Feature request: Support on-demand or realtime feature flag updates (avoid stale cached experiment values)

Problem Statement

Hi PostHog team,

We are using posthog-flutter and are running into an experiment/feature-flag refresh issue.

Problem

Our flow is:

1. We fetch all feature flags on app start (it has some crucial info to run app).
2. We run an experiment whose assignment is effectively needed later (after a specific tracked event / later user state).
3. Until reassignment/evaluation happens, we keep getting the default/cached feature flag value.
4. The experiment variant is not updated unless we manually reload ALL flags.

Right now, the only relatively (not really sure because of this https://github.com/PostHog/posthog-flutter/issues/241) reliable way we found is:

await Posthog().reloadFeatureFlags();

Is manual reloadFeatureFlags() the only supported approach in Flutter for this case?

Solution Brainstorm

• Method to fetch a new value for only one specific flag,
• or real-time feature flags updates similar to how it works in Firebase.

Start by reviewing Posthog().reloadFeatureFlags() and the behavior discussed in issue #241. Compare that flow with the delayed experiment-assignment scenario described here, then determine the intended scope between per-flag fetching and realtime updates. Done means the supported refresh behavior is clearly defined and validated for later user-state changes.