Can't update reactive value from download handler

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
python
Domain
backend

Research direction

Start by reproducing the two linked Shinylive examples, focusing on the download handler, reactive value, and separately registered side effect. Trace how download-handler execution interacts with reactive updates, then establish whether updates should be synchronous or explicitly supported; done means the intended behavior is documented and the reported cases behave consistently.

Written by the indexing model from the issue text.

Description

ai-triage:done needs-triage Priority: Medium

When attempting to update a reactive value from within a download handler, the value is either not updated until modified by another action button:
Shinylive example

Or the value is not updated at all when separately registering a side effect:
Shinylive example

Is this the intended behavior (implicit asynchrony for the download handler)? Or would there be a way to properly modify reactive values from within download handlers?

Dominant language
Python
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Avg merge
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Merged PRs (30d)
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