feat!: per-event capture options and legacy property hoisting

[eli-r-ph]

💡 Motivation and Context

Capture v1 sends processing options (process_person_profile, cookieless_mode, disable_skew_correction, product_tour_id) in a per-event options object. Until now the SDK only filled it from legacy $ properties, coerced the values, and gave callers no way to set options directly. posthog-go and posthog-rs v1 already take per-event options and send them as given.

New options argument on capture, capture_ai, set, set_once, group_identify, alias and capture_exception, on Client, AsyncPosthog and the module-level functions. For example: posthog.capture("signed_up", distinct_id=..., options={"cookieless_mode": True}).

Behavior changes:

• Options are sent as given. The SDK checks neither keys nor value types; PostHog validates them. Unknown keys pass through. A value that is not a dict is logged as an error, and the event is sent without it.
• Legacy properties are no longer coerced. $cookieless_mode, $ignore_sent_at, $product_tour_id and $process_person_profile still fill the matching option, unchanged. Before, "true" became True and an unparseable value was dropped. The property is always removed from properties.
• An option wins over its legacy property. A null option counts as unset, so the property fills it. This matches go and rs.
• The legacy properties move into options once, after before_send. That was already the case. before_send now also sees options and can change it.
• Event uuids accept only the forms other SDKs accept:
  • hyphenated, 32 hex, {...} braced and urn:uuid: in any case; each is canonicalized
  • anything else, such as Python's uuid: prefix or misplaced hyphens, is replaced with a generated uuid and logged
  • this now applies to AsyncPosthog too, which before accepted anything uuid.UUID() parses
• Minimal $feature_flag_called events keep $cookieless_mode, $ignore_sent_at, $product_tour_id and $window_id. The allowlist runs before the legacy properties move into options, so these were dropped and their options lost. posthog-go has the same fix in feat!: add default and request-context options; event values win over defaults posthog-go#359.

Not in this PR: global and context options, the layer-order change, and the personless option (next PR in the stack), and AI wrappers and MCP moving to options (the one after).

💚 How did you test it?

• Wire builder:
  • each legacy property fills its option unchanged
  • option vs legacy, with the option set, null or missing
  • unknown options pass through
  • a non-dict is logged and ignored
  • the input is not mutated
  • accepted and rejected uuid forms
• Clients: new test_event_options.py. It checks that options reaches the wire from every method on Client and AsyncPosthog. A before_send that returns a new event can change options and remove a legacy property. A non-dict options is logged and the event is still sent.
• Minimal flag events: a gated event with legacy option super properties keeps the options and window_id.
• Break-on-purpose: each of these was reverted in turn, and the matching test failed every time:
  • the legacy property winning
  • alias dropping options
  • the four allowlist keys
  • lenient uuid parsing
  • async capture dropping options
  • sync and async ignoring the hook's options
• I ran ruff, mypy (baseline), the strict type smoke, the full pytest suite, the adapter tests, python -W error -c "import posthog", the public API snapshot and uv lock --check.

📝 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

Covered by the existing capture-v1-major changeset; the migration guide lands later in this stack.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Written with Cursor (Claude Opus) under the direction of the assignee.

Agreed before implementation:

• options pass through unchanged
• non-dict options logged and ignored
• only string $session_id/$window_id move to top-level fields
• hoisting once, after before_send
• an option wins over its legacy property
• the uuid forms, matching posthog-go uuid.Validate

Agent calls worth review:

• the queued message always carries options (maybe {}), so before_send sees the key
• a null legacy property still fills an unset option as null, as in posthog-rs

[github-actions]

posthog-python Compliance Report

Date: 2026-10-07T02:08:45.202684+00:00
Duration: 246900ms

✅ All Tests Passed!

116/116 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	✅	509ms
Required Headers.Has Authorization Bearer Header	✅	508ms
Required Headers.Has Content Type Json	✅	509ms
Required Headers.Has Posthog Sdk Info Format	✅	509ms
Required Headers.Has Posthog Attempt Header	✅	508ms
Required Headers.Has Posthog Request Id	✅	509ms
Required Headers.Has Posthog Request Timestamp	✅	508ms
Required Headers.Has User Agent	✅	509ms
Body Format.Body Has Created At And Batch	✅	510ms
Body Format.No Api Key In Body	✅	508ms
Body Format.No Sent At In Body	✅	508ms
Event Format.Event Has Required Root Fields	✅	509ms
Event Format.Event Uuid Is Valid	✅	509ms
Event Format.Event Timestamp Is Rfc3339	✅	509ms
Event Format.Non Utc Event Timestamp Is Converted To Utc	✅	513ms
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	✅	510ms
Event Format.Set Once Properties Preserved	✅	508ms
Event Format.Groups Properties Preserved	✅	511ms
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	✅	511ms
Event Format.Distinct Id Is String Batch	✅	512ms
Event Format.Distinct Id At Root Not Properties Batch	✅	511ms
Event Format.Custom Properties Preserved Batch	✅	510ms
Event Format.Set Properties Preserved Batch	✅	512ms
Event Format.Set Once Properties Preserved Batch	✅	511ms
Event Format.Groups Properties Preserved Batch	✅	511ms
Event Format.Sdk Generates Uuid If Not Provided Batch	✅	511ms
Batch Behavior.Multiple Events In Single Batch	✅	514ms
Batch Behavior.Batch Envelope Smoke	✅	513ms
Batch Behavior.Flush With No Events Sends Nothing	✅	505ms
Batch Behavior.Flush At Triggers Batch	✅	1009ms
Batch Behavior.Created At Reflects Batch Creation Time	✅	509ms
Deduplication.Generates Unique Uuids	✅	515ms
Deduplication.Different Events Same Content Different Uuids	✅	510ms
Deduplication.Preserves Uuid On Retry	✅	6517ms
Deduplication.Preserves Timestamp On Retry	✅	6518ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	6520ms
Deduplication.No Duplicate Events In Batch	✅	515ms
Header Behavior On Retry.Attempt Header Starts At One	✅	509ms
Header Behavior On Retry.Attempt Header Increments On Retry	✅	12519ms
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	✅	510ms
Response Format Validation.Success Response Has Ok For Each Event	✅	512ms
Response Format Validation.Success No Retry After When All Ok	✅	510ms
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	✅	6517ms
Retry Behavior.Retries On 500	✅	6518ms
Retry Behavior.Retries On 503	✅	7519ms
Retry Behavior.Retries On 504	✅	6518ms
Retry Behavior.Retryable Errors Have Retry After	✅	3514ms
Retry Behavior.Respects Retry After On Retryable Error	✅	11522ms
Retry Behavior.Does Not Retry On 400	✅	2512ms
Retry Behavior.Does Not Retry On 401	✅	2511ms
Retry Behavior.Does Not Retry On 402	✅	2512ms
Retry Behavior.Does Not Retry On 413	✅	2512ms
Retry Behavior.Does Not Retry On 415	✅	2510ms
Retry Behavior.Non Retryable Errors Have No Retry After	✅	2512ms
Retry Behavior.Implements Backoff	✅	18526ms
Retry Behavior.Max Retries Respected	✅	18526ms
Partial Batch Handling.Handles 200 Full Success	✅	2510ms
Partial Batch Handling.Handles 200 With All Ok	✅	3515ms
Partial Batch Handling.Does Not Retry Dropped Events	✅	3512ms
Partial Batch Handling.Does Not Retry Limited Events	✅	3514ms
Partial Batch Handling.Prunes Ok Events On Partial Retry	✅	6519ms
Partial Batch Handling.Prunes Dropped Events On Partial Retry	✅	6515ms
Partial Batch Handling.Retries Only Retry Events From Partial	✅	6521ms
Partial Batch Handling.Partial Retry Preserves Uuids	✅	6519ms
Partial Batch Handling.Partial Retry Attempt Header Increments	✅	6515ms
Partial Batch Handling.Partial Retry Request Id Preserved	✅	6515ms
Partial Batch Handling.Respects Retry After On Partial	✅	8517ms
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	✅	508ms
Compression.Compressed Body Is Decompressible	✅	509ms
Error Handling.Does Not Retry On Unknown 4Xx	✅	2511ms
Event Options.Cookieless Mode Override	✅	509ms
Event Options.Disable Skew Correction Override	✅	509ms
Event Options.Process Person Profile Override	✅	508ms
Event Options.Product Tour Id Override	✅	508ms
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	✅	509ms

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	✅	8ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	7ms
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	✅	7ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	7ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	8ms
Request Lifecycle.No Flags Request On Init Alone	✅	2ms
Request Lifecycle.No Flags Request On Normal Capture	✅	508ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	11ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	7ms
Retry Behavior.Retries Flags On 502	✅	310ms
Retry Behavior.Retries Flags On 504	✅	311ms
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	✅	54ms
Versioned Boolean Matching.Matching Version 1	✅	60ms
Versioned Boolean Matching.Matching Version 2	✅	56ms
Versioned Boolean Matching.Version Only Reload 1 2 1 2 Missing	✅	27ms