diff --git a/gas-report b/gas-report
index 0d13dfa..8d8c89d 100644
--- a/gas-report
+++ b/gas-report
@@ -1,7 +1,7 @@
-Poseidon2Huff_BN254:hash_1: 14845 gas
-Poseidon2Huff_BN254:hash_2: 14845 gas
-Poseidon2Huff_BN254:hash_3: 14845 gas
-Poseidon2Yul_BN254:fallback: 19607 gas
+Poseidon2Huff_BN254:hash_1: 14869 gas
+Poseidon2Huff_BN254:hash_2: 14869 gas
+Poseidon2Huff_BN254:hash_3: 14869 gas
+Poseidon2Yul_BN254:fallback: 19639 gas
 Poseidon2_BN254:hash_1: 217702 gas
 Poseidon2_BN254:hash_2: 218222 gas
 Poseidon2_BN254:hash_3: 218801 gas
diff --git a/gas-report.sh b/gas-report.sh
index 4f47e8a..2fed5ca 100755
--- a/gas-report.sh
+++ b/gas-report.sh
@@ -9,6 +9,6 @@
 OUTPUT=$(forge test --match-contract Poseidon2Test -vvvv 2>&1 | \
   grep -E "^[[:space:]]+├─ \[[0-9]+\] (Poseidon2_BN254|Poseidon2Yul_BN254|Poseidon2Huff_BN254)::(hash_1|hash_2|hash_3|fallback)" | \
   sed 's/.*├─ \[\([0-9]*\)\] \(.*\)::\([a-z_0-9]*\).*/\2:\3: \1 gas/' | \
-  sort -u)
+  LC_ALL=C sort -u)
 
 echo "$OUTPUT" | tee gas-report
diff --git a/generate-yul.ts b/generate-yul.ts
index d514f69..ec2fd17 100644
--- a/generate-yul.ts
+++ b/generate-yul.ts
@@ -44,10 +44,10 @@ function poseidon2_core(s0: string, s1: string, s2: string, s3: string) {
   return `
     let PRIME := 0x30644e72e131a029b85045b68181585d2833e84879b9709143e1f593f0000001
 
-    let state0 := ${s0}
-    let state1 := ${s1}
-    let state2 := ${s2}
-    let state3 := ${s3}
+    let state0 := mod(${s0}, PRIME)
+    let state1 := mod(${s1}, PRIME)
+    let state2 := mod(${s2}, PRIME)
+    let state3 := mod(${s3}, PRIME)
 
     ${poseidon2_rounds()}
 `;
diff --git a/src/bn254/huff/Utils.huff b/src/bn254/huff/Utils.huff
index e3ebf65..d3384d2 100644
--- a/src/bn254/huff/Utils.huff
+++ b/src/bn254/huff/Utils.huff
@@ -27,7 +27,7 @@
 /// @notice Absorb calldata inputs into sponge state for interface-compatible hashing
 /// @dev Supports IPoseidon2 interface: hash_1(uint256), hash_2(uint256,uint256), hash_3(uint256,uint256,uint256)
 /// @dev Calldata layout: [4-byte selector][32-byte arg0][32-byte arg1][32-byte arg2]
-/// @dev User-supplied dirty calldata (>= PRIME) is acceptable; will be cleaned by S-box
+/// @dev Inputs are cleaned via mod PRIME to ensure proper field element values
 #define macro ABSORB_CALLDATA() = takes (1) returns (5) {
     // takes: [PRIME]
 
@@ -37,10 +37,16 @@
     0x5 shr                 // [(calldatasize - 4) / 32, PRIME]
     0x40 shl                // [iv, PRIME]
 
-    // Load inputs from calldata
-    0x44 calldataload       // [input2, iv, PRIME]
-    0x24 calldataload       // [input1, input2, iv, PRIME]
-    0x04 calldataload       // [input0, input1, input2, iv, PRIME]
+    // Load inputs from calldata and apply mod PRIME
+    dup2                    // [PRIME, iv, PRIME]
+    0x44 calldataload       // [input2, PRIME, iv, PRIME]
+    mod                     // [input2 % PRIME, iv, PRIME]
+    dup3                    // [PRIME, input2 % PRIME, iv, PRIME]
+    0x24 calldataload       // [input1, PRIME, input2 % PRIME, iv, PRIME]
+    mod                     // [input1 % PRIME, input2 % PRIME, iv, PRIME]
+    dup4                    // [PRIME, input1 % PRIME, input2 % PRIME, iv, PRIME]
+    0x04 calldataload       // [input0, PRIME, input1 % PRIME, input2 % PRIME, iv, PRIME]
+    mod                     // [input0 % PRIME, input1 % PRIME, input2 % PRIME, iv, PRIME]
     // returns: [state0, state1, state2, state3, PRIME]
 }
 
diff --git a/src/bn254/yul/LibPoseidon2Yul.sol b/src/bn254/yul/LibPoseidon2Yul.sol
index 3fb651b..02c89aa 100644
--- a/src/bn254/yul/LibPoseidon2Yul.sol
+++ b/src/bn254/yul/LibPoseidon2Yul.sol
@@ -23,10 +23,10 @@ library LibPoseidon2Yul {
         assembly {
             let PRIME := 0x30644e72e131a029b85045b68181585d2833e84879b9709143e1f593f0000001
 
-            let state0 := s0
-            let state1 := s1
-            let state2 := s2
-            let state3 := s3
+            let state0 := mod(s0, PRIME)
+            let state1 := mod(s1, PRIME)
+            let state2 := mod(s2, PRIME)
+            let state3 := mod(s3, PRIME)
 
             // Apply 1st linear layer
 
diff --git a/test/Poseidon2.t.sol b/test/Poseidon2.t.sol
index d9a1e6a..fd0ce8e 100644
--- a/test/Poseidon2.t.sol
+++ b/test/Poseidon2.t.sol
@@ -199,6 +199,93 @@ contract Poseidon2Test is Test {
         );
     }
 
+    // ============================================================
+    // Input sanitization tests
+    // ============================================================
+
+    function test_input_sanitization() public view {
+        // Test that inputs >= PRIME are handled correctly
+        uint256 PRIME = Field.PRIME;
+
+        // Test input = PRIME (should be treated as 0)
+        {
+            uint256 result = poseidon2Yul.hash_1(PRIME);
+            uint256 expected = poseidon2Yul.hash_1(0);
+            assertEq(result, expected, "Yul: PRIME should equal 0");
+        }
+        {
+            uint256 result = poseidon2Huff.hash_1(PRIME);
+            uint256 expected = poseidon2Huff.hash_1(0);
+            assertEq(result, expected, "Huff: PRIME should equal 0");
+        }
+
+        // Test input = PRIME + 5 (should be treated as 5)
+        {
+            uint256 result = poseidon2Yul.hash_1(PRIME + 5);
+            uint256 expected = poseidon2Yul.hash_1(5);
+            assertEq(result, expected, "Yul: PRIME+5 should equal 5");
+        }
+        {
+            uint256 result = poseidon2Huff.hash_1(PRIME + 5);
+            uint256 expected = poseidon2Huff.hash_1(5);
+            assertEq(result, expected, "Huff: PRIME+5 should equal 5");
+        }
+
+        // Test input = type(uint256).max (should be treated as type(uint256).max % PRIME)
+        {
+            uint256 maxModPrime = type(uint256).max % PRIME;
+            uint256 result = poseidon2Yul.hash_1(type(uint256).max);
+            uint256 expected = poseidon2Yul.hash_1(maxModPrime);
+            assertEq(result, expected, "Yul: uint256.max should equal max % PRIME");
+        }
+        {
+            uint256 maxModPrime = type(uint256).max % PRIME;
+            uint256 result = poseidon2Huff.hash_1(type(uint256).max);
+            uint256 expected = poseidon2Huff.hash_1(maxModPrime);
+            assertEq(result, expected, "Huff: uint256.max should equal max % PRIME");
+        }
+
+        // Test hash_2 with mixed inputs
+        {
+            uint256 result = poseidon2Yul.hash_2(PRIME + 3, PRIME + 7);
+            uint256 expected = poseidon2Yul.hash_2(3, 7);
+            assertEq(result, expected, "Yul: hash_2 sanitization");
+        }
+        {
+            uint256 result = poseidon2Huff.hash_2(PRIME + 3, PRIME + 7);
+            uint256 expected = poseidon2Huff.hash_2(3, 7);
+            assertEq(result, expected, "Huff: hash_2 sanitization");
+        }
+
+        // Test hash_2 with type(uint256).max
+        {
+            uint256 maxModPrime = type(uint256).max % PRIME;
+            uint256 result = poseidon2Yul.hash_2(type(uint256).max, type(uint256).max);
+            uint256 expected = poseidon2Yul.hash_2(maxModPrime, maxModPrime);
+            assertEq(result, expected, "Yul: hash_2 with uint256.max");
+        }
+        {
+            uint256 maxModPrime = type(uint256).max % PRIME;
+            uint256 result = poseidon2Huff.hash_2(type(uint256).max, type(uint256).max);
+            uint256 expected = poseidon2Huff.hash_2(maxModPrime, maxModPrime);
+            assertEq(result, expected, "Huff: hash_2 with uint256.max");
+        }
+
+        // Test hash_3 with type(uint256).max
+        {
+            uint256 maxModPrime = type(uint256).max % PRIME;
+            uint256 result = poseidon2Yul.hash_3(type(uint256).max, type(uint256).max, type(uint256).max);
+            uint256 expected = poseidon2Yul.hash_3(maxModPrime, maxModPrime, maxModPrime);
+            assertEq(result, expected, "Yul: hash_3 with uint256.max");
+        }
+        {
+            uint256 maxModPrime = type(uint256).max % PRIME;
+            uint256 result = poseidon2Huff.hash_3(type(uint256).max, type(uint256).max, type(uint256).max);
+            uint256 expected = poseidon2Huff.hash_3(maxModPrime, maxModPrime, maxModPrime);
+            assertEq(result, expected, "Huff: hash_3 with uint256.max");
+        }
+    }
+
     // ============================================================
     // Variable length hashing tests
     // ============================================================