diff --git a/include/swift-c/DependencyScan/DependencyScan.h b/include/swift-c/DependencyScan/DependencyScan.h
index 711c59a7af2c5..c65c431d070ed 100644
--- a/include/swift-c/DependencyScan/DependencyScan.h
+++ b/include/swift-c/DependencyScan/DependencyScan.h
@@ -496,6 +496,29 @@ SWIFTSCAN_PUBLIC swiftscan_string_ref_t
 swiftscan_cas_store(swiftscan_cas_t cas, uint8_t *data, unsigned size,
                     swiftscan_string_ref_t *error);
 
+/// Get the local storage size for the CAS in bytes. Return the local storage
+/// size of the CAS/cache data, or -1 if the implementation does not support
+/// reporting such size, or -2 if an error occurred.
+/// If error happens, the error message is returned via `error` parameter, and
+/// caller needs to free the error message via `swiftscan_string_dispose`.
+SWIFTSCAN_PUBLIC int64_t
+swiftscan_cas_get_ondisk_size(swiftscan_cas_t, swiftscan_string_ref_t *error);
+
+/// Set the size for the limiting disk storage size for CAS. \c size_limit is
+/// the maximum size limit in bytes (0 means no limit, negative is invalid).
+/// Return true if error. If error happens, the error message is returned via
+/// `error` parameter, and caller needs to free the error message via
+/// `swiftscan_string_dispose`.
+SWIFTSCAN_PUBLIC bool
+swiftscan_cas_set_ondisk_size_limit(swiftscan_cas_t, int64_t size_limit,
+                                    swiftscan_string_ref_t *error);
+
+/// Prune local CAS storage according to the size limit. Return true if error.
+/// If error happens, the error message is returned via `error` parameter, and
+/// caller needs to free the error message via `swiftscan_string_dispose`.
+SWIFTSCAN_PUBLIC bool
+swiftscan_cas_prune_ondisk_data(swiftscan_cas_t, swiftscan_string_ref_t *error);
+
 /// Dispose the \c cas instance.
 SWIFTSCAN_PUBLIC void swiftscan_cas_dispose(swiftscan_cas_t cas);
 
diff --git a/tools/libSwiftScan/SwiftCaching.cpp b/tools/libSwiftScan/SwiftCaching.cpp
index 1f4a749d1c2b1..21d93206d90d8 100644
--- a/tools/libSwiftScan/SwiftCaching.cpp
+++ b/tools/libSwiftScan/SwiftCaching.cpp
@@ -47,6 +47,7 @@
 #include "llvm/Support/VirtualOutputBackend.h"
 #include "llvm/Support/VirtualOutputBackends.h"
 #include "llvm/Support/raw_ostream.h"
+#include <optional>
 #include <variant>
 
 namespace {
@@ -197,6 +198,53 @@ swiftscan_string_ref_t swiftscan_cas_store(swiftscan_cas_t cas, uint8_t *data,
       CAS.getID(*Result).toString().c_str());
 }
 
+int64_t swiftscan_cas_get_ondisk_size(swiftscan_cas_t cas,
+                                      swiftscan_string_ref_t *error) {
+  auto &CAS = unwrap(cas)->getCAS();
+  std::optional<uint64_t> Size;
+  if (auto E = CAS.getStorageSize().moveInto(Size)) {
+    *error =
+        swift::c_string_utils::create_clone(toString(std::move(E)).c_str());
+    return -2;
+  }
+
+  *error = swift::c_string_utils::create_null();
+  return Size ? *Size : -1;
+}
+
+bool
+swiftscan_cas_set_ondisk_size_limit(swiftscan_cas_t cas, int64_t size_limit,
+    swiftscan_string_ref_t *error) {
+  if (size_limit < 0) {
+    *error = swift::c_string_utils::create_clone(
+        "invalid size limit passing to swiftscan_cas_set_ondisk_size_limit");
+    return true;
+  }
+  auto &CAS = unwrap(cas)->getCAS();
+  std::optional<uint64_t> SizeLimit;
+  if (size_limit > 0)
+    SizeLimit = size_limit;
+  if (auto E = CAS.setSizeLimit(SizeLimit)) {
+    *error =
+        swift::c_string_utils::create_clone(toString(std::move(E)).c_str());
+    return true;
+  }
+  *error = swift::c_string_utils::create_null();
+  return false;
+}
+
+bool swiftscan_cas_prune_ondisk_data(swiftscan_cas_t cas,
+                                     swiftscan_string_ref_t *error) {
+  auto &CAS = unwrap(cas)->getCAS();
+  if (auto E = CAS.pruneStorageData()) {
+    *error =
+        swift::c_string_utils::create_clone(toString(std::move(E)).c_str());
+    return true;
+  }
+  *error = swift::c_string_utils::create_null();
+  return false;
+}
+
 /// Expand the invocation if there is repsonseFile into Args that are passed in
 /// the parameter. Return swift-frontend arguments in an ArrayRef, which has the
 /// first "-frontend" option dropped if needed.
diff --git a/tools/libSwiftScan/libSwiftScan.exports b/tools/libSwiftScan/libSwiftScan.exports
index 0b749aeaf7daf..89bc2dbfaa8d5 100644
--- a/tools/libSwiftScan/libSwiftScan.exports
+++ b/tools/libSwiftScan/libSwiftScan.exports
@@ -77,6 +77,9 @@ swiftscan_diagnostic_get_message
 swiftscan_diagnostic_get_severity
 swiftscan_diagnostics_set_dispose
 swiftscan_cas_create_from_options
+swiftscan_cas_get_ondisk_size
+swiftscan_cas_set_ondisk_size_limit
+swiftscan_cas_prune_ondisk_data
 swiftscan_cas_dispose
 swiftscan_cas_options_create
 swiftscan_cas_options_dispose