feat(metrics): support metrics config via module-level settings

[DanielVisca]

💡 Motivation and Context

Apps configured through module attributes (posthog.api_key = ... + implicit setup()) — including PostHog's own Django monorepo via posthoganalytics — have no way to pass the metrics config dict. Every series they record through client.metrics ships service.name='unknown_service', which defeats the Metrics UI's service filtering.

This adds the module-level metrics attr (mirroring how every other Client kwarg is exposed as a module setting) and passes it through setup(). Because the config is consumed lazily on first .metrics access, a repeat setup() call also refreshes it until the metrics API is first used — Django ready() hooks that run after something already forced setup() still apply.

Groundwork for the monorepo's bump-ready client.metrics usage from web/celery (companion PR in PostHog/posthog).

💚 How did you test it?

• Two new tests in posthog/test/test_metrics.py, red before the change (service.name came back unknown_service): module attr flows into the setup() client's OTLP resource attributes, and late assignment applies on repeat setup() until first use.
• pytest --timeout=30: 1640 passed; the 9 failures are the pre-existing network-dependent posthog/test/ai/* integration tests (verified they fail identically on a clean checkout in the same sandbox).
• ruff format --check, ruff check, mypy | mypy-baseline filter (no issues), python -W error -c "import posthog" all clean.
• End to end: with this patch, a module-configured client in a forked child (celery-prefork shape) recorded and flushed real metrics that arrived in the Metrics product with the configured service name.

📝 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 (authored directly in .sampo/changesets/module-level-metrics-config.md — same format)

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Written by Claude (PostHog Code session) while making the PostHog monorepo bump-ready for client.metrics. TDD: the two tests were written and observed failing before the implementation. The late-assignment refresh in setup() follows the existing "always set in case user changes it" post-construction block, and is limited to before first .metrics use so an active aggregation window is never reconfigured mid-flight.

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Created with PostHog Code

[github-actions]

posthog-python Compliance Report

Date: 2026-07-20 22:51:23 UTC
Duration: 338827ms

✅ All Tests Passed!

111/111 tests passed

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Capture_V1 Tests

✅ 94/94 tests passed

View Details

Test	Status	Duration
Endpoint And Method.Targets V1 Endpoint	✅	516ms
Endpoint And Method.Does Not Use Legacy Endpoints	✅	1009ms
Required Headers.Has Authorization Bearer Header	✅	1009ms
Required Headers.Has Content Type Json	✅	1008ms
Required Headers.Has Posthog Sdk Info Format	✅	1008ms
Required Headers.Has Posthog Attempt Header	✅	1008ms
Required Headers.Has Posthog Request Id	✅	1009ms
Required Headers.Has Posthog Request Timestamp	✅	1007ms
Required Headers.Has User Agent	✅	1007ms
Body Format.Body Has Created At And Batch	✅	1007ms
Body Format.No Api Key In Body	✅	1009ms
Body Format.No Sent At In Body	✅	1008ms
Event Format.Event Has Required Root Fields	✅	1008ms
Event Format.Event Uuid Is Valid	✅	1008ms
Event Format.Event Timestamp Is Rfc3339	✅	1009ms
Event Format.Distinct Id Is String	✅	1008ms
Event Format.Distinct Id At Root Not Properties	✅	1008ms
Event Format.Custom Properties Preserved	✅	1009ms
Event Format.Set Properties Preserved	✅	1008ms
Event Format.Set Once Properties Preserved	✅	1009ms
Event Format.Groups Properties Preserved	✅	1008ms
Event Format.Sdk Generates Uuid If Not Provided	✅	1008ms
Event Format.Event Has Required Root Fields Batch	✅	1012ms
Event Format.Event Uuid Is Valid Batch	✅	1012ms
Event Format.Event Timestamp Is Rfc3339 Batch	✅	1012ms
Event Format.Distinct Id Is String Batch	✅	1012ms
Event Format.Distinct Id At Root Not Properties Batch	✅	1011ms
Event Format.Custom Properties Preserved Batch	✅	1012ms
Event Format.Set Properties Preserved Batch	✅	1012ms
Event Format.Set Once Properties Preserved Batch	✅	1013ms
Event Format.Groups Properties Preserved Batch	✅	1012ms
Event Format.Sdk Generates Uuid If Not Provided Batch	✅	1012ms
Batch Behavior.Multiple Events In Single Batch	✅	1507ms
Batch Behavior.Batch Envelope Smoke	✅	1014ms
Batch Behavior.Flush With No Events Sends Nothing	✅	1005ms
Batch Behavior.Flush At Triggers Batch	✅	1507ms
Batch Behavior.Created At Reflects Batch Creation Time	✅	1011ms
Deduplication.Generates Unique Uuids	✅	1507ms
Deduplication.Different Events Same Content Different Uuids	✅	1506ms
Deduplication.Preserves Uuid On Retry	✅	7516ms
Deduplication.Preserves Timestamp On Retry	✅	7506ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7512ms
Deduplication.No Duplicate Events In Batch	✅	1507ms
Header Behavior On Retry.Attempt Header Starts At One	✅	1009ms
Header Behavior On Retry.Attempt Header Increments On Retry	✅	14515ms
Header Behavior On Retry.Request Id Preserved On Retry	✅	7515ms
Header Behavior On Retry.Different Requests Have Different Request Ids	✅	3515ms
Header Behavior On Retry.Request Timestamp Changes On Retry	✅	7514ms
Response Format Validation.Success Response Has Uuid Keyed Results	✅	1005ms
Response Format Validation.Success Response Has Ok For Each Event	✅	1506ms
Response Format Validation.Success No Retry After When All Ok	✅	1507ms
Response Format Validation.Success Retry After Present When Retry Events	✅	2509ms
Response Format Validation.Success No Retry After When Drop Only	✅	1507ms
Response Format Validation.Response Echoes Request Id	✅	1009ms
Retry Behavior.Retries On 408	✅	7514ms
Retry Behavior.Retries On 500	✅	7508ms
Retry Behavior.Retries On 503	✅	9514ms
Retry Behavior.Retries On 504	✅	7512ms
Retry Behavior.Retryable Errors Have Retry After	✅	4513ms
Retry Behavior.Respects Retry After On Retryable Error	✅	12516ms
Retry Behavior.Does Not Retry On 400	✅	3503ms
Retry Behavior.Does Not Retry On 401	✅	3508ms
Retry Behavior.Does Not Retry On 402	✅	3507ms
Retry Behavior.Does Not Retry On 413	✅	3506ms
Retry Behavior.Does Not Retry On 415	✅	3508ms
Retry Behavior.Non Retryable Errors Have No Retry After	✅	3508ms
Retry Behavior.Implements Backoff	✅	23520ms
Retry Behavior.Max Retries Respected	✅	23520ms
Partial Batch Handling.Handles 200 Full Success	✅	3012ms
Partial Batch Handling.Handles 200 With All Ok	✅	4508ms
Partial Batch Handling.Does Not Retry Dropped Events	✅	4508ms
Partial Batch Handling.Does Not Retry Limited Events	✅	4506ms
Partial Batch Handling.Prunes Ok Events On Partial Retry	✅	7515ms
Partial Batch Handling.Prunes Dropped Events On Partial Retry	✅	7512ms
Partial Batch Handling.Retries Only Retry Events From Partial	✅	7508ms
Partial Batch Handling.Partial Retry Preserves Uuids	✅	7515ms
Partial Batch Handling.Partial Retry Attempt Header Increments	✅	7506ms
Partial Batch Handling.Partial Retry Request Id Preserved	✅	7516ms
Partial Batch Handling.Respects Retry After On Partial	✅	9512ms
Partial Batch Handling.Unknown Result Treated As Terminal	✅	4506ms
Partial Batch Handling.Mixed Ok Drop Limited No Retry	✅	4508ms
Compression.Sends Gzip Content Encoding	✅	1007ms
Compression.No Content Encoding When Disabled	✅	1008ms
Compression.Compressed Body Is Decompressible	✅	1009ms
Error Handling.Does Not Retry On Unknown 4Xx	✅	3508ms
Event Options.Cookieless Mode Override	✅	1007ms
Event Options.Disable Skew Correction Override	✅	1008ms
Event Options.Process Person Profile Override	✅	1008ms
Event Options.Product Tour Id Override	✅	1009ms
Event Options.Unset Options Omitted	✅	1008ms
Event Options.Options Override In Batch	✅	1012ms
Geoip And Historical Migration.Geoip Disable Injected Into Properties	✅	1008ms
Geoip And Historical Migration.Historical Migration Set In Body	✅	1008ms
Geoip And Historical Migration.Historical Migration Absent By Default	✅	1008ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	1005ms
Request Payload.Flags Request Uses V2 Query Param	✅	1006ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	1006ms
Request Payload.Flags Request Omits Authorization Header	✅	1006ms
Request Payload.Token In Flags Body Matches Init	✅	1006ms
Request Payload.Groups Round Trip	✅	1006ms
Request Payload.Groups Default To Empty Object	✅	1006ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	1006ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	1006ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	1006ms
Request Lifecycle.No Flags Request On Init Alone	✅	503ms
Request Lifecycle.No Flags Request On Normal Capture	✅	1507ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	1009ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	1003ms
Retry Behavior.Retries Flags On 502	✅	1005ms
Retry Behavior.Retries Flags On 504	✅	1007ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	1508ms

[greptile-apps]

_{Reviews (1): Last reviewed commit: "chore: add changeset for module-level me..." | Re-trigger Greptile}

[DanielVisca]

sdk-dustin review — single pass

Fully automated AI review; comments were not individually reviewed by a human before posting. Applied sdk-dustin-code-review + sdk-dustin-sdk-review (single pass + calibration, per author request — no fix loop needed).

Verdict

APPROVE (agent pre-review; Client Libraries review still required) — no BLOCKING/IMPORTANT findings. One design question flagged below for a deliberate call before this ships in a minor release.

Existing supported workaround / API necessity

• Desired outcome: module-configured apps (posthog.api_key = ... + implicit setup()) pass the metrics config so series don't ship service.name='unknown_service'.
• Mechanisms searched: all module attrs mirrored into setup(); direct client construction; post-hoc mutation of default_client.
• Strongest workaround: posthog.default_client = Client(api_key, metrics={...}) — validated against the checkout, but it bypasses setup()'s wiring (disabled/debug/before_send sync with module attrs), so workaround exists but has meaningful gaps.
• Conclusion: the addition follows the SDK's uniform convention (every Client kwarg is exposed as a same-named module setting); justified. But see the naming flag.

Review comment drafts

[P2/design] posthog.metrics as a config attr spends the natural name of a future module-level metrics API.
posthog/__init__.py:381. The module exposes client APIs as proxy functions (posthog.capture(...), posthog.flush(...)); there is no metrics accessor yet. If one is ever added, the ergonomic, posthog-js-mirroring name is posthog.metrics.count(...) — which this attr forecloses: after this ships (minor release), posthog.metrics is publicly a Optional[dict], and posthog.metrics.count is an AttributeError on None. The kwarg-mirroring convention argues for the current name; reserving the accessor name argues for e.g. a metrics key consumed from a differently-named attr, or accepting that module-level users will always go through setup().metrics. Consider making this an explicit decision (a one-line note in the changeset would do) rather than an accident of convention.

Criteria summary

• Backwards compatibility ✅ — pure addition; default None preserves existing behavior; snapshot updated.
• API surface ⚠️ one new public module attr (see design flag); consistent with the established kwarg-mirroring pattern.
• Entry-point tracing ✅ — setup() fresh-construct path passes the kwarg; repeat-setup() path applies via _metrics_config only while _metrics is None, matching the documented "until first use" contract. (The guard is belt-and-braces: config is only read at first .metrics access anyway.)
• Performance ✅ — config plumbing only.
• Test coverage ✅ — both paths executed locally (fresh setup + late assignment), module state restored; 36/36 suite green on this branch.
• No throwing ✅ — invalid dicts degrade inside PostHogMetrics (hardened further by fix(metrics): harden attribute snapshots, retry backoff, and config validation #742).
• Cross-SDK parity ✅/note — posthog-js configures metrics at init too; the naming flag above is where parity pressure will eventually appear.

Non-blocking observations

• This branch predates fix(metrics): harden attribute snapshots, retry backoff, and config validation #742's metrics hardening; both PRs edit test_metrics.py in disjoint regions, so whichever merges second should rebase clean (merge fix(metrics): harden attribute snapshots, retry backoff, and config validation #742 first — it's further along).
• Concurrent first-.metrics access racing a repeat setup() can silently drop the late config — same outcome as the documented "already used" case; startup-time only, not material.

[dustinbyrne]

recommend adding a client constructor argument for this as well

otherwise, users who don't use the default global posthog cannot set this (unless it already exists, i didn't check). if you do add it, make sure it's positioned as the last argument in the constructor for backwards compatibility

[DanielVisca]

recommend adding a client constructor argument for this as well

otherwise, users who don't use the default global posthog cannot set this (unless it already exists, i didn't check). if you do add it, make sure it's positioned as the last argument in the constructor for backwards compatibility

Already there 👍🏽