bdclient constructor throws under Bun runtime: 'dns is not a function'

[jimmyhoran]

Summary

Calling new bdclient(...) throws synchronously under the Bun runtime with TypeError: dns is not a function. The SDK's Transport constructor calls interceptors.dns() from undici (dist/esm/core/transport.mjs:45), but Bun's bundled undici polyfill exposes only redirect, retry, and dump. Bun substitutes its own undici for the undici import regardless of what's installed in node_modules, so the userland undici@^7.16.0 dependency does not help. Underlying Bun gap: oven-sh/bun#19748.

Environment

• @brightdata/sdk@1.1.0
• Bun 1.3.11
• macOS arm64
• Also reproducible via @mastra/brightdata@0.2.0, which calls new bdclient(...) inside its tool factories.

Repro

// repro.mjs
import { bdclient } from "@brightdata/sdk";
new bdclient({ apiKey: "any-string" });
console.log("OK — constructor returned");

$ bun run repro.mjs
TypeError: dns is not a function. (In 'dns()', 'dns' is undefined)
    at new Transport (.../@brightdata/sdk/dist/esm/core/transport.mjs:45:20)
    at new bdclient   (.../@brightdata/sdk/dist/esm/client.mjs:82:26)

$ node repro.mjs
OK — constructor returned

Diagnostic

// undici-check.mjs
import * as u from "undici";
console.log("interceptors:", Object.keys(u.interceptors ?? {}));

# Bun
interceptors: [ 'redirect', 'retry', 'dump' ]   // dns missing

# Node (real undici 7.16+)
interceptors: [ 'redirect', 'responseError', 'retry', 'dump', 'dns', 'cache', 'decompress', 'deduplicate' ]

Suggested fixes (any one would unblock callers on Bun)

1. Guard the interceptor chain. In Transport constructor, only compose dns() when interceptors.dns is a function. When it's absent (Bun), compose retry() alone. DNS resolution falls back to the platform default, which is acceptable for most callers.
2. Drop the interceptors.dns() dependency. Use Node's built-in dns module (or skip custom DNS handling entirely), removing the runtime requirement on undici's dns interceptor.
3. Document Node-only support. Add a Bun-incompatibility note to the README and tighten the engines field (currently node >=20.0.0 with no Bun caveat) so users discover the limitation before installing.