diff --git a/Gemfile b/Gemfile
index fd6364427..3cddb2774 100644
--- a/Gemfile
+++ b/Gemfile
@@ -123,7 +123,6 @@ gem 'acts_as_list'
 
 # integrations
 gem 'clearbit'
-gem 'graphql-client'
 gem 'net-ldap'
 gem 'slack-notifier'
 gem 'zendesk_api'
diff --git a/Gemfile.lock b/Gemfile.lock
index 03bdd0727..cb397af57 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -218,10 +218,6 @@ GEM
       activesupport (>= 4.2.0)
     gmail_xoauth (0.4.2)
       oauth (>= 0.3.6)
-    graphql (1.11.6)
-    graphql-client (0.16.0)
-      activesupport (>= 3.0)
-      graphql (~> 1.8)
     guard (2.15.0)
       formatador (>= 0.2.4)
       listen (>= 2.7, < 4.0)
@@ -617,7 +613,6 @@ DEPENDENCIES
   faker
   github_changelog_generator
   gmail_xoauth
-  graphql-client
   guard
   guard-livereload
   guard-symlink
diff --git a/app/assets/javascripts/app/controllers/_integration/github.coffee b/app/assets/javascripts/app/controllers/_integration/github.coffee
index e3ace7e5a..284f01945 100644
--- a/app/assets/javascripts/app/controllers/_integration/github.coffee
+++ b/app/assets/javascripts/app/controllers/_integration/github.coffee
@@ -51,8 +51,7 @@ class Form extends App.Controller
           )
           return
 
-        config.schema = data.response
-        App.Setting.set('github_config', config)
+        App.Setting.set('github_config', config, notify: true)
 
       error: (data, status) ->
 
diff --git a/app/assets/javascripts/app/controllers/_integration/gitlab.coffee b/app/assets/javascripts/app/controllers/_integration/gitlab.coffee
index 223905ca0..a0220d37c 100644
--- a/app/assets/javascripts/app/controllers/_integration/gitlab.coffee
+++ b/app/assets/javascripts/app/controllers/_integration/gitlab.coffee
@@ -51,8 +51,7 @@ class Form extends App.Controller
           )
           return
 
-        config.schema = data.response
-        App.Setting.set('gitlab_config', config)
+        App.Setting.set('gitlab_config', config, notify: true)
 
       error: (data, status) ->
 
diff --git a/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_git_issue.coffee b/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_git_issue.coffee
index 9590e4461..19d28e93d 100644
--- a/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_git_issue.coffee
+++ b/app/assets/javascripts/app/controllers/ticket_zoom/sidebar_git_issue.coffee
@@ -4,7 +4,8 @@ class App.SidebarGitIssue extends App.Controller
 
   constructor: ->
     super
-    @issueLinks = []
+    @issueLinks         = []
+    @issueLinkData      = []
     @providerIdentifier = @provider.toLowerCase()
 
   sidebarItem: =>
@@ -13,7 +14,7 @@ class App.SidebarGitIssue extends App.Controller
       name: @providerIdentifier
       badgeCallback: @badgeRender
       sidebarHead: @provider
-      sidebarCallback: @showObjects
+      sidebarCallback: @reloadIssues
       sidebarActions: [
         {
           title:    'Link issue'
@@ -26,8 +27,8 @@ class App.SidebarGitIssue extends App.Controller
 
   shown: ->
     return if !@ticket
-    return if !@ticket.id
-    @showIssues()
+
+    @listIssues()
 
   metaBadge: =>
     counter = ''
@@ -45,6 +46,7 @@ class App.SidebarGitIssue extends App.Controller
     @badgeRenderLocal()
 
   badgeRenderLocal: =>
+    return if !@badgeEl
     @badgeEl.html(App.view('generic/sidebar_tabs_item')(@metaBadge()))
 
   linkIssue: =>
@@ -54,86 +56,141 @@ class App.SidebarGitIssue extends App.Controller
       taskKey: @taskKey
       container: @el.closest('.content')
       callback: (link, ui) =>
-        if @ticket && @ticket.id
-          @saveTicketIssues = true
-        ui.close()
-        @showIssues([link])
+        @getIssues(
+          links: [link]
+          success: (result) =>
+            if !_.contains(@issueLinks, link)
+              @issueLinks.push(result[0].url)
+              @issueLinkData = @issueLinkData.concat(result)
+
+            if @ticket && @ticket.id
+              @saveIssues(
+                ticket_id: @ticket.id
+                links: @issueLinks
+                success: =>
+                  ui.close()
+                  @renderIssues()
+                error: (message = 'Unable to save issue') =>
+                  ui.showAlert(App.i18n.translatePlain(message))
+                  form = ui.el.find('.js-result')
+                  @formEnable(form)
+              )
+            else
+              ui.close()
+              @renderIssues()
+          error: (message = 'Unable to load issues') =>
+            ui.showAlert(App.i18n.translatePlain(message))
+            form = ui.el.find('.js-result')
+            @formEnable(form)
+        )
     )
 
-  showObjects: (el) =>
-    @el = el
+  reloadIssues: (el) =>
+    if el
+      @el = el
 
-    # show placeholder
-    if @ticket && @ticket.preferences && @ticket.preferences[@providerIdentifier] && @ticket.preferences[@providerIdentifier].issue_links
-      @issueLinks = @ticket.preferences[@providerIdentifier].issue_links
-    queryParams = @queryParam()
+    return @renderIssues() if !@ticket
 
-    # TODO: what is 'gitlab_issue_links'
-    if queryParams && queryParams.gitlab_issue_links
-      @issueLinks.push queryParams.gitlab_issue_links
-    @showIssues()
+    ticketLinks = @ticket?.preferences?[@providerIdentifier]?.issue_links || []
+    return @renderIssues() if _.isEqual(@issueLinks, ticketLinks)
 
-  showIssues: (issueLinks) =>
-    if issueLinks
-      @issueLinks = _.uniq(@issueLinks.concat(issueLinks))
+    @issueLinks = ticketLinks
+    @listIssues(true)
 
-    # show placeholder
-    if _.isEmpty(@issueLinks)
-      @html("<div>#{App.i18n.translateInline('No linked issues')}</div>")
+  renderIssues: =>
+    if _.isEmpty(@issueLinkData)
+      @showEmpty()
       return
 
-    # AJAX call to show items
-    @ajax(
-      id:    "#{@providerIdentifier}-#{@taskKey}"
-      type:  'POST'
-      url:   "#{@apiPath}/integration/#{@providerIdentifier}"
-      data: JSON.stringify(links: @issueLinks)
-      success: (data, status, xhr) =>
-        if data.response
-          @showList(data.response)
-          if @saveTicketIssues
-            @saveTicketIssues = false
-            @issueLinks = data.response.map((issue) -> issue.url)
-            @updateTicket(@ticket.id, @issueLinks)
-          return
-        @showError('Unable to load data...')
-
-      error: (xhr, status, error) =>
-
-        # do not close window if request is aborted
-        return if status is 'abort'
-
-        # show error message
-        @showError('Unable to load data...')
-    )
-
-  showList: (issues) =>
     list = $(App.view('ticket_zoom/sidebar_git_issue')(
-      issues: issues
+      issues: @issueLinkData
     ))
     list.delegate('.js-delete', 'click', (e) =>
       e.preventDefault()
       issueLink = $(e.currentTarget).attr 'data-issue-id'
-      @delete(issueLink)
+      @deleteIssue(issueLink)
     )
     @html(list)
     @badgeRenderLocal()
 
+  listIssues: (force = false) =>
+    return @renderIssues() if !force && @fetchFullActive && @fetchFullActive > new Date().getTime() - 5000
+    @fetchFullActive = new Date().getTime()
+
+    return @renderIssues() if _.isEmpty(@issueLinks)
+
+    @getIssues(
+      links: @issueLinks
+      success: (result) =>
+        @issueLinks    = result.map((element) -> element.url)
+        @issueLinkData = result
+        @renderIssues()
+      error: =>
+        @showError(App.i18n.translateInline('Unable to load issues'))
+    )
+
+  getIssues: (params) ->
+    @ajax(
+      id:    "#{@providerIdentifier}-#{@taskKey}"
+      type:  'POST'
+      url:   "#{@apiPath}/integration/#{@providerIdentifier}"
+      data: JSON.stringify(links: params.links)
+      success: (data, status, xhr) ->
+        if data.response
+
+          # some issues redirect to pull requests like
+          # https://github.com/zammad/zammad/issues/1574
+          # in this case throw error
+          return params.error('Unable to load issues') if _.isEmpty(data.response)
+
+          params.success(data.response)
+        else
+          params.error(data.message)
+      error: (xhr, status, error) ->
+        return if status is 'abort'
+
+        params.error()
+    )
+
+  saveIssues: (params) ->
+    App.Ajax.request(
+      id:    "#{@providerIdentifier}-update-#{params.ticket_id}"
+      type:  'POST'
+      url:   "#{@apiPath}/integration/#{@providerIdentifier}_ticket_update"
+      data:  JSON.stringify(ticket_id: params.ticket_id, issue_links: params.links)
+      success: (data, status, xhr) ->
+        params.success(data)
+      error: (xhr, status, details) ->
+        return if status is 'abort'
+
+        params.error()
+    )
+
+  deleteIssue: (link) ->
+    @issueLinks    = _.filter(@issueLinks, (element) -> element isnt link)
+    @issueLinkData = _.filter(@issueLinkData, (element) -> element.url isnt link)
+
+    if @ticket && @ticket.id
+      @saveIssues(
+        ticket_id: @ticket.id
+        links: @issueLinks
+        success: =>
+          @renderIssues()
+        error: (message = 'Unable to save issue') =>
+          @showError(App.i18n.translateInline(message))
+      )
+    else
+      @renderIssues()
+
+  showEmpty: ->
+    @html("<div>#{App.i18n.translateInline('No linked issues')}</div>")
+    @badgeRenderLocal()
+
   showError: (message) =>
     @html App.i18n.translateInline(message)
 
   reload: =>
-    @showIssues()
-
-  delete: (issueLink) =>
-    localLinks = []
-    for localLink in @issueLinks
-      if issueLink.toString() isnt localLink.toString()
-        localLinks.push localLink
-    @issueLinks = localLinks
-    if @ticket && @ticket.id
-      @updateTicket(@ticket.id, @issueLinks)
-    @showIssues()
+    @reloadIssues()
 
   postParams: (args) =>
     return if !args.ticket
@@ -143,25 +200,3 @@ class App.SidebarGitIssue extends App.Controller
     args.ticket.preferences ||= {}
     args.ticket.preferences[@providerIdentifier] ||= {}
     args.ticket.preferences[@providerIdentifier].issue_links = @issueLinks
-
-  updateTicket: (ticket_id, issueLinks) =>
-    App.Ajax.request(
-      id:    "#{@providerIdentifier}-update-#{ticket_id}"
-      type:  'POST'
-      url:   "#{@apiPath}/integration/#{@providerIdentifier}_ticket_update"
-      data:  JSON.stringify(ticket_id: ticket_id, issue_links: issueLinks)
-      success: (data, status, xhr) =>
-        @badgeRenderLocal()
-      error: (xhr, status, details) =>
-
-        # do not close window if request is aborted
-        return if status is 'abort'
-
-        # show error message
-        @log 'errors', details
-        @notify(
-          type:    'error'
-          msg:     App.i18n.translateContent(details.error_human || details.error || 'Unable to update object!')
-          timeout: 6000
-        )
-    )
diff --git a/app/assets/javascripts/app/views/integration/git_issue_link_modal.jst.eco b/app/assets/javascripts/app/views/integration/git_issue_link_modal.jst.eco
index 6d9734423..389ab9cfc 100644
--- a/app/assets/javascripts/app/views/integration/git_issue_link_modal.jst.eco
+++ b/app/assets/javascripts/app/views/integration/git_issue_link_modal.jst.eco
@@ -1,3 +1,3 @@
-<form class="flex horizontal js-result">
+<div class="flex horizontal js-result">
   <input type="text" name="link" value="" autocomplete="off" placeholder="<%= @placeholder %>" class="form-control"/>
-</form>
+</div>
diff --git a/app/controllers/integration/github_controller.rb b/app/controllers/integration/github_controller.rb
index 2cab8e130..ee2f05179 100644
--- a/app/controllers/integration/github_controller.rb
+++ b/app/controllers/integration/github_controller.rb
@@ -5,9 +5,11 @@ class Integration::GitHubController < ApplicationController
 
   def verify
     github = ::GitHub.new(params[:endpoint], params[:api_token])
+
+    github.verify!
+
     render json: {
-      result:   'ok',
-      response: github.schema.to_json,
+      result: 'ok',
     }
   rescue => e
     logger.error e
@@ -21,7 +23,7 @@ class Integration::GitHubController < ApplicationController
   def query
     config = Setting.get('github_config')
 
-    github = ::GitHub.new(config['endpoint'], config['api_token'], schema: config['schema'])
+    github = ::GitHub.new(config['endpoint'], config['api_token'])
 
     render json: {
       result:   'ok',
diff --git a/app/controllers/integration/gitlab_controller.rb b/app/controllers/integration/gitlab_controller.rb
index abc2e8e61..0143054ee 100644
--- a/app/controllers/integration/gitlab_controller.rb
+++ b/app/controllers/integration/gitlab_controller.rb
@@ -5,9 +5,11 @@ class Integration::GitLabController < ApplicationController
 
   def verify
     gitlab = ::GitLab.new(params[:endpoint], params[:api_token])
+
+    gitlab.verify!
+
     render json: {
-      result:   'ok',
-      response: gitlab.schema.to_json,
+      result: 'ok',
     }
   rescue => e
     logger.error e
@@ -21,7 +23,7 @@ class Integration::GitLabController < ApplicationController
   def query
     config = Setting.get('gitlab_config')
 
-    gitlab = ::GitLab.new(config['endpoint'], config['api_token'], schema: config['schema'])
+    gitlab = ::GitLab.new(config['endpoint'], config['api_token'])
 
     render json: {
       result:   'ok',
diff --git a/lib/github.rb b/lib/github.rb
index de35f63c6..f6dc5c74d 100644
--- a/lib/github.rb
+++ b/lib/github.rb
@@ -1,14 +1,14 @@
 # Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/
 
 class GitHub
-  extend Forwardable
-
   attr_reader :client
 
-  def_delegator :client, :schema
+  def initialize(endpoint, api_token)
+    @client = GitHub::HttpClient.new(endpoint, api_token)
+  end
 
-  def initialize(*args, **kargs)
-    @client = GitHub::Client.new(*args, **kargs)
+  def verify!
+    GitHub::Credentials.new(client).verify!
   end
 
   def issues_by_urls(urls)
diff --git a/lib/github/client.rb b/lib/github/client.rb
deleted file mode 100644
index adbcfde6d..000000000
--- a/lib/github/client.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-# Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/
-require 'graphql/client'
-
-class GitHub
-  class Client
-
-    delegate_missing_to :client
-
-    attr_reader :endpoint
-
-    def initialize(endpoint, api_token, schema: nil)
-      @endpoint  = endpoint
-      @api_token = api_token
-      schema(schema) if schema.present?
-    end
-
-    def schema(source = http_client)
-      @schema ||= ::GraphQL::Client.load_schema(source)
-    end
-
-    private
-
-    def http_client
-      @http_client ||= GitHub::HttpClient.new(@endpoint, @api_token)
-    end
-
-    def client
-      @client ||= begin
-        GraphQL::Client.new(
-          schema:  schema,
-          execute: http_client,
-        ).tap do |client|
-          client.allow_dynamic_queries = true
-        end
-      end
-    end
-  end
-end
diff --git a/lib/github/credentials.rb b/lib/github/credentials.rb
new file mode 100644
index 000000000..e21db67d9
--- /dev/null
+++ b/lib/github/credentials.rb
@@ -0,0 +1,28 @@
+# Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/
+class GitHub
+  class Credentials
+
+    QUERY = <<-'GRAPHQL'.freeze
+      query {
+        viewer {
+          login
+        }
+      }
+    GRAPHQL
+
+    attr_reader :client
+
+    def initialize(client)
+      @client = client
+    end
+
+    def verify!
+      response = client.perform(
+        query: GitHub::Credentials::QUERY,
+      )
+      return if response.dig('data', 'viewer', 'login').present?
+
+      raise 'Invalid GitHub GraphQL API token'
+    end
+  end
+end
diff --git a/lib/github/http_client.rb b/lib/github/http_client.rb
index e00c3da54..71a4b5270 100644
--- a/lib/github/http_client.rb
+++ b/lib/github/http_client.rb
@@ -1,22 +1,45 @@
 # Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/
-require 'graphql/client'
-require 'graphql/client/http'
 
 class GitHub
-  class HttpClient < ::GraphQL::Client::HTTP
+  class HttpClient
+    attr_reader :api_token, :endpoint
 
     def initialize(endpoint, api_token)
       raise 'api_token required' if api_token.blank?
       raise 'endpoint required' if endpoint.blank?
 
       @api_token = api_token
-
-      super(endpoint)
+      @endpoint  = endpoint
     end
 
-    def headers(_context)
+    def perform(payload)
+      response = UserAgent.post(
+        endpoint,
+        payload,
+        {
+          headers:      headers,
+          json:         true,
+          open_timeout: 6,
+          read_timeout: 16,
+          log:          {
+            facility: 'GitHub',
+          },
+        },
+      )
+
+      if !response.success?
+        Rails.logger.error response.error
+        raise "Error while requesting GitHub GraphQL API: #{response.error}"
+      end
+
+      response.data
+    end
+
+    private
+
+    def headers
       {
-        Authorization: "bearer #{@api_token}"
+        Authorization: "bearer #{api_token}"
       }
     end
   end
diff --git a/lib/github/linked_issue.rb b/lib/github/linked_issue.rb
index cc3c49163..72b9e6517 100644
--- a/lib/github/linked_issue.rb
+++ b/lib/github/linked_issue.rb
@@ -87,28 +87,28 @@ class GitHub
       @result.dig('milestone', 'title')
     end
 
-    def query
-      @query ||= client.parse GitHub::LinkedIssue::QUERY
-    end
-
     def query_by_url(url)
-      variables = variables(url)
-      return if variables.blank?
+      response = client.perform(
+        query:     GitHub::LinkedIssue::QUERY,
+        variables: variables!(url)
+      )
 
-      response = client.query(query, variables: variables)
-
-      response&.data&.repository&.issue&.to_h&.deep_dup
+      response.dig('data', 'repository', 'issue')
     end
 
-    def variables(url)
-      return if url !~ %r{^https://([^/]+)/([^/]+)/([^/]+)/issues/(\d+)$}
+    def variables!(url)
+      if url !~ %r{^https://([^/]+)/([^/]+)/([^/]+)/issues/(\d+)$}
+        raise Exceptions::UnprocessableEntity, 'Invalid GitHub issue link format'
+      end
 
       host            = $1
       repositor_owner = $2
       repository_name = $3
       id              = $4
 
-      return if client.endpoint.exclude?(host)
+      if client.endpoint.exclude?(host)
+        raise Exceptions::UnprocessableEntity, "Issue link doesn't match configured GitHub endpoint '#{client.endpoint}'"
+      end
 
       {
         repositor_owner: repositor_owner,
diff --git a/lib/gitlab.rb b/lib/gitlab.rb
index 81d96aa05..200a97748 100644
--- a/lib/gitlab.rb
+++ b/lib/gitlab.rb
@@ -1,14 +1,14 @@
 # Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/
 
 class GitLab
-  extend Forwardable
-
   attr_reader :client
 
-  def_delegator :client, :schema
+  def initialize(endpoint, api_token)
+    @client = GitLab::HttpClient.new(endpoint, api_token)
+  end
 
-  def initialize(*args, **kargs)
-    @client = GitLab::Client.new(*args, **kargs)
+  def verify!
+    GitLab::Credentials.new(client).verify!
   end
 
   def issues_by_urls(urls)
diff --git a/lib/gitlab/client.rb b/lib/gitlab/client.rb
deleted file mode 100644
index 7fc371361..000000000
--- a/lib/gitlab/client.rb
+++ /dev/null
@@ -1,38 +0,0 @@
-# Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/
-require 'graphql/client'
-
-class GitLab
-  class Client
-
-    delegate_missing_to :client
-
-    attr_reader :endpoint
-
-    def initialize(endpoint, api_token, schema: nil)
-      @endpoint  = endpoint
-      @api_token = api_token
-      schema(schema) if schema.present?
-    end
-
-    def schema(source = http_client)
-      @schema ||= ::GraphQL::Client.load_schema(source)
-    end
-
-    private
-
-    def http_client
-      @http_client ||= GitLab::HttpClient.new(@endpoint, @api_token)
-    end
-
-    def client
-      @client ||= begin
-        GraphQL::Client.new(
-          schema:  schema,
-          execute: http_client,
-        ).tap do |client|
-          client.allow_dynamic_queries = true
-        end
-      end
-    end
-  end
-end
diff --git a/lib/gitlab/credentials.rb b/lib/gitlab/credentials.rb
new file mode 100644
index 000000000..fa335ecf9
--- /dev/null
+++ b/lib/gitlab/credentials.rb
@@ -0,0 +1,28 @@
+# Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/
+class GitLab
+  class Credentials
+
+    QUERY = <<-'GRAPHQL'.freeze
+      query {
+        currentUser {
+          username
+        }
+      }
+    GRAPHQL
+
+    attr_reader :client
+
+    def initialize(client)
+      @client = client
+    end
+
+    def verify!
+      response = client.perform(
+        query: GitLab::Credentials::QUERY,
+      )
+      return if response.dig('data', 'currentUser', 'username').present?
+
+      raise 'Invalid GitLab GraphQL API token'
+    end
+  end
+end
diff --git a/lib/gitlab/http_client.rb b/lib/gitlab/http_client.rb
index 8a6fc6825..8a97b37d6 100644
--- a/lib/gitlab/http_client.rb
+++ b/lib/gitlab/http_client.rb
@@ -1,20 +1,43 @@
 # Copyright (C) 2012-2016 Zammad Foundation, http://zammad-foundation.org/
-require 'graphql/client'
-require 'graphql/client/http'
 
 class GitLab
-  class HttpClient < ::GraphQL::Client::HTTP
+  class HttpClient
+    attr_reader :api_token, :endpoint
 
     def initialize(endpoint, api_token)
       raise 'api_token required' if api_token.blank?
       raise 'endpoint required' if endpoint.blank?
 
       @api_token = api_token
-
-      super(endpoint)
+      @endpoint = endpoint
     end
 
-    def headers(_context)
+    def perform(payload)
+      response = UserAgent.post(
+        endpoint,
+        payload,
+        {
+          headers:      headers,
+          json:         true,
+          open_timeout: 6,
+          read_timeout: 16,
+          log:          {
+            facility: 'GitLab',
+          },
+        },
+      )
+
+      if !response.success?
+        Rails.logger.error response.error
+        raise "Error while requesting GitLab GraphQL API: #{response.error}"
+      end
+
+      response.data
+    end
+
+    private
+
+    def headers
       {
         "PRIVATE-TOKEN": @api_token
       }
diff --git a/lib/gitlab/linked_issue.rb b/lib/gitlab/linked_issue.rb
index a3762eb47..144f7cfd9 100644
--- a/lib/gitlab/linked_issue.rb
+++ b/lib/gitlab/linked_issue.rb
@@ -84,27 +84,30 @@ class GitLab
       @result.dig('milestone', 'title')
     end
 
-    def query
-      @query ||= client.parse GitLab::LinkedIssue::QUERY
-    end
-
     def query_by_url(url)
       variables = variables(url)
       return if variables.blank?
 
-      response = client.query(query, variables: variables)
+      response = client.perform(
+        query:     GitLab::LinkedIssue::QUERY,
+        variables: variables
+      )
 
-      response&.data&.project&.issue&.to_h&.deep_dup
+      response.dig('data', 'project', 'issue')
     end
 
     def variables(url)
-      return if url !~ %r{^https://([^/]+)/(.*)/-/issues/(\d+)$}
+      if url !~ %r{^https://([^/]+)/(.*)/-/issues/(\d+)$}
+        raise Exceptions::UnprocessableEntity, 'Invalid GitLab issue link format'
+      end
 
       host     = $1
       fullpath = $2
       id       = $3
 
-      return if client.endpoint.exclude?(host)
+      if client.endpoint.exclude?(host)
+        raise Exceptions::UnprocessableEntity, "Issue link doesn't match configured GitLab endpoint '#{client.endpoint}'"
+      end
 
       {
         fullpath: fullpath,
diff --git a/spec/integration/github_spec.rb b/spec/integration/github_spec.rb
index 1b0f049e3..633823add 100644
--- a/spec/integration/github_spec.rb
+++ b/spec/integration/github_spec.rb
@@ -6,13 +6,9 @@ RSpec.describe GitHub, type: :integration do # rubocop:disable RSpec/FilePath
     required_envs.each do |key|
       skip("NOTICE: Missing environment variable #{key} for test! (Please fill up: #{required_envs.join(' && ')})") if ENV[key].blank?
     end
-
-    # request schema only once for performance reasons
-    @cached_schema = described_class.new(ENV['GITHUB_ENDPOINT'], ENV['GITHUB_APITOKEN']).schema
   end
 
-  let(:instance) { described_class.new(ENV['GITHUB_ENDPOINT'], ENV['GITHUB_APITOKEN'], schema: schema) }
-  let(:schema) { @cached_schema } # rubocop:disable RSpec/InstanceVariable
+  let(:instance) { described_class.new(ENV['GITHUB_ENDPOINT'], ENV['GITHUB_APITOKEN']) }
   let(:issue_data) do
     {
       id:         '1575',
@@ -37,12 +33,6 @@ RSpec.describe GitHub, type: :integration do # rubocop:disable RSpec/FilePath
   end
   let(:invalid_issue_url) { 'https://github.com/organization/repository/issues/42' }
 
-  describe '#schema' do
-    it 'returns GraphQL schema' do
-      expect(instance.schema).to respond_to(:to_graphql)
-    end
-  end
-
   describe '#issues_by_urls' do
     let(:result) { instance.issues_by_urls([ issue_url ]) }
 
diff --git a/spec/integration/gitlab_spec.rb b/spec/integration/gitlab_spec.rb
index 6c598cb78..9d37fc64a 100644
--- a/spec/integration/gitlab_spec.rb
+++ b/spec/integration/gitlab_spec.rb
@@ -6,13 +6,9 @@ RSpec.describe GitLab, type: :integration do # rubocop:disable RSpec/FilePath
     required_envs.each do |key|
       skip("NOTICE: Missing environment variable #{key} for test! (Please fill up: #{required_envs.join(' && ')})") if ENV[key].blank?
     end
-
-    # request schema only once for performance reasons
-    @cached_schema = described_class.new(ENV['GITLAB_ENDPOINT'], ENV['GITLAB_APITOKEN']).schema
   end
 
-  let(:instance) { described_class.new(ENV['GITLAB_ENDPOINT'], ENV['GITLAB_APITOKEN'], schema: schema) }
-  let(:schema) { @cached_schema } # rubocop:disable RSpec/InstanceVariable
+  let(:instance) { described_class.new(ENV['GITLAB_ENDPOINT'], ENV['GITLAB_APITOKEN']) }
   let(:issue_data) do
     {
       id:         '1',
@@ -40,13 +36,7 @@ RSpec.describe GitLab, type: :integration do # rubocop:disable RSpec/FilePath
       ],
     }
   end
-  let(:invalid_issue_url) { 'https://git.example.com/group/project/-/issues/1' }
-
-  describe '#schema' do
-    it 'returns GraphQL schema' do
-      expect(instance.schema).to respond_to(:to_graphql)
-    end
-  end
+  let(:invalid_issue_url) { "https://#{URI.parse(ENV['GITLAB_ISSUE_LINK']).host}/group/project/-/issues/1" }
 
   describe '#issues_by_urls' do
     let(:result) { instance.issues_by_urls([ issue_url ]) }
diff --git a/spec/requests/integration/github_spec.rb b/spec/requests/integration/github_spec.rb
index 873134c1a..b7a263e71 100644
--- a/spec/requests/integration/github_spec.rb
+++ b/spec/requests/integration/github_spec.rb
@@ -60,14 +60,13 @@ RSpec.describe 'GitHub', type: :request do
       authenticated_as(admin)
       instance = instance_double('GitHub')
       expect(GitHub).to receive(:new).with(endpoint, token).and_return instance
-      expect(instance).to receive(:schema).and_return(dummy_schema)
+      expect(instance).to receive(:verify!).and_return(true)
 
       post '/api/v1/integration/github/verify', params: params, as: :json
       expect(response).to have_http_status(:ok)
       expect(json_response).to be_a_kind_of(Hash)
       expect(json_response).not_to be_blank
       expect(json_response['result']).to eq('ok')
-      expect(json_response['response']).to eq(dummy_schema.to_json)
     end
 
     it 'does query objects' do
diff --git a/spec/requests/integration/gitlab_spec.rb b/spec/requests/integration/gitlab_spec.rb
index 914e179a6..6fb58d8d4 100644
--- a/spec/requests/integration/gitlab_spec.rb
+++ b/spec/requests/integration/gitlab_spec.rb
@@ -65,14 +65,13 @@ RSpec.describe 'GitLab', type: :request do
       authenticated_as(admin)
       instance = instance_double('GitLab')
       expect(GitLab).to receive(:new).with(endpoint, token).and_return instance
-      expect(instance).to receive(:schema).and_return(dummy_schema)
+      expect(instance).to receive(:verify!).and_return(true)
 
       post '/api/v1/integration/gitlab/verify', params: params, as: :json
       expect(response).to have_http_status(:ok)
       expect(json_response).to be_a_kind_of(Hash)
       expect(json_response).not_to be_blank
       expect(json_response['result']).to eq('ok')
-      expect(json_response['response']).to eq(dummy_schema.to_json)
     end
 
     it 'does query objects' do
diff --git a/spec/system/ticket/create_spec.rb b/spec/system/ticket/create_spec.rb
index 2f6ef8dc3..56da031fe 100644
--- a/spec/system/ticket/create_spec.rb
+++ b/spec/system/ticket/create_spec.rb
@@ -352,9 +352,6 @@ RSpec.describe 'Ticket Create', type: :system do
       required_envs.each do |key|
         skip("NOTICE: Missing environment variable #{key} for test! (Please fill up: #{required_envs.join(' && ')})") if ENV[key].blank?
       end
-
-      # request schema only once for performance reasons
-      @cached_schema = GitLab.new(ENV['GITLAB_ENDPOINT'], ENV['GITLAB_APITOKEN']).schema.to_json
     end
 
     def authenticate
@@ -362,7 +359,6 @@ RSpec.describe 'Ticket Create', type: :system do
       Setting.set('gitlab_config', {
                     api_token: ENV['GITLAB_APITOKEN'],
                     endpoint:  ENV['GITLAB_ENDPOINT'],
-                    schema:    @cached_schema, # rubocop:disable RSpec/InstanceVariable
                   })
       true
     end
@@ -410,9 +406,6 @@ RSpec.describe 'Ticket Create', type: :system do
       required_envs.each do |key|
         skip("NOTICE: Missing environment variable #{key} for test! (Please fill up: #{required_envs.join(' && ')})") if ENV[key].blank?
       end
-
-      # request schema only once for performance reasons
-      @cached_schema = GitHub.new(ENV['GITHUB_ENDPOINT'], ENV['GITHUB_APITOKEN']).schema.to_json
     end
 
     def authenticate
@@ -420,7 +413,6 @@ RSpec.describe 'Ticket Create', type: :system do
       Setting.set('github_config', {
                     api_token: ENV['GITHUB_APITOKEN'],
                     endpoint:  ENV['GITHUB_ENDPOINT'],
-                    schema:    @cached_schema, # rubocop:disable RSpec/InstanceVariable
                   })
       true
     end
diff --git a/spec/system/ticket/zoom_spec.rb b/spec/system/ticket/zoom_spec.rb
index 1739edb71..b94678cd4 100644
--- a/spec/system/ticket/zoom_spec.rb
+++ b/spec/system/ticket/zoom_spec.rb
@@ -1513,9 +1513,6 @@ RSpec.describe 'Ticket zoom', type: :system do
       required_envs.each do |key|
         skip("NOTICE: Missing environment variable #{key} for test! (Please fill up: #{required_envs.join(' && ')})") if ENV[key].blank?
       end
-
-      # request schema only once for performance reasons
-      @cached_schema = GitLab.new(ENV['GITLAB_ENDPOINT'], ENV['GITLAB_APITOKEN']).schema.to_json
     end
 
     def authenticate
@@ -1523,7 +1520,6 @@ RSpec.describe 'Ticket zoom', type: :system do
       Setting.set('gitlab_config', {
                     api_token: ENV['GITLAB_APITOKEN'],
                     endpoint:  ENV['GITLAB_ENDPOINT'],
-                    schema:    @cached_schema, # rubocop:disable RSpec/InstanceVariable
                   })
       true
     end
@@ -1577,9 +1573,6 @@ RSpec.describe 'Ticket zoom', type: :system do
       required_envs.each do |key|
         skip("NOTICE: Missing environment variable #{key} for test! (Please fill up: #{required_envs.join(' && ')})") if ENV[key].blank?
       end
-
-      # request schema only once for performance reasons
-      @cached_schema = GitHub.new(ENV['GITHUB_ENDPOINT'], ENV['GITHUB_APITOKEN']).schema.to_json
     end
 
     def authenticate
@@ -1587,7 +1580,6 @@ RSpec.describe 'Ticket zoom', type: :system do
       Setting.set('github_config', {
                     api_token: ENV['GITHUB_APITOKEN'],
                     endpoint:  ENV['GITHUB_ENDPOINT'],
-                    schema:    @cached_schema, # rubocop:disable RSpec/InstanceVariable
                   })
       true
     end