diff --git a/core/components/com_resources/helpers/html.php b/core/components/com_resources/helpers/html.php
index 0f0900e330e..2c2113c1e45 100644
--- a/core/components/com_resources/helpers/html.php
+++ b/core/components/com_resources/helpers/html.php
@@ -824,7 +824,24 @@ public static function primary_child($option, $resource, $firstChild, $xact='')
 					//} else {
 						$pop = (User::isGuest()) ? '<p class="warning">' . Lang::txt('COM_RESOURCES_TOOL_LOGIN_REQUIRED_TO_RUN') . '</p>' : '';
 						$pop = ($resource->revision =='dev') ? '<p class="warning">' . Lang::txt('COM_RESOURCES_TOOL_VERSION_UNDER_DEVELOPMENT') . '</p>' : $pop;
-						$html .= self::primaryButton('launchtool', $lurl, Lang::txt('COM_RESOURCES_LAUNCH_TOOL'), '', '', '', 0, $pop);
+
+						$existingSession = self::findExistingToolSession($resource);
+						if ($existingSession)
+						{
+							$resumeUrl = Route::url(
+								'index.php?option=com_tools&task=session'
+								. '&app=' . $existingSession->appname
+								. '&sess=' . $existingSession->sessnum
+							);
+							$routedLurl = Route::url($lurl);
+							$newUrl = $routedLurl . (strpos($routedLurl, '?') !== false ? '&newinstance=1' : '?newinstance=1');
+							$html .= self::primaryButton('resumetool', $resumeUrl, Lang::txt('COM_RESOURCES_RESUME_TOOL'), '', Lang::txt('COM_RESOURCES_RESUME_TOOL_TITLE'), '', 0, $pop);
+							$html .= '<p class="launch-new-instance"><a class="btn btn-secondary" href="' . $newUrl . '">' . Lang::txt('COM_RESOURCES_LAUNCH_NEW_INSTANCE') . '</a></p>';
+						}
+						else
+						{
+							$html .= self::primaryButton('launchtool', $lurl, Lang::txt('COM_RESOURCES_LAUNCH_TOOL'), '', '', '', 0, $pop);
+						}
 					//}
 				}
 				else
@@ -1095,6 +1112,71 @@ public static function primary_child($option, $resource, $firstChild, $xact='')
 		return $html;
 	}
 
+	/**
+	 * Look for an existing middleware session for the current user that matches
+	 * this tool resource (any version). Returns the most recently accessed one,
+	 * or null when none exist / middleware is unavailable.
+	 *
+	 * @param   object  $resource  Tool resource
+	 * @return  object|null
+	 */
+	protected static function findExistingToolSession($resource)
+	{
+		if (User::isGuest())
+		{
+			return null;
+		}
+
+		if (!$resource->alias)
+		{
+			return null;
+		}
+
+		// The session appname is the attached revision: alias_r<rev>, or "_dev" for the dev version.
+		$appname = (!isset($resource->revision) || $resource->revision == 'dev')
+			? $resource->alias . '_dev'
+			: $resource->alias . '_r' . $resource->revision;
+
+		try
+		{
+			require_once \Component::path('com_tools') . DS . 'helpers' . DS . 'utils.php';
+
+			$mwdb = \Components\Tools\Helpers\Utils::getMWDBO();
+			if (!$mwdb)
+			{
+				return null;
+			}
+
+			$toolsTables = \Component::path('com_tools') . DS . 'tables';
+			require_once $toolsTables . DS . 'viewperm.php';
+			require_once $toolsTables . DS . 'session.php';
+
+			$ms = new \Components\Tools\Tables\Session($mwdb);
+			$records = $ms->getRecords(User::get('username'), $appname, false);
+		}
+		catch (\Exception $e)
+		{
+			return null;
+		}
+
+		if (!$records)
+		{
+			return null;
+		}
+
+		// Records are already filtered to this appname; pick the most recently accessed.
+		$match = null;
+		foreach ($records as $row)
+		{
+			if (!$match || strtotime($row->accesstime) > strtotime($match->accesstime))
+			{
+				$match = $row;
+			}
+		}
+
+		return $match;
+	}
+
 	/**
 	 * Generate the primary resources button
 	 *
diff --git a/core/components/com_resources/site/assets/css/resources.css b/core/components/com_resources/site/assets/css/resources.css
index 92033b0d517..850ee1405d4 100644
--- a/core/components/com_resources/site/assets/css/resources.css
+++ b/core/components/com_resources/site/assets/css/resources.css
@@ -409,6 +409,14 @@
 		display: block;
 	}
 
+	.launch-new-instance {
+		margin: -1em 0 1.5em 0;
+	}
+	.launch-new-instance .btn {
+		display: block;
+		text-align: center;
+	}
+
 	#primary-document_pop {
 		display: none;
 		position: absolute;
diff --git a/core/components/com_resources/site/language/en-GB/en-GB.com_resources.ini b/core/components/com_resources/site/language/en-GB/en-GB.com_resources.ini
index 3753f58a17d..a046a305a31 100644
--- a/core/components/com_resources/site/language/en-GB/en-GB.com_resources.ini
+++ b/core/components/com_resources/site/language/en-GB/en-GB.com_resources.ini
@@ -172,6 +172,9 @@ COM_RESOURCES_LICENSE="License"
 COM_RESOURCES_AVAILABLE_VERSIONS="Available Versions"
 COM_RESOURCES_TOOL_IS_CLOSED_SOURCE="This tool is closed source."
 COM_RESOURCES_LAUNCH_TOOL="Launch Tool"
+COM_RESOURCES_RESUME_TOOL="Resume Tool"
+COM_RESOURCES_RESUME_TOOL_TITLE="Resume your existing session for this tool"
+COM_RESOURCES_LAUNCH_NEW_INSTANCE="launch a new instance"
 COM_RESOURCES_TOOL_IS_RESTRICTED="WARNING: This tool is currently restricted to authorized members of the hub. If you need access, please submit a ticket to that effect and include the reason for your request."
 COM_RESOURCES_TOOL_VERSION_UNDER_DEVELOPMENT="Warning: This tool version is under development and may not be run until it is installed."
 COM_RESOURCES_TOOL_LOGIN_REQUIRED_TO_RUN="You must login before you can run this tool."