diff --git a/internal/lsp/cache/session.go b/internal/lsp/cache/session.go
index 16a928ea..f16814f0 100644
--- a/internal/lsp/cache/session.go
+++ b/internal/lsp/cache/session.go
@@ -44,9 +44,9 @@ type overlay struct {
 	hash    string
 	kind    source.FileKind
 
-	// onDisk is true if a file has been saved on disk,
+	// sameContentOnDisk is true if a file has been saved on disk,
 	// and therefore does not need to be part of the overlay sent to go/packages.
-	onDisk bool
+	sameContentOnDisk bool
 }
 
 func (s *session) Shutdown(ctx context.Context) {
@@ -182,14 +182,17 @@ func (s *session) Logger() xlog.Logger {
 	return s.log
 }
 
-func (s *session) DidOpen(ctx context.Context, uri span.URI) {
+func (s *session) DidOpen(ctx context.Context, uri span.URI, text []byte) {
+	// Mark the file as open.
 	s.openFiles.Store(uri, true)
 
+	// Read the file on disk and compare it to the text provided.
+	// If it is the same as on disk, we can avoid sending it as an overlay to go/packages.
+	s.openOverlay(ctx, uri, text)
+
 	// Mark the file as just opened so that we know to re-run packages.Load on it.
 	// We do this because we may not be aware of all of the packages the file belongs to.
-
 	// A file may be in multiple views.
-	// For each view, get the file and mark it as just opened.
 	for _, view := range s.views {
 		if strings.HasPrefix(string(uri), string(view.Folder())) {
 			f, err := view.GetFile(ctx, uri)
@@ -215,7 +218,7 @@ func (s *session) DidSave(uri span.URI) {
 	defer s.overlayMu.Unlock()
 
 	if overlay, ok := s.overlays[uri]; ok {
-		overlay.onDisk = true
+		overlay.sameContentOnDisk = true
 	}
 }
 
@@ -255,6 +258,30 @@ func (s *session) SetOverlay(uri span.URI, data []byte) {
 	}
 }
 
+// openOverlay adds the file content to the overlay.
+// It also checks if the provided content is equivalent to the file's content on disk.
+func (s *session) openOverlay(ctx context.Context, uri span.URI, data []byte) {
+	s.overlayMu.Lock()
+	defer func() {
+		s.overlayMu.Unlock()
+		s.filesWatchMap.Notify(uri)
+	}()
+	s.overlays[uri] = &overlay{
+		session: s,
+		uri:     uri,
+		data:    data,
+		hash:    hashContents(data),
+	}
+	_, hash, err := s.cache.GetFile(uri).Read(ctx)
+	if err != nil {
+		s.log.Errorf(ctx, "failed to read %s: %v", uri, err)
+		return
+	}
+	if hash == s.overlays[uri].hash {
+		s.overlays[uri].sameContentOnDisk = true
+	}
+}
+
 func (s *session) readOverlay(uri span.URI) *overlay {
 	s.overlayMu.Lock()
 	defer s.overlayMu.Unlock()
@@ -272,7 +299,7 @@ func (s *session) buildOverlay() map[string][]byte {
 
 	overlays := make(map[string][]byte)
 	for uri, overlay := range s.overlays {
-		if overlay.onDisk {
+		if overlay.sameContentOnDisk {
 			continue
 		}
 		overlays[uri.Filename()] = overlay.data
diff --git a/internal/lsp/source/view.go b/internal/lsp/source/view.go
index b2619e99..872e463c 100644
--- a/internal/lsp/source/view.go
+++ b/internal/lsp/source/view.go
@@ -154,7 +154,7 @@ type Session interface {
 	FileSystem
 
 	// DidOpen is invoked each time a file is opened in the editor.
-	DidOpen(ctx context.Context, uri span.URI)
+	DidOpen(ctx context.Context, uri span.URI, text []byte)
 
 	// DidSave is invoked each time an open file is saved in the editor.
 	DidSave(uri span.URI)
diff --git a/internal/lsp/text_synchronization.go b/internal/lsp/text_synchronization.go
index 4cd88532..7fe8d81e 100644
--- a/internal/lsp/text_synchronization.go
+++ b/internal/lsp/text_synchronization.go
@@ -17,8 +17,18 @@ import (
 
 func (s *Server) didOpen(ctx context.Context, params *protocol.DidOpenTextDocumentParams) error {
 	uri := span.NewURI(params.TextDocument.URI)
-	s.session.DidOpen(ctx, uri)
-	return s.cacheAndDiagnose(ctx, uri, []byte(params.TextDocument.Text))
+	text := []byte(params.TextDocument.Text)
+
+	// Open the file.
+	s.session.DidOpen(ctx, uri, text)
+
+	// Run diagnostics on the newly-changed file.
+	view := s.session.ViewOf(uri)
+	go func() {
+		ctx := view.BackgroundContext()
+		s.Diagnostics(ctx, view, uri)
+	}()
+	return nil
 }
 
 func (s *Server) didChange(ctx context.Context, params *protocol.DidChangeTextDocumentParams) error {
@@ -46,16 +56,12 @@ func (s *Server) didChange(ctx context.Context, params *protocol.DidChangeTextDo
 			}
 		}
 	}
-
 	// Cache the new file content and send fresh diagnostics.
-	return s.cacheAndDiagnose(ctx, uri, []byte(text))
-}
-
-func (s *Server) cacheAndDiagnose(ctx context.Context, uri span.URI, content []byte) error {
 	view := s.session.ViewOf(uri)
-	if err := view.SetContent(ctx, uri, content); err != nil {
+	if err := view.SetContent(ctx, uri, []byte(text)); err != nil {
 		return err
 	}
+	// Run diagnostics on the newly-changed file.
 	go func() {
 		ctx := view.BackgroundContext()
 		s.Diagnostics(ctx, view, uri)