Claude Code's 25,000-token MCP limit bypassed by CJK text, researchers find

Developers testing Claude Code v2.1.273 discovered that its 25,000-token MCP output limit can be exceeded when content consists of CJK (Chinese, Japanese, Korean) characters. The tool's size check operates on character count, not tokens, meaning 24,000 CJK characters — which expand to roughly 49,964 tokens — bypassed the token-based limit entirely. Researchers built a minimal stdio MCP server to systematically probe both the character-based and token-based checks, measuring exactly what content Claude received in context and at what token cost. The Claude Code documentation describes the two limits in separate paragraphs using different units — tokens in one, characters in the next — without specifying the character threshold, which the team says contributed to the ambiguity. The findings highlight a gap between documented behavior and actual enforcement, particularly for non-Latin text that carries a higher token-per-character ratio.
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