llmwho

Passive LLM endpoint identity and stability instrumentation for Node.js.

npm install llmwho

import { init } from "llmwho";

const handle = init();

Direct Anthropic Messages API calls need no LLMWho-specific wrapper:

import Anthropic from "@anthropic-ai/sdk";
import { init } from "llmwho";

init();
const client = new Anthropic();
await client.messages.create({
  model: "claude-sonnet-4-20250514",
  max_tokens: 64,
  messages: [{ role: "user", content: "Hello" }],
});

One call instruments globalThis.fetch for recognized LLM routes. It writes content-free observations to ~/.llmwho/events.jsonl; it never sends active traffic. Calls are idempotent, streaming responses are not consumed, and handle.shutdown() safely restores only the LLMWho-owned hook.

Send the same observations to a self-hosted Collector without changing request sites:

const handle = init({
  collectorUrl: "http://127.0.0.1:7734",
  collectorToken: "…",
});

The remote queue is bounded, non-blocking, and fail-open. Native and OTLP modes are available; no Collector URL keeps the local JSONL default. Run the Python service with llmwho collector; deployment and security details are in the Collector guide.

The CLI also accepts content-free Claude Code and Codex lifecycle events: llmwho hook claude-code|codex --event EVENT. Project configuration and privacy details are in the agent hook guide.

Run an explicit OpenAI-compatible compatibility canary:

import { probe } from "llmwho";

const report = await probe({
  baseUrl: "https://api.openai.com/v1",
  apiKey: process.env.OPENAI_API_KEY,
  model: "gpt-4o-mini",
});

Run the authoritative Python output-affinity plugin:

import { science } from "llmwho";

const analysis = await science.outputAffinityMatrix({
  reference: ["reference answer"],
  endpoint: ["endpoint answer"],
});
console.log(analysis.evidence.matrix[0][1]);

Science calls discover uv and create a locked, cached Python environment. Package import, npm installation, and init() do not perform setup. Inspect or prepare it with npx llmwho science status|setup; add --offline to prohibit downloads. The symmetric character-trigram distance measures surface style only. It does not prove model identity, distillation, or capability transfer. Full science runtime and output-affinity documentation is available in the repository.

Inspect local history:

npx llmwho summary
npx llmwho dashboard

The package provides ESM and CommonJS entry points plus TypeScript declarations. Version 0.4 records the response body's declared model field only as a provider declaration. It never turns that declaration into model identity or confidence. Identity remains unknown unless an independent calibrated detector supplies evidence. Undocumented model response headers are ignored; the smoke suite measures capability and does not uniquely identify arbitrary model weights. Raw prompts, responses, headers, query strings, and credentials are never stored.

Full documentation, research review, and source: github.com/tcztzy/llmwho.