From c44489088b81f5c6e7b3c253f7d751bd2939b462 Mon Sep 17 00:00:00 2001
From: Yevhenii <evgeny.kotyrlo@gmail.com>
Date: Wed, 25 Feb 2026 17:44:40 +0200
Subject: [PATCH] fix: support exactOptionalPropertyTypes and narrow duplex
 type

Enable exactOptionalPropertyTypes in tsconfig so emitted .d.ts files
don't expand optional properties with | undefined. Fix two code
patterns in create-fetch that assign possibly-undefined values to
optional properties. Narrow duplex from "full" | "half" to "half"
per WHATWG Fetch spec.
---
 packages/better-fetch/src/create-fetch/index.ts | 8 ++++----
 packages/better-fetch/src/types.ts              | 2 +-
 packages/better-fetch/tsconfig.json             | 1 +
 3 files changed, 6 insertions(+), 5 deletions(-)

diff --git a/packages/better-fetch/src/create-fetch/index.ts b/packages/better-fetch/src/create-fetch/index.ts
index bbf80b3..96bdbde 100644
--- a/packages/better-fetch/src/create-fetch/index.ts
+++ b/packages/better-fetch/src/create-fetch/index.ts
@@ -95,9 +95,9 @@ export const applySchemaPlugin = (config: CreateFetchOption) =>
 					
 					let opts = {
 						...options,
-						method: keySchema.method,
-						output: keySchema.output,
-						headers: validatedHeaders,
+						...(keySchema.method != null ? { method: keySchema.method } : undefined),
+						...(keySchema.output != null ? { output: keySchema.output } : undefined),
+						...(validatedHeaders != null ? { headers: validatedHeaders } : undefined),
 					};
 					
 					if (!options?.disableValidation) {
@@ -122,7 +122,7 @@ export const applySchemaPlugin = (config: CreateFetchOption) =>
 			}
 			return {
 				url,
-				options,
+				...(options != null ? { options } : undefined),
 			};
 		},
 	}) satisfies BetterFetchPlugin;
diff --git a/packages/better-fetch/src/types.ts b/packages/better-fetch/src/types.ts
index 320b027..e4166ea 100644
--- a/packages/better-fetch/src/types.ts
+++ b/packages/better-fetch/src/types.ts
@@ -93,7 +93,7 @@ export type BetterFetchOption<
 			/**
 			 * Duplex mode
 			 */
-			duplex?: "full" | "half";
+			duplex?: "half";
 			/**
 			 * Custom JSON parser
 			 */
diff --git a/packages/better-fetch/tsconfig.json b/packages/better-fetch/tsconfig.json
index 71ea3fd..5fd1e46 100644
--- a/packages/better-fetch/tsconfig.json
+++ b/packages/better-fetch/tsconfig.json
@@ -5,6 +5,7 @@
 		"esModuleInterop": true /* Emit additional JavaScript to ease support for importing CommonJS modules. This enables 'allowSyntheticDefaultImports' for type compatibility. */,
 		"forceConsistentCasingInFileNames": true /* Ensure that casing is correct in imports. */,
 		"strict": true /* Enable all strict type-checking options. */,
+		"exactOptionalPropertyTypes": true,
 		"noImplicitReturns": true /* Enable error reporting for codepaths that do not explicitly return in a function. */,
 		"skipLibCheck": true /* Skip type checking all .d.ts files. */,
 		"noEmit": true,