Fix AH Inflation back to what RC was (#998)

While copying configs from RC to AH, the fixed total issuance noted in
[Referendum 1139](https://polkadot.subsquare.io/referenda/1139) was
misplaced with sth else. This PR fixes this.

**Note to all validators and stakers: Until this fix is deployed, the
staking rewards are expected to be about 60% less than before.**

- [x] move `experimental_inflation_prediction_info` to AH.
- [x] use `async_backing::MINUTES`!

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: Bastian Köcher <git@kchr.de>

Author: 3 people

.github/workflows/check-migrations.yml

@@ -77,7 +77,7 @@ jobs:
             CHECKS="pre-and-post"
           else
             echo "Enabling weight checks since we are not on a relay"
-            
+
             echo "Enabling try-state checks on the non-relay"
             CHECKS="all"
           fi

CHANGELOG.md

@@ -6,8 +6,9 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## [Unreleased]
 
-### Fixed 
+### Fixed
 
+- Fix AH staking inflation calculation to use correct total issuance (https://github.com/polkadot-fellows/runtimes/pull/998).
 - Set invulnerable deposit for Polkadot AssetHub staking election ([#993](https://github.com/polkadot-fellows/runtimes/pull/993))
 
 ## [2.0.1] 04.11.2025

Cargo.lock

@@ -8,23 +8,15 @@ repository.workspace = true
 version.workspace = true
 
 [dependencies]
-codec = { features = ["derive", "max-encoded-len"], workspace = true }
-scale-info = { features = ["derive"], workspace = true }
-
-sp-api = { workspace = true }
 sp-runtime = { workspace = true }
-polkadot-primitives = { workspace = true }
 pallet-staking-reward-fn = { workspace = true }
+polkadot-primitives = { workspace = true }
 
 [features]
 default = ["std"]
 std = [
-	"codec/std",
-	"scale-info/std",
-
 	"pallet-staking-reward-fn/std",
 	"polkadot-primitives/std",
-	"sp-api/std",
 	"sp-runtime/std",
 ]
 runtime-benchmarks = [

relay/common/Cargo.toml

@@ -20,35 +20,6 @@
 use polkadot_primitives::Balance;
 use sp_runtime::{Perquintill, Saturating};
 
-/// Extra runtime APIs for kusama runtime.
-pub mod apis {
-	/// Information about the current inflation rate of the system.
-	///
-	/// Both fields should be treated as best-effort, given that the inflation rate might not be
-	/// fully predict-able.
-	#[derive(scale_info::TypeInfo, codec::Encode, codec::Decode)]
-	#[cfg_attr(feature = "std", derive(Debug))]
-	pub struct InflationInfo {
-		/// The rate of inflation estimated per annum.
-		pub inflation: sp_runtime::Perquintill,
-		/// Next amount that we anticipate to mint.
-		///
-		/// First item is the amount that goes to stakers, second is the leftover that is usually
-		/// forwarded to the treasury.
-		pub next_mint: (polkadot_primitives::Balance, polkadot_primitives::Balance),
-	}
-
-	sp_api::decl_runtime_apis! {
-		pub trait Inflation {
-			/// Return the current estimates of the inflation amount.
-			///
-			/// This is marked as experimental in light of RFC#89. Nonetheless, its usage is highly
-			/// recommended over trying to read-storage, or re-create the onchain logic.
-			fn experimental_inflation_prediction_info() -> InflationInfo;
-		}
-	}
-}
-
 // ---- TODO: Below is copy pasted from sdk, remove once we pull the version containing
 // https://github.com/paritytech/polkadot-sdk/pull/4938
 

relay/common/src/lib.rs

@@ -97,7 +97,6 @@ use polkadot_runtime_common::{
 	paras_registrar, prod_or_fast, slots, BalanceToU256, BlockHashCount, BlockLength,
 	CurrencyToVote, SlowAdjustingFeeUpdate, U256ToBalance,
 };
-use relay_common::apis::*;
 use runtime_parachains::{
 	assigner_coretime as parachains_assigner_coretime,
 	configuration::{
@@ -124,7 +123,7 @@ use sp_runtime::{
 	generic, impl_opaque_keys,
 	traits::{
 		AccountIdConversion, AccountIdLookup, BlakeTwo256, Block as BlockT, Convert, ConvertInto,
-		Get, IdentityLookup, Keccak256, OpaqueKeys, SaturatedConversion, Saturating, Verify,
+		Get, IdentityLookup, Keccak256, OpaqueKeys, SaturatedConversion, Verify,
 	},
 	transaction_validity::{TransactionPriority, TransactionSource, TransactionValidity},
 	ApplyExtrinsicResult, FixedU128, KeyTypeId, OpaqueValue, Perbill, Percent, Permill,
@@ -2437,43 +2436,7 @@ mod benches {
 #[cfg(feature = "runtime-benchmarks")]
 use benches::*;
 
-impl Runtime {
-	fn impl_experimental_inflation_info() -> InflationInfo {
-		use pallet_staking::{ActiveEra, EraPayout, ErasTotalStake};
-		let (staked, _start) = ActiveEra::<Runtime>::get()
-			.map(|ae| (ErasTotalStake::<Runtime>::get(ae.index), ae.start.unwrap_or(0)))
-			.unwrap_or((0, 0));
-
-		let ideal_staking_rate = dynamic_params::inflation::IdealStake::get();
-		let inflation = if dynamic_params::inflation::UseAuctionSlots::get() {
-			let auctioned_slots = parachains_paras::Parachains::<Runtime>::get()
-				.into_iter()
-				// All active para-ids that do not belong to a system chain is the number of
-				// parachains that we should take into account for inflation.
-				.filter(|i| *i >= LOWEST_PUBLIC_ID)
-				.count() as u64;
-			ideal_staking_rate
-				.saturating_sub(Perquintill::from_rational(auctioned_slots.min(60), 200u64))
-		} else {
-			ideal_staking_rate
-		};
-
-		// We assume un-delayed 6h eras.
-		let era_duration = 6 * (HOURS as Moment) * MILLISECS_PER_BLOCK;
-		let next_mint =
-			<Self as pallet_staking::Config>::EraPayout::era_payout(staked, 0, era_duration);
-
-		InflationInfo { inflation, next_mint }
-	}
-}
-
 sp_api::impl_runtime_apis! {
-	impl relay_common::apis::Inflation<Block> for Runtime {
-		fn experimental_inflation_prediction_info() -> InflationInfo {
-			Runtime::impl_experimental_inflation_info()
-		}
-	}
-
 	impl sp_api::Core<Block> for Runtime {
 		fn version() -> RuntimeVersion {
 			VERSION

relay/kusama/src/lib.rs

@@ -94,7 +94,6 @@ use sp_runtime::traits::Convert;
 
 use pallet_staking_async_ah_client as ah_client;
 use pallet_staking_async_rc_client as rc_client;
-use relay_common::apis::InflationInfo;
 use runtime_parachains::{
 	assigner_coretime as parachains_assigner_coretime, configuration as parachains_configuration,
 	configuration::ActiveConfigHrmpChannelSizeAndCapacityRatio,
@@ -2261,39 +2260,7 @@ mod benches {
 #[cfg(feature = "runtime-benchmarks")]
 use benches::*;
 
-impl Runtime {
-	fn impl_experimental_inflation_info() -> InflationInfo {
-		use pallet_staking::{ActiveEra, EraPayout, ErasTotalStake};
-		let (staked, _start) = ActiveEra::<Runtime>::get()
-			.map(|ae| (ErasTotalStake::<Runtime>::get(ae.index), ae.start.unwrap_or(0)))
-			.unwrap_or((0, 0));
-		let stake_able_issuance = Balances::total_issuance();
-
-		// We assume un-delayed 24h eras.
-		let era_duration = 24 * (HOURS as Moment) * MILLISECS_PER_BLOCK;
-		let next_mint = <Self as pallet_staking::Config>::EraPayout::era_payout(
-			staked,
-			stake_able_issuance,
-			era_duration,
-		);
-		// reverse-engineer the current inflation by looking at the total minted against the total
-		// issuance.
-		let inflation = Perquintill::from_rational(
-			(next_mint.0 + next_mint.1) * 36525 / 100,
-			stake_able_issuance,
-		);
-
-		InflationInfo { inflation, next_mint }
-	}
-}
-
 sp_api::impl_runtime_apis! {
-	impl relay_common::apis::Inflation<Block> for Runtime {
-		fn experimental_inflation_prediction_info() -> InflationInfo {
-			Runtime::impl_experimental_inflation_info()
-		}
-	}
-
 	impl sp_api::Core<Block> for Runtime {
 		fn version() -> RuntimeVersion {
 			VERSION
@@ -3618,7 +3585,6 @@ mod remote_tests {
 			log::info!(target: LOG_TARGET, "era-duration = {average_era_duration_millis:?}");
 			log::info!(target: LOG_TARGET, "maxStakingRewards = {:?}", pallet_staking::MaxStakedRewards::<Runtime>::get());
 			log::info!(target: LOG_TARGET, "💰 Inflation ==> staking = {:?} / leftover = {:?}", token.amount(staking), token.amount(leftover));
-			log::info!(target: LOG_TARGET, "inflation_rate runtime API: {:?}", Runtime::impl_experimental_inflation_info());
 		});
 	}
 }

relay/polkadot/src/lib.rs

@@ -1440,15 +1440,17 @@ pub mod dynamic_params {
 	pub mod staking_election {
 		/// 10m worth of local 6s blocks for signed phase.
 		#[codec(index = 0)]
-		pub static SignedPhase: BlockNumber = 10 * system_parachains_constants::MINUTES;
+		pub static SignedPhase: BlockNumber =
+			10 * system_parachains_constants::async_backing::MINUTES;
 
 		/// Allow up to 16 signed solutions to be submitted.
 		#[codec(index = 1)]
 		pub static MaxSignedSubmissions: u32 = 16;
 
-		/// 10m for unsigned phase...
+		/// 5m for unsigned phase...
 		#[codec(index = 2)]
-		pub static UnsignedPhase: BlockNumber = 10 * system_parachains_constants::MINUTES;
+		pub static UnsignedPhase: BlockNumber =
+			5 * system_parachains_constants::async_backing::MINUTES;
 
 		/// .. in which we try and mine a 4-page solution.
 		#[codec(index = 3)]
@@ -2650,6 +2652,12 @@ pallet_revive::impl_runtime_apis_plus_revive!(
 		}
 	}
 
+	impl system_parachains_common::apis::Inflation<Block> for Runtime {
+		fn experimental_issuance_prediction_info() -> system_parachains_common::apis::InflationInfo {
+			crate::staking::EraPayout::impl_experimental_inflation_info()
+		}
+	}
+
 	#[cfg(feature = "try-runtime")]
 	impl frame_try_runtime::TryRuntime<Block> for Runtime {
 		fn on_runtime_upgrade(checks: frame_try_runtime::UpgradeCheckSelect) -> (Weight, Weight) {

system-parachains/asset-hubs/asset-hub-kusama/src/lib.rs

@@ -30,6 +30,7 @@ use pallet_staking_async_rc_client as rc_client;
 use scale_info::TypeInfo;
 use sp_runtime::{transaction_validity::TransactionPriority, Perquintill};
 use sp_staking::SessionIndex;
+use system_parachains_common::apis::InflationInfo;
 use xcm::v5::prelude::*;
 
 // alias for the ones backed by parameters-pallet.
@@ -332,6 +333,30 @@ impl pallet_staking_async::EraPayout<Balance> for EraPayout {
 	}
 }
 
+impl EraPayout {
+	pub(crate) fn impl_experimental_inflation_info() -> InflationInfo {
+		use pallet_staking_async::{ActiveEra, ActiveEraInfo, ErasTotalStake};
+		let staked = ActiveEra::<Runtime>::get()
+			.map(|ActiveEraInfo { index, .. }| ErasTotalStake::<Runtime>::get(index))
+			.unwrap_or(0);
+		let ti = pallet_balances::Pallet::<Runtime>::total_issuance();
+
+		// We assume un-delayed 6h eras.
+		let era_duration = 6 * 60 * 60 * 1000;
+		let next_mint = <Self as pallet_staking_async::EraPayout<Balance>>::era_payout(
+			staked,
+			ti,
+			era_duration,
+		);
+		let total = next_mint.0 + next_mint.1;
+		const NUM_ERAS_PER_DAY: u128 = 4;
+		let annual_issuance = total * 36525 * NUM_ERAS_PER_DAY / 100;
+		let issuance = Perquintill::from_rational(annual_issuance, ti);
+
+		InflationInfo { issuance, next_mint }
+	}
+}
+
 parameter_types! {
 	pub const SessionsPerEra: SessionIndex = 6;
 	/// Note: This is measured in RC block time. Our calculation of when to plan a new era might get
@@ -557,6 +582,23 @@ mod tests {
 			);
 			assert_eq!(staking, 844_606070970705);
 			assert_eq!(treasury, 320_110565207524);
+
+			pallet_balances::TotalIssuance::<Runtime>::put(17016510054564053390u128);
+			pallet_staking_async::ActiveEra::<Runtime>::put(pallet_staking_async::ActiveEraInfo {
+				index: 777,
+				start: None,
+			});
+			pallet_staking_async::ErasTotalStake::<Runtime>::insert(777, 8085567183241128549u128);
+			let expected_issuance_parts = 99999999999999249;
+			assert_eq!(
+				super::EraPayout::impl_experimental_inflation_info(),
+				InflationInfo {
+					issuance: Perquintill::from_parts(99999999999999249),
+					next_mint: (staking, treasury),
+				}
+			);
+			// around 9% now
+			assert_eq!(expected_issuance_parts * 100 / 10u64.pow(18), 9)
 		});
 	}
 
@@ -566,6 +608,7 @@ mod tests {
 		// session `n` and the results to be ready before the end of that session. Atm RC and KAH
 		// have the same block time, 6s.
 		sp_io::TestExternalities::new_empty().execute_with(|| {
+			sp_tracing::try_init_simple();
 			let duration = <<Runtime as pallet_staking_async::Config>::ElectionProvider as ElectionProvider>::duration();
 			let session = RelaySessionDuration::get();
 			log::info!(target: "runtime::asset-hub-kusama", "election duration is {duration:?}, relay session {session:?}",);

system-parachains/asset-hubs/asset-hub-kusama/src/staking/mod.rs

@@ -27,6 +27,7 @@ collectives-polkadot-runtime-constants = { workspace = true }
 kusama-runtime-constants = { workspace = true }
 polkadot-runtime-constants = { workspace = true }
 system-parachains-constants = { workspace = true }
+system-parachains-common = { workspace = true }
 
 # Substrate
 frame-benchmarking = { optional = true, workspace = true }
@@ -217,6 +218,7 @@ runtime-benchmarks = [
 	"snowbridge-runtime-common/runtime-benchmarks",
 	"sp-runtime/runtime-benchmarks",
 	"sp-staking/runtime-benchmarks",
+	"system-parachains-common/runtime-benchmarks",
 	"system-parachains-constants/runtime-benchmarks",
 	"xcm-builder/runtime-benchmarks",
 	"xcm-executor/runtime-benchmarks",
@@ -281,6 +283,7 @@ try-runtime = [
 	"snowbridge-pallet-system-frontend/try-runtime",
 	"snowbridge-runtime-common/try-runtime",
 	"sp-runtime/try-runtime",
+	"system-parachains-common/try-runtime",
 ]
 std = [
 	"pallet-ah-migrator/std",
@@ -388,6 +391,7 @@ std = [
 	"sp-version/std",
 	"sp-weights/std",
 	"substrate-wasm-builder",
+	"system-parachains-common/std",
 	"system-parachains-constants/std",
 	"xcm-builder/std",
 	"xcm-executor/std",