fix(flags): load shared definitions without a secret key

[dustinbyrne]

💡 Motivation and Context

Like PostHog/posthog-python#1039, a worker consuming shared feature flag definitions should not need a privileged secret key. Existing initialization gates prevent that supported cache-consumer configuration from evaluating flags locally.

Changes

• Permit the configured definition cache provider to supply definitions without a secret/personal API key.
• Keyless consumers read the shared cache directly, without invoking the fetch-decision callback or publishing definitions. They cannot claim fetch leadership they are unable to use.
• With privileged credentials, retain the existing decision flow: false reads the cache; true fetches definitions and publishes them. Direct definition requests remain authenticated.
• Add public-entry regressions, update active credential/provider docs, and include scoped patch release metadata.

Cache-only readers bypass the shared loader specification's decision-first provider step; credentialed consumers retain that step.

The existing supervision, NegativeKnowledge dependency, bounded provider callbacks and polling lifecycle are retained.

💚 How did you test it?

• Focused provider/loader suites: 30 tests passed.
• mix test: 614 tests, zero failures, 18 integration tests excluded.
• mix format --check-formatted, forced warnings-as-errors compilation, strict Credo and public API snapshot check: passed.
• Shared-leadership regression fails against the prior loader and passes with the fix; true, raising, throwing and hanging decision callbacks are never invoked by keyless readers.
• Local validation used Elixir 1.19.5/OTP 28; no live service credentials were used.

Release scope

Patch release for hex/posthog. Existing signatures, capture defaults and wire formats are unchanged.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Implemented with Pi worker agents and reviewed by separate fresh-context Pi reviewers. A simplify pass covered the scoped source/tests/docs before final local validation. Human review remains required.

[github-actions]

posthog-elixir Compliance Report

Date: 2026-10-10T04:16:37.539898+00:00
Duration: 108702ms

⚠️ Some Tests Failed

40/47 tests passed, 7 failed

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Capture Tests

⚠️ 29/30 tests passed, 1 failed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	610ms
Format Validation.Event Has Uuid	✅	612ms
Format Validation.Event Has Lib Properties	✅	611ms
Format Validation.Distinct Id Is String	✅	611ms
Format Validation.Token Is Present	✅	611ms
Format Validation.Custom Properties Preserved	✅	611ms
Format Validation.Event Has Timestamp	✅	611ms
Format Validation.Non Utc Event Timestamp Is Converted To Utc	❌	611ms
Retry Behavior.Retries On 503	✅	5616ms
Retry Behavior.Does Not Retry On 400	✅	2614ms
Retry Behavior.Does Not Retry On 401	✅	2612ms
Retry Behavior.Respects Retry After Header	✅	5618ms
Retry Behavior.Implements Backoff	✅	15627ms
Retry Behavior.Retries On 500	✅	5615ms
Retry Behavior.Retries On 502	✅	5616ms
Retry Behavior.Retries On 504	✅	5616ms
Retry Behavior.Max Retries Respected	✅	15619ms
Deduplication.Generates Unique Uuids	✅	623ms
Deduplication.Preserves Uuid On Retry	✅	5616ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10621ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5618ms
Deduplication.No Duplicate Events In Batch	✅	617ms
Deduplication.Different Events Have Different Uuids	✅	614ms
Compression.Sends Gzip When Enabled	✅	610ms
Batch Format.Uses Proper Batch Structure	✅	610ms
Batch Format.Flush With No Events Sends Nothing	✅	607ms
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	✅	5615ms

Failures

format_validation.non_utc_event_timestamp_is_converted_to_utc

Event 0 field 'timestamp' instant '2026-10-10T04:14:53.435257Z' != expected '2025-01-02T03:04:05Z'

Feature_Flags Tests

⚠️ 11/17 tests passed, 6 failed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	10ms
Request Payload.Flags Request Uses V2 Query Param	✅	8ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	7ms
Request Payload.Flags Request Omits Authorization Header	✅	8ms
Request Payload.Token In Flags Body Matches Init	✅	8ms
Request Payload.Groups Round Trip	✅	8ms
Request Payload.Groups Default To Empty Object	❌	8ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	9ms
Request Payload.Disable Geoip Omitted Defaults To False	❌	7ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	9ms
Request Lifecycle.No Flags Request On Init Alone	✅	4ms
Request Lifecycle.No Flags Request On Normal Capture	✅	610ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	13ms
Request Lifecycle.Mock Response Value Is Returned To Caller	❌	8ms
Retry Behavior.Retries Flags On 502	❌	311ms
Retry Behavior.Retries Flags On 504	❌	313ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	❌	611ms

Failures

request_payload.groups_default_to_empty_object

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

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', 'api_key', 'flag_keys_to_evaluate']

request_lifecycle.mock_response_value_is_returned_to_caller

Last action result missing field 'value'. Keys: ['error', 'success']

retry_behavior.retries_flags_on_502

Last action result missing field 'value'. Keys: ['error', 'success']

retry_behavior.retries_flags_on_504

Last action result missing field 'value'. Keys: ['error', 'success']

side_effect_events.get_feature_flag_captures_feature_flag_called_event

Expected 1 events with name '$feature_flag_called', got 0