diff --git a/milli/src/update/new/document_change.rs b/milli/src/update/new/document_change.rs
index bb1fc9441..4a61c110d 100644
--- a/milli/src/update/new/document_change.rs
+++ b/milli/src/update/new/document_change.rs
@@ -6,6 +6,7 @@ use super::vector_document::{
     MergedVectorDocument, VectorDocumentFromDb, VectorDocumentFromVersions,
 };
 use crate::documents::FieldIdMapper;
+use crate::vector::EmbeddingConfigs;
 use crate::{DocumentId, Index, Result};
 
 pub enum DocumentChange<'doc> {
@@ -94,8 +95,9 @@ impl<'doc> Insertion<'doc> {
     pub fn inserted_vectors(
         &self,
         doc_alloc: &'doc Bump,
+        embedders: &'doc EmbeddingConfigs,
     ) -> Result<Option<VectorDocumentFromVersions<'doc>>> {
-        VectorDocumentFromVersions::new(&self.new, doc_alloc)
+        VectorDocumentFromVersions::new(&self.new, doc_alloc, embedders)
     }
 }
 
@@ -165,8 +167,9 @@ impl<'doc> Update<'doc> {
     pub fn updated_vectors(
         &self,
         doc_alloc: &'doc Bump,
+        embedders: &'doc EmbeddingConfigs,
     ) -> Result<Option<VectorDocumentFromVersions<'doc>>> {
-        VectorDocumentFromVersions::new(&self.new, doc_alloc)
+        VectorDocumentFromVersions::new(&self.new, doc_alloc, embedders)
     }
 
     pub fn merged_vectors<Mapper: FieldIdMapper>(
@@ -175,11 +178,14 @@ impl<'doc> Update<'doc> {
         index: &'doc Index,
         mapper: &'doc Mapper,
         doc_alloc: &'doc Bump,
+        embedders: &'doc EmbeddingConfigs,
     ) -> Result<Option<MergedVectorDocument<'doc>>> {
         if self.has_deletion {
-            MergedVectorDocument::without_db(&self.new, doc_alloc)
+            MergedVectorDocument::without_db(&self.new, doc_alloc, embedders)
         } else {
-            MergedVectorDocument::with_db(self.docid, index, rtxn, mapper, &self.new, doc_alloc)
+            MergedVectorDocument::with_db(
+                self.docid, index, rtxn, mapper, &self.new, doc_alloc, embedders,
+            )
         }
     }
 }
diff --git a/milli/src/update/new/extract/vectors/mod.rs b/milli/src/update/new/extract/vectors/mod.rs
index 92c355710..70bd4d42d 100644
--- a/milli/src/update/new/extract/vectors/mod.rs
+++ b/milli/src/update/new/extract/vectors/mod.rs
@@ -93,7 +93,7 @@ impl<'a, 'extractor> Extractor<'extractor> for EmbeddingExtractor<'a> {
                         context.db_fields_ids_map,
                         &context.doc_alloc,
                     )?;
-                    let new_vectors = update.updated_vectors(&context.doc_alloc)?;
+                    let new_vectors = update.updated_vectors(&context.doc_alloc, self.embedders)?;
 
                     if let Some(new_vectors) = &new_vectors {
                         unused_vectors_distribution.append(new_vectors);
@@ -118,7 +118,12 @@ impl<'a, 'extractor> Extractor<'extractor> for EmbeddingExtractor<'a> {
                             if let Some(embeddings) = new_vectors.embeddings {
                                 chunks.set_vectors(
                                     update.docid(),
-                                    embeddings.into_vec().map_err(UserError::SerdeJson)?,
+                                    embeddings
+                                        .into_vec(&context.doc_alloc, embedder_name)
+                                        .map_err(|error| UserError::InvalidVectorsEmbedderConf {
+                                            document_id: update.external_document_id().to_string(),
+                                            error,
+                                        })?,
                                 );
                             } else if new_vectors.regenerate {
                                 let new_rendered = prompt.render_document(
@@ -177,7 +182,8 @@ impl<'a, 'extractor> Extractor<'extractor> for EmbeddingExtractor<'a> {
                     }
                 }
                 DocumentChange::Insertion(insertion) => {
-                    let new_vectors = insertion.inserted_vectors(&context.doc_alloc)?;
+                    let new_vectors =
+                        insertion.inserted_vectors(&context.doc_alloc, self.embedders)?;
                     if let Some(new_vectors) = &new_vectors {
                         unused_vectors_distribution.append(new_vectors);
                     }
@@ -194,7 +200,14 @@ impl<'a, 'extractor> Extractor<'extractor> for EmbeddingExtractor<'a> {
                             if let Some(embeddings) = new_vectors.embeddings {
                                 chunks.set_vectors(
                                     insertion.docid(),
-                                    embeddings.into_vec().map_err(UserError::SerdeJson)?,
+                                    embeddings
+                                        .into_vec(&context.doc_alloc, embedder_name)
+                                        .map_err(|error| UserError::InvalidVectorsEmbedderConf {
+                                            document_id: insertion
+                                                .external_document_id()
+                                                .to_string(),
+                                            error,
+                                        })?,
                                 );
                             } else if new_vectors.regenerate {
                                 let rendered = prompt.render_document(
diff --git a/milli/src/update/new/indexer/de.rs b/milli/src/update/new/indexer/de.rs
index 3da4fc239..94ab4c2c1 100644
--- a/milli/src/update/new/indexer/de.rs
+++ b/milli/src/update/new/indexer/de.rs
@@ -326,3 +326,294 @@ pub fn match_component<'de, 'indexer: 'de>(
     }
     ControlFlow::Continue(())
 }
+
+pub struct DeserrRawValue<'a> {
+    value: &'a RawValue,
+    alloc: &'a Bump,
+}
+
+impl<'a> DeserrRawValue<'a> {
+    pub fn new_in(value: &'a RawValue, alloc: &'a Bump) -> Self {
+        Self { value, alloc }
+    }
+}
+
+pub struct DeserrRawVec<'a> {
+    vec: raw_collections::RawVec<'a>,
+    alloc: &'a Bump,
+}
+
+impl<'a> deserr::Sequence for DeserrRawVec<'a> {
+    type Value = DeserrRawValue<'a>;
+
+    type Iter = DeserrRawVecIter<'a>;
+
+    fn len(&self) -> usize {
+        self.vec.len()
+    }
+
+    fn into_iter(self) -> Self::Iter {
+        DeserrRawVecIter { it: self.vec.into_iter(), alloc: self.alloc }
+    }
+}
+
+pub struct DeserrRawVecIter<'a> {
+    it: raw_collections::vec::iter::IntoIter<'a>,
+    alloc: &'a Bump,
+}
+
+impl<'a> Iterator for DeserrRawVecIter<'a> {
+    type Item = DeserrRawValue<'a>;
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let next = self.it.next()?;
+        Some(DeserrRawValue { value: next, alloc: self.alloc })
+    }
+}
+
+pub struct DeserrRawMap<'a> {
+    map: raw_collections::RawMap<'a>,
+    alloc: &'a Bump,
+}
+
+impl<'a> deserr::Map for DeserrRawMap<'a> {
+    type Value = DeserrRawValue<'a>;
+
+    type Iter = DeserrRawMapIter<'a>;
+
+    fn len(&self) -> usize {
+        self.map.len()
+    }
+
+    fn remove(&mut self, _key: &str) -> Option<Self::Value> {
+        unimplemented!()
+    }
+
+    fn into_iter(self) -> Self::Iter {
+        DeserrRawMapIter { it: self.map.into_iter(), alloc: self.alloc }
+    }
+}
+
+pub struct DeserrRawMapIter<'a> {
+    it: raw_collections::map::iter::IntoIter<'a>,
+    alloc: &'a Bump,
+}
+
+impl<'a> Iterator for DeserrRawMapIter<'a> {
+    type Item = (String, DeserrRawValue<'a>);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let (name, value) = self.it.next()?;
+        Some((name.to_string(), DeserrRawValue { value, alloc: self.alloc }))
+    }
+}
+
+impl<'a> deserr::IntoValue for DeserrRawValue<'a> {
+    type Sequence = DeserrRawVec<'a>;
+
+    type Map = DeserrRawMap<'a>;
+
+    fn kind(&self) -> deserr::ValueKind {
+        self.value.deserialize_any(DeserrKindVisitor).unwrap()
+    }
+
+    fn into_value(self) -> deserr::Value<Self> {
+        self.value.deserialize_any(DeserrRawValueVisitor { alloc: self.alloc }).unwrap()
+    }
+}
+
+pub struct DeserrKindVisitor;
+
+impl<'de> Visitor<'de> for DeserrKindVisitor {
+    type Value = deserr::ValueKind;
+
+    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(formatter, "any value")
+    }
+
+    fn visit_bool<E>(self, _v: bool) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::ValueKind::Boolean)
+    }
+
+    fn visit_i64<E>(self, _v: i64) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::ValueKind::NegativeInteger)
+    }
+
+    fn visit_u64<E>(self, _v: u64) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::ValueKind::Integer)
+    }
+
+    fn visit_f64<E>(self, _v: f64) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::ValueKind::Float)
+    }
+
+    fn visit_str<E>(self, _v: &str) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::ValueKind::String)
+    }
+
+    fn visit_none<E>(self) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::ValueKind::Null)
+    }
+
+    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        deserializer.deserialize_any(self)
+    }
+
+    fn visit_unit<E>(self) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::ValueKind::Null)
+    }
+
+    fn visit_newtype_struct<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        deserializer.deserialize_any(self)
+    }
+
+    fn visit_seq<A>(self, _seq: A) -> Result<Self::Value, A::Error>
+    where
+        A: serde::de::SeqAccess<'de>,
+    {
+        Ok(deserr::ValueKind::Sequence)
+    }
+
+    fn visit_map<A>(self, _map: A) -> Result<Self::Value, A::Error>
+    where
+        A: serde::de::MapAccess<'de>,
+    {
+        Ok(deserr::ValueKind::Map)
+    }
+}
+
+pub struct DeserrRawValueVisitor<'a> {
+    alloc: &'a Bump,
+}
+
+impl<'de> Visitor<'de> for DeserrRawValueVisitor<'de> {
+    type Value = deserr::Value<DeserrRawValue<'de>>;
+
+    fn expecting(&self, formatter: &mut std::fmt::Formatter) -> std::fmt::Result {
+        write!(formatter, "any value")
+    }
+
+    fn visit_bool<E>(self, v: bool) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::Value::Boolean(v))
+    }
+
+    fn visit_i64<E>(self, v: i64) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::Value::NegativeInteger(v))
+    }
+
+    fn visit_u64<E>(self, v: u64) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::Value::Integer(v))
+    }
+
+    fn visit_f64<E>(self, v: f64) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::Value::Float(v))
+    }
+
+    fn visit_str<E>(self, v: &str) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::Value::String(v.to_string()))
+    }
+
+    fn visit_string<E>(self, v: String) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::Value::String(v))
+    }
+
+    fn visit_none<E>(self) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::Value::Null)
+    }
+
+    fn visit_some<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        deserializer.deserialize_any(self)
+    }
+
+    fn visit_unit<E>(self) -> Result<Self::Value, E>
+    where
+        E: serde::de::Error,
+    {
+        Ok(deserr::Value::Null)
+    }
+
+    fn visit_newtype_struct<D>(self, deserializer: D) -> Result<Self::Value, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        deserializer.deserialize_any(self)
+    }
+
+    fn visit_seq<A>(self, mut seq: A) -> Result<Self::Value, A::Error>
+    where
+        A: serde::de::SeqAccess<'de>,
+    {
+        let mut raw_vec = raw_collections::RawVec::new_in(&self.alloc);
+        while let Some(next) = seq.next_element()? {
+            raw_vec.push(next);
+        }
+        Ok(deserr::Value::Sequence(DeserrRawVec { vec: raw_vec, alloc: self.alloc }))
+    }
+
+    fn visit_map<A>(self, map: A) -> Result<Self::Value, A::Error>
+    where
+        A: serde::de::MapAccess<'de>,
+    {
+        let _ = map;
+        Err(serde::de::Error::invalid_type(serde::de::Unexpected::Map, &self))
+    }
+
+    fn visit_enum<A>(self, data: A) -> Result<Self::Value, A::Error>
+    where
+        A: serde::de::EnumAccess<'de>,
+    {
+        let _ = data;
+        Err(serde::de::Error::invalid_type(serde::de::Unexpected::Enum, &self))
+    }
+}
diff --git a/milli/src/update/new/vector_document.rs b/milli/src/update/new/vector_document.rs
index a5519a025..6796134db 100644
--- a/milli/src/update/new/vector_document.rs
+++ b/milli/src/update/new/vector_document.rs
@@ -1,29 +1,67 @@
 use std::collections::BTreeSet;
 
 use bumpalo::Bump;
+use deserr::{Deserr, IntoValue};
 use heed::RoTxn;
 use raw_collections::RawMap;
 use serde::Serialize;
 use serde_json::value::RawValue;
 
 use super::document::{Document, DocumentFromDb, DocumentFromVersions, Versions};
+use super::indexer::de::DeserrRawValue;
 use crate::documents::FieldIdMapper;
 use crate::index::IndexEmbeddingConfig;
-use crate::vector::parsed_vectors::RawVectors;
-use crate::vector::Embedding;
+use crate::vector::parsed_vectors::{
+    RawVectors, VectorOrArrayOfVectors, RESERVED_VECTORS_FIELD_NAME,
+};
+use crate::vector::{Embedding, EmbeddingConfigs};
 use crate::{DocumentId, Index, InternalError, Result, UserError};
 
 #[derive(Serialize)]
 #[serde(untagged)]
 pub enum Embeddings<'doc> {
-    FromJson(&'doc RawValue),
+    FromJsonExplicit(&'doc RawValue),
+    FromJsonImplicityUserProvided(&'doc RawValue),
     FromDb(Vec<Embedding>),
 }
 impl<'doc> Embeddings<'doc> {
-    pub fn into_vec(self) -> std::result::Result<Vec<Embedding>, serde_json::Error> {
+    pub fn into_vec(
+        self,
+        doc_alloc: &'doc Bump,
+        embedder_name: &str,
+    ) -> std::result::Result<Vec<Embedding>, deserr::errors::JsonError> {
         match self {
-            /// FIXME: this should be a VecOrArrayOfVec
-            Embeddings::FromJson(value) => serde_json::from_str(value.get()),
+            Embeddings::FromJsonExplicit(value) => {
+                let vectors_ref = deserr::ValuePointerRef::Key {
+                    key: RESERVED_VECTORS_FIELD_NAME,
+                    prev: &deserr::ValuePointerRef::Origin,
+                };
+                let embedders_ref =
+                    deserr::ValuePointerRef::Key { key: embedder_name, prev: &vectors_ref };
+
+                let embeddings_ref =
+                    deserr::ValuePointerRef::Key { key: "embeddings", prev: &embedders_ref };
+
+                let v: VectorOrArrayOfVectors = VectorOrArrayOfVectors::deserialize_from_value(
+                    DeserrRawValue::new_in(value, doc_alloc).into_value(),
+                    embeddings_ref,
+                )?;
+                Ok(v.into_array_of_vectors().unwrap_or_default())
+            }
+            Embeddings::FromJsonImplicityUserProvided(value) => {
+                let vectors_ref = deserr::ValuePointerRef::Key {
+                    key: RESERVED_VECTORS_FIELD_NAME,
+                    prev: &deserr::ValuePointerRef::Origin,
+                };
+                let embedders_ref =
+                    deserr::ValuePointerRef::Key { key: embedder_name, prev: &vectors_ref };
+
+                let v: VectorOrArrayOfVectors = VectorOrArrayOfVectors::deserialize_from_value(
+                    DeserrRawValue::new_in(value, doc_alloc).into_value(),
+                    embedders_ref,
+                )?;
+                Ok(v.into_array_of_vectors().unwrap_or_default())
+            }
             Embeddings::FromDb(vec) => Ok(vec),
         }
     }
@@ -109,7 +147,7 @@ impl<'t> VectorDocument<'t> for VectorDocumentFromDb<'t> {
                 Ok((&*config_name, entry))
             })
             .chain(self.vectors_field.iter().flat_map(|map| map.iter()).map(|(name, value)| {
-                Ok((name, entry_from_raw_value(value).map_err(InternalError::SerdeJson)?))
+                Ok((name, entry_from_raw_value(value, false).map_err(InternalError::SerdeJson)?))
             }))
     }
 
@@ -122,7 +160,8 @@ impl<'t> VectorDocument<'t> for VectorDocumentFromDb<'t> {
             }
             None => match self.vectors_field.as_ref().and_then(|obkv| obkv.get(key)) {
                 Some(embedding_from_doc) => Some(
-                    entry_from_raw_value(embedding_from_doc).map_err(InternalError::SerdeJson)?,
+                    entry_from_raw_value(embedding_from_doc, false)
+                        .map_err(InternalError::SerdeJson)?,
                 ),
                 None => None,
             },
@@ -132,26 +171,40 @@ impl<'t> VectorDocument<'t> for VectorDocumentFromDb<'t> {
 
 fn entry_from_raw_value(
     value: &RawValue,
+    has_configured_embedder: bool,
 ) -> std::result::Result<VectorEntry<'_>, serde_json::Error> {
     let value: RawVectors = serde_json::from_str(value.get())?;
-    Ok(VectorEntry {
-        has_configured_embedder: false,
-        embeddings: value.embeddings().map(Embeddings::FromJson),
-        regenerate: value.must_regenerate(),
+
+    Ok(match value {
+        RawVectors::Explicit(raw_explicit_vectors) => VectorEntry {
+            has_configured_embedder,
+            embeddings: raw_explicit_vectors.embeddings.map(Embeddings::FromJsonExplicit),
+            regenerate: raw_explicit_vectors.regenerate,
+        },
+        RawVectors::ImplicitlyUserProvided(value) => VectorEntry {
+            has_configured_embedder,
+            embeddings: Some(Embeddings::FromJsonImplicityUserProvided(value)),
+            regenerate: false,
+        },
     })
 }
 
 pub struct VectorDocumentFromVersions<'doc> {
     vectors: RawMap<'doc>,
+    embedders: &'doc EmbeddingConfigs,
 }
 
 impl<'doc> VectorDocumentFromVersions<'doc> {
-    pub fn new(versions: &Versions<'doc>, bump: &'doc Bump) -> Result<Option<Self>> {
+    pub fn new(
+        versions: &Versions<'doc>,
+        bump: &'doc Bump,
+        embedders: &'doc EmbeddingConfigs,
+    ) -> Result<Option<Self>> {
         let document = DocumentFromVersions::new(versions);
         if let Some(vectors_field) = document.vectors_field()? {
             let vectors =
                 RawMap::from_raw_value(vectors_field, bump).map_err(UserError::SerdeJson)?;
-            Ok(Some(Self { vectors }))
+            Ok(Some(Self { vectors, embedders }))
         } else {
             Ok(None)
         }
@@ -161,14 +214,16 @@ impl<'doc> VectorDocumentFromVersions<'doc> {
 impl<'doc> VectorDocument<'doc> for VectorDocumentFromVersions<'doc> {
     fn iter_vectors(&self) -> impl Iterator<Item = Result<(&'doc str, VectorEntry<'doc>)>> {
         self.vectors.iter().map(|(embedder, vectors)| {
-            let vectors = entry_from_raw_value(vectors).map_err(UserError::SerdeJson)?;
+            let vectors = entry_from_raw_value(vectors, self.embedders.contains(embedder))
+                .map_err(UserError::SerdeJson)?;
             Ok((embedder, vectors))
         })
     }
 
     fn vectors_for_key(&self, key: &str) -> Result<Option<VectorEntry<'doc>>> {
         let Some(vectors) = self.vectors.get(key) else { return Ok(None) };
-        let vectors = entry_from_raw_value(vectors).map_err(UserError::SerdeJson)?;
+        let vectors = entry_from_raw_value(vectors, self.embedders.contains(key))
+            .map_err(UserError::SerdeJson)?;
         Ok(Some(vectors))
     }
 }
@@ -186,14 +241,19 @@ impl<'doc> MergedVectorDocument<'doc> {
         db_fields_ids_map: &'doc Mapper,
         versions: &Versions<'doc>,
         doc_alloc: &'doc Bump,
+        embedders: &'doc EmbeddingConfigs,
     ) -> Result<Option<Self>> {
         let db = VectorDocumentFromDb::new(docid, index, rtxn, db_fields_ids_map, doc_alloc)?;
-        let new_doc = VectorDocumentFromVersions::new(versions, doc_alloc)?;
+        let new_doc = VectorDocumentFromVersions::new(versions, doc_alloc, embedders)?;
         Ok(if db.is_none() && new_doc.is_none() { None } else { Some(Self { new_doc, db }) })
     }
 
-    pub fn without_db(versions: &Versions<'doc>, doc_alloc: &'doc Bump) -> Result<Option<Self>> {
-        let Some(new_doc) = VectorDocumentFromVersions::new(versions, doc_alloc)? else {
+    pub fn without_db(
+        versions: &Versions<'doc>,
+        doc_alloc: &'doc Bump,
+        embedders: &'doc EmbeddingConfigs,
+    ) -> Result<Option<Self>> {
+        let Some(new_doc) = VectorDocumentFromVersions::new(versions, doc_alloc, embedders)? else {
             return Ok(None);
         };
         Ok(Some(Self { new_doc: Some(new_doc), db: None }))
diff --git a/milli/src/vector/mod.rs b/milli/src/vector/mod.rs
index 2e9a498c0..a21e9e2ca 100644
--- a/milli/src/vector/mod.rs
+++ b/milli/src/vector/mod.rs
@@ -316,6 +316,10 @@ impl EmbeddingConfigs {
         Self(data)
     }
 
+    pub fn contains(&self, name: &str) -> bool {
+        self.0.contains_key(name)
+    }
+
     /// Get an embedder configuration and template from its name.
     pub fn get(&self, name: &str) -> Option<(Arc<Embedder>, Arc<Prompt>, bool)> {
         self.0.get(name).cloned()
diff --git a/milli/src/vector/parsed_vectors.rs b/milli/src/vector/parsed_vectors.rs
index 526516fef..40e823f17 100644
--- a/milli/src/vector/parsed_vectors.rs
+++ b/milli/src/vector/parsed_vectors.rs
@@ -84,7 +84,6 @@ impl<'doc> RawVectors<'doc> {
             RawVectors::Explicit(RawExplicitVectors { regenerate, .. }) => *regenerate,
         }
     }
-
     pub fn embeddings(&self) -> Option<&'doc RawValue> {
         match self {
             RawVectors::ImplicitlyUserProvided(embeddings) => Some(embeddings),