diff --git a/.github/workflows/tests.yml b/.github/workflows/tests.yml
index 33f2e852..ca0bd4f5 100644
--- a/.github/workflows/tests.yml
+++ b/.github/workflows/tests.yml
@@ -42,9 +42,10 @@ jobs:
             -p serai-processor-key-gen \
             -p serai-processor-frost-attempt-manager \
             -p serai-processor-primitives \
+            -p serai-processor-scanner \
+            -p serai-processor-scheduler-primitives \
             -p serai-processor-utxo-scheduler-primitives \
             -p serai-processor-transaction-chaining-scheduler \
-            -p serai-processor-scanner \
             -p serai-processor \
             -p tendermint-machine \
             -p tributary-chain \
diff --git a/Cargo.lock b/Cargo.lock
index 7512f35c..6e7ced07 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8679,6 +8679,16 @@ dependencies = [
  "tokio",
 ]
 
+[[package]]
+name = "serai-processor-scheduler-primitives"
+version = "0.1.0"
+dependencies = [
+ "borsh",
+ "group",
+ "parity-scale-codec",
+ "serai-db",
+]
+
 [[package]]
 name = "serai-processor-tests"
 version = "0.1.0"
@@ -8715,11 +8725,11 @@ dependencies = [
  "borsh",
  "group",
  "parity-scale-codec",
- "serai-coins-primitives",
  "serai-db",
  "serai-primitives",
  "serai-processor-primitives",
  "serai-processor-scanner",
+ "serai-processor-scheduler-primitives",
  "serai-processor-utxo-scheduler-primitives",
 ]
 
diff --git a/Cargo.toml b/Cargo.toml
index 17435713..b61cde68 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -74,9 +74,10 @@ members = [
   "processor/frost-attempt-manager",
 
   "processor/primitives",
+  "processor/scanner",
+  "processor/scheduler/primitives",
   "processor/scheduler/utxo/primitives",
   "processor/scheduler/utxo/transaction-chaining",
-  "processor/scanner",
   "processor",
 
   "coordinator/tributary/tendermint",
diff --git a/deny.toml b/deny.toml
index fb616244..2ca0ca50 100644
--- a/deny.toml
+++ b/deny.toml
@@ -49,9 +49,10 @@ exceptions = [
   { allow = ["AGPL-3.0"], name = "serai-processor-key-gen" },
   { allow = ["AGPL-3.0"], name = "serai-processor-frost-attempt-manager" },
 
-  { allow = ["AGPL-3.0"], name = "serai-processor-utxo-primitives" },
-  { allow = ["AGPL-3.0"], name = "serai-processor-transaction-chaining-scheduler" },
   { allow = ["AGPL-3.0"], name = "serai-processor-scanner" },
+  { allow = ["AGPL-3.0"], name = "serai-processor-scheduler-primitives" },
+  { allow = ["AGPL-3.0"], name = "serai-processor-utxo-scheduler-primitives" },
+  { allow = ["AGPL-3.0"], name = "serai-processor-transaction-chaining-scheduler" },
   { allow = ["AGPL-3.0"], name = "serai-processor" },
 
   { allow = ["AGPL-3.0"], name = "tributary-chain" },
diff --git a/processor/scanner/src/lib.rs b/processor/scanner/src/lib.rs
index 4d33d0d0..d894f819 100644
--- a/processor/scanner/src/lib.rs
+++ b/processor/scanner/src/lib.rs
@@ -241,8 +241,12 @@ pub trait Scheduler<S: ScannerFeed>: 'static + Send {
   ///
   /// When a key is activated, the existing multisig should retain its outputs and utility for a
   /// certain time period. With `flush_key`, all outputs should be directed towards fulfilling some
-  /// obligation or the `new_key`. Every output MUST be connected to an Eventuality. If a key no
-  /// longer has active Eventualities, it MUST be able to be retired.
+  /// obligation or the `new_key`. Every output held by the retiring key MUST be connected to an
+  /// Eventuality. If a key no longer has active Eventualities, it MUST be able to be retired
+  /// without losing any coins.
+  ///
+  /// If the retiring key has any unfulfilled payments associated with it, those MUST be made
+  /// the responsibility of the new key.
   fn flush_key(&mut self, txn: &mut impl DbTxn, retiring_key: KeyFor<S>, new_key: KeyFor<S>);
 
   /// Retire a key as it'll no longer be used.
diff --git a/processor/scheduler/primitives/Cargo.toml b/processor/scheduler/primitives/Cargo.toml
new file mode 100644
index 00000000..31d73853
--- /dev/null
+++ b/processor/scheduler/primitives/Cargo.toml
@@ -0,0 +1,25 @@
+[package]
+name = "serai-processor-scheduler-primitives"
+version = "0.1.0"
+description = "Primitives for schedulers for the Serai processor"
+license = "AGPL-3.0-only"
+repository = "https://github.com/serai-dex/serai/tree/develop/processor/scheduler/primitives"
+authors = ["Luke Parker <lukeparker5132@gmail.com>"]
+keywords = []
+edition = "2021"
+publish = false
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[lints]
+workspace = true
+
+[dependencies]
+group = { version = "0.13", default-features = false }
+
+scale = { package = "parity-scale-codec", version = "3", default-features = false, features = ["std"] }
+borsh = { version = "1", default-features = false, features = ["std", "derive", "de_strict_order"] }
+
+serai-db = { path = "../../../common/db" }
diff --git a/processor/scheduler/primitives/LICENSE b/processor/scheduler/primitives/LICENSE
new file mode 100644
index 00000000..e091b149
--- /dev/null
+++ b/processor/scheduler/primitives/LICENSE
@@ -0,0 +1,15 @@
+AGPL-3.0-only license
+
+Copyright (c) 2024 Luke Parker
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License Version 3 as
+published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.
diff --git a/processor/scheduler/primitives/README.md b/processor/scheduler/primitives/README.md
new file mode 100644
index 00000000..6e81249d
--- /dev/null
+++ b/processor/scheduler/primitives/README.md
@@ -0,0 +1,3 @@
+# Scheduler Primitives
+
+Primitives for schedulers.
diff --git a/processor/scheduler/primitives/src/lib.rs b/processor/scheduler/primitives/src/lib.rs
new file mode 100644
index 00000000..97a00c03
--- /dev/null
+++ b/processor/scheduler/primitives/src/lib.rs
@@ -0,0 +1,48 @@
+#![cfg_attr(docsrs, feature(doc_auto_cfg))]
+#![doc = include_str!("../README.md")]
+#![deny(missing_docs)]
+
+use core::marker::PhantomData;
+use std::io;
+
+use group::GroupEncoding;
+
+use serai_db::DbTxn;
+
+/// A signable transaction.
+pub trait SignableTransaction: 'static + Sized + Send + Sync {
+  /// Read a `SignableTransaction`.
+  fn read(reader: &mut impl io::Read) -> io::Result<Self>;
+  /// Write a `SignableTransaction`.
+  fn write(&self, writer: &mut impl io::Write) -> io::Result<()>;
+}
+
+mod db {
+  use serai_db::{Get, DbTxn, create_db, db_channel};
+
+  db_channel! {
+    SchedulerPrimitives {
+      TransactionsToSign: (key: &[u8]) -> Vec<u8>,
+    }
+  }
+}
+
+/// The transactions to sign, as scheduled by a Scheduler.
+pub struct TransactionsToSign<T>(PhantomData<T>);
+impl<T: SignableTransaction> TransactionsToSign<T> {
+  /// Send a transaction to sign.
+  pub fn send(txn: &mut impl DbTxn, key: &impl GroupEncoding, tx: &T) {
+    let mut buf = Vec::with_capacity(128);
+    tx.write(&mut buf).unwrap();
+    db::TransactionsToSign::send(txn, key.to_bytes().as_ref(), &buf);
+  }
+
+  /// Try to receive a transaction to sign.
+  pub fn try_recv(txn: &mut impl DbTxn, key: &impl GroupEncoding) -> Option<T> {
+    let tx = db::TransactionsToSign::try_recv(txn, key.to_bytes().as_ref())?;
+    let mut tx = tx.as_slice();
+    let res = T::read(&mut tx).unwrap();
+    assert!(tx.is_empty());
+    Some(res)
+  }
+}
diff --git a/processor/scheduler/utxo/transaction-chaining/Cargo.toml b/processor/scheduler/utxo/transaction-chaining/Cargo.toml
index d54d0f85..a6b12128 100644
--- a/processor/scheduler/utxo/transaction-chaining/Cargo.toml
+++ b/processor/scheduler/utxo/transaction-chaining/Cargo.toml
@@ -26,10 +26,10 @@ scale = { package = "parity-scale-codec", version = "3", default-features = fals
 borsh = { version = "1", default-features = false, features = ["std", "derive", "de_strict_order"] }
 
 serai-primitives = { path = "../../../../substrate/primitives", default-features = false, features = ["std"] }
-serai-coins-primitives = { path = "../../../../substrate/coins/primitives", default-features = false, features = ["std"] }
 
 serai-db = { path = "../../../../common/db" }
 
 primitives = { package = "serai-processor-primitives", path = "../../../primitives" }
-scheduler-primitives = { package = "serai-processor-utxo-scheduler-primitives", path = "../primitives" }
+scheduler-primitives = { package = "serai-processor-scheduler-primitives", path = "../../primitives" }
+utxo-scheduler-primitives = { package = "serai-processor-utxo-scheduler-primitives", path = "../primitives" }
 scanner = { package = "serai-processor-scanner", path = "../../../scanner" }
diff --git a/processor/scheduler/utxo/transaction-chaining/src/db.rs b/processor/scheduler/utxo/transaction-chaining/src/db.rs
index 20c574e9..f6de26d1 100644
--- a/processor/scheduler/utxo/transaction-chaining/src/db.rs
+++ b/processor/scheduler/utxo/transaction-chaining/src/db.rs
@@ -2,7 +2,7 @@ use core::marker::PhantomData;
 
 use group::GroupEncoding;
 
-use serai_primitives::Coin;
+use serai_primitives::{Coin, Amount};
 
 use serai_db::{Get, DbTxn, create_db};
 
@@ -11,12 +11,23 @@ use scanner::{ScannerFeed, KeyFor, OutputFor};
 
 create_db! {
   TransactionChainingScheduler {
+    OperatingCosts: (coin: Coin) -> Amount,
     SerializedOutputs: (key: &[u8], coin: Coin) -> Vec<u8>,
+    // We should be immediately able to schedule the fulfillment of payments, yet this may not be
+    // possible if we're in the middle of a multisig rotation (as our output set will be split)
+    SerializedQueuedPayments: (key: &[u8]) > Vec<u8>,
   }
 }
 
 pub(crate) struct Db<S: ScannerFeed>(PhantomData<S>);
 impl<S: ScannerFeed> Db<S> {
+  pub(crate) fn operating_costs(getter: &impl Get, coin: Coin) -> Amount {
+    OperatingCosts::get(getter, coin).unwrap_or(Amount(0))
+  }
+  pub(crate) fn set_operating_costs(txn: &mut impl DbTxn, coin: Coin, amount: Amount) {
+    OperatingCosts::set(txn, coin, &amount)
+  }
+
   pub(crate) fn outputs(
     getter: &impl Get,
     key: KeyFor<S>,
@@ -46,4 +57,17 @@ impl<S: ScannerFeed> Db<S> {
   pub(crate) fn del_outputs(txn: &mut impl DbTxn, key: KeyFor<S>, coin: Coin) {
     SerializedOutputs::del(txn, key.to_bytes().as_ref(), coin);
   }
+
+  pub(crate) fn queued_payments(
+    getter: &impl Get,
+    key: KeyFor<S>,
+  ) -> Option<Vec<Payment<S>>> {
+    todo!("TODO")
+  }
+  pub(crate) fn set_queued_payments(txn: &mut impl DbTxn, key: KeyFor<S>, queued: Vec<Payment<S>>) {
+    todo!("TODO")
+  }
+  pub(crate) fn del_outputs(txn: &mut impl DbTxn, key: KeyFor<S>) {
+    SerializedQueuedPayments::del(txn, key.to_bytes().as_ref());
+  }
 }
diff --git a/processor/scheduler/utxo/transaction-chaining/src/lib.rs b/processor/scheduler/utxo/transaction-chaining/src/lib.rs
index 63635696..8f21e9d6 100644
--- a/processor/scheduler/utxo/transaction-chaining/src/lib.rs
+++ b/processor/scheduler/utxo/transaction-chaining/src/lib.rs
@@ -5,6 +5,8 @@
 use core::marker::PhantomData;
 use std::collections::HashMap;
 
+use group::GroupEncoding;
+
 use serai_primitives::Coin;
 
 use serai_db::DbTxn;
@@ -15,6 +17,7 @@ use scanner::{
   Scheduler as SchedulerTrait,
 };
 use scheduler_primitives::*;
+use utxo_scheduler_primitives::*;
 
 mod db;
 use db::Db;
@@ -25,7 +28,7 @@ pub struct PlannedTransaction<S: ScannerFeed, T> {
   signable: T,
   /// The outputs we'll receive from this.
   effected_received_outputs: OutputFor<S>,
-  /// The Evtnuality to watch for.
+  /// The Eventuality to watch for.
   eventuality: EventualityFor<S>,
 }
 
@@ -60,13 +63,13 @@ impl<S: ScannerFeed, T, P: TransactionPlanner<S, PlannedTransaction = PlannedTra
 
 impl<
     S: ScannerFeed,
-    T: 'static + Send + Sync,
+    T: 'static + Send + Sync + SignableTransaction,
     P: TransactionPlanner<S, PlannedTransaction = PlannedTransaction<S, T>>,
   > SchedulerTrait<S> for Scheduler<S, T, P>
 {
   fn activate_key(&mut self, txn: &mut impl DbTxn, key: KeyFor<S>) {
     for coin in S::NETWORK.coins() {
-      Db::<S>::set_outputs(txn, key, *coin, &vec![]);
+      Db::<S>::set_outputs(txn, key, *coin, &[]);
     }
   }
 
@@ -98,22 +101,27 @@ impl<
     {
       let mut planned_txs = vec![];
       for forward in update.forwards() {
-        let forward_to_key = active_keys.last().unwrap();
-        assert_eq!(forward_to_key.1, LifetimeStage::Active);
+        let key = forward.key();
+
+        assert_eq!(active_keys.len(), 2);
+        assert_eq!(active_keys[0].1, LifetimeStage::Forwarding);
+        assert_eq!(active_keys[1].1, LifetimeStage::Active);
+        let forward_to_key = active_keys[1].0;
 
         let Some(plan) = P::plan_transaction_with_fee_amortization(
           // This uses 0 for the operating costs as we don't incur any here
           &mut 0,
           fee_rates[&forward.balance().coin],
           vec![forward.clone()],
-          vec![Payment::new(P::forwarding_address(forward_to_key.0), forward.balance(), None)],
+          vec![Payment::new(P::forwarding_address(forward_to_key), forward.balance(), None)],
           None,
         ) else {
           continue;
         };
-        planned_txs.push(plan);
+        planned_txs.push((key, plan));
       }
       for to_return in update.returns() {
+        let key = to_return.output().key();
         let out_instruction =
           Payment::new(to_return.address().clone(), to_return.output().balance(), None);
         let Some(plan) = P::plan_transaction_with_fee_amortization(
@@ -126,12 +134,24 @@ impl<
         ) else {
           continue;
         };
-        planned_txs.push(plan);
+        planned_txs.push((key, plan));
       }
 
-      // TODO: Send the transactions off for signing
-      // TODO: Return the eventualities
-      todo!("TODO")
+      let mut eventualities = HashMap::new();
+      for (key, planned_tx) in planned_txs {
+        // Send the transactions off for signing
+        TransactionsToSign::<T>::send(txn, &key, &planned_tx.signable);
+
+        // Insert the eventualities into the result
+        eventualities
+          .entry(key.to_bytes().as_ref().to_vec())
+          .or_insert(Vec::with_capacity(1))
+          .push(planned_tx.eventuality);
+      }
+
+      // TODO: Fulfill any payments we prior couldn't
+
+      eventualities
     }
   }