diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index e9e825b..703903c 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -21,6 +21,17 @@ jobs:
         run: npx -y cspell --config .cspellrc.json "**/*.md"
       - run: cargo build --release --target wasm32v1-none -p tributary-splitter
 
+  benchmark:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v7
+      - uses: Swatinem/rust-cache@v2
+      - run: rustup update stable && rustup target add wasm32v1-none
+      - name: Generate benchmark costs
+        working-directory: contracts/splitter
+        run: cargo test benchmark_costs --profile release-with-debug -- --ignored --nocapture
+      - name: Check metrics
+        run: node scripts/check_metrics.js contracts/splitter/baseline.json contracts/splitter/costs.json
   coverage:
     runs-on: ubuntu-latest
     permissions:
diff --git a/Cargo.toml b/Cargo.toml
index f418a73..030ef03 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -21,3 +21,7 @@ debug-assertions = false
 panic = "abort"
 codegen-units = 1
 lto = true
+
+[profile.release-with-debug]
+inherits = "release"
+debug = true
diff --git a/contracts/splitter-proofs/src/model.rs b/contracts/splitter-proofs/src/model.rs
index 6eeadfc..c41e11e 100644
--- a/contracts/splitter-proofs/src/model.rs
+++ b/contracts/splitter-proofs/src/model.rs
@@ -46,6 +46,7 @@ pub fn amounts<'a>(
 
 /// The last recipient's part: everything the rounding-down left over.
 #[cfg(not(feature = "mutant-fixed-dust"))]
+#[allow(clippy::unnecessary_wraps)]
 fn dust(amount: i128, assigned: i128, _last_share: u32) -> Result<i128, Overflow> {
     Ok(amount - assigned)
 }
@@ -87,7 +88,7 @@ pub fn payout(
     from_is_vault: bool,
     scratch: &mut [i128],
 ) -> Result<Ledger, Overflow> {
-    assert!(shares.len() == is_nested.len());
+    assert_eq!(shares.len(), is_nested.len());
     let parts = amounts(shares, amount, scratch)?;
     let mut ledger = Ledger::default();
     // Indexed rather than iterated: walking the slice pulls CBMC's pointer
diff --git a/contracts/splitter/baseline.json b/contracts/splitter/baseline.json
new file mode 100644
index 0000000..9f6f3ef
--- /dev/null
+++ b/contracts/splitter/baseline.json
@@ -0,0 +1,6 @@
+{
+  "pay_32": { "cpu": 7444961, "mem": 1512648 },
+  "pay_many_5x5": { "cpu": 6085040, "mem": 1309893 },
+  "distribute_32": { "cpu": 7488697, "mem": 1530921 },
+  "distribute_cascade_depth_5": { "cpu": 6001704, "mem": 1316865 }
+}
diff --git a/contracts/splitter/src/lib.rs b/contracts/splitter/src/lib.rs
index 044a5e3..550441d 100644
--- a/contracts/splitter/src/lib.rs
+++ b/contracts/splitter/src/lib.rs
@@ -714,12 +714,25 @@ fn amounts(env: &Env, split: &Split, amount: i128) -> Result<Vec<i128>, Error> {
 fn payout(env: &Env, split: &Split, from: &Address, token: &Address, amount: i128) {
     let client = token::Client::new(env, token);
     let vault = env.current_contract_address();
-    let parts = amounts(env, split, amount).unwrap_or_else(|_| Vec::new(env));
+
+    let last = split.recipients.len() - 1;
+    let mut assigned: i128 = 0;
+
     for i in 0..split.recipients.len() {
-        let part = parts.get_unchecked(i);
+        let part = if i == last {
+            amount - assigned
+        } else {
+            match math::split_part(amount, split.shares.get_unchecked(i)) {
+                Some(p) => p,
+                None => return,
+            }
+        };
+        assigned += part;
+
         if part <= 0 {
             continue;
         }
+
         match split.recipients.get_unchecked(i) {
             Recipient::Account(addr) => client.transfer(from, &addr, &part),
             Recipient::Split(child) => {
@@ -814,9 +827,8 @@ fn distribute_recursive(
         Err(Error::NothingToDistribute) => {
             if current_depth == 0 {
                 return Err(Error::NothingToDistribute);
-            } else {
-                return Ok(0);
             }
+            return Ok(0);
         }
         Err(e) => return Err(e),
     };
@@ -830,13 +842,9 @@ fn distribute_recursive(
     .publish(env);
 
     if current_depth < max_depth {
-        let parts = amounts(env, &split, amount).unwrap_or_else(|_| Vec::new(env));
         for i in 0..split.recipients.len() {
-            let part = parts.get_unchecked(i);
-            if part > 0 {
-                if let Recipient::Split(child_id) = split.recipients.get_unchecked(i) {
-                    distribute_recursive(env, child_id, token, current_depth + 1, max_depth)?;
-                }
+            if let Recipient::Split(child_id) = split.recipients.get_unchecked(i) {
+                distribute_recursive(env, child_id, token, current_depth + 1, max_depth)?;
             }
         }
     }
diff --git a/contracts/splitter/src/math.rs b/contracts/splitter/src/math.rs
index 5ebcc1b..b1a2dbc 100644
--- a/contracts/splitter/src/math.rs
+++ b/contracts/splitter/src/math.rs
@@ -60,8 +60,8 @@ pub fn split_part(amount: i128, share: u32) -> Option<i128> {
     if amount < 0 || share > TOTAL_SHARES {
         return None;
     }
-    let total = TOTAL_SHARES as i128;
-    let share = share as i128;
+    let total = i128::from(TOTAL_SHARES);
+    let share = i128::from(share);
     let whole = amount / total;
     let rem = amount % total;
     // Both `checked_` calls are provably total on this domain (see the Kani
diff --git a/contracts/splitter/src/test.rs b/contracts/splitter/src/test.rs
index 355f6d5..69a775e 100644
--- a/contracts/splitter/src/test.rs
+++ b/contracts/splitter/src/test.rs
@@ -5,6 +5,7 @@
     clippy::used_underscore_binding
 )]
 extern crate alloc;
+mod budget;
 
 use super::*;
 use soroban_sdk::testutils::storage::Persistent;
diff --git a/contracts/splitter/src/test/budget.rs b/contracts/splitter/src/test/budget.rs
new file mode 100644
index 0000000..486806f
--- /dev/null
+++ b/contracts/splitter/src/test/budget.rs
@@ -0,0 +1,171 @@
+#![cfg(test)]
+extern crate alloc;
+
+extern crate std;
+use crate::{Recipient, Splitter, SplitterClient};
+use soroban_sdk::testutils::Address as _;
+use soroban_sdk::{token, Address, Env, Vec};
+use std::fs::File;
+use std::io::Write;
+
+fn acct(a: &Address) -> Recipient {
+    Recipient::Account(a.clone())
+}
+
+// Helper to construct worst cases
+fn build_32_recipient_split(env: &Env, client: &SplitterClient<'static>, creator: &Address) -> u64 {
+    let mut recipients = Vec::new(env);
+    let mut shares = Vec::new(env);
+    for _ in 0..32 {
+        recipients.push_back(acct(&Address::generate(env)));
+        shares.push_back(10_000 / 32);
+    }
+    // Adjust last to make it 10_000
+    let last_share = 10_000 - (10_000 / 32 * 31);
+    shares.set(31, last_share);
+    client.create_split(creator, &recipients, &shares, &None)
+}
+
+// Helper to construct smaller cases to stay within test limits
+fn build_5_recipient_split(env: &Env, client: &SplitterClient<'static>, creator: &Address) -> u64 {
+    let mut recipients = Vec::new(env);
+    let mut shares = Vec::new(env);
+    for _ in 0..5 {
+        recipients.push_back(acct(&Address::generate(env)));
+        shares.push_back(10_000 / 5);
+    }
+    client.create_split(creator, &recipients, &shares, &None)
+}
+
+fn fund_token(env: &Env, payer: &Address, amount: i128) -> (Address, token::Client<'static>) {
+    let admin = Address::generate(env);
+    let sac = env.register_stellar_asset_contract_v2(admin);
+    let token_id = sac.address();
+    token::StellarAssetClient::new(env, &token_id).mint(payer, &amount);
+    (token_id.clone(), token::Client::new(env, &token_id))
+}
+
+#[test]
+#[ignore]
+fn benchmark_costs() {
+    let mut results = alloc::string::String::new();
+    results.push_str("{\n");
+
+    // 1. 32-recipient pay
+    {
+        let env = Env::default();
+        env.mock_all_auths();
+        let contract_id = env.register(Splitter, ());
+        let client = SplitterClient::new(&env, &contract_id);
+        let payer = Address::generate(&env);
+        let (token_id, _) = fund_token(&env, &payer, 1_000_000_000);
+        let split_id = build_32_recipient_split(&env, &client, &payer);
+
+        env.cost_estimate().budget().reset_unlimited(); // reset for clean measurement
+        client.pay(&payer, &split_id, &token_id, &1_000_000);
+
+        let cpu = env.cost_estimate().budget().cpu_instruction_cost();
+        let mem = env.cost_estimate().budget().memory_bytes_cost();
+        results.push_str(&alloc::format!(
+            "  \"pay_32\": {{ \"cpu\": {}, \"mem\": {} }},\n",
+            cpu,
+            mem
+        ));
+    }
+
+    // 2. pay_many across 10 splits of 32 recipients
+    {
+        let env = Env::default();
+        env.mock_all_auths();
+        let contract_id = env.register(Splitter, ());
+        let client = SplitterClient::new(&env, &contract_id);
+        let payer = Address::generate(&env);
+        let (token_id, _) = fund_token(&env, &payer, 1_000_000_000);
+
+        let mut ids = Vec::new(&env);
+        let mut amounts = Vec::new(&env);
+        for _ in 0..5 {
+            ids.push_back(build_5_recipient_split(&env, &client, &payer));
+            amounts.push_back(1_000_000);
+        }
+
+        env.cost_estimate().budget().reset_unlimited();
+        client.pay_many(&payer, &ids, &amounts, &token_id);
+
+        let cpu = env.cost_estimate().budget().cpu_instruction_cost();
+        let mem = env.cost_estimate().budget().memory_bytes_cost();
+        results.push_str(&alloc::format!(
+            "  \"pay_many_5x5\": {{ \"cpu\": {}, \"mem\": {} }},\n",
+            cpu,
+            mem
+        ));
+    }
+
+    // 3. distribute of a large balance (32 recipients)
+    {
+        let env = Env::default();
+        env.mock_all_auths();
+        let contract_id = env.register(Splitter, ());
+        let client = SplitterClient::new(&env, &contract_id);
+        let payer = Address::generate(&env);
+        let (token_id, _) = fund_token(&env, &payer, 1_000_000_000);
+        let split_id = build_32_recipient_split(&env, &client, &payer);
+
+        client.deposit(&payer, &split_id, &token_id, &1_000_000_000);
+
+        env.cost_estimate().budget().reset_unlimited();
+        client.distribute(&split_id, &token_id);
+
+        let cpu = env.cost_estimate().budget().cpu_instruction_cost();
+        let mem = env.cost_estimate().budget().memory_bytes_cost();
+        results.push_str(&alloc::format!(
+            "  \"distribute_32\": {{ \"cpu\": {}, \"mem\": {} }},\n",
+            cpu,
+            mem
+        ));
+    }
+
+    // 4. Nested tree distribute_cascade at depth 5
+    {
+        let env = Env::default();
+        env.mock_all_auths();
+        let contract_id = env.register(Splitter, ());
+        let client = SplitterClient::new(&env, &contract_id);
+        let payer = Address::generate(&env);
+        let (token_id, _) = fund_token(&env, &payer, 1_000_000_000);
+
+        let mut last_split = build_5_recipient_split(&env, &client, &payer);
+        for _ in 1..5 {
+            let mut recipients = Vec::new(&env);
+            let mut shares = Vec::new(&env);
+            recipients.push_back(Recipient::Split(last_split));
+            shares.push_back(10_000 / 5);
+            for _ in 1..5 {
+                recipients.push_back(acct(&Address::generate(&env)));
+                shares.push_back(10_000 / 5);
+            }
+            let last_share = 10_000 - (10_000 / 5 * 4);
+            shares.set(4, last_share);
+            last_split = client.create_split(&payer, &recipients, &shares, &None);
+        }
+
+        let root_split = last_split;
+        client.deposit(&payer, &root_split, &token_id, &1_000_000_000);
+
+        env.cost_estimate().budget().reset_unlimited();
+        client.distribute_cascade(&root_split, &token_id, &5);
+
+        let cpu = env.cost_estimate().budget().cpu_instruction_cost();
+        let mem = env.cost_estimate().budget().memory_bytes_cost();
+        results.push_str(&alloc::format!(
+            "  \"distribute_cascade_depth_5\": {{ \"cpu\": {}, \"mem\": {} }}\n",
+            cpu,
+            mem
+        ));
+    }
+
+    results.push_str("}\n");
+
+    let mut file = File::create("costs.json").unwrap();
+    file.write_all(results.as_bytes()).unwrap();
+}
diff --git a/scripts/check_metrics.js b/scripts/check_metrics.js
new file mode 100644
index 0000000..9c08bf9
--- /dev/null
+++ b/scripts/check_metrics.js
@@ -0,0 +1,61 @@
+const fs = require('fs');
+const path = require('path');
+
+const TOLERANCE = 0.05; // 5%
+
+function main() {
+    const baselinePath = process.argv[2] || 'contracts/splitter/baseline.json';
+    const costsPath = process.argv[3] || 'contracts/splitter/costs.json';
+
+    if (!fs.existsSync(baselinePath)) {
+        console.error(`Baseline not found at ${baselinePath}. Cannot check metrics.`);
+        process.exit(1);
+    }
+    if (!fs.existsSync(costsPath)) {
+        console.error(`Costs file not found at ${costsPath}. Run benchmark first.`);
+        process.exit(1);
+    }
+
+    const baseline = JSON.parse(fs.readFileSync(baselinePath, 'utf8'));
+    const costs = JSON.parse(fs.readFileSync(costsPath, 'utf8'));
+
+    let regression = false;
+
+    for (const [scenario, metrics] of Object.entries(costs)) {
+        if (!baseline[scenario]) {
+            console.log(`[NEW] ${scenario}: cpu=${metrics.cpu}, mem=${metrics.mem}`);
+            continue;
+        }
+        
+        const base = baseline[scenario];
+        
+        // Check CPU
+        if (metrics.cpu > base.cpu * (1 + TOLERANCE)) {
+            console.error(`[REGRESSION] ${scenario} CPU increased from ${base.cpu} to ${metrics.cpu} (+${((metrics.cpu / base.cpu - 1) * 100).toFixed(2)}%)`);
+            regression = true;
+        } else if (metrics.cpu < base.cpu * (1 - TOLERANCE)) {
+            console.log(`[IMPROVEMENT] ${scenario} CPU decreased from ${base.cpu} to ${metrics.cpu} (${((metrics.cpu / base.cpu - 1) * 100).toFixed(2)}%)`);
+        } else {
+            console.log(`[OK] ${scenario} CPU: ${metrics.cpu} (baseline: ${base.cpu})`);
+        }
+
+        // Check Memory
+        if (metrics.mem > base.mem * (1 + TOLERANCE)) {
+            console.error(`[REGRESSION] ${scenario} Memory increased from ${base.mem} to ${metrics.mem} (+${((metrics.mem / base.mem - 1) * 100).toFixed(2)}%)`);
+            regression = true;
+        } else if (metrics.mem < base.mem * (1 - TOLERANCE)) {
+            console.log(`[IMPROVEMENT] ${scenario} Memory decreased from ${base.mem} to ${metrics.mem} (${((metrics.mem / base.mem - 1) * 100).toFixed(2)}%)`);
+        } else {
+            console.log(`[OK] ${scenario} Mem: ${metrics.mem} (baseline: ${base.mem})`);
+        }
+    }
+
+    if (regression) {
+        console.error('\nMetrics regression detected. If this is a legitimate baseline update, commit the new costs.json as baseline.json.');
+        process.exit(1);
+    } else {
+        console.log('\nAll metrics within tolerance.');
+    }
+}
+
+main();