diff --git a/mls-rs/src/group/commit.rs b/mls-rs/src/group/commit.rs
index f8caa7c8..f01fb31c 100644
--- a/mls-rs/src/group/commit.rs
+++ b/mls-rs/src/group/commit.rs
@@ -94,6 +94,9 @@ pub struct CommitOutput {
     /// functionality. This value is set if [`MlsRules::commit_options`] returns
     /// `allow_external_commit` set to true.
     pub external_commit_group_info: Option<MlsMessage>,
+    /// Proposals that were received in the prior epoch but not included in the following commit.
+    #[cfg(feature = "by_ref_proposal")]
+    pub unused_proposals: Vec<crate::mls_rules::ProposalInfo<Proposal>>,
 }
 
 #[cfg_attr(all(feature = "ffi", not(test)), ::safer_ffi_gen::safer_ffi_gen)]
@@ -117,6 +120,20 @@ impl CommitOutput {
     pub fn ratchet_tree(&self) -> Option<&ExportedTree<'static>> {
         self.ratchet_tree.as_ref()
     }
+
+    /// A group info that can be provided to new members in order to enable external commit
+    /// functionality. This value is set if [`MlsRules::commit_options`] returns
+    /// `allow_external_commit` set to true.
+    #[cfg(feature = "ffi")]
+    pub fn external_commit_group_info(&self) -> Option<&MlsMessage> {
+        self.external_commit_group_info.as_ref()
+    }
+
+    /// Proposals that were received in the prior epoch but not included in the following commit.
+    #[cfg(all(feature = "ffi", feature = "by_ref_proposal"))]
+    pub fn unused_proposals(&self) -> &[crate::mls_rules::ProposalInfo<Proposal>] {
+        &self.unused_proposals
+    }
 }
 
 /// Build a commit with multiple proposals by-value.
@@ -722,6 +739,8 @@ where
             welcome_messages,
             ratchet_tree,
             external_commit_group_info,
+            #[cfg(feature = "by_ref_proposal")]
+            unused_proposals: provisional_state.rejected_proposals,
         })
     }
 
diff --git a/mls-rs/src/group/framing.rs b/mls-rs/src/group/framing.rs
index 31527e5b..891127a4 100644
--- a/mls-rs/src/group/framing.rs
+++ b/mls-rs/src/group/framing.rs
@@ -36,6 +36,10 @@ impl From<&Content> for ContentType {
     }
 }
 
+#[cfg_attr(
+    all(feature = "ffi", not(test)),
+    safer_ffi_gen::ffi_type(clone, opaque)
+)]
 #[derive(Clone, Copy, Debug, PartialEq, Eq, MlsSize, MlsEncode, MlsDecode)]
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
 #[repr(u8)]
diff --git a/mls-rs/src/group/message_processor.rs b/mls-rs/src/group/message_processor.rs
index ba70ecac..b11c24bc 100644
--- a/mls-rs/src/group/message_processor.rs
+++ b/mls-rs/src/group/message_processor.rs
@@ -35,10 +35,10 @@ use super::proposal_ref::ProposalRef;
 #[cfg(not(feature = "by_ref_proposal"))]
 use crate::group::proposal_cache::resolve_for_commit;
 
-#[cfg(any(feature = "state_update", feature = "by_ref_proposal"))]
+#[cfg(feature = "by_ref_proposal")]
 use super::proposal::Proposal;
 
-#[cfg(all(feature = "state_update", feature = "custom_proposal"))]
+#[cfg(feature = "custom_proposal")]
 use super::proposal_filter::ProposalInfo;
 
 #[cfg(feature = "state_update")]
@@ -72,7 +72,7 @@ pub(crate) struct ProvisionalState {
     pub(crate) group_context: GroupContext,
     pub(crate) external_init_index: Option<LeafIndex>,
     pub(crate) indexes_of_added_kpkgs: Vec<LeafIndex>,
-    #[cfg(all(feature = "state_update", feature = "by_ref_proposal"))]
+    #[cfg(feature = "by_ref_proposal")]
     pub(crate) rejected_proposals: Vec<crate::mls_rules::ProposalInfo<Proposal>>,
 }
 
diff --git a/mls-rs/src/group/proposal_filter/bundle.rs b/mls-rs/src/group/proposal_filter/bundle.rs
index 69d21f45..e2c7c5d3 100644
--- a/mls-rs/src/group/proposal_filter/bundle.rs
+++ b/mls-rs/src/group/proposal_filter/bundle.rs
@@ -434,6 +434,10 @@ impl ProposalBundle {
     }
 }
 
+#[cfg_attr(
+    all(feature = "ffi", not(test)),
+    safer_ffi_gen::ffi_type(clone, opaque)
+)]
 #[derive(Clone, Debug, PartialEq)]
 pub enum ProposalSource {
     ByValue,
@@ -442,6 +446,7 @@ pub enum ProposalSource {
     Local,
 }
 
+#[cfg_attr(all(feature = "ffi", not(test)), safer_ffi_gen::ffi_type(opaque))]
 #[derive(Clone, Debug, PartialEq)]
 #[non_exhaustive]
 /// Proposal description used as input to a
@@ -455,6 +460,9 @@ pub struct ProposalInfo<T> {
     pub source: ProposalSource,
 }
 
+safer_ffi_gen::specialize!(ProposalInfoFfi = crate::group::proposal_filter::ProposalInfo<Proposal>);
+
+#[cfg_attr(all(feature = "ffi", not(test)), ::safer_ffi_gen::safer_ffi_gen)]
 impl ProposalInfo<Proposal> {
     /// Create a new ProposalInfo.
     ///
@@ -464,6 +472,7 @@ impl ProposalInfo<Proposal> {
     ///
     /// This function is useful when implementing custom
     /// [`MlsRules`](crate::MlsRules).
+    #[safer_ffi_gen::safer_ffi_gen_ignore]
     pub fn new(proposal: Proposal, sender: Sender, can_transmit: bool) -> ProposalInfo<Proposal> {
         let source = if can_transmit {
             ProposalSource::ByValue
@@ -477,6 +486,18 @@ impl ProposalInfo<Proposal> {
             source,
         }
     }
+
+    // TODO: Proposal has a lot of cases that we don't have FFI support for yet.
+
+    #[cfg(feature = "ffi")]
+    pub fn sender(&self) -> &Sender {
+        &self.sender
+    }
+
+    #[cfg(feature = "ffi")]
+    pub fn source(&self) -> &ProposalSource {
+        &self.source
+    }
 }
 
 impl<T> ProposalInfo<T> {
diff --git a/mls-rs/src/group/proposal_ref.rs b/mls-rs/src/group/proposal_ref.rs
index c6b10b23..9e9ec483 100644
--- a/mls-rs/src/group/proposal_ref.rs
+++ b/mls-rs/src/group/proposal_ref.rs
@@ -5,6 +5,10 @@
 use super::*;
 use crate::hash_reference::HashReference;
 
+#[cfg_attr(
+    all(feature = "ffi", not(test)),
+    safer_ffi_gen::ffi_type(clone, opaque)
+)]
 #[derive(Debug, Clone, PartialEq, Eq, Hash, PartialOrd, Ord, MlsSize, MlsEncode, MlsDecode)]
 #[cfg_attr(feature = "arbitrary", derive(arbitrary::Arbitrary))]
 /// Unique identifier for a proposal message.
@@ -18,6 +22,7 @@ impl Deref for ProposalRef {
     }
 }
 
+#[cfg_attr(all(feature = "ffi", not(test)), ::safer_ffi_gen::safer_ffi_gen)]
 impl ProposalRef {
     #[cfg_attr(not(mls_build_async), maybe_async::must_be_sync)]
     pub(crate) async fn from_content<CS: CipherSuiteProvider>(
@@ -31,6 +36,10 @@ impl ProposalRef {
                 .await?,
         ))
     }
+
+    pub fn as_slice(&self) -> &[u8] {
+        &self.0
+    }
 }
 
 #[cfg(test)]