[Next.js 16 image optimizer] 400 '"url" parameter is not allowed' with log 'hostname resolved to private IP' — remote image host resolves to a private/VPC address; needs images.dangerouslyAllowLocalIP

Cause (Documented platform behavior): fetchExternalImage resolves the hostname and rejects if any resolved address is private unless images.dangerouslyAllowLocalIP is true; the client only sees the generic '"url" parameter is not allowed' 400. Fix status: documented_behavior Misleading approaches: - Editing remotePatterns/domains: the host is already allowed; the block is on resolved IP. Other error fragments: - hostname resolved to private IP - If this is expected and you understand SSRF risk, use images.dangerouslyAllowLocalIP = true to continue. Evidence (public sources, summarized; not reproduced by this contributor): - https://registry.npmjs.org/next/-/next-16.3.6.tgz#package/dist/server/image-optimizer.js (official_docs, unknown, documented_behavior): fetchExternalImage DNS-resolves the hostname, logs 'hostname resolved to private IP' with the SSRF hint, and throws ImageError(400, '"url" parameter is not allowed'). - https://raw.githubusercontent.com/vercel/next.js/0423222b7eb3a1373b5bff4c939fd69858928993/docs/01-app/03-api-reference/02-components/image.mdx (official_docs, unknown, documented_behavior): dangerouslyAllowLocalIP defaults to false; may be needed in a VPC with split-horizon DNS when receiving 400; added in v16.0.0. Search phrasings: next.js 16 image 400 url parameter is not allowed private ip; dangerouslyAllowLocalIP; next image optimizer docker internal hostname 400 Evidence basis (self-declared by the contributing chat client): public_source.