diff --git a/contracts/teachlink/src/errors.rs b/contracts/teachlink/src/errors.rs
index 8adb6d6..7e5fa67 100644
--- a/contracts/teachlink/src/errors.rs
+++ b/contracts/teachlink/src/errors.rs
@@ -55,6 +55,8 @@ pub enum BridgeError {
     RetryLimitExceeded = 140,
     RetryBackoffActive = 141,
     BridgeTransactionFailed = 142,
+    IncompatibleInterfaceVersion = 143,
+    InvalidInterfaceVersionRange = 144,
 }
 
 /// Escrow module errors
@@ -67,7 +69,6 @@ pub enum EscrowError {
     RefundTimeMustBeInFuture = 203,
     RefundTimeMustBeAfterReleaseTime = 204,
     DuplicateSigner = 205,
-    DuplicateSigners = 205,  // Alias for consistency
     SignerNotAuthorized = 206,
     SignerAlreadyApproved = 207,
     CallerNotAuthorized = 208,
diff --git a/contracts/teachlink/src/interface_versioning.rs b/contracts/teachlink/src/interface_versioning.rs
new file mode 100644
index 0000000..6da5c97
--- /dev/null
+++ b/contracts/teachlink/src/interface_versioning.rs
@@ -0,0 +1,147 @@
+use crate::errors::BridgeError;
+use crate::storage::{ADMIN, INTERFACE_VERSION, MIN_COMPAT_INTERFACE_VERSION};
+use crate::types::{ContractSemVer, InterfaceVersionStatus};
+use soroban_sdk::{Address, Env};
+
+pub const DEFAULT_INTERFACE_VERSION: ContractSemVer = ContractSemVer::new(1, 0, 0);
+pub const DEFAULT_MIN_COMPAT_INTERFACE_VERSION: ContractSemVer = ContractSemVer::new(1, 0, 0);
+
+pub struct InterfaceVersioning;
+
+impl InterfaceVersioning {
+    pub fn initialize(env: &Env) {
+        if !env.storage().instance().has(&INTERFACE_VERSION) {
+            env.storage()
+                .instance()
+                .set(&INTERFACE_VERSION, &DEFAULT_INTERFACE_VERSION);
+        }
+
+        if !env.storage().instance().has(&MIN_COMPAT_INTERFACE_VERSION) {
+            env.storage().instance().set(
+                &MIN_COMPAT_INTERFACE_VERSION,
+                &DEFAULT_MIN_COMPAT_INTERFACE_VERSION,
+            );
+        }
+    }
+
+    pub fn get_interface_version(env: &Env) -> ContractSemVer {
+        env.storage()
+            .instance()
+            .get(&INTERFACE_VERSION)
+            .unwrap_or(DEFAULT_INTERFACE_VERSION)
+    }
+
+    pub fn get_minimum_compatible_interface_version(env: &Env) -> ContractSemVer {
+        env.storage()
+            .instance()
+            .get(&MIN_COMPAT_INTERFACE_VERSION)
+            .unwrap_or(DEFAULT_MIN_COMPAT_INTERFACE_VERSION)
+    }
+
+    pub fn get_interface_version_status(env: &Env) -> InterfaceVersionStatus {
+        InterfaceVersionStatus {
+            current: Self::get_interface_version(env),
+            minimum_compatible: Self::get_minimum_compatible_interface_version(env),
+        }
+    }
+
+    pub fn set_interface_versions(
+        env: &Env,
+        current: ContractSemVer,
+        minimum_compatible: ContractSemVer,
+    ) -> Result<(), BridgeError> {
+        Self::require_admin_auth(env);
+        Self::validate_range(&current, &minimum_compatible)?;
+
+        env.storage().instance().set(&INTERFACE_VERSION, &current);
+        env.storage()
+            .instance()
+            .set(&MIN_COMPAT_INTERFACE_VERSION, &minimum_compatible);
+
+        Ok(())
+    }
+
+    #[must_use]
+    pub fn is_interface_compatible(env: &Env, client_version: ContractSemVer) -> bool {
+        let status = Self::get_interface_version_status(env);
+
+        client_version.major == status.current.major
+            && !client_version.is_lower_than(&status.minimum_compatible)
+            && !client_version.is_greater_than(&status.current)
+    }
+
+    pub fn assert_interface_compatible(
+        env: &Env,
+        client_version: ContractSemVer,
+    ) -> Result<(), BridgeError> {
+        if Self::is_interface_compatible(env, client_version) {
+            Ok(())
+        } else {
+            Err(BridgeError::IncompatibleInterfaceVersion)
+        }
+    }
+
+    fn require_admin_auth(env: &Env) {
+        let admin: Address = env.storage().instance().get(&ADMIN).unwrap();
+        admin.require_auth();
+    }
+
+    fn validate_range(
+        current: &ContractSemVer,
+        minimum_compatible: &ContractSemVer,
+    ) -> Result<(), BridgeError> {
+        if minimum_compatible.major != current.major {
+            return Err(BridgeError::InvalidInterfaceVersionRange);
+        }
+
+        if minimum_compatible.is_greater_than(current) {
+            return Err(BridgeError::InvalidInterfaceVersionRange);
+        }
+
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{InterfaceVersioning, DEFAULT_INTERFACE_VERSION};
+    use crate::types::ContractSemVer;
+    use crate::TeachLinkBridge;
+    use soroban_sdk::testutils::Address as _;
+    use soroban_sdk::{Address, Env};
+
+    #[test]
+    fn compatibility_requires_same_major_and_supported_range() {
+        let env = Env::default();
+        let contract_id = env.register(TeachLinkBridge, ());
+
+        let token_admin = Address::generate(&env);
+        let sac = env.register_stellar_asset_contract_v2(token_admin);
+        let token = sac.address();
+        let admin = Address::generate(&env);
+        let fee_recipient = Address::generate(&env);
+
+        let client = crate::TeachLinkBridgeClient::new(&env, &contract_id);
+        env.mock_all_auths();
+        client.initialize(&token, &admin, &1, &fee_recipient);
+
+        assert!(env.as_contract(&contract_id, || {
+            InterfaceVersioning::is_interface_compatible(&env, ContractSemVer::new(1, 0, 0))
+        }));
+        assert!(!env.as_contract(&contract_id, || {
+            InterfaceVersioning::is_interface_compatible(&env, ContractSemVer::new(2, 0, 0))
+        }));
+    }
+
+    #[test]
+    fn defaults_are_available_before_explicit_initialization() {
+        let env = Env::default();
+        let contract_id = env.register(TeachLinkBridge, ());
+
+        let version = env.as_contract(&contract_id, || {
+            InterfaceVersioning::get_interface_version(&env)
+        });
+
+        assert_eq!(version, DEFAULT_INTERFACE_VERSION);
+    }
+}
diff --git a/contracts/teachlink/src/lib.rs b/contracts/teachlink/src/lib.rs
index c2fe749..a0c6136 100644
--- a/contracts/teachlink/src/lib.rs
+++ b/contracts/teachlink/src/lib.rs
@@ -103,6 +103,7 @@ mod escrow;
 mod escrow_analytics;
 mod events;
 mod insurance;
+mod interface_versioning;
 // FUTURE: Implement governance module (tracked in TRACKING.md)
 // mod governance;
 // mod learning_paths;
@@ -114,10 +115,7 @@ mod notification;
 mod notification_events_basic;
 // mod content_quality;
 mod backup;
-// NOTE: notification_tests is temporarily excluded from the default lib test suite
-// because it uses direct storage access patterns incompatible with the current
-// Soroban SDK test runtime without additional env.as_contract wrappers.
-// mod notification_tests;
+mod notification_tests;
 mod notification_types;
 mod performance;
 pub mod property_based_tests;
@@ -146,15 +144,15 @@ pub use types::{
     AlertConditionType, AlertRule, ArbitratorProfile, AtomicSwap, AuditRecord, BackupManifest,
     BackupSchedule, BridgeMetrics, BridgeProposal, BridgeTransaction, CachedBridgeSummary,
     ChainConfig, ChainMetrics, ComplianceReport, ConsensusState, ContentMetadata, ContentToken,
-    ContentTokenParameters, ContentType, CrossChainMessage, CrossChainPacket, DashboardAnalytics,
-    DisputeOutcome, EmergencyState, Escrow, EscrowMetrics, EscrowParameters, EscrowRole,
-    EscrowSigner, EscrowStatus, LiquidityPool, MultiChainAsset, NotificationChannel,
-    NotificationContent, NotificationPreference, NotificationSchedule, NotificationTemplate,
-    NotificationTracking, OperationType, PacketStatus, ProposalStatus, ProvenanceRecord,
-    RecoveryRecord, ReportComment, ReportSchedule, ReportSnapshot, ReportTemplate, ReportType,
-    ReportUsage, RewardRate, RewardType, RtoTier, SlashingReason, SlashingRecord, SwapStatus,
-    TransferType, UserNotificationSettings, UserReputation, UserReward, ValidatorInfo,
-    ValidatorReward, ValidatorSignature, VisualizationDataPoint,
+    ContentTokenParameters, ContentType, ContractSemVer, CrossChainMessage, CrossChainPacket,
+    DashboardAnalytics, DisputeOutcome, EmergencyState, Escrow, EscrowMetrics, EscrowParameters,
+    EscrowRole, EscrowSigner, EscrowStatus, InterfaceVersionStatus, LiquidityPool, MultiChainAsset,
+    NotificationChannel, NotificationContent, NotificationPreference, NotificationSchedule,
+    NotificationTemplate, NotificationTracking, OperationType, PacketStatus, ProposalStatus,
+    ProvenanceRecord, RecoveryRecord, ReportComment, ReportSchedule, ReportSnapshot,
+    ReportTemplate, ReportType, ReportUsage, RewardRate, RewardType, RtoTier, SlashingReason,
+    SlashingRecord, SwapStatus, TransferType, UserNotificationSettings, UserReputation, UserReward,
+    ValidatorInfo, ValidatorReward, ValidatorSignature, VisualizationDataPoint,
 };
 
 /// TeachLink main contract.
@@ -174,7 +172,9 @@ impl TeachLinkBridge {
         min_validators: u32,
         fee_recipient: Address,
     ) -> Result<(), BridgeError> {
-        bridge::Bridge::initialize(&env, token, admin, min_validators, fee_recipient)
+        bridge::Bridge::initialize(&env, token, admin, min_validators, fee_recipient)?;
+        interface_versioning::InterfaceVersioning::initialize(&env);
+        Ok(())
     }
 
     /// Bridge tokens out to another chain (lock/burn tokens on Stellar)
@@ -253,6 +253,47 @@ impl TeachLinkBridge {
 
     // ========== View Functions ==========
 
+    /// Get full interface version status (current and minimum compatible version)
+    pub fn get_interface_version_status(env: Env) -> InterfaceVersionStatus {
+        interface_versioning::InterfaceVersioning::get_interface_version_status(&env)
+    }
+
+    /// Get current interface semantic version
+    pub fn get_interface_version(env: Env) -> ContractSemVer {
+        interface_versioning::InterfaceVersioning::get_interface_version(&env)
+    }
+
+    /// Get minimum supported interface semantic version
+    pub fn get_min_compat_interface_version(env: Env) -> ContractSemVer {
+        interface_versioning::InterfaceVersioning::get_minimum_compatible_interface_version(&env)
+    }
+
+    /// Update current and minimum compatible interface versions (admin only)
+    pub fn set_interface_version(
+        env: Env,
+        current: ContractSemVer,
+        minimum_compatible: ContractSemVer,
+    ) -> Result<(), BridgeError> {
+        interface_versioning::InterfaceVersioning::set_interface_versions(
+            &env,
+            current,
+            minimum_compatible,
+        )
+    }
+
+    /// Validate whether a client interface version is compatible
+    pub fn is_interface_compatible(env: Env, client_version: ContractSemVer) -> bool {
+        interface_versioning::InterfaceVersioning::is_interface_compatible(&env, client_version)
+    }
+
+    /// Assert interface compatibility and return an explicit error if incompatible
+    pub fn assert_interface_compatible(
+        env: Env,
+        client_version: ContractSemVer,
+    ) -> Result<(), BridgeError> {
+        interface_versioning::InterfaceVersioning::assert_interface_compatible(&env, client_version)
+    }
+
     /// Get the bridge transaction by nonce
     pub fn get_bridge_transaction(env: Env, nonce: u64) -> Option<BridgeTransaction> {
         bridge::Bridge::get_bridge_transaction(&env, nonce)
diff --git a/contracts/teachlink/src/storage.rs b/contracts/teachlink/src/storage.rs
index db408c0..44a74b1 100644
--- a/contracts/teachlink/src/storage.rs
+++ b/contracts/teachlink/src/storage.rs
@@ -14,6 +14,8 @@ pub const BRIDGE_FEE: Symbol = symbol_short!("bridgefee");
 pub const BRIDGE_RETRY_COUNTS: Symbol = symbol_short!("br_rtryc");
 pub const BRIDGE_LAST_RETRY: Symbol = symbol_short!("br_lstry");
 pub const BRIDGE_FAILURES: Symbol = symbol_short!("br_fails");
+pub const INTERFACE_VERSION: Symbol = symbol_short!("if_ver");
+pub const MIN_COMPAT_INTERFACE_VERSION: Symbol = symbol_short!("if_minv");
 
 // ========== Advanced Bridge Storage Keys ==========
 
diff --git a/contracts/teachlink/src/types.rs b/contracts/teachlink/src/types.rs
index 812560a..3f9e13c 100644
--- a/contracts/teachlink/src/types.rs
+++ b/contracts/teachlink/src/types.rs
@@ -7,6 +7,44 @@ use soroban_sdk::{contracttype, panic_with_error, Address, Bytes, Map, String, S
 // Include notification types
 pub use crate::notification_types::*;
 
+// ========== Interface Versioning Types ==========
+
+#[contracttype]
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct ContractSemVer {
+    pub major: u32,
+    pub minor: u32,
+    pub patch: u32,
+}
+
+impl ContractSemVer {
+    #[must_use]
+    pub const fn new(major: u32, minor: u32, patch: u32) -> Self {
+        Self {
+            major,
+            minor,
+            patch,
+        }
+    }
+
+    #[must_use]
+    pub fn is_lower_than(&self, other: &Self) -> bool {
+        (self.major, self.minor, self.patch) < (other.major, other.minor, other.patch)
+    }
+
+    #[must_use]
+    pub fn is_greater_than(&self, other: &Self) -> bool {
+        (self.major, self.minor, self.patch) > (other.major, other.minor, other.patch)
+    }
+}
+
+#[contracttype]
+#[derive(Clone, Debug, Eq, PartialEq)]
+pub struct InterfaceVersionStatus {
+    pub current: ContractSemVer,
+    pub minimum_compatible: ContractSemVer,
+}
+
 // ========== Chain Configuration Types ==========
 
 #[contracttype]
diff --git a/contracts/teachlink/tests/test_interface_versioning.rs b/contracts/teachlink/tests/test_interface_versioning.rs
new file mode 100644
index 0000000..9563f5d
--- /dev/null
+++ b/contracts/teachlink/tests/test_interface_versioning.rs
@@ -0,0 +1,66 @@
+#![allow(clippy::needless_pass_by_value)]
+
+use soroban_sdk::testutils::Address as _;
+use soroban_sdk::{Address, Env};
+use teachlink_contract::{ContractSemVer, TeachLinkBridge, TeachLinkBridgeClient};
+
+fn setup_client(env: &Env) -> (TeachLinkBridgeClient<'_>, Address, Address, Address) {
+    let contract_id = env.register(TeachLinkBridge, ());
+    let client = TeachLinkBridgeClient::new(env, &contract_id);
+
+    let token_admin = Address::generate(env);
+    let sac = env.register_stellar_asset_contract_v2(token_admin);
+    let token = sac.address();
+
+    let admin = Address::generate(env);
+    let fee_recipient = Address::generate(env);
+
+    env.mock_all_auths();
+    client.initialize(&token, &admin, &1, &fee_recipient);
+
+    (client, token, admin, fee_recipient)
+}
+
+#[test]
+fn interface_version_defaults_follow_semver() {
+    let env = Env::default();
+    let (client, _, _, _) = setup_client(&env);
+
+    let status = client.get_interface_version_status();
+
+    assert_eq!(status.current, ContractSemVer::new(1, 0, 0));
+    assert_eq!(status.minimum_compatible, ContractSemVer::new(1, 0, 0));
+    assert!(client.is_interface_compatible(&ContractSemVer::new(1, 0, 0)));
+    assert!(!client.is_interface_compatible(&ContractSemVer::new(2, 0, 0)));
+}
+
+#[test]
+fn interface_version_range_enforces_compatibility_window() {
+    let env = Env::default();
+    let (client, _, _, _) = setup_client(&env);
+
+    env.mock_all_auths();
+    client.set_interface_version(&ContractSemVer::new(1, 3, 0), &ContractSemVer::new(1, 1, 0));
+
+    assert!(!client.is_interface_compatible(&ContractSemVer::new(1, 0, 9)));
+    assert!(client.is_interface_compatible(&ContractSemVer::new(1, 1, 0)));
+    assert!(client.is_interface_compatible(&ContractSemVer::new(1, 2, 5)));
+    assert!(client.is_interface_compatible(&ContractSemVer::new(1, 3, 0)));
+    assert!(!client.is_interface_compatible(&ContractSemVer::new(1, 3, 1)));
+    assert!(!client.is_interface_compatible(&ContractSemVer::new(2, 0, 0)));
+}
+
+#[test]
+fn interface_version_rejects_invalid_ranges() {
+    let env = Env::default();
+    let (client, _, _, _) = setup_client(&env);
+
+    env.mock_all_auths();
+    let invalid_major = client
+        .try_set_interface_version(&ContractSemVer::new(2, 0, 0), &ContractSemVer::new(1, 9, 9));
+    assert!(invalid_major.is_err());
+
+    let invalid_order = client
+        .try_set_interface_version(&ContractSemVer::new(1, 1, 0), &ContractSemVer::new(1, 2, 0));
+    assert!(invalid_order.is_err());
+}
diff --git a/docs/versions/CONTRACT_INTERFACE_VERSIONING.md b/docs/versions/CONTRACT_INTERFACE_VERSIONING.md
new file mode 100644
index 0000000..7a8ec6c
--- /dev/null
+++ b/docs/versions/CONTRACT_INTERFACE_VERSIONING.md
@@ -0,0 +1,75 @@
+# Contract Interface Versioning Strategy
+
+This document defines the TeachLink contract interface versioning system for compatibility management.
+
+## Scope
+
+This policy covers public contract entry points exposed by `TeachLinkBridge` and consumed by off-chain clients, SDKs, and indexers.
+
+## Semantic Versioning Model
+
+TeachLink uses semantic versioning (`MAJOR.MINOR.PATCH`) for interface compatibility:
+
+- `MAJOR`: breaking interface changes.
+- `MINOR`: backward-compatible interface additions.
+- `PATCH`: backward-compatible fixes and clarifications.
+
+Contract version values are represented on-chain as:
+
+- `current`: the latest contract interface version.
+- `minimum_compatible`: the oldest client interface version supported by the deployed contract.
+
+## Compatibility Rules
+
+A client version is compatible only when all conditions hold:
+
+1. `client.major == current.major`
+2. `client >= minimum_compatible`
+3. `client <= current`
+
+If any condition fails, the contract reports incompatibility.
+
+## On-Chain Interface Methods
+
+The contract exposes explicit interface version controls:
+
+- `get_interface_version_status()`
+- `get_interface_version()`
+- `get_min_compat_interface_version()`
+- `is_interface_compatible(client_version)`
+- `assert_interface_compatible(client_version)`
+- `set_interface_version(current, minimum_compatible)` (admin only)
+
+## Upgrade Policy
+
+When deploying interface changes:
+
+1. Decide version bump type (`MAJOR`, `MINOR`, or `PATCH`).
+2. Set `current` to the new semantic version.
+3. Set `minimum_compatible` to the oldest client version guaranteed to work.
+4. Keep `minimum_compatible.major == current.major`.
+5. Ensure `minimum_compatible <= current`.
+6. Run compatibility tests before release.
+
+## Backward Compatibility Guarantees
+
+- Minor and patch releases must not break clients between `minimum_compatible` and `current`.
+- Breaking changes require a major bump and corresponding client migration guidance.
+- Contracts must reject impossible compatibility windows (for example, mismatched major versions).
+
+## Operational Guidance
+
+- SDKs should query `get_interface_version_status()` at startup.
+- Clients should fail fast when outside the compatible window.
+- Indexers should track interface versions per deployment and chain.
+
+## Testing Requirements
+
+Versioning tests must cover:
+
+- Default version state after initialization.
+- Positive compatibility at lower/upper boundary versions.
+- Rejection of below-minimum versions.
+- Rejection of higher-than-current versions.
+- Rejection of different major versions.
+- Rejection of invalid admin updates (`minimum_compatible > current` or major mismatch).
diff --git a/docs/versions/README.md b/docs/versions/README.md
index 462e2ec..b441d53 100644
--- a/docs/versions/README.md
+++ b/docs/versions/README.md
@@ -86,3 +86,4 @@ See [CHANGELOG.md](./CHANGELOG.md) for detailed version history.
 ---
 
 *For API versioning, see [API_REFERENCE.md](../API_REFERENCE.md)*
+*For on-chain interface compatibility policy, see [CONTRACT_INTERFACE_VERSIONING.md](./CONTRACT_INTERFACE_VERSIONING.md)*