[gustavohstrassburger]

💡 Motivation and Context

Why: sdk-specs #85 defines how a server SDK reports flags that local evaluation could not resolve. Today such a flag is absent from the evaluate_flags() snapshot, so it looks the same as a flag that does not exist, and $feature_flag_called reports flag_missing for both. With only_evaluate_locally=True this is permanent. posthog-node already implements this (PostHog/posthog-js#5234).

This replaces #1033, which was closed as stale. It is rebased on main and adds the spec parts that #1033 did not have.

Changes:

• FeatureFlagEvaluations.unresolved_flags maps each unresolved flag to an UnresolvedFlagReason (experience_continuity, unsupported_definition, unresolved_dependency, missing_context). When several causes apply, the spec's fixed precedence picks one. Snapshots from only() / only_accessed() have no entries, and reading the map is not an access.
• A snapshot read of an unresolved flag reports local_evaluation_inconclusive instead of flag_missing. Values, keys and capture enrichment do not change.
• Every raise site carries an explicit reason, including the regex fallback sites. A bad person value is missing_context; a bad filter value is unsupported_definition.
• When definitions load, the SDK logs a warning (WARNING level) for flags local evaluation can never resolve. Each flag warns once until its definition changes; 304 and unchanged cache loads do not repeat it.
• AsyncClient evaluates only remotely, so its snapshots have no unresolved flags. This is documented.

Behavior changes (in the changeset):

• A condition no longer stops at the first inconclusive filter. If another filter does not match, the condition resolves locally as no match instead of falling back to /flags. A static cohort still forces the fallback only when it is the first filter in its condition that cannot be checked, as in posthog-node.
• An inactive flag with experience continuity now resolves to false locally.
• A flag that depends on a flag with experience continuity no longer resolves locally.

Divergences from the spec or posthog-node:

• A missing group key still resolves to false, as before, so it is not reported as missing_context. posthog-node does the same.
• Regex deferrals that depend on the person value report unsupported_definition but are not in the load-time warning, because the definition alone does not show them.

💚 How did you test it?

Unit tests mirror every scenario tagged @unresolved_flags_capable and @unresolvable_flag_warning_capable in acceptance/public/evaluate-flags.feature, including the device-id row, plus precedence, the condition loop, dependencies, warning pruning and unexpected errors. Run locally:

• pytest --timeout=30. Live AI-provider tests were run with the provider API keys unset.
• ruff format --check ., ruff check ., mypy with the baseline
• make public_api_check

No manual testing in an app.

📝 Checklist

• All commits are signed (see Commit signing)
• 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)

• Written with Claude Code in PostHog Desktop, from a cross-SDK plan to apply sdk-specs chore: Remove upper bound #85 to all server SDKs.
• Started from the feat: report unresolved local flags on evaluate_flags snapshots #1033 commit and resolved its conflicts with main. Then added reasons for the newer regex raise sites, the spec's reason precedence (so a later server error cannot overwrite a higher reason), the condition loop change, dependency checks, the unsupported_definition warning and per-flag pruning of the warning history.

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Created with PostHog Desktop

🤖 Generated with Claude Code

[posthog]

PostHog Review · Standard · reviewed 5572e1c: 3 Should fix. This pull request is large, so the review ran in 4 parts with less depth than usual.

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[github-actions]

posthog-python Compliance Report

Date: 2026-10-28T20:00:33.406868+00:00
Duration: 259408ms

✅ All Tests Passed!

121/121 tests passed

---

Capture_V1 Tests

✅ 95/95 tests passed

View Details

Test	Status	Duration
Endpoint And Method.Targets V1 Endpoint	✅	515ms
Endpoint And Method.Does Not Use Legacy Endpoints	✅	510ms
Required Headers.Has Authorization Bearer Header	✅	509ms
Required Headers.Has Content Type Json	✅	509ms
Required Headers.Has Posthog Sdk Info Format	✅	508ms
Required Headers.Has Posthog Attempt Header	✅	509ms
Required Headers.Has Posthog Request Id	✅	508ms
Required Headers.Has Posthog Request Timestamp	✅	509ms
Required Headers.Has User Agent	✅	508ms
Body Format.Body Has Created At And Batch	✅	508ms
Body Format.No Api Key In Body	✅	509ms
Body Format.No Sent At In Body	✅	508ms
Event Format.Event Has Required Root Fields	✅	508ms
Event Format.Event Uuid Is Valid	✅	509ms
Event Format.Event Timestamp Is Rfc3339	✅	508ms
Event Format.Non Utc Event Timestamp Is Converted To Utc	✅	518ms
Event Format.Distinct Id Is String	✅	509ms
Event Format.Distinct Id At Root Not Properties	✅	508ms
Event Format.Custom Properties Preserved	✅	509ms
Event Format.Set Properties Preserved	✅	509ms
Event Format.Set Once Properties Preserved	✅	508ms
Event Format.Groups Properties Preserved	✅	509ms
Event Format.Sdk Generates Uuid If Not Provided	✅	508ms
Event Format.Event Has Required Root Fields Batch	✅	511ms
Event Format.Event Uuid Is Valid Batch	✅	511ms
Event Format.Event Timestamp Is Rfc3339 Batch	✅	512ms
Event Format.Distinct Id Is String Batch	✅	511ms
Event Format.Distinct Id At Root Not Properties Batch	✅	511ms
Event Format.Custom Properties Preserved Batch	✅	511ms
Event Format.Set Properties Preserved Batch	✅	511ms
Event Format.Set Once Properties Preserved Batch	✅	511ms
Event Format.Groups Properties Preserved Batch	✅	511ms
Event Format.Sdk Generates Uuid If Not Provided Batch	✅	512ms
Batch Behavior.Multiple Events In Single Batch	✅	515ms
Batch Behavior.Batch Envelope Smoke	✅	527ms
Batch Behavior.Flush With No Events Sends Nothing	✅	506ms
Batch Behavior.Flush At Triggers Batch	✅	1010ms
Batch Behavior.Created At Reflects Batch Creation Time	✅	509ms
Deduplication.Generates Unique Uuids	✅	514ms
Deduplication.Different Events Same Content Different Uuids	✅	511ms
Deduplication.Preserves Uuid On Retry	✅	6517ms
Deduplication.Preserves Timestamp On Retry	✅	6514ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	6516ms
Deduplication.No Duplicate Events In Batch	✅	515ms
Header Behavior On Retry.Attempt Header Starts At One	✅	510ms
Header Behavior On Retry.Attempt Header Increments On Retry	✅	13518ms
Header Behavior On Retry.Request Id Preserved On Retry	✅	6518ms
Header Behavior On Retry.Different Requests Have Different Request Ids	✅	3017ms
Header Behavior On Retry.Request Timestamp Changes On Retry	✅	6518ms
Response Format Validation.Success Response Has Uuid Keyed Results	✅	511ms
Response Format Validation.Success Response Has Ok For Each Event	✅	523ms
Response Format Validation.Success No Retry After When All Ok	✅	511ms
Response Format Validation.Success Retry After Present When Retry Events	✅	1513ms
Response Format Validation.Success No Retry After When Drop Only	✅	511ms
Response Format Validation.Response Echoes Request Id	✅	509ms
Retry Behavior.Retries On 408	✅	6512ms
Retry Behavior.Retries On 500	✅	6518ms
Retry Behavior.Retries On 503	✅	8522ms
Retry Behavior.Retries On 504	✅	6517ms
Retry Behavior.Retryable Errors Have Retry After	✅	3515ms
Retry Behavior.Respects Retry After On Retryable Error	✅	11530ms
Retry Behavior.Does Not Retry On 400	✅	2512ms
Retry Behavior.Does Not Retry On 401	✅	2510ms
Retry Behavior.Does Not Retry On 402	✅	2512ms
Retry Behavior.Does Not Retry On 413	✅	2509ms
Retry Behavior.Does Not Retry On 415	✅	2511ms
Retry Behavior.Non Retryable Errors Have No Retry After	✅	2512ms
Retry Behavior.Implements Backoff	✅	22533ms
Retry Behavior.Max Retries Respected	✅	22533ms
Partial Batch Handling.Handles 200 Full Success	✅	2511ms
Partial Batch Handling.Handles 200 With All Ok	✅	3514ms
Partial Batch Handling.Does Not Retry Dropped Events	✅	3511ms
Partial Batch Handling.Does Not Retry Limited Events	✅	3513ms
Partial Batch Handling.Prunes Ok Events On Partial Retry	✅	6516ms
Partial Batch Handling.Prunes Dropped Events On Partial Retry	✅	6519ms
Partial Batch Handling.Retries Only Retry Events From Partial	✅	6521ms
Partial Batch Handling.Partial Retry Preserves Uuids	✅	6515ms
Partial Batch Handling.Partial Retry Attempt Header Increments	✅	6515ms
Partial Batch Handling.Partial Retry Request Id Preserved	✅	6518ms
Partial Batch Handling.Respects Retry After On Partial	✅	8518ms
Partial Batch Handling.Unknown Result Treated As Terminal	✅	3514ms
Partial Batch Handling.Mixed Ok Drop Limited No Retry	✅	3514ms
Compression.Sends Gzip Content Encoding	✅	509ms
Compression.No Content Encoding When Disabled	✅	509ms
Compression.Compressed Body Is Decompressible	✅	508ms
Error Handling.Does Not Retry On Unknown 4Xx	✅	2511ms
Event Options.Cookieless Mode Override	✅	509ms
Event Options.Disable Skew Correction Override	✅	508ms
Event Options.Process Person Profile Override	✅	508ms
Event Options.Product Tour Id Override	✅	509ms
Event Options.Unset Options Omitted	✅	509ms
Event Options.Options Override In Batch	✅	511ms
Geoip And Historical Migration.Geoip Disable Injected Into Properties	✅	508ms
Geoip And Historical Migration.Historical Migration Set In Body	✅	508ms
Geoip And Historical Migration.Historical Migration Absent By Default	✅	508ms

Capture_Ai Tests

✅ 5/5 tests passed

View Details

Test	Status	Duration
Routing.Capture Ai Posts To Ai Endpoint	✅	508ms
Routing.Capture Does Not Reroute Ai Named Events	✅	509ms
Identity.Capture Ai Event Has Uuid	✅	509ms
Identity.Capture Ai Keeps Supplied Uuid	✅	508ms
Timestamp Format.Non Utc Event Timestamp Is Converted To Utc	✅	508ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	9ms
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	✅	10ms
Request Payload.Token In Flags Body Matches Init	✅	7ms
Request Payload.Groups Round Trip	✅	6ms
Request Payload.Groups Default To Empty Object	✅	7ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	7ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	6ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	7ms
Request Lifecycle.No Flags Request On Init Alone	✅	2ms
Request Lifecycle.No Flags Request On Normal Capture	✅	507ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	12ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	7ms
Retry Behavior.Retries Flags On 502	✅	309ms
Retry Behavior.Retries Flags On 504	✅	310ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	509ms

Feature_Flags_Local_Evaluation Tests

✅ 4/4 tests passed

View Details

Test	Status	Duration
Versioned Boolean Matching.Matching Version Missing	✅	49ms
Versioned Boolean Matching.Matching Version 1	✅	46ms
Versioned Boolean Matching.Matching Version 2	✅	47ms
Versioned Boolean Matching.Version Only Reload 1 2 1 2 Missing	✅	24ms

[posthog]

PostHog Review · Standard · reviewed 1bbd5de: no findings. This pull request is large, so the review ran in 4 parts with less depth than usual.

[dustinbyrne]

The added lock-ownership regression test behaves as intended. The known diagnostic-precedence limitation remains a cross-SDK follow-up, as discussed.

AI-assisted review.