fix: Retry flags only on transport errors

[marandaneto]

💡 Motivation and Context

Align Python /flags/?v=2 retry behavior with the other SDK fixes: retry only bounded network/transport/timeout failures, and do not retry HTTP/API status responses like 408, 429, or 5xx.

This keeps transient network handling while avoiding repeated requests when PostHog has already returned an API response.

💚 How did you test it?

• uv run --extra test --extra dev ruff check posthog/request.py posthog/client.py posthog/__init__.py posthog/test/test_request.py posthog/test/test_client.py
• uv run --extra test --extra dev python .github/scripts/check_public_api.py
• uv run --extra test pytest posthog/test/test_request.py posthog/test/test_client.py

📝 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)

Implemented with pi. The retry policy was changed from urllib3 status-code retries to explicit /flags transport retries, with default max retries set to 1, 0 disabling retries, and exponential backoff starting at 300ms.

[marandaneto]

#708 was closed because its a fork and i cant run the sdk harness as a fork

[github-actions]

posthog-python Compliance Report

Date: 2026-07-02 10:26:50 UTC
Duration: 177188ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	516ms
Format Validation.Event Has Uuid	✅	1508ms
Format Validation.Event Has Lib Properties	✅	1506ms
Format Validation.Distinct Id Is String	✅	1507ms
Format Validation.Token Is Present	✅	1507ms
Format Validation.Custom Properties Preserved	✅	1507ms
Format Validation.Event Has Timestamp	✅	1507ms
Retry Behavior.Retries On 503	✅	9518ms
Retry Behavior.Does Not Retry On 400	✅	3505ms
Retry Behavior.Does Not Retry On 401	✅	3509ms
Retry Behavior.Respects Retry After Header	✅	9509ms
Retry Behavior.Implements Backoff	✅	23522ms
Retry Behavior.Retries On 500	✅	7514ms
Retry Behavior.Retries On 502	✅	7513ms
Retry Behavior.Retries On 504	✅	7511ms
Retry Behavior.Max Retries Respected	✅	23517ms
Deduplication.Generates Unique Uuids	✅	1509ms
Deduplication.Preserves Uuid On Retry	✅	7513ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	14521ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7507ms
Deduplication.No Duplicate Events In Batch	✅	1504ms
Deduplication.Different Events Have Different Uuids	✅	1507ms
Compression.Sends Gzip When Enabled	✅	1507ms
Batch Format.Uses Proper Batch Structure	✅	1506ms
Batch Format.Flush With No Events Sends Nothing	✅	1005ms
Batch Format.Multiple Events Batched Together	✅	1505ms
Error Handling.Does Not Retry On 403	✅	3509ms
Error Handling.Does Not Retry On 413	✅	3507ms
Error Handling.Retries On 408	✅	7512ms

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	✅	1006ms
Request Payload.Flags Request Omits Authorization Header	✅	1006ms
Request Payload.Token In Flags Body Matches Init	✅	1007ms
Request Payload.Groups Round Trip	✅	1006ms
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	✅	502ms
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	✅	1003ms
Retry Behavior.Retries Flags On 502	✅	1005ms
Retry Behavior.Retries Flags On 504	✅	1007ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	1508ms

[greptile-apps]

Comments Outside Diff (1)

1. posthog/test/test_request.py, line 507-549 (link)

   Prefer @parameterized.expand over subTest loops

   Two tests (test_flags_retries_contract_http_status_errors and test_flags_does_not_retry_other_http_status_errors) iterate over status code lists with for … subTest rather than using @parameterized.expand, which is the team standard (see test_feature_flags_request_max_retries_is_forwarded added in this same PR for the correct pattern). Failures in subTest loops are harder to locate in CI output, and a future reader must scan the loop body to understand what inputs are covered. Both tests are good candidates for @parameterized.expand([(502,), (504,)]) and @parameterized.expand([(408,), (429,), (500,), (503,)]) respectively.

   Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

_{Reviews (1): Last reviewed commit: "fix: retry flags only on transport error..." | Re-trigger Greptile}

[marandaneto]

@ioannisj blind approval pls because of #724 (comment)

[marandaneto]

Addressed the Greptile feedback in fe937c6: converted the /flags HTTP status retry tests from subTest loops to @parameterized.expand, and also de-duplicated retry bookkeeping from the inline comment.