Logfire

Common errors

• ModuleNotFoundError: No module named 'opentelemetry'

  cause The 'logfire' library relies on OpenTelemetry components, and this error indicates that the necessary 'opentelemetry-sdk' package or its dependencies are not installed in the environment.
  fix Install the OpenTelemetry SDK: `pip install opentelemetry-sdk` or ensure a fresh `logfire` installation handles all its dependencies correctly.

• ValueError: LOGFIRE_TOKEN environment variable must be provided.

  cause The Logfire SDK requires an authentication token to connect to the Logfire platform, which can be provided via the `LOGFIRE_TOKEN` environment variable or directly in `logfire.configure()`.
  fix Set the `LOGFIRE_TOKEN` environment variable (e.g., `export LOGFIRE_TOKEN='your_token_here'`) or pass the token explicitly when configuring Logfire: `logfire.configure(token='your_token_here')`.

• ModuleNotFoundError: No module named 'pydantic_logfire'

  cause Developers might mistakenly try to import from the deprecated `pydantic-logfire` package instead of the current `logfire` package.
  fix Ensure you have installed the `logfire` package (not `pydantic-logfire`) and update your import statements to `import logfire`.

• ModuleNotFoundError: No module named 'pytest'

  cause In some older versions of `logfire` (e.g., 0.50), `pytest` was an unexpected transitive dependency, particularly if `logfire.testing` was imported indirectly.
  fix Install `pytest` (`pip install pytest`) or upgrade `logfire` to a newer version where this dependency issue may have been resolved, especially if you are not directly using `logfire.testing`.

Warnings

• breaking logfire.configure() must be called before any spans, logs, or instrument_*() calls. Omitting it causes all telemetry to be silently dropped — no error is raised.
  Fix: Call logfire.configure() at application startup, before importing or initializing any instrumented libraries. For FastAPI: call it before app = FastAPI().
• breaking instrument_httpx() parameters changed: capture_request_json_body, capture_request_text_body, capture_request_form_data, and capture_response_json_body were removed and replaced by capture_request_body and capture_response_body.
  Fix: Replace: logfire.instrument_httpx(capture_request_json_body=True) with logfire.instrument_httpx(capture_request_body=True, capture_response_body=True)
• breaking install_auto_tracing() requires explicit modules parameter — there is no default. Calling it without modules raises TypeError.
  Fix: Always specify modules: logfire.install_auto_tracing(modules=['myapp', 'myapp.services'])
• gotcha pydantic-logfire on PyPI is a deprecated stub package that just depends on logfire. Use pip install logfire directly.
  Fix: pip install logfire. Remove pydantic-logfire from requirements. import logfire not from pydantic_logfire import ...
• gotcha Logfire pricing changed January 2026. Free Personal plan now limited to 1 seat and 3 projects. Teams exceeding these limits needed to upgrade by February 1, 2026 or be auto-upgraded.
  Fix: Check current plan at logfire.pydantic.dev. Team plan ($49/mo) for 5 seats/5 projects. Growth plan ($249/mo) for unlimited.
• breaking logfire.configure() raises LogfireConfigError if LOGFIRE_TOKEN is missing or invalid, or `logfire auth` has not been run, preventing cloud export and application startup. It does not silently default to local console output.
  Fix: Set LOGFIRE_TOKEN environment variable in production, or run `logfire auth` to authenticate. Verify export is working: logfire.configure() logs the dashboard URL if the token is valid.

Install

• pip install logfire Core SDK
• pip install logfire[fastapi] With FastAPI auto-instrumentation
• pip install logfire[httpx,requests,sqlalchemy,asyncpg] With common integrations
• pip install pydantic-logfire DEPRECATED stub — installs logfire automatically

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

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