Dspy

2

Install DSPy and LiteLLM

Required

Install DSPy and LiteLLM. DSPy uses LiteLLM natively for provider access, and PostHog integrates with LiteLLM’s callback system.

pip install dspy litellm

3

Configure PostHog with LiteLLM

Required

Set your PostHog project token and host as environment variables, then configure LiteLLM to use PostHog as a callback handler. You can find your project token in your project settings (opens in a new tab).

import os
import dspy
import litellm
# Set PostHog environment variables
os.environ["POSTHOG_API_KEY"] = "<ph_project_token>"
os.environ["POSTHOG_API_URL"] = "https://us.i.posthog.com"
# Enable PostHog callbacks in LiteLLM
litellm.success_callback = ["posthog"]
litellm.failure_callback = ["posthog"]
# Configure DSPy to use an LLM
lm = dspy.LM("openai/gpt-5-mini", api_key="your_openai_api_key")
dspy.configure(lm=lm)

How this works

DSPy uses LiteLLM under the hood for LLM provider access. By configuring PostHog as a LiteLLM callback, all LLM calls made through DSPy are automatically captured as $ai_generation events.

4

Run DSPy modules

Required

Use DSPy as normal. PostHog automatically captures an $ai_generation event for each LLM call made through LiteLLM.

# Define a simple signature
class QA(dspy.Signature):
    """Answer the question."""
    question: str = dspy.InputField()
    answer: str = dspy.OutputField()
# Create and run a module
predictor = dspy.Predict(QA)
result = predictor(
    question="What is a fun fact about hedgehogs?"
)
print(result.answer)

You can expect captured $ai_generation events to have the following properties:

Verify traces and generations

Recommended

Confirm LLM events are being sent to PostHog

Let’s make sure LLM events are being captured and sent to PostHog. Under AI Observability, you should see rows of data appear in the Traces and Generations tabs.

Check for LLM events in PostHog (opens in a new tab)

5

Next steps

Recommended

Now that you’re capturing AI conversations, continue with the resources below to learn what else AI Observability enables within the PostHog platform.