diff --git a/integration-tests/src/bindings_tests/replica.c b/integration-tests/src/bindings_tests/replica.c
index 7e598695b..423d8dc25 100644
--- a/integration-tests/src/bindings_tests/replica.c
+++ b/integration-tests/src/bindings_tests/replica.c
@@ -40,12 +40,74 @@ static void test_replica_add_undo_point(void) {
     tc_replica_free(rep);
 }
 
-// rebuilding working set succeeds
-static void test_replica_rebuild_working_set(void) {
+// working set operations succeed
+static void test_replica_working_set(void) {
+    TCWorkingSet *ws;
+    TCTask *task1, *task2, *task3;
+    TCUuid uuid, uuid1, uuid2, uuid3;
+
     TCReplica *rep = tc_replica_new_in_memory();
     TEST_ASSERT_NULL(tc_replica_error(rep));
+
     TEST_ASSERT_EQUAL(TC_RESULT_OK, tc_replica_rebuild_working_set(rep, true));
     TEST_ASSERT_NULL(tc_replica_error(rep));
+
+    ws = tc_replica_working_set(rep);
+    TEST_ASSERT_EQUAL(0, tc_working_set_len(ws));
+    tc_working_set_free(ws);
+
+    task1 = tc_replica_new_task(rep, TC_STATUS_PENDING, tc_string_borrow("task1"));
+    TEST_ASSERT_NOT_NULL(task1);
+    uuid1 = tc_task_get_uuid(task1);
+
+    TEST_ASSERT_EQUAL(TC_RESULT_OK, tc_replica_rebuild_working_set(rep, true));
+    TEST_ASSERT_NULL(tc_replica_error(rep));
+
+    task2 = tc_replica_new_task(rep, TC_STATUS_PENDING, tc_string_borrow("task2"));
+    TEST_ASSERT_NOT_NULL(task2);
+    uuid2 = tc_task_get_uuid(task2);
+
+    task3 = tc_replica_new_task(rep, TC_STATUS_PENDING, tc_string_borrow("task3"));
+    TEST_ASSERT_NOT_NULL(task3);
+    uuid3 = tc_task_get_uuid(task3);
+
+    TEST_ASSERT_EQUAL(TC_RESULT_OK, tc_replica_rebuild_working_set(rep, false));
+    TEST_ASSERT_NULL(tc_replica_error(rep));
+
+    // finish task2 to leave a "hole"
+    tc_task_to_mut(task2, rep);
+    TEST_ASSERT_EQUAL(TC_RESULT_OK, tc_task_done(task2));
+    tc_task_to_immut(task2);
+
+    TEST_ASSERT_EQUAL(TC_RESULT_OK, tc_replica_rebuild_working_set(rep, false));
+    TEST_ASSERT_NULL(tc_replica_error(rep));
+
+    tc_task_free(task1);
+    tc_task_free(task2);
+    tc_task_free(task3);
+
+    // working set should now be
+    //  0 -> None
+    //  1 -> uuid1
+    //  2 -> None
+    //  3 -> uuid3
+    ws = tc_replica_working_set(rep);
+    TEST_ASSERT_EQUAL(2, tc_working_set_len(ws));
+    TEST_ASSERT_EQUAL(3, tc_working_set_largest_index(ws));
+
+    TEST_ASSERT_FALSE(tc_working_set_by_index(ws, 0, &uuid));
+    TEST_ASSERT_TRUE(tc_working_set_by_index(ws, 1, &uuid));
+    TEST_ASSERT_EQUAL_MEMORY(uuid1.bytes, uuid.bytes, sizeof(uuid));
+    TEST_ASSERT_FALSE(tc_working_set_by_index(ws, 2, &uuid));
+    TEST_ASSERT_TRUE(tc_working_set_by_index(ws, 3, &uuid));
+    TEST_ASSERT_EQUAL_MEMORY(uuid3.bytes, uuid.bytes, sizeof(uuid));
+
+    TEST_ASSERT_EQUAL(1, tc_working_set_by_uuid(ws, uuid1));
+    TEST_ASSERT_EQUAL(0, tc_working_set_by_uuid(ws, uuid2));
+    TEST_ASSERT_EQUAL(3, tc_working_set_by_uuid(ws, uuid3));
+
+    tc_working_set_free(ws);
+
     tc_replica_free(rep);
 }
 
@@ -209,7 +271,7 @@ int replica_tests(void) {
     RUN_TEST(test_replica_creation_disk);
     RUN_TEST(test_replica_undo_empty);
     RUN_TEST(test_replica_add_undo_point);
-    RUN_TEST(test_replica_rebuild_working_set);
+    RUN_TEST(test_replica_working_set);
     RUN_TEST(test_replica_undo_empty_null_undone_out);
     RUN_TEST(test_replica_task_creation);
     RUN_TEST(test_replica_all_tasks);
diff --git a/lib/src/lib.rs b/lib/src/lib.rs
index 5bc7629a3..b49acf77c 100644
--- a/lib/src/lib.rs
+++ b/lib/src/lib.rs
@@ -14,6 +14,7 @@ pub mod string;
 pub mod task;
 pub mod uda;
 pub mod uuid;
+pub mod workingset;
 
 pub(crate) mod types {
     pub(crate) use crate::annotation::{TCAnnotation, TCAnnotationList};
@@ -24,4 +25,5 @@ pub(crate) mod types {
     pub(crate) use crate::task::{TCTask, TCTaskList};
     pub(crate) use crate::uda::{TCUDAList, TCUDA, UDA};
     pub(crate) use crate::uuid::{TCUuid, TCUuidList};
+    pub(crate) use crate::workingset::TCWorkingSet;
 }
diff --git a/lib/src/replica.rs b/lib/src/replica.rs
index 99f07639d..b89df1091 100644
--- a/lib/src/replica.rs
+++ b/lib/src/replica.rs
@@ -177,7 +177,21 @@ pub unsafe extern "C" fn tc_replica_all_task_uuids(rep: *mut TCReplica) -> TCUui
     )
 }
 
-// TODO: tc_replica_working_set
+/// Get the current working set for this replica.
+///
+/// Returns NULL on error.
+#[no_mangle]
+pub unsafe extern "C" fn tc_replica_working_set(rep: *mut TCReplica) -> *mut TCWorkingSet {
+    wrap(
+        rep,
+        |rep| {
+            let ws = rep.working_set()?;
+            // SAFETY: caller promises to free this task
+            Ok(unsafe { TCWorkingSet::return_val(ws.into()) })
+        },
+        std::ptr::null_mut(),
+    )
+}
 
 /// Get an existing task by its UUID.
 ///
diff --git a/lib/src/workingset.rs b/lib/src/workingset.rs
new file mode 100644
index 000000000..91f73bbd0
--- /dev/null
+++ b/lib/src/workingset.rs
@@ -0,0 +1,87 @@
+use crate::traits::*;
+use crate::types::*;
+use taskchampion::{Uuid, WorkingSet};
+
+/// A TCWorkingSet represents a snapshot of the working set for a replica.  It is not automatically
+/// updated based on changes in the replica.  Its lifetime is independent of the replica and it can
+/// be freed at any time.
+///
+/// To iterate over a working set, search indexes 1 through largest_index.
+pub struct TCWorkingSet(WorkingSet);
+
+impl PassByPointer for TCWorkingSet {}
+
+impl From<WorkingSet> for TCWorkingSet {
+    fn from(ws: WorkingSet) -> TCWorkingSet {
+        TCWorkingSet(ws)
+    }
+}
+
+/// Utility function to get a shared reference to the underlying WorkingSet.
+fn wrap<'a, T, F>(ws: *mut TCWorkingSet, f: F) -> T
+where
+    F: FnOnce(&WorkingSet) -> T,
+{
+    // SAFETY:
+    //  - ws is not null (promised by caller)
+    //  - ws outlives 'a (promised by caller)
+    let tcws: &'a TCWorkingSet = unsafe { TCWorkingSet::from_arg_ref(ws) };
+    f(&tcws.0)
+}
+
+/// Get the working set's length, or the number of UUIDs it contains.
+#[no_mangle]
+pub unsafe extern "C" fn tc_working_set_len(ws: *mut TCWorkingSet) -> usize {
+    wrap(ws, |ws| ws.len())
+}
+
+/// Get the working set's largest index.
+#[no_mangle]
+pub unsafe extern "C" fn tc_working_set_largest_index(ws: *mut TCWorkingSet) -> usize {
+    wrap(ws, |ws| ws.largest_index())
+}
+
+/// Get the UUID for the task at the given index.  Returns true if the UUID exists in the working
+/// set.  If not, returns false and does not change uuid_out.
+#[no_mangle]
+pub unsafe extern "C" fn tc_working_set_by_index(
+    ws: *mut TCWorkingSet,
+    index: usize,
+    uuid_out: *mut TCUuid,
+) -> bool {
+    debug_assert!(!uuid_out.is_null());
+    wrap(ws, |ws| {
+        if let Some(uuid) = ws.by_index(index) {
+            // SAFETY:
+            //  - uuid_out is not NULL (promised by caller)
+            //  - alignment is not required
+            unsafe { TCUuid::to_arg_out(uuid, uuid_out) };
+            true
+        } else {
+            false
+        }
+    })
+}
+
+/// Get the working set index for the task with the given UUID.  Returns 0 if the task is not in
+/// the working set.
+#[no_mangle]
+pub unsafe extern "C" fn tc_working_set_by_uuid(ws: *mut TCWorkingSet, uuid: TCUuid) -> usize {
+    wrap(ws, |ws| {
+        // SAFETY:
+        //  - tcuuid is a valid TCUuid (all byte patterns are valid)
+        let uuid: Uuid = unsafe { TCUuid::from_arg(uuid) };
+        ws.by_uuid(uuid).unwrap_or(0)
+    })
+}
+
+/// Free a TCWorkingSet.  The given value must not be NULL.  The value must not be used after this
+/// function returns, and must not be freed more than once.
+#[no_mangle]
+pub unsafe extern "C" fn tc_working_set_free(ws: *mut TCWorkingSet) {
+    // SAFETY:
+    //  - rep is not NULL (promised by caller)
+    //  - caller will not use the TCWorkingSet after this (promised by caller)
+    let ws = unsafe { TCWorkingSet::take_from_arg(ws) };
+    drop(ws);
+}
diff --git a/lib/taskchampion.h b/lib/taskchampion.h
index bc61b1e40..79b25ba35 100644
--- a/lib/taskchampion.h
+++ b/lib/taskchampion.h
@@ -117,6 +117,15 @@ typedef struct TCString TCString;
  */
 typedef struct TCTask TCTask;
 
+/**
+ * A TCWorkingSet represents a snapshot of the working set for a replica.  It is not automatically
+ * updated based on changes in the replica.  Its lifetime is independent of the replica and it can
+ * be freed at any time.
+ *
+ * To iterate over a working set, search indexes 1 through largest_index.
+ */
+typedef struct TCWorkingSet TCWorkingSet;
+
 /**
  * TCAnnotation contains the details of an annotation.
  */
@@ -309,6 +318,13 @@ struct TCTaskList tc_replica_all_tasks(struct TCReplica *rep);
  */
 struct TCUuidList tc_replica_all_task_uuids(struct TCReplica *rep);
 
+/**
+ * Get the current working set for this replica.
+ *
+ * Returns NULL on error.
+ */
+struct TCWorkingSet *tc_replica_working_set(struct TCReplica *rep);
+
 /**
  * Get an existing task by its UUID.
  *
@@ -721,6 +737,34 @@ TCResult tc_uuid_from_str(struct TCString *s, struct TCUuid *uuid_out);
  */
 void tc_uuid_list_free(struct TCUuidList *tcuuids);
 
+/**
+ * Get the working set's length, or the number of UUIDs it contains.
+ */
+size_t tc_working_set_len(struct TCWorkingSet *ws);
+
+/**
+ * Get the working set's largest index.
+ */
+size_t tc_working_set_largest_index(struct TCWorkingSet *ws);
+
+/**
+ * Get the UUID for the task at the given index.  Returns true if the UUID exists in the working
+ * set.  If not, returns false and does not change uuid_out.
+ */
+bool tc_working_set_by_index(struct TCWorkingSet *ws, size_t index, struct TCUuid *uuid_out);
+
+/**
+ * Get the working set index for the task with the given UUID.  Returns 0 if the task is not in
+ * the working set.
+ */
+size_t tc_working_set_by_uuid(struct TCWorkingSet *ws, struct TCUuid uuid);
+
+/**
+ * Free a TCWorkingSet.  The given value must not be NULL.  The value must not be used after this
+ * function returns, and must not be freed more than once.
+ */
+void tc_working_set_free(struct TCWorkingSet *ws);
+
 #ifdef __cplusplus
 } // extern "C"
 #endif // __cplusplus
diff --git a/taskchampion/src/workingset.rs b/taskchampion/src/workingset.rs
index ea746a72b..8bd0cce53 100644
--- a/taskchampion/src/workingset.rs
+++ b/taskchampion/src/workingset.rs
@@ -38,6 +38,11 @@ impl WorkingSet {
         self.by_index.iter().filter(|e| e.is_some()).count()
     }
 
+    /// Get the largest index in the working set, or zero if the set is empty.
+    pub fn largest_index(&self) -> usize {
+        self.by_index.len().saturating_sub(1)
+    }
+
     /// True if the length is zero
     pub fn is_empty(&self) -> bool {
         self.by_index.iter().all(|e| e.is_none())
@@ -103,6 +108,21 @@ mod test {
         assert_eq!(ws.is_empty(), true);
     }
 
+    #[test]
+    fn test_largest_index() {
+        let (uuid1, uuid2, ws) = make();
+        assert_eq!(ws.largest_index(), 0);
+
+        let ws = WorkingSet::new(vec![None, Some(uuid1)]);
+        assert_eq!(ws.largest_index(), 1);
+
+        let ws = WorkingSet::new(vec![None, Some(uuid1), None, Some(uuid2)]);
+        assert_eq!(ws.largest_index(), 3);
+
+        let ws = WorkingSet::new(vec![None, Some(uuid1), None, Some(uuid2), None]);
+        assert_eq!(ws.largest_index(), 4);
+    }
+
     #[test]
     fn test_by_index() {
         let (uuid1, uuid2, ws) = make();