AwaitRequired with sqlite+aiolibsql in SQLAlchemy 2.0 — DBAPI sync masked as async?

[swaggyd1]

Summary

When using create_async_engine("sqlite+aiolibsql:///...") from SQLAlchemy 2.0, every awaited operation raises AwaitRequired even with poolclass=StaticPool or NullPool explicitly set. The dialect sqlite.aiolibsql (registered by sqlalchemy-libsql) advertises async support, but the underlying DBAPI (libsql-experimental) appears to be sync internally — so the dialect's async claim is either false or requires an async-specific DBAPI package that is not published.

This makes sqlalchemy-libsql unusable as a drop-in replacement for aiosqlite in SQLAlchemy 2.0 async stacks.

Versions

• Python 3.12
• SQLAlchemy 2.0.49
• alembic 1.18.4
• sqlalchemy-libsql 0.2.0 (entry-points: sqlite.libsql, sqlite.aiolibsql)
• libsql-experimental 0.0.55 (transitive)
• Linux (WSL2 Ubuntu 22.04)

Minimal reproduction

import asyncio
from sqlalchemy.ext.asyncio import create_async_engine
from sqlalchemy.pool import StaticPool
from sqlalchemy import text

async def main():
    engine = create_async_engine(
        "sqlite+aiolibsql:///:memory:",
        poolclass=StaticPool,
    )
    async with engine.connect() as conn:
        await conn.execute(text("SELECT 1"))

asyncio.run(main())

Result: AwaitRequired raised on await conn.execute(...).

Companion observations

• The sibling dialect sqlite+libsql is rejected by create_async_engine with "The asyncio extension requires an async driver" — confirms it is sync, as expected.
• On Windows native (Python 3.12), libsql-experimental==0.0.55 has no cp312-win-amd64 wheel and the sdist build fails on MAX_PATH=260 in the uv cache path during CMake/MSBuild — separate platform issue, not the focus here.

Expected behavior

Either:

• sqlite+aiolibsql works as a true async dialect with a corresponding async DBAPI, or
• the dialect is removed / clearly documented as not yet functional, with a tracking issue for the async DBAPI work.

Context

Filed while evaluating libsql as a drop-in for aiosqlite in a SQLAlchemy 2.0 async project. Decision documented in https://github.com/swaggyd1/trampo/blob/master/docs/decisions/0003-spike-libsql-swap.md (ADR-0003 outcome). Stayed on aiosqlite until the async path is functional. Happy to test patches.