fix(better-auth): preserve response headers for early before hook returns

packages/better-auth/src/api/to-auth-endpoints.test.ts

@@ -199,6 +199,15 @@ describe("before hook", async () => {
 					return { response: true };
 				},
 			),
+			responseHeaders: createAuthEndpoint(
+				"/response-headers",
+				{
+					method: "POST",
+				},
+				async (c) => {
+					return { response: true };
+				},
+			),
 		};
 
 		const authContext = init({
@@ -207,6 +216,15 @@ describe("before hook", async () => {
 					if (c.path === "/json") {
 						return { before: true };
 					}
+					if (c.path === "/response-headers") {
+						return new Response(JSON.stringify({ before: true }), {
+							status: 201,
+							headers: {
+								"content-type": "application/json",
+								"x-hook": "before",
+							},
+						});
+					}
 					return new Response(JSON.stringify({ before: true }));
 				}),
 			},
@@ -222,6 +240,39 @@ describe("before hook", async () => {
 			const response = await authEndpoints.json();
 			expect(response).toMatchObject({ before: true });
 		});
+
+		it("should not leak request headers into early before responses", async () => {
+			const response = await authEndpoints.responseHeaders({
+				asResponse: true,
+				headers: new Headers({
+					"content-length": "999",
+					"x-request": "leak-me-not",
+				}),
+			});
+
+			expect(response.status).toBe(201);
+			expect(response.headers.get("x-hook")).toBe("before");
+			expect(response.headers.get("x-request")).toBeNull();
+			expect(response.headers.get("content-length")).toBeNull();
+			await expect(response.json()).resolves.toMatchObject({ before: true });
+		});
+
+		it("should return response headers and status for early before responses", async () => {
+			const result = await authEndpoints.responseHeaders({
+				returnHeaders: true,
+				returnStatus: true,
+				headers: new Headers({
+					"content-length": "999",
+					"x-request": "leak-me-not",
+				}),
+			});
+
+			expect(result.status).toBe(201);
+			expect(result.headers.get("x-hook")).toBe("before");
+			expect(result.headers.get("x-request")).toBeNull();
+			expect(result.headers.get("content-length")).toBeNull();
+			expect(result.response).toBeInstanceOf(Response);
+		});
 	});
 });
 

packages/better-auth/src/api/to-auth-endpoints.ts

@@ -160,16 +160,28 @@ export function toAuthEndpoints<const E extends Record<string, Endpoint>>(
 								internalContext = defuReplaceArrays(rest, internalContext);
 							} else if (before) {
 								/* Return before hook response if it's anything other than a context return */
-								return context?.asResponse
-									? toResponse(before, {
-											headers: context?.headers,
-										})
-									: context?.returnHeaders
+								const response = toResponse(before);
+								if (context?.asResponse) {
+									return response;
+								}
+								if (context?.returnHeaders) {
+									return context?.returnStatus
 										? {
-												headers: context?.headers,
+												headers: response.headers,
 												response: before,
+												status: response.status,
 											}
-										: before;
+										: {
+												headers: response.headers,
+												response: before,
+											};
+								}
+								return context?.returnStatus
+									? {
+											response: before,
+											status: response.status,
+										}
+									: before;
 							}
 
 							internalContext.asResponse = false;