Introduce PSM pallet (part of the pUSD Project)

Cargo.toml

@@ -414,6 +414,7 @@ members = [
 	"substrate/frame/people",
 	"substrate/frame/preimage",
 	"substrate/frame/proxy",
+	"substrate/frame/psm",
 	"substrate/frame/ranked-collective",
 	"substrate/frame/recovery",
 	"substrate/frame/referenda",
@@ -1039,6 +1040,7 @@ pallet-parameters = { path = "substrate/frame/parameters", default-features = fa
 pallet-people = { path = "substrate/frame/people", default-features = false }
 pallet-preimage = { path = "substrate/frame/preimage", default-features = false }
 pallet-proxy = { path = "substrate/frame/proxy", default-features = false }
+pallet-psm = { path = "substrate/frame/psm", default-features = false }
 pallet-ranked-collective = { path = "substrate/frame/ranked-collective", default-features = false }
 pallet-recovery = { path = "substrate/frame/recovery", default-features = false }
 pallet-referenda = { path = "substrate/frame/referenda", default-features = false }

prdoc/pr_11068.prdoc

@@ -0,0 +1,26 @@
+title: 'FRAME: Add Peg Stability Module (PSM) pallet'
+doc:
+- audience: Runtime Dev
+  description: |-
+    Introduces `pallet-psm`, a Peg Stability Module that enables 1:1 swaps between a native
+    stablecoin (pUSD) and pre-approved external stablecoins (e.g. USDC, USDT). The PSM
+    strengthens the stablecoin peg by creating arbitrage opportunities bounded by configurable
+    minting and redemption fees.
+
+    Key features:
+    - Minting: deposit an external stablecoin to receive pUSD
+    - Redemption: burn pUSD to receive an external stablecoin
+    - Per-asset circuit breakers to disable minting or all swaps
+    - Configurable ceiling weights and maximum PSM debt ratio
+    - Inter-pallet traits (`VaultsInterface`, `PsmInterface`) for coordinating debt ceilings
+      with a companion Vaults pallet
+
+crates:
+- name: pallet-psm
+  bump: major
+- name: kitchensink-runtime
+  bump: major
+- name: frame-support
+  bump: minor
+- name: polkadot-sdk
+  bump: minor

substrate/bin/node/runtime/src/lib.rs

@@ -2881,6 +2881,9 @@ mod runtime {
 	#[runtime::pallet_index(85)]
 	pub type Oracle = pallet_oracle::Pallet<Runtime>;
 
+	#[runtime::pallet_index(86)]
+	pub type Psm = pallet_psm::Pallet<Runtime>;
+
 	#[runtime::pallet_index(89)]
 	pub type MetaTx = pallet_meta_tx::Pallet<Runtime>;
 
@@ -3062,6 +3065,65 @@ impl pallet_oracle::Config for Runtime {
 	type BenchmarkHelper = OracleBenchmarkingHelper;
 }
 
+parameter_types! {
+	/// The pUSD stablecoin asset ID.
+	pub const PsmStablecoinAssetId: u32 = 4242;
+	/// Minimum swap amount for PSM operations (100 pUSD = 100 * 10^6).
+	pub const PsmMinSwapAmount: Balance = 100_000_000;
+	/// PalletId for deriving the PSM system account.
+	pub const PsmPalletId: PalletId = PalletId(*b"py/pegsm");
+	/// Insurance fund account that receives PSM fee revenue.
+	pub PsmInsuranceFundAccount: AccountId =
+		sp_runtime::traits::AccountIdConversion::<AccountId>::into_account_truncating(
+			&PalletId(*b"py/insur"),
+		);
+}
+
+type PsmStableAsset = ItemOf<Assets, PsmStablecoinAssetId, AccountId>;
+
+/// Stub VaultsInterface that imposes no debt ceiling.
+pub struct NoVaultsCeiling;
+impl frame_support::traits::VaultsInterface for NoVaultsCeiling {
+	type Balance = Balance;
+	fn get_maximum_issuance() -> Balance {
+		Balance::MAX
+	}
+}
+
+/// EnsureOrigin implementation for PSM management that supports privilege levels.
+pub struct EnsurePsmManager;
+impl frame_support::traits::EnsureOrigin<RuntimeOrigin> for EnsurePsmManager {
+	type Success = pallet_psm::PsmManagerLevel;
+
+	fn try_origin(o: RuntimeOrigin) -> Result<Self::Success, RuntimeOrigin> {
+		use frame_system::RawOrigin;
+
+		match o.clone().into() {
+			Ok(RawOrigin::Root) => Ok(pallet_psm::PsmManagerLevel::Full),
+			_ => Err(o),
+		}
+	}
+
+	#[cfg(feature = "runtime-benchmarks")]
+	fn try_successful_origin() -> Result<RuntimeOrigin, ()> {
+		Ok(RuntimeOrigin::root())
+	}
+}
+
+/// Configure the PSM (Peg Stability Module) pallet.
+impl pallet_psm::Config for Runtime {
+	type Fungibles = Assets;
+	type AssetId = u32;
+	type VaultsInterface = NoVaultsCeiling;
+	type ManagerOrigin = EnsurePsmManager;
+	type WeightInfo = pallet_psm::weights::SubstrateWeight<Runtime>;
+	type StableAsset = PsmStableAsset;
+	type FeeHandler = ResolveTo<PsmInsuranceFundAccount, PsmStableAsset>;
+	type PalletId = PsmPalletId;
+	type MinSwapAmount = PsmMinSwapAmount;
+	type MaxExternalAssets = ConstU32<10>;
+}
+
 /// MMR helper types.
 mod mmr {
 	use super::*;
@@ -3207,6 +3269,7 @@ mod benches {
 		[pallet_asset_conversion_ops, AssetConversionMigration]
 		[pallet_verify_signature, VerifySignature]
 		[pallet_meta_tx, MetaTx]
+		[pallet_psm, Psm]
 	);
 }
 

substrate/frame/psm/Cargo.toml

@@ -0,0 +1,58 @@
+[package]
+name = "pallet-psm"
+version = "0.1.0"
+authors.workspace = true
+edition.workspace = true
+license = "Apache-2.0"
+homepage.workspace = true
+repository.workspace = true
+description = "FRAME pallet for the Peg Stability Module."
+readme = "README.md"
+include = ["README.md", "src/**/*"]
+
+[lints]
+workspace = true
+
+[package.metadata.docs.rs]
+targets = ["x86_64-unknown-linux-gnu"]
+
+[dependencies]
+codec = { features = ["derive"], workspace = true }
+frame-benchmarking = { workspace = true, optional = true }
+frame-support = { workspace = true }
+frame-system = { workspace = true }
+log = { workspace = true }
+scale-info = { features = ["derive"], workspace = true }
+sp-runtime = { workspace = true }
+
+[dev-dependencies]
+pallet-assets = { workspace = true, default-features = true }
+pallet-balances = { workspace = true, default-features = true }
+sp-io = { workspace = true, default-features = true }
+
+[features]
+default = ["std"]
+std = [
+	"codec/std",
+	"frame-benchmarking?/std",
+	"frame-support/std",
+	"frame-system/std",
+	"log/std",
+	"scale-info/std",
+	"sp-runtime/std",
+]
+runtime-benchmarks = [
+	"frame-benchmarking/runtime-benchmarks",
+	"frame-support/runtime-benchmarks",
+	"frame-system/runtime-benchmarks",
+	"pallet-assets/runtime-benchmarks",
+	"pallet-balances/runtime-benchmarks",
+	"sp-runtime/runtime-benchmarks",
+]
+try-runtime = [
+	"frame-support/try-runtime",
+	"frame-system/try-runtime",
+	"pallet-assets/try-runtime",
+	"pallet-balances/try-runtime",
+	"sp-runtime/try-runtime",
+]