diff --git a/rust/agents/relayer/src/relayer.rs b/rust/agents/relayer/src/relayer.rs
index 2f1a801cf..c8a3aa40e 100644
--- a/rust/agents/relayer/src/relayer.rs
+++ b/rust/agents/relayer/src/relayer.rs
@@ -2,7 +2,7 @@ use std::collections::{HashMap, HashSet};
 use std::sync::Arc;
 
 use async_trait::async_trait;
-use eyre::{Context, Result};
+use eyre::{ensure, Context, Result};
 use hyperlane_core::U256;
 use tokio::sync::{
     mpsc::{self, UnboundedReceiver, UnboundedSender},
@@ -67,10 +67,18 @@ impl BaseAgent for Relayer {
         let core = settings.build_hyperlane_core(metrics.clone());
         let db = DB::from_path(&settings.db)?;
 
+        let destination_chains = settings.destinationchainnames.split(',');
+
+        for destination_chain in destination_chains.clone() {
+            let Some(cfg) = settings.chains.get(destination_chain) else { continue };
+            ensure!(
+                cfg.signer.is_some(),
+                format!("Destination chain {destination_chain} does not have a configured signer")
+            )
+        }
+
         // Use defined remote chains + the origin chain
-        let chain_names: Vec<_> = settings
-            .destinationchainnames
-            .split(',')
+        let chain_names: Vec<_> = destination_chains
             .chain([settings.originchainname.as_str()])
             .collect();
 
diff --git a/rust/hyperlane-base/src/macros.rs b/rust/hyperlane-base/src/macros.rs
index f6f8a1bdf..decb6e111 100644
--- a/rust/hyperlane-base/src/macros.rs
+++ b/rust/hyperlane-base/src/macros.rs
@@ -44,6 +44,7 @@ macro_rules! decl_agent {
     };
 }
 
+use crate::Settings;
 /// Export this so they don't need to import paste.
 #[doc(hidden)]
 pub use paste;
@@ -103,6 +104,12 @@ macro_rules! decl_settings {
                 }
             }
 
+            impl AsMut<hyperlane_base::Settings> for [<$name Settings>] {
+                fn as_mut(&mut self) -> &mut hyperlane_base::Settings {
+                    &mut self.base
+                }
+            }
+
             impl hyperlane_base::NewFromSettings for [<$name Settings>] {
                 type Error = eyre::Report;
 
@@ -117,7 +124,10 @@ macro_rules! decl_settings {
 
 /// Static logic called by the decl_settings! macro. Do not call directly!
 #[doc(hidden)]
-pub fn _new_settings<'de, T: Deserialize<'de>>(name: &str) -> eyre::Result<T> {
+pub fn _new_settings<'de, T>(name: &str) -> eyre::Result<T>
+where
+    T: Deserialize<'de> + AsMut<Settings>,
+{
     use crate::settings::loader::load_settings_object;
 
     load_settings_object::<T, &str>(name, &[])
diff --git a/rust/hyperlane-base/src/settings/loader.rs b/rust/hyperlane-base/src/settings/loader.rs
index 849ea5498..877b5aaa0 100644
--- a/rust/hyperlane-base/src/settings/loader.rs
+++ b/rust/hyperlane-base/src/settings/loader.rs
@@ -3,16 +3,21 @@ use std::env;
 use std::error::Error;
 use std::path::PathBuf;
 
+use crate::Settings;
 use config::{Config, Environment, File};
 use eyre::{Context, Result};
 use serde::Deserialize;
 
 /// Load a settings object from the config locations.
 /// Further documentation can be found in the `settings` module.
-pub(crate) fn load_settings_object<'de, T: Deserialize<'de>, S: AsRef<str>>(
+pub(crate) fn load_settings_object<'de, T, S>(
     agent_prefix: &str,
     ignore_prefixes: &[S],
-) -> Result<T> {
+) -> Result<T>
+where
+    T: Deserialize<'de> + AsMut<Settings>,
+    S: AsRef<str>,
+{
     // Derive additional prefix from agent name
     let prefix = format!("HYP_{}", agent_prefix).to_ascii_uppercase();
 
@@ -81,8 +86,11 @@ pub(crate) fn load_settings_object<'de, T: Deserialize<'de>, S: AsRef<str>>(
         }
     };
 
-    match Config::try_deserialize(config_deserializer) {
-        Ok(cfg) => Ok(cfg),
+    match Config::try_deserialize::<T>(config_deserializer) {
+        Ok(mut cfg) => {
+            cfg.as_mut().post_deserialize();
+            Ok(cfg)
+        }
         Err(err) => {
             let err_str = err.to_string();
 
diff --git a/rust/hyperlane-base/src/settings/mod.rs b/rust/hyperlane-base/src/settings/mod.rs
index 07761a338..ce6410d6c 100644
--- a/rust/hyperlane-base/src/settings/mod.rs
+++ b/rust/hyperlane-base/src/settings/mod.rs
@@ -77,6 +77,7 @@ use rusoto_kms::KmsClient;
 use serde::Deserialize;
 
 pub use chains::{ChainConf, ChainSetup, CoreContractAddresses};
+use hyperlane_core::utils::StrOrInt;
 use hyperlane_core::{
     db::{HyperlaneDB, DB},
     HyperlaneChain, HyperlaneDomain, HyperlaneProvider, InterchainGasPaymaster,
@@ -128,10 +129,14 @@ static KMS_CLIENT: OnceCell<KmsClient> = OnceCell::new();
 pub struct Settings {
     /// Configuration for contracts on each chain
     pub chains: HashMap<String, ChainSetup>,
+    /// Default signer configuration for chains which do not define their own.
+    /// This value is intentionally private as it will get consumed by
+    /// `post_deserialize`.
+    defaultsigner: Option<SignerConf>,
     /// Gelato config
     pub gelato: Option<GelatoConf>,
     /// Port to listen for prometheus scrape requests
-    pub metrics: Option<String>,
+    pub metrics: Option<StrOrInt>,
     /// The tracing configuration
     pub tracing: TracingConfig,
 }
@@ -251,12 +256,20 @@ impl Settings {
             name,
             self.metrics
                 .as_ref()
-                .map(|v| v.parse::<u16>().context("Port must be a valid u16"))
+                .map(|v| v.try_into().context("Port must be a valid u16"))
                 .transpose()?,
             prometheus::Registry::new(),
         )?))
     }
 
+    /// Make internal connections as-needed after deserializing.
+    pub(super) fn post_deserialize(&mut self) {
+        let Some(signer) = self.defaultsigner.take() else { return };
+        for chain in self.chains.values_mut() {
+            chain.signer.get_or_insert_with(|| signer.clone());
+        }
+    }
+
     /// Private to preserve linearity of AgentCore::from_settings -- creating an
     /// agent consumes the settings.
     fn clone(&self) -> Self {
@@ -265,6 +278,7 @@ impl Settings {
             gelato: self.gelato.clone(),
             metrics: self.metrics.clone(),
             tracing: self.tracing.clone(),
+            defaultsigner: self.defaultsigner.clone(),
         }
     }
 }
diff --git a/rust/hyperlane-core/src/utils.rs b/rust/hyperlane-core/src/utils.rs
index f2d220b0c..03783b0e9 100644
--- a/rust/hyperlane-core/src/utils.rs
+++ b/rust/hyperlane-core/src/utils.rs
@@ -204,6 +204,7 @@ macro_rules! convert_to {
     };
 }
 
+convert_to!(u16);
 convert_to!(u32);
 convert_to!(u64);
 
diff --git a/rust/utils/run-locally/src/main.rs b/rust/utils/run-locally/src/main.rs
index 091eff1cf..c0dd72f0d 100644
--- a/rust/utils/run-locally/src/main.rs
+++ b/rust/utils/run-locally/src/main.rs
@@ -154,8 +154,9 @@ fn main() -> ExitCode {
         "HYP_BASE_CHAINS_TEST1_SIGNER_TYPE" => "hexKey",
         "HYP_BASE_CHAINS_TEST2_SIGNER_KEY" => "f214f2b2cd398c806f84e317254e0f0b801d0643303237d97a22a48e01628897",
         "HYP_BASE_CHAINS_TEST2_SIGNER_TYPE" => "hexKey",
-        "HYP_BASE_CHAINS_TEST3_SIGNER_KEY" => "701b615bbdfb9de65240bc28bd21bbc0d996645a3dd57e7b12bc2bdf6f192c82",
-        "HYP_BASE_CHAINS_TEST3_SIGNER_TYPE" => "hexKey",
+        // default is used for TEST3
+        "HYP_BASE_DEFAULTSIGNER_KEY" => "701b615bbdfb9de65240bc28bd21bbc0d996645a3dd57e7b12bc2bdf6f192c82",
+        "HYP_BASE_DEFAULTSIGNER_TYPE" => "hexKey",
         "HYP_RELAYER_GASPAYMENTENFORCEMENT" => r#"[{"type": "none"}]"#,
         "HYP_RELAYER_ORIGINCHAINNAME" => "test1",
         "HYP_RELAYER_DESTINATIONCHAINNAMES" => "test2,test3",