Pydantic Logfire

Documentation Index

Fetch the complete documentation index at: https://www.truefoundry.com/llms.txt

Use this file to discover all available pages before exploring further.

​

What is Pydantic Logfire?

​

Key Features of Pydantic Logfire

• LLM & AI Observability: Automatically detects GenAI span attributes and renders conversation replay, token usage, and cost data — no custom configuration needed.
• OpenTelemetry Native: Built on the OTLP standard, meaning any OTLP-compatible exporter can send traces and metrics to Logfire without using the Logfire SDK.
• Multi-region Ingestion: Provides dedicated ingestion endpoints for the US and EU regions to meet data residency requirements.

​

Prerequisites

1. TrueFoundry Account: Create a TrueFoundry account and follow the instructions in our Gateway Quick Start Guide.
2. Pydantic Logfire Account: Sign up at logfire.pydantic.dev and create a project to obtain a write token.

​

Understanding the Logfire Endpoint

• Traces: https://logfire-us.pydantic.dev/v1/traces
• Metrics: https://logfire-us.pydantic.dev/v1/metrics

​

Integration Steps

1

Create a Write Token in Logfire

1. Log into logfire.pydantic.dev and open your project.
2. Navigate to Project Settings → Write Tokens.
3. Click Create Write Token, give it a name, and copy the token value immediately — it is shown only once.

Store the write token in a secrets manager. Enter it directly as the Authorization header value in TrueFoundry — the Logfire OTLP endpoint accepts the raw write token without a Bearer prefix.

2

Configure OTEL Export in TrueFoundry

1. Go to AI Gateway → Controls → Settings in the TrueFoundry dashboard.
2. Scroll down to the OTEL Config section and click the edit (✏️) button.

3. Enable the Otel Traces Exporter Configuration toggle and fill in:

Field	Value
Toggle	Enabled
Protocol	HTTP Configuration
Endpoint	https://logfire-us.pydantic.dev/v1/traces
Encoding	Proto
Header Key	Authorization
Header Value	<your-logfire-write-token>

4. Enable the Otel Metrics Exporter Configuration toggle and fill in:

Field	Value
Toggle	Enabled
Protocol	HTTP Configuration
Endpoint	https://logfire-us.pydantic.dev/v1/metrics
Encoding	Proto
Header Key	Authorization
Header Value	<your-logfire-write-token>

5. Click Save to apply the configuration.

If your Logfire project is in the EU region, replace logfire-us.pydantic.dev with logfire-eu.pydantic.dev in both the traces and metrics endpoint fields.

3

Verify the Integration

1. Make a request through the TrueFoundry AI Gateway.
2. Log into logfire.pydantic.dev and open your project.
3. Navigate to the Live view and confirm spans with service.name tfy-llm-gateway are appearing.

4. Open the Dashboards → Usage Overview view to confirm gateway metrics are flowing in.

Logfire automatically recognizes gen_ai.* span attributes emitted by the TrueFoundry gateway and renders them in its LLM panel — showing token usage, model names, and request/response content without any extra configuration.

​

Configuration Reference