@zh-npm/claude-authenticity-detector

Verify whether an API endpoint is serving a genuine Anthropic Claude model.

Probes an API endpoint's streaming behavior, thinking capabilities, token usage, and identity signals to detect whether it serves an authentic Claude model or a relay/proxy substituting a different model.

Installation

npm install -g @zh-npm/claude-authenticity-detector

Or run directly with npx:

npx @zh-npm/claude-authenticity-detector --url https://api.anthropic.com --api-key sk-ant-... --model claude-opus-4-6

CLI Usage

claude-authenticity-detector --url https://api.anthropic.com --api-key sk-ant-...

Flags

| Flag | Default | Description | |------|---------|-------------| | --url | https://api.anthropic.com | Base URL of the API endpoint | | --api-key | $ANTHROPIC_API_KEY | Anthropic API key (falls back to env var) | | --model | claude-opus-4-6 | Model identifier to probe | | --timeout | 120000 | Request timeout in milliseconds | | --verbose | false | Print detailed probe events |

Scoring

The detector runs 5 checks, producing a score from 0 to 100:

| Check | Points | What it measures | |-------|--------|------------------| | Knowledge Cutoff | 0 -- 50 | Whether the model's stated knowledge cutoff matches known Claude dates | | SSE Shape | 0 -- 20 | Whether the streaming event sequence matches Anthropic's SSE protocol | | Thinking Block | 0 -- 15 | Presence and structure of extended-thinking content blocks | | Usage Fields | 0 -- 15 | Correct input/output token usage reporting across stream events | | Identity Penalties | -25 -- 0 | Deductions for identity inconsistencies (wrong model name, non-Claude claims) |

Confidence Levels

| Level | Score Range | |-------|-------------| | HIGH | >= 80 | | MEDIUM | 60 -- 79 | | LOW | 35 -- 59 | | VERY_LOW | < 35 |

Exit Codes

| Code | Meaning | |------|---------| | 0 | HIGH or MEDIUM confidence | | 1 | LOW or VERY_LOW confidence | | 2 | Error (network failure, invalid key, timeout, etc.) |

Programmatic Usage

import { runDetection } from '@zh-npm/claude-authenticity-detector';

const { report, error } = await runDetection({
  url: 'https://api.anthropic.com',
  apiKey: 'your-api-key',
  model: 'claude-opus-4-6',
  timeout: 120000,
  verbose: false,
});

console.log(report.totalScore, report.confidence);

License

Apache-2.0