[ketanmixpanel]

Summary

SDK-448: $experiment_started exposures fired through the Mixpanel OpenFeature provider now include "$openfeature_provider": true, so OpenFeature usage can be told apart from direct SDK flag calls. Direct SDK calls are unchanged (no property).

No public API change: no new public methods, parameters or fields. The provider signals the SDK through an argument it already passes on every evaluation.

How

• Provider: adds "$openfeature_provider": true to the evaluation context it already passes to getVariant, set after the customer attributes so a same-named attribute cannot override it.
• SDK: the exposure-tracking code (which already receives the context to read distinct_id) copies the marker onto $experiment_started when the context value is exactly true. Covers local and remote evaluation.
• Local evaluation is unaffected: it only reads the flag assignment key, distinct_id and custom_properties.

Testing

• New SDK tests (local and remote): marker present tags the exposure, absent does not. The protected trackExposure signature is unchanged.
• New provider tests: marker reaches getVariant, cannot be overridden by a customer attribute, and is set for a null context.
• mvn test (SDK): 396, 0 failures. cd openfeature-provider && mvn test: 38, 0 failures.
• Also verified the provider against the local SDK (throwaway version installed to ~/.m2, removed afterwards), including an end-to-end test with a real RemoteFlagsProvider: 39/39.

Note: marker is sent to the server on remote evaluation

Because the marker lives in the evaluation context, remote evaluation sends it to /flags with the rest of the context. The flags API accepts and ignores it (checked in analytics/go/src/mixpanel.com/flags/api/handlers/evaluatefeatureflags.go):

• request validation only type-checks distinct_id and device_id;
• evaluation only reads the assignment key, distinct_id/device_id, custom_properties and hierarchical group IDs;
• logRequest does not log it.

So it has no effect on targeting, rollout or variant assignment; it is only visible in the GET context query parameter.

Release order

Older SDKs ignore the marker, so the provider change is safe on its own (no errors; the property just does not appear). The property appears once customers run an SDK release containing this change; the provider minimum SDK version was intentionally not bumped here and should be raised after the SDK release. No version or changelog edits.

🤖 Generated with Claude Code

[linear-code]

SDK-448

[greptile-apps]

Confidence Score: 5/5

[Medium impact] The PR appears safe to merge; no actionable issues were found.

_{Reviews (1) · Last reviewed commit: "feat: tag OpenFeature exposures with $op..." · Reviewed by Greptile}