diff --git a/Cargo.lock b/Cargo.lock
index e172318e..fe6226ef 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -8211,6 +8211,7 @@ dependencies = [
  "anyhow",
  "arithmetic",
  "axum",
+ "axum-extra",
  "bls",
  "builder_api",
  "cached",
diff --git a/grandine-snapshot-tests b/grandine-snapshot-tests
index c09e1cfa..1ded5ee9 160000
--- a/grandine-snapshot-tests
+++ b/grandine-snapshot-tests
@@ -1 +1 @@
-Subproject commit c09e1cfa56a3c3cfc2502f8650a92db8f66a9e7d
+Subproject commit 1ded5ee9eed683ee965c190f44d5ed2ee660b93d
diff --git a/http_api/src/error.rs b/http_api/src/error.rs
index 90537f88..ba002e46 100644
--- a/http_api/src/error.rs
+++ b/http_api/src/error.rs
@@ -3,10 +3,12 @@ use std::error::Error as StdError;
 
 use anyhow::Error as AnyhowError;
 use axum::{
+    extract::rejection::JsonRejection,
     http::StatusCode,
     response::{IntoResponse, Response},
     Extension, Json,
 };
+use axum_extra::extract::QueryRejection;
 use bls::SignatureBytes;
 use futures::channel::oneshot::Canceled;
 use itertools::Itertools as _;
@@ -69,7 +71,7 @@ pub enum Error {
     #[error("invalid epoch")]
     InvalidEpoch(#[source] AnyhowError),
     #[error("invalid JSON body")]
-    InvalidJsonBody(#[source] AnyhowError),
+    InvalidJsonBody(#[source] JsonRejection),
     #[error("invalid peer ID")]
     InvalidPeerId(#[source] AnyhowError),
     #[error(
@@ -84,13 +86,13 @@ pub enum Error {
     #[error("invalid proposer slashing, it will never pass validation so it's rejected")]
     InvalidProposerSlashing(#[source] AnyhowError),
     #[error("invalid query string")]
-    InvalidQuery(#[source] AnyhowError),
+    InvalidQuery(#[source] QueryRejection),
     #[error("invalid voluntary exit, it will never pass validation so it's rejected")]
     InvalidSignedVoluntaryExit(#[source] AnyhowError),
     #[error("invalid sync committee messages")]
     InvalidSyncCommitteeMessages(Vec<IndexedError>),
-    #[error("invalid validator index")]
-    InvalidValidatorIndex(#[source] AnyhowError),
+    #[error("invalid validator indices")]
+    InvalidValidatorIndices(#[source] JsonRejection),
     #[error("invalid validator signatures")]
     InvalidValidatorSignatures(Vec<IndexedError>),
     #[error("invalid BLS to execution changes")]
@@ -160,16 +162,26 @@ impl Error {
 
     // `StdError::sources` is not stable as of Rust 1.78.0.
     fn sources(&self) -> impl Iterator<Item = &dyn StdError> {
-        let mut error: Option<&dyn StdError> = Some(self);
+        let first: &dyn StdError = self;
 
-        core::iter::from_fn(move || {
-            let source = error?.source();
-            core::mem::replace(&mut error, source)
-        })
+        let skip_duplicates = || match self {
+            Self::InvalidJsonBody(_) | Self::InvalidValidatorIndices(_) => first.source()?.source(),
+            Self::InvalidQuery(_) => first.source()?.source()?.source(),
+            _ => first.source(),
+        };
+
+        let mut next = skip_duplicates();
+
+        core::iter::once(first).chain(core::iter::from_fn(move || {
+            let source = next?.source();
+            core::mem::replace(&mut next, source)
+        }))
     }
 
-    const fn status_code(&self) -> StatusCode {
+    fn status_code(&self) -> StatusCode {
         match self {
+            Self::InvalidJsonBody(json_rejection)
+            | Self::InvalidValidatorIndices(json_rejection) => json_rejection.status(),
             Self::AttestationNotFound
             | Self::BlockNotFound
             | Self::MatchingAttestationHeadBlockNotFound
@@ -191,7 +203,6 @@ impl Error {
             | Self::InvalidBlockId(_)
             | Self::InvalidContributionAndProofs(_)
             | Self::InvalidEpoch(_)
-            | Self::InvalidJsonBody(_)
             | Self::InvalidQuery(_)
             | Self::InvalidPeerId(_)
             | Self::InvalidProposerSlashing(_)
@@ -201,7 +212,6 @@ impl Error {
             | Self::InvalidSyncCommitteeMessages(_)
             | Self::InvalidRandaoReveal
             | Self::InvalidValidatorId(_)
-            | Self::InvalidValidatorIndex(_)
             | Self::InvalidValidatorSignatures(_)
             | Self::ProposalSlotNotLaterThanStateSlot
             | Self::SlotNotInEpoch
@@ -266,6 +276,7 @@ struct EthErrorResponse<'error> {
 #[allow(clippy::needless_pass_by_value)]
 #[cfg(test)]
 mod tests {
+    use axum::{extract::rejection::MissingJsonContentType, Error as AxumError};
     use serde_json::{json, Result, Value};
     use test_case::test_case;
 
@@ -299,4 +310,34 @@ mod tests {
         assert_eq!(actual_json, expected_json);
         Ok(())
     }
+
+    // `axum::extract::rejection::JsonRejection` duplicates error sources.
+    // The underlying bug in `axum-core` was fixed in <https://github.com/tokio-rs/axum/pull/2030>.
+    // The fix was backported in <https://github.com/tokio-rs/axum/pull/2098> but not released.
+    #[test]
+    fn error_sources_does_not_yield_duplicates_from_json_rejection() {
+        let error = Error::InvalidJsonBody(JsonRejection::from(MissingJsonContentType::default()));
+
+        assert_eq!(
+            error.sources().map(ToString::to_string).collect_vec(),
+            [
+                "invalid JSON body",
+                "Expected request with `Content-Type: application/json`",
+            ],
+        );
+    }
+
+    // `axum_extra::extract::QueryRejection` and `axum::Error` duplicate error sources.
+    // `axum::Error` has not been fixed in any version yet.
+    // `axum::extract::rejection::QueryRejection` is even worse and harder to work around.
+    #[test]
+    fn error_sources_does_not_yield_triplicates_from_query_rejection() {
+        let axum_error = AxumError::new("error");
+        let error = Error::InvalidQuery(QueryRejection::FailedToDeserializeQueryString(axum_error));
+
+        assert_eq!(
+            error.sources().map(ToString::to_string).collect_vec(),
+            ["invalid query string", "error"],
+        );
+    }
 }
diff --git a/http_api/src/extractors.rs b/http_api/src/extractors.rs
index 6da3ec69..78a7db48 100644
--- a/http_api/src/extractors.rs
+++ b/http_api/src/extractors.rs
@@ -160,7 +160,6 @@ impl<S, T: DeserializeOwned + 'static> FromRequestParts<S> for EthQuery<T> {
             .extract()
             .await
             .map(|Query(query)| Self(query))
-            .map_err(AnyhowError::msg)
             .map_err(Error::InvalidQuery)
     }
 }
@@ -177,8 +176,7 @@ impl<S> FromRequest<S, Body> for EthJson<Box<ProposerSlashing>> {
             .extract()
             .await
             .map(|Json(slashing)| Self(slashing))
-            .map_err(AnyhowError::new)
-            .map_err(Error::InvalidProposerSlashing)
+            .map_err(Error::InvalidJsonBody)
     }
 }
 
@@ -191,8 +189,7 @@ impl<S> FromRequest<S, Body> for EthJson<Box<SignedVoluntaryExit>> {
             .extract()
             .await
             .map(|Json(slashing)| Self(slashing))
-            .map_err(AnyhowError::new)
-            .map_err(Error::InvalidSignedVoluntaryExit)
+            .map_err(Error::InvalidJsonBody)
     }
 }
 
@@ -205,8 +202,7 @@ impl<S, P: Preset> FromRequest<S, Body> for EthJson<Box<AttesterSlashing<P>>> {
             .extract()
             .await
             .map(|Json(slashing)| Self(slashing))
-            .map_err(AnyhowError::new)
-            .map_err(Error::InvalidAttesterSlashing)
+            .map_err(Error::InvalidJsonBody)
     }
 }
 
@@ -219,7 +215,6 @@ impl<S, P: Preset> FromRequest<S, Body> for EthJson<Vec<Arc<Attestation<P>>>> {
             .extract()
             .await
             .map(|Json(attestation)| Self(attestation))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -233,7 +228,6 @@ impl<S> FromRequest<S, Body> for EthJson<Vec<Value>> {
             .extract()
             .await
             .map(|Json(values)| Self(values))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -250,8 +244,7 @@ impl<S> FromRequest<S, Body> for EthJson<Vec<ValidatorIndex>> {
             .extract()
             .await
             .map(|Json(Wrapper(indices))| Self(indices))
-            .map_err(AnyhowError::new)
-            .map_err(Error::InvalidValidatorIndex)
+            .map_err(Error::InvalidValidatorIndices)
     }
 }
 
@@ -264,8 +257,7 @@ impl<S> FromRequest<S, Body> for EthJson<Vec<ValidatorId>> {
             .extract()
             .await
             .map(|Json(indices)| Self(indices))
-            .map_err(AnyhowError::new)
-            .map_err(Error::InvalidValidatorId)
+            .map_err(Error::InvalidJsonBody)
     }
 }
 
@@ -278,7 +270,6 @@ impl<S> FromRequest<S, Body> for EthJson<Vec<SyncCommitteeSubscription>> {
             .extract()
             .await
             .map(|Json(subscription)| Self(subscription))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -292,7 +283,6 @@ impl<S> FromRequest<S, Body> for EthJson<Vec<BeaconCommitteeSubscription>> {
             .extract()
             .await
             .map(|Json(subscription)| Self(subscription))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -306,7 +296,6 @@ impl<S, P: Preset> FromRequest<S, Body> for EthJson<Vec<Arc<SignedAggregateAndPr
             .extract()
             .await
             .map(|Json(aggregate_and_proof)| Self(aggregate_and_proof))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -320,7 +309,6 @@ impl<S, P: Preset> FromRequest<S, Body> for EthJson<Vec<SignedContributionAndPro
             .extract()
             .await
             .map(|Json(contribution_and_proof)| Self(contribution_and_proof))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -334,7 +322,6 @@ impl<S> FromRequest<S, Body> for EthJson<Vec<ValidatorProposerData>> {
             .extract()
             .await
             .map(|Json(proposer_data)| Self(proposer_data))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -348,7 +335,6 @@ impl<S> FromRequest<S, Body> for EthJson<Vec<SignedValidatorRegistrationV1>> {
             .extract()
             .await
             .map(|Json(registrations)| Self(registrations))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
diff --git a/validator/Cargo.toml b/validator/Cargo.toml
index cd4ab32f..db713f5d 100644
--- a/validator/Cargo.toml
+++ b/validator/Cargo.toml
@@ -7,9 +7,10 @@ authors = ["Grandine <info@grandine.io>"]
 workspace = true
 
 [dependencies]
-axum = { workspace = true }
 anyhow = { workspace = true }
 arithmetic = { workspace = true }
+axum = { workspace = true }
+axum-extra = { workspace = true }
 bls = { workspace = true }
 builder_api = { workspace = true }
 cached = { workspace = true }
diff --git a/validator/src/api.rs b/validator/src/api.rs
index abcc7aed..11e9dd29 100644
--- a/validator/src/api.rs
+++ b/validator/src/api.rs
@@ -13,7 +13,10 @@ use anyhow::{ensure, Error as AnyhowError, Result};
 use axum::{
     async_trait,
     body::Body,
-    extract::{FromRef, FromRequest, FromRequestParts, Path as RequestPath, Query, State},
+    extract::{
+        rejection::JsonRejection, FromRef, FromRequest, FromRequestParts, Path as RequestPath,
+        State,
+    },
     headers::{authorization::Bearer, Authorization},
     http::{request::Parts, Request, StatusCode},
     middleware::Next,
@@ -21,6 +24,7 @@ use axum::{
     routing::{delete, get, post},
     Json, RequestExt as _, RequestPartsExt as _, Router, Server, TypedHeader,
 };
+use axum_extra::extract::{Query, QueryRejection};
 use bls::PublicKeyBytes;
 use constant_time_eq::constant_time_eq;
 use directories::Directories;
@@ -86,11 +90,11 @@ enum Error {
     #[error("internal error")]
     Internal(#[from] AnyhowError),
     #[error("invalid JSON body")]
-    InvalidJsonBody(#[source] AnyhowError),
+    InvalidJsonBody(#[source] JsonRejection),
     #[error("invalid public key")]
     InvalidPublicKey(#[source] AnyhowError),
     #[error("invalid query string")]
-    InvalidQuery(#[source] AnyhowError),
+    InvalidQuery(#[source] QueryRejection),
     #[error("authentication error")]
     Unauthorized,
     #[error("validator {pubkey:?} not found")]
@@ -115,11 +119,10 @@ impl Error {
         ErrorResponse { message: self }
     }
 
-    const fn status_code(&self) -> StatusCode {
+    fn status_code(&self) -> StatusCode {
         match self {
-            Self::InvalidJsonBody(_) | Self::InvalidPublicKey(_) | Self::InvalidQuery(_) => {
-                StatusCode::BAD_REQUEST
-            }
+            Self::InvalidJsonBody(json_rejection) => json_rejection.status(),
+            Self::InvalidPublicKey(_) | Self::InvalidQuery(_) => StatusCode::BAD_REQUEST,
             Self::ValidatorNotFound { pubkey: _ } | Self::ValidatorNotOwned { pubkey: _ } => {
                 StatusCode::NOT_FOUND
             }
@@ -139,12 +142,20 @@ impl Error {
 
     // `StdError::sources` is not stable as of Rust 1.78.0.
     fn sources(&self) -> impl Iterator<Item = &dyn StdError> {
-        let mut error: Option<&dyn StdError> = Some(self);
+        let first: &dyn StdError = self;
 
-        core::iter::from_fn(move || {
-            let source = error?.source();
-            core::mem::replace(&mut error, source)
-        })
+        let skip_duplicates = || match self {
+            Self::InvalidJsonBody(_) => first.source()?.source(),
+            Self::InvalidQuery(_) => first.source()?.source()?.source(),
+            _ => first.source(),
+        };
+
+        let mut next = skip_duplicates();
+
+        core::iter::once(first).chain(core::iter::from_fn(move || {
+            let source = next?.source();
+            core::mem::replace(&mut next, source)
+        }))
     }
 }
 
@@ -214,7 +225,6 @@ impl<S> FromRequest<S, Body> for EthJson<SetFeeRecipientQuery> {
             .extract()
             .await
             .map(|Json(query)| Self(query))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -228,7 +238,6 @@ impl<S> FromRequest<S, Body> for EthJson<SetGasLimitQuery> {
             .extract()
             .await
             .map(|Json(query)| Self(query))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -242,7 +251,6 @@ impl<S> FromRequest<S, Body> for EthJson<SetGraffitiQuery> {
             .extract()
             .await
             .map(|Json(query)| Self(query))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -256,7 +264,6 @@ impl<S> FromRequest<S, Body> for EthJson<KeystoreImportQuery> {
             .extract()
             .await
             .map(|Json(query)| Self(query))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -270,7 +277,6 @@ impl<S> FromRequest<S, Body> for EthJson<KeystoreDeleteQuery> {
             .extract()
             .await
             .map(|Json(query)| Self(query))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -284,7 +290,6 @@ impl<S> FromRequest<S, Body> for EthJson<RemoteKeysImportQuery> {
             .extract()
             .await
             .map(|Json(query)| Self(query))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -298,7 +303,6 @@ impl<S> FromRequest<S, Body> for EthJson<RemoteKeysDeleteQuery> {
             .extract()
             .await
             .map(|Json(query)| Self(query))
-            .map_err(AnyhowError::new)
             .map_err(Error::InvalidJsonBody)
     }
 }
@@ -333,7 +337,6 @@ impl<S, T: DeserializeOwned + 'static> FromRequestParts<S> for EthQuery<T> {
             .extract()
             .await
             .map(|Query(query)| Self(query))
-            .map_err(AnyhowError::msg)
             .map_err(Error::InvalidQuery)
     }
 }
@@ -878,6 +881,7 @@ impl ApiToken {
 #[cfg(test)]
 mod tests {
     use anyhow::Result as AnyhowResult;
+    use axum::{extract::rejection::MissingJsonContentType, Error as AxumError};
     use serde_json::{json, Result, Value};
     use tempfile::{Builder, NamedTempFile};
     use test_case::test_case;
@@ -953,6 +957,36 @@ mod tests {
         Ok(())
     }
 
+    // `axum::extract::rejection::JsonRejection` duplicates error sources.
+    // The underlying bug in `axum-core` was fixed in <https://github.com/tokio-rs/axum/pull/2030>.
+    // The fix was backported in <https://github.com/tokio-rs/axum/pull/2098> but not released.
+    #[test]
+    fn error_sources_does_not_yield_duplicates_from_json_rejection() {
+        let error = Error::InvalidJsonBody(JsonRejection::from(MissingJsonContentType::default()));
+
+        assert_eq!(
+            error.sources().map(ToString::to_string).collect_vec(),
+            [
+                "invalid JSON body",
+                "Expected request with `Content-Type: application/json`",
+            ],
+        );
+    }
+
+    // `axum_extra::extract::QueryRejection` and `axum::Error` duplicate error sources.
+    // `axum::Error` has not been fixed in any version yet.
+    // `axum::extract::rejection::QueryRejection` is even worse and harder to work around.
+    #[test]
+    fn error_sources_does_not_yield_triplicates_from_query_rejection() {
+        let axum_error = AxumError::new("error");
+        let error = Error::InvalidQuery(QueryRejection::FailedToDeserializeQueryString(axum_error));
+
+        assert_eq!(
+            error.sources().map(ToString::to_string).collect_vec(),
+            ["invalid query string", "error"],
+        );
+    }
+
     fn token_file() -> AnyhowResult<NamedTempFile> {
         Ok(Builder::new().tempfile()?)
     }