feat(analytics): add an early capture filter by sortafreel · Pull Request #1010 · PostHog/posthog-python

sortafreel · 2026-10-06T08:32:38Z

💡 Motivation and Context

Context-based event filtering currently uses before_send, which cleans every allowed event twice even when the filter leaves its payload unchanged.

Add should_capture, a synchronous callback that receives no payload and returns True to allow an event.
Drop rejected events before normalization and cleaning. Callback errors also drop events without logging private contents.
Preserve existing before_send behavior, including support for callbacks that modify events in place.

This adds a public option to Client/Posthog and module configuration. It covers analytics and AI events; AsyncClient, metrics, and tracing spans remain outside its scope. The existing before-send specification stays unchanged; no published spec defines this new option.

💚 How did you test it?

Focused tests cover admission, failure handling, concurrent contexts, existing callbacks, module configuration, fork handling, and v0/v1 transports.
PostHog integration tests passed against the local mirror, including a regular capture alongside a private trial and suppression of trial errors.
API snapshot, formatting, and warning-free SDK import checks passed.
A broader client suite hit a cache-provider shutdown hang, reproduced with the unchanged main implementation.

Local synthetic benchmark using the same candidate SDK, sending disabled, median of seven alternating batches:

Event	No filter	Current `before_send` filter	New early filter
Small	0.033 ms	0.038 ms	0.034 ms
500 nested items	1.261 ms	2.499 ms	1.263 ms

These measure synchronous event preparation, not production throughput. PostHog adoption is prepared and tested locally; it needs a published SDK version before deployment.

📝 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

Added a minor release changeset in .sampo/changesets/.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Agent: Codex, GPT-6. Skills: writing-tests, writing-pr-descriptions. CodeRabbit local review skipped because the CLI is signed out and setup was deferred.

No matching open PR found. All test and benchmark inputs are synthetic; no production traffic or private data was used.

github-actions · 2026-10-06T08:35:45Z

posthog-python Compliance Report

Date: 2026-10-06T09:03:29.229263+00:00
Duration: 259931ms

✅ 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	✅	518ms
Endpoint And Method.Does Not Use Legacy Endpoints	✅	512ms
Required Headers.Has Authorization Bearer Header	✅	510ms
Required Headers.Has Content Type Json	✅	513ms
Required Headers.Has Posthog Sdk Info Format	✅	510ms
Required Headers.Has Posthog Attempt Header	✅	511ms
Required Headers.Has Posthog Request Id	✅	511ms
Required Headers.Has Posthog Request Timestamp	✅	511ms
Required Headers.Has User Agent	✅	511ms
Body Format.Body Has Created At And Batch	✅	510ms
Body Format.No Api Key In Body	✅	511ms
Body Format.No Sent At In Body	✅	510ms
Event Format.Event Has Required Root Fields	✅	511ms
Event Format.Event Uuid Is Valid	✅	511ms
Event Format.Event Timestamp Is Rfc3339	✅	510ms
Event Format.Non Utc Event Timestamp Is Converted To Utc	✅	517ms
Event Format.Distinct Id Is String	✅	510ms
Event Format.Distinct Id At Root Not Properties	✅	511ms
Event Format.Custom Properties Preserved	✅	510ms
Event Format.Set Properties Preserved	✅	511ms
Event Format.Set Once Properties Preserved	✅	511ms
Event Format.Groups Properties Preserved	✅	511ms
Event Format.Sdk Generates Uuid If Not Provided	✅	511ms
Event Format.Event Has Required Root Fields Batch	✅	514ms
Event Format.Event Uuid Is Valid Batch	✅	514ms
Event Format.Event Timestamp Is Rfc3339 Batch	✅	514ms
Event Format.Distinct Id Is String Batch	✅	515ms
Event Format.Distinct Id At Root Not Properties Batch	✅	515ms
Event Format.Custom Properties Preserved Batch	✅	514ms
Event Format.Set Properties Preserved Batch	✅	514ms
Event Format.Set Once Properties Preserved Batch	✅	515ms
Event Format.Groups Properties Preserved Batch	✅	515ms
Event Format.Sdk Generates Uuid If Not Provided Batch	✅	515ms
Batch Behavior.Multiple Events In Single Batch	✅	518ms
Batch Behavior.Batch Envelope Smoke	✅	515ms
Batch Behavior.Flush With No Events Sends Nothing	✅	507ms
Batch Behavior.Flush At Triggers Batch	✅	1012ms
Batch Behavior.Created At Reflects Batch Creation Time	✅	511ms
Deduplication.Generates Unique Uuids	✅	518ms
Deduplication.Different Events Same Content Different Uuids	✅	512ms
Deduplication.Preserves Uuid On Retry	✅	6516ms
Deduplication.Preserves Timestamp On Retry	✅	6521ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	6524ms
Deduplication.No Duplicate Events In Batch	✅	519ms
Header Behavior On Retry.Attempt Header Starts At One	✅	510ms
Header Behavior On Retry.Attempt Header Increments On Retry	✅	13521ms
Header Behavior On Retry.Request Id Preserved On Retry	✅	6521ms
Header Behavior On Retry.Different Requests Have Different Request Ids	✅	3020ms
Header Behavior On Retry.Request Timestamp Changes On Retry	✅	6520ms
Response Format Validation.Success Response Has Uuid Keyed Results	✅	511ms
Response Format Validation.Success Response Has Ok For Each Event	✅	515ms
Response Format Validation.Success No Retry After When All Ok	✅	513ms
Response Format Validation.Success Retry After Present When Retry Events	✅	1517ms
Response Format Validation.Success No Retry After When Drop Only	✅	513ms
Response Format Validation.Response Echoes Request Id	✅	510ms
Retry Behavior.Retries On 408	✅	6520ms
Retry Behavior.Retries On 500	✅	6520ms
Retry Behavior.Retries On 503	✅	8520ms
Retry Behavior.Retries On 504	✅	6520ms
Retry Behavior.Retryable Errors Have Retry After	✅	3516ms
Retry Behavior.Respects Retry After On Retryable Error	✅	11522ms
Retry Behavior.Does Not Retry On 400	✅	2514ms
Retry Behavior.Does Not Retry On 401	✅	2514ms
Retry Behavior.Does Not Retry On 402	✅	2513ms
Retry Behavior.Does Not Retry On 413	✅	2513ms
Retry Behavior.Does Not Retry On 415	✅	2514ms
Retry Behavior.Non Retryable Errors Have No Retry After	✅	2514ms
Retry Behavior.Implements Backoff	✅	22523ms
Retry Behavior.Max Retries Respected	✅	22537ms
Partial Batch Handling.Handles 200 Full Success	✅	2512ms
Partial Batch Handling.Handles 200 With All Ok	✅	3518ms
Partial Batch Handling.Does Not Retry Dropped Events	✅	3516ms
Partial Batch Handling.Does Not Retry Limited Events	✅	3516ms
Partial Batch Handling.Prunes Ok Events On Partial Retry	✅	6522ms
Partial Batch Handling.Prunes Dropped Events On Partial Retry	✅	6522ms
Partial Batch Handling.Retries Only Retry Events From Partial	✅	6523ms
Partial Batch Handling.Partial Retry Preserves Uuids	✅	6518ms
Partial Batch Handling.Partial Retry Attempt Header Increments	✅	6521ms
Partial Batch Handling.Partial Retry Request Id Preserved	✅	6522ms
Partial Batch Handling.Respects Retry After On Partial	✅	8521ms
Partial Batch Handling.Unknown Result Treated As Terminal	✅	3514ms
Partial Batch Handling.Mixed Ok Drop Limited No Retry	✅	3519ms
Compression.Sends Gzip Content Encoding	✅	511ms
Compression.No Content Encoding When Disabled	✅	511ms
Compression.Compressed Body Is Decompressible	✅	510ms
Error Handling.Does Not Retry On Unknown 4Xx	✅	2513ms
Event Options.Cookieless Mode Override	✅	510ms
Event Options.Disable Skew Correction Override	✅	510ms
Event Options.Process Person Profile Override	✅	510ms
Event Options.Product Tour Id Override	✅	510ms
Event Options.Unset Options Omitted	✅	510ms
Event Options.Options Override In Batch	✅	514ms
Geoip And Historical Migration.Geoip Disable Injected Into Properties	✅	511ms
Geoip And Historical Migration.Historical Migration Set In Body	✅	510ms
Geoip And Historical Migration.Historical Migration Absent By Default	✅	510ms

Capture_Ai Tests

✅ 5/5 tests passed

View Details

Test	Status	Duration
Routing.Capture Ai Posts To Ai Endpoint	✅	510ms
Routing.Capture Does Not Reroute Ai Named Events	✅	510ms
Identity.Capture Ai Event Has Uuid	✅	510ms
Identity.Capture Ai Keeps Supplied Uuid	✅	510ms
Timestamp Format.Non Utc Event Timestamp Is Converted To Utc	✅	511ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	11ms
Request Payload.Flags Request Uses V2 Query Param	✅	9ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	9ms
Request Payload.Flags Request Omits Authorization Header	✅	9ms
Request Payload.Token In Flags Body Matches Init	✅	9ms
Request Payload.Groups Round Trip	✅	9ms
Request Payload.Groups Default To Empty Object	✅	9ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	9ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	9ms
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	✅	509ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	14ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	9ms
Retry Behavior.Retries Flags On 502	✅	313ms
Retry Behavior.Retries Flags On 504	✅	313ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	511ms

Feature_Flags_Local_Evaluation Tests

✅ 4/4 tests passed

View Details

Test	Status	Duration
Versioned Boolean Matching.Matching Version Missing	✅	69ms
Versioned Boolean Matching.Matching Version 1	✅	68ms
Versioned Boolean Matching.Matching Version 2	✅	68ms
Versioned Boolean Matching.Version Only Reload 1 2 1 2 Missing	✅	34ms

greptile-apps · 2026-10-06T08:35:56Z

[Medium risk] Adds optional event filtering callback to analytics client.

The PR should not merge until rejected captures avoid feature-flag requests.

_{Reviews (1) · Last reviewed commit: "feat(analytics): add an early capture fi..."}

posthog · 2026-10-06T08:40:29Z

🦔 PostHog Review reviewed this pull request

Found 0 must fix, 1 should fix, 0 consider.

Published 1 finding (view the review).

Resolved comments: 2 fixed, 1 declined

posthog · 2026-10-06T08:51:27Z

PostHog Review alpha 🦔 If you find any issues helpful - please reply "valid", "invalid", etc., for evaluation purposes 🙏

posthog

PostHog Review

Found 1 should fix.

Only mark a $feature_flag_called event as reported when capture() returns an event UUID. A should_capture rejection no longer suppresses the same exposure from a later allowed context on the shared client. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Generated-By: PostHog Desktop Task-Id: bdf93d58-c0c1-4a15-a1e6-78b6a3944b02

capture() and capture_ai() now check the should_capture callback before they build the event or evaluate send_feature_flags. A rejected event no longer makes a /flags request. set, set_once, alias, and group_identify still apply the callback in _enqueue, and it runs once per event. Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com> Generated-By: PostHog Desktop Task-Id: bdf93d58-c0c1-4a15-a1e6-78b6a3944b02

feat(analytics): add an early capture filter

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sortafreel self-assigned this Oct 6, 2026

greptile-apps Bot reviewed Oct 6, 2026

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Comment thread posthog/test/test_should_capture.py

posthog Bot reviewed Oct 6, 2026

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Comment thread posthog/client.py Outdated

posthog Bot added 2 commits October 6, 2026 08:55

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feat(analytics): add an early capture filter - #1010

feat(analytics): add an early capture filter#1010
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sortafreel commented Oct 6, 2026

💡 Motivation and Context

💚 How did you test it?

📝 Checklist

If releasing new changes

🤖 Agent context

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posthog-python Compliance Report

✅ All Tests Passed!

Capture_V1 Tests

Capture_Ai Tests

Feature_Flags Tests

Feature_Flags_Local_Evaluation Tests

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