diff --git a/internal/lsp/cache/session.go b/internal/lsp/cache/session.go
index 4f3bffb215..3da975ddef 100644
--- a/internal/lsp/cache/session.go
+++ b/internal/lsp/cache/session.go
@@ -419,6 +419,7 @@ func (s *Session) updateOverlays(ctx context.Context, changes []source.FileModif
 	return overlays, nil
 }
 
+// GetFile implements the source.FileSystem interface.
 func (s *Session) GetFile(uri span.URI) source.FileHandle {
 	if overlay := s.readOverlay(uri); overlay != nil {
 		return overlay
@@ -436,3 +437,16 @@ func (s *Session) readOverlay(uri span.URI) *overlay {
 	}
 	return nil
 }
+
+func (s *Session) UnsavedFiles() []span.URI {
+	s.overlayMu.Lock()
+	defer s.overlayMu.Unlock()
+
+	var unsaved []span.URI
+	for uri, overlay := range s.overlays {
+		if !overlay.saved {
+			unsaved = append(unsaved, uri)
+		}
+	}
+	return unsaved
+}
diff --git a/internal/lsp/source/view.go b/internal/lsp/source/view.go
index 29b3671e59..e82b11d3f2 100644
--- a/internal/lsp/source/view.go
+++ b/internal/lsp/source/view.go
@@ -185,6 +185,9 @@ type Session interface {
 	// It returns the resulting snapshots, a guaranteed one per view.
 	DidModifyFiles(ctx context.Context, changes []FileModification) ([]Snapshot, error)
 
+	// UnsavedFiles returns a slice of open but unsaved files in the session.
+	UnsavedFiles() []span.URI
+
 	// Options returns a copy of the SessionOptions for this session.
 	Options() Options