tool invoke error: Instance <Account at 0x7677bc952000> is not bound to a Session; attribute refresh operation cannot proceed (Background on this error at: https://sqlalche.me/e/20/bhk3)

[wangyucha]

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1. Is this request related to a challenge you're experiencing? Tell me about your story.

When I call the local workflow in the studio's agent and chatflow, this error occurs. However, it doesn't appear when a workflow calls another workflow. How can I resolve this issue?
“tool invoke error: Instance <Account at 0x7677bc952000> is not bound to a Session; attribute refresh operation cannot proceed (Background on this error at: https://sqlalche.me/e/20/bhk3)”

2. Additional context or comments

No response

[dosubot[bot]]

Hi @wangyucha! I'm Dosu and I’m helping the dify team.

This error happens because the Account object is being accessed outside of an active SQLAlchemy session—usually when agent-invoked tools or chatflows pass ORM objects across async boundaries or after the session is closed. Direct workflow-to-workflow calls keep objects session-bound, but agent/tool invocation often serializes/deserializes data, so only IDs should be passed and ORM objects must be re-fetched inside a fresh session context.

How to fix:
Always pass the Account ID (not the object itself) between workflow nodes, agents, and tools, and then re-query the Account inside a session where you need it:

from sqlalchemy.orm import Session
with Session(db.engine) as session:
    account = session.query(Account).get(account_id)
    # use account safely here

If you must use an ORM object after the session is closed, re-attach it with db.session.merge(account) before accessing its attributes. Avoid passing ORM objects between threads, async calls, or outside the function where the session is active—convert them to dicts or pass only IDs if needed for later use.

Recent Dify versions (after v1.8.0) have improved session management for tool invocation, but the best practice is to always re-query by ID within a session. Upgrading to the latest version is recommended for a permanent fix, as session handling in workflow runners and tool services has been refactored (example PR, session fix). Temporary workarounds like expunging objects from the session before returning them exist, but are not recommended for production use.

For more details and code examples, see this issue thread.

To reply, just mention @dosu.

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[wangyucha]

Thanks, the issue has been resolved after the upgrade.@dosu