From 9b7d2a9885c0cf7c3d2e23767ed610b4ddaf557f Mon Sep 17 00:00:00 2001
From: Michael Nahkies <michael@nahkies.co.nz>
Date: Sat, 20 Jun 2026 13:20:36 +0100
Subject: [PATCH] fix: adjust headers type for nodejs 26 compatibility

---
 packages/typescript-fetch-runtime/src/types.ts | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/packages/typescript-fetch-runtime/src/types.ts b/packages/typescript-fetch-runtime/src/types.ts
index 88dfaf8f..883ddfcc 100644
--- a/packages/typescript-fetch-runtime/src/types.ts
+++ b/packages/typescript-fetch-runtime/src/types.ts
@@ -34,8 +34,11 @@ export interface AbstractFetchClientConfig {
 }
 
 // fetch HeadersInit type
+export type HeaderValue = string | readonly string[] | undefined
+
 export type HeadersInit =
   | string[][]
   | readonly (readonly [string, string])[]
-  | Record<string, string | ReadonlyArray<string>>
+  | Iterable<readonly [string, string]>
+  | Record<string, HeaderValue>
   | Headers