Open the Playground at a given session from the URL (?playground=true&session=<id>) #15747

Feature Request

Let the flow editor's URL open the Playground and select a session:

/flow/<flow-id>?playground=true&session=<session-id>

• playground=true opens the Playground modal, as proposed in feat: add url parameter to playground modal #7270.
• session=<session-id> selects that session, if it exists for the flow; otherwise the Playground opens as usual.

#7270 already syncs the Playground modal with a URL parameter, so this could extend it with session. The /playground/<id>/ shareable page doesn't cover this: it needs the flow to be public and starts a new chat.

Motivation

External tools that run flows through the API can pass a session_id per run, and Langflow stores each run as its own Playground session. But there is no way to link from outside to that session: a user who follows a link to the flow (/flow/<flow-id>) has to open the Playground and look for the right session by hand, which is slow and error-prone when a flow has many sessions.

Our use case: we orchestrate workflows with LangGraph, and each workflow step calls a Langflow flow through /api/v1/run/<flow> with session_id set to the workflow run's id. Our UI shows the run and links each step to its flow. With this feature the link would open the exact conversation for that run.

Tested on Langflow 1.12.4.

Your Contribution

Happy to test a pull request against our setup.