feat(escrow_wip): build_unsigned_escrow_deposit builder

Plutus V3 spend with continuing-output state transition. Validator runs
Deposit { contributor } redeemer.

v1 limitation: ADA-only deposits. Multi-asset deposits are deferred —
Aiken's flat_merge uses right-fold which produces REVERSED appended-
policy ordering vs naive forward iteration. Single-entry net_added
(lovelace-only) trivially collapses any ordering ambiguity, so Rust's
existing value_merge matches Aiken's flat_merge byte-for-byte for v1.

Mirrors all six validator checks client-side as preflight (state==Open,
contributor in {a,b}, signed_by, continuing-output exists, datum equal
except deposits, deposits canonicality). 9 unit tests cover both
negative paths and happy-path datum mutations (new entry append,
existing entry merge, immutable fields preserved).

Inlines V3 validator CBOR in the tx witness for v1; reference-script
optimization is a v2 follow-up. Sets V3 cost model via language_view
to satisfy script_data_hash.

crates/aldabra-dao/src/builder/escrow_deposit.rs

@@ -0,0 +1,624 @@
+//! Build an unsigned `escrow_deposit_unsigned` transaction.
+//!
+//! ⚠️  WIP / UNAUDITED. Feature-gated behind `escrow_wip`.
+//!
+//! ## What this tx does
+//!
+//! Plutus V3 spend of an existing escrow UTxO with a continuing-output
+//! state transition (only `deposits` field mutated). Validator runs
+//! `Deposit { contributor }` redeemer.
+//!
+//! - **Inputs**:
+//!   - The escrow UTxO at `escrow_script_address` (Plutus V3 spend,
+//!     redeemer = `Deposit { contributor }`).
+//!   - One funding wallet UTxO covering `add_lovelace + fee + change_min`.
+//! - **Collateral**: 1 ADA-only ≥5 ADA wallet UTxO (separate from funding).
+//! - **Outputs**:
+//!   - Continuing escrow UTxO at the same script address. Inline datum =
+//!     old datum with `deposits` mutated; lovelace = old + add_lovelace;
+//!     pre-existing native assets preserved bit-exact.
+//!   - Wallet change.
+//! - **Disclosed signer**: `contributor_pkh` (validator's `signed_by` check).
+//!
+//! ## v1 limitation: ADA-only deposits
+//!
+//! The validator enforces canonicality via:
+//!
+//! ```text
+//! cbor.serialise(expected_deposits_after) == cbor.serialise(new_d.deposits)
+//! ```
+//!
+//! where `expected_deposits_after` is computed in Aiken via right-fold
+//! over `flat_merge`. Right-fold + multi-entry `net_added` produces
+//! REVERSED appended-policy ordering. Mirroring that exactly off-chain
+//! is doable but a v2 enhancement.
+//!
+//! For v1 we restrict each Deposit tx to lovelace-only (`net_added` is
+//! a single-entry `EscrowValue` — `[(empty_policy, [(empty_name, qty)])]`).
+//! Single-entry foldr / forward-iter produce identical results, so
+//! Rust's `value_merge` matches Aiken's `flat_merge` byte-for-byte
+//! regardless of iteration direction.
+//!
+//! Multi-asset deposit shapes (token + ADA, multiple distinct tokens,
+//! etc.) are deferred until we mirror the foldr ordering exactly AND
+//! verify byte-equality via golden CBOR captured from the on-chain
+//! validator.
+//!
+//! ## What the validator enforces (must match)
+//!
+//! From `aiken-escrow/validators/escrow.ak` Deposit branch:
+//!
+//! 1. `d.state == Open` (escrow not yet agreed/finalised).
+//! 2. `contributor == d.party_a || contributor == d.party_b`.
+//! 3. `signed_by(self, contributor)`.
+//! 4. Continuing output exists at `script_addr` with parsable inline datum.
+//! 5. New datum equals old datum in every field except `deposits`
+//!    (party_a/b/recipient/open_deadline_ms/lock_period_ms/state preserved).
+//! 6. New datum's `deposits` matches `expected_deposits_after(d.deposits,
+//!    contributor, value_to_flat(new_value - in_value))` byte-for-byte
+//!    via `cbor.serialise`.
+//!
+//! All six are preflighted client-side here so a misshaped tx never
+//! reaches the chain (and thus never burns collateral).
+
+use pallas_codec::minicbor;
+use pallas_crypto::hash::Hash;
+use pallas_txbuilder::{BuildConway, ExUnits, Input, Output, ScriptKind, StagingTransaction};
+
+use crate::agora::escrow::{
+    value_merge, EscrowDatum, EscrowDeposit, EscrowRedeemer, EscrowState, EscrowValue, PKH_LEN,
+};
+use crate::config::{DaoConfig, DaoNetwork};
+use crate::error::{DaoError, DaoResult};
+
+use super::proposal_create::{
+    parse_address, parse_script_hash, parse_tx_hash, WalletUtxo, MIN_COLLATERAL_LOVELACE,
+};
+
+/// Generous-but-bounded ExUnits budget for the escrow Deposit redeemer.
+/// Refine via Koios `tx_evaluate` once we have a live tx to evaluate.
+pub const ESCROW_SPEND_EX_UNITS: ExUnits = ExUnits {
+    mem: 5_000_000,
+    steps: 2_000_000_000,
+};
+
+/// Conway-era min UTxO floor we apply to the continuing escrow output.
+/// Real value depends on serialized output size; this is a generous
+/// bound that covers the escrow datum + token shapes we expect.
+pub const ESCROW_OUTPUT_MIN_LOVELACE: u64 = 2_000_000;
+
+/// Wallet-change min-UTxO floor.
+const WALLET_CHANGE_MIN_LOVELACE: u64 = 1_000_000;
+
+/// On-chain escrow state being spent.
+#[derive(Debug, Clone)]
+pub struct EscrowUtxoIn {
+    pub tx_hash_hex: String,
+    pub output_index: u32,
+    pub lovelace: u64,
+    /// Native assets currently locked alongside the lovelace. Preserved
+    /// bit-exact onto the continuing output (Deposit doesn't move tokens
+    /// in v1 — only lovelace). Each tuple: `(policy_hex, name_hex, qty)`.
+    pub assets: Vec<(String, String, u64)>,
+    /// Current EscrowDatum decoded from the inline datum. Caller fetches
+    /// via `escrow_show` / Koios.
+    pub datum: EscrowDatum,
+}
+
+/// Args bundle for [`build_unsigned_escrow_deposit`].
+#[derive(Debug, Clone)]
+pub struct EscrowDepositArgs {
+    pub cfg: DaoConfig,
+    /// Bech32 address of the deployed escrow validator script. Continuing
+    /// output goes here. Must match `escrow_in`'s on-chain address.
+    pub escrow_script_address: String,
+    /// Compiled Plutus V3 UPLC bytecode of the escrow validator. Inlined
+    /// in the tx witness for v1; reference-script optimization is a v2
+    /// follow-up.
+    pub validator_script_cbor: Vec<u8>,
+    pub escrow_in: EscrowUtxoIn,
+    /// Depositing party's payment-credential hash. Must equal
+    /// `escrow_in.datum.party_a` or `escrow_in.datum.party_b`.
+    pub contributor_pkh: [u8; PKH_LEN],
+    /// Lovelace being added to the escrow on this tx. v1 restriction:
+    /// ADA-only deposits. Must be > 0. Output min-utxo floor still
+    /// applies after the merge.
+    pub add_lovelace: u64,
+    /// Caller's bech32 base address (for change).
+    pub change_address: String,
+    /// Caller's spendable wallet UTxOs (must include 1 ADA-only utxo
+    /// ≥5 ADA for collateral and 1 ADA-only funding utxo).
+    pub wallet_utxos: Vec<WalletUtxo>,
+    /// Chain tip slot (sets `valid_from_slot`).
+    pub tip_slot: u64,
+    /// Tx upper-bound slot (sets `invalid_from_slot`). Validator does NOT
+    /// enforce time bounds on Deposit — caller can set freely (commonly
+    /// `tip_slot + 1800` for a 30-minute window).
+    pub validity_upper_slot: u64,
+    /// Estimated total fee. Caller-supplied for v1; refine via real
+    /// evaluator + size measurement later.
+    pub fee_lovelace: u64,
+    /// ExUnits budget for the spend redeemer. Defaults to
+    /// [`ESCROW_SPEND_EX_UNITS`].
+    pub ex_units: ExUnits,
+}
+
+/// What [`build_unsigned_escrow_deposit`] returns.
+#[derive(Debug, Clone)]
+pub struct UnsignedEscrowDeposit {
+    /// Hex-encoded CBOR of the unsigned tx body.
+    pub tx_cbor_hex: String,
+    /// Blake2b-256 hash of the tx body.
+    pub tx_hash_hex: String,
+    /// The script address where the continuing escrow lives.
+    pub escrow_script_address: String,
+    /// Hex-encoded CBOR of the new (post-deposit) escrow datum.
+    pub new_datum_cbor_hex: String,
+    /// Lovelace locked at the continuing output (= old + add_lovelace).
+    pub new_escrow_lovelace: u64,
+    /// Human-readable summary for MCP wrappers.
+    pub summary: String,
+}
+
+/// Build the unsigned escrow_deposit tx.
+pub fn build_unsigned_escrow_deposit(args: EscrowDepositArgs) -> DaoResult<UnsignedEscrowDeposit> {
+    let datum_in = &args.escrow_in.datum;
+
+    // ---- preflight ----------------------------------------------------------
+    //
+    // Rules numbered against the validator's Deposit branch (see module docstring).
+
+    // (1) state must be Open.
+    if datum_in.state != EscrowState::Open {
+        return Err(DaoError::State(format!(
+            "escrow state is {:?}, must be Open to accept deposits",
+            datum_in.state
+        )));
+    }
+
+    // (2) contributor must be a or b.
+    if args.contributor_pkh != datum_in.party_a && args.contributor_pkh != datum_in.party_b {
+        return Err(DaoError::State(
+            "contributor_pkh is neither party_a nor party_b — only escrow parties can deposit"
+                .into(),
+        ));
+    }
+
+    // v1 ADA-only restriction: add_lovelace > 0, no native assets being added.
+    if args.add_lovelace == 0 {
+        return Err(DaoError::State(
+            "add_lovelace must be > 0 — Deposit tx with zero net value would still pay fees"
+                .into(),
+        ));
+    }
+
+    // The continuing output's lovelace must clear the floor.
+    let new_escrow_lovelace = args
+        .escrow_in
+        .lovelace
+        .checked_add(args.add_lovelace)
+        .ok_or_else(|| DaoError::State("escrow output lovelace overflow".into()))?;
+    if new_escrow_lovelace < ESCROW_OUTPUT_MIN_LOVELACE {
+        return Err(DaoError::State(format!(
+            "continuing escrow output lovelace {new_escrow_lovelace} < min {ESCROW_OUTPUT_MIN_LOVELACE}"
+        )));
+    }
+
+    // ---- compute new datum --------------------------------------------------
+    //
+    // For v1 ADA-only deposits, single-entry `net_added` makes Rust
+    // `value_merge` byte-equivalent to Aiken `flat_merge` regardless of
+    // fold direction (only one b_entry to process).
+
+    let net_added = EscrowValue::ada(args.add_lovelace);
+    let mut new_deposits = datum_in.deposits.clone();
+    let pos = new_deposits
+        .iter()
+        .position(|d| d.contributor == args.contributor_pkh);
+    match pos {
+        Some(i) => {
+            new_deposits[i].value = value_merge(&new_deposits[i].value, &net_added);
+        }
+        None => {
+            new_deposits.push(EscrowDeposit {
+                contributor: args.contributor_pkh,
+                value: net_added,
+            });
+        }
+    }
+
+    let new_datum = EscrowDatum {
+        party_a: datum_in.party_a,
+        party_b: datum_in.party_b,
+        recipient: datum_in.recipient,
+        open_deadline_ms: datum_in.open_deadline_ms,
+        lock_period_ms: datum_in.lock_period_ms,
+        state: EscrowState::Open,
+        deposits: new_deposits,
+    };
+    let new_datum_pd = new_datum.to_plutus_data()?;
+    let new_datum_cbor = minicbor::to_vec(&new_datum_pd)
+        .map_err(|e| DaoError::Cbor(format!("new escrow datum encode: {e}")))?;
+
+    // ---- redeemer -----------------------------------------------------------
+
+    let redeemer_pd = EscrowRedeemer::Deposit {
+        contributor: args.contributor_pkh,
+    }
+    .to_plutus_data()?;
+    let redeemer_cbor = minicbor::to_vec(&redeemer_pd)
+        .map_err(|e| DaoError::Cbor(format!("deposit redeemer encode: {e}")))?;
+
+    // ---- pick funding + collateral -----------------------------------------
+
+    let mut ada_only: Vec<WalletUtxo> = args
+        .wallet_utxos
+        .iter()
+        .filter(|u| u.is_ada_only())
+        .cloned()
+        .collect();
+    ada_only.sort_by_key(|u| std::cmp::Reverse(u.lovelace));
+
+    let collateral = ada_only
+        .iter()
+        .rev()
+        .find(|u| u.lovelace >= MIN_COLLATERAL_LOVELACE)
+        .ok_or_else(|| {
+            DaoError::State(format!(
+                "no ada-only wallet UTxO ≥ {MIN_COLLATERAL_LOVELACE} lovelace for collateral"
+            ))
+        })?
+        .clone();
+
+    let funding = ada_only
+        .iter()
+        .find(|u| {
+            !(u.tx_hash_hex == collateral.tx_hash_hex && u.output_index == collateral.output_index)
+        })
+        .cloned()
+        .ok_or_else(|| {
+            DaoError::State(
+                "need a SECOND ada-only wallet UTxO to fund the deposit (separate from collateral)"
+                    .into(),
+            )
+        })?;
+
+    // ---- balance + change ---------------------------------------------------
+    //
+    // total_in  = escrow_in.lovelace + funding.lovelace
+    // outputs   = new_escrow_lovelace + change + fee
+    // change    = total_in - new_escrow_lovelace - fee
+
+    let total_in = args
+        .escrow_in
+        .lovelace
+        .checked_add(funding.lovelace)
+        .ok_or_else(|| DaoError::State("input lovelace overflow".into()))?;
+    let total_out = new_escrow_lovelace
+        .checked_add(args.fee_lovelace)
+        .ok_or_else(|| DaoError::State("output lovelace overflow".into()))?;
+    let change_lovelace = total_in.checked_sub(total_out).ok_or_else(|| {
+        DaoError::State(format!(
+            "insufficient input: total_in={total_in} need={total_out} \
+             (escrow_out={new_escrow_lovelace} + fee={})",
+            args.fee_lovelace
+        ))
+    })?;
+    if change_lovelace > 0 && change_lovelace < WALLET_CHANGE_MIN_LOVELACE {
+        return Err(DaoError::State(format!(
+            "change lovelace {change_lovelace} below min UTxO ({WALLET_CHANGE_MIN_LOVELACE}); top up wallet"
+        )));
+    }
+
+    // ---- assemble pallas StagingTransaction --------------------------------
+
+    let escrow_addr = parse_address(&args.escrow_script_address)?;
+    let change_addr = parse_address(&args.change_address)?;
+
+    let escrow_input = Input::new(
+        parse_tx_hash(&args.escrow_in.tx_hash_hex)?,
+        args.escrow_in.output_index as u64,
+    );
+    let funding_input = Input::new(
+        parse_tx_hash(&funding.tx_hash_hex)?,
+        funding.output_index as u64,
+    );
+    let collateral_input = Input::new(
+        parse_tx_hash(&collateral.tx_hash_hex)?,
+        collateral.output_index as u64,
+    );
+
+    let network_id = match args.cfg.network {
+        DaoNetwork::Mainnet => 1u8,
+        DaoNetwork::Preprod | DaoNetwork::Preview => 0u8,
+    };
+
+    // Continuing escrow output: same address, new lovelace, preserve any
+    // pre-existing native assets bit-exact, new inline datum.
+    let mut new_escrow_output = Output::new(escrow_addr, new_escrow_lovelace)
+        .set_inline_datum(new_datum_cbor.clone());
+    for (policy_hex, name_hex, qty) in &args.escrow_in.assets {
+        let policy = parse_script_hash(policy_hex)?;
+        let name = hex::decode(name_hex)
+            .map_err(|e| DaoError::Config(format!("escrow_in asset name hex: {e}")))?;
+        new_escrow_output = new_escrow_output
+            .add_asset(policy, name, *qty)
+            .map_err(|e| DaoError::Backend(format!("preserve escrow asset: {e}")))?;
+    }
+
+    let mut staging = StagingTransaction::new();
+    // Two regular inputs: escrow (script) + funding (wallet).
+    staging = staging.input(escrow_input.clone());
+    staging = staging.input(funding_input);
+    staging = staging.collateral_input(collateral_input);
+    // Continuing escrow output, then change.
+    staging = staging.output(new_escrow_output);
+    if change_lovelace > 0 {
+        let mut change_output = Output::new(change_addr, change_lovelace);
+        for (policy_hex, name_hex, qty) in &funding.assets {
+            let policy = parse_script_hash(policy_hex)?;
+            let name = hex::decode(name_hex)
+                .map_err(|e| DaoError::Config(format!("funding asset name hex: {e}")))?;
+            change_output = change_output
+                .add_asset(policy, name, *qty)
+                .map_err(|e| DaoError::Backend(format!("add asset to change: {e}")))?;
+        }
+        staging = staging.output(change_output);
+    }
+
+    // Inline the V3 validator script (v1 — no ref-script).
+    staging = staging.script(ScriptKind::PlutusV3, args.validator_script_cbor);
+    staging = staging.add_spend_redeemer(escrow_input, redeemer_cbor, Some(args.ex_units));
+
+    staging = staging.fee(args.fee_lovelace).network_id(network_id);
+
+    // Validity range — Deposit doesn't enforce time bounds, but we set
+    // them so the tx isn't valid forever.
+    staging = staging.valid_from_slot(args.tip_slot);
+    staging = staging.invalid_from_slot(args.validity_upper_slot);
+
+    // Disclosed signer: contributor pkh (validator's `signed_by` check).
+    staging = staging.disclosed_signer(Hash::<28>::from(args.contributor_pkh));
+
+    // V3 cost model — required for script_data_hash. Without it the
+    // chain rejects with PPViewHashesDontMatch.
+    staging = staging.language_view(
+        ScriptKind::PlutusV3,
+        aldabra_core::plutus_cost_models::PLUTUS_V3_COST_MODEL_PREPROD.to_vec(),
+    );
+
+    let built = staging
+        .build_conway_raw()
+        .map_err(|e| DaoError::Backend(format!("build_conway_raw: {e}")))?;
+
+    let tx_cbor_hex = hex::encode(&built.tx_bytes.0);
+    let tx_hash_hex = hex::encode(built.tx_hash.0);
+
+    let summary = format!(
+        "escrow_deposit_unsigned: contributor={} +{} lovelace → {} lovelace at {} (fee={})",
+        hex::encode(args.contributor_pkh),
+        args.add_lovelace,
+        new_escrow_lovelace,
+        args.escrow_script_address,
+        args.fee_lovelace,
+    );
+
+    Ok(UnsignedEscrowDeposit {
+        tx_cbor_hex,
+        tx_hash_hex,
+        escrow_script_address: args.escrow_script_address,
+        new_datum_cbor_hex: hex::encode(&new_datum_cbor),
+        new_escrow_lovelace,
+        summary,
+    })
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::config::ScriptRefs;
+
+    fn pkh(seed: u8) -> [u8; PKH_LEN] {
+        [seed; PKH_LEN]
+    }
+
+    fn sample_cfg() -> DaoConfig {
+        DaoConfig {
+            name: "sulkta-escrow".into(),
+            description: None,
+            governor_addr: "addr_test1wpyt48l".repeat(3),
+            stakes_addr: "addr_test1wpyt48l".repeat(3),
+            treasury_addr: "addr_test1wpyt48l".repeat(3),
+            gov_token_policy: "00".repeat(28),
+            gov_token_name_hex: "".into(),
+            initial_spend: format!("{}#0", "00".repeat(32)),
+            max_cosigners: 5,
+            treasury_ref_config: "00".repeat(28),
+            network: DaoNetwork::Preprod,
+            proposal_addr: None,
+            stake_st_policy: None,
+            proposal_st_policy: None,
+            script_refs: ScriptRefs::default(),
+        }
+    }
+
+    /// Stub script CBOR — V3 always-true (`\46\01\00\00\32\22`). Real builds
+    /// pass the compiled escrow validator UPLC.
+    fn stub_v3_script() -> Vec<u8> {
+        vec![0x46, 0x01, 0x00, 0x00, 0x32, 0x22]
+    }
+
+    fn sample_args(
+        state: EscrowState,
+        deposits: Vec<EscrowDeposit>,
+        contributor: [u8; PKH_LEN],
+    ) -> EscrowDepositArgs {
+        let escrow_in = EscrowUtxoIn {
+            tx_hash_hex: "11".repeat(32),
+            output_index: 0,
+            lovelace: 5_000_000,
+            assets: vec![],
+            datum: EscrowDatum {
+                party_a: pkh(0xa1),
+                party_b: pkh(0xb2),
+                recipient: pkh(0xb2),
+                open_deadline_ms: 1_700_000_000_000,
+                lock_period_ms: 30 * 60 * 1000,
+                state,
+                deposits,
+            },
+        };
+        EscrowDepositArgs {
+            cfg: sample_cfg(),
+            escrow_script_address:
+                "addr_test1wqlzsnytzs4qv0trmhvw5cuyxnxk0qjq68crn85jj4lhv7qn4wym4".into(),
+            validator_script_cbor: stub_v3_script(),
+            escrow_in,
+            contributor_pkh: contributor,
+            add_lovelace: 5_000_000,
+            change_address:
+                "addr_test1qqqt0pru382hy9vjlsxv3ye02z50sfvt8xunscg5pgden77z73dpdfng2ctw2ekqplqgrljelz7h4dneac27nn3qx3rqqpavzj"
+                    .into(),
+            wallet_utxos: vec![
+                WalletUtxo {
+                    tx_hash_hex: "22".repeat(32),
+                    output_index: 0,
+                    lovelace: 20_000_000,
+                    assets: vec![],
+                },
+                WalletUtxo {
+                    tx_hash_hex: "33".repeat(32),
+                    output_index: 0,
+                    lovelace: 8_000_000,
+                    assets: vec![],
+                },
+            ],
+            tip_slot: 50_000_000,
+            validity_upper_slot: 50_001_800,
+            fee_lovelace: 2_500_000,
+            ex_units: ESCROW_SPEND_EX_UNITS,
+        }
+    }
+
+    #[test]
+    fn rejects_non_open_state() {
+        let args = sample_args(
+            EscrowState::Agreed { agreed_at_ms: 0 },
+            vec![],
+            pkh(0xa1),
+        );
+        let err = build_unsigned_escrow_deposit(args).unwrap_err();
+        assert!(err.to_string().contains("must be Open"));
+    }
+
+    #[test]
+    fn rejects_outsider_contributor() {
+        let args = sample_args(EscrowState::Open, vec![], pkh(0xff));
+        let err = build_unsigned_escrow_deposit(args).unwrap_err();
+        assert!(err.to_string().contains("party_a nor party_b"));
+    }
+
+    #[test]
+    fn rejects_zero_add_lovelace() {
+        let mut args = sample_args(EscrowState::Open, vec![], pkh(0xa1));
+        args.add_lovelace = 0;
+        let err = build_unsigned_escrow_deposit(args).unwrap_err();
+        assert!(err.to_string().contains("add_lovelace"));
+    }
+
+    #[test]
+    fn rejects_when_no_collateral_utxo() {
+        let mut args = sample_args(EscrowState::Open, vec![], pkh(0xa1));
+        args.wallet_utxos = vec![WalletUtxo {
+            tx_hash_hex: "44".repeat(32),
+            output_index: 0,
+            lovelace: 1_000_000, // way under collateral floor
+            assets: vec![],
+        }];
+        let err = build_unsigned_escrow_deposit(args).unwrap_err();
+        assert!(err.to_string().contains("collateral"));
+    }
+
+    #[test]
+    fn rejects_when_only_one_ada_utxo() {
+        let mut args = sample_args(EscrowState::Open, vec![], pkh(0xa1));
+        args.wallet_utxos = vec![WalletUtxo {
+            tx_hash_hex: "55".repeat(32),
+            output_index: 0,
+            lovelace: 50_000_000, // qualifies for collateral but no funding
+            assets: vec![],
+        }];
+        let err = build_unsigned_escrow_deposit(args).unwrap_err();
+        assert!(err.to_string().contains("SECOND ada-only"));
+    }
+
+    #[test]
+    fn first_deposit_appends_new_entry() {
+        // Empty deposits → new entry created.
+        let args = sample_args(EscrowState::Open, vec![], pkh(0xa1));
+        let unsigned = build_unsigned_escrow_deposit(args).unwrap();
+        assert!(unsigned.summary.contains("contributor="));
+        assert_eq!(unsigned.new_escrow_lovelace, 10_000_000);
+    }
+
+    #[test]
+    fn second_deposit_merges_into_existing_entry() {
+        // Existing deposit by party_a — second deposit must merge in place.
+        let existing = vec![EscrowDeposit {
+            contributor: pkh(0xa1),
+            value: EscrowValue::ada(3_000_000),
+        }];
+        let args = sample_args(EscrowState::Open, existing, pkh(0xa1));
+        let unsigned = build_unsigned_escrow_deposit(args).unwrap();
+        // Decode new datum and check
+        let pd: pallas_primitives::PlutusData =
+            minicbor::decode(&hex::decode(&unsigned.new_datum_cbor_hex).unwrap()).unwrap();
+        let new_datum = EscrowDatum::from_plutus_data(&pd).unwrap();
+        assert_eq!(new_datum.deposits.len(), 1);
+        // 3 ADA existing + 5 ADA added = 8 ADA
+        assert_eq!(
+            new_datum.deposits[0].value.lovelace(),
+            8_000_000,
+            "value_merge should sum lovelace in place"
+        );
+        assert_eq!(new_datum.deposits[0].contributor, pkh(0xa1));
+    }
+
+    #[test]
+    fn second_party_deposit_appends_new_entry() {
+        // party_a already deposited; party_b deposits next.
+        let existing = vec![EscrowDeposit {
+            contributor: pkh(0xa1),
+            value: EscrowValue::ada(5_000_000),
+        }];
+        let args = sample_args(EscrowState::Open, existing, pkh(0xb2));
+        let unsigned = build_unsigned_escrow_deposit(args).unwrap();
+        let pd: pallas_primitives::PlutusData =
+            minicbor::decode(&hex::decode(&unsigned.new_datum_cbor_hex).unwrap()).unwrap();
+        let new_datum = EscrowDatum::from_plutus_data(&pd).unwrap();
+        assert_eq!(new_datum.deposits.len(), 2);
+        assert_eq!(new_datum.deposits[0].contributor, pkh(0xa1));
+        assert_eq!(new_datum.deposits[0].value.lovelace(), 5_000_000);
+        assert_eq!(new_datum.deposits[1].contributor, pkh(0xb2));
+        assert_eq!(new_datum.deposits[1].value.lovelace(), 5_000_000);
+    }
+
+    #[test]
+    fn datum_immutable_fields_preserved() {
+        // Ensure party_a/b/recipient/deadline/lock_period are bit-exact
+        // on the new datum. Validator's "datum equal except deposits"
+        // check fails otherwise.
+        let args = sample_args(EscrowState::Open, vec![], pkh(0xa1));
+        let original = args.escrow_in.datum.clone();
+        let unsigned = build_unsigned_escrow_deposit(args).unwrap();
+        let pd: pallas_primitives::PlutusData =
+            minicbor::decode(&hex::decode(&unsigned.new_datum_cbor_hex).unwrap()).unwrap();
+        let new_datum = EscrowDatum::from_plutus_data(&pd).unwrap();
+        assert_eq!(new_datum.party_a, original.party_a);
+        assert_eq!(new_datum.party_b, original.party_b);
+        assert_eq!(new_datum.recipient, original.recipient);
+        assert_eq!(new_datum.open_deadline_ms, original.open_deadline_ms);
+        assert_eq!(new_datum.lock_period_ms, original.lock_period_ms);
+        assert_eq!(new_datum.state, EscrowState::Open);
+    }
+}

crates/aldabra-dao/src/builder/mod.rs

@@ -24,5 +24,7 @@ pub mod proposal_retract_votes;
 pub mod proposal_vote;
 pub mod stake_destroy;
 
+#[cfg(feature = "escrow_wip")]
+pub mod escrow_deposit;
 #[cfg(feature = "escrow_wip")]
 pub mod escrow_open;