diff --git a/crates/aldabra-dao/src/builder/proposal_vote.rs b/crates/aldabra-dao/src/builder/proposal_vote.rs
index 739e1c9..497ab2a 100644
--- a/crates/aldabra-dao/src/builder/proposal_vote.rs
+++ b/crates/aldabra-dao/src/builder/proposal_vote.rs
@@ -110,15 +110,23 @@ pub struct ProposalVoteArgs {
     pub change_address: String,
     /// Spendable wallet UTxOs.
     pub wallet_utxos: Vec<WalletUtxo>,
-    /// Current chain tip slot. Sets `valid_from_slot(tip_slot)` and
-    /// `invalid_from_slot(tip_slot + VALIDITY_RANGE_SLOTS)`.
+    /// Current chain tip slot. Sets `valid_from_slot(tip_slot)`.
     pub tip_slot: u64,
-    /// POSIX-ms equivalent of the validity range's UPPER bound (i.e. the
-    /// slot `tip_slot + VALIDITY_RANGE_SLOTS` converted to ms via the
-    /// Shelley genesis epoch). Embedded as `Voted.posix_time` on the new
-    /// stake lock — must match what the validator extracts from
-    /// `PFullyBoundedTimeRange _ upperBound`. Caller is responsible for
-    /// the slot↔ms conversion.
+    /// Tx upper-bound slot. Sets `invalid_from_slot(validity_upper_slot)`.
+    /// Caller may clamp this to (e.g.) the proposal's voting_end_slot to
+    /// keep the validity range inside the voting window. MUST be consistent
+    /// with `validity_upper_ms` — both should encode the SAME slot via the
+    /// network's slot↔ms conversion. The chain's V2 ScriptContext computes
+    /// `txInfo.validRange.upperBound` from this slot, and the validator's
+    /// `ppermitVote` synthesizes the expected `Voted.posix_time` from
+    /// THAT upper bound. If the slot underlying `validity_upper_ms` differs
+    /// from this slot, the validator's `passert "Correct outputs"` fails.
+    pub validity_upper_slot: u64,
+    /// POSIX-ms equivalent of `validity_upper_slot`. Embedded as
+    /// `Voted.posix_time` on the new stake lock — must match what the
+    /// validator extracts from `PFullyBoundedTimeRange _ upperBound`.
+    /// Caller is responsible for the slot↔ms conversion AND for ensuring
+    /// `slot_to_posix_ms(validity_upper_slot) == validity_upper_ms`.
     pub validity_upper_ms: i64,
     /// Reference UTxO citing the stake validator script.
     pub stake_validator_ref: ReferenceUtxo,
@@ -481,9 +489,13 @@ pub fn build_unsigned_proposal_vote(
     );
 
     // Validity range — must be inside voting window (already preflighted)
-    // AND its width must be ≤ votingTimeRangeMaxWidth.
+    // AND its width must be ≤ votingTimeRangeMaxWidth. The TTL uses
+    // `validity_upper_slot` (which the caller may have clamped) so the
+    // chain's reconstructed `txInfo.validRange.upperBound` matches the
+    // `validity_upper_ms` we embedded in the new `Voted` lock — otherwise
+    // `ppermitVote`'s `passert "Correct outputs"` would crash silently.
     staging = staging.valid_from_slot(args.tip_slot);
-    staging = staging.invalid_from_slot(args.tip_slot + VALIDITY_RANGE_SLOTS);
+    staging = staging.invalid_from_slot(args.validity_upper_slot);
 
     // Disclosed signer: voter pkh. The validator's `pisSignedBy` checks
     // this against `txInfoSignatories`.
@@ -644,6 +656,11 @@ mod tests {
                 },
             ],
             tip_slot: 180_062_536,
+            // Derive from validity_upper_ms via mainnet shelley_zero.
+            // shelley_zero = (4_492_800, 1_596_059_091_000).
+            // slot = 4_492_800 + (validity_upper_ms - 1_596_059_091_000) / 1000.
+            validity_upper_slot: 4_492_800
+                + ((validity_upper_ms - 1_596_059_091_000) / 1000) as u64,
             validity_upper_ms,
             stake_validator_ref: ReferenceUtxo {
                 tx_hash_hex: "479b8203c8b84ce20bb0a1c6ee1f527f122d1ce3e655dfc54635061eff622aea".into(),
diff --git a/crates/aldabra-mcp/src/tools.rs b/crates/aldabra-mcp/src/tools.rs
index 7e41ad3..11fdd8e 100644
--- a/crates/aldabra-mcp/src/tools.rs
+++ b/crates/aldabra-mcp/src/tools.rs
@@ -3274,6 +3274,7 @@ impl WalletService {
             change_address: self.inner.address.clone(),
             wallet_utxos,
             tip_slot,
+            validity_upper_slot,
             validity_upper_ms,
             stake_validator_ref,
             proposal_validator_ref,