Resend · sdk · fg-0399

Cloudflare Worker deploy fails after upgrading the resend package to 6.9

Build errors resolving stream, buffer, string_decoder or crypto

Verified 2026-10-15 · Confirmed by 0 builders · Trust 50/100

Cause

resend 6.9.0 pulled in mailparser, which imports Node built-ins that the Workers runtime lacks without the compatibility flag. 6.9.2 removed the problem.

Fix

Upgrade to resend 6.9.2 or later. If you must stay on 6.9.0 or 6.9.1, add compatibility_flags = ["nodejs_compat"] to wrangler.toml.

Apply

npm i resend@^6.9.2

Affects: resend (Node SDK) 6.9.0 and 6.9.1 on Cloudflare Workers, fixed in 6.9.2 (2026-02-10)

Sources

https://github.com/resend/resend-node/issues/817

Have your agent know this before it fails

claude mcp add --transport http footgun https://getfootgun.com/api/mcp