Fix ASYNC230: blocking file I/O in async FastAPI handlers

[YaMachinu]

Problem

Running ruff check on the codebase reveals 8 instances of ASYNC230 — blocking file I/O operations (open()) inside async FastAPI route handlers. The primary offenders are in routes.py and debug_routes.py.

In an async FastAPI/Uvicorn application, synchronous open() calls block the entire event loop while the OS services the I/O request. Under any meaningful load, this will cause latency spikes and request queuing across all concurrent users of the API.

Affected Files

• src/agentevals/routes.py — multiple async handlers using open() directly
• • src/agentevals/debug_routes.py — similar pattern

Fix

Replace blocking open() calls with async equivalents. Two options:

Option A — aiofiles (recommended, minimal diff):

import aiofiles

async def my_handler():
    async with aiofiles.open("path/to/file", "r") as f:
        content = await f.read()

Option B — asyncio.to_thread() (stdlib, no new dependency):

import asyncio

async def my_handler():
    content = await asyncio.to_thread(_read_file_sync, "path/to/file")

Add aiofiles to the project dependencies if choosing Option A.

[krisztianfekete]

Invalid after #37