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Error monitoring for FastAPI.

With sentry-sdk, your FastAPI app reports exceptions and 5xx responses with stack trace and local variables to Fehlo. Setup is one call before FastAPI().

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As of 24 October 2026, sentry-sdk 2.73.0, FastAPI 0.79 or later. We tested the Python SDK with Fehlo on 19 October 2026.

1. Install the package

Terminal
pip install sentry-sdk

The FastAPI and Starlette integration switches itself on when FastAPI is installed.

2. Start the SDK and test it

Call sentry_sdk.init before you create the app:

main.py
import sentry_sdk
from fastapi import FastAPI

sentry_sdk.init(
    dsn="https://<key>@app.fehlo.de/<project-id>",
    environment="production",
    release="my-api@1.0.0",
)

app = FastAPI()


@app.get("/sentry-debug")
async def trigger_error():
    division_by_zero = 1 / 0

Start the app with uvicorn main:app and open /sentry-debug. The ZeroDivisionError appears in Fehlo with stack trace, local variables and the route.

3. Which responses are reported

The SDK always reports exceptions without a status code, plus responses with status 500 to 599. To see 403 as well, set failed_request_status_codes on both integrations:

main.py
from sentry_sdk.integrations.fastapi import FastApiIntegration
from sentry_sdk.integrations.starlette import StarletteIntegration

sentry_sdk.init(
    dsn="...",
    integrations=[
        StarletteIntegration(failed_request_status_codes={403, *range(500, 600)}),
        FastApiIntegration(failed_request_status_codes={403, *range(500, 600)}),
    ],
)

Requests with OPTIONS and HEAD are left out.

Privacy

Without further options the Python SDK sends no IP addresses, cookies or user data. Don't set data_collection: once it is set, its more permissive defaults apply, and the SDK sends IP addresses, cookies and bodies. Local variables are included; Fehlo filters passwords, tokens and email addresses on the server.

Measure performance

main.py
traces_sample_rate=0.2,

Each measured request is a transaction and counts against your plan's transaction allowance, not against your events.

Questions

Nothing arrives. What should I check?

First the DSN: it has to point at app.fehlo.de. Second, whether your server or browser can reach https://app.fehlo.de (firewall, proxy, ad blocker). Third, whether this month's quota is used up; you get an email when it is. Fourth, whether sampleRate or beforeSend drops events. If only performance data is missing, this month's transactions may be used up.

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