no-fire-and-forget-task-without-cancellation

Install

Works with Claude Code, Claude apps, Codex, Cursor, Gemini CLI, GitHub Copilot, VS Code, OpenCode, Goose, Windsurf. Read the repository before you give any tool access to your data.

npx agentmarket install skill/stopthatslop-no-fire-and-forget-task-without-cancellation

About

Use cases: backend, writing, productivity

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Permissions

What this skill can do and what it asks for, from its SKILL.md. Checked Oct 25, 2026.

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What's inside

Skill name

no-fire-and-forget-task-without-cancellation

Description

Do not spawn asyncio background tasks with create_task and drop the reference. Keep the task, surface its errors, and cancel it on shutdown. Use only when editing Python asyncio task spawning or FastAPI startup/shutdown hooks. Do not use for thread pools, Celery workers, or sync threads.

License

MIT

Metadata

pack: stopthatslop-python-fastapi-v1 · globs: **/*.py · engine_rule_id: python.asyncio.no-fire-and-forget-task-without-cancellation

Instructions

49 lines in SKILL.md · view on GitHub

# Background tasks need a kept reference and a cancellation path

`asyncio.create_task(...)` whose result is discarded can be garbage collected
mid-flight, and its exceptions vanish. On shutdown nobody cancels it, so the
process hangs or dies mid-write.

## Do

```python
import asyncio

from fastapi import FastAPI

app = FastAPI()
_background: set[asyncio.Task] = set()


def spawn(coro) -> None:
    task = asyncio.create_task(coro)
    _background.add(task)
    task.add_done_callback(_background.discard)


@app.on_event("shutdown")
async def shutdown() -> None:
    for task in _background:
        task.cancel()
    await asyncio.gather(*_background, return_exceptions=True)
```

## Do not

```python
@app.post("/events")
async def record(event: dict) -> dict:
    asyncio.create_task(persist(event))  # reference dropped, GC may kill it
    return {"ok": True}
```

If you only need work after the response, prefer `BackgroundTasks` from
FastAPI — it is awaited as part of the response cycle and needs none of this
plumbing.

## Enforce

This skill is teach-only. No engine detector exists yet; CI must not fail on
it.

Signals

Stars

4

Forks

0

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Last commit (this folder)

Sep 1, 2026 (2 months ago)

Last release

Sep 13, 2026 (1 month ago)

From GitHub (fetched Oct 24, 2026).

Details

License

MIT

Repository

github.com/StopThatSlop/stopthatslop

Website

stopthatslop.com

First seen

Oct 24, 2026

Last checked

Oct 24, 2026

Source

GitHubgithub-graphql