Introduce gas floor

node/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Enforce `min_tx_gas` in mempool preverify, reject TXs where `gas_limit < max(min_gas_limit, min_tx_gas)` [#3940]
+
 ## [1.4.1] - 2025-12-04
 
 ### Added
@@ -76,6 +80,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - First `dusk-node` release
 
 <!-- Issues -->
+[#3940]: https://github.com/dusk-network/rusk/issues/3940
 [#3917]: https://github.com/dusk-network/rusk/issues/3917
 [#3874]: https://github.com/dusk-network/rusk/issues/3874
 [#3871]: https://github.com/dusk-network/rusk/issues/3871

node/src/mempool.rs

@@ -61,7 +61,7 @@ pub enum TxAcceptanceError {
     VerificationFailed(String),
     #[error("gas price lower than minimum {0}")]
     GasPriceTooLow(u64),
-    #[error("gas limit lower than minimum {0}")]
+    #[error("gas limit lower than minimum {0} LUX")]
     GasLimitTooLow(u64),
     #[error("Maximum count of transactions exceeded {0}")]
     MaxTxnCountExceeded(usize),
@@ -349,10 +349,16 @@ impl MempoolSrv {
                 dusk_consensus::validate_blob_sidecars(tx)?;
             }
 
-            // Check global minimum gas limit
-            let min_gas_limit = vm.min_gas_limit();
-            if tx.inner.gas_limit() < min_gas_limit {
-                return Err(TxAcceptanceError::GasLimitTooLow(min_gas_limit));
+            // Check global minimum gas limit and per-tx fee floor
+            let chain_min_gas_limit = vm.min_gas_limit();
+            let min_tx_gas = vm.min_tx_gas(tip_height);
+            let required_gas_limit =
+                core::cmp::max(chain_min_gas_limit, min_tx_gas);
+
+            if tx.inner.gas_limit() < required_gas_limit {
+                return Err(TxAcceptanceError::GasLimitTooLow(
+                    required_gas_limit,
+                ));
             }
         }
 

node/src/vm.rs

@@ -98,6 +98,7 @@ pub trait VMExecution: Send + Sync + 'static {
     fn wasm64_disabled(&self, block_height: u64) -> bool;
     fn wasm32_disabled(&self, block_height: u64) -> bool;
     fn third_party_disabled(&self, block_height: u64) -> bool;
+    fn min_tx_gas(&self, height: u64) -> u64;
 }
 
 #[allow(clippy::large_enum_variant)]

rusk/CHANGELOG.md

@@ -7,6 +7,10 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 ## [Unreleased]
 
+### Added
+
+- Add TX floor price feature, including for well-known chain ids [#3940]
+
 ## [1.4.1] - 2025-12-04
 
 ### Added
@@ -406,6 +410,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 - Add build system that generates keys for circuits and caches them.
 
 <!-- Issues -->
+[#3940]: https://github.com/dusk-network/rusk/issues/3940
 [#3917]: https://github.com/dusk-network/rusk/issues/3917
 [#3897]: https://github.com/dusk-network/rusk/issues/3897
 [#3894]: https://github.com/dusk-network/rusk/issues/3894

rusk/src/lib/node/vm.rs

@@ -321,6 +321,19 @@ impl VMExecution for Rusk {
             .map(|activation| activation.is_active_at(block_height))
             .unwrap_or(false)
     }
+
+    fn min_tx_gas(&self, height: u64) -> u64 {
+        self.vm_config
+            .feature(FEATURE_MIN_TX_GAS)
+            .map(|activation| {
+                if activation.is_active_at(height) {
+                    self.vm_config.min_tx_gas
+                } else {
+                    0
+                }
+            })
+            .unwrap_or(0)
+    }
 }
 
 fn has_unique_elements<T>(iter: T) -> bool

rusk/src/lib/node/vm/config.rs

@@ -21,6 +21,8 @@ const DEFAULT_GAS_PER_BLOB: u64 = 1_000_000;
 const DEFAULT_MIN_DEPLOY_POINTS: u64 = 5_000_000;
 const DEFAULT_MIN_DEPLOYMENT_GAS_PRICE: u64 = 2_000;
 const DEFAULT_BLOCK_GAS_LIMIT: u64 = 3 * 1_000_000_000;
+/// Default per‑tx minimum gas floor. 0 disables it.
+const DEFAULT_MIN_TX_GAS: u64 = 5_000_000;
 
 /// Configuration for the execution of a transaction.
 #[derive(Debug, Clone, serde::Serialize)]
@@ -45,6 +47,9 @@ pub struct Config {
     #[serde(with = "humantime_serde")]
     pub generation_timeout: Option<Duration>,
 
+    /// Minimum gas charged for any transaction.
+    pub min_tx_gas: u64,
+
     /// Set of features to activate
     features: HashMap<String, FeatureActivation>,
 }
@@ -61,6 +66,7 @@ pub(crate) mod feature {
     pub const FEATURE_DISABLE_WASM64: &str = "DISABLE_WASM64";
     pub const FEATURE_DISABLE_WASM32: &str = "DISABLE_WASM32";
     pub const FEATURE_DISABLE_3RD_PARTY: &str = "DISABLE_3RD_PARTY";
+    pub const FEATURE_MIN_TX_GAS: &str = "MIN_TX_GAS";
 
     pub const HQ_KECCAK256: &str = "HQ_KECCAK256";
 }
@@ -73,6 +79,7 @@ impl Config {
             min_deployment_gas_price: DEFAULT_MIN_DEPLOYMENT_GAS_PRICE,
             min_deploy_points: DEFAULT_MIN_DEPLOY_POINTS,
             block_gas_limit: DEFAULT_BLOCK_GAS_LIMIT,
+            min_tx_gas: DEFAULT_MIN_TX_GAS,
             generation_timeout: None,
             features: HashMap::new(),
         }
@@ -121,6 +128,12 @@ impl Config {
         self
     }
 
+    /// Set the minimum gas charged for any transaction.
+    pub const fn with_min_tx_gas(mut self, min_tx_gas: u64) -> Self {
+        self.min_tx_gas = min_tx_gas;
+        self
+    }
+
     /// Create a new `Config` with the given parameters.
     pub fn to_execution_config(&self, block_height: u64) -> ExecutionConfig {
         let with_public_sender: bool = self
@@ -143,11 +156,23 @@ impl Config {
             .feature(feature::FEATURE_DISABLE_3RD_PARTY)
             .map(|activation| activation.is_active_at(block_height))
             .unwrap_or_default();
+        let min_tx_gas = self
+            .feature(feature::FEATURE_MIN_TX_GAS)
+            .map(|activation| {
+                if activation.is_active_at(block_height) {
+                    self.min_tx_gas
+                } else {
+                    0
+                }
+            })
+            .unwrap_or(0);
+
         ExecutionConfig {
             gas_per_blob: self.gas_per_blob,
             gas_per_deploy_byte: self.gas_per_deploy_byte,
             min_deploy_points: self.min_deploy_points,
             min_deploy_gas_price: self.min_deployment_gas_price,
+            min_tx_gas,
             with_public_sender,
             with_blob,
             disable_wasm64,

rusk/src/lib/node/vm/config/known.rs

@@ -10,7 +10,9 @@ use std::sync::LazyLock;
 
 use dusk_vm::FeatureActivation;
 
-use crate::node::{FEATURE_DISABLE_3RD_PARTY, FEATURE_DISABLE_WASM32};
+use crate::node::{
+    FEATURE_DISABLE_3RD_PARTY, FEATURE_DISABLE_WASM32, FEATURE_MIN_TX_GAS,
+};
 
 use super::feature::{
     FEATURE_ABI_PUBLIC_SENDER, FEATURE_BLOB, FEATURE_DISABLE_WASM64,
@@ -19,6 +21,7 @@ use super::feature::{
 use super::{
     DEFAULT_BLOCK_GAS_LIMIT, DEFAULT_GAS_PER_BLOB, DEFAULT_GAS_PER_DEPLOY_BYTE,
     DEFAULT_MIN_DEPLOYMENT_GAS_PRICE, DEFAULT_MIN_DEPLOY_POINTS,
+    DEFAULT_MIN_TX_GAS,
 };
 
 pub const MAINNET_ID: u8 = 1;
@@ -36,7 +39,8 @@ pub struct WellKnownConfig {
     pub min_deploy_points: u64,
     pub min_deployment_gas_price: u64,
     pub block_gas_limit: u64,
-    pub features: [(&'static str, FeatureActivation); 6],
+    pub min_tx_gas: u64,
+    pub features: [(&'static str, FeatureActivation); 7],
 }
 
 impl WellKnownConfig {
@@ -79,6 +83,9 @@ static MAINNET_DISABLE_WASM_64: LazyLock<FeatureActivation> =
 const MAINNET_BLOB_ACTIVATION: FeatureActivation =
     FeatureActivation::Height(MAINNET_AT_10_12_2025_AT_09_00_UTC);
 
+const MAINNET_MIN_TX_GAS_ACTIVATION: FeatureActivation =
+    FeatureActivation::Height(3_060_210);
+
 /// Mainnet VM configuration.
 static MAINNET_CONFIG: LazyLock<WellKnownConfig> =
     LazyLock::new(|| WellKnownConfig {
@@ -87,34 +94,41 @@ static MAINNET_CONFIG: LazyLock<WellKnownConfig> =
         min_deploy_points: DEFAULT_MIN_DEPLOY_POINTS,
         min_deployment_gas_price: DEFAULT_MIN_DEPLOYMENT_GAS_PRICE,
         block_gas_limit: DEFAULT_BLOCK_GAS_LIMIT,
+        min_tx_gas: DEFAULT_MIN_TX_GAS,
         features: [
             (FEATURE_ABI_PUBLIC_SENDER, MAINNET_SENDER_ACTIVATION_HEIGHT),
             (HQ_KECCAK256, NEVER),
             (FEATURE_BLOB, MAINNET_BLOB_ACTIVATION),
             (FEATURE_DISABLE_WASM64, MAINNET_DISABLE_WASM_64.clone()),
             (FEATURE_DISABLE_WASM32, MAINNET_3RD_PARTY_OFF.clone()),
             (FEATURE_DISABLE_3RD_PARTY, MAINNET_3RD_PARTY_OFF.clone()),
+            (FEATURE_MIN_TX_GAS, MAINNET_MIN_TX_GAS_ACTIVATION),
         ],
     });
 
 /// Estimated testnet block height for 12th November 2025, 09:00 UTC.
 const TESTNET_AT_12_11_2025_AT_09_00_UTC: FeatureActivation =
     FeatureActivation::Height(1_814_090);
 
+const TESTNET_MIN_TX_GAS_ACTIVATION: FeatureActivation =
+    FeatureActivation::Height(2_242_800);
+
 /// Testnet VM configuration.
 const TESTNET_CONFIG: WellKnownConfig = WellKnownConfig {
     gas_per_blob: DEFAULT_GAS_PER_BLOB,
     gas_per_deploy_byte: DEFAULT_GAS_PER_DEPLOY_BYTE,
     min_deploy_points: DEFAULT_MIN_DEPLOY_POINTS,
     min_deployment_gas_price: DEFAULT_MIN_DEPLOYMENT_GAS_PRICE,
     block_gas_limit: DEFAULT_BLOCK_GAS_LIMIT,
+    min_tx_gas: DEFAULT_MIN_TX_GAS,
     features: [
         (FEATURE_ABI_PUBLIC_SENDER, GENESIS),
         (HQ_KECCAK256, NEVER),
         (FEATURE_BLOB, TESTNET_AT_12_11_2025_AT_09_00_UTC),
         (FEATURE_DISABLE_WASM64, TESTNET_AT_12_11_2025_AT_09_00_UTC),
         (FEATURE_DISABLE_WASM32, NEVER),
         (FEATURE_DISABLE_3RD_PARTY, NEVER),
+        (FEATURE_MIN_TX_GAS, TESTNET_MIN_TX_GAS_ACTIVATION),
     ],
 };
 
@@ -125,13 +139,15 @@ const DEVNET_CONFIG: WellKnownConfig = WellKnownConfig {
     min_deploy_points: DEFAULT_MIN_DEPLOY_POINTS,
     min_deployment_gas_price: DEFAULT_MIN_DEPLOYMENT_GAS_PRICE,
     block_gas_limit: DEFAULT_BLOCK_GAS_LIMIT,
+    min_tx_gas: DEFAULT_MIN_TX_GAS,
     features: [
         (FEATURE_ABI_PUBLIC_SENDER, GENESIS),
         (HQ_KECCAK256, GENESIS),
         (FEATURE_BLOB, GENESIS),
         (FEATURE_DISABLE_WASM64, GENESIS),
         (FEATURE_DISABLE_WASM32, NEVER),
         (FEATURE_DISABLE_3RD_PARTY, NEVER),
+        (FEATURE_MIN_TX_GAS, GENESIS),
     ],
 };
 
@@ -142,12 +158,14 @@ const LOCALNET_CONFIG: WellKnownConfig = WellKnownConfig {
     min_deploy_points: DEFAULT_MIN_DEPLOY_POINTS,
     min_deployment_gas_price: DEFAULT_MIN_DEPLOYMENT_GAS_PRICE,
     block_gas_limit: DEFAULT_BLOCK_GAS_LIMIT,
+    min_tx_gas: DEFAULT_MIN_TX_GAS,
     features: [
         (FEATURE_ABI_PUBLIC_SENDER, GENESIS),
         (HQ_KECCAK256, GENESIS),
         (FEATURE_BLOB, GENESIS),
         (FEATURE_DISABLE_WASM64, GENESIS),
         (FEATURE_DISABLE_WASM32, NEVER),
         (FEATURE_DISABLE_3RD_PARTY, NEVER),
+        (FEATURE_MIN_TX_GAS, GENESIS),
     ],
 };

rusk/src/lib/node/vm/config/opt.rs

@@ -43,6 +43,9 @@ pub struct OptionalConfig {
     #[serde(default, with = "humantime_serde")]
     pub generation_timeout: Option<Duration>,
 
+    /// Minimum gas charged for any transaction.
+    pub min_tx_gas: Option<u64>,
+
     /// Set of features to activate
     #[serde(default)]
     features: HashMap<String, FeatureActivation>,
@@ -111,6 +114,12 @@ impl OptionalConfig {
             config.block_gas_limit,
         );
 
+        Self::set_or_warn(
+            "min_tx_gas",
+            &mut self.min_tx_gas,
+            config.min_tx_gas,
+        );
+
         for (feature, activation) in &config.features {
             if let Some(v) = self.feature(feature) {
                 if v != activation {
@@ -192,6 +201,9 @@ impl TryFrom<OptionalConfig> for Config {
             block_gas_limit: value
                 .block_gas_limit
                 .ok_or(anyhow!("Missing block_gas_limit"))?,
+            min_tx_gas: value
+                .min_tx_gas
+                .ok_or(anyhow!("Missing min_tx_gas"))?,
             generation_timeout: value.generation_timeout,
             features: value.features,
         })