fix: stop duplicating distinct_id in flags person properties

[marandaneto]

💡 Motivation and Context

/flags requests already send distinct_id at the top level. Automatically copying the same value into person_properties.distinct_id sends duplicated identity data and differs from the desired payload shape.

This PR keeps the top-level distinct_id and stops automatically injecting it into person_properties. Caller-provided person properties are still forwarded.

💚 How did you test it?

• uv run --extra test pytest posthog/test/test_client.py posthog/test/test_feature_flags.py -q

📝 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 sampo add to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

This was implemented with pi in dedicated git worktrees. I changed the /flags request construction so SDKs keep the top-level distinct_id while no longer auto-copying it into person_properties; explicit caller-provided person_properties['distinct_id'] values are still preserved where covered.

[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix: stop duplicating distinct_id in fla..." | Re-trigger Greptile}

[github-actions]

posthog-python Compliance Report

Date: 2026-07-02 11:45:38 UTC
Duration: 177146ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	517ms
Format Validation.Event Has Uuid	✅	1506ms
Format Validation.Event Has Lib Properties	✅	1507ms
Format Validation.Distinct Id Is String	✅	1507ms
Format Validation.Token Is Present	✅	1507ms
Format Validation.Custom Properties Preserved	✅	1506ms
Format Validation.Event Has Timestamp	✅	1507ms
Retry Behavior.Retries On 503	✅	9518ms
Retry Behavior.Does Not Retry On 400	✅	3506ms
Retry Behavior.Does Not Retry On 401	✅	3506ms
Retry Behavior.Respects Retry After Header	✅	9511ms
Retry Behavior.Implements Backoff	✅	23531ms
Retry Behavior.Retries On 500	✅	7503ms
Retry Behavior.Retries On 502	✅	7512ms
Retry Behavior.Retries On 504	✅	7509ms
Retry Behavior.Max Retries Respected	✅	23533ms
Deduplication.Generates Unique Uuids	✅	1496ms
Deduplication.Preserves Uuid On Retry	✅	7514ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	14521ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7507ms
Deduplication.No Duplicate Events In Batch	✅	1503ms
Deduplication.Different Events Have Different Uuids	✅	1507ms
Compression.Sends Gzip When Enabled	✅	1506ms
Batch Format.Uses Proper Batch Structure	✅	1507ms
Batch Format.Flush With No Events Sends Nothing	✅	1005ms
Batch Format.Multiple Events Batched Together	✅	1505ms
Error Handling.Does Not Retry On 403	✅	3508ms
Error Handling.Does Not Retry On 413	✅	3507ms
Error Handling.Retries On 408	✅	7513ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	1004ms
Request Payload.Flags Request Uses V2 Query Param	✅	1006ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	1007ms
Request Payload.Flags Request Omits Authorization Header	✅	1006ms
Request Payload.Token In Flags Body Matches Init	✅	1006ms
Request Payload.Groups Round Trip	✅	1007ms
Request Payload.Groups Default To Empty Object	✅	1006ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	1006ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	1007ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	1006ms
Request Lifecycle.No Flags Request On Init Alone	✅	503ms
Request Lifecycle.No Flags Request On Normal Capture	✅	1507ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	1010ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	1002ms
Retry Behavior.Retries Flags On 502	✅	1007ms
Retry Behavior.Retries Flags On 504	✅	1006ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	1508ms

[greptile-apps]

_{Reviews (2): Last reviewed commit: "Format local distinct_id evaluation chan..." | Re-trigger Greptile}