diff --git a/polkadot/runtime/test-runtime/src/lib.rs b/polkadot/runtime/test-runtime/src/lib.rs
index 6901278dbb2f6..efa8bdd141300 100644
--- a/polkadot/runtime/test-runtime/src/lib.rs
+++ b/polkadot/runtime/test-runtime/src/lib.rs
@@ -323,8 +323,8 @@ impl pallet_session::Config for Runtime {
 }
 
 impl pallet_session::historical::Config for Runtime {
-	type FullIdentification = ();
-	type FullIdentificationOf = pallet_staking::NullIdentity;
+	type FullIdentification = pallet_staking::Existence;
+	type FullIdentificationOf = pallet_staking::ExistenceOf<Runtime>;
 }
 
 pallet_staking_reward_curve::build! {
diff --git a/polkadot/runtime/westend/src/lib.rs b/polkadot/runtime/westend/src/lib.rs
index f63ee8e4fb20a..80d3fa139bbe8 100644
--- a/polkadot/runtime/westend/src/lib.rs
+++ b/polkadot/runtime/westend/src/lib.rs
@@ -537,8 +537,8 @@ impl pallet_session::Config for Runtime {
 }
 
 impl pallet_session::historical::Config for Runtime {
-	type FullIdentification = pallet_staking::Exposure<AccountId, Balance>;
-	type FullIdentificationOf = pallet_staking::ExposureOf<Runtime>;
+	type FullIdentification = pallet_staking::ExistenceOrLegacyExposure<AccountId, Balance>;
+	type FullIdentificationOf = pallet_staking::ExistenceOrLegacyExposureOf<Runtime>;
 }
 
 pub struct MaybeSignedPhase;
diff --git a/prdoc/pr_7936.prdoc b/prdoc/pr_7936.prdoc
new file mode 100644
index 0000000000000..946de516acb83
--- /dev/null
+++ b/prdoc/pr_7936.prdoc
@@ -0,0 +1,55 @@
+title: 'Replace Validator FullIdentification from `Exposure` to `Existence`'
+doc:
+- audience: Runtime Dev
+  description: |-
+    This introduces a new type in `pallet-staking`, `ExistenceOf`, which replaces `ExposureOf`.
+    With this change, runtimes can be configured to identify a validator solely by their presence,
+    rather than using full exposure data.
+
+    This is particularly useful when configuring historical sessions, for example:
+
+    ```rust
+    impl pallet_session::historical::Config for Runtime {
+      type FullIdentification = pallet_staking::Existence;
+      type FullIdentificationOf = pallet_staking::ExistenceOf<Runtime>;
+    }
+    ```
+
+    However, for existing runtimes that depend on the `Exposure` type for `pallet-offences` - often configured like this:
+
+    ```rust
+    impl pallet_offences::Config for Runtime {
+      ...
+      type IdentificationTuple = pallet_session::historical::IdentificationTuple<Self>;
+    }
+    ```
+
+    Where `IdentificationTuple` is defined as:
+    ```rust
+    pub type IdentificationTuple<T> = (<T as pallet_session::Config>::ValidatorId, <T as Config>::FullIdentification);
+    ```
+
+    You should use `ExistenceOrLegacyExposureOf` instead. This type includes a custom encoder/decoder that supports both
+    the legacy `Exposure` type and the new `Existence` type.
+
+    This compatibility layer is necessary because `pallet-offences` stores the `FullIdentification` type in its storage.
+    If you replace `FullIdentification` with `Existence` directly, any previously stored items using `Exposure` will
+    fail to decode. `ExistenceOrLegacyExposureOf` ensures backward compatibility after this change.
+
+crates:
+- name: pallet-babe
+  bump: patch
+- name: pallet-beefy
+  bump: patch
+- name: pallet-grandpa
+  bump: patch
+- name: pallet-offences-benchmarking
+  bump: patch
+- name: pallet-root-offences
+  bump: patch
+- name: pallet-session-benchmarking
+  bump: patch
+- name: pallet-staking
+  bump: major
+- name: westend-runtime
+  bump: minor
diff --git a/substrate/bin/node/runtime/src/lib.rs b/substrate/bin/node/runtime/src/lib.rs
index 3a0c2e13c823f..d0a9c667fbb23 100644
--- a/substrate/bin/node/runtime/src/lib.rs
+++ b/substrate/bin/node/runtime/src/lib.rs
@@ -693,8 +693,8 @@ impl pallet_session::Config for Runtime {
 }
 
 impl pallet_session::historical::Config for Runtime {
-	type FullIdentification = ();
-	type FullIdentificationOf = pallet_staking::NullIdentity;
+	type FullIdentification = pallet_staking::Existence;
+	type FullIdentificationOf = pallet_staking::ExistenceOf<Runtime>;
 }
 
 pallet_staking_reward_curve::build! {
diff --git a/substrate/frame/babe/src/mock.rs b/substrate/frame/babe/src/mock.rs
index c51ddeb9ab9cd..cfbbbf5dd0e18 100644
--- a/substrate/frame/babe/src/mock.rs
+++ b/substrate/frame/babe/src/mock.rs
@@ -105,8 +105,8 @@ impl pallet_session::Config for Test {
 }
 
 impl pallet_session::historical::Config for Test {
-	type FullIdentification = ();
-	type FullIdentificationOf = pallet_staking::NullIdentity;
+	type FullIdentification = pallet_staking::Existence;
+	type FullIdentificationOf = pallet_staking::ExistenceOf<Test>;
 }
 
 impl pallet_authorship::Config for Test {
diff --git a/substrate/frame/beefy/src/mock.rs b/substrate/frame/beefy/src/mock.rs
index ee84d9e5bbe40..5df910541b301 100644
--- a/substrate/frame/beefy/src/mock.rs
+++ b/substrate/frame/beefy/src/mock.rs
@@ -191,8 +191,8 @@ impl pallet_session::Config for Test {
 }
 
 impl pallet_session::historical::Config for Test {
-	type FullIdentification = pallet_staking::Exposure<u64, u128>;
-	type FullIdentificationOf = pallet_staking::ExposureOf<Self>;
+	type FullIdentification = pallet_staking::Existence;
+	type FullIdentificationOf = pallet_staking::ExistenceOf<Test>;
 }
 
 impl pallet_authorship::Config for Test {
diff --git a/substrate/frame/election-provider-multi-phase/test-staking-e2e/src/mock.rs b/substrate/frame/election-provider-multi-phase/test-staking-e2e/src/mock.rs
index 8619325d56b35..4b02fd6ca0337 100644
--- a/substrate/frame/election-provider-multi-phase/test-staking-e2e/src/mock.rs
+++ b/substrate/frame/election-provider-multi-phase/test-staking-e2e/src/mock.rs
@@ -147,8 +147,8 @@ impl pallet_session::Config for Runtime {
 	type WeightInfo = ();
 }
 impl pallet_session::historical::Config for Runtime {
-	type FullIdentification = ();
-	type FullIdentificationOf = pallet_staking::NullIdentity;
+	type FullIdentification = pallet_staking::Existence;
+	type FullIdentificationOf = pallet_staking::ExistenceOf<Runtime>;
 }
 
 frame_election_provider_support::generate_solution_type!(
diff --git a/substrate/frame/grandpa/src/mock.rs b/substrate/frame/grandpa/src/mock.rs
index 5de6107440d97..6c3870a90079c 100644
--- a/substrate/frame/grandpa/src/mock.rs
+++ b/substrate/frame/grandpa/src/mock.rs
@@ -109,8 +109,8 @@ impl pallet_session::Config for Test {
 }
 
 impl pallet_session::historical::Config for Test {
-	type FullIdentification = ();
-	type FullIdentificationOf = pallet_staking::NullIdentity;
+	type FullIdentification = pallet_staking::Existence;
+	type FullIdentificationOf = pallet_staking::ExistenceOf<Test>;
 }
 
 impl pallet_authorship::Config for Test {
diff --git a/substrate/frame/offences/benchmarking/src/mock.rs b/substrate/frame/offences/benchmarking/src/mock.rs
index fe5ef8e172c81..daa0b6c85bba9 100644
--- a/substrate/frame/offences/benchmarking/src/mock.rs
+++ b/substrate/frame/offences/benchmarking/src/mock.rs
@@ -53,8 +53,8 @@ impl pallet_timestamp::Config for Test {
 	type WeightInfo = ();
 }
 impl pallet_session::historical::Config for Test {
-	type FullIdentification = ();
-	type FullIdentificationOf = pallet_staking::NullIdentity;
+	type FullIdentification = pallet_staking::Existence;
+	type FullIdentificationOf = pallet_staking::ExistenceOf<Test>;
 }
 
 sp_runtime::impl_opaque_keys! {
diff --git a/substrate/frame/root-offences/src/lib.rs b/substrate/frame/root-offences/src/lib.rs
index 8e91c4ecfd1cd..33a3371d2d263 100644
--- a/substrate/frame/root-offences/src/lib.rs
+++ b/substrate/frame/root-offences/src/lib.rs
@@ -49,8 +49,8 @@ pub mod pallet {
 		+ pallet_staking::Config
 		+ pallet_session::Config<ValidatorId = <Self as frame_system::Config>::AccountId>
 		+ pallet_session::historical::Config<
-			FullIdentification = (),
-			FullIdentificationOf = pallet_staking::NullIdentity,
+			FullIdentification = pallet_staking::Existence,
+			FullIdentificationOf = pallet_staking::ExistenceOf<Self>,
 		>
 	{
 		type RuntimeEvent: From<Event<Self>> + IsType<<Self as frame_system::Config>::RuntimeEvent>;
diff --git a/substrate/frame/root-offences/src/mock.rs b/substrate/frame/root-offences/src/mock.rs
index 19119c5541e57..cd409dfd4ec9b 100644
--- a/substrate/frame/root-offences/src/mock.rs
+++ b/substrate/frame/root-offences/src/mock.rs
@@ -144,8 +144,8 @@ impl pallet_staking::Config for Test {
 }
 
 impl pallet_session::historical::Config for Test {
-	type FullIdentification = ();
-	type FullIdentificationOf = pallet_staking::NullIdentity;
+	type FullIdentification = pallet_staking::Existence;
+	type FullIdentificationOf = pallet_staking::ExistenceOf<Test>;
 }
 
 sp_runtime::impl_opaque_keys! {
diff --git a/substrate/frame/session/benchmarking/src/mock.rs b/substrate/frame/session/benchmarking/src/mock.rs
index da39ed4e1ffd0..40e7215ccc307 100644
--- a/substrate/frame/session/benchmarking/src/mock.rs
+++ b/substrate/frame/session/benchmarking/src/mock.rs
@@ -67,8 +67,8 @@ impl pallet_timestamp::Config for Test {
 	type WeightInfo = ();
 }
 impl pallet_session::historical::Config for Test {
-	type FullIdentification = ();
-	type FullIdentificationOf = pallet_staking::NullIdentity;
+	type FullIdentification = pallet_staking::Existence;
+	type FullIdentificationOf = pallet_staking::ExistenceOf<Test>;
 }
 
 sp_runtime::impl_opaque_keys! {
diff --git a/substrate/frame/staking/src/lib.rs b/substrate/frame/staking/src/lib.rs
index 6d712f1329148..75d0a76b7db7f 100644
--- a/substrate/frame/staking/src/lib.rs
+++ b/substrate/frame/staking/src/lib.rs
@@ -308,7 +308,9 @@ mod pallet;
 extern crate alloc;
 
 use alloc::{collections::btree_map::BTreeMap, vec, vec::Vec};
-use codec::{Decode, DecodeWithMemTracking, Encode, HasCompact, MaxEncodedLen};
+use codec::{
+	Decode, DecodeWithMemTracking, Encode, EncodeLike, HasCompact, Input, MaxEncodedLen, Output,
+};
 use frame_support::{
 	defensive, defensive_assert,
 	traits::{
@@ -1066,8 +1068,10 @@ impl<T: Config> Convert<T::AccountId, Option<T::AccountId>> for StashOf<T> {
 ///
 /// Active exposure is the exposure of the validator set currently validating, i.e. in
 /// `active_era`. It can differ from the latest planned exposure in `current_era`.
+#[deprecated(note = "Use `ExistenceOf` or `ExistenceOrLegacyExposureOf` instead")]
 pub struct ExposureOf<T>(core::marker::PhantomData<T>);
 
+#[allow(deprecated)]
 impl<T: Config> Convert<T::AccountId, Option<Exposure<T::AccountId, BalanceOf<T>>>>
 	for ExposureOf<T>
 {
@@ -1077,10 +1081,69 @@ impl<T: Config> Convert<T::AccountId, Option<Exposure<T::AccountId, BalanceOf<T>
 	}
 }
 
-pub struct NullIdentity;
-impl<T> Convert<T, Option<()>> for NullIdentity {
-	fn convert(_: T) -> Option<()> {
-		Some(())
+/// A type representing the presence of a validator. Encodes as a unit type.
+pub type Existence = ();
+
+/// A converter type that returns `Some(())` if the validator exists in the current active era,
+/// otherwise `None`. This serves as a lightweight presence check for validators.
+pub struct ExistenceOf<T>(core::marker::PhantomData<T>);
+impl<T: Config> Convert<T::AccountId, Option<Existence>> for ExistenceOf<T> {
+	fn convert(validator: T::AccountId) -> Option<Existence> {
+		Validators::<T>::contains_key(&validator).then_some(())
+	}
+}
+
+/// A compatibility wrapper type used to represent the presence of a validator in the current era.
+/// Encodes as type [`Existence`] but can decode from legacy [`Exposure`] values for backward
+/// compatibility.
+#[derive(PartialEq, Eq, PartialOrd, Ord, Clone, RuntimeDebug, TypeInfo, DecodeWithMemTracking)]
+pub enum ExistenceOrLegacyExposure<A, B: HasCompact> {
+	/// Validator exists in the current era.
+	Exists,
+	/// Legacy `Exposure` data, retained for decoding compatibility.
+	Exposure(Exposure<A, B>),
+}
+
+/// Converts a validator account ID to a Some([`ExistenceOrLegacyExposure::Exists`]) if the
+/// validator exists in the current era, otherwise `None`.
+pub struct ExistenceOrLegacyExposureOf<T>(core::marker::PhantomData<T>);
+
+impl<T: Config> Convert<T::AccountId, Option<ExistenceOrLegacyExposure<T::AccountId, BalanceOf<T>>>>
+	for ExistenceOrLegacyExposureOf<T>
+{
+	fn convert(
+		validator: T::AccountId,
+	) -> Option<ExistenceOrLegacyExposure<T::AccountId, BalanceOf<T>>> {
+		ActiveEra::<T>::get()
+			.map(|active_era| ErasStakersOverview::<T>::contains_key(active_era.index, &validator))
+			.unwrap_or(false)
+			.then_some(ExistenceOrLegacyExposure::Exists)
+	}
+}
+
+impl<A, B: HasCompact> Encode for ExistenceOrLegacyExposure<A, B>
+where
+	Exposure<A, B>: Encode,
+{
+	fn encode_to<T: Output + ?Sized>(&self, dest: &mut T) {
+		match self {
+			ExistenceOrLegacyExposure::Exists => (),
+			ExistenceOrLegacyExposure::Exposure(exposure) => exposure.encode_to(dest),
+		}
+	}
+}
+
+impl<A, B: HasCompact> EncodeLike for ExistenceOrLegacyExposure<A, B> where Exposure<A, B>: Encode {}
+
+impl<A, B: HasCompact> Decode for ExistenceOrLegacyExposure<A, B>
+where
+	Exposure<A, B>: Decode,
+{
+	fn decode<I: Input>(input: &mut I) -> Result<Self, codec::Error> {
+		match input.remaining_len() {
+			Ok(Some(x)) if x > 0 => Ok(ExistenceOrLegacyExposure::Exposure(Decode::decode(input)?)),
+			_ => Ok(ExistenceOrLegacyExposure::Exists),
+		}
 	}
 }
 
@@ -1369,3 +1432,52 @@ impl BenchmarkingConfig for TestBenchmarkingConfig {
 	type MaxValidators = frame_support::traits::ConstU32<100>;
 	type MaxNominators = frame_support::traits::ConstU32<100>;
 }
+
+#[cfg(test)]
+mod test {
+	use crate::ExistenceOrLegacyExposure;
+	use codec::{Decode, Encode};
+	use sp_staking::{Exposure, IndividualExposure};
+
+	#[test]
+	fn existence_encodes_decodes_correctly() {
+		let encoded_existence = ExistenceOrLegacyExposure::<u32, u32>::Exists.encode();
+		assert!(encoded_existence.is_empty());
+
+		// try decoding the existence
+		let decoded_existence =
+			ExistenceOrLegacyExposure::<u32, u32>::decode(&mut encoded_existence.as_slice())
+				.unwrap();
+		assert!(matches!(decoded_existence, ExistenceOrLegacyExposure::Exists));
+
+		// check that round-trip encoding works
+		assert_eq!(encoded_existence, decoded_existence.encode());
+	}
+
+	#[test]
+	fn legacy_existence_encodes_decodes_correctly() {
+		let legacy_exposure = Exposure::<u32, u32> {
+			total: 1,
+			own: 2,
+			others: vec![IndividualExposure { who: 3, value: 4 }],
+		};
+
+		let encoded_legacy_exposure = legacy_exposure.encode();
+
+		// try decoding the legacy exposure
+		let decoded_legacy_exposure =
+			ExistenceOrLegacyExposure::<u32, u32>::decode(&mut encoded_legacy_exposure.as_slice())
+				.unwrap();
+		assert_eq!(
+			decoded_legacy_exposure,
+			ExistenceOrLegacyExposure::Exposure(Exposure {
+				total: 1,
+				own: 2,
+				others: vec![IndividualExposure { who: 3, value: 4 }]
+			})
+		);
+
+		// round trip encoding works
+		assert_eq!(encoded_legacy_exposure, decoded_legacy_exposure.encode());
+	}
+}
diff --git a/substrate/frame/staking/src/mock.rs b/substrate/frame/staking/src/mock.rs
index a759d4ab2c63f..49e8b9705f9f0 100644
--- a/substrate/frame/staking/src/mock.rs
+++ b/substrate/frame/staking/src/mock.rs
@@ -151,8 +151,8 @@ impl pallet_session::Config for Test {
 }
 
 impl pallet_session::historical::Config for Test {
-	type FullIdentification = ();
-	type FullIdentificationOf = NullIdentity;
+	type FullIdentification = Existence;
+	type FullIdentificationOf = ExistenceOf<Test>;
 }
 impl pallet_authorship::Config for Test {
 	type FindAuthor = Author11;
diff --git a/substrate/frame/staking/src/pallet/impls.rs b/substrate/frame/staking/src/pallet/impls.rs
index 12af97385486d..1dfd88316801b 100644
--- a/substrate/frame/staking/src/pallet/impls.rs
+++ b/substrate/frame/staking/src/pallet/impls.rs
@@ -50,9 +50,10 @@ use sp_staking::{
 
 use crate::{
 	asset, election_size_tracker::StaticTracker, log, slashing, weights::WeightInfo, ActiveEraInfo,
-	BalanceOf, EraInfo, EraPayout, Exposure, Forcing, IndividualExposure, LedgerIntegrityState,
-	MaxNominationsOf, MaxWinnersOf, Nominations, NominationsQuota, PositiveImbalanceOf,
-	RewardDestination, SessionInterface, StakingLedger, ValidatorPrefs, STAKING_ID,
+	BalanceOf, EraInfo, EraPayout, Existence, ExistenceOrLegacyExposure, Exposure, Forcing,
+	IndividualExposure, LedgerIntegrityState, MaxNominationsOf, MaxWinnersOf, Nominations,
+	NominationsQuota, PositiveImbalanceOf, RewardDestination, SessionInterface, StakingLedger,
+	ValidatorPrefs, STAKING_ID,
 };
 use alloc::{boxed::Box, vec, vec::Vec};
 
@@ -1428,7 +1429,7 @@ impl<T: Config> ElectionDataProvider for Pallet<T> {
 
 		// We can't handle this case yet -- return an error. WIP to improve handling this case in
 		// <https://github.com/paritytech/substrate/pull/13195>.
-		if bounds.exhausted(None, CountBound(T::TargetList::count() as u32).into()) {
+		if bounds.exhausted(None, CountBound(T::TargetList::count()).into()) {
 			return Err("Target snapshot too big")
 		}
 
@@ -1571,42 +1572,23 @@ impl<T: Config> pallet_session::SessionManager<T::AccountId> for Pallet<T> {
 	}
 }
 
-impl<T: Config> historical::SessionManager<T::AccountId, Exposure<T::AccountId, BalanceOf<T>>>
+impl<T: Config>
+	historical::SessionManager<T::AccountId, ExistenceOrLegacyExposure<T::AccountId, BalanceOf<T>>>
 	for Pallet<T>
 {
 	fn new_session(
 		new_index: SessionIndex,
-	) -> Option<Vec<(T::AccountId, Exposure<T::AccountId, BalanceOf<T>>)>> {
+	) -> Option<Vec<(T::AccountId, ExistenceOrLegacyExposure<T::AccountId, BalanceOf<T>>)>> {
 		<Self as pallet_session::SessionManager<_>>::new_session(new_index).map(|validators| {
-			let current_era = CurrentEra::<T>::get()
-				// Must be some as a new era has been created.
-				.unwrap_or(0);
-
-			validators
-				.into_iter()
-				.map(|v| {
-					let exposure = Self::eras_stakers(current_era, &v);
-					(v, exposure)
-				})
-				.collect()
+			validators.into_iter().map(|v| (v, ExistenceOrLegacyExposure::Exists)).collect()
 		})
 	}
 	fn new_session_genesis(
 		new_index: SessionIndex,
-	) -> Option<Vec<(T::AccountId, Exposure<T::AccountId, BalanceOf<T>>)>> {
+	) -> Option<Vec<(T::AccountId, ExistenceOrLegacyExposure<T::AccountId, BalanceOf<T>>)>> {
 		<Self as pallet_session::SessionManager<_>>::new_session_genesis(new_index).map(
 			|validators| {
-				let current_era = CurrentEra::<T>::get()
-					// Must be some as a new era has been created.
-					.unwrap_or(0);
-
-				validators
-					.into_iter()
-					.map(|v| {
-						let exposure = Self::eras_stakers(current_era, &v);
-						(v, exposure)
-					})
-					.collect()
+				validators.into_iter().map(|v| (v, ExistenceOrLegacyExposure::Exists)).collect()
 			},
 		)
 	}
@@ -1618,12 +1600,12 @@ impl<T: Config> historical::SessionManager<T::AccountId, Exposure<T::AccountId,
 	}
 }
 
-impl<T: Config> historical::SessionManager<T::AccountId, ()> for Pallet<T> {
-	fn new_session(new_index: SessionIndex) -> Option<Vec<(T::AccountId, ())>> {
+impl<T: Config> historical::SessionManager<T::AccountId, Existence> for Pallet<T> {
+	fn new_session(new_index: SessionIndex) -> Option<Vec<(T::AccountId, Existence)>> {
 		<Self as pallet_session::SessionManager<_>>::new_session(new_index)
 			.map(|validators| validators.into_iter().map(|v| (v, ())).collect())
 	}
-	fn new_session_genesis(new_index: SessionIndex) -> Option<Vec<(T::AccountId, ())>> {
+	fn new_session_genesis(new_index: SessionIndex) -> Option<Vec<(T::AccountId, Existence)>> {
 		<Self as pallet_session::SessionManager<_>>::new_session_genesis(new_index)
 			.map(|validators| validators.into_iter().map(|v| (v, ())).collect())
 	}
diff --git a/substrate/frame/staking/src/tests.rs b/substrate/frame/staking/src/tests.rs
index 1b3411b65360d..20b9b55c8f69d 100644
--- a/substrate/frame/staking/src/tests.rs
+++ b/substrate/frame/staking/src/tests.rs
@@ -4662,6 +4662,28 @@ fn restricted_accounts_can_only_withdraw() {
 	})
 }
 
+#[test]
+fn validator_existence_check() {
+	ExtBuilder::default().build_and_execute(|| {
+		mock::start_active_era(1);
+
+		// Given: 11 is an active validator for Era 1
+		assert!(ErasStakersOverview::<Test>::get(1, 11).is_some());
+
+		// And: 31 is not an active validator for Era 1
+		assert!(ErasStakersOverview::<Test>::get(1, 31).is_none());
+
+		// Then: 11 converts to Exists.
+		assert_eq!(
+			ExistenceOrLegacyExposureOf::<Test>::convert(11),
+			Some(ExistenceOrLegacyExposure::Exists)
+		);
+
+		// And: 31 converts to None (Not Exists).
+		assert_eq!(ExistenceOrLegacyExposureOf::<Test>::convert(31), None);
+	});
+}
+
 mod election_data_provider {
 	use super::*;
 	use frame_election_provider_support::ElectionDataProvider;