ci: test latest Rails on stable Ruby

[dustinbyrne]

💡 Motivation and Context

The existing RSpec jobs vary Ruby versions but lock Rails to 7.2.3.1. posthog-rails declares support for Rails 5.2+, so add ongoing coverage for the latest stable Rails.

• Add a separate full-suite job on stable Ruby, including real OpenTelemetry export/fork integration.
• Resolve fresh dependencies on every run, honoring the existing 7-day RubyGems cooldown, and print the resolved Ruby, Rails and JSON versions.
• Allow the development Rails constraint to be overridden with RAILS_VERSION; existing jobs retain their current constraints and committed lockfiles.

Merge after #297. The new dependency resolution selects JSON 3 and exposes the pre-existing response parsing bug fixed there. This PR is independently based on main and does not duplicate that runtime fix.

💚 How did you test it?

• Local resolution: Rails 8.1.4, JSON 3.0.2, OTel logs SDK 0.7.0/exporter 0.6.0 (Ruby 3.4.7, Bundler 4.0.13).
• On unchanged runtime code, a focused remote flag spec reproduces the known JSON 3 failure (nil rather than true). The full baseline run also showed flag failures but was stopped at the 180-second local deadline.
• In a disposable checkout combining this CI change with fix(flags): support JSON 3 response parsing #297: 1,255 specs passed, no failures or pending, including real OTel integration. No additional Rails 8.1 failure observed in that suite. Ubuntu/stable-Ruby execution is left to the new CI job.
• Existing default bundle: 1,254 specs passed, with the two expected optional OTel pending tests.
• Full RuboCop, public API snapshot, actionlint, Gemfile syntax, YAML parsing and diff checks passed.

CI/development configuration only; no published API or runtime behavior changes, so no changeset.

📝 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.

🤖 Agent context

Autonomy: Human-driven (agent-assisted).

Implemented and validated with Pi using Git, Bundler/RSpec, actionlint and the GitHub CLI. A fresh read-only reviewer inspected the scoped diff. The latest dependency lane is separate from the locked compatibility matrix and the JSON 3 runtime fix in #297. Human review is required.

[github-actions]

posthog-ruby-sync Compliance Report

Date: 2026-10-07T20:21:22.388297+00:00
Duration: 94139ms

⚠️ Some Tests Failed

45/47 tests passed, 2 failed

---

Capture Tests

⚠️ 29/30 tests passed, 1 failed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	10ms
Format Validation.Event Has Uuid	✅	7ms
Format Validation.Event Has Lib Properties	✅	6ms
Format Validation.Distinct Id Is String	✅	9ms
Format Validation.Token Is Present	✅	7ms
Format Validation.Custom Properties Preserved	✅	7ms
Format Validation.Event Has Timestamp	✅	8ms
Format Validation.Non Utc Event Timestamp Is Converted To Utc	✅	7ms
Retry Behavior.Retries On 503	✅	5344ms
Retry Behavior.Does Not Retry On 400	✅	2008ms
Retry Behavior.Does Not Retry On 401	✅	2011ms
Retry Behavior.Respects Retry After Header	✅	8014ms
Retry Behavior.Implements Backoff	✅	15289ms
Retry Behavior.Retries On 500	✅	5115ms
Retry Behavior.Retries On 502	✅	5115ms
Retry Behavior.Retries On 504	✅	5115ms
Retry Behavior.Max Retries Respected	✅	15592ms
Deduplication.Generates Unique Uuids	✅	22ms
Deduplication.Preserves Uuid On Retry	✅	5113ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10359ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5154ms
Deduplication.No Duplicate Events In Batch	✅	18ms
Deduplication.Different Events Have Different Uuids	✅	8ms
Compression.Sends Gzip When Enabled	✅	7ms
Batch Format.Uses Proper Batch Structure	✅	6ms
Batch Format.Flush With No Events Sends Nothing	✅	4ms
Batch Format.Multiple Events Batched Together	❌	16ms
Error Handling.Does Not Retry On 403	✅	2009ms
Error Handling.Does Not Retry On 413	✅	2009ms
Error Handling.Retries On 408	✅	5115ms

Failures

batch_format.multiple_events_batched_together

Expected 1 requests, got 5

Feature_Flags Tests

⚠️ 16/17 tests passed, 1 failed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	8ms
Request Payload.Flags Request Uses V2 Query Param	✅	7ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	6ms
Request Payload.Flags Request Omits Authorization Header	✅	7ms
Request Payload.Token In Flags Body Matches Init	✅	7ms
Request Payload.Groups Round Trip	✅	7ms
Request Payload.Groups Default To Empty Object	✅	7ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	8ms
Request Payload.Disable Geoip Omitted Defaults To False	❌	8ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	8ms
Request Lifecycle.No Flags Request On Init Alone	✅	3ms
Request Lifecycle.No Flags Request On Normal Capture	✅	6ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	9ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	7ms
Retry Behavior.Retries Flags On 502	✅	110ms
Retry Behavior.Retries Flags On 504	✅	110ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	9ms

Failures

request_payload.disable_geoip_omitted_defaults_to_false

Field 'geoip_disable' not found in /flags request body at path 'geoip_disable'. Available keys: ['distinct_id', 'groups', 'person_properties', 'group_properties', 'flag_keys_to_evaluate', 'token']

[github-actions]

posthog-ruby-async Compliance Report

Date: 2026-10-07T20:21:27.449967+00:00
Duration: 98502ms

⚠️ Some Tests Failed

46/47 tests passed, 1 failed

---

Capture Tests

✅ 30/30 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	109ms
Format Validation.Event Has Uuid	✅	107ms
Format Validation.Event Has Lib Properties	✅	110ms
Format Validation.Distinct Id Is String	✅	106ms
Format Validation.Token Is Present	✅	108ms
Format Validation.Custom Properties Preserved	✅	108ms
Format Validation.Event Has Timestamp	✅	108ms
Format Validation.Non Utc Event Timestamp Is Converted To Utc	✅	10ms
Retry Behavior.Retries On 503	✅	5309ms
Retry Behavior.Does Not Retry On 400	✅	2109ms
Retry Behavior.Does Not Retry On 401	✅	2109ms
Retry Behavior.Respects Retry After Header	✅	8017ms
Retry Behavior.Implements Backoff	✅	15616ms
Retry Behavior.Retries On 500	✅	5211ms
Retry Behavior.Retries On 502	✅	5212ms
Retry Behavior.Retries On 504	✅	5212ms
Retry Behavior.Max Retries Respected	✅	15722ms
Deduplication.Generates Unique Uuids	✅	112ms
Deduplication.Preserves Uuid On Retry	✅	5212ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10412ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5214ms
Deduplication.No Duplicate Events In Batch	✅	111ms
Deduplication.Different Events Have Different Uuids	✅	106ms
Compression.Sends Gzip When Enabled	✅	106ms
Batch Format.Uses Proper Batch Structure	✅	105ms
Batch Format.Flush With No Events Sends Nothing	✅	4ms
Batch Format.Multiple Events Batched Together	✅	110ms
Error Handling.Does Not Retry On 403	✅	2107ms
Error Handling.Does Not Retry On 413	✅	2109ms
Error Handling.Retries On 408	✅	5211ms

Feature_Flags Tests

⚠️ 16/17 tests passed, 1 failed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	107ms
Request Payload.Flags Request Uses V2 Query Param	✅	106ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	108ms
Request Payload.Flags Request Omits Authorization Header	✅	107ms
Request Payload.Token In Flags Body Matches Init	✅	106ms
Request Payload.Groups Round Trip	✅	106ms
Request Payload.Groups Default To Empty Object	✅	106ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	105ms
Request Payload.Disable Geoip Omitted Defaults To False	❌	106ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	108ms
Request Lifecycle.No Flags Request On Init Alone	✅	2ms
Request Lifecycle.No Flags Request On Normal Capture	✅	105ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	110ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	106ms
Retry Behavior.Retries Flags On 502	✅	235ms
Retry Behavior.Retries Flags On 504	✅	246ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	108ms

Failures

request_payload.disable_geoip_omitted_defaults_to_false

Field 'geoip_disable' not found in /flags request body at path 'geoip_disable'. Available keys: ['distinct_id', 'groups', 'person_properties', 'group_properties', 'flag_keys_to_evaluate', 'token']

[greptile-apps]

[High risk] Adds a new CI job that tests with latest Rails and updates all dependencies.

No new blocking issue found; keep the stated merge order after #297.

_{Reviews (1) · Last reviewed commit: "ci: test latest Rails on stable Ruby" · Reviewed by Greptile}