diff --git a/README.md b/README.md
index 07d4347..1ecbc97 100644
--- a/README.md
+++ b/README.md
@@ -24,6 +24,7 @@ When defining the script, you can specify one of the following placeholders that
 %i | file id | *142430*
 %a | actor's user id | *bob*
 %o | owner's user id | *alice*
+%r | approval requester's user id (requires the [approval app](https://github.com/nextcloud/approval), only substituted when the flow is triggered by an approval state change; if no requester is known, the command is not executed and a warning is logged) | *alice*
 %n | nextcloud-relative path | *alice/files/Pictures/Wonderland/20180717_192103.jpg*
 %f | locally available file | */tmp/oc_tmp_m6E6OO-.jpg*
 %x | old nextcloud-relative file path (only on *rename* and *copy*) | *alice/files/Workbench/20180717_192103.jpg*
diff --git a/lib/AppInfo/Application.php b/lib/AppInfo/Application.php
index bcd2356..a29f230 100644
--- a/lib/AppInfo/Application.php
+++ b/lib/AppInfo/Application.php
@@ -7,6 +7,8 @@
 
 namespace OCA\WorkflowScript\AppInfo;
 
+use OCA\Approval\Events\ApprovalStateChangedEvent;
+use OCA\WorkflowScript\Listener\ApprovalStateChangedListener;
 use OCA\WorkflowScript\Listener\RegisterFlowOperationsListener;
 use OCP\AppFramework\App;
 use OCP\AppFramework\Bootstrap\IBootContext;
@@ -30,6 +32,8 @@ public function __construct() {
 	#[\Override]
 	public function register(IRegistrationContext $context): void {
 		$context->registerEventListener(RegisterOperationsEvent::class, RegisterFlowOperationsListener::class);
+		// the approval app is optional; if it is absent, its event is simply never emitted
+		$context->registerEventListener(ApprovalStateChangedEvent::class, ApprovalStateChangedListener::class);
 	}
 
 	#[\Override]
diff --git a/lib/Listener/ApprovalStateChangedListener.php b/lib/Listener/ApprovalStateChangedListener.php
new file mode 100644
index 0000000..04ab4ff
--- /dev/null
+++ b/lib/Listener/ApprovalStateChangedListener.php
@@ -0,0 +1,50 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\WorkflowScript\Listener;
+
+use OCA\Approval\Events\ApprovalStateChangedEvent;
+use OCA\WorkflowScript\RequesterContext;
+use OCP\EventDispatcher\Event;
+use OCP\EventDispatcher\IEventListener;
+
+/**
+ * Picks up the requester of approval state changes provided by the
+ * approval app, so the %r placeholder can be substituted when a flow
+ * is triggered by the tag assignment following the state change.
+ *
+ * The event class belongs to the approval app. The registration happens
+ * by class name, so nothing breaks when the approval app is not
+ * installed: the event is then simply never emitted.
+ *
+ * @template-implements IEventListener<Event>
+ * @psalm-api
+ */
+class ApprovalStateChangedListener implements IEventListener {
+	public function __construct(
+		private RequesterContext $requesterContext,
+	) {
+	}
+
+	/**
+	 * @inheritDoc
+	 */
+	#[\Override]
+	public function handle(Event $event): void {
+		if (!$event instanceof ApprovalStateChangedEvent) {
+			return;
+		}
+
+		$requesterId = $event->getRequesterUserId();
+		if ($requesterId === null || $requesterId === '') {
+			return;
+		}
+
+		$this->requesterContext->setRequester($event->getFileId(), $requesterId);
+	}
+}
diff --git a/lib/Operation.php b/lib/Operation.php
index 81f8957..54506a1 100644
--- a/lib/Operation.php
+++ b/lib/Operation.php
@@ -46,6 +46,7 @@ public function __construct(
 		private IRootFolder $rootFolder,
 		private LoggerInterface $logger,
 		private IURLGenerator $urlGenerator,
+		private RequesterContext $requesterContext,
 	) {
 	}
 
@@ -211,6 +212,20 @@ protected function buildCommand(string $template, Node $node, string $event, arr
 			$command = str_replace('%o', escapeshellarg($userID), $command);
 		}
 
+		if (strpos($command, '%r')) {
+			// filled by ApprovalStateChangedListener when the flow was
+			// triggered by an approval state change of the approval app
+			$requesterID = null;
+			try {
+				$requesterID = $this->requesterContext->getRequester($node->getId());
+			} catch (InvalidPathException|NotFoundException) {
+			}
+			if ($requesterID === null) {
+				throw new PlaceholderNotSubstituted('r');
+			}
+			$command = str_replace('%r', escapeshellarg($requesterID), $command);
+		}
+
 		if (strpos($command, '%x')) {
 			if (!isset($extra['oldFilePath'])) {
 				$extra['oldFilePath'] = '';
diff --git a/lib/RequesterContext.php b/lib/RequesterContext.php
new file mode 100644
index 0000000..dd366c9
--- /dev/null
+++ b/lib/RequesterContext.php
@@ -0,0 +1,31 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\WorkflowScript;
+
+/**
+ * Request-scoped storage for the approval requester of files.
+ *
+ * The approval app (when installed) emits an ApprovalStateChangedEvent
+ * carrying the requester right before it (un)assigns its system tags.
+ * The workflow engine reacts to the tag change synchronously within the
+ * same request, so the requester is picked up here when substituting
+ * the %r placeholder while building the command.
+ */
+class RequesterContext {
+	/** @var array<int, string> */
+	private array $requesters = [];
+
+	public function setRequester(int $fileId, string $requesterId): void {
+		$this->requesters[$fileId] = $requesterId;
+	}
+
+	public function getRequester(int $fileId): ?string {
+		return $this->requesters[$fileId] ?? null;
+	}
+}
diff --git a/psalm.xml b/psalm.xml
index c178bf5..d0be197 100644
--- a/psalm.xml
+++ b/psalm.xml
@@ -18,5 +18,6 @@
 	</extraFiles>
 	<stubs>
 		<file name="tests/stubs/oc_hooks_emitter.php" />
+		<file name="tests/stubs/oca_approval_events_approvalstatechangedevent.php" />
 	</stubs>
 </psalm>
diff --git a/tests/stubs/oca_approval_events_approvalstatechangedevent.php b/tests/stubs/oca_approval_events_approvalstatechangedevent.php
new file mode 100644
index 0000000..07f8604
--- /dev/null
+++ b/tests/stubs/oca_approval_events_approvalstatechangedevent.php
@@ -0,0 +1,46 @@
+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2026 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+
+namespace OCA\Approval\Events {
+	/**
+	 * Stub of the event emitted by the approval app (since its version
+	 * shipping OCA\Approval\Events\ApprovalStateChangedEvent). The approval
+	 * app is an optional integration, so its classes are not available to
+	 * the autoloader; this stub only exists for static analysis.
+	 */
+	class ApprovalStateChangedEvent extends \OCP\EventDispatcher\Event {
+		public function __construct(
+			private int $fileId,
+			private int $ruleId,
+			private int $newState,
+			private ?string $actorUserId,
+			private ?string $requesterUserId,
+		) {
+		}
+
+		public function getFileId(): int {
+			return $this->fileId;
+		}
+
+		public function getRuleId(): int {
+			return $this->ruleId;
+		}
+
+		public function getNewState(): int {
+			return $this->newState;
+		}
+
+		public function getActorUserId(): ?string {
+			return $this->actorUserId;
+		}
+
+		public function getRequesterUserId(): ?string {
+			return $this->requesterUserId;
+		}
+	}
+}