Logfire

Common errors

Warnings

Install

Install compatibility verified last tested: 2026-05-12

Imports

• logfire.configure
  wrong

  import logfire
  
  # Missing configure() before use — spans not exported:
  logfire.info('This message is not exported')  # silently dropped
  
  # Old pydantic-logfire import (deprecated):
  from pydantic_logfire import configure  # ImportError — use import logfire

  correct

  import logfire
  
  # Must call configure() FIRST — before any spans or instrumentation
  # Reads LOGFIRE_TOKEN env var automatically if set
  logfire.configure()
  
  # Then instrument libraries
  logfire.instrument_fastapi(app)
  logfire.instrument_httpx()
  logfire.instrument_sqlalchemy(engine)
  
  # Structured logging
  logfire.info('User {user_id} logged in', user_id=123)
  
  # Manual spans
  with logfire.span('Processing order {order_id}', order_id=order.id):
      result = process(order)

  logfire.configure() must be called before any logging, spans, or instrumentation. Without it, spans are created but not exported. The LOGFIRE_TOKEN env var is read automatically at configure() time.

Quickstart stale last tested: 2026-04-23

Always call logfire.configure() first. LOGFIRE_TOKEN from env. Free tier: 1 seat, 3 projects.

import logfire
import os

# Set env var: export LOGFIRE_TOKEN='your-token'
# Or pass directly (not recommended for production):
logfire.configure(
    token=os.environ.get('LOGFIRE_TOKEN'),
    service_name='my-service',
    environment='production'
)

# Structured log with attributes
logfire.info('Processing request', user_id=42, endpoint='/api/data')
logfire.warning('Rate limit approaching', limit=100, current=95)
logfire.error('Database error', error_type='ConnectionTimeout', db='postgres')

# Span (traces an operation)
with logfire.span('Fetch user data {user_id}', user_id=42):
    # Code here is traced
    data = fetch_user(42)
    logfire.info('Fetched {record_count} records', record_count=len(data))

# FastAPI integration
from fastapi import FastAPI
app = FastAPI()
logfire.instrument_fastapi(app)  # auto-traces all routes