honoでhono/clientを利用したRPCモードでのクライアント通信を実装していたところ、CORS対応にて調べた内容。

hono: CORS設定

https://hono.dev/docs/middleware/builtin/cors

app.use(
	"*",
	cors({
		origin: "http://localhost:3000",
		allowHeaders: [
			"X-Custom-Header",
			"Upgrade-Insecure-Requests",
			"Content-Type",
			"Authorization",
		],
		allowMethods: ["POST", "GET", "OPTIONS"],
		maxAge: 600,
		credentials: true,
	}),
);

その場合のclientではinit: {}にてcredentials設定を行う。

const _client = hc<ApiType>("http://localhost:5001", {
	headers: {
		"Content-Type": "application/json",
	},
	init: {
		credentials: "include",
	},
});
 

https://github.com/orgs/honojs/discussions/2291