diff --git a/emmarin/cl/cl/src/cl/output.rs b/emmarin/cl/cl/src/cl/output.rs
index a1fc8e4..604ef66 100644
--- a/emmarin/cl/cl/src/cl/output.rs
+++ b/emmarin/cl/cl/src/cl/output.rs
@@ -6,7 +6,7 @@ use crate::cl::{
     NullifierSecret,
 };
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
+#[derive(Debug, Clone, Copy, Hash, PartialEq, Eq, Serialize, Deserialize)]
 pub struct Output {
     pub note_comm: NoteCommitment,
 }
diff --git a/emmarin/cl/cl/src/cl/pact.rs b/emmarin/cl/cl/src/cl/pact.rs
index 3f5f3e1..b231bc9 100644
--- a/emmarin/cl/cl/src/cl/pact.rs
+++ b/emmarin/cl/cl/src/cl/pact.rs
@@ -1,5 +1,5 @@
-use crate::zone_layer::ZoneId;
 use crate::cl::{PartialTx, PartialTxWitness};
+use crate::zone_layer::notes::ZoneId;
 use serde::{Deserialize, Serialize};
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize)]
diff --git a/emmarin/cl/cl/src/zone_layer/ledger.rs b/emmarin/cl/cl/src/zone_layer/ledger.rs
new file mode 100644
index 0000000..11acbe6
--- /dev/null
+++ b/emmarin/cl/cl/src/zone_layer/ledger.rs
@@ -0,0 +1,55 @@
+use crate::cl::{merkle, NoteCommitment, Nullifier};
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
+pub struct Ledger {
+    cm_root: [u8; 32],
+    nf_root: [u8; 32],
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct LedgerWitness {
+    pub commitments: Vec<NoteCommitment>,
+    pub nullifiers: Vec<Nullifier>,
+}
+
+const MAX_COMM: usize = 256;
+const MAX_NULL: usize = 256;
+
+impl LedgerWitness {
+    pub fn commit(&self) -> Ledger {
+        Ledger {
+            cm_root: self.cm_root(),
+            nf_root: self.nf_root(),
+        }
+    }
+
+    pub fn nf_root(&self) -> [u8; 32] {
+        let bytes = self
+            .nullifiers
+            .iter()
+            .map(|i| i.as_bytes().to_vec())
+            .collect::<Vec<_>>();
+        merkle::root(merkle::padded_leaves::<MAX_NULL>(&bytes))
+    }
+
+    pub fn cm_root(&self) -> [u8; 32] {
+        let bytes = self
+            .commitments
+            .iter()
+            .map(|i| i.as_bytes().to_vec())
+            .collect::<Vec<_>>();
+        merkle::root(merkle::padded_leaves::<MAX_COMM>(&bytes))
+    }
+
+    pub fn cm_path(&self, cm: &NoteCommitment) -> Option<Vec<merkle::PathNode>> {
+        let bytes = self
+            .commitments
+            .iter()
+            .map(|i| i.as_bytes().to_vec())
+            .collect::<Vec<_>>();
+        let leaves = merkle::padded_leaves::<MAX_COMM>(&bytes);
+        let idx = self.commitments.iter().position(|c| c == cm)?;
+        Some(merkle::path(leaves, idx))
+    }
+}
diff --git a/emmarin/cl/cl/src/zone_layer/mod.rs b/emmarin/cl/cl/src/zone_layer/mod.rs
index 1487ef7..20710b3 100644
--- a/emmarin/cl/cl/src/zone_layer/mod.rs
+++ b/emmarin/cl/cl/src/zone_layer/mod.rs
@@ -1,66 +1,3 @@
-use crate::cl::{merkle, Constraint, NoteCommitment, Nullifier};
-use serde::{Deserialize, Serialize};
-
-pub struct ZoneNote {
-    pub stf: Constraint,
-    pub state: State,
-    pub ledger: Ledger,
-    pub id: [u8; 32],
-}
-
-pub type State = [u8; 32];
-#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
-pub struct Ledger {
-    cm_root: [u8; 32],
-    nf_root: [u8; 32],
-}
-
-pub type ZoneId = [u8; 32];
-pub struct StateWitness;
-
-#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
-pub struct LedgerWitness {
-    pub commitments: Vec<NoteCommitment>,
-    pub nullifiers: Vec<Nullifier>,
-}
-
-const MAX_COMM: usize = 256;
-const MAX_NULL: usize = 256;
-
-impl LedgerWitness {
-    pub fn commit(&self) -> Ledger {
-        Ledger {
-            cm_root: self.cm_root(),
-            nf_root: self.nf_root(),
-        }
-    }
-
-    pub fn nf_root(&self) -> [u8; 32] {
-        let bytes = self
-            .nullifiers
-            .iter()
-            .map(|i| i.as_bytes().to_vec())
-            .collect::<Vec<_>>();
-        merkle::root(merkle::padded_leaves::<MAX_NULL>(&bytes))
-    }
-
-    pub fn cm_root(&self) -> [u8; 32] {
-        let bytes = self
-            .commitments
-            .iter()
-            .map(|i| i.as_bytes().to_vec())
-            .collect::<Vec<_>>();
-        merkle::root(merkle::padded_leaves::<MAX_COMM>(&bytes))
-    }
-
-    pub fn cm_path(&self, cm: &NoteCommitment) -> Option<Vec<merkle::PathNode>> {
-        let bytes = self
-            .commitments
-            .iter()
-            .map(|i| i.as_bytes().to_vec())
-            .collect::<Vec<_>>();
-        let leaves = merkle::padded_leaves::<MAX_COMM>(&bytes);
-        let idx = self.commitments.iter().position(|c| c == cm)?;
-        Some(merkle::path(leaves, idx))
-    }
-}
+pub mod ledger;
+pub mod notes;
+pub mod tx;
diff --git a/emmarin/cl/cl/src/zone_layer/notes.rs b/emmarin/cl/cl/src/zone_layer/notes.rs
new file mode 100644
index 0000000..8adf0e4
--- /dev/null
+++ b/emmarin/cl/cl/src/zone_layer/notes.rs
@@ -0,0 +1,14 @@
+use super::ledger::Ledger;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
+pub struct ZoneNote {
+    pub stf: Stf,
+    pub state: State,
+    pub ledger: Ledger,
+    pub id: [u8; 32],
+}
+
+pub type Stf = [u8; 32];
+pub type ZoneId = [u8; 32];
+pub type State = [u8; 32];
diff --git a/emmarin/cl/cl/src/zone_layer/tx.rs b/emmarin/cl/cl/src/zone_layer/tx.rs
new file mode 100644
index 0000000..02bb511
--- /dev/null
+++ b/emmarin/cl/cl/src/zone_layer/tx.rs
@@ -0,0 +1,24 @@
+use super::notes::ZoneNote;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct UpdateBundle {
+    pub updates: Vec<ZoneUpdate>,
+}
+
+#[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
+pub struct ZoneUpdate {
+    pub old: ZoneNote,
+    pub new: ZoneNote,
+}
+
+impl ZoneUpdate {
+    pub fn new(old: ZoneNote, new: ZoneNote) -> Self {
+        assert_eq!(old.id, new.id);
+        Self { old, new }
+    }
+
+    pub fn well_formed(&self) -> bool {
+        self.old.id == self.new.id
+    }
+}
diff --git a/emmarin/cl/ledger/src/ledger.rs b/emmarin/cl/ledger/src/ledger.rs
index b955cc7..6fab328 100644
--- a/emmarin/cl/ledger/src/ledger.rs
+++ b/emmarin/cl/ledger/src/ledger.rs
@@ -7,7 +7,7 @@ use crate::{
     pact::ProvedPact,
     partial_tx::ProvedPartialTx,
 };
-use cl::zone_layer::{LedgerWitness, ZoneId};
+use cl::zone_layer::{ledger::LedgerWitness, notes::ZoneId};
 
 pub struct ProvedLedgerTransition {
     pub public: LedgerProofPublic,
@@ -101,26 +101,7 @@ impl ProvedLedgerTransition {
         })
     }
 
-    pub fn public(&self) -> Result<LedgerProofPublic> {
-        Ok(self.risc0_receipt.journal.decode()?)
-    }
-
     pub fn verify(&self) -> bool {
-        // let Ok(proved_ptx_inputs) = self.public() else {
-        //     return false;
-        // };
-        // let expected_ptx_inputs = PtxPublic {
-        //     ptx: self.ptx.clone(),
-        //     cm_root: self.cm_root,
-        //     from: self.from,
-        //     to: self.to,
-        // };
-        // if expected_ptx_inputs != proved_ptx_inputs {
-        //     return false;
-        // }
-
-        // let ptx_root = self.ptx.root();
-
         self.risc0_receipt
             .verify(ledger_validity_proof::LEDGER_ID)
             .is_ok()
diff --git a/emmarin/cl/ledger/src/lib.rs b/emmarin/cl/ledger/src/lib.rs
index e95c59c..93be05a 100644
--- a/emmarin/cl/ledger/src/lib.rs
+++ b/emmarin/cl/ledger/src/lib.rs
@@ -4,5 +4,7 @@ pub mod error;
 pub mod ledger;
 pub mod pact;
 pub mod partial_tx;
+pub mod stf;
+pub mod zone_update;
 
 pub use constraint::ConstraintProof;
diff --git a/emmarin/cl/ledger/src/partial_tx.rs b/emmarin/cl/ledger/src/partial_tx.rs
index 29a333a..6a1c614 100644
--- a/emmarin/cl/ledger/src/partial_tx.rs
+++ b/emmarin/cl/ledger/src/partial_tx.rs
@@ -2,7 +2,7 @@ use ledger_proof_statements::ptx::{PtxPrivate, PtxPublic};
 
 use crate::error::{Error, Result};
 use cl::cl::{merkle, PartialTx, PartialTxWitness};
-use cl::zone_layer::ZoneId;
+use cl::zone_layer::notes::ZoneId;
 
 pub struct ProvedPartialTx {
     pub ptx: PartialTx,
diff --git a/emmarin/cl/ledger/src/stf.rs b/emmarin/cl/ledger/src/stf.rs
new file mode 100644
index 0000000..f416008
--- /dev/null
+++ b/emmarin/cl/ledger/src/stf.rs
@@ -0,0 +1,33 @@
+use cl::zone_layer::notes::Stf;
+use ledger_proof_statements::stf::StfPublic;
+
+#[derive(Debug, Clone)]
+pub struct StfProof {
+    pub risc0_id: [u32; 8],
+    pub public: StfPublic,
+    pub risc0_receipt: risc0_zkvm::Receipt,
+}
+
+pub fn risc0_constraint(risc0_id: [u32; 8]) -> Stf {
+    // TODO: hash
+
+    unsafe { core::mem::transmute::<[u32; 8], [u8; 32]>(risc0_id) }
+}
+
+impl StfProof {
+    pub fn from_risc0(risc0_id: [u32; 8], risc0_receipt: risc0_zkvm::Receipt) -> Self {
+        Self {
+            risc0_id,
+            public: risc0_receipt.journal.decode().unwrap(),
+            risc0_receipt,
+        }
+    }
+
+    pub fn stf(&self) -> Stf {
+        risc0_constraint(self.risc0_id)
+    }
+
+    pub fn verify(&self) -> bool {
+        self.risc0_receipt.verify(self.risc0_id).is_ok()
+    }
+}
diff --git a/emmarin/cl/ledger/src/zone_update.rs b/emmarin/cl/ledger/src/zone_update.rs
new file mode 100644
index 0000000..efcb251
--- /dev/null
+++ b/emmarin/cl/ledger/src/zone_update.rs
@@ -0,0 +1,103 @@
+pub use crate::error::{Error, Result};
+use crate::{ledger::ProvedLedgerTransition, stf::StfProof};
+use cl::zone_layer::tx::UpdateBundle;
+use std::collections::HashSet;
+
+pub struct ProvedUpdateBundle {
+    pub bundle: UpdateBundle,
+    pub ledger_proofs: Vec<ProvedLedgerTransition>,
+    pub stf_proofs: Vec<StfProof>,
+}
+
+impl ProvedUpdateBundle {
+    // pub fn prove(bundle_witness: &BundleWitness) -> Result<Self> {
+    //     // need to show that bundle is balanced.
+    //     // i.e. the sum of ptx balances is 0
+
+    //     let bundle_private = BundlePrivate {
+    //         balances: bundle_witness
+    //             .partials
+    //             .iter()
+    //             .map(|ptx| ptx.balance())
+    //             .collect(),
+    //     };
+
+    //     let env = risc0_zkvm::ExecutorEnv::builder()
+    //         .write(&bundle_private)
+    //         .unwrap()
+    //         .build()
+    //         .unwrap();
+
+    //     let prover = risc0_zkvm::default_prover();
+
+    //     let start_t = std::time::Instant::now();
+
+    //     let opts = risc0_zkvm::ProverOpts::succinct();
+    //     let prove_info = prover
+    //         .prove_with_opts(env, nomos_cl_risc0_proofs::BUNDLE_ELF, &opts)
+    //         .map_err(|_| Error::Risc0ProofFailed)?;
+
+    //     println!(
+    //         "STARK 'bundle' prover time: {:.2?}, total_cycles: {}",
+    //         start_t.elapsed(),
+    //         prove_info.stats.total_cycles
+    //     );
+
+    //     let receipt = prove_info.receipt;
+
+    //     Ok(Self {
+    //         bundle: receipt.journal.decode()?,
+    //         risc0_receipt: receipt,
+    //     })
+    // }
+
+    pub fn verify(&self) -> bool {
+        let mut consumed_commitments = HashSet::new();
+        let mut produced_commitments = HashSet::new();
+        for proof in &self.ledger_proofs {
+            if !proof.verify() {
+                return false;
+            }
+
+            for comm in &proof.public.cross_out {
+                if produced_commitments.insert(comm) {
+                    // already in?
+                }
+            }
+            for comm in &proof.public.cross_in {
+                if consumed_commitments.insert(comm) {
+                    // already in?
+                }
+            }
+        }
+
+        // check that cross zone transactions match
+        if consumed_commitments != produced_commitments {
+            return false;
+        }
+
+        for ((update, stf_proof), ledger_proof) in self
+            .bundle
+            .updates
+            .iter()
+            .zip(self.stf_proofs.iter())
+            .zip(self.ledger_proofs.iter())
+        {
+            if !update.well_formed() {
+                return false;
+            }
+
+            if ledger_proof.public.old_ledger != update.old.ledger
+                || ledger_proof.public.ledger != update.new.ledger
+            {
+                return false;
+            }
+
+            if stf_proof.public.old != update.old || stf_proof.public.new != update.new {
+                return false;
+            }
+        }
+
+        true
+    }
+}
diff --git a/emmarin/cl/ledger_proof_statements/src/ledger.rs b/emmarin/cl/ledger_proof_statements/src/ledger.rs
index 04700fd..ed3d728 100644
--- a/emmarin/cl/ledger_proof_statements/src/ledger.rs
+++ b/emmarin/cl/ledger_proof_statements/src/ledger.rs
@@ -2,11 +2,15 @@ use crate::bundle::BundlePublic;
 use crate::pact::PactPublic;
 use crate::ptx::PtxPublic;
 use cl::cl::Output;
-use cl::zone_layer::*;
+use cl::zone_layer::{
+    ledger::{Ledger, LedgerWitness},
+    notes::ZoneId,
+};
 use serde::{Deserialize, Serialize};
 
 #[derive(Debug, Clone, PartialEq, Serialize, Deserialize)]
 pub struct LedgerProofPublic {
+    pub old_ledger: Ledger,
     pub ledger: Ledger,
     pub id: ZoneId,
     pub cross_in: Vec<Output>,
diff --git a/emmarin/cl/ledger_proof_statements/src/lib.rs b/emmarin/cl/ledger_proof_statements/src/lib.rs
index 12c64c5..fa0941c 100644
--- a/emmarin/cl/ledger_proof_statements/src/lib.rs
+++ b/emmarin/cl/ledger_proof_statements/src/lib.rs
@@ -3,3 +3,4 @@ pub mod constraint;
 pub mod ledger;
 pub mod pact;
 pub mod ptx;
+pub mod stf;
diff --git a/emmarin/cl/ledger_proof_statements/src/stf.rs b/emmarin/cl/ledger_proof_statements/src/stf.rs
new file mode 100644
index 0000000..22eb9cc
--- /dev/null
+++ b/emmarin/cl/ledger_proof_statements/src/stf.rs
@@ -0,0 +1,8 @@
+use cl::zone_layer::notes::ZoneNote;
+use serde::{Deserialize, Serialize};
+
+#[derive(Debug, Clone, Copy, PartialEq, Serialize, Deserialize)]
+pub struct StfPublic {
+    pub old: ZoneNote,
+    pub new: ZoneNote,
+}
diff --git a/emmarin/cl/ledger_validity_proof/ledger/src/main.rs b/emmarin/cl/ledger_validity_proof/ledger/src/main.rs
index 06cedcb..55bf280 100644
--- a/emmarin/cl/ledger_validity_proof/ledger/src/main.rs
+++ b/emmarin/cl/ledger_validity_proof/ledger/src/main.rs
@@ -1,4 +1,7 @@
-use cl::{zones::*, Output};
+use cl::{
+    cl::Output,
+    zone_layer::{ledger::LedgerWitness, notes::ZoneId},
+};
 use ledger_proof_statements::{bundle::*, constraint::*, ledger::*, pact::PactPublic, ptx::*};
 use risc0_zkvm::{guest::env, serde};
 
@@ -9,6 +12,8 @@ fn main() {
         txs,
     } = env::read();
 
+    let old_ledger = ledger.commit();
+
     let cm_root = ledger.cm_root();
 
     let mut cross_in = vec![];
@@ -30,6 +35,7 @@ fn main() {
     }
 
     env::commit(&LedgerProofPublic {
+        old_ledger,
         ledger: ledger.commit(),
         id,
         cross_in,