From a6d24841b864665078514db0fb24c3004acf01ec Mon Sep 17 00:00:00 2001
From: Mariam <mariamsulakian@gmail.com>
Date: Sun, 17 May 2026 19:01:27 -0700
Subject: [PATCH] fix mergeStyles argument type recursion

---
 ...-merge-styles-9f0f4ab7-7a99-4d0e-9d25-22c0e7f7c314.json | 7 +++++++
 packages/merge-styles/src/mergeStyles.ts                   | 5 ++---
 2 files changed, 9 insertions(+), 3 deletions(-)
 create mode 100644 change/@fluentui-merge-styles-9f0f4ab7-7a99-4d0e-9d25-22c0e7f7c314.json

diff --git a/change/@fluentui-merge-styles-9f0f4ab7-7a99-4d0e-9d25-22c0e7f7c314.json b/change/@fluentui-merge-styles-9f0f4ab7-7a99-4d0e-9d25-22c0e7f7c314.json
new file mode 100644
index 0000000000000..0bad2185ca099
--- /dev/null
+++ b/change/@fluentui-merge-styles-9f0f4ab7-7a99-4d0e-9d25-22c0e7f7c314.json
@@ -0,0 +1,7 @@
+{
+  "type": "patch",
+  "comment": "fix: simplify mergeStyles argument type to avoid excessive type instantiation",
+  "packageName": "@fluentui/merge-styles",
+  "email": "mariamsulakian@gmail.com",
+  "dependentChangeType": "patch"
+}
diff --git a/packages/merge-styles/src/mergeStyles.ts b/packages/merge-styles/src/mergeStyles.ts
index 5d13a93f0828c..fbbc72ce77f5a 100644
--- a/packages/merge-styles/src/mergeStyles.ts
+++ b/packages/merge-styles/src/mergeStyles.ts
@@ -1,13 +1,12 @@
 import { extractStyleParts } from './extractStyleParts';
-import { IStyle, IStyleBaseArray } from './IStyle';
+import { IStyle } from './IStyle';
 import { IStyleOptions } from './IStyleOptions';
 import { isShadowConfig, ShadowConfig } from './shadowConfig';
 import { getStyleOptions } from './StyleOptionsState';
 import { Stylesheet } from './Stylesheet';
 import { styleToClassName } from './styleToClassName';
 
-type Missing = false | null | undefined;
-type StyleArg = IStyle | IStyleBaseArray | Missing;
+type StyleArg = IStyle;
 type StyleArgWithShadow = StyleArg | ShadowConfig;
 
 export function mergeStyles(...args: StyleArg[]): string;