diff --git a/packages/boxel-ui/src/components/header/usage.gts b/packages/boxel-ui/src/components/header/usage.gts
index 66f31997994..dc7e8b8ff5b 100644
--- a/packages/boxel-ui/src/components/header/usage.gts
+++ b/packages/boxel-ui/src/components/header/usage.gts
@@ -102,7 +102,10 @@ export default class HeaderUsage extends Component {
     </FreestyleUsage>
     <style scoped>
       .definition-container {
-        --boxel-header-min-height: 1.56rem;
+        /* 25px exactly. 1.56rem is 24.96px, and a fractional height
+           leaves every engine to round it its own way — which is how
+           the same content lands a pixel apart between browsers. */
+        --boxel-header-min-height: 1.5625rem;
         --boxel-header-padding: var(--boxel-sp-5xs) var(--boxel-sp-xs);
         --boxel-header-background-color: var(--boxel-300);
         --boxel-header-text-color: var(--boxel-dark);
diff --git a/packages/host/app/components/operator-mode/definition-container/base.gts b/packages/host/app/components/operator-mode/definition-container/base.gts
index 2978667f86b..5bfcc1673da 100644
--- a/packages/host/app/components/operator-mode/definition-container/base.gts
+++ b/packages/host/app/components/operator-mode/definition-container/base.gts
@@ -39,7 +39,10 @@ const BaseContainerHeader: TemplateOnlyComponent<BaseContainerHeaderSignature> =
     </Header>
     <style scoped>
       .base-container-header {
-        --boxel-header-min-height: 1.56rem;
+        /* 25px exactly. 1.56rem is 24.96px, and a fractional height
+           leaves every engine to round it its own way — which is how
+           the same content lands a pixel apart between browsers. */
+        --boxel-header-min-height: 1.5625rem;
         --boxel-header-padding: var(--boxel-sp-5xs) var(--boxel-sp-xs);
         --boxel-header-background-color: var(--boxel-300);
         --boxel-header-text-color: var(--boxel-dark);