diff --git a/apps/desktop/src/components/backup/ScheduledDatabaseBackupSettings.vue b/apps/desktop/src/components/backup/ScheduledDatabaseBackupSettings.vue
index 6f9ab533f..143b5f09d 100644
--- a/apps/desktop/src/components/backup/ScheduledDatabaseBackupSettings.vue
+++ b/apps/desktop/src/components/backup/ScheduledDatabaseBackupSettings.vue
@@ -381,7 +381,7 @@ function restoreBackup(run: DatabaseBackupRun, file: DatabaseBackupFile) {
   </div>
 
   <Dialog v-model:open="scheduleDialogOpen">
-    <DialogContent class="max-h-[min(760px,calc(100dvh-32px))] max-w-[min(720px,calc(100vw-32px))] overflow-y-auto">
+    <DialogContent class="max-h-[min(760px,calc(var(--dbx-viewport-height)-32px))] max-w-[min(720px,calc(100vw-32px))] overflow-y-auto">
       <DialogHeader>
         <DialogTitle>{{ editingScheduleId ? t("databaseBackup.editSchedule") : t("databaseBackup.addSchedule") }}</DialogTitle>
       </DialogHeader>
diff --git a/apps/desktop/src/components/connection/ConnectionDialog.vue b/apps/desktop/src/components/connection/ConnectionDialog.vue
index 5939fffed..0432f8aae 100644
--- a/apps/desktop/src/components/connection/ConnectionDialog.vue
+++ b/apps/desktop/src/components/connection/ConnectionDialog.vue
@@ -6377,7 +6377,7 @@ function openExternalUrl(url: string) {
 .connection-dialog-content {
   display: flex;
   flex-direction: column;
-  max-height: calc(100dvh - 2rem);
+  max-height: calc(var(--dbx-viewport-height) - 2rem);
 }
 
 @media (min-width: 640px) {
diff --git a/apps/desktop/src/components/diff/SchemaDiffDialog.vue b/apps/desktop/src/components/diff/SchemaDiffDialog.vue
index 94e7a273a..d01153f17 100644
--- a/apps/desktop/src/components/diff/SchemaDiffDialog.vue
+++ b/apps/desktop/src/components/diff/SchemaDiffDialog.vue
@@ -106,10 +106,10 @@ const isMaximized = ref(false);
 const dialogStyle = computed(() => {
   if (isMaximized.value) {
     return {
-      width: "100vw",
-      height: "100vh",
-      maxWidth: "100vw",
-      maxHeight: "100vh",
+      width: "100%",
+      height: "100%",
+      maxWidth: "100%",
+      maxHeight: "100%",
       borderRadius: "0",
     };
   }
@@ -133,6 +133,13 @@ function toggleMaximize() {
   isMaximized.value = !isMaximized.value;
 }
 
+function handleDialogEscape(event: KeyboardEvent) {
+  if (!showOptionsPanel.value) return;
+
+  event.preventDefault();
+  showOptionsPanel.value = false;
+}
+
 let resizeObserver: ResizeObserver | null = null;
 let saveTimeout: number | null = null;
 
@@ -679,7 +686,7 @@ const targetConnectionInfo = computed(() => {
 
 <template>
   <Dialog v-model:open="open">
-    <DialogContent :class="['min-w-[800px] flex flex-col overflow-hidden', isMaximized ? '' : 'resize']" :style="dialogStyle" @interact-outside.prevent>
+    <DialogContent :class="['flex flex-col overflow-hidden', isMaximized ? 'min-w-0' : 'min-w-[800px] resize']" :portal-class="isMaximized ? 'p-0' : undefined" :style="dialogStyle" @interact-outside.prevent @escape-key-down="handleDialogEscape">
       <Button variant="ghost" size="icon-sm" class="absolute top-2 right-10 z-10" @click="toggleMaximize">
         <Maximize2 v-if="!isMaximized" class="w-4 h-4" />
         <Minimize2 v-else class="w-4 h-4" />
diff --git a/apps/desktop/src/components/diff/__tests__/SchemaDiffDialog.spec.ts b/apps/desktop/src/components/diff/__tests__/SchemaDiffDialog.spec.ts
new file mode 100644
index 000000000..2c6389741
--- /dev/null
+++ b/apps/desktop/src/components/diff/__tests__/SchemaDiffDialog.spec.ts
@@ -0,0 +1,25 @@
+import { readFileSync } from "node:fs";
+import { describe, expect, it } from "vitest";
+
+const dialogSource = readFileSync(new URL("../SchemaDiffDialog.vue", import.meta.url), "utf8");
+
+describe("SchemaDiffDialog fullscreen layout", () => {
+  it("fits the dialog to its portal instead of the viewport width", () => {
+    expect(dialogSource).toContain('width: "100%"');
+    expect(dialogSource).toContain('height: "100%"');
+    expect(dialogSource).not.toContain('width: "100vw"');
+    expect(dialogSource).not.toContain('height: "100vh"');
+  });
+
+  it("removes the normal dialog gutter and minimum width while maximized", () => {
+    expect(dialogSource).toContain(":portal-class=\"isMaximized ? 'p-0' : undefined\"");
+    expect(dialogSource).toContain("isMaximized ? 'min-w-0' : 'min-w-[800px] resize'");
+  });
+
+  it("closes the options panel before allowing Escape to dismiss the dialog", () => {
+    expect(dialogSource).toContain('@escape-key-down="handleDialogEscape"');
+    expect(dialogSource).toContain("if (!showOptionsPanel.value) return;");
+    expect(dialogSource).toContain("event.preventDefault();");
+    expect(dialogSource).toContain("showOptionsPanel.value = false;");
+  });
+});
diff --git a/apps/desktop/src/components/editor/EditorSettingsDialog.vue b/apps/desktop/src/components/editor/EditorSettingsDialog.vue
index 4d65dfcd5..7b9d80cf4 100644
--- a/apps/desktop/src/components/editor/EditorSettingsDialog.vue
+++ b/apps/desktop/src/components/editor/EditorSettingsDialog.vue
@@ -172,7 +172,9 @@ const settingsRootComponent = computed(() => (isSettingsPage.value ? "div" : Dia
 const settingsRootProps = computed(() => (isSettingsPage.value ? {} : { open: props.open === true }));
 const settingsRootClass = computed(() => (isSettingsPage.value ? "h-full min-h-0 overflow-hidden bg-background" : ""));
 const settingsContentComponent = computed(() => (isSettingsPage.value ? "div" : DialogContent));
-const settingsContentClass = computed(() => (isSettingsPage.value ? "flex h-full min-h-0 flex-col gap-4 overflow-hidden bg-background p-4" : "h-[min(660px,calc(100dvh-80px))] !max-w-[min(920px,calc(100vw-32px))] grid-rows-[auto_minmax(0,1fr)] gap-3 p-4 sm:!max-w-[min(920px,calc(100vw-48px))]"));
+const settingsContentClass = computed(() =>
+  isSettingsPage.value ? "flex h-full min-h-0 flex-col gap-4 overflow-hidden bg-background p-4" : "h-[min(660px,calc(var(--dbx-viewport-height)-80px))] !max-w-[min(920px,calc(100vw-32px))] grid-rows-[auto_minmax(0,1fr)] gap-3 p-4 sm:!max-w-[min(920px,calc(100vw-48px))]",
+);
 const settingsTitleComponent = computed(() => (isSettingsPage.value ? "h2" : DialogTitle));
 
 function onSettingsRootOpenChange(value: boolean) {
diff --git a/apps/desktop/src/components/import/TableImportDialog.vue b/apps/desktop/src/components/import/TableImportDialog.vue
index 46b666c1e..88b22e620 100644
--- a/apps/desktop/src/components/import/TableImportDialog.vue
+++ b/apps/desktop/src/components/import/TableImportDialog.vue
@@ -822,7 +822,7 @@ watch(targetMode, (mode) => {
 
 <template>
   <Dialog v-model:open="open">
-    <DialogScrollContent class="flex max-h-[calc(100dvh-6rem)] min-h-0 flex-col overflow-hidden sm:max-w-[980px]" :trap-focus="false" @interact-outside.prevent>
+    <DialogScrollContent class="flex max-h-[calc(var(--dbx-viewport-height)-6rem)] min-h-0 flex-col overflow-hidden sm:max-w-[980px]" :trap-focus="false" @interact-outside.prevent>
       <DialogHeader class="shrink-0 pr-8">
         <DialogTitle class="flex items-center gap-2 text-base">
           <FileUp class="h-4 w-4" />
diff --git a/apps/desktop/src/components/objects/InstallExtensionDialog.vue b/apps/desktop/src/components/objects/InstallExtensionDialog.vue
index d0ae49a2b..049d8c5d7 100644
--- a/apps/desktop/src/components/objects/InstallExtensionDialog.vue
+++ b/apps/desktop/src/components/objects/InstallExtensionDialog.vue
@@ -133,7 +133,7 @@ defineExpose({ show });
 
 <template>
   <Dialog v-model:open="open">
-    <DialogContent class="h-[min(760px,calc(100dvh-2rem))] flex flex-col overflow-hidden sm:max-w-3xl">
+    <DialogContent class="h-[min(760px,calc(var(--dbx-viewport-height)-2rem))] flex flex-col overflow-hidden sm:max-w-3xl">
       <DialogHeader>
         <DialogTitle>{{ t("extension.manageTitle") }}</DialogTitle>
       </DialogHeader>
diff --git a/apps/desktop/src/components/objects/ObjectSourceDialog.vue b/apps/desktop/src/components/objects/ObjectSourceDialog.vue
index 8f726937f..7171ae4d9 100644
--- a/apps/desktop/src/components/objects/ObjectSourceDialog.vue
+++ b/apps/desktop/src/components/objects/ObjectSourceDialog.vue
@@ -182,7 +182,7 @@ function closeDialog() {
 
 <template>
   <Dialog :open="props.open" @update:open="(value) => emit('update:open', value)">
-    <DialogContent class="h-[min(760px,calc(100dvh-2rem))] grid-rows-[auto_minmax(0,1fr)_auto] sm:max-w-[900px]">
+    <DialogContent class="h-[min(760px,calc(var(--dbx-viewport-height)-2rem))] grid-rows-[auto_minmax(0,1fr)_auto] sm:max-w-[900px]">
       <DialogHeader>
         <DialogTitle>{{ title }}</DialogTitle>
       </DialogHeader>
diff --git a/apps/desktop/src/components/search/DatabaseSearchDialog.vue b/apps/desktop/src/components/search/DatabaseSearchDialog.vue
index af28c992c..541435e94 100644
--- a/apps/desktop/src/components/search/DatabaseSearchDialog.vue
+++ b/apps/desktop/src/components/search/DatabaseSearchDialog.vue
@@ -268,7 +268,7 @@ function openResult(item: SearchResultItem) {
 
 <template>
   <Dialog v-model:open="dialogOpen">
-    <DialogScrollContent class="flex max-h-[calc(100dvh-6rem)] min-h-0 max-w-4xl flex-col overflow-hidden gap-0 p-0">
+    <DialogScrollContent class="flex max-h-[calc(var(--dbx-viewport-height)-6rem)] min-h-0 max-w-4xl flex-col overflow-hidden gap-0 p-0">
       <DialogHeader class="shrink-0 border-b px-5 py-4">
         <DialogTitle class="flex items-center gap-2">
           <Search class="h-5 w-5" />
diff --git a/apps/desktop/src/components/search/__tests__/DatabaseSearchDialog.spec.ts b/apps/desktop/src/components/search/__tests__/DatabaseSearchDialog.spec.ts
index b9346bfc7..c4b250320 100644
--- a/apps/desktop/src/components/search/__tests__/DatabaseSearchDialog.spec.ts
+++ b/apps/desktop/src/components/search/__tests__/DatabaseSearchDialog.spec.ts
@@ -5,7 +5,7 @@ const dialogSource = readFileSync(new URL("../DatabaseSearchDialog.vue", import.
 
 describe("DatabaseSearchDialog layout", () => {
   it("keeps the header and footer visible within the dynamic viewport", () => {
-    expect(dialogSource).toContain('class="flex max-h-[calc(100dvh-6rem)] min-h-0 max-w-4xl flex-col overflow-hidden gap-0 p-0"');
+    expect(dialogSource).toContain('class="flex max-h-[calc(var(--dbx-viewport-height)-6rem)] min-h-0 max-w-4xl flex-col overflow-hidden gap-0 p-0"');
     expect(dialogSource).toContain('<DialogHeader class="shrink-0 border-b px-5 py-4">');
     expect(dialogSource).toContain('<DialogFooter class="shrink-0 border-t px-5 py-3">');
   });
diff --git a/apps/desktop/src/components/sql-file/SqlFileExecutionDialog.vue b/apps/desktop/src/components/sql-file/SqlFileExecutionDialog.vue
index b79f7ccdf..bfc646ef3 100644
--- a/apps/desktop/src/components/sql-file/SqlFileExecutionDialog.vue
+++ b/apps/desktop/src/components/sql-file/SqlFileExecutionDialog.vue
@@ -438,7 +438,7 @@ watch(
 
 <template>
   <Dialog :open="open" @update:open="handleOpenChange">
-    <DialogScrollContent class="flex max-h-[calc(100dvh-6rem)] min-h-0 min-w-0 flex-col overflow-hidden sm:max-w-[860px]" :trap-focus="false" @interact-outside.prevent>
+    <DialogScrollContent class="flex max-h-[calc(var(--dbx-viewport-height)-6rem)] min-h-0 min-w-0 flex-col overflow-hidden sm:max-w-[860px]" :trap-focus="false" @interact-outside.prevent>
       <DialogHeader class="shrink-0">
         <DialogTitle class="flex items-center gap-2">
           <FileCode class="w-4 h-4" />
diff --git a/apps/desktop/src/components/ui/dialog/DialogContent.vue b/apps/desktop/src/components/ui/dialog/DialogContent.vue
index 373d25b82..6ae6034d5 100644
--- a/apps/desktop/src/components/ui/dialog/DialogContent.vue
+++ b/apps/desktop/src/components/ui/dialog/DialogContent.vue
@@ -42,7 +42,7 @@ const forwarded = useForwardPropsEmits(delegatedProps, emits);
         v-bind="{ ...$attrs, ...forwarded }"
         :class="
           cn(
-            'bg-popover text-popover-foreground data-open:animate-in data-closed:animate-out data-closed:fade-out-0 data-open:fade-in-0 data-closed:zoom-out-95 data-open:zoom-in-95 relative grid max-h-[calc(100dvh-2rem)] w-full max-w-sm gap-4 overflow-hidden rounded-xl border border-border p-4 text-sm shadow-lg duration-100 outline-none pointer-events-auto',
+            'bg-popover text-popover-foreground data-open:animate-in data-closed:animate-out data-closed:fade-out-0 data-open:fade-in-0 data-closed:zoom-out-95 data-open:zoom-in-95 relative grid max-h-[calc(var(--dbx-viewport-height)-2rem)] w-full max-w-sm gap-4 overflow-hidden rounded-xl border border-border p-4 text-sm shadow-lg duration-100 outline-none pointer-events-auto',
             props.class,
           )
         "
diff --git a/apps/desktop/src/components/ui/dialog/DialogScrollContent.vue b/apps/desktop/src/components/ui/dialog/DialogScrollContent.vue
index a83373348..b094e5466 100644
--- a/apps/desktop/src/components/ui/dialog/DialogScrollContent.vue
+++ b/apps/desktop/src/components/ui/dialog/DialogScrollContent.vue
@@ -26,7 +26,7 @@ const forwarded = useForwardPropsEmits(delegatedProps, emits);
     <div class="fixed inset-0 z-50 grid place-items-center p-4 pointer-events-none">
       <DialogContent
         data-slot="dialog-content"
-        :class="cn('relative z-50 grid w-full max-w-lg my-8 gap-4 border border-border bg-background p-4 shadow-lg duration-200 sm:rounded-lg md:w-full pointer-events-auto', props.class)"
+        :class="cn('relative z-50 grid max-h-[calc(var(--dbx-viewport-height)-6rem)] w-full max-w-lg my-8 gap-4 border border-border bg-background p-4 shadow-lg duration-200 sm:rounded-lg md:w-full pointer-events-auto', props.class)"
         v-bind="{ ...$attrs, ...forwarded }"
         @pointer-down-outside="
           (event) => {
diff --git a/apps/desktop/src/styles/__tests__/legacyWebviewFallback.spec.ts b/apps/desktop/src/styles/__tests__/legacyWebviewFallback.spec.ts
index 5ca13e43c..96a71f4f0 100644
--- a/apps/desktop/src/styles/__tests__/legacyWebviewFallback.spec.ts
+++ b/apps/desktop/src/styles/__tests__/legacyWebviewFallback.spec.ts
@@ -2,6 +2,9 @@ import { readFileSync } from "node:fs";
 import { describe, expect, it } from "vitest";
 
 const globalsCss = readFileSync(new URL("../globals.css", import.meta.url), "utf8");
+const dialogContentSource = readFileSync(new URL("../../components/ui/dialog/DialogContent.vue", import.meta.url), "utf8");
+const dialogScrollContentSource = readFileSync(new URL("../../components/ui/dialog/DialogScrollContent.vue", import.meta.url), "utf8");
+const connectionDialogSource = readFileSync(new URL("../../components/connection/ConnectionDialog.vue", import.meta.url), "utf8");
 
 describe("legacy WebView CSS fallbacks", () => {
   it("scopes component overrides to WebViews without OKLCH support", () => {
@@ -24,4 +27,17 @@ describe("legacy WebView CSS fallbacks", () => {
     expect(tabsNestingDepth).toBeGreaterThan(0);
     expect(nestingDepth).toBe(0);
   });
+
+  it("falls back to the legacy viewport height when dynamic viewport units are unavailable", () => {
+    const fallback = globalsCss.indexOf("--dbx-viewport-height: 100vh;");
+    const supports = globalsCss.indexOf("@supports (height: 100dvh)");
+    const enhanced = globalsCss.indexOf("--dbx-viewport-height: min(100vh, 100dvh);");
+
+    expect(fallback).toBeGreaterThan(-1);
+    expect(supports).toBeGreaterThan(fallback);
+    expect(enhanced).toBeGreaterThan(supports);
+    expect(dialogContentSource).toContain("max-h-[calc(var(--dbx-viewport-height)-2rem)]");
+    expect(dialogScrollContentSource).toContain("max-h-[calc(var(--dbx-viewport-height)-6rem)]");
+    expect(connectionDialogSource).toContain("max-height: calc(var(--dbx-viewport-height) - 2rem);");
+  });
 });
diff --git a/apps/desktop/src/styles/globals.css b/apps/desktop/src/styles/globals.css
index ebb13eaff..70efb85f6 100644
--- a/apps/desktop/src/styles/globals.css
+++ b/apps/desktop/src/styles/globals.css
@@ -120,6 +120,13 @@
   --sidebar-border: rgb(229 229 229);
   --sidebar-ring: rgb(161 161 161);
   --dbx-window-top-border: rgb(0 0 0 / 0.35);
+  --dbx-viewport-height: 100vh;
+}
+
+@supports (height: 100dvh) {
+  :root {
+    --dbx-viewport-height: min(100vh, 100dvh);
+  }
 }
 
 .dark {
diff --git a/packages/app-tests/sqlFileExecutionDialog.test.ts b/packages/app-tests/sqlFileExecutionDialog.test.ts
index 8ae4e6948..7b42135eb 100644
--- a/packages/app-tests/sqlFileExecutionDialog.test.ts
+++ b/packages/app-tests/sqlFileExecutionDialog.test.ts
@@ -17,7 +17,7 @@ test("SQL file execution dialog SFC compiles", () => {
 });
 
 test("SQL file execution dialog keeps actions visible within narrow viewports", () => {
-  assert.match(dialogSource, /DialogScrollContent class="[^"]*max-h-\[calc\(100dvh-6rem\)\][^"]*flex-col[^"]*overflow-hidden/);
+  assert.match(dialogSource, /DialogScrollContent class="[^"]*max-h-\[calc\(var\(--dbx-viewport-height\)-6rem\)\][^"]*flex-col[^"]*overflow-hidden/);
   assert.match(dialogSource, /<DialogHeader class="shrink-0">/);
   assert.match(dialogSource, /class="grid min-h-0 min-w-0 flex-1 gap-4 overflow-y-auto py-3"/);
   assert.match(dialogSource, /class="grid grid-cols-1 gap-3 sm:grid-cols-2"/);