diff --git a/Cargo.lock b/Cargo.lock
index ae47dd5..e7aa18b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1337,9 +1337,9 @@ dependencies = [
 
 [[package]]
 name = "soroban-ledger-snapshot"
-version = "25.0.2"
+version = "25.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ab9d1bfa6f7d57307bf8241789b13d3703438e7afa0527aa098a357ef757d3a2"
+checksum = "760124fb65a2acdea7d241b8efdfab9a39287ae8dc5bf8feb6fd9dfb664c1ad5"
 dependencies = [
  "serde",
  "serde_json",
@@ -1358,9 +1358,9 @@ dependencies = [
 
 [[package]]
 name = "soroban-sdk"
-version = "25.0.2"
+version = "25.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "9953e782d6da30974eea520c2b5f624c28bbc518c3bb926ec581242dd3f9d2a2"
+checksum = "5fb27e93f8d3fc3a815d24c60ec11e893c408a36693ec9c823322f954fa096ae"
 dependencies = [
  "arbitrary",
  "bytes-lit",
@@ -1382,9 +1382,9 @@ dependencies = [
 
 [[package]]
 name = "soroban-sdk-macros"
-version = "25.0.2"
+version = "25.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "8a8cecb6acc735670dad3303c6a9d2b47e51adfb11224ad5a8ced55fd7b0a600"
+checksum = "dec603a62a90abdef898f8402471a24d8b58a0043b9a998ed6a607a19a5dabe1"
 dependencies = [
  "darling 0.20.11",
  "heck",
@@ -1402,11 +1402,12 @@ dependencies = [
 
 [[package]]
 name = "soroban-spec"
-version = "25.0.2"
+version = "25.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c79501d0636f86fe2c9b1dd7e88b9397415b3493a59b34f466abd7758c84b92b"
+checksum = "24718fac3af127fc6910eb6b1d3ccd8403201b6ef0aca73b5acabe4bc3dd42ed"
 dependencies = [
  "base64",
+ "sha2",
  "stellar-xdr",
  "thiserror",
  "wasmparser",
@@ -1414,9 +1415,9 @@ dependencies = [
 
 [[package]]
 name = "soroban-spec-rust"
-version = "25.0.2"
+version = "25.3.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b520b5fb013fde70796d9a6057591f53817aa0c38f8bad460126f97f59394af9"
+checksum = "93c558bca7a693ec8ed67d2d8c8f5b300f3772141d619a4a694ad5dd48461256"
 dependencies = [
  "prettyplease",
  "proc-macro2",
diff --git a/Cargo.toml b/Cargo.toml
index 19b20f0..9d1aad6 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -14,7 +14,7 @@ rust-version = "1.84.0"
 license = "Apache-2.0"
 
 [workspace.dependencies]
-soroban-sdk = "25.0.2"
+soroban-sdk = "25.3.0"
 soroban-poseidon = { path = "." }
 
 [package]
diff --git a/README.md b/README.md
index 3ec8299..87ed5ec 100644
--- a/README.md
+++ b/README.md
@@ -82,7 +82,7 @@ let hash2 = sponge.compute_hash(&inputs2);
 
 ## Limitations / Future Work
 
-1. **Multi-round absorption**: Currently, inputs must fit within a single rate (i.e., `inputs.len() <= T - 1`). Future versions will support absorbing inputs larger than the state size across multiple permutation rounds.
+1. **Multi-round absorption**: Currently, for Poseidon, inputs must exactly fill the rate (i.e., `inputs.len() == T - 1`), matching circom's behavior where `nInputs` determines `T = nInputs + 1`. Poseidon2 requires inputs to fit within a single rate (i.e., `inputs.len() <= T - 1`). Future versions will support absorbing inputs larger than the state size across multiple permutation rounds.
 
 2. **Persistent parameters**: Make `PoseidonParams` / `Poseidon2Params` a `#[contracttype]` so they can be stored as contract data and reduce the contract size.
 
diff --git a/src/lib.rs b/src/lib.rs
index 33d402b..9786e7b 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -62,7 +62,7 @@ impl Field for BlsScalar {
 ///
 /// # Type Parameters
 ///
-/// - `T`: State size. Must be ≥ `inputs.len() + 1` (rate = T-1, capacity = 1).
+/// - `T`: State size. Must equal `inputs.len() + 1` (rate = T-1, capacity = 1).
 /// - `F`: Field type. Use [`BnScalar`] for BN254 or [`BlsScalar`] for BLS12-381.
 ///
 /// # Supported Configurations
@@ -72,8 +72,7 @@ impl Field for BlsScalar {
 ///
 /// # Panics
 ///
-/// - if `inputs.is_empty()`
-/// - if `inputs.len() > T - 1` (rate exceeded)
+/// - if `inputs.len() != T - 1`
 /// - if any input value ≥ the field modulus (inputs must be valid field elements)
 ///
 /// # Example
diff --git a/src/poseidon/sponge.rs b/src/poseidon/sponge.rs
index 54f8e71..3e7ec56 100644
--- a/src/poseidon/sponge.rs
+++ b/src/poseidon/sponge.rs
@@ -217,7 +217,10 @@ where
     }
 
     pub(crate) fn absorb(&mut self, inputs: &Vec<U256>) {
-        assert!(inputs.len() <= Self::RATE);
+        assert!(
+            inputs.len() == Self::RATE,
+            "Poseidon: inputs.len() must equal rate (T - 1)"
+        );
         let modulus = F::modulus(&self.env);
         for i in 0..inputs.len() {
             let v = inputs.get_unchecked(i);
@@ -243,15 +246,13 @@ where
     /// implementation](https://github.com/iden3/circomlib/blob/master/circuits/poseidon.circom).
     ///
     /// # Panics
-    /// - if `inputs.is_empty()`. Empty inputs are not allowed because
-    ///   `hash([])` would collide with `hash([0])`. Circom also disallows empty
-    ///   inputs.
-    /// - if `inputs.len() > RATE` (i.e., `T - 1`). For larger inputs,
-    ///   multi-round absorption would be needed (not yet implemented).
+    /// - if `inputs.len() != RATE` (i.e., must equal `T - 1` exactly).
+    ///   This matches circom's Poseidon where `nInputs` determines
+    ///   `T = nInputs + 1`, ensuring the rate is always fully used and
+    ///   preventing suffix-zero collisions from implicit zero-padding.
     /// - if any input value is greater than or equal to the field modulus.
     ///   All inputs must be valid field elements (i.e., less than the modulus).
     pub fn compute_hash(&mut self, inputs: &Vec<U256>) -> U256 {
-        assert!(!inputs.is_empty(), "Poseidon: inputs cannot be empty");
         self.reset_state();
         self.absorb(inputs);
         self.squeeze()
diff --git a/src/poseidon2/sponge.rs b/src/poseidon2/sponge.rs
index a45f27a..b7abdae 100644
--- a/src/poseidon2/sponge.rs
+++ b/src/poseidon2/sponge.rs
@@ -174,8 +174,13 @@ where
     }
 
     pub(crate) fn absorb(&mut self, inputs: &Vec<U256>) {
-        // Absorb into rate portion of state (positions 0..RATE)
-        assert!(inputs.len() <= Self::RATE);
+        // <= is safe here because IV = input_len << 64 provides domain
+        // separation for different-length inputs. This differs from Poseidon V1
+        // (which uses IV=0 and therefore requires == RATE).
+        assert!(
+            inputs.len() <= Self::RATE,
+            "Poseidon2: inputs.len() must not exceed rate (T - 1)"
+        );
         let modulus = F::modulus(&self.env);
         for i in 0..inputs.len() {
             let v = inputs.get_unchecked(i);
diff --git a/src/tests/poseidon.rs b/src/tests/poseidon.rs
index 9fe735a..aeaf8f3 100644
--- a/src/tests/poseidon.rs
+++ b/src/tests/poseidon.rs
@@ -711,45 +711,23 @@ fn test_poseidon_sponge_matches_hash_function() {
 }
 
 // ============================================================================
-// Partial rate tests (inputs.len() < RATE)
+// Partial rate rejection tests
 // ============================================================================
 
-// Note: Circom's Poseidon always uses T = inputs.len() + 1 (full rate), so there are
-// no reference test vectors for partial rate scenarios. These tests verify that:
-// 1. Our implementation handles partial rate correctly (zero-padding)
-// 2. Results are deterministic
-// 3. Different T values produce different results (as expected)
+// Poseidon V1 requires inputs.len() == RATE (full rate), matching circom's
+// behavior where nInputs determines T = nInputs + 1. Partial-rate inputs are
+// rejected to prevent suffix-zero collisions from implicit zero-padding.
 
-// Test hashing 1 input with T=3 (rate=2) - partial rate usage
-// This verifies zero-padding works correctly when inputs don't fill the rate
 #[test]
-fn test_poseidon_bn254_partial_rate_t3_1_input() {
+#[should_panic(expected = "inputs.len() must equal rate")]
+fn test_poseidon_bn254_rejects_partial_rate() {
     let env = Env::default();
 
-    // 1 input with T=3 (rate=2) - only half the rate is used
-    let inputs = vec![
-        &env,
-        U256::from_be_bytes(
-            &env,
-            &bytesn!(
-                &env,
-                0x0000000000000000000000000000000000000000000000000000000000000001
-            )
-            .into(),
-        ),
-    ];
+    // 1 input with T=3 (rate=2) - partial rate must be rejected
+    let inputs = vec![&env, U256::from_u32(&env, 1)];
 
     let mut sponge = PoseidonSponge::<3, BnScalar>::new(&env);
-    let result = sponge.compute_hash(&inputs);
-
-    // Result should be deterministic
-    let result2 = sponge.compute_hash(&inputs);
-    assert_eq!(result, result2);
-
-    // Verify it's different from using T=2 (full rate with 1 input)
-    let mut sponge_t2 = PoseidonSponge::<2, BnScalar>::new(&env);
-    let result_t2 = sponge_t2.compute_hash(&inputs);
-    assert_ne!(result, result_t2);
+    sponge.compute_hash(&inputs); // should panic
 }
 
 // ============================================================================
@@ -757,7 +735,7 @@ fn test_poseidon_bn254_partial_rate_t3_1_input() {
 // ============================================================================
 
 #[test]
-#[should_panic(expected = "assertion failed")]
+#[should_panic(expected = "inputs.len() must equal rate")]
 fn test_poseidon_sponge_inputs_exceed_rate() {
     let env = Env::default();
 
@@ -896,15 +874,9 @@ fn test_poseidon_bls12_381_input_below_modulus_accepted() {
     let _ = sponge.compute_hash(&inputs);
 }
 
-// Empty inputs are explicitly rejected in Poseidon because:
-// 1. Circom rejects them
-// 2. With IV=0, hash([]) would collide with hash([0]) since both result in
-//    permuting state [0, 0, ...]
-//
-// This differs from Poseidon2, which uses IV = `input_len << 64`, making
-// hash([]) and hash([0]) produce different outputs.
+// Empty inputs are rejected because inputs.len() must equal RATE (>= 1).
 #[test]
-#[should_panic(expected = "Poseidon: inputs cannot be empty")]
+#[should_panic(expected = "inputs.len() must equal rate")]
 fn test_poseidon_bn254_empty_inputs_rejected() {
     let env = Env::default();
 
diff --git a/src/tests/poseidon2.rs b/src/tests/poseidon2.rs
index 9423013..3492130 100644
--- a/src/tests/poseidon2.rs
+++ b/src/tests/poseidon2.rs
@@ -852,7 +852,7 @@ fn test_poseidon2_bn254_partial_rate_t4_2_inputs() {
 // ============================================================================
 
 #[test]
-#[should_panic(expected = "assertion failed")]
+#[should_panic(expected = "Poseidon2: inputs.len() must not exceed rate (T - 1)")]
 fn test_poseidon2_sponge_inputs_exceed_rate_t4() {
     let env = Env::default();