diff --git a/frontend/src/components/date/DatepickerWithRange.vue b/frontend/src/components/date/DatepickerWithRange.vue
index ab867ecb6..8ef4bc604 100644
--- a/frontend/src/components/date/DatepickerWithRange.vue
+++ b/frontend/src/components/date/DatepickerWithRange.vue
@@ -86,7 +86,6 @@
 
 						<Modal
 							:enabled="showHowItWorks"
-							transition-name="fade"
 							:overflow="true"
 							variant="hint-modal"
 							@close="() => showHowItWorks = false"
diff --git a/frontend/src/components/date/DatepickerWithValues.vue b/frontend/src/components/date/DatepickerWithValues.vue
index ae1068b78..c8420dc68 100644
--- a/frontend/src/components/date/DatepickerWithValues.vue
+++ b/frontend/src/components/date/DatepickerWithValues.vue
@@ -64,7 +64,6 @@
 
 						<Modal
 							:enabled="showHowItWorks"
-							transition-name="fade"
 							:overflow="true"
 							variant="hint-modal"
 							@close="() => showHowItWorks = false"
diff --git a/frontend/src/components/input/filter/FilterAutocomplete.ts b/frontend/src/components/input/filter/FilterAutocomplete.ts
index 25da1eb65..a4b0d64fc 100644
--- a/frontend/src/components/input/filter/FilterAutocomplete.ts
+++ b/frontend/src/components/input/filter/FilterAutocomplete.ts
@@ -451,7 +451,10 @@ export default Extension.create<FilterAutocompleteOptions>({
 				popupElement.style.zIndex = '20000'
 				popupElement.id = 'filter-autocomplete-popup'
 				popupElement.appendChild(component.element!)
-				document.body.appendChild(popupElement)
+				// Append to the closest dialog (if inside a modal) so the popup
+				// is not blocked by <dialog> inertness, otherwise fall back to body.
+				const parentDialog = view.dom.closest('dialog')
+				;(parentDialog || document.body).appendChild(popupElement)
 
 				cleanupFloating = autoUpdate(virtualReference, popupElement, updatePosition)
 			}
diff --git a/frontend/src/components/misc/CustomTransition.vue b/frontend/src/components/misc/CustomTransition.vue
index 23f406a20..cb7fc9dc5 100644
--- a/frontend/src/components/misc/CustomTransition.vue
+++ b/frontend/src/components/misc/CustomTransition.vue
@@ -7,7 +7,7 @@
 
 <script setup lang="ts">
 withDefaults(defineProps<{
-	name?: 'fade' | 'flash-background' | 'width' | 'modal'
+	name?: 'fade' | 'flash-background' | 'width'
 }>(), {
 	name: 'fade',
 })
@@ -58,13 +58,4 @@ $flash-background-duration: 750ms;
   inline-size: 0;
 }
 
-.modal-enter,
-.modal-leave-active {
-	opacity: 0;
-}
-
-.modal-enter .modal-container,
-.modal-leave-active .modal-container {
-	transform: scale(0.9);
-}
 </style>
diff --git a/frontend/src/components/misc/Modal.vue b/frontend/src/components/misc/Modal.vue
index f11763339..1d80fce7f 100644
--- a/frontend/src/components/misc/Modal.vue
+++ b/frontend/src/components/misc/Modal.vue
@@ -1,128 +1,159 @@
 <template>
 	<Teleport to="body">
-		<!-- FIXME: transition should not be included in the modal -->
-		<CustomTransition
-			:name="transitionName"
-			appear
+		<dialog
+			v-if="showDialog"
+			ref="dialogRef"
+			class="modal-dialog"
+			:class="[
+				{ 'has-overflow': overflow },
+				variant,
+			]"
+			v-bind="attrs"
+			@cancel.prevent="$emit('close')"
 		>
-			<section
-				v-if="enabled"
-				ref="modal"
-				class="modal-mask"
-				:class="[
-					{ 'has-overflow': overflow },
-					variant,
-				]"
-				v-bind="attrs"
+			<div
+				class="modal-container"
+				@mousedown.self.prevent.stop="$emit('close')"
 			>
-				<div
-					v-shortcut="'Escape'"
-					class="modal-container"
-					@mousedown.self.prevent.stop="$emit('close')"
+				<BaseButton
+					class="close"
+					@click="$emit('close')"
 				>
-					<BaseButton
-						class="close"
-						@click="$emit('close')"
-					>
-						<Icon icon="times" />
-					</BaseButton>
-					<div
-						class="modal-content"
-						:class="{
-							'has-overflow': overflow,
-							'is-wide': wide
-						}"
-					>
-						<slot>
-							<div class="modal-header">
-								<slot name="header" />
-							</div>
-							<div class="content">
-								<slot name="text" />
-							</div>
-							<div class="actions">
-								<XButton
-									variant="tertiary"
-									class="has-text-danger"
-									@click="$emit('close')"
-								>
-									{{ $t('misc.cancel') }}
-								</XButton>
-								<XButton
-									v-cy="'modalPrimary'"
-									variant="primary"
-									:shadow="false"
-									@click="$emit('submit')"
-								>
-									{{ $t('misc.doit') }}
-								</XButton>
-							</div>
-						</slot>
-					</div>
+					<Icon icon="times" />
+				</BaseButton>
+				<div
+					class="modal-content"
+					:class="{
+						'has-overflow': overflow,
+						'is-wide': wide
+					}"
+				>
+					<slot>
+						<div class="modal-header">
+							<slot name="header" />
+						</div>
+						<div class="content">
+							<slot name="text" />
+						</div>
+						<div class="actions">
+							<XButton
+								variant="tertiary"
+								class="has-text-danger"
+								@click="$emit('close')"
+							>
+								{{ $t('misc.cancel') }}
+							</XButton>
+							<XButton
+								v-cy="'modalPrimary'"
+								variant="primary"
+								:shadow="false"
+								@click="$emit('submit')"
+							>
+								{{ $t('misc.doit') }}
+							</XButton>
+						</div>
+					</slot>
 				</div>
-			</section>
-		</CustomTransition>
+			</div>
+		</dialog>
 	</Teleport>
 </template>
 
 <script lang="ts" setup>
-import CustomTransition from '@/components/misc/CustomTransition.vue'
 import BaseButton from '@/components/base/BaseButton.vue'
-import {ref, useAttrs, watchEffect, onBeforeUnmount, watch} from 'vue'
-import {useScrollLock} from '@vueuse/core'
+import {ref, useAttrs, watch, onBeforeUnmount, onMounted, nextTick} from 'vue'
 
 const props = withDefaults(defineProps<{
 	enabled?: boolean,
 	overflow?: boolean,
 	wide?: boolean,
-	transitionName?: 'modal' | 'fade',
 	variant?: 'default' | 'hint-modal' | 'scrolling',
 }>(), {
 	enabled: true,
 	overflow: false,
 	wide: false,
-	transitionName: 'modal',
 	variant: 'default',
 })
 
-const emit = defineEmits(['close', 'submit'])
+defineEmits(['close', 'submit'])
 
 defineOptions({
 	inheritAttrs: false,
 })
 
+const TRANSITION_DURATION = 150
+
 const attrs = useAttrs()
+const dialogRef = ref<HTMLDialogElement | null>(null)
+const previouslyFocused = ref<Element | null>(null)
+const showDialog = ref(false)
+let closeTimer: ReturnType<typeof setTimeout> | null = null
 
-const modal = ref<HTMLElement | null>(null)
-const scrollLock = useScrollLock(modal)
-
-watchEffect(() => {
-	scrollLock.value = props.enabled
-})
-
-function onKeydown(e: KeyboardEvent) {
-	if (e.code === 'Escape') {
-		if (e.isComposing) {
-			return
-		}
- 		emit('close')
+function openDialog() {
+	if (closeTimer) {
+		clearTimeout(closeTimer)
+		closeTimer = null
 	}
+	previouslyFocused.value = document.activeElement
+	showDialog.value = true
+	nextTick(() => {
+		const dialog = dialogRef.value
+		if (dialog) {
+			delete dialog.dataset.closing
+			dialog.showModal()
+		}
+		document.body.style.overflow = 'hidden'
+	})
+}
+
+function closeDialog() {
+	const dialog = dialogRef.value
+	if (!dialog) return
+
+	// Trigger the fade-out while the dialog is still [open] so the opacity
+	// transition plays in browsers that don't support allow-discrete (Firefox).
+	dialog.dataset.closing = ''
+	document.body.style.overflow = ''
+
+	closeTimer = setTimeout(() => {
+		delete dialog.dataset.closing
+		dialog.close()
+		showDialog.value = false
+		closeTimer = null
+		if (previouslyFocused.value instanceof HTMLElement) {
+			previouslyFocused.value.focus()
+		}
+		previouslyFocused.value = null
+	}, TRANSITION_DURATION)
 }
 
 watch(
 	() => props.enabled,
-	(value: boolean) => {
- 		if (value) {
-			window.addEventListener('keydown', onKeydown)
+	(isEnabled) => {
+		if (isEnabled) {
+			openDialog()
 		} else {
-			window.removeEventListener('keydown', onKeydown)
+			closeDialog()
 		}
 	},
-	{immediate: true},
+	{immediate: false},
 )
 
+onMounted(() => {
+	if (props.enabled) {
+		openDialog()
+	}
+})
+
 onBeforeUnmount(() => {
-	window.removeEventListener('keydown', onKeydown)
+	if (closeTimer) {
+		clearTimeout(closeTimer)
+		closeTimer = null
+	}
+	document.body.style.overflow = ''
+	if (previouslyFocused.value instanceof HTMLElement) {
+		previouslyFocused.value.focus()
+	}
 })
 </script>
 
@@ -130,20 +161,49 @@ onBeforeUnmount(() => {
 $modal-margin: 4rem;
 $modal-width: 1024px;
 
-.modal-mask {
+.modal-dialog {
+	// Reset UA dialog styles
+	padding: 0;
+	border: none;
+	background: transparent;
+	color: #ffffff;
+	// Fill viewport
 	position: fixed;
-	z-index: 4000;
-	inset-block-start: 0;
-	inset-inline-start: 0;
+	inset: 0;
 	inline-size: 100%;
 	block-size: 100%;
-	background-color: rgba(0, 0, 0, .8);
-	transition: opacity 150ms ease;
-	color: #ffffff;
+	max-inline-size: 100%;
+	max-block-size: 100%;
+
+	// Transitions
+	opacity: 0;
+	transition: opacity 150ms ease,
+				display 150ms ease allow-discrete;
+
+	&[open]:not([data-closing]) {
+		opacity: 1;
+
+		@starting-style {
+			opacity: 0;
+		}
+	}
+
+	&::backdrop {
+		background-color: rgba(0, 0, 0, 0);
+		transition: background-color 150ms ease,
+					display 150ms ease allow-discrete;
+	}
+
+	&[open]:not([data-closing])::backdrop {
+		background-color: rgba(0, 0, 0, .8);
+
+		@starting-style {
+			background-color: rgba(0, 0, 0, 0);
+		}
+	}
 }
 
 .modal-container {
-	transition: all 150ms ease;
 	position: relative;
 	inline-size: 100%;
 	block-size: 100%;
@@ -151,6 +211,7 @@ $modal-width: 1024px;
 	overflow: auto;
 	padding-block-start: env(safe-area-inset-top);
 	padding-block-end: env(safe-area-inset-bottom);
+
 }
 
 .default .modal-content,
@@ -161,7 +222,7 @@ $modal-width: 1024px;
 	inset-block-start: 50%;
 	inset-inline-start: 50%;
 	transform: translate(-50%, -50%);
-	
+
 	[dir="rtl"] & {
 		transform: translate(50%, -50%);
 	}
@@ -190,7 +251,7 @@ $modal-width: 1024px;
 
 	max-block-size: none; // reset bulma
 	overflow: visible; // reset bulma
-	
+
 	@media not print {
 		max-inline-size: $modal-width;
 	}
@@ -212,8 +273,6 @@ $modal-width: 1024px;
 }
 
 .hint-modal {
-	z-index: 4600;
-
 	:deep(.card-content) {
 		text-align: start;
 
@@ -244,7 +303,7 @@ $modal-width: 1024px;
 }
 
 @media print, screen and (max-width: $tablet) {
-	.modal-mask {
+	.modal-dialog {
 		overflow: visible !important;
 	}
 
@@ -285,7 +344,7 @@ $modal-width: 1024px;
 
 .modal-content :deep(.card .card-header-icon.close) {
 	display: none;
-	
+
 	@media screen and (max-width: $tablet) {
 		display: block;
 	}
@@ -294,12 +353,12 @@ $modal-width: 1024px;
 
 <style lang="scss">
 // Close icon SVG uses currentColor, change the color to keep it visible
-.dark .close {
+.dark .modal-dialog .close {
 	color: var(--grey-900);
 }
 
 @media print, screen and (max-width: $tablet) {
-  body:has(.modal-mask) #app {
+  body:has(dialog[open].modal-dialog) #app {
 	display: none;
   }
 }
diff --git a/frontend/src/components/project/partials/FilterPopup.vue b/frontend/src/components/project/partials/FilterPopup.vue
index 22bd9173c..1ece58801 100644
--- a/frontend/src/components/project/partials/FilterPopup.vue
+++ b/frontend/src/components/project/partials/FilterPopup.vue
@@ -9,7 +9,6 @@
 	</XButton>
 	<Modal
 		:enabled="modalOpen"
-		transition-name="fade"
 		:overflow="true"
 		variant="hint-modal"
 		@close="() => modalOpen = false"
diff --git a/frontend/src/components/quick-actions/QuickAddOverlay.vue b/frontend/src/components/quick-actions/QuickAddOverlay.vue
index 555fc6e10..f6f09a5e9 100644
--- a/frontend/src/components/quick-actions/QuickAddOverlay.vue
+++ b/frontend/src/components/quick-actions/QuickAddOverlay.vue
@@ -42,7 +42,11 @@ watch(() => baseStore.quickActionsActive, (active) => {
 // backdrop, disable scroll, and collapse all extra spacing so the input
 // fills the window edge-to-edge.
 .quick-add-overlay {
-	.modal-mask {
+	dialog.modal-dialog {
+		background: transparent;
+	}
+
+	dialog.modal-dialog::backdrop {
 		background: transparent;
 	}
 
@@ -50,7 +54,7 @@ watch(() => baseStore.quickActionsActive, (active) => {
 		overflow: hidden;
 	}
 
-	.modal-mask > .close {
+	dialog.modal-dialog .close {
 		display: none;
 	}
 }
diff --git a/frontend/src/components/tasks/partials/QuickAddMagic.vue b/frontend/src/components/tasks/partials/QuickAddMagic.vue
index 0915baadd..703f5ff10 100644
--- a/frontend/src/components/tasks/partials/QuickAddMagic.vue
+++ b/frontend/src/components/tasks/partials/QuickAddMagic.vue
@@ -19,7 +19,6 @@
 			</BaseButton>
 			<Modal
 				:enabled="visible"
-				transition-name="fade"
 				:overflow="true"
 				variant="hint-modal"
 				@close="close"
diff --git a/frontend/src/views/About.vue b/frontend/src/views/About.vue
index df6896735..d5745a7c3 100644
--- a/frontend/src/views/About.vue
+++ b/frontend/src/views/About.vue
@@ -1,6 +1,5 @@
 <template>
 	<Modal
-		transition-name="fade"
 		variant="hint-modal"
 		@close="$router.back()"
 	>
diff --git a/frontend/tests/e2e/project/project-view-kanban.spec.ts b/frontend/tests/e2e/project/project-view-kanban.spec.ts
index c480ad986..0d1f37941 100644
--- a/frontend/tests/e2e/project/project-view-kanban.spec.ts
+++ b/frontend/tests/e2e/project/project-view-kanban.spec.ts
@@ -126,8 +126,8 @@ test.describe('Project View Kanban', () => {
 
 		await page.locator('.kanban .bucket .bucket-header .dropdown.options .dropdown-trigger').first().click()
 		await page.locator('.kanban .bucket .bucket-header .dropdown.options .dropdown-menu .dropdown-item').filter({hasText: 'Delete'}).click()
-		await expect(page.locator('.modal-mask .modal-container .modal-content .modal-header')).toContainText('Delete the bucket')
-		await page.locator('.modal-mask .modal-container .modal-content .actions .button').filter({hasText: 'Do it!'}).click()
+		await expect(page.locator('dialog[open] .modal-content .modal-header')).toContainText('Delete the bucket')
+		await page.locator('dialog[open] .modal-content .actions .button').filter({hasText: 'Do it!'}).click()
 
 		await expect(page.locator('.kanban .bucket .title').filter({hasText: buckets[0].title})).not.toBeVisible()
 		await expect(page.locator('.kanban .bucket .title').filter({hasText: buckets[1].title})).toBeVisible()
@@ -208,8 +208,8 @@ test.describe('Project View Kanban', () => {
 		await page.locator('.kanban .bucket .tasks .task').filter({hasText: task.title}).click()
 		await expect(page.locator('.task-view .action-buttons .button').filter({hasText: 'Delete'})).toBeVisible()
 		await page.locator('.task-view .action-buttons .button').filter({hasText: 'Delete'}).click()
-		await expect(page.locator('.modal-mask .modal-container .modal-content .modal-header')).toContainText('Delete this task')
-		await page.locator('.modal-mask .modal-container .modal-content .actions .button').filter({hasText: 'Do it!'}).click()
+		await expect(page.locator('dialog[open] .modal-content .modal-header')).toContainText('Delete this task')
+		await page.locator('dialog[open] .modal-content .actions .button').filter({hasText: 'Do it!'}).click()
 
 		await expect(page.locator('.global-notification')).toContainText('Success')
 
diff --git a/frontend/tests/e2e/project/project.spec.ts b/frontend/tests/e2e/project/project.spec.ts
index 05e86bd43..968f08c47 100644
--- a/frontend/tests/e2e/project/project.spec.ts
+++ b/frontend/tests/e2e/project/project.spec.ts
@@ -103,7 +103,7 @@ test.describe('Projects', () => {
 
 		await page.locator('.project-title-dropdown .project-title-button').click()
 		await page.getByRole('link', {name: /^archive$/i}).click()
-		await expect(page.locator('.modal-content')).toContainText('Archive this project')
+		await expect(page.locator('dialog[open] .modal-content')).toContainText('Archive this project')
 		await page.getByRole('button', {name: /do it/i}).click()
 
 		await expect(page.locator('.global-notification')).toContainText('Success')
diff --git a/frontend/tests/e2e/task/task.spec.ts b/frontend/tests/e2e/task/task.spec.ts
index c367047af..b4344722f 100644
--- a/frontend/tests/e2e/task/task.spec.ts
+++ b/frontend/tests/e2e/task/task.spec.ts
@@ -73,8 +73,13 @@ async function uploadAttachmentAndVerify(page: Page, taskId: number) {
 	const uploadAttachmentPromise = page.waitForResponse(response =>
 		response.url().includes(`/tasks/${taskId}/attachments`) && response.request().method() === 'PUT',
 	)
+	// The "Add Attachments" button triggers openFilePicker() which may open
+	// a native file chooser (especially inside a <dialog>). Handle it via the
+	// filechooser event so it doesn't block the test.
+	const fileChooserPromise = page.waitForEvent('filechooser')
 	await page.locator('.task-view .action-buttons .button').filter({hasText: 'Add Attachments'}).click()
-	await page.locator('input[type=file]#files').setInputFiles('tests/fixtures/image.jpg')
+	const fileChooser = await fileChooserPromise
+	await fileChooser.setFiles('tests/fixtures/image.jpg')
 	await uploadAttachmentPromise
 
 	await expect(page.locator('.attachments .attachments .files button.attachment')).toBeVisible()
@@ -458,8 +463,8 @@ test.describe('Task', () => {
 
 			await expect(page.locator('.task-view .action-buttons .button').filter({hasText: 'Delete'})).toBeVisible()
 			await page.locator('.task-view .action-buttons .button').filter({hasText: 'Delete'}).click()
-			await expect(page.locator('.modal-mask .modal-container .modal-content .modal-header')).toContainText('Delete this task')
-			await page.locator('.modal-mask .modal-container .modal-content .actions .button').filter({hasText: 'Do it!'}).click()
+			await expect(page.locator('dialog[open] .modal-content .modal-header')).toContainText('Delete this task')
+			await page.locator('dialog[open] .modal-content .actions .button').filter({hasText: 'Do it!'}).click()
 
 			await expect(page.locator('.global-notification')).toContainText('Success')
 			await expect(page).toHaveURL(new RegExp(`/projects/${tasks[0].project_id}/`))
@@ -580,7 +585,7 @@ test.describe('Task', () => {
 
 			await addLabelToTaskAndVerify(page, labels[0].title)
 
-			await page.locator('.modal-container > .close').click()
+			await page.locator('dialog[open] .modal-container > .close').click()
 
 			await expect(page.locator('.bucket .task')).toContainText(labels[0].title)
 		})
@@ -973,7 +978,7 @@ test.describe('Task', () => {
 
 			await uploadAttachmentAndVerify(page, tasks[0].id)
 
-			await page.locator('.modal-container > .close').click()
+			await page.locator('dialog[open] .modal-container > .close').click()
 
 			await expect(page.locator('.bucket .task .footer .icon svg.fa-paperclip')).toBeVisible()
 		})