diff --git a/internal/lsp/cache/session.go b/internal/lsp/cache/session.go
index 00fc455..9affdb5 100644
--- a/internal/lsp/cache/session.go
+++ b/internal/lsp/cache/session.go
@@ -27,7 +27,8 @@
 	cache *Cache
 	id    string
 
-	options *source.Options
+	optionsMu sync.Mutex
+	options   *source.Options
 
 	viewMu  sync.Mutex
 	views   []*View
@@ -118,10 +119,14 @@
 func (s *Session) String() string { return s.id }
 
 func (s *Session) Options() *source.Options {
+	s.optionsMu.Lock()
+	defer s.optionsMu.Unlock()
 	return s.options
 }
 
 func (s *Session) SetOptions(options *source.Options) {
+	s.optionsMu.Lock()
+	defer s.optionsMu.Unlock()
 	s.options = options
 }
 
diff --git a/internal/lsp/cmd/semantictokens.go b/internal/lsp/cmd/semantictokens.go
index 93f2cdb..0bcb487 100644
--- a/internal/lsp/cmd/semantictokens.go
+++ b/internal/lsp/cmd/semantictokens.go
@@ -114,8 +114,7 @@
 	tok := fset.File(f.Pos())
 	if tok == nil {
 		// can't happen; just parsed this file
-		log.Printf("tok is nil!")
-		return fmt.Errorf("can't find %s in fset!", args[0])
+		return fmt.Errorf("can't find %s in fset", args[0])
 	}
 	tc := span.NewContentConverter(args[0], buf)
 	colmap = &protocol.ColumnMapper{
diff --git a/internal/lsp/general.go b/internal/lsp/general.go
index 11f2f3e..a6de385 100644
--- a/internal/lsp/general.go
+++ b/internal/lsp/general.go
@@ -82,10 +82,14 @@
 		}
 	}
 
+	if st := params.Capabilities.TextDocument.SemanticTokens; st != nil {
+		rememberToks(st.TokenTypes, st.TokenModifiers)
+	}
+
 	goplsVer := &bytes.Buffer{}
 	debug.PrintVersionInfo(ctx, goplsVer, true, debug.PlainText)
 
-	ans := &protocol.InitializeResult{
+	return &protocol.InitializeResult{
 		Capabilities: protocol.ServerCapabilities{
 			CallHierarchyProvider: true,
 			CodeActionProvider:    codeActionProvider,
@@ -131,25 +135,7 @@
 			Name:    "gopls",
 			Version: goplsVer.String(),
 		},
-	}
-
-	st := params.Capabilities.TextDocument.SemanticTokens
-	if st != nil {
-		tokTypes, tokModifiers := rememberToks(st.TokenTypes, st.TokenModifiers)
-		// check that st.TokenFormat is "relative"
-		v := &protocol.SemanticTokensOptions{
-			Legend: protocol.SemanticTokensLegend{
-				// TODO(pjw): trim these to what we use (and an unused one
-				// at position 0 of TokTypes, to catch typos)
-				TokenTypes:     tokTypes,
-				TokenModifiers: tokModifiers,
-			},
-			Range: true,
-			Full:  true,
-		}
-		ans.Capabilities.SemanticTokensProvider = v
-	}
-	return ans, nil
+	}, nil
 }
 
 func (s *Server) initialized(ctx context.Context, params *protocol.InitializedParams) error {
@@ -175,17 +161,22 @@
 	s.pendingFolders = nil
 
 	if options.ConfigurationSupported && options.DynamicConfigurationSupported {
-		if err := s.client.RegisterCapability(ctx, &protocol.RegistrationParams{
-			Registrations: []protocol.Registration{
-				{
-					ID:     "workspace/didChangeConfiguration",
-					Method: "workspace/didChangeConfiguration",
-				},
-				{
-					ID:     "workspace/didChangeWorkspaceFolders",
-					Method: "workspace/didChangeWorkspaceFolders",
-				},
+		registrations := []protocol.Registration{
+			{
+				ID:     "workspace/didChangeConfiguration",
+				Method: "workspace/didChangeConfiguration",
 			},
+			{
+				ID:     "workspace/didChangeWorkspaceFolders",
+				Method: "workspace/didChangeWorkspaceFolders",
+			},
+		}
+		if options.SemanticTokens {
+			registrations = append(registrations, semanticTokenRegistrations()...)
+
+		}
+		if err := s.client.RegisterCapability(ctx, &protocol.RegistrationParams{
+			Registrations: registrations,
 		}); err != nil {
 			return err
 		}
diff --git a/internal/lsp/semantic.go b/internal/lsp/semantic.go
index f883a67..b0f42d6 100644
--- a/internal/lsp/semantic.go
+++ b/internal/lsp/semantic.go
@@ -595,7 +595,7 @@
 }
 
 // save what the client sent
-func rememberToks(toks []string, mods []string) ([]string, []string) {
+func rememberToks(toks []string, mods []string) {
 	SemanticMemo = &SemMemo{
 		tokTypes: toks,
 		tokMods:  mods,
@@ -610,7 +610,6 @@
 	}
 	// we could have pruned or rearranged them.
 	// But then change the list in cmd.go too
-	return SemanticMemo.tokTypes, SemanticMemo.tokMods
 }
 
 // SemanticTypes to use in case there is no client, as in the command line, or tests
diff --git a/internal/lsp/workspace.go b/internal/lsp/workspace.go
index 72123a2..beced5a 100644
--- a/internal/lsp/workspace.go
+++ b/internal/lsp/workspace.go
@@ -41,8 +41,16 @@
 	return snapshot, release, err
 }
 
-func (s *Server) didChangeConfiguration(ctx context.Context, changed interface{}) error {
-	// go through all the views getting the config
+func (s *Server) didChangeConfiguration(ctx context.Context, _ *protocol.DidChangeConfigurationParams) error {
+	// Apply any changes to the session-level settings.
+	options := s.session.Options().Clone()
+	semanticTokensRegistered := options.SemanticTokens
+	if err := s.fetchConfig(ctx, "", "", options); err != nil {
+		return err
+	}
+	s.session.SetOptions(options)
+
+	// Go through each view, getting and updating its configuration.
 	for _, view := range s.session.Views() {
 		options := s.session.Options().Clone()
 		if err := s.fetchConfig(ctx, view.Name(), view.Folder(), options); err != nil {
@@ -58,5 +66,50 @@
 			s.diagnoseDetached(snapshot)
 		}()
 	}
+
+	// Update any session-specific registrations or unregistrations.
+	if !semanticTokensRegistered && options.SemanticTokens {
+		if err := s.client.RegisterCapability(ctx, &protocol.RegistrationParams{
+			Registrations: semanticTokenRegistrations(),
+		}); err != nil {
+			return err
+		}
+	} else if semanticTokensRegistered && !options.SemanticTokens {
+		var unregistrations []protocol.Unregistration
+		for _, r := range semanticTokenRegistrations() {
+			unregistrations = append(unregistrations, protocol.Unregistration{
+				ID:     r.ID,
+				Method: r.Method,
+			})
+		}
+		if err := s.client.UnregisterCapability(ctx, &protocol.UnregistrationParams{
+			Unregisterations: unregistrations,
+		}); err != nil {
+			return err
+		}
+	}
 	return nil
 }
+
+func semanticTokenRegistrations() []protocol.Registration {
+	var registrations []protocol.Registration
+	for _, method := range []string{
+		"textDocument/semanticTokens/full",
+		"textDocument/semanticTokens/full/delta",
+		"textDocument/semanticTokens/range",
+	} {
+		registrations = append(registrations, protocol.Registration{
+			ID:     method,
+			Method: method,
+			RegisterOptions: &protocol.SemanticTokensOptions{
+				Legend: protocol.SemanticTokensLegend{
+					// TODO(pjw): trim these to what we use (and an unused one
+					// at position 0 of TokTypes, to catch typos)
+					TokenTypes:     SemanticMemo.tokTypes,
+					TokenModifiers: SemanticMemo.tokMods,
+				},
+			},
+		})
+	}
+	return registrations
+}