AI coding agents search in English even for non-English queries, test finds

A developer ran 320 web-search sessions with Claude Code (Opus 5.5) and Codex CLI across five languages. For global topics, 205 of 206 searches were in English and none of the 222 cited pages matched the question's language. For local topics, searches in the local language reached 82% for Claude Code and 50% for Codex.

• 205 of 206 global-topic searches were conducted in English
• 0 of 222 cited pages matched the language of the question
• Local topics: 82% local-language searches for Claude Code, 50% for Codex
• All 320 answers came back in the question's language, hiding source language