diff --git a/CHANGELOG.md b/CHANGELOG.md
index 463e16ffda..6b8a45b695 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -96,6 +96,7 @@
 - [BREAKING] Fixed batch ID being serialized/deserialized and potentially not matching the serialized transaction headers ([#3061](https://github.com/0xMiden/protocol/pull/3061)).
 - Simplified the `ownable2step` ownership transitions ([#3170](https://github.com/0xMiden/protocol/pull/3170)).
 - Fixed `note_script_allowlist::assert_all_input_notes_allowed` and `tx_script_allowlist::assert_tx_script_allowed` to read the allowlist from the transaction's initial storage state via `active_account::get_initial_map_item` ([#3182](https://github.com/0xMiden/protocol/pull/3182)).
+- Fixed `eth_address::to_account_id` to validate the decoded `AccountId` structural invariants, preventing a malformed bridge-in destination address from being routed into an unspendable P2ID/MINT output ([#3231](https://github.com/0xMiden/protocol/pull/3231)).
 
 ## v0.15.2 (2026-06-05)
 
diff --git a/crates/miden-agglayer/asm/agglayer/common/eth_address.masm b/crates/miden-agglayer/asm/agglayer/common/eth_address.masm
index b9cc4a9c33..cdec50cbb3 100644
--- a/crates/miden-agglayer/asm/agglayer/common/eth_address.masm
+++ b/crates/miden-agglayer/asm/agglayer/common/eth_address.masm
@@ -1,6 +1,7 @@
 use agglayer::common::utils
 use miden::core::crypto::hashes::keccak256
 use miden::core::word
+use miden::protocol::account_id
 
 # TYPE ALIASES
 # =================================================================================================
@@ -42,9 +43,19 @@ const TWO_POW_32=4294967296
 #! The packing is done via build_felt, which validates limbs are u32 and checks the packed value
 #! did not reduce mod p (i.e. the word fits in the field).
 #!
+#! The decoded (suffix, prefix) is validated as a structurally valid AccountId, matching the Rust
+#! `EthEmbeddedAccountId::try_from_eth_address` contract. This guarantees the id is safe to use as
+#! an output target: an invalid id would otherwise be routed into an unspendable P2ID/MINT output.
+#!
 #! Inputs:  [limb0, limb1, limb2, limb3, limb4]
 #! Outputs: [suffix, prefix]
 #!
+#! Panics if:
+#! - the most-significant 4 bytes (limb0) are non-zero.
+#! - any limb is not a valid u32, or a packed 8-byte word does not fit in the field.
+#! - the decoded (suffix, prefix) is not a valid AccountId (unsupported version, suffix most
+#!   significant bit set, or suffix least significant byte non-zero).
+#!
 #! Invocation: exec
 pub proc to_account_id
     # limb0 must be 0 (most-significant limb, on top)
@@ -67,6 +78,13 @@ pub proc to_account_id
 
     swap
     # => [suffix, prefix]
+
+    # Validate the decoded id is a structurally valid AccountId before it is used as an output target.
+    dup.1 dup.1
+    # => [suffix, prefix, suffix, prefix]
+
+    exec.account_id::validate
+    # => [suffix, prefix]
 end
 
 # HELPER PROCEDURES
diff --git a/crates/miden-testing/tests/agglayer/eth_address.rs b/crates/miden-testing/tests/agglayer/eth_address.rs
new file mode 100644
index 0000000000..eaa00365fa
--- /dev/null
+++ b/crates/miden-testing/tests/agglayer/eth_address.rs
@@ -0,0 +1,98 @@
+//! Tests for `AccountId` validation in `eth_address::to_account_id`.
+//!
+//! The bridge-in claim decodes a deposit's `destinationAddress` into an `AccountId` and routes
+//! bridged value to it via a P2ID/MINT output. If the decoded id is not a valid `AccountId`, that
+//! output can never be consumed and the assets are locked.
+
+extern crate alloc;
+
+use alloc::format;
+use alloc::string::String;
+use alloc::vec::Vec;
+
+use miden_agglayer::errors::ERR_MSB_NONZERO;
+use miden_agglayer::eth_types::{AddressConversionError, EthAddress, EthEmbeddedAccountId};
+use miden_protocol::Felt;
+use miden_protocol::account::AccountId;
+use miden_protocol::errors::MasmError;
+use miden_protocol::testing::account_id::ACCOUNT_ID_REGULAR_PUBLIC_ACCOUNT_IMMUTABLE_CODE;
+
+use super::test_utils::assert_execution_fails_with;
+
+/// Message of `ERR_ACCOUNT_ID_SUFFIX_LEAST_SIGNIFICANT_BYTE_MUST_BE_ZERO` from the protocol
+/// `account_id.masm`. It has no exported Rust constant, so we mirror the string (matched by code).
+const ERR_SUFFIX_LSB_NONZERO: MasmError =
+    MasmError::from_static_str("least significant byte of the account ID suffix must be zero");
+
+/// Builds a script that pushes the 5 address limbs (`limb0` on top) and runs `to_account_id`.
+///
+/// `truncate_stack` lets a non-reverting run finish cleanly, so a missing revert surfaces as a
+/// successful execution rather than a stack error.
+fn to_account_id_script(addr: &EthAddress) -> String {
+    let limbs: Vec<u64> = addr.to_elements().iter().map(|f| f.as_canonical_u64()).collect();
+    format!(
+        "use miden::core::sys
+use agglayer::common::eth_address
+
+begin
+    push.{}.{}.{}.{}.{}
+    exec.eth_address::to_account_id
+    exec.sys::truncate_stack
+end",
+        limbs[4], limbs[3], limbs[2], limbs[1], limbs[0]
+    )
+}
+
+/// Returns an embedded-form address that decodes into a structurally invalid `AccountId` (suffix
+/// least-significant byte non-zero), plus its decoded `(suffix, prefix)`. Built from a valid
+/// `AccountId` with only the suffix LSB flipped, so `account_id::validate` fails on that check.
+fn crafted_invalid_embedded_address() -> (EthAddress, Felt, Felt) {
+    let valid_id = AccountId::try_from(ACCOUNT_ID_REGULAR_PUBLIC_ACCOUNT_IMMUTABLE_CODE).unwrap();
+    let mut bytes = EthEmbeddedAccountId::from_account_id(valid_id).to_bytes();
+
+    // suffix = bytes[12..20] (big-endian), so byte 19 is its least-significant byte. A valid
+    // AccountId always has this byte zero; set it to make the suffix structurally invalid.
+    assert_eq!(bytes[19], 0, "a valid AccountId must have a zero suffix least-significant byte");
+    bytes[19] = 1;
+
+    let prefix_u64 = u64::from_be_bytes(bytes[4..12].try_into().unwrap());
+    let suffix_u64 = u64::from_be_bytes(bytes[12..20].try_into().unwrap());
+    let prefix = Felt::try_from(prefix_u64).unwrap();
+    let suffix = Felt::try_from(suffix_u64).unwrap();
+
+    (EthAddress::new(bytes), suffix, prefix)
+}
+
+/// Case A: a non-embedded destination (non-zero most-significant 4 bytes) hard-traps in
+/// `to_account_id`, so the committed claim is deterministically unclaimable. Unchanged by the fix.
+#[tokio::test]
+async fn to_account_id_rejects_non_embedded_address() {
+    // A real-looking EVM address: the top 4 bytes are non-zero, so it is not an embedded AccountId.
+    let addr = EthAddress::from_hex("0xdeadbeefcafebabe0badf00d0011223344556677").unwrap();
+    assert_execution_fails_with(&to_account_id_script(&addr), &ERR_MSB_NONZERO).await;
+}
+
+/// Evidence that the crafted destination really is an invalid `AccountId`: the Rust reference
+/// conversion rejects it, so the on-chain path accepting it is a genuine gap.
+#[test]
+fn crafted_invalid_account_id_is_rejected_by_rust() {
+    let (bad_addr, suffix, prefix) = crafted_invalid_embedded_address();
+
+    // The Rust embedded-address conversion (used off-chain to build CLAIM notes) rejects it...
+    assert_eq!(
+        EthEmbeddedAccountId::try_from(bad_addr),
+        Err(AddressConversionError::InvalidAccountId),
+    );
+
+    // ...precisely because the decoded (suffix, prefix) is not a structurally valid AccountId.
+    assert!(AccountId::try_from_elements(suffix, prefix).is_err());
+}
+
+/// Case B (the core bug): an embedded destination that decodes into a structurally invalid
+/// `AccountId` must be rejected. Before the fix `to_account_id` accepts it (this test fails,
+/// reproducing the bug); after the fix it reverts with the suffix least-significant-byte error.
+#[tokio::test]
+async fn to_account_id_rejects_structurally_invalid_account_id() {
+    let (bad_addr, _suffix, _prefix) = crafted_invalid_embedded_address();
+    assert_execution_fails_with(&to_account_id_script(&bad_addr), &ERR_SUFFIX_LSB_NONZERO).await;
+}
diff --git a/crates/miden-testing/tests/agglayer/mod.rs b/crates/miden-testing/tests/agglayer/mod.rs
index cf2362ca00..eeab6a29ca 100644
--- a/crates/miden-testing/tests/agglayer/mod.rs
+++ b/crates/miden-testing/tests/agglayer/mod.rs
@@ -2,6 +2,7 @@ pub mod asset_conversion;
 mod bridge_in;
 mod bridge_out;
 mod config_bridge;
+mod eth_address;
 mod faucet_helpers;
 mod global_index;
 mod leaf_utils;
diff --git a/crates/miden-testing/tests/agglayer/solidity_miden_address_conversion.rs b/crates/miden-testing/tests/agglayer/solidity_miden_address_conversion.rs
index 17b42685df..55ec2db8cc 100644
--- a/crates/miden-testing/tests/agglayer/solidity_miden_address_conversion.rs
+++ b/crates/miden-testing/tests/agglayer/solidity_miden_address_conversion.rs
@@ -14,7 +14,6 @@ use miden_processor::{
     Program,
     StackInputs,
 };
-use miden_protocol::Felt;
 use miden_protocol::account::AccountId;
 use miden_protocol::address::NetworkId;
 use miden_protocol::testing::account_id::{
@@ -25,6 +24,8 @@ use miden_protocol::testing::account_id::{
     AccountIdBuilder,
 };
 use miden_protocol::transaction::TransactionKernel;
+use miden_protocol::{Felt, ProtocolLib};
+use miden_standards::StandardsLib;
 
 /// Execute a program with default host
 async fn execute_program_with_default_host(
@@ -42,6 +43,12 @@ async fn execute_program_with_default_host(
         host.register_handler(event_name, handler)?;
     }
 
+    let protocol_lib = ProtocolLib::default();
+    host.load_library(protocol_lib.mast_forest()).unwrap();
+
+    let standards_lib = StandardsLib::default();
+    host.load_library(standards_lib.mast_forest()).unwrap();
+
     let asset_conversion_lib = agglayer_library();
     host.load_library(asset_conversion_lib.mast_forest()).unwrap();
 
diff --git a/crates/miden-testing/tests/agglayer/test_utils.rs b/crates/miden-testing/tests/agglayer/test_utils.rs
index 3c6490edc3..ade3f287bc 100644
--- a/crates/miden-testing/tests/agglayer/test_utils.rs
+++ b/crates/miden-testing/tests/agglayer/test_utils.rs
@@ -23,9 +23,11 @@ use miden_processor::{
     Program,
     StackInputs,
 };
+use miden_protocol::ProtocolLib;
 use miden_protocol::errors::MasmError;
 use miden_protocol::transaction::TransactionKernel;
 use miden_protocol::utils::sync::LazyLock;
+use miden_standards::StandardsLib;
 
 // EMBEDDED TEST VECTOR JSON FILES
 // ================================================================================================
@@ -63,6 +65,12 @@ pub async fn execute_program_with_default_host(
         host.register_handler(event_name, handler)?;
     }
 
+    let protocol_lib = ProtocolLib::default();
+    host.load_library(protocol_lib.mast_forest()).unwrap();
+
+    let standards_lib = StandardsLib::default();
+    host.load_library(standards_lib.mast_forest()).unwrap();
+
     let agglayer_lib = agglayer_library();
     host.load_library(agglayer_lib.mast_forest()).unwrap();