fix: Retry flags only on transport errors

[marandaneto]

💡 Motivation and Context

Align Elixir /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 overrides Req's :transient behavior for /flags so server responses are surfaced immediately while transient transport failures still get one retry by default.

💚 How did you test it?

• mix test test/posthog/api/client_test.exs test/posthog/config_test.exs
• mix test

📝 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. /flags now uses a request-specific Req retry function that skips HTTP responses, retries transport exceptions, uses default max retries of 1 with 0 disabling retries, and applies exponential backoff starting at 300ms.

[github-actions]

posthog-elixir Compliance Report

Date: 2026-07-02 10:07:11 UTC
Duration: 117671ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	609ms
Format Validation.Event Has Uuid	✅	611ms
Format Validation.Event Has Lib Properties	✅	610ms
Format Validation.Distinct Id Is String	✅	610ms
Format Validation.Token Is Present	✅	609ms
Format Validation.Custom Properties Preserved	✅	610ms
Format Validation.Event Has Timestamp	✅	609ms
Retry Behavior.Retries On 503	✅	5615ms
Retry Behavior.Does Not Retry On 400	✅	2614ms
Retry Behavior.Does Not Retry On 401	✅	2613ms
Retry Behavior.Respects Retry After Header	✅	5616ms
Retry Behavior.Implements Backoff	✅	15625ms
Retry Behavior.Retries On 500	✅	5615ms
Retry Behavior.Retries On 502	✅	5615ms
Retry Behavior.Retries On 504	✅	5614ms
Retry Behavior.Max Retries Respected	✅	15626ms
Deduplication.Generates Unique Uuids	✅	622ms
Deduplication.Preserves Uuid On Retry	✅	5615ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10621ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5618ms
Deduplication.No Duplicate Events In Batch	✅	616ms
Deduplication.Different Events Have Different Uuids	✅	612ms
Compression.Sends Gzip When Enabled	✅	610ms
Batch Format.Uses Proper Batch Structure	✅	610ms
Batch Format.Flush With No Events Sends Nothing	✅	606ms
Batch Format.Multiple Events Batched Together	✅	615ms
Error Handling.Does Not Retry On 403	✅	2612ms
Error Handling.Does Not Retry On 413	✅	2612ms
Error Handling.Retries On 408	✅	5613ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	610ms
Request Payload.Flags Request Uses V2 Query Param	✅	609ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	609ms
Request Payload.Flags Request Omits Authorization Header	✅	609ms
Request Payload.Token In Flags Body Matches Init	✅	610ms
Request Payload.Groups Round Trip	✅	609ms
Request Payload.Groups Default To Empty Object	✅	609ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	609ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	609ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	610ms
Request Lifecycle.No Flags Request On Init Alone	✅	3ms
Request Lifecycle.No Flags Request On Normal Capture	✅	609ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	1215ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	609ms
Retry Behavior.Retries Flags On 502	✅	912ms
Retry Behavior.Retries Flags On 504	✅	913ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	1212ms

[greptile-apps]

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

[marandaneto]

this will require PostHog/posthog-sdk-test-harness#30 to be merged/released

[greptile-apps]

_{Reviews (2): Last reviewed commit: "Merge branch 'main' into pi-flags-networ..." | Re-trigger Greptile}