diff --git a/crates/client-api/src/routes/database.rs b/crates/client-api/src/routes/database.rs
index f871e1e9d5d..18128b79e17 100644
--- a/crates/client-api/src/routes/database.rs
+++ b/crates/client-api/src/routes/database.rs
@@ -223,19 +223,20 @@ fn assert_content_type_json(content_type: headers::ContentType) -> axum::respons
     }
 }
 
-fn reducer_outcome_response(owner_identity: &Identity, reducer: &str, outcome: ReducerOutcome) -> (StatusCode, String) {
+fn reducer_outcome_response(
+    owner_identity: &Identity,
+    reducer: &str,
+    outcome: ReducerOutcome,
+) -> (StatusCode, Box<str>) {
     match outcome {
-        ReducerOutcome::Committed => (StatusCode::OK, "".to_owned()),
+        ReducerOutcome::Committed => (StatusCode::OK, "".into()),
         ReducerOutcome::Failed(errmsg) => {
             // TODO: different status code? this is what cloudflare uses, sorta
-            (StatusCode::from_u16(530).unwrap(), errmsg)
+            (StatusCode::from_u16(530).unwrap(), *errmsg)
         }
         ReducerOutcome::BudgetExceeded => {
             log::warn!("Node's energy budget exceeded for identity: {owner_identity} while executing {reducer}");
-            (
-                StatusCode::PAYMENT_REQUIRED,
-                "Module energy budget exhausted.".to_owned(),
-            )
+            (StatusCode::PAYMENT_REQUIRED, "Module energy budget exhausted.".into())
         }
     }
 }
diff --git a/crates/core/src/host/host_controller.rs b/crates/core/src/host/host_controller.rs
index 46678071acf..bf7fe461a62 100644
--- a/crates/core/src/host/host_controller.rs
+++ b/crates/core/src/host/host_controller.rs
@@ -156,7 +156,7 @@ impl From<ReducerCallResult> for Result<(), anyhow::Error> {
 #[derive(Clone, Debug)]
 pub enum ReducerOutcome {
     Committed,
-    Failed(String),
+    Failed(Box<Box<str>>),
     BudgetExceeded,
 }
 
@@ -178,7 +178,7 @@ impl From<&EventStatus> for ReducerOutcome {
     fn from(status: &EventStatus) -> Self {
         match &status {
             EventStatus::Committed(_) => ReducerOutcome::Committed,
-            EventStatus::Failed(e) => ReducerOutcome::Failed(e.clone()),
+            EventStatus::Failed(e) => ReducerOutcome::Failed(Box::new((&**e).into())),
             EventStatus::OutOfEnergy => ReducerOutcome::BudgetExceeded,
         }
     }
diff --git a/crates/core/src/host/module_host.rs b/crates/core/src/host/module_host.rs
index 5d819caa2a3..012883b84d2 100644
--- a/crates/core/src/host/module_host.rs
+++ b/crates/core/src/host/module_host.rs
@@ -578,7 +578,7 @@ pub fn call_identity_connected(
 
             // If the reducer returned an error or couldn't run due to insufficient energy,
             // abort the connection: the module code has decided it doesn't want this client.
-            ReducerOutcome::Failed(message) => Err(ClientConnectedError::Rejected(message)),
+            ReducerOutcome::Failed(message) => Err(ClientConnectedError::Rejected(*message)),
             ReducerOutcome::BudgetExceeded => Err(ClientConnectedError::OutOfEnergy),
         }
     } else {
@@ -966,7 +966,7 @@ pub enum ClientConnectedError {
     #[error("Failed to insert `st_client` row for module without client_connected reducer: {0}")]
     DBError(#[from] Box<DBError>),
     #[error("Connection rejected by `client_connected` reducer: {0}")]
-    Rejected(String),
+    Rejected(Box<str>),
     #[error("Insufficient energy balance to run `client_connected` reducer")]
     OutOfEnergy,
 }
diff --git a/crates/core/src/host/v8/mod.rs b/crates/core/src/host/v8/mod.rs
index 730fd7a4e12..0abf9203163 100644
--- a/crates/core/src/host/v8/mod.rs
+++ b/crates/core/src/host/v8/mod.rs
@@ -43,6 +43,7 @@ use spacetimedb_datastore::locking_tx_datastore::FuncCallType;
 use spacetimedb_datastore::traits::Program;
 use spacetimedb_lib::{ConnectionId, Identity, RawModuleDef, Timestamp};
 use spacetimedb_schema::auto_migrate::MigrationPolicy;
+use spacetimedb_table::static_assert_size;
 use std::sync::{Arc, LazyLock};
 use std::time::Instant;
 use tokio::sync::oneshot;
@@ -368,11 +369,13 @@ impl JsInstance {
         self: Box<Self>,
         program: Program,
     ) -> (anyhow::Result<Option<ReducerCallResult>>, Box<Self>) {
-        self.send_recv(
-            JsWorkerReply::into_init_database,
-            JsWorkerRequest::InitDatabase(program),
-        )
-        .await
+        let (ret, inst) = self
+            .send_recv(
+                JsWorkerReply::into_init_database,
+                JsWorkerRequest::InitDatabase(program),
+            )
+            .await;
+        (*ret, inst)
     }
 
     pub async fn call_procedure(self: Box<Self>, params: CallProcedureParams) -> (CallProcedureReturn, Box<Self>) {
@@ -421,10 +424,12 @@ enum JsWorkerReply {
     CallIdentityConnected(Result<(), ClientConnectedError>),
     CallIdentityDisconnected(Result<(), ReducerCallError>),
     DisconnectClient(Result<(), ReducerCallError>),
-    InitDatabase(anyhow::Result<Option<ReducerCallResult>>),
+    InitDatabase(Box<anyhow::Result<Option<ReducerCallResult>>>),
     CallScheduledFunction(CallScheduledFunctionResult),
 }
 
+static_assert_size!(JsWorkerReply, 48);
+
 /// A request for the worker in [`spawn_instance_worker`].
 // We care about optimizing for `CallReducer` as it happens frequently,
 // so we don't want to box anything in it.
@@ -646,7 +651,7 @@ fn spawn_instance_worker(
                 JsWorkerRequest::InitDatabase(program) => {
                     let (res, trapped): (Result<Option<ReducerCallResult>, anyhow::Error>, bool) =
                         init_database(replica_ctx, &module_common.info().module_def, program, call_reducer);
-                    reply("init_database", InitDatabase(res), trapped);
+                    reply("init_database", InitDatabase(Box::new(res)), trapped);
                 }
                 JsWorkerRequest::CallScheduledFunction(params, rt) => {
                     let _guard = rt.enter();