diff --git a/apexchainx_calculator/src/api_stability.rs b/apexchainx_calculator/src/api_stability.rs
index 43a0d69..eae3d82 100644
--- a/apexchainx_calculator/src/api_stability.rs
+++ b/apexchainx_calculator/src/api_stability.rs
@@ -89,7 +89,7 @@ pub fn canonical_field_counts() -> [(&'static str, u32); 31] {
         ("FailureCode", 3),
         ("FailureSchema", 2),
         ("HealthcheckResult", 3),
-        ("ConfigBundle", 2),
+        ("ConfigBundle", 3),
         ("AuditState", 10),
         ("ContractInfo", 11),
         ("HistoryPage", 3),
diff --git a/apexchainx_calculator/src/calculation.rs b/apexchainx_calculator/src/calculation.rs
index 22f45e2..1c85e97 100644
--- a/apexchainx_calculator/src/calculation.rs
+++ b/apexchainx_calculator/src/calculation.rs
@@ -158,6 +158,29 @@ pub fn calculate_sla_view(
     crate::SLACalculatorContract::check_version(env)?;
     let cfg = crate::SLACalculatorContract::load_config(env, &severity)?;
     let config_version_hash = crate::SLACalculatorContract::compute_config_version_hash(env)?;
+
+    let history: Vec<SLAResult> = env
+        .storage()
+        .instance()
+        .get(&HISTORY_KEY)
+        .unwrap_or_else(|| Vec::new(env));
+
+    let mut existing: Option<SLAResult> = None;
+    for i in 0..history.len() {
+        let entry = history.get(i).unwrap();
+        if entry.outage_id == outage_id {
+            existing = Some(entry);
+        }
+    }
+    if let Some(prev) = existing {
+        if prev.config_version_hash == config_version_hash {
+            if prev.mttr_minutes != mttr_minutes || prev.threshold_minutes != cfg.threshold_minutes {
+                return Err(SLAError::DuplicateOutageInput);
+            }
+            return Ok(prev);
+        }
+    }
+
     compute_result(
         outage_id,
         mttr_minutes,
diff --git a/apexchainx_calculator/src/config.rs b/apexchainx_calculator/src/config.rs
index 58503b0..5a663a3 100644
--- a/apexchainx_calculator/src/config.rs
+++ b/apexchainx_calculator/src/config.rs
@@ -8,7 +8,7 @@ use soroban_sdk::{symbol_short, Env, Map, Symbol, Vec};
 
 use crate::{
     config_freeze, config_metadata, SLAConfig, SLAConfigEntry, SLAConfigSnapshot, SLAError, CONFIG_KEY,
-    CUSTOM_CONFIG_KEY, EVENT_CONFIG_UPD, EVENT_VERSION,
+    CONFIG_SNAPSHOT_SCHEMA_VERSION, CUSTOM_CONFIG_KEY, EVENT_CONFIG_UPD, EVENT_VERSION,
 };
 
 /// Sets the SLA configuration for a given severity level.
@@ -75,7 +75,7 @@ pub fn get_config_snapshot(env: &Env) -> Result<SLAConfigSnapshot, SLAError> {
     }
 
     Ok(SLAConfigSnapshot {
-        version: symbol_short!("v1"),
+        version: CONFIG_SNAPSHOT_SCHEMA_VERSION,
         entries,
     })
 }
@@ -201,7 +201,7 @@ pub fn get_custom_config_snapshot(env: &Env) -> Result<SLAConfigSnapshot, SLAErr
     }
 
     Ok(SLAConfigSnapshot {
-        version: symbol_short!("v1"),
+        version: CONFIG_SNAPSHOT_SCHEMA_VERSION,
         entries,
     })
 }
diff --git a/apexchainx_calculator/src/config_bundle.rs b/apexchainx_calculator/src/config_bundle.rs
index de2c9ab..22f156e 100644
--- a/apexchainx_calculator/src/config_bundle.rs
+++ b/apexchainx_calculator/src/config_bundle.rs
@@ -46,6 +46,8 @@ pub struct ConfigBundle {
     pub snapshot: SLAConfigSnapshot,
     /// Result schema descriptor with symbol mappings.
     pub schema: SLAResultSchema,
+    /// Config version hash corresponding to the snapshot for duplicate detection.
+    pub config_version_hash: u64,
 }
 
 #[cfg(test)]
@@ -73,6 +75,12 @@ mod tests {
             bundle.is_some(),
             "ConfigBundle must be available after initialize()",
         );
+        let b = bundle.unwrap();
+        assert_eq!(
+            b.config_version_hash,
+            client.get_config_version_hash(),
+            "ConfigBundle config_version_hash must match get_config_version_hash()",
+        );
     }
 
     #[test]
@@ -126,6 +134,11 @@ mod tests {
         assert_eq!(entry.config.threshold_minutes, 42);
         assert_eq!(entry.config.penalty_per_minute, 111);
         assert_eq!(entry.config.reward_base, 999);
+        assert_eq!(
+            bundle.config_version_hash,
+            client.get_config_version_hash(),
+            "Bundle config_version_hash must update when config changes",
+        );
     }
 
     #[test]
@@ -144,6 +157,7 @@ mod tests {
 
         assert_eq!(a.snapshot, b.snapshot);
         assert_eq!(a.schema, b.schema);
+        assert_eq!(a.config_version_hash, b.config_version_hash);
         assert_eq!(a.snapshot.entries.len(), 4);
         assert_eq!(a.schema.status_met, symbol_short!("met"));
     }
diff --git a/apexchainx_calculator/src/lib.rs b/apexchainx_calculator/src/lib.rs
index e6c885d..a815829 100644
--- a/apexchainx_calculator/src/lib.rs
+++ b/apexchainx_calculator/src/lib.rs
@@ -177,6 +177,19 @@ pub(crate) const RESULT_SCHEMA_VERSION: u32 = 1;
 /// 6. See `docs/result-schema-migration-guard.md` for the full process.
 pub(crate) const RESULT_SCHEMA_FIELD_COUNT: u32 = 9;
 
+/// Version label of the SLAConfigSnapshot schema exposed via get_config_snapshot().
+/// Incremented/bumped when snapshot layout changes in a breaking way.
+pub(crate) const CONFIG_SNAPSHOT_SCHEMA_VERSION: Symbol = symbol_short!("v1");
+
+/// Number of named fields in `SLAConfigSnapshot`.
+///
+/// This constant is the migration guardrail for `SLAConfigSnapshot`.
+/// It must be updated in the same commit that adds or removes a field from
+/// `SLAConfigSnapshot`. The companion test `test_config_snapshot_schema_field_count_sentinel`
+/// in `schema_migration_tests.rs` will fail CI if the struct layout changes
+/// without a corresponding update to this constant and `CONFIG_SNAPSHOT_SCHEMA_VERSION`.
+pub(crate) const CONFIG_SNAPSHOT_SCHEMA_FIELD_COUNT: u32 = 2;
+
 /// Hard upper bound on retained history entries. (SC-062)
 /// Configurable down to 1 via set_retention_limit().
 pub(crate) const MAX_HISTORY_SIZE: u32 = 1000;
@@ -1061,6 +1074,11 @@ impl SLACalculatorContract {
     /// Deploy the contract.
     /// `admin`    – may update config, pause/unpause, and assign the operator.
     /// `operator` – may call `calculate_sla`.
+    ///
+    /// # Role Distinctness & Single-Address Mode
+    /// Both `admin` and `operator` signatures are required at initialization. However, `admin` and
+    /// `operator` may be set to the same address for single-key / merged-role deployments where
+    /// role separation is not required. In this case, both authorization checks are satisfied by a single signature.
     pub fn initialize(env: Env, admin: Address, operator: Address) -> Result<(), SLAError> {
         if env.storage().instance().has(&ADMIN_KEY) {
             return Err(SLAError::AlreadyInitialized);
@@ -1656,7 +1674,7 @@ impl SLACalculatorContract {
         }
 
         Ok(SLAConfigSnapshot {
-            version: symbol_short!("v1"),
+            version: CONFIG_SNAPSHOT_SCHEMA_VERSION,
             entries,
         })
     }
@@ -1700,7 +1718,7 @@ impl SLACalculatorContract {
         }
 
         Ok(SLAConfigSnapshot {
-            version: symbol_short!("v1"),
+            version: CONFIG_SNAPSHOT_SCHEMA_VERSION,
             entries,
         })
     }
@@ -1742,7 +1760,7 @@ impl SLACalculatorContract {
             entries.push_back(SLAConfigEntry { severity, config });
         }
         Ok(SLAConfigSnapshot {
-            version: symbol_short!("v1"),
+            version: CONFIG_SNAPSHOT_SCHEMA_VERSION,
             entries,
         })
     }
@@ -1850,8 +1868,13 @@ impl SLACalculatorContract {
     /// contract is initialised and on the current storage version.
     pub fn get_config_bundle(env: Env) -> Result<Option<ConfigBundle>, SLAError> {
         let snapshot = Self::get_config_snapshot(env.clone())?;
-        let schema = Self::get_result_schema(env)?;
-        Ok(Some(ConfigBundle { snapshot, schema }))
+        let schema = Self::get_result_schema(env.clone())?;
+        let config_version_hash = Self::compute_config_version_hash(&env)?;
+        Ok(Some(ConfigBundle {
+            snapshot,
+            schema,
+            config_version_hash,
+        }))
     }
 
     /// Returns the full audit state including roles, config, stats, and history.
@@ -2224,11 +2247,29 @@ impl SLACalculatorContract {
         let cfg = Self::load_config(&env, &severity)?;
         let config_version_hash = Self::compute_config_version_hash(&env)?;
 
-        // Delegate to pure internal math without mutating state or emitting events.
+        // Apply duplicate/replay policy read-only against recorded history
+        let history: Vec<SLAResult> = env
+            .storage()
+            .instance()
+            .get(&HISTORY_KEY)
+            .unwrap_or_else(|| Vec::new(&env));
+
+        let mut existing: Option<SLAResult> = None;
+        for i in 0..history.len() {
+            let entry = history.get(i).unwrap();
+            if entry.outage_id == outage_id {
+                existing = Some(entry);
+            }
+        }
+        if let Some(prev) = existing {
+            if prev.config_version_hash == config_version_hash {
+                if prev.mttr_minutes != mttr_minutes || prev.threshold_minutes != cfg.threshold_minutes {
+                    return Err(SLAError::DuplicateOutageInput);
+                }
+                return Ok(prev);
+            }
+        }
 
-        // Use the current ledger timestamp so the view result matches the mutating
-        // path for the same inputs executed in the same ledger, while still avoiding
-        // any state writes or event emission.
         Self::compute_result(
             outage_id,
             mttr_minutes,
diff --git a/apexchainx_calculator/src/schema_migration_tests.rs b/apexchainx_calculator/src/schema_migration_tests.rs
index 5461cb5..2a25bd7 100644
--- a/apexchainx_calculator/src/schema_migration_tests.rs
+++ b/apexchainx_calculator/src/schema_migration_tests.rs
@@ -31,7 +31,8 @@
 #[cfg(test)]
 mod tests {
     use crate::{
-        SLACalculatorContract, SLACalculatorContractClient, RESULT_SCHEMA_FIELD_COUNT, RESULT_SCHEMA_VERSION,
+        SLACalculatorContract, SLACalculatorContractClient, CONFIG_SNAPSHOT_SCHEMA_FIELD_COUNT,
+        CONFIG_SNAPSHOT_SCHEMA_VERSION, RESULT_SCHEMA_FIELD_COUNT, RESULT_SCHEMA_VERSION,
     };
     use soroban_sdk::{testutils::Address as _, Env, Symbol};
 
@@ -216,4 +217,32 @@ mod tests {
             panic!("get_config_bundle returned None after initialization");
         }
     }
+
+    // -----------------------------------------------------------------------
+    // SLAConfigSnapshot sentinel: field count must match CONFIG_SNAPSHOT_SCHEMA_FIELD_COUNT
+    // -----------------------------------------------------------------------
+
+    #[test]
+    fn test_config_snapshot_schema_field_count_sentinel() {
+        use crate::SLAConfigSnapshot;
+        use soroban_sdk::{symbol_short, Env, Vec};
+
+        let env = Env::default();
+        let sample = SLAConfigSnapshot {
+            version: CONFIG_SNAPSHOT_SCHEMA_VERSION,
+            entries: Vec::new(&env),
+        };
+
+        let SLAConfigSnapshot {
+            version: _,
+            entries: _,
+        } = sample;
+
+        assert_eq!(
+            CONFIG_SNAPSHOT_SCHEMA_FIELD_COUNT, 2,
+            "CONFIG_SNAPSHOT_SCHEMA_FIELD_COUNT is out of sync with SLAConfigSnapshot. \
+             Update lib.rs::CONFIG_SNAPSHOT_SCHEMA_FIELD_COUNT and \
+             CONFIG_SNAPSHOT_SCHEMA_VERSION when adding or removing fields."
+        );
+    }
 }
diff --git a/apexchainx_calculator/src/tests.rs b/apexchainx_calculator/src/tests.rs
index 32b76b9..50bf1fd 100644
--- a/apexchainx_calculator/src/tests.rs
+++ b/apexchainx_calculator/src/tests.rs
@@ -64,6 +64,32 @@ fn test_initialize_stores_roles() {
     assert_eq!(client.get_operator(), actors.operator);
 }
 
+#[test]
+fn test_initialize_single_address_merged_roles() {
+    let env = Env::default();
+    env.mock_all_auths();
+    let cid = env.register_contract(None, SLACalculatorContract);
+    let client = SLACalculatorContractClient::new(&env, &cid);
+    let single_key = soroban_sdk::Address::generate(&env);
+
+    client.initialize(&single_key, &single_key);
+
+    assert_eq!(client.get_admin(), single_key);
+    assert_eq!(client.get_operator(), single_key);
+
+    // Single key can invoke both admin and operator methods
+    let result = client.calculate_sla(
+        &single_key,
+        &symbol_short!("INC001"),
+        &symbol_short!("critical"),
+        &10,
+    );
+    assert_eq!(result.status, symbol_short!("met"));
+
+    client.set_config(&single_key, &symbol_short!("critical"), &20, &200, &1000);
+    assert_eq!(client.get_config(&symbol_short!("critical")).threshold_minutes, 20);
+}
+
 #[test]
 #[should_panic]
 fn test_double_initialize_fails() {
@@ -5210,6 +5236,46 @@ fn test_invariance_critical_all_rating_zones() {
     }
 }
 
+#[test]
+fn test_calculate_sla_view_detects_duplicate_conflict() {
+    let (_env, client, actors) = setup();
+    let outage_id = symbol_short!("OUTDUP1");
+    let severity = symbol_short!("critical");
+
+    // First, record a calculation via mutating path
+    let res1 = client.calculate_sla(&actors.operator, &outage_id, &severity, &10);
+    assert_eq!(res1.status, symbol_short!("met"));
+
+    // View call with conflicting mttr must return DuplicateOutageInput error
+    let res2 = client.try_calculate_sla_view(&outage_id, &severity, &20);
+    assert_eq!(res2, Err(Ok(SLAError::DuplicateOutageInput)));
+}
+
+#[test]
+fn test_calculate_sla_view_handles_replay() {
+    let (env, client, actors) = setup();
+    env.ledger().set_timestamp(1000);
+    let outage_id = symbol_short!("OUTREP1");
+    let severity = symbol_short!("critical");
+
+    // Record calculation at t = 1000
+    let orig = client.calculate_sla(&actors.operator, &outage_id, &severity, &10);
+    assert_eq!(orig.recorded_at, 1000);
+
+    // Advance time to t = 2000
+    env.ledger().set_timestamp(2000);
+
+    // View call for identical outage_id and mttr must replay stored result with original timestamp (1000)
+    let replayed = client.calculate_sla_view(&outage_id, &severity, &10);
+    assert_eq!(replayed.recorded_at, 1000);
+    assert_eq!(replayed.amount, orig.amount);
+    assert_eq!(replayed.status, orig.status);
+
+    // Assert side-effect free: history count remains 1
+    let history = client.get_history_page(&0, &10);
+    assert_eq!(history.entries.len(), 1);
+}
+
 #[test]
 fn test_invariance_high_all_rating_zones() {
     let (_env, client, actors) = setup();
@@ -8086,6 +8152,7 @@ fn test_240_all_contracttype_structures_round_trip_serialization() {
             deprecated_symbols,
             severity_aliases,
         },
+        config_version_hash: 12345,
     };
     let scval_bundle: soroban_sdk::Val = config_bundle.clone().try_into_val(&env).unwrap();
     let restored_bundle: ConfigBundle = scval_bundle.try_into_val(&env).unwrap();