feat(flags): add $feature_flag_has_experiment to $feature_flag_called events

[haacked]

💡 Motivation and Context

Part of a cross-SDK effort to shrink $feature_flag_called events. This first phase adds a $feature_flag_has_experiment boolean property to every $feature_flag_called event, reflecting the server's has_experiment signal: metadata.has_experiment in the /flags?v=2 response and has_experiment on /api/feature_flag/local_evaluation flag definitions. When the server does not report the field (older deployments, bootstrapped flags), the property is omitted, so it is tri-state: true, false, or absent (unknown).

This lets ingestion distinguish experiment-linked flag events (which need the full property set for exposure analysis) from the rest, and lets us measure the split before a later phase strips the expensive properties ($feature/<key>, $feature_flag_payload, per-event system metadata) from non-experiment flag events. This PR intentionally minimizes nothing: no properties are removed, no config options are added, and dedupe behavior is unchanged.

Changes

• FeatureFlagMetadata parses has_experiment from /flags?v=2 metadata (boolean-coerced, default false).
• Poller get_feature_flag returns has_experiment sourced from the stored /flags/definitions definition on local eval and from response metadata on remote fallback; get_all_flags_and_payloads carries parsed flag objects through an internal key (stripped from the public return) to reach metadata on the bulk remote path.
• client.rb adds the property on the single-flag path and threads it into EvaluatedFlagRecords; snapshot-path events include it (missing flags omit the property).
• Public API snapshot regenerated; minor changeset.

💚 How did you test it?

bundle exec rspec: 614 examples, 0 failures, with new coverage for remote true/false/absent/missing-flag, local-definition true/absent, single-flag local and remote v4/v3 paths, and metadata parsing; five existing exact-hash assertions updated. rubocop clean.

📝 Checklist

• 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

[github-actions]

posthog-ruby Compliance Report

Date: 2026-07-15 23:27:12 UTC
Duration: 98350ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	9ms
Format Validation.Event Has Uuid	✅	105ms
Format Validation.Event Has Lib Properties	✅	108ms
Format Validation.Distinct Id Is String	✅	106ms
Format Validation.Token Is Present	✅	106ms
Format Validation.Custom Properties Preserved	✅	106ms
Format Validation.Event Has Timestamp	✅	107ms
Retry Behavior.Retries On 503	✅	5413ms
Retry Behavior.Does Not Retry On 400	✅	2108ms
Retry Behavior.Does Not Retry On 401	✅	2109ms
Retry Behavior.Respects Retry After Header	✅	8115ms
Retry Behavior.Implements Backoff	✅	15622ms
Retry Behavior.Retries On 500	✅	5213ms
Retry Behavior.Retries On 502	✅	5211ms
Retry Behavior.Retries On 504	✅	5212ms
Retry Behavior.Max Retries Respected	✅	15623ms
Deduplication.Generates Unique Uuids	✅	111ms
Deduplication.Preserves Uuid On Retry	✅	5212ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10318ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5214ms
Deduplication.No Duplicate Events In Batch	✅	111ms
Deduplication.Different Events Have Different Uuids	✅	107ms
Compression.Sends Gzip When Enabled	✅	105ms
Batch Format.Uses Proper Batch Structure	✅	106ms
Batch Format.Flush With No Events Sends Nothing	✅	4ms
Batch Format.Multiple Events Batched Together	✅	110ms
Error Handling.Does Not Retry On 403	✅	2107ms
Error Handling.Does Not Retry On 413	✅	2109ms
Error Handling.Retries On 408	✅	5211ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	108ms
Request Payload.Flags Request Uses V2 Query Param	✅	109ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	109ms
Request Payload.Flags Request Omits Authorization Header	✅	106ms
Request Payload.Token In Flags Body Matches Init	✅	106ms
Request Payload.Groups Round Trip	✅	106ms
Request Payload.Groups Default To Empty Object	✅	107ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	107ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	106ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	106ms
Request Lifecycle.No Flags Request On Init Alone	✅	3ms
Request Lifecycle.No Flags Request On Normal Capture	✅	106ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	108ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	106ms
Retry Behavior.Retries Flags On 502	✅	247ms
Retry Behavior.Retries Flags On 504	✅	208ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	108ms

[greptile-apps]

_{Reviews (1): Last reviewed commit: "Add $feature_flag_has_experiment to $fea..." | Re-trigger Greptile}

[turnipdabeets]

LGTM! Every read is nil-safe (&. chains / short-circuits), the internal flagDetails key is stripped before the public return, and true/false/absent are covered on the metadata, single-flag local/remote, and snapshot paths.