Thanks for the details — that error means the

SqlAlchemyConnector

block failed Pydantic validation when loading, most commonly because the connection info can’t be parsed into a valid SQLAlchemy URL or the required driver isn’t installed in the runtime. Here’s a quick checklist to resolve it: 1) Verify the block contents - Run:

prefect block inspect sqlalchemy-connector/ai-platform-postgres-connector

Look for

connection_info

. If it’s a URL string, make sure it’s complete and well-formed. For Postgres, valid examples: - Sync (psycopg2):

<postgresql+psycopg2://username:password@host:5432/database>

- Sync (psycopg v3):

<postgresql+psycopg://username:password@host:5432/database>

- Async (asyncpg):

<postgresql+asyncpg://username:password@host:5432/database>

Tips: - Use

postgresql

, not just

postgres

. - Percent-encode special characters in passwords (e.g.,

@

->

%40

). 2) Ensure the driver is installed in the runtime that loads/uses the block - For psycopg2:

pip install psycopg2-binary

- For psycopg v3:

pip install psycopg

- For asyncpg:

pip install asyncpg

Also ensure you have SQLAlchemy available (Prefect 3 + prefect-sqlalchemy):

pip install prefect-sqlalchemy sqlalchemy

If you’re running in a worker container or remote environment, the packages must be installed there too. 3) Recreate or update the block using the current schema Sometimes validation fails if the block was created with an older

prefect-sqlalchemy

version and the schema changed. Recreate it in code to ensure the schema matches your installed package: - Using a URL string:

from prefect_sqlalchemy.database import SqlAlchemyConnector

SqlAlchemyConnector(
    connection_info="<postgresql+psycopg2://username:password@host:5432/database>"
).save("ai-platform-postgres-connector", overwrite=True)

- Using components (avoids string mistakes):

from prefect_sqlalchemy.database import SqlAlchemyConnector
from prefect_sqlalchemy.credentials import ConnectionComponents

SqlAlchemyConnector(
    connection_info=ConnectionComponents(
        driver="postgresql+psycopg2",  # or "postgresql+psycopg", "postgresql+asyncpg"
        host="host",
        port=5432,
        username="username",
        password="password",
        database="database",
    )
).save("ai-platform-postgres-connector", overwrite=True)

4) (Optional) Load without validation to inspect further

from prefect_sqlalchemy.database import SqlAlchemyConnector
c = SqlAlchemyConnector.load("ai-platform-postgres-connector", validate=False)

If the block loads with

validate=False

, try creating a client to test connectivity (this will still fail if the URL/driver is wrong):

from sqlalchemy import text
with c.get_client() as engine:
    with engine.connect() as conn:
        conn.execute(text("SELECT 1"))

If you can share: - The connection string format you used (with secrets redacted) - Whether you created the block in the UI or via code - Your versions of Prefect, prefect-sqlalchemy, SQLAlchemy, and the Postgres driver …I can pinpoint the exact issue quickly. Docs for reference: - prefect-sqlalchemy: prefect-sqlalchemy docs