autoreg-skills-max/skills/conol-autoreg/references/fastapi-body-pitfall.md

FastAPI Request Body Pitfall

Symptom

POST/PUT endpoints return null instead of parsed JSON, or FastAPI returns 400/422 with no clear error.

Root Cause

When you write async def endpoint(request: dict):, FastAPI treats request as a query parameter named "request", NOT as a JSON body. The endpoint will:

• Accept requests without error
• Receive request = None (no query param named "request")
• Return null when you try to use it

Fix

from fastapi import FastAPI, HTTPException, Request

# WRONG — request is treated as a query parameter, always None
@app.post("/api/endpoint")
async def bad(request: dict):
    return request  # returns null

# RIGHT — use FastAPI Request + await request.json()
@app.post("/api/endpoint")
async def good(request: Request):
    try:
        body = await request.json()
    except Exception:
        raise HTTPException(400, "Invalid JSON body")
    return body  # returns the actual JSON

Alternative: Pydantic model

from pydantic import BaseModel

class Item(BaseModel):
    email: str
    password: str | None = None

@app.post("/api/endpoint")
async def good(item: Item):
    return {"email": item.email, "password": item.password}

Occurrence

Hit this bug in dashboard_server.py queue_add endpoint. The request: dict signature silently returned null for every POST. Fixed by importing Request and using await request.json().