Claude Authenticity

This is a self-contained Python script that runs nine weighted checks to detect whether an API endpoint actually serves genuine Claude or just wraps someone else's model. It mirrors the claude-verify project's methodology, looking for signature fields, extended thinking blocks, cache_creation tokens, and identity keywords that real Claude returns but wrappers typically strip or fake. The script also extracts injected system prompts if a provider is overriding Claude's identity. One sharp design choice: it defaults to Anthropic's native API format because OpenAI-compatible endpoints silently drop the telltale fields, causing false negatives. You get a score out of 100 and a verdict: genuine, suspected, or likely fake. Useful when auditing third-party Claude resellers or testing whether your API key points to the real thing.

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GitHub stars: 657
last updated: Jun 9, 2026

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Install

$ npx -y skills add agentscope-ai/openjudge --skill claude-authenticity --agent claude-code

Installs into .claude/skills of the current project.

Files

Claude Authenticity Skill

Verify whether an API endpoint serves genuine Claude and optionally extract any injected system prompt.

No installation required beyond httpx. Copy the code blocks below directly into a single .py file and run — no openjudge, no cookbooks, no other setup.

pip install httpx

The 9 checks (mirrors claude-verify)

#	Check	Weight	Signal
1	Signature 长度	12	`signature` field in response (official API exclusive)
2	身份回答	12	Reply mentions `claude code` / `cli` / `command`
3	Thinking 输出	14	Extended-thinking block present
4	Thinking 身份	8	Thinking text references Claude Code / CLI
5	响应结构	14	`id` + `cache_creation` fields present
6	系统提示词	10	No prompt-injection signals (reverse check)
7	工具支持	12	Reply mentions `bash` / `file` / `read` / `write`
8	多轮对话	10	Identity keywords appear ≥ 2 times
9	Output Config	10	`cache_creation` or `service_tier` present