[rodrigoi]

Problem

Funnel (#61796) and mean (#62291) metrics attribute breakdowns from the metric event. Retention metrics still use the exposure-event injector.

Changes

This PR migrates retention metrics to MetricBreakdownInjector, behind the same flag.

Retention support in the injector

The breakdown is read off the start event and attributed first touch (argMin over the start event timestamp). Attribution is fixed with no user choice, and that's deliberate: retention is retained / cohort, the cohort (denominator) is defined by the start event, and every retained user has one. Reading the breakdown off the completion event would break the per-bucket denominator, since non-retained users have no completion event to bucket by. start_events already groups by entity, so the value is deduped per user there and carried into entity_metrics.

• products/experiments/backend/hogql_queries/metric_breakdown_injector.py
• products/experiments/backend/hogql_queries/experiment_query_runner.py
• products/experiments/backend/hogql_queries/experiment_retention_query_builder.py

Tests

Flag-on retention cases in test_metric_breakdown.py (start-event attribution, limit, Other bucket) plus injector unit tests.

• products/experiments/backend/hogql_queries/test/experiment_query_runner/test_metric_breakdown.py
• products/experiments/backend/hogql_queries/test/test_metric_breakdown_injector.py

How did you test this code?

pnpm turbo run backend:test --filter=@posthog/products-experiments

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

Automatic notifications

• Publish to changelog?
• Alert Sales and Marketing teams?

Docs update

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Model: Opus 4.7 (implementation), Fable 5 (restack and PR description)
Manually refactored: yes

Skills used:

• /writing-tests (local)
• /writing-pull-requests (local)

Relevant decisions:

• Start-event attribution is the only source that keeps the per-bucket denominator well-defined, so no attribution dropdown is offered for retention.

[rodrigoi]

Warning

This pull request is not mergeable via GitHub because a downstack PR is open. Once all requirements are satisfied, merge this PR as a stack on Graphite.
Learn more

• feat(experiments): add ratio metrics to the metric breakdown injector #62293
• feat(experiments): add retention metrics to the metric breakdown injector #62292 👈 (View in Graphite)
• feat(experiments): add metric breakdown injector for mean metrics #62291
• feat(experiments): add metric breakdown injector for funnels #61796
• feat(experiments): add breakdown attribution to the metric row group #61788
• master

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[greptile-apps]

Comments Outside Diff (1)

1. products/experiments/backend/hogql_queries/metric_breakdown_injector.py, line 1-13 (link)

   Stale module-level docstring

   The module header still says "Scope: funnel metrics only" and "Metric-event breakdown injection for experiment funnel queries," but the class has been extended to handle mean, ratio, and now retention metrics. Any new reader will come away with an inaccurate mental model of the file's scope.

   Prompt To Fix With AI

   This is a comment left during a code review.
   Path: products/experiments/backend/hogql_queries/metric_breakdown_injector.py
   Line: 1-13
   
   Comment:
   **Stale module-level docstring**
   
   The module header still says "Scope: funnel metrics only" and "Metric-event breakdown injection for experiment funnel queries," but the class has been extended to handle mean, ratio, and now retention metrics. Any new reader will come away with an inaccurate mental model of the file's scope.
   
   How can I resolve this? If you propose a fix, please make it concise.

   Note: If this suggestion doesn't match your team's coding style, reply to this and let me know. I'll remember it for next time!

Prompt To Fix All With AI

Fix the following 1 code review issue. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 1
products/experiments/backend/hogql_queries/metric_breakdown_injector.py:1-13
**Stale module-level docstring**

The module header still says "Scope: funnel metrics only" and "Metric-event breakdown injection for experiment funnel queries," but the class has been extended to handle mean, ratio, and now retention metrics. Any new reader will come away with an inaccurate mental model of the file's scope.

_{Reviews (1): Last reviewed commit: "feat(experiments): add ratio metrics to ..." | Re-trigger Greptile}

[trunk-io]

   

View Full Report ↗︎ ⋅ Docs

[andehen]

Findings from a review of the full stack (#61788, #61796, #62291, #62292, #62293), placed on the PR where each belongs. Prefixes: should-fix, suggestion, nit. Only one small thing here, the retention path is the most solid of the four (breakdown read off the start event keeps the per-bucket denominator well defined, and the non-retained-users test covers it).

[scheduled-actions-posthog]

This PR hasn't seen activity in a week! Should it be merged, closed, or further worked on? If you want to keep it open, please remove the stale label – otherwise this will be closed in another week. If you want to permanently keep it open, use the waiting label.

[scheduled-actions-posthog]

This PR hasn't seen activity in a week! Should it be merged, closed, or further worked on? If you want to keep it open, please remove the stale label – otherwise this will be closed in another week. If you want to permanently keep it open, use the waiting label.

[scheduled-actions-posthog]

This PR hasn't seen activity in a week! Should it be merged, closed, or further worked on? If you want to keep it open, please remove the stale label – otherwise this will be closed in another week. If you want to permanently keep it open, use the waiting label.