[turnipdabeets]

💡 Motivation and Context

This assumed we’ve pulled in Android 4.0

PostHogConfig.onFeatureFlags was a void Function() and reloadFeatureFlags() returned Future<void>, so Flutter apps couldn't tell what loaded or whether loading failed. posthog-ios 4.0 passes this to its listener and reload callback (PostHog/posthog-ios#897, #913), posthog-android 4.0 gets the same (PostHog/posthog-android#877), and posthog-js already passes it to onFeatureFlags.

Closes #231

Both now carry a new PostHogFeatureFlagsLoaded:

Field	Meaning
flags	keys of the enabled flags
variants	enabled flag → true or the variant string; disabled flags left out
errorsLoading	true when the latest load failed; the values are then the last known ones

Per platform:

Platform	onFeatureFlags	reloadFeatureFlags()
iOS/macOS	from posthog-ios onFeatureFlags	from posthog-ios reloadFeatureFlags(_:)
Android	from posthog-android PostHogFeatureFlagsCallback	from posthog-android reloadFeatureFlags
Web	from posthog-js onFeatureFlags	posthog-js 1.438.2+: awaits featureFlags.reloadFeatureFlagsAsync(), which settles after this reload's own request (not one already in flight); errorsLoading unless it loaded. Older posthog-js: the next onFeatureFlags call, with a timeout covering every retry posthog-js may make ((feature_flag_request_max_retries + 2) × feature_flag_request_timeout_ms + 500 ms per retry, 9.5 s with defaults)
Windows/Linux	from the Dart core	awaits the Dart core's reload

fromMap stays internal (channel_serialization.dart), in line with #646.

Breaking: onFeatureFlags = () { … } becomes (loaded) { … } or (_) { … }. Callers of reloadFeatureFlags() are unaffected; custom platform interface implementations must return the new type.

Depends on #663 (posthog-android 4.0). The Android code is written against the PostHogFeatureFlagsLoaded posthog-android 4.0 adds, which is still in review, so this stays a draft until that API is final.

💚 How did you test it?

• flutter analyze, flutter test (1258 pass), dart format, scripts/check-api-dart.sh (snapshot updated).
• New tests: the method channel passes native flags to the callback and drops disabled ones; malformed native args give empty flags; on desktop, reloadFeatureFlags() returns the loaded flags, and after a failed request returns the last known flags with errorsLoading: true, as does onFeatureFlags. The desktop test fails when errorsLoading is hardcoded to false.
• flutter build ios --simulator against a local posthog-ios 4.0 checkout (temporary .package(path:), reverted), and flutter build web.
• Web (Chrome): reloadFeatureFlags awaits reloadFeatureFlagsAsync() when present and reports errorsLoading when posthog-js skips the request; the first test fails without that path.
• Not yet built: Android, until posthog-android 4.0 exists locally.

📝 Checklist

• All commits are signed (see Commit signing)
• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Claude Code (Claude Opus 5.5) made this as part of the feature flag parity work across the iOS, Android and Flutter majors. The field names mirror posthog-ios's PostHogFeatureFlagsLoaded. For web reloadFeatureFlags(), waiting only for the next posthog-js onFeatureFlags call could return a response from a request already in flight, and never fires when posthog-js skips the request, so newer posthog-js uses reloadFeatureFlagsAsync() and older versions keep that path behind a timeout.

🤖 Generated with Claude Code

[posthog]

PostHog Review · Standard · reviewed 93f0034: 1 Should fix.

This is the only automatic review while this pull request is a draft. Comment @posthog review to review new changes sooner. Otherwise, a review of the new changes runs when you mark it ready for review.

See this review and its findings in PostHog Review. Comment @posthog review --deep for a Deep review. A Deep review takes longer and looks deeper than a Standard review.

[github-actions]

posthog-flutter Compliance Report

Date: 2026-10-27 22:18:27 UTC
Duration: 96884ms

✅ All Tests Passed!

45/45 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	144ms
Format Validation.Event Has Uuid	✅	119ms
Format Validation.Event Has Lib Properties	✅	117ms
Format Validation.Distinct Id Is String	✅	117ms
Format Validation.Token Is Present	✅	116ms
Format Validation.Custom Properties Preserved	✅	119ms
Format Validation.Event Has Timestamp	✅	119ms
Retry Behavior.Retries On 503	✅	5332ms
Retry Behavior.Does Not Retry On 400	✅	2119ms
Retry Behavior.Does Not Retry On 401	✅	2118ms
Retry Behavior.Respects Retry After Header	✅	8127ms
Retry Behavior.Implements Backoff	✅	15446ms
Retry Behavior.Retries On 500	✅	5229ms
Retry Behavior.Retries On 502	✅	5229ms
Retry Behavior.Retries On 504	✅	5226ms
Retry Behavior.Max Retries Respected	✅	15434ms
Deduplication.Generates Unique Uuids	✅	126ms
Deduplication.Preserves Uuid On Retry	✅	5225ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10337ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5232ms
Deduplication.No Duplicate Events In Batch	✅	125ms
Deduplication.Different Events Have Different Uuids	✅	118ms
Compression.Sends Gzip When Enabled	✅	118ms
Batch Format.Uses Proper Batch Structure	✅	115ms
Batch Format.Flush With No Events Sends Nothing	✅	109ms
Batch Format.Multiple Events Batched Together	✅	125ms
Error Handling.Does Not Retry On 403	✅	2117ms
Error Handling.Does Not Retry On 413	✅	2118ms
Error Handling.Retries On 408	✅	5224ms

Feature_Flags Tests

✅ 16/16 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	14ms
Request Payload.Flags Request Uses V2 Query Param	✅	10ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	10ms
Request Payload.Flags Request Omits Authorization Header	✅	10ms
Request Payload.Token In Flags Body Matches Init	✅	10ms
Request Payload.Groups Round Trip	✅	11ms
Request Payload.Groups Default To Empty Object	✅	10ms
Request Payload.Person Properties Distinct Id Auto Populated When Caller Omits It	✅	10ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	10ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	10ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	10ms
Request Lifecycle.No Flags Request On Init Alone	✅	5ms
Request Lifecycle.No Flags Request On Normal Capture	✅	113ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	17ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	10ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	117ms

[posthog]

PostHog Review · Standard · reviewed 80ac673: 1 Should fix.

[dustinbyrne]

The native/desktop result plumbing and major migration look consistent, but the legacy web fallback can report a successful retry as failed with default settings. Consider accounting for the full retry lifecycle before completing the fallback. Two optional documentation qualifications are inline. Native 4.0 dependency/build prerequisites remain separate.

AI-assisted review.

[dustinbyrne]

All three previous findings are addressed. The successful-retry reproduction now returns fresh flags without reporting a failure. One optional public-documentation update is inline. Native 4.0 dependency availability and successful native builds remain release prerequisites.

AI-assisted review.