fix: fall back when payload compression fails

[marandaneto]

💡 Motivation and Context

If local gzip compression fails while preparing a batch upload, the SDK should still send the original payload uncompressed instead of failing before the request is sent.

This updates the compressed batch path to build gzip content first and fall back to the normal JSON request path when gzip content creation fails.

💚 How did you test it?

• dotnet test tests/UnitTests/UnitTests.csproj --filter HttpClientExtensionsTests

📝 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

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Implemented as part of a cross-SDK consistency pass for client-side compression failure fallback. Kept the change surgical and limited to the gzip request-construction path.

[github-actions]

posthog-dotnet Compliance Report

Date: 2026-06-29 09:05:33 UTC
Duration: 629ms

⚠️ Some Tests Failed

2/16 tests passed, 14 failed

---

Feature_Flags Tests

⚠️ 2/16 tests passed, 14 failed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	❌	43ms
Request Payload.Flags Request Uses V2 Query Param	❌	22ms
Request Payload.Flags Request Hits Flags Path Not Decide	❌	6ms
Request Payload.Flags Request Omits Authorization Header	❌	6ms
Request Payload.Token In Flags Body Matches Init	❌	4ms
Request Payload.Groups Round Trip	❌	5ms
Request Payload.Groups Default To Empty Object	❌	5ms
Request Payload.Person Properties Distinct Id Auto Populated When Caller Omits It	❌	5ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	❌	5ms
Request Payload.Disable Geoip Omitted Defaults To False	❌	4ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	❌	5ms
Request Lifecycle.No Flags Request On Init Alone	✅	3ms
Request Lifecycle.No Flags Request On Normal Capture	✅	183ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	❌	6ms
Request Lifecycle.Mock Response Value Is Returned To Caller	❌	5ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	❌	5ms

Failures

request_payload.request_with_person_properties_device_id

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.flags_request_uses_v2_query_param

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.flags_request_hits_flags_path_not_decide

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.flags_request_omits_authorization_header

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.token_in_flags_body_matches_init

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.groups_round_trip

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.groups_default_to_empty_object

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.person_properties_distinct_id_auto_populated_when_caller_omits_it

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.disable_geoip_false_propagates_as_geoip_disable_false

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.disable_geoip_omitted_defaults_to_false

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_payload.flag_keys_to_evaluate_contains_only_requested_key

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_lifecycle.two_flag_calls_produce_two_remote_requests

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

request_lifecycle.mock_response_value_is_returned_to_caller

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

side_effect_events.get_feature_flag_captures_feature_flag_called_event

404, message='Not Found', url='http://sdk-adapter:8080/get_feature_flag'

[greptile-apps]

_{Reviews (1): Last reviewed commit: "fix: fall back when payload compression ..." | Re-trigger Greptile}

[greptile-apps]

_{Reviews (2): Last reviewed commit: "Fix changeset package names" | Re-trigger Greptile}

[ioannisj]

LG but left a couple of comments