tiangolo/fastapi · error · HTTPException

X-Key header invalid

Error message

X-Key header invalid

What it means

Raised (400) by the verify_key dependency on GET /items/. The X-Key header must equal 'fake-super-secret-key'. Unlike verify_token, verify_key returns x_key (a usable dependency value), but the route does not consume it. verify_key runs after verify_token, so the token check must pass first.

Solutions

1. Send X-Key: fake-super-secret-key together with a valid X-Token.
2. Configure both headers in a shared auth helper on the client.
3. Store both expected secrets in one config object to keep them in sync.

Example fix

// before
GET /items/   X-Token: fake-super-secret-token
// after
GET /items/   X-Token: fake-super-secret-token   X-Key: fake-super-secret-key

import httpx
resp = httpx.get('http://localhost:8000/items/', headers={'X-Token': 'fake-super-secret-token', 'X-Key': 'fake-super-secret-key'})

def is_valid_x_key(value: object) -> bool:
    return isinstance(value, str) and value == 'fake-super-secret-key'

When it happens

Trigger: GET /items/ with a correct X-Token but a missing/wrong X-Key header. Because verify_token precedes it, you only reach this line when the token is valid.

Common situations: Clients fix the token error and then hit the key error on the next attempt; or a client sends only one of the two required headers.

Related errors

• X-Key header invalid
• X-Token header invalid
• X-Token header invalid
• X-Token header invalid
• Invalid X-Token header

AI-assisted analysis of tiangolo/fastapi@3e8d1526d8 (2026-08-11). Data as JSON: /api/errors/ef76ae82a3cbe001. Report an issue: GitHub.

Appendix: source

Thrown at docs_src/dependencies/tutorial006_an_py310.py:15

from typing import Annotated

from fastapi import Depends, FastAPI, Header, HTTPException

app = FastAPI()


async def verify_token(x_token: Annotated[str, Header()]):
    if x_token != "fake-super-secret-token":
        raise HTTPException(status_code=400, detail="X-Token header invalid")


async def verify_key(x_key: Annotated[str, Header()]):
    if x_key != "fake-super-secret-key":
        raise HTTPException(status_code=400, detail="X-Key header invalid")
    return x_key


@app.get("/items/", dependencies=[Depends(verify_token), Depends(verify_key)])
async def read_items():
    return [{"item": "Foo"}, {"item": "Bar"}]

View on GitHub (pinned to 3e8d1526d8)