Chapter 150 · LLM Analytics Setup
Subchapter 150.29
references/perplexity.mdMarkdown7 KBView on GitHub
Required
Setting up analytics starts with installing the PostHog SDK for your language. LLM analytics works best with our Python and Node SDKs.
PostHog AI
pip install posthognpm install @posthog/ai posthog-node2
Required
Install the OpenAI SDK. The PostHog SDK instruments your LLM calls by wrapping the OpenAI client. The PostHog SDK does not proxy your calls.
PostHog AI
pip install openainpm install openai3
Required
We call Perplexity through the OpenAI client and generate a response. We’ll use PostHog’s OpenAI provider to capture all the details of the call. Initialize PostHog with your PostHog project token and host from your project settings (opens in a new tab), then pass the PostHog client along with the Perplexity config (the base URL and API key) to our OpenAI wrapper.
PostHog AI
from posthog.ai.openai import OpenAI
from posthog import Posthog
posthog = Posthog(
"<ph_project_token>",
host="https://us.i.posthog.com"
)
client = OpenAI(
base_url="https://api.perplexity.ai",
api_key="<perplexity_api_key>",
posthog_client=posthog
)import { OpenAI } from '@posthog/ai'
import { PostHog } from 'posthog-node'
const phClient = new PostHog(
'<ph_project_token>',
{ host: 'https://us.i.posthog.com' }
);
const openai = new OpenAI({
baseURL: 'https://api.perplexity.ai',
apiKey: '<perplexity_api_key>'
Note: This also works with the
AsyncOpenAIclient.
Proxy note
These SDKs do not proxy your calls. They only fire off an async call to PostHog in the background to send the data. You can also use LLM analytics with other SDKs or our API, but you will need to capture the data in the right format. See the schema in the manual capture section (opens in a new tab) for more details.
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Required
Now, when you call Perplexity with the OpenAI SDK, PostHog automatically captures an $ai_generation event. You can also capture or modify additional properties with the distinct ID, trace ID, properties, groups, and privacy mode parameters.
PostHog AI
response = client.chat.completions.create(
model="sonar",
messages=[
{"role": "user", "content": "Tell me a fun fact about hedgehogs"}
],
posthog_distinct_id="user_123", # optional
posthog_trace_id="trace_123", # optional
posthog_properties={"conversation_id": "abc123", "paid": True}, # optional
posthog_groups={"company": "company_id_in_your_db"}, # optional
posthog_privacy_mode=False # optional
)
print(response.choices[0].message.content)const completion = await openai.chat.completions.create({
model: "sonar",
messages: [{ role: "user", content: "Tell me a fun fact about hedgehogs" }],
posthogDistinctId: "user_123", // optional
posthogTraceId: "trace_123", // optional
posthogProperties: { conversation_id: "abc123", paid: true }, // optional
Notes:
- We also support the old
chat.completionsAPI.- This works with responses where
stream=True.- If you want to capture LLM events anonymously, don’t pass a distinct ID to the request.
See our docs on anonymous vs identified events (opens in a new tab) to learn more.
You can expect captured $ai_generation events to have the following properties:
| Property | Description |
|---|---|
| $ai_model | The specific model, like gpt-5-mini or claude-4-sonnet |
| $ai_latency | The latency of the LLM call in seconds |
| $ai_time_to_first_token | Time to first token in seconds (streaming only) |
| $ai_tools | Tools and functions available to the LLM |
| $ai_input | List of messages sent to the LLM |
| $ai_input_tokens | The number of tokens in the input (often found in response.usage) |
| $ai_output_choices | List of response choices from the LLM |
| $ai_output_tokens | The number of tokens in the output (often found in response.usage) |
| $ai_total_cost_usd | The total cost in USD (input + output) |
| […] (opens in a new tab) | See full list (opens in a new tab) of properties |
Recommended
Confirm LLM events are being sent to PostHog
Let’s make sure LLM events are being captured and sent to PostHog. Under LLM analytics, you should see rows of data appear in the Traces and Generations tabs.


5
Recommended
Now that you’re capturing AI conversations, continue with the resources below to learn what else LLM Analytics enables within the PostHog platform.
| Resource | Description |
|---|---|
| Basics (opens in a new tab) | Learn the basics of how LLM calls become events in PostHog. |
| Generations (opens in a new tab) | Read about the $ai_generation event and its properties. |
| Traces (opens in a new tab) | Explore the trace hierarchy and how to use it to debug LLM calls. |
| Spans (opens in a new tab) | Review spans and their role in representing individual operations. |
| Anaylze LLM performance (opens in a new tab) | Learn how to create dashboards to analyze LLM performance. |
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