diff --git a/openmls/src/group/errors.rs b/openmls/src/group/errors.rs
index 37a9a72ad..50e2e8317 100644
--- a/openmls/src/group/errors.rs
+++ b/openmls/src/group/errors.rs
@@ -500,7 +500,7 @@ pub(crate) enum CoreGroupParseMessageError {
 
 /// Create group context ext proposal error
 #[derive(Error, Debug, PartialEq, Clone)]
-pub enum CreateGroupContextExtProposalError {
+pub enum CreateGroupContextExtProposalError<StorageError> {
     /// See [`LibraryError`] for more details.
     #[error(transparent)]
     LibraryError(#[from] LibraryError),
@@ -513,6 +513,12 @@ pub enum CreateGroupContextExtProposalError {
     /// See [`LeafNodeValidationError`] for more details.
     #[error(transparent)]
     LeafNodeValidation(#[from] LeafNodeValidationError),
+    /// See [`MlsGroupStateError`] for more details.
+    #[error(transparent)]
+    MlsGroupStateError(#[from] MlsGroupStateError<StorageError>),
+    /// See [`CreateCommitError`] for more details.
+    #[error(transparent)]
+    CreateCommitError(#[from] CreateCommitError<StorageError>),
 }
 
 /// Error merging a commit.
@@ -537,6 +543,15 @@ pub enum GroupContextExtensionsProposalValidationError {
     #[error(transparent)]
     LibraryError(#[from] LibraryError),
 
+    /// The new extension types in required capabilties contails extensions that are not supported by all group members.
+    #[error(
+        "The new required capabilties contain extension types that are not supported by all group members."
+    )]
+    ExtensionNotSupportedByAllMembers,
+    /// Proposal changes the immutable metadata extension, which is not allowed.
+    #[error("Proposal changes the immutable metadata extension, which is not allowed.")]
+    ChangedImmutableMetadata,
+
     /// The new extension types in required capabilties contails extensions that are not supported by all group members.
     #[error(
         "The new required capabilties contain extension types that are not supported by all group members."
diff --git a/openmls/src/group/mls_group/membership.rs b/openmls/src/group/mls_group/membership.rs
index 0416b4bfd..b22c723ed 100644
--- a/openmls/src/group/mls_group/membership.rs
+++ b/openmls/src/group/mls_group/membership.rs
@@ -214,6 +214,23 @@ impl MlsGroup {
             .leaf(leaf_index)
             .map(|leaf| leaf.credential())
     }
+
+    /// Returns the [`Member`] corresponding to the given
+    /// leaf index. Returns `None` if the member can not be found in this group.
+    pub fn member_at(&self, leaf_index: LeafNodeIndex) -> Option<Member> {
+        self.group
+            .public_group()
+            // This will return an error if the member can't be found.
+            .leaf(leaf_index)
+            .map(|leaf_node| {
+                Member::new(
+                    leaf_index,
+                    leaf_node.encryption_key().as_slice().to_vec(),
+                    leaf_node.signature_key().as_slice().to_vec(),
+                    leaf_node.credential().clone(),
+                )
+            })
+    }
 }
 
 /// Helper `enum` that classifies the kind of remove operation. This can be used to
diff --git a/openmls/src/group/mls_group/proposal.rs b/openmls/src/group/mls_group/proposal.rs
index 19bfd78d5..a747ac141 100644
--- a/openmls/src/group/mls_group/proposal.rs
+++ b/openmls/src/group/mls_group/proposal.rs
@@ -1,8 +1,10 @@
 use openmls_traits::{signatures::Signer, storage::StorageProvider, types::Ciphersuite};
 
 use super::{
+    core_group::create_commit_params::CreateCommitParams,
     errors::{ProposalError, ProposeAddMemberError, ProposeRemoveMemberError},
-    CustomProposal, MlsGroup,
+    CreateGroupContextExtProposalError, CustomProposal, GroupContextExtensionProposal, MlsGroup,
+    MlsGroupState, PendingCommitState, Proposal,
 };
 use crate::{
     binary_tree::LeafNodeIndex,
@@ -12,7 +14,7 @@ use crate::{
     framing::MlsMessageOut,
     group::{errors::CreateAddProposalError, GroupId, QueuedProposal},
     key_packages::KeyPackage,
-    messages::proposals::ProposalOrRefType,
+    messages::{group_info::GroupInfo, proposals::ProposalOrRefType},
     prelude::LibraryError,
     schedule::PreSharedKeyId,
     storage::OpenMlsProvider,
@@ -384,4 +386,46 @@ impl MlsGroup {
 
         Ok((mls_message, proposal_ref))
     }
+
+    /// Updates group context extensions
+    ///
+    /// Returns an error when the group does not support all the required capabilities
+    /// in the new `extensions`.
+    #[allow(clippy::type_complexity)]
+    pub fn update_group_context_extensions<Provider: OpenMlsProvider>(
+        &mut self,
+        provider: &Provider,
+        extensions: Extensions,
+        signer: &impl Signer,
+    ) -> Result<
+        (MlsMessageOut, Option<MlsMessageOut>, Option<GroupInfo>),
+        CreateGroupContextExtProposalError<Provider::StorageError>,
+    > {
+        self.is_operational()?;
+
+        // Create group context extension proposals
+        let inline_proposals = vec![Proposal::GroupContextExtensions(
+            GroupContextExtensionProposal { extensions },
+        )];
+
+        let params = CreateCommitParams::builder()
+            .framing_parameters(self.framing_parameters())
+            .proposal_store(&self.proposal_store)
+            .inline_proposals(inline_proposals)
+            .build();
+        let create_commit_result = self.group.create_commit(params, provider, signer)?;
+
+        let mls_messages = self.content_to_mls_message(create_commit_result.commit, provider)?;
+        self.group_state = MlsGroupState::PendingCommit(Box::new(PendingCommitState::Member(
+            create_commit_result.staged_commit,
+        )));
+
+        Ok((
+            mls_messages,
+            create_commit_result
+                .welcome_option
+                .map(|w| MlsMessageOut::from_welcome(w, self.group.version())),
+            create_commit_result.group_info,
+        ))
+    }
 }
diff --git a/openmls/src/key_packages/mod.rs b/openmls/src/key_packages/mod.rs
index 558b73efa..cf5369500 100644
--- a/openmls/src/key_packages/mod.rs
+++ b/openmls/src/key_packages/mod.rs
@@ -401,6 +401,11 @@ impl KeyPackage {
     pub fn last_resort(&self) -> bool {
         self.payload.extensions.contains(ExtensionType::LastResort)
     }
+
+    /// Get the lifetime of the KeyPackage
+    pub fn life_time(&self) -> &Lifetime {
+        self.payload.leaf_node.life_time().unwrap()
+    }
 }
 
 /// Crate visible `KeyPackage` functions.
diff --git a/openmls/src/messages/proposals.rs b/openmls/src/messages/proposals.rs
index 181fa7cb9..c13a236c0 100644
--- a/openmls/src/messages/proposals.rs
+++ b/openmls/src/messages/proposals.rs
@@ -468,7 +468,7 @@ pub struct AppAckProposal {
     TlsSize,
 )]
 pub struct GroupContextExtensionProposal {
-    extensions: Extensions,
+    pub(crate) extensions: Extensions,
 }
 
 impl GroupContextExtensionProposal {
@@ -478,7 +478,7 @@ impl GroupContextExtensionProposal {
     }
 
     /// Get the extensions of the proposal
-    pub(crate) fn extensions(&self) -> &Extensions {
+    pub fn extensions(&self) -> &Extensions {
         &self.extensions
     }
 }