migration arms must initialise newly-added keys.
+            Self::init_missing_storage_defaults(&env);
             env.storage().instance().set(&STORAGE_VERSION_KEY, &1u32);
             current = 1;
         }
diff --git a/apexchainx_calculator/src/tests.rs b/apexchainx_calculator/src/tests.rs
index 79d299e..fff7611 100644
--- a/apexchainx_calculator/src/tests.rs
+++ b/apexchainx_calculator/src/tests.rs
@@ -3200,6 +3200,39 @@ fn test_get_migration_state_after_migrate_shows_no_migration_needed() {
     assert!(!info.needs_migration);
 }
 
+#[test]
+fn test_migrate_initialises_missing_fields() {
+    // Simulate a frozen older snapshot that lacks keys added in later
+    // schemas, then run migrate and verify deterministic defaults are set.
+    let env = Env::default();
+    let cid = env.register_contract(None, SLACalculatorContract);
+    let client = SLACalculatorContractClient::new(&env, &cid);
+    let admin = soroban_sdk::Address::generate(&env);
+    let op = soroban_sdk::Address::generate(&env);
+    client.initialize(&admin, &op);
+
+    // Remove some keys to emulate an older schema state and force stored
+    // version to 0 so migrate will exercise the v0->v1 path.
+    env.as_contract(&cid, || {
+        env.storage().instance().remove(&CONFIG_KEY);
+        env.storage().instance().remove(&STATS_KEY);
+        env.storage().instance().set(&STORAGE_VERSION_KEY, &0u32);
+    });
+
+    // Run migration as admin
+    client.migrate(&admin);
+
+    // After migrate the keys should exist again and the stored version
+    // should match the binary's STORAGE_VERSION.
+    let version = client.get_storage_version();
+    assert_eq!(version, STORAGE_VERSION);
+
+    env.as_contract(&cid, || {
+        assert!(env.storage().instance().has(&CONFIG_KEY));
+        assert!(env.storage().instance().has(&STATS_KEY));
+    });
+}
+
 // ============================================================
 // SC-011 – Latest result by outage (issue #131) – additional coverage
 // ============================================================