diff --git a/icechunk-python/python/icechunk/_icechunk_python.pyi b/icechunk-python/python/icechunk/_icechunk_python.pyi
index f713dee54..02975c6ff 100644
--- a/icechunk-python/python/icechunk/_icechunk_python.pyi
+++ b/icechunk-python/python/icechunk/_icechunk_python.pyi
@@ -964,10 +964,8 @@ class PyRepository:
     def save_config(self) -> None: ...
     def config(self) -> RepositoryConfig: ...
     def storage(self) -> Storage: ...
-    def set_default_commit_metadata(
-        self, metadata: dict[str, Any] | None = None
-    ) -> None: ...
-    def default_commit_metadata(self) -> dict[str, Any] | None: ...
+    def set_default_commit_metadata(self, metadata: dict[str, Any]) -> None: ...
+    def default_commit_metadata(self) -> dict[str, Any]: ...
     def async_ancestry(
         self,
         *,
diff --git a/icechunk-python/python/icechunk/repository.py b/icechunk-python/python/icechunk/repository.py
index 01e9e06d6..7cb95cb18 100644
--- a/icechunk-python/python/icechunk/repository.py
+++ b/icechunk-python/python/icechunk/repository.py
@@ -216,7 +216,7 @@ def storage(self) -> Storage:
         """
         return self._repository.storage()
 
-    def set_default_commit_metadata(self, metadata: dict[str, Any] | None = None) -> None:
+    def set_default_commit_metadata(self, metadata: dict[str, Any]) -> None:
         """
         Set the default commit metadata for the repository. This is useful for providing
         addition static system conexted metadata to all commits.
@@ -230,18 +230,18 @@ def set_default_commit_metadata(self, metadata: dict[str, Any] | None = None) ->
 
         Parameters
         ----------
-        metadata : dict[str, Any], optional
-            The default commit metadata.
+        metadata : dict[str, Any]
+            The default commit metadata. Pass an empty dict to clear the default metadata.
         """
         return self._repository.set_default_commit_metadata(metadata)
 
-    def default_commit_metadata(self) -> dict[str, Any] | None:
+    def default_commit_metadata(self) -> dict[str, Any]:
         """
         Get the current configured default commit metadata for the repository.
 
         Returns
         -------
-        dict[str, Any] | None
+        dict[str, Any]
             The default commit metadata.
         """
         return self._repository.default_commit_metadata()
diff --git a/icechunk-python/src/repository.rs b/icechunk-python/src/repository.rs
index d45547198..441962d2d 100644
--- a/icechunk-python/src/repository.rs
+++ b/icechunk-python/src/repository.rs
@@ -362,7 +362,7 @@ impl PyGCSummary {
 }
 
 #[pyclass]
-pub struct PyRepository(Arc<Repository>);
+pub struct PyRepository(Arc<RwLock<Repository>>);
 
 #[pymethods]
 /// Most functions in this class call `Runtime.block_on` so they need to `allow_threads` so other
@@ -390,7 +390,7 @@ impl PyRepository {
                     .map_err(PyIcechunkStoreError::RepositoryError)
                 })?;
 
-            Ok(Self(Arc::new(repository)))
+            Ok(Self(Arc::new(RwLock::new(repository))))
         })
     }
 
@@ -416,7 +416,7 @@ impl PyRepository {
                     .map_err(PyIcechunkStoreError::RepositoryError)
                 })?;
 
-            Ok(Self(Arc::new(repository)))
+            Ok(Self(Arc::new(RwLock::new(repository))))
         })
     }
 
@@ -444,7 +444,7 @@ impl PyRepository {
                     )
                 })?;
 
-            Ok(Self(Arc::new(repository)))
+            Ok(Self(Arc::new(RwLock::new(repository))))
         })
     }
 
@@ -474,14 +474,15 @@ impl PyRepository {
         virtual_chunk_credentials: Option<Option<HashMap<String, PyCredentials>>>,
     ) -> PyResult<Self> {
         py.allow_threads(move || {
-            Ok(Self(Arc::new(
+            Ok(Self(Arc::new(RwLock::new(
                 self.0
+                    .blocking_read()
                     .reopen(
                         config.map(|c| c.into()),
                         virtual_chunk_credentials.map(map_credentials),
                     )
                     .map_err(PyIcechunkStoreError::RepositoryError)?,
-            )))
+            ))))
         })
     }
 
@@ -495,15 +496,18 @@ impl PyRepository {
         py.allow_threads(move || {
             let repository = Repository::from_bytes(bytes)
                 .map_err(PyIcechunkStoreError::RepositoryError)?;
-            Ok(Self(Arc::new(repository)))
+            Ok(Self(Arc::new(RwLock::new(repository))))
         })
     }
 
     fn as_bytes(&self, py: Python<'_>) -> PyResult<Cow<[u8]>> {
         // This is a compute intensive task, we need to release the Gil
         py.allow_threads(move || {
-            let bytes =
-                self.0.as_bytes().map_err(PyIcechunkStoreError::RepositoryError)?;
+            let bytes = self
+                .0
+                .blocking_read()
+                .as_bytes()
+                .map_err(PyIcechunkStoreError::RepositoryError)?;
             Ok(Cow::Owned(bytes))
         })
     }
@@ -530,6 +534,8 @@ impl PyRepository {
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 let _etag = self
                     .0
+                    .read()
+                    .await
                     .save_config()
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -539,33 +545,32 @@ impl PyRepository {
     }
 
     pub fn config(&self) -> PyRepositoryConfig {
-        self.0.config().clone().into()
+        self.0.blocking_read().config().clone().into()
     }
 
     pub fn storage_settings(&self) -> PyStorageSettings {
-        self.0.storage_settings().clone().into()
+        self.0.blocking_read().storage_settings().clone().into()
     }
 
     pub fn storage(&self) -> PyStorage {
-        PyStorage(Arc::clone(self.0.storage()))
+        PyStorage(Arc::clone(self.0.blocking_read().storage()))
     }
 
-    #[pyo3(signature = (metadata))]
     pub fn set_default_commit_metadata(
         &self,
-        metadata: Option<PySnapshotProperties>,
-    ) -> PyResult<()> {
-        let metadata = metadata.map(|m| m.into());
-        pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
-            self.0.set_default_commit_metadata(metadata).await;
-            Ok(())
+        py: Python<'_>,
+        metadata: PySnapshotProperties,
+    ) {
+        py.allow_threads(move || {
+            let metadata = metadata.into();
+            self.0.blocking_write().set_default_commit_metadata(metadata);
         })
     }
 
-    pub fn default_commit_metadata(&self) -> PyResult<Option<PySnapshotProperties>> {
-        pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
-            let metadata = self.0.default_commit_metadata().await;
-            Ok(metadata.map(|m| m.into()))
+    pub fn default_commit_metadata(&self, py: Python<'_>) -> PySnapshotProperties {
+        py.allow_threads(move || {
+            let metadata = self.0.blocking_read().default_commit_metadata().clone();
+            metadata.into()
         })
     }
 
@@ -578,12 +583,20 @@ impl PyRepository {
         tag: Option<String>,
         snapshot_id: Option<String>,
     ) -> PyResult<PyAsyncGenerator> {
-        let repo = Arc::clone(&self.0);
         // This function calls block_on, so we need to allow other thread python to make progress
         py.allow_threads(move || {
             let version = args_to_version_info(branch, tag, snapshot_id, None)?;
             let ancestry = pyo3_async_runtimes::tokio::get_runtime()
-                .block_on(async move { repo.ancestry_arc(&version).await })
+                .block_on(async move {
+                    let (snapshot_id, asset_manager) = {
+                        let lock = self.0.read().await;
+                        (
+                            lock.resolve_version(&version).await?,
+                            Arc::clone(lock.asset_manager()),
+                        )
+                    };
+                    asset_manager.snapshot_ancestry(&snapshot_id).await
+                })
                 .map_err(PyIcechunkStoreError::RepositoryError)?
                 .map_err(PyIcechunkStoreError::RepositoryError);
 
@@ -615,6 +628,8 @@ impl PyRepository {
 
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 self.0
+                    .read()
+                    .await
                     .create_branch(branch_name, &snapshot_id)
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -629,6 +644,8 @@ impl PyRepository {
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 let branches = self
                     .0
+                    .read()
+                    .await
                     .list_branches()
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -643,6 +660,8 @@ impl PyRepository {
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 let tip = self
                     .0
+                    .read()
+                    .await
                     .lookup_branch(branch_name)
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -667,6 +686,8 @@ impl PyRepository {
 
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 self.0
+                    .read()
+                    .await
                     .reset_branch(branch_name, &snapshot_id)
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -680,6 +701,8 @@ impl PyRepository {
         py.allow_threads(move || {
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 self.0
+                    .read()
+                    .await
                     .delete_branch(branch)
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -693,6 +716,8 @@ impl PyRepository {
         py.allow_threads(move || {
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 self.0
+                    .read()
+                    .await
                     .delete_tag(tag)
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -717,6 +742,8 @@ impl PyRepository {
 
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 self.0
+                    .read()
+                    .await
                     .create_tag(tag_name, &snapshot_id)
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -731,6 +758,8 @@ impl PyRepository {
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 let tags = self
                     .0
+                    .read()
+                    .await
                     .list_tags()
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -745,6 +774,8 @@ impl PyRepository {
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 let tag = self
                     .0
+                    .read()
+                    .await
                     .lookup_tag(tag)
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
@@ -773,6 +804,8 @@ impl PyRepository {
             pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                 let diff = self
                     .0
+                    .read()
+                    .await
                     .diff(&from, &to)
                     .await
                     .map_err(PyIcechunkStoreError::SessionError)?;
@@ -796,6 +829,8 @@ impl PyRepository {
             let session =
                 pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                     self.0
+                        .read()
+                        .await
                         .readonly_session(&version)
                         .await
                         .map_err(PyIcechunkStoreError::RepositoryError)
@@ -811,6 +846,8 @@ impl PyRepository {
             let session =
                 pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
                     self.0
+                        .read()
+                        .await
                         .writable_session(branch)
                         .await
                         .map_err(PyIcechunkStoreError::RepositoryError)
@@ -832,10 +869,19 @@ impl PyRepository {
         py.allow_threads(move || {
             let result =
                 pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
+                    let (storage, storage_settings, asset_manager) = {
+                        let lock = self.0.read().await;
+                        (
+                            Arc::clone(lock.storage()),
+                            lock.storage_settings().clone(),
+                            Arc::clone(lock.asset_manager()),
+                        )
+                    };
+
                     let result = expire(
-                        self.0.storage().as_ref(),
-                        self.0.storage_settings(),
-                        self.0.asset_manager().clone(),
+                        storage.as_ref(),
+                        &storage_settings,
+                        asset_manager,
                         older_than,
                         if delete_expired_branches {
                             ExpiredRefAction::Delete
@@ -877,10 +923,18 @@ impl PyRepository {
                         delete_object_older_than,
                         Default::default(),
                     );
+                    let (storage, storage_settings, asset_manager) = {
+                        let lock = self.0.read().await;
+                        (
+                            Arc::clone(lock.storage()),
+                            lock.storage_settings().clone(),
+                            Arc::clone(lock.asset_manager()),
+                        )
+                    };
                     let result = garbage_collect(
-                        self.0.storage().as_ref(),
-                        self.0.storage_settings(),
-                        self.0.asset_manager().clone(),
+                        storage.as_ref(),
+                        &storage_settings,
+                        asset_manager,
                         &gc_config,
                     )
                     .await
@@ -897,10 +951,18 @@ impl PyRepository {
         py.allow_threads(move || {
             let result =
                 pyo3_async_runtimes::tokio::get_runtime().block_on(async move {
+                    let (storage, storage_settings, asset_manager) = {
+                        let lock = self.0.read().await;
+                        (
+                            Arc::clone(lock.storage()),
+                            lock.storage_settings().clone(),
+                            Arc::clone(lock.asset_manager()),
+                        )
+                    };
                     let result = repo_chunks_storage(
-                        self.0.storage().as_ref(),
-                        self.0.storage_settings(),
-                        self.0.asset_manager().clone(),
+                        storage.as_ref(),
+                        &storage_settings,
+                        asset_manager,
                     )
                     .await
                     .map_err(PyIcechunkStoreError::RepositoryError)?;
diff --git a/icechunk-python/tests/test_pickle.py b/icechunk-python/tests/test_pickle.py
index 1a71bd92b..239bd6e12 100644
--- a/icechunk-python/tests/test_pickle.py
+++ b/icechunk-python/tests/test_pickle.py
@@ -15,7 +15,9 @@
 
 
 def create_local_repo(path: str) -> Repository:
-    return Repository.create(storage=local_filesystem_storage(path))
+    repo = Repository.create(storage=local_filesystem_storage(path))
+    repo.set_default_commit_metadata({"author": "test"})
+    return repo
 
 
 @pytest.fixture(scope="function")
@@ -29,6 +31,8 @@ def test_pickle_repository(tmpdir: Path, tmp_repo: Repository) -> None:
     pickled = pickle.dumps(tmp_repo)
     roundtripped = pickle.loads(pickled)
     assert tmp_repo.list_branches() == roundtripped.list_branches()
+    assert tmp_repo.default_commit_metadata() == roundtripped.default_commit_metadata()
+    assert tmp_repo.default_commit_metadata() == {"author": "test"}
 
     storage = tmp_repo.storage
     assert (
diff --git a/icechunk/src/repository.rs b/icechunk/src/repository.rs
index d52d5de2b..039a82624 100644
--- a/icechunk/src/repository.rs
+++ b/icechunk/src/repository.rs
@@ -16,7 +16,6 @@ use futures::{
 use regex::bytes::Regex;
 use serde::{Deserialize, Serialize};
 use thiserror::Error;
-use tokio::sync::RwLock;
 use tokio::task::JoinError;
 use tracing::{Instrument, debug, error, instrument, trace};
 
@@ -60,7 +59,6 @@ pub enum RepositoryErrorKind {
     FormatError(IcechunkFormatErrorKind),
     #[error(transparent)]
     Ref(RefErrorKind),
-
     #[error("snapshot not found: `{id}`")]
     SnapshotNotFound { id: SnapshotId },
     #[error("branch {branch} does not have a snapshots before or at {at}")]
@@ -139,8 +137,7 @@ pub struct Repository {
     asset_manager: Arc<AssetManager>,
     virtual_resolver: Arc<VirtualChunkResolver>,
     virtual_chunk_credentials: HashMap<ContainerName, Credentials>,
-    #[serde(skip)]
-    default_commit_metadata: Arc<RwLock<Option<SnapshotProperties>>>,
+    default_commit_metadata: SnapshotProperties,
 }
 
 impl Repository {
@@ -312,7 +309,7 @@ impl Repository {
             virtual_resolver,
             asset_manager,
             virtual_chunk_credentials,
-            default_commit_metadata: Arc::new(RwLock::new(None)),
+            default_commit_metadata: SnapshotProperties::default(),
         })
     }
 
@@ -382,17 +379,13 @@ impl Repository {
     }
 
     #[instrument(skip_all)]
-    pub async fn set_default_commit_metadata(
-        &self,
-        metadata: Option<SnapshotProperties>,
-    ) {
-        let mut guard = self.default_commit_metadata.write().await;
-        *guard = metadata;
+    pub fn set_default_commit_metadata(&mut self, metadata: SnapshotProperties) {
+        self.default_commit_metadata = metadata;
     }
 
     #[instrument(skip_all)]
-    pub async fn default_commit_metadata(&self) -> Option<SnapshotProperties> {
-        self.default_commit_metadata.read().await.clone()
+    pub fn default_commit_metadata(&self) -> &SnapshotProperties {
+        &self.default_commit_metadata
     }
 
     #[instrument(skip(storage, config))]
@@ -629,7 +622,7 @@ impl Repository {
     }
 
     #[instrument(skip(self))]
-    async fn resolve_version(
+    pub async fn resolve_version(
         &self,
         version: &VersionInfo,
     ) -> RepositoryResult<SnapshotId> {
@@ -774,7 +767,7 @@ impl Repository {
             self.virtual_resolver.clone(),
             branch.to_string(),
             ref_data.snapshot.clone(),
-            self.default_commit_metadata.read().await.clone(),
+            self.default_commit_metadata.clone(),
         );
 
         self.preload_manifests(ref_data.snapshot);
diff --git a/icechunk/src/session.rs b/icechunk/src/session.rs
index 2364797bc..ce5293180 100644
--- a/icechunk/src/session.rs
+++ b/icechunk/src/session.rs
@@ -166,7 +166,7 @@ pub struct Session {
     branch_name: Option<String>,
     snapshot_id: SnapshotId,
     change_set: ChangeSet,
-    default_commit_metadata: Option<SnapshotProperties>,
+    default_commit_metadata: SnapshotProperties,
 }
 
 impl Session {
@@ -187,7 +187,7 @@ impl Session {
             branch_name: None,
             snapshot_id,
             change_set: ChangeSet::default(),
-            default_commit_metadata: None,
+            default_commit_metadata: SnapshotProperties::default(),
         }
     }
 
@@ -200,7 +200,7 @@ impl Session {
         virtual_resolver: Arc<VirtualChunkResolver>,
         branch_name: String,
         snapshot_id: SnapshotId,
-        default_commit_metadata: Option<SnapshotProperties>,
+        default_commit_metadata: SnapshotProperties,
     ) -> Self {
         Self {
             config,
@@ -811,16 +811,14 @@ impl Session {
             return Err(SessionErrorKind::ReadOnlySession.into());
         };
 
-        let properties = match (properties, self.default_commit_metadata.as_ref()) {
-            (Some(p), None) => Some(p),
-            (None, Some(d)) => Some(d.clone()),
-            (Some(p), Some(d)) => {
-                let mut merged = d.clone();
+        let default_metadata = self.default_commit_metadata.clone();
+        let properties = properties
+            .map(|p| {
+                let mut merged = default_metadata.clone();
                 merged.extend(p.into_iter());
-                Some(merged)
-            }
-            (None, None) => None,
-        };
+                merged
+            })
+            .unwrap_or(default_metadata);
 
         let current = fetch_branch_tip(
             self.storage.as_ref(),
@@ -839,7 +837,7 @@ impl Session {
                     &self.snapshot_id,
                     &self.change_set,
                     message,
-                    properties,
+                    Some(properties),
                 )
                 .await
             }
@@ -861,7 +859,7 @@ impl Session {
                         &self.snapshot_id,
                         &self.change_set,
                         message,
-                        properties,
+                        Some(properties),
                     )
                     .await
                 }
@@ -1969,7 +1967,7 @@ mod tests {
     #[tokio::test(flavor = "multi_thread")]
     async fn test_repository_with_default_commit_metadata() -> Result<(), Box<dyn Error>>
     {
-        let repo = create_memory_store_repository().await;
+        let mut repo = create_memory_store_repository().await;
         let mut ds = repo.writable_session("main").await?;
         ds.add_group(Path::root(), Bytes::new()).await?;
         let snapshot = ds.commit("commit", None).await?;
@@ -1983,7 +1981,7 @@ mod tests {
         let mut default_metadata = SnapshotProperties::default();
         default_metadata.insert("author".to_string(), "John Doe".to_string().into());
         default_metadata.insert("project".to_string(), "My Project".to_string().into());
-        repo.set_default_commit_metadata(Some(default_metadata.clone())).await;
+        repo.set_default_commit_metadata(default_metadata.clone());
 
         let mut ds = repo.writable_session("main").await?;
         ds.add_group("/group".try_into().unwrap(), Bytes::new()).await?;