diff --git a/contracts/atomic_swap/src/lib.rs b/contracts/atomic_swap/src/lib.rs
index 795e656..44e7649 100644
--- a/contracts/atomic_swap/src/lib.rs
+++ b/contracts/atomic_swap/src/lib.rs
@@ -54,6 +54,7 @@ pub enum ContractError {
     SchemaNotGreater = 29,
     MissingFunc = 30,
     FuncChanged = 31,
+    InsufficientReputation = 40,
 }
 
 // ── TTL ───────────────────────────────────────────────────────────────────────
@@ -126,6 +127,10 @@ pub enum DataKey {
     SwapMode(u64),
     /// Escrow: maps swap_id → deposited amount (set when buyer deposits).
     EscrowDeposit(u64),
+    /// Maps address → reputation score (0–100).
+    UserReputation(Address),
+    /// Maps ip_id → minimum buyer reputation required (set by seller per swap).
+    ReputationMultiplier(u64),
 }
 
 // ── Types ─────────────────────────────────────────────────────────────────────
@@ -395,6 +400,24 @@ impl AtomicSwap {
             Self::evaluate_conditions(&env, &swap);
         }
 
+        // Check minimum reputation requirement set by seller
+        if let Some(min_rep) = env
+            .storage()
+            .persistent()
+            .get::<_, u32>(&DataKey::ReputationMultiplier(swap_id))
+        {
+            let buyer_rep = env
+                .storage()
+                .persistent()
+                .get::<_, u32>(&DataKey::UserReputation(swap.buyer.clone()))
+                .unwrap_or(50u32);
+            if buyer_rep < min_rep {
+                env.panic_with_error(Error::from_contract_error(
+                    ContractError::InsufficientReputation as u32,
+                ));
+            }
+        }
+
         // #350: Deposit collateral if required
         if swap.collateral_amount > 0 {
             // Check if collateral already deposited
@@ -602,7 +625,8 @@ impl AtomicSwap {
         }
 
         // #359: Update reputation on completion
-        // reputation::update_reputation_on_completion(&env, &swap.seller, &swap.buyer);
+        Self::update_reputation(&env, &swap.seller, 5);
+        Self::update_reputation(&env, &swap.buyer, 5);
 
         env.events().publish(
             (soroban_sdk::symbol_short!("key_rev"),),
@@ -962,6 +986,9 @@ impl AtomicSwap {
         // #253: Log history entry
         Self::append_history(&env, swap_id, SwapStatus::Cancelled);
 
+        // Update reputation: canceller loses 10 points
+        Self::update_reputation(&env, &canceller, -10);
+
         env.events().publish(
             (soroban_sdk::symbol_short!("swap_cncl"),),
             SwapCancelledEvent { swap_id, canceller },
@@ -1026,6 +1053,9 @@ impl AtomicSwap {
         // #253: Log history entry
         Self::append_history(&env, swap_id, SwapStatus::Cancelled);
 
+        // Seller defaulted (expired without revealing key): seller loses 10 points
+        Self::update_reputation(&env, &swap.seller, -10);
+
         env.events().publish(
             (soroban_sdk::symbol_short!("s_cancel"),),
             SwapCancelledEvent {
@@ -2825,6 +2855,47 @@ impl AtomicSwap {
             SwapCancelledEvent { swap_id, canceller: swap.buyer },
         );
     }
+
+    // ── Reputation ────────────────────────────────────────────────────────────
+
+    /// Returns the reputation score (0–100) for an address. Defaults to 50.
+    pub fn get_reputation(env: Env, address: Address) -> u32 {
+        env.storage()
+            .persistent()
+            .get(&DataKey::UserReputation(address))
+            .unwrap_or(50u32)
+    }
+
+    /// Seller sets a minimum buyer reputation required for a specific swap.
+    /// Must be called by the swap's seller before the buyer accepts.
+    pub fn set_reputation_multiplier(env: Env, swap_id: u64, min_reputation: u32) {
+        let swap = require_swap_exists(&env, swap_id);
+        swap.seller.require_auth();
+        require_swap_status(&env, &swap, SwapStatus::Pending, ContractError::NotPending);
+
+        env.storage()
+            .persistent()
+            .set(&DataKey::ReputationMultiplier(swap_id), &min_reputation);
+        env.storage()
+            .persistent()
+            .extend_ttl(&DataKey::ReputationMultiplier(swap_id), LEDGER_BUMP, LEDGER_BUMP);
+    }
+
+    /// Internal: adjust reputation score, clamped to [0, 100].
+    fn update_reputation(env: &Env, address: &Address, delta: i32) {
+        let current: u32 = env
+            .storage()
+            .persistent()
+            .get(&DataKey::UserReputation(address.clone()))
+            .unwrap_or(50u32);
+        let updated = (current as i32).saturating_add(delta).clamp(0, 100) as u32;
+        env.storage()
+            .persistent()
+            .set(&DataKey::UserReputation(address.clone()), &updated);
+        env.storage()
+            .persistent()
+            .extend_ttl(&DataKey::UserReputation(address.clone()), LEDGER_BUMP, LEDGER_BUMP);
+    }
 }
 
 // ── Tests ─────────────────────────────────────────────────────────────────────
diff --git a/contracts/atomic_swap/src/reputation_tests.rs b/contracts/atomic_swap/src/reputation_tests.rs
new file mode 100644
index 0000000..98a2bc6
--- /dev/null
+++ b/contracts/atomic_swap/src/reputation_tests.rs
@@ -0,0 +1,271 @@
+#[cfg(test)]
+mod reputation_tests {
+    use ip_registry::{IpRegistry, IpRegistryClient};
+    use soroban_sdk::{
+        testutils::{Address as _, Ledger},
+        token::StellarAssetClient,
+        Address, Bytes, BytesN, Env,
+    };
+
+    use crate::{AtomicSwap, AtomicSwapClient, ContractError, SwapStatus};
+
+    // ── Helpers ───────────────────────────────────────────────────────────────
+
+    fn setup_registry(env: &Env, owner: &Address) -> (Address, u64, BytesN<32>, BytesN<32>) {
+        let registry_id = env.register(IpRegistry, ());
+        let registry = IpRegistryClient::new(env, &registry_id);
+
+        let secret = BytesN::from_array(env, &[0xAAu8; 32]);
+        let blinding = BytesN::from_array(env, &[0xBBu8; 32]);
+
+        let mut preimage = Bytes::new(env);
+        preimage.append(&Bytes::from(secret.clone()));
+        preimage.append(&Bytes::from(blinding.clone()));
+        let commitment_hash: BytesN<32> = env.crypto().sha256(&preimage).into();
+
+        let ip_id = registry.commit_ip(owner, &commitment_hash);
+        (registry_id, ip_id, secret, blinding)
+    }
+
+    fn setup_token(env: &Env, admin: &Address, recipient: &Address, amount: i128) -> Address {
+        let token_id = env
+            .register_stellar_asset_contract_v2(admin.clone())
+            .address();
+        StellarAssetClient::new(env, &token_id).mint(recipient, &amount);
+        token_id
+    }
+
+    fn setup_swap_contract(env: &Env, registry_id: &Address) -> Address {
+        let contract_id = env.register(AtomicSwap, ());
+        AtomicSwapClient::new(env, &contract_id).initialize(registry_id);
+        contract_id
+    }
+
+    // ── Tests ─────────────────────────────────────────────────────────────────
+
+    #[test]
+    fn test_default_reputation_is_50() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let seller = Address::generate(&env);
+        let (registry_id, _, _, _) = setup_registry(&env, &seller);
+        let contract_id = setup_swap_contract(&env, &registry_id);
+        let client = AtomicSwapClient::new(&env, &contract_id);
+
+        let unknown = Address::generate(&env);
+        assert_eq!(client.get_reputation(&unknown), 50);
+    }
+
+    #[test]
+    fn test_reputation_increases_on_successful_swap() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let seller = Address::generate(&env);
+        let buyer = Address::generate(&env);
+        let (registry_id, ip_id, secret, blinding) = setup_registry(&env, &seller);
+        let token_id = setup_token(&env, &seller, &buyer, 1_000_000);
+        let contract_id = setup_swap_contract(&env, &registry_id);
+        let client = AtomicSwapClient::new(&env, &contract_id);
+
+        let swap_id = client.initiate_swap(
+            &token_id, &ip_id, &seller, &1000i128, &buyer,
+            &0u32, &None, &0i128, &false,
+        );
+        client.accept_swap(&swap_id);
+        client.reveal_key(&swap_id, &seller, &secret, &blinding);
+
+        assert_eq!(client.get_reputation(&seller), 55);
+        assert_eq!(client.get_reputation(&buyer), 55);
+    }
+
+    #[test]
+    fn test_reputation_decreases_on_cancel_swap() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let seller = Address::generate(&env);
+        let buyer = Address::generate(&env);
+        let (registry_id, ip_id, _, _) = setup_registry(&env, &seller);
+        let token_id = setup_token(&env, &seller, &buyer, 1_000_000);
+        let contract_id = setup_swap_contract(&env, &registry_id);
+        let client = AtomicSwapClient::new(&env, &contract_id);
+
+        let swap_id = client.initiate_swap(
+            &token_id, &ip_id, &seller, &1000i128, &buyer,
+            &0u32, &None, &0i128, &false,
+        );
+        client.cancel_swap(&swap_id, &seller);
+
+        assert_eq!(client.get_reputation(&seller), 40);
+    }
+
+    #[test]
+    fn test_reputation_decreases_on_cancel_expired_swap() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let seller = Address::generate(&env);
+        let buyer = Address::generate(&env);
+        let (registry_id, ip_id, _, _) = setup_registry(&env, &seller);
+        let token_id = setup_token(&env, &seller, &buyer, 1_000_000);
+        let contract_id = setup_swap_contract(&env, &registry_id);
+        let client = AtomicSwapClient::new(&env, &contract_id);
+
+        let swap_id = client.initiate_swap(
+            &token_id, &ip_id, &seller, &1000i128, &buyer,
+            &0u32, &None, &0i128, &false,
+        );
+        client.accept_swap(&swap_id);
+
+        // Advance time past expiry (7 days + 1)
+        env.ledger().with_mut(|l| l.timestamp += 604801);
+
+        client.cancel_expired_swap(&swap_id, &buyer);
+
+        // Seller defaulted: seller loses 10 points
+        assert_eq!(client.get_reputation(&seller), 40);
+    }
+
+    #[test]
+    fn test_reputation_clamped_at_zero() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let seller = Address::generate(&env);
+        let buyer = Address::generate(&env);
+        let (registry_id, ip_id, _, _) = setup_registry(&env, &seller);
+        let token_id = setup_token(&env, &seller, &buyer, 1_000_000);
+        let contract_id = setup_swap_contract(&env, &registry_id);
+        let client = AtomicSwapClient::new(&env, &contract_id);
+
+        // Cancel 6 times to drive reputation from 50 down to 0 (50 - 6*10 = -10 → clamped 0)
+        for i in 0..6u64 {
+            // Need a fresh IP for each swap since active swap lock is released on cancel
+            let registry = IpRegistryClient::new(&env, &registry_id);
+            let secret = BytesN::from_array(&env, &[(i as u8) + 1; 32]);
+            let blinding = BytesN::from_array(&env, &[(i as u8) + 0x80; 32]);
+            let mut preimage = Bytes::new(&env);
+            preimage.append(&Bytes::from(secret.clone()));
+            preimage.append(&Bytes::from(blinding.clone()));
+            let hash: BytesN<32> = env.crypto().sha256(&preimage).into();
+            let ip_id_i = registry.commit_ip(&seller, &hash);
+
+            let swap_id = client.initiate_swap(
+                &token_id, &ip_id_i, &seller, &100i128, &buyer,
+                &0u32, &None, &0i128, &false,
+            );
+            client.cancel_swap(&swap_id, &seller);
+        }
+
+        assert_eq!(client.get_reputation(&seller), 0);
+        let _ = ip_id; // suppress unused warning
+    }
+
+    #[test]
+    fn test_reputation_clamped_at_100() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let seller = Address::generate(&env);
+        let buyer = Address::generate(&env);
+        let (registry_id, ip_id, secret, blinding) = setup_registry(&env, &seller);
+        let token_id = setup_token(&env, &seller, &buyer, 10_000_000);
+        let contract_id = setup_swap_contract(&env, &registry_id);
+        let client = AtomicSwapClient::new(&env, &contract_id);
+
+        // Complete 10 swaps: 50 + 10*5 = 100
+        let registry = IpRegistryClient::new(&env, &registry_id);
+        for i in 0..10u64 {
+            let s = BytesN::from_array(&env, &[(i as u8) + 1; 32]);
+            let b = BytesN::from_array(&env, &[(i as u8) + 0x80; 32]);
+            let mut preimage = Bytes::new(&env);
+            preimage.append(&Bytes::from(s.clone()));
+            preimage.append(&Bytes::from(b.clone()));
+            let hash: BytesN<32> = env.crypto().sha256(&preimage).into();
+            let ip_id_i = registry.commit_ip(&seller, &hash);
+
+            let swap_id = client.initiate_swap(
+                &token_id, &ip_id_i, &seller, &100i128, &buyer,
+                &0u32, &None, &0i128, &false,
+            );
+            client.accept_swap(&swap_id);
+            client.reveal_key(&swap_id, &seller, &s, &b);
+        }
+
+        assert_eq!(client.get_reputation(&seller), 100);
+        let _ = (ip_id, secret, blinding);
+    }
+
+    #[test]
+    fn test_set_reputation_multiplier_enforced() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let seller = Address::generate(&env);
+        let buyer = Address::generate(&env);
+        let (registry_id, ip_id, _, _) = setup_registry(&env, &seller);
+        let token_id = setup_token(&env, &seller, &buyer, 1_000_000);
+        let contract_id = setup_swap_contract(&env, &registry_id);
+        let client = AtomicSwapClient::new(&env, &contract_id);
+
+        let swap_id = client.initiate_swap(
+            &token_id, &ip_id, &seller, &1000i128, &buyer,
+            &0u32, &None, &0i128, &false,
+        );
+
+        // Seller requires buyer reputation ≥ 80; buyer has default 50
+        client.set_reputation_multiplier(&swap_id, &80u32);
+
+        let result = client.try_accept_swap(&swap_id);
+        assert!(
+            result.is_err(),
+            "accept_swap must fail when buyer reputation is below minimum"
+        );
+    }
+
+    #[test]
+    fn test_set_reputation_multiplier_passes_when_met() {
+        let env = Env::default();
+        env.mock_all_auths();
+
+        let seller = Address::generate(&env);
+        let buyer = Address::generate(&env);
+        let (registry_id, ip_id, secret, blinding) = setup_registry(&env, &seller);
+        let token_id = setup_token(&env, &seller, &buyer, 1_000_000);
+        let contract_id = setup_swap_contract(&env, &registry_id);
+        let client = AtomicSwapClient::new(&env, &contract_id);
+
+        // Boost buyer reputation to 55 via a prior successful swap
+        let registry = IpRegistryClient::new(&env, &registry_id);
+        let s2 = BytesN::from_array(&env, &[0x11u8; 32]);
+        let b2 = BytesN::from_array(&env, &[0x22u8; 32]);
+        let mut preimage = Bytes::new(&env);
+        preimage.append(&Bytes::from(s2.clone()));
+        preimage.append(&Bytes::from(b2.clone()));
+        let hash2: BytesN<32> = env.crypto().sha256(&preimage).into();
+        let ip_id2 = registry.commit_ip(&seller, &hash2);
+
+        let swap_id2 = client.initiate_swap(
+            &token_id, &ip_id2, &seller, &100i128, &buyer,
+            &0u32, &None, &0i128, &false,
+        );
+        client.accept_swap(&swap_id2);
+        client.reveal_key(&swap_id2, &seller, &s2, &b2);
+        // buyer reputation is now 55
+
+        // Now initiate the real swap with min_reputation = 55
+        let swap_id = client.initiate_swap(
+            &token_id, &ip_id, &seller, &1000i128, &buyer,
+            &0u32, &None, &0i128, &false,
+        );
+        client.set_reputation_multiplier(&swap_id, &55u32);
+
+        // Should succeed
+        client.accept_swap(&swap_id);
+        let swap = client.get_swap(&swap_id).unwrap();
+        assert_eq!(swap.status, SwapStatus::Accepted);
+        let _ = (secret, blinding);
+    }
+}