feat(flags): add fresh option to feature flag methods#3119
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Add a `fresh` option to `getFeatureFlag()`, `getFeatureFlagResult()`, and
`isFeatureEnabled()` that only returns values loaded from the server, not
cached localStorage values.
By default, these methods may return cached values from localStorage if the
`/flags` endpoint hasn't responded yet. This reduces flicker but means you
might briefly see stale values (e.g., a flag that was disabled on the server).
With `{ fresh: true }`, the methods return `undefined` until the `/flags`
endpoint responds, ensuring you always get the current server state.
Usage:
```js
// Default behavior (may return cached values)
posthog.getFeatureFlag('my-flag')
// Only return fresh values from server
posthog.getFeatureFlag('my-flag', { fresh: true })
```
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Co-Authored-By: Claude <noreply@anthropic.com>
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gustavohstrassburger
approved these changes
Feb 19, 2026
| * @param {Object|String} options (optional) If {send_event: false}, we won't send an $feature_flag_call event to PostHog. | ||
| * If {fresh: true}, we won't return cached values from localStorage - only values loaded from the server. | ||
| */ | ||
| getFeatureFlag(key: string, options?: { send_event?: boolean }): boolean | string | undefined { |
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We have the type options?: { send_event?: boolean; fresh?: boolean } in several places, maybe worth creating a type or an interface for it an centralize it.
Extract the inline `{ send_event?: boolean; fresh?: boolean }` options
type into a centralized `FeatureFlagOptions` type in @posthog/types.
This reduces duplication across 9 occurrences in 3 files and provides
a single source of truth for the feature flag lookup options.
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Co-Authored-By: Claude <noreply@anthropic.com>
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Summary
Adds a
freshoption togetFeatureFlag(),getFeatureFlagResult(), andisFeatureEnabled()that only returns values loaded from the server, not cached localStorage values.Problem
By default, feature flag methods may return cached values from localStorage if the
/flagsendpoint hasn't responded yet. This reduces flicker but means users might briefly see stale values - for example, a flag that was disabled on the server would still return its cached value until the network request completes.This was causing issues where disabled flags continued to show their enabled variants to users who had previously been enrolled.
Solution
Add a non-breaking
{ fresh: true }option that returnsundefineduntil the/flagsendpoint responds, ensuring you always get the current server state.Changes
fresh?: booleanoption togetFeatureFlag(),getFeatureFlagResult(), andisFeatureEnabled()fresh: true, returnsundefinedif_flagsLoadedFromRemoteis falsefresh: true