@posthog/ai throws "Class extends value undefined is not a constructor or null" when using OpenAI (Anthropic import issue)`

[ketanip]

Bug description

Please describe.

Using @posthog/ai with OpenAI results in:

TypeError: Class extends value undefined is not a constructor or null
    at Object.<anonymous> (node_modules/@posthog/ai/src/anthropic/index.ts:46:56)

This happens even though I’m not using Anthropic. The error points to PostHogAnthropic extends AnthropicOriginal, but AnthropicOriginal is undefined. It looks like @posthog/ai imports a default from @anthropic-ai/sdk that doesn’t exist or isn’t being resolved properly.

---

How to reproduce

1. Install dependencies:

   npm install openai @posthog/ai posthog-node
   

2. Add the following code:

   import { OpenAI } from '@posthog/ai'
   import { PostHog } from 'posthog-node'
   
   const phClient = new PostHog(
     "POSTHOG_KEY", 
     { host: "https://us.i.posthog.com" }
   );
   
   const openai = new OpenAI({
     apiKey: "POSTHOG_KEY",
     posthog: phClient,
   });
   

3. Run the file with node → crash with TypeError: Class extends value undefined is not a constructor or null.

---

Related sub-libraries

• [ ] All of them
• [ ] posthog-js (web)
• [ ] posthog-js-lite (web lite)
• [ ] posthog-node
• [ ] posthog-react-native
• [ ] @posthog/react
• [x] @posthog/ai
• [ ] @posthog/nextjs-config

---

Additional context

• I am not using Anthropic, but the package fails during import because PostHogAnthropic extends an undefined AnthropicOriginal.
• Installing @anthropic-ai/sdk manually did not fix the issue.
• Seems like the import in @posthog/ai/src/anthropic/index.ts is broken or should be optional when Anthropic isn’t used.

Thank you for your bug report – we love squashing them!

[mistakenot]

I am also getting this same error when using the Google Vertex AI provider with this library.

[ketanip]

From my analysis this issue is because how they are importing anthroipic sdk in the library, that part of code should not trigger but for some reason it is triggering.

[mistakenot]

Odd thing for me is that it works fine when running as a normal nextjs process, I only get this issue when running automated tests with Jest with this config:

import nextJest from 'next/jest.js';

/** @type {import('jest').Config} */
const createJestConfig = nextJest({
  // Provide the path to your Next.js app to load next.config.js and .env files in your test environment
  dir: './',
});

// Add any custom config to be passed to Jest
const config = {
  testEnvironment: 'node',  // Use node environment for server-side tests
  transform: {
    '^.+\\.(js|jsx|ts|tsx)$': ['babel-jest', { presets: ['next/babel'] }],
  },
  moduleNameMapper: {
    // Handle module aliases (if you use them in your project)
    '^@/(.*)$': '<rootDir>/src/$1',
  },
  testPathIgnorePatterns: ['<rootDir>/node_modules/', '<rootDir>/.next/'],
  detectOpenHandles: true,
};

// createJestConfig is exported this way to ensure that next/jest can load the Next.js config which is async
export default createJestConfig(config);

[ketanip]

I'm using this with nest.js (backend framework), while startup it throws this error.

[ketanip]

@posthog-bot Any updates ?

[ketanip]

@Radu-Raicea @carlos-marchal-ph your input will be appreciated a lot on this matter.

[aramvr]

I'm using this for the Vercel gateway; the error throws on the Anthropic client. so changing the import from @posthog/ai to @posthog/ai/vercel fixed it for me.

import { withTracing } from "@posthog/ai/vercel";

[mistakenot]

Good advice, I got around this by changing this:

import { GoogleGenAI } from '@posthog/ai'
import { PostHog } from 'posthog-node'

to this

import { PostHogGoogleGenAI as GoogleGenAI } from '@posthog/ai/gemini'
import { PostHog } from 'posthog-node'

[marandaneto]

@PostHog/team-llm-analytics

[ketanip]

I got this working by importing it from @posthog/ai/openai also use node16 or later in modeuleResolution for typescript . I used "module": "nodenext" intsconfig.json.

import OpenAI from "@posthog/ai/openai";
import { PostHog } from 'posthog-node';

const phClient = new PostHog(
  "POSTHOG_KEY", 
  { host: "https://us.i.posthog.com" }
);

const openai = new OpenAI({
  apiKey: "OPEN_AI_KEY",
  posthog: phClient,
});

[seanghods]

Still broken for me...

[ketanip]

Use names imports like import OpenAI from "@posthog/ai/openai" as per provider you're working, it's a temporary workout until posthog team fixed it.

[seanghods]

Use names imports like import OpenAI from "@posthog/ai/openai" as per provider you're working, it's a temporary workout until posthog team fixed it.

Thanks, I had some issues with that solution. I ended up creating a patch with @dsinghvi's code in the PR above and it is working for me.

[shadyshoha]

Still broken for me too on Anthropic here

[Khosraw]

so we fixing this or nah?

[dannyhellman]

Good advice, I got around this by changing this:

import { GoogleGenAI } from '@posthog/ai' import { PostHog } from 'posthog-node' to this

import { PostHogGoogleGenAI as GoogleGenAI } from '@posthog/ai/gemini' import { PostHog } from 'posthog-node'

I've tried this, but it seems PostHog is not logging the thoughtsToken of gemini. Only the output and input. Can't tell if it's a different bug or related to this workaround.

[yakkomajuri]

I'm having this issue when using the actual Anthropic wrapper.

/app/node_modules/.pnpm/@[email protected]_@[email protected]_@[email protected]_@opentel_3d63026c5d7eeb563f4d68eb3f58318e/node_modules/@posthog/ai/dist/index.cjs:2469
class WrappedMessages extends AnthropicOriginal.Messages {
                                                ^
TypeError: Class extends value undefined is not a constructor or null
    at Object.<anonymous> (/app/node_modules/.pnpm/@[email protected]_@[email protected]_@[email protected]_@opentel_3d63026c5d7eeb563f4d68eb3f58318e/node_modules/@posthog/ai/dist/index.cjs:2469:49)
    at Module._compile (node:internal/modules/cjs/loader:1761:14)
    at Object..js (node:internal/modules/cjs/loader:1893:10)
    at Module.load (node:internal/modules/cjs/loader:1481:32)
    at Module._load (node:internal/modules/cjs/loader:1300:12)
    at TracingChannel.traceSync (node:diagnostics_channel:328:14)
    at wrapModuleLoad (node:internal/modules/cjs/loader:245:24)
    at Module.require (node:internal/modules/cjs/loader:1504:12)
    at require (node:internal/modules/helpers:152:16)
    at Object.<anonymous> (/app/dist/agents/normalizationAgent/normalizationAgent.js:4:14)
Node.js v24.12.0

Versions:

• @anthropic-ai/sdk: ^0.71.2
• @posthog/ai: ^7.3.0