diff --git a/src/plugins/languageclient/client.cpp b/src/plugins/languageclient/client.cpp
index 77462e1833f..79108970594 100644
--- a/src/plugins/languageclient/client.cpp
+++ b/src/plugins/languageclient/client.cpp
@@ -34,9 +34,11 @@
 #include <coreplugin/icore.h>
 #include <coreplugin/idocument.h>
 #include <coreplugin/messagemanager.h>
+#include <languageserverprotocol/completion.h>
 #include <languageserverprotocol/diagnostics.h>
 #include <languageserverprotocol/languagefeatures.h>
 #include <languageserverprotocol/messages.h>
+#include <languageserverprotocol/servercapabilities.h>
 #include <languageserverprotocol/workspace.h>
 #include <projectexplorer/project.h>
 #include <projectexplorer/session.h>
@@ -356,16 +358,41 @@ void Client::closeDocument(TextEditor::TextDocument *document)
     }
 }
 
+void Client::updateCompletionProvider(TextEditor::TextDocument *document)
+{
+    bool useLanguageServer = m_serverCapabilities.completionProvider().has_value();
+    auto clientCompletionProvider = static_cast<LanguageClientCompletionAssistProvider *>(
+        m_clientProviders.completionAssistProvider.data());
+    if (m_dynamicCapabilities.isRegistered(CompletionRequest::methodName).value_or(false)) {
+        const QJsonValue &options = m_dynamicCapabilities.option(CompletionRequest::methodName);
+        const TextDocumentRegistrationOptions docOptions(options);
+        useLanguageServer = docOptions.filterApplies(document->filePath(),
+                                                     Utils::mimeTypeForName(document->mimeType()));
+
+        const ServerCapabilities::CompletionOptions completionOptions(options);
+        if (completionOptions.isValid(nullptr))
+            clientCompletionProvider->setTriggerCharacters(completionOptions.triggerCharacters());
+    }
+
+    if (document->completionAssistProvider() != clientCompletionProvider) {
+        if (useLanguageServer) {
+            m_resetAssistProvider[document].completionAssistProvider
+                = document->completionAssistProvider();
+            document->setCompletionAssistProvider(clientCompletionProvider);
+        }
+    } else if (!useLanguageServer) {
+        document->setCompletionAssistProvider(
+            m_resetAssistProvider[document].completionAssistProvider);
+    }
+}
+
 void Client::activateDocument(TextEditor::TextDocument *document)
 {
     auto uri = DocumentUri::fromFilePath(document->filePath());
     m_diagnosticManager.showDiagnostics(uri);
     SemanticHighligtingSupport::applyHighlight(document, m_highlights.value(uri), capabilities());
     // only replace the assist provider if the language server support it
-    if (m_serverCapabilities.completionProvider()) {
-        m_resetAssistProvider[document].completionAssistProvider = document->completionAssistProvider();
-        document->setCompletionAssistProvider(m_clientProviders.completionAssistProvider);
-    }
+    updateCompletionProvider(document);
     if (m_serverCapabilities.signatureHelpProvider()) {
         m_resetAssistProvider[document].functionHintProvider = document->functionHintAssistProvider();
         document->setFunctionHintAssistProvider(m_clientProviders.functionHintProvider);
@@ -527,6 +554,11 @@ void Client::documentContentsChanged(TextEditor::TextDocument *document,
 void Client::registerCapabilities(const QList<Registration> &registrations)
 {
     m_dynamicCapabilities.registerCapability(registrations);
+    if (Utils::anyOf(registrations,
+                     Utils::equal(&Registration::method, QString(CompletionRequest::methodName)))) {
+        for (auto document : m_openedDocument.keys())
+            updateCompletionProvider(document);
+    }
 }
 
 void Client::unregisterCapabilities(const QList<Unregistration> &unregistrations)
@@ -1124,7 +1156,7 @@ void Client::handleMethod(const QString &method, const MessageId &id, const ICon
     } else if (method == RegisterCapabilityRequest::methodName) {
         auto params = dynamic_cast<const RegisterCapabilityRequest *>(content)->params().value_or(RegistrationParams());
         if (params.isValid(&error))
-            m_dynamicCapabilities.registerCapability(params.registrations());
+            registerCapabilities(params.registrations());
         else
             logError(params);
     } else if (method == UnregisterCapabilityRequest::methodName) {
@@ -1265,8 +1297,7 @@ void Client::initializeCallback(const InitializeRequest::Response &initResponse)
         completionProvider->setTriggerCharacters(
             m_serverCapabilities.completionProvider()
                 .value_or(ServerCapabilities::CompletionOptions())
-                .triggerCharacters()
-                .value_or(QList<QString>()));
+                .triggerCharacters());
     }
     if (auto functionHintAssistProvider = qobject_cast<FunctionHintAssistProvider *>(
             m_clientProviders.functionHintProvider)) {
diff --git a/src/plugins/languageclient/client.h b/src/plugins/languageclient/client.h
index 9d8d8487ce8..a8c200f9a04 100644
--- a/src/plugins/languageclient/client.h
+++ b/src/plugins/languageclient/client.h
@@ -208,6 +208,8 @@ private:
     void resetAssistProviders(TextEditor::TextDocument *document);
     void sendPostponedDocumentUpdates();
 
+    void updateCompletionProvider(TextEditor::TextDocument *document);
+
     using ContentHandler = std::function<void(const QByteArray &, QTextCodec *, QString &,
                                               LanguageServerProtocol::ResponseHandlers,
                                               LanguageServerProtocol::MethodHandler)>;
diff --git a/src/plugins/languageclient/languageclientcompletionassist.cpp b/src/plugins/languageclient/languageclientcompletionassist.cpp
index 2114257faef..34567c5a690 100644
--- a/src/plugins/languageclient/languageclientcompletionassist.cpp
+++ b/src/plugins/languageclient/languageclientcompletionassist.cpp
@@ -451,10 +451,12 @@ bool LanguageClientCompletionAssistProvider::isActivationCharSequence(const QStr
     });
 }
 
-void LanguageClientCompletionAssistProvider::setTriggerCharacters(QList<QString> triggerChars)
+void LanguageClientCompletionAssistProvider::setTriggerCharacters(
+    const Utils::optional<QList<QString>> triggerChars)
 {
-    m_triggerChars = triggerChars;
-    for (const QString &trigger : triggerChars) {
+    m_activationCharSequenceLength = 0;
+    m_triggerChars = triggerChars.value_or(QList<QString>());
+    for (const QString &trigger : qAsConst(m_triggerChars)) {
         if (trigger.length() > m_activationCharSequenceLength)
             m_activationCharSequenceLength = trigger.length();
     }
diff --git a/src/plugins/languageclient/languageclientcompletionassist.h b/src/plugins/languageclient/languageclientcompletionassist.h
index 828a33ec758..34bf7b209ac 100644
--- a/src/plugins/languageclient/languageclientcompletionassist.h
+++ b/src/plugins/languageclient/languageclientcompletionassist.h
@@ -27,6 +27,8 @@
 
 #include <texteditor/codeassist/completionassistprovider.h>
 
+#include <utils/optional.h>
+
 namespace LanguageClient {
 
 class Client;
@@ -45,7 +47,7 @@ public:
     bool isActivationCharSequence(const QString &sequence) const override;
     bool isContinuationChar(const QChar &) const override { return true; }
 
-    void setTriggerCharacters(QList<QString> triggerChars);
+    void setTriggerCharacters(const Utils::optional<QList<QString>> triggerChars);
 
 private:
     QList<QString> m_triggerChars;