diff --git a/Cargo.lock b/Cargo.lock
index 6dd5b588..d0395448 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4524,6 +4524,7 @@ dependencies = [
  "borsh",
  "bridge_core",
  "clock_core",
+ "cross_zone_inbox_core",
  "env_logger",
  "faucet_core",
  "hex",
@@ -4531,6 +4532,7 @@ dependencies = [
  "k256",
  "lee_core",
  "log",
+ "ping_core",
  "rand 0.8.6",
  "risc0-binfmt",
  "risc0-build",
@@ -7133,6 +7135,14 @@ version = "0.2.17"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a89322df9ebe1c1578d689c92318e070967d1042b512afbe49518723f4e6d5cd"
 
+[[package]]
+name = "ping_core"
+version = "0.1.0"
+dependencies = [
+ "lee_core",
+ "serde",
+]
+
 [[package]]
 name = "pkcs1"
 version = "0.7.5"
@@ -7409,6 +7419,7 @@ dependencies = [
  "cross_zone_outbox_core",
  "faucet_core",
  "lee_core",
+ "ping_core",
  "risc0-zkvm",
  "serde",
  "token_core",
diff --git a/Cargo.toml b/Cargo.toml
index 1b15f129..0fd60a92 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -26,6 +26,7 @@ members = [
   "programs/vault/core",
   "programs/cross_zone_outbox/core",
   "programs/cross_zone_inbox/core",
+  "programs/ping/core",
   "lez/sequencer/core",
   "lez/sequencer/service",
   "lez/sequencer/service/protocol",
@@ -84,6 +85,7 @@ bridge_core = { path = "programs/bridge/core" }
 vault_core = { path = "programs/vault/core" }
 cross_zone_outbox_core = { path = "programs/cross_zone_outbox/core" }
 cross_zone_inbox_core = { path = "programs/cross_zone_inbox/core" }
+ping_core = { path = "programs/ping/core" }
 test_program_methods = { path = "test_program_methods" }
 testnet_initial_state = { path = "lez/testnet_initial_state" }
 keycard_wallet = { path = "lez/keycard_wallet" }
diff --git a/artifacts/program_methods/ping_receiver.bin b/artifacts/program_methods/ping_receiver.bin
new file mode 100644
index 00000000..e5c1680e
Binary files /dev/null and b/artifacts/program_methods/ping_receiver.bin differ
diff --git a/lee/state_machine/Cargo.toml b/lee/state_machine/Cargo.toml
index 8777db09..7337cb47 100644
--- a/lee/state_machine/Cargo.toml
+++ b/lee/state_machine/Cargo.toml
@@ -34,6 +34,8 @@ risc0-binfmt = "3.0.2"
 lee_core = { workspace = true, features = ["test_utils"] }
 token_core.workspace = true
 authenticated_transfer_core.workspace = true
+cross_zone_inbox_core.workspace = true
+ping_core.workspace = true
 test_program_methods.workspace = true
 
 env_logger.workspace = true
diff --git a/lee/state_machine/src/cross_zone_dispatch_tests.rs b/lee/state_machine/src/cross_zone_dispatch_tests.rs
new file mode 100644
index 00000000..aab90e85
--- /dev/null
+++ b/lee/state_machine/src/cross_zone_dispatch_tests.rs
@@ -0,0 +1,104 @@
+#![expect(
+    clippy::tests_outside_test_module,
+    clippy::arithmetic_side_effects,
+    reason = "We don't care about these in tests"
+)]
+
+use std::collections::BTreeMap;
+
+use cross_zone_inbox_core::{
+    CrossZoneMessage, InboxConfig, Instruction, inbox_config_account_id,
+    inbox_seen_shard_account_id,
+};
+use lee_core::account::Account;
+use ping_core::{ReceiverInstruction, ping_record_pda};
+
+use crate::{
+    V03State,
+    program::Program,
+    public_transaction::{Message, WitnessSet},
+    validated_state_diff::ValidatedStateDiff,
+};
+
+/// Drives `cross_zone_inbox::Dispatch` directly through the state machine
+/// (no watcher) and asserts the message is delivered to `ping_receiver`, which
+/// records the payload into its own PDA.
+#[test]
+fn inbox_dispatch_delivers_payload_to_ping_receiver() {
+    let mut state = V03State::new_with_genesis_accounts(&[], vec![], 0);
+    // ping_receiver is a throwaway demo target, registered only in this test state.
+    state.insert_program(Program::ping_receiver());
+
+    let inbox_id = Program::cross_zone_inbox().id();
+    let receiver_id = Program::ping_receiver().id();
+
+    let self_zone = [1_u8; 32];
+    let src_zone = [2_u8; 32];
+    let src_block_id = 5;
+
+    // Seed the inbox config account (inbox-owned) allowing src_zone -> ping_receiver.
+    let mut allowed_targets = BTreeMap::new();
+    allowed_targets.insert(src_zone, vec![receiver_id]);
+    let config = InboxConfig {
+        self_zone,
+        allowed_peers: BTreeMap::new(),
+        allowed_targets,
+    };
+    let config_id = inbox_config_account_id(inbox_id);
+    state.force_insert_account(
+        config_id,
+        Account {
+            program_owner: inbox_id,
+            balance: 0_u128,
+            data: config
+                .to_bytes()
+                .try_into()
+                .expect("config fits in account data"),
+            nonce: 0_u128.into(),
+        },
+    );
+
+    // The payload is the ping_receiver instruction, serialized as risc0 words in
+    // little-endian bytes (the contract the inbox reverses when forwarding).
+    let inner = b"hello-cross-zone".to_vec();
+    let words = risc0_zkvm::serde::to_vec(&ReceiverInstruction::Record {
+        payload: inner.clone(),
+    })
+    .expect("serialize ping instruction");
+    let payload: Vec<u8> = words.iter().flat_map(|word| word.to_le_bytes()).collect();
+
+    let msg = CrossZoneMessage {
+        src_zone,
+        src_block_id,
+        src_tx_index: 0,
+        src_program_id: [9_u32; 8],
+        target_program_id: receiver_id,
+        payload,
+        l1_inclusion_witness: None,
+    };
+
+    let seen_id = inbox_seen_shard_account_id(inbox_id, &src_zone, src_block_id);
+    let record_id = ping_record_pda(receiver_id);
+
+    let message = Message::try_new(
+        inbox_id,
+        vec![config_id, seen_id, record_id],
+        vec![],
+        Instruction::Dispatch(msg),
+    )
+    .expect("build dispatch message");
+    let tx = crate::PublicTransaction::new(message, WitnessSet::from_raw_parts(vec![]));
+
+    let diff = ValidatedStateDiff::from_public_transaction(&tx, &state, 1, 0)
+        .expect("dispatch must validate and execute");
+    let public_diff = diff.public_diff();
+
+    let record = public_diff
+        .get(&record_id)
+        .expect("ping record account must change");
+    assert_eq!(
+        record.data.clone().into_inner(),
+        inner,
+        "ping_receiver must record the delivered payload"
+    );
+}
diff --git a/lee/state_machine/src/lib.rs b/lee/state_machine/src/lib.rs
index 129821b5..87dfd513 100644
--- a/lee/state_machine/src/lib.rs
+++ b/lee/state_machine/src/lib.rs
@@ -33,6 +33,9 @@ mod signature;
 mod state;
 mod validated_state_diff;
 
+#[cfg(test)]
+mod cross_zone_dispatch_tests;
+
 pub mod program_methods {
     include!(concat!(env!("OUT_DIR"), "/program_methods/mod.rs"));
 }
diff --git a/lee/state_machine/src/program.rs b/lee/state_machine/src/program.rs
index bf48afd8..8b71448b 100644
--- a/lee/state_machine/src/program.rs
+++ b/lee/state_machine/src/program.rs
@@ -12,8 +12,8 @@ use crate::{
         AMM_ELF, AMM_ID, ASSOCIATED_TOKEN_ACCOUNT_ELF, ASSOCIATED_TOKEN_ACCOUNT_ID,
         AUTHENTICATED_TRANSFER_ELF, AUTHENTICATED_TRANSFER_ID, BRIDGE_ELF, BRIDGE_ID, CLOCK_ELF,
         CLOCK_ID, CROSS_ZONE_INBOX_ELF, CROSS_ZONE_INBOX_ID, CROSS_ZONE_OUTBOX_ELF,
-        CROSS_ZONE_OUTBOX_ID, FAUCET_ELF, FAUCET_ID, PINATA_ELF, PINATA_ID, TOKEN_ELF, TOKEN_ID,
-        VAULT_ELF, VAULT_ID,
+        CROSS_ZONE_OUTBOX_ID, FAUCET_ELF, FAUCET_ID, PINATA_ELF, PINATA_ID, PING_RECEIVER_ELF,
+        PING_RECEIVER_ID, TOKEN_ELF, TOKEN_ID, VAULT_ELF, VAULT_ID,
     },
 };
 
@@ -190,6 +190,14 @@ impl Program {
             elf: CROSS_ZONE_INBOX_ELF.to_vec(),
         }
     }
+
+    #[must_use]
+    pub fn ping_receiver() -> Self {
+        Self {
+            id: PING_RECEIVER_ID,
+            elf: PING_RECEIVER_ELF.to_vec(),
+        }
+    }
 }
 
 // TODO: Testnet only. Refactor to prevent compilation on mainnet.
diff --git a/lee/state_machine/src/state.rs b/lee/state_machine/src/state.rs
index 110f3113..949c9920 100644
--- a/lee/state_machine/src/state.rs
+++ b/lee/state_machine/src/state.rs
@@ -711,6 +711,11 @@ pub mod tests {
             this.insert(Program::vault().id(), Program::vault());
             this.insert(Program::faucet().id(), Program::faucet());
             this.insert(Program::bridge().id(), Program::bridge());
+            this.insert(
+                Program::cross_zone_outbox().id(),
+                Program::cross_zone_outbox(),
+            );
+            this.insert(Program::cross_zone_inbox().id(), Program::cross_zone_inbox());
             this
         };
 
diff --git a/program_methods/guest/Cargo.toml b/program_methods/guest/Cargo.toml
index d7572235..318af4b6 100644
--- a/program_methods/guest/Cargo.toml
+++ b/program_methods/guest/Cargo.toml
@@ -22,5 +22,6 @@ bridge_core.workspace = true
 vault_core.workspace = true
 cross_zone_outbox_core.workspace = true
 cross_zone_inbox_core.workspace = true
+ping_core.workspace = true
 risc0-zkvm.workspace = true
 serde = { workspace = true, default-features = false }
diff --git a/program_methods/guest/src/bin/ping_receiver.rs b/program_methods/guest/src/bin/ping_receiver.rs
new file mode 100644
index 00000000..567736da
--- /dev/null
+++ b/program_methods/guest/src/bin/ping_receiver.rs
@@ -0,0 +1,47 @@
+use lee_core::{
+    account::AccountWithMetadata,
+    program::{AccountPostState, Claim, ProgramInput, ProgramOutput, read_lee_inputs},
+};
+use ping_core::{ReceiverInstruction, ping_record_pda, ping_record_seed};
+
+fn main() {
+    let (
+        ProgramInput {
+            self_program_id,
+            caller_program_id,
+            pre_states,
+            instruction,
+        },
+        instruction_words,
+    ) = read_lee_inputs::<ReceiverInstruction>();
+
+    assert!(
+        caller_program_id.is_some(),
+        "ping_receiver is only callable through a chained call"
+    );
+
+    let payload = match instruction {
+        ReceiverInstruction::Record { payload } => payload,
+    };
+
+    let [record] = <[AccountWithMetadata; 1]>::try_from(pre_states)
+        .expect("Record requires exactly 1 account");
+    assert_eq!(
+        record.account_id,
+        ping_record_pda(self_program_id),
+        "Account must be the ping record PDA"
+    );
+
+    let mut post_account = record.account.clone();
+    post_account.data = payload.try_into().expect("payload fits in account data");
+    let post = AccountPostState::new_claimed_if_default(post_account, Claim::Pda(ping_record_seed()));
+
+    ProgramOutput::new(
+        self_program_id,
+        caller_program_id,
+        instruction_words,
+        vec![record],
+        vec![post],
+    )
+    .write();
+}
diff --git a/programs/ping/core/Cargo.toml b/programs/ping/core/Cargo.toml
new file mode 100644
index 00000000..29870630
--- /dev/null
+++ b/programs/ping/core/Cargo.toml
@@ -0,0 +1,12 @@
+[package]
+name = "ping_core"
+version = "0.1.0"
+edition = "2024"
+license = { workspace = true }
+
+[lints]
+workspace = true
+
+[dependencies]
+lee_core.workspace = true
+serde = { workspace = true, features = ["alloc"] }
diff --git a/programs/ping/core/src/lib.rs b/programs/ping/core/src/lib.rs
new file mode 100644
index 00000000..f6b5b963
--- /dev/null
+++ b/programs/ping/core/src/lib.rs
@@ -0,0 +1,25 @@
+use lee_core::{
+    account::AccountId,
+    program::{PdaSeed, ProgramId},
+};
+use serde::{Deserialize, Serialize};
+
+const PING_RECORD_SEED: [u8; 32] = *b"/LEZ/v0.3/PingRecord/0000000000/";
+
+/// Instruction delivered to `ping_receiver` by the inbox: record the payload.
+#[derive(Clone, Debug, PartialEq, Eq, Serialize, Deserialize)]
+pub enum ReceiverInstruction {
+    Record { payload: Vec<u8> },
+}
+
+/// The account a `ping_receiver` records the latest delivered payload into.
+#[must_use]
+pub fn ping_record_pda(receiver_id: ProgramId) -> AccountId {
+    AccountId::for_public_pda(&receiver_id, &ping_record_seed())
+}
+
+/// Seed of the record PDA, exposed so the guest can claim the account.
+#[must_use]
+pub fn ping_record_seed() -> PdaSeed {
+    PdaSeed::new(PING_RECORD_SEED)
+}