fix: improve strict public API types

[marandaneto]

💡 Motivation and Context

Strict Pyright users could still hit partially unknown types when accessing public PostHog APIs, even after the issue-specific Posthog.shutdown path was fixed.

Fixes #559.

💚 How did you test it?

• Compared the SDK event-facing types against the capture /batch/ backend contract in rust/capture/src/v0_request.rs and rust/common/types/src/event.rs. The SDK intentionally keeps some wrapper timestamp types stricter than the backend accepts.
• python -m mypy --config-file mypy.ini posthog/client.py posthog/__init__.py
• uv run ruff check posthog/client.py posthog/__init__.py
• uv run --extra dev python .github/scripts/check_public_api.py
• uv run --extra test pytest posthog/test/test_feature_flag.py posthog/test/test_feature_flag_result.py posthog/test/test_module.py::TestModule::test_flush
• .github/scripts/check_strict_types.sh
• Added a CI Strict type smoke job that runs .github/scripts/check_strict_types.sh. The script installs the package into a temporary downstream venv, runs strict Pyright against representative public API usage, and checks all public client/module function member access for unknown types.

📝 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

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

An AI coding agent investigated the strict typing gaps around #559, identified remaining Pyright Unknown types on public APIs, and made a typing-only fix. The changes focus on explicit public signatures in posthog.client.Client and the module-level wrappers in posthog.__init__, plus a patch changeset for release notes and a strict downstream Pyright smoke check in CI.

[greptile-apps]

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
posthog/__init__.py:62-67
`FlagValue` is imported without the `as FlagValue` explicit re-export form, so strict Pyright will still raise `reportPrivateImportUsage` when downstream users write `from posthog import FlagValue` to annotate variables holding the return value of `get_feature_flag()` or `get_all_flags()`. Every other intentionally public type in this block uses the `X as X` pattern (`BeforeSendCallback as BeforeSendCallback`, `FeatureFlag as FeatureFlag`); `FlagValue` should match.

```suggestion
from posthog.types import (
    BeforeSendCallback as BeforeSendCallback,
    FeatureFlag as FeatureFlag,
    FlagValue as FlagValue,
    FlagsAndPayloads,
)
```

_{Reviews (1): Last reviewed commit: "fix: improve strict public API types" | Re-trigger Greptile}

[github-actions]

posthog-python Compliance Report

Date: 2026-06-19 14:10:23 UTC
Duration: 540099ms

✅ All Tests Passed!

45/45 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	517ms
Format Validation.Event Has Uuid	✅	10007ms
Format Validation.Event Has Lib Properties	✅	10007ms
Format Validation.Distinct Id Is String	✅	10007ms
Format Validation.Token Is Present	✅	10007ms
Format Validation.Custom Properties Preserved	✅	10007ms
Format Validation.Event Has Timestamp	✅	10007ms
Retry Behavior.Retries On 503	✅	18019ms
Retry Behavior.Does Not Retry On 400	✅	12005ms
Retry Behavior.Does Not Retry On 401	✅	10006ms
Retry Behavior.Respects Retry After Header	✅	16014ms
Retry Behavior.Implements Backoff	✅	32028ms
Retry Behavior.Retries On 500	✅	16000ms
Retry Behavior.Retries On 502	✅	16009ms
Retry Behavior.Retries On 504	✅	16008ms
Retry Behavior.Max Retries Respected	✅	32032ms
Deduplication.Generates Unique Uuids	✅	9994ms
Deduplication.Preserves Uuid On Retry	✅	16014ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	23019ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	16006ms
Deduplication.No Duplicate Events In Batch	✅	10001ms
Deduplication.Different Events Have Different Uuids	✅	10007ms
Compression.Sends Gzip When Enabled	✅	10007ms
Batch Format.Uses Proper Batch Structure	✅	10007ms
Batch Format.Flush With No Events Sends Nothing	✅	5005ms
Batch Format.Multiple Events Batched Together	✅	10005ms
Error Handling.Does Not Retry On 403	✅	12010ms
Error Handling.Does Not Retry On 413	✅	10006ms
Error Handling.Retries On 408	✅	14014ms

Feature_Flags Tests

✅ 16/16 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	9501ms
Request Payload.Flags Request Uses V2 Query Param	✅	10007ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	10007ms
Request Payload.Flags Request Omits Authorization Header	✅	10007ms
Request Payload.Token In Flags Body Matches Init	✅	10007ms
Request Payload.Groups Round Trip	✅	10007ms
Request Payload.Groups Default To Empty Object	✅	10007ms
Request Payload.Person Properties Distinct Id Auto Populated When Caller Omits It	✅	10006ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	10007ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	10007ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	10007ms
Request Lifecycle.No Flags Request On Init Alone	✅	5003ms
Request Lifecycle.No Flags Request On Normal Capture	✅	10508ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	9510ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	10003ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	10509ms

[greptile-apps]

Prompt To Fix All With AI

Fix the following 2 code review issues. Work through them one at a time, proposing concise fixes.

---

### Issue 1 of 2
posthog/__init__.py:6
`ID_TYPES` is newly added to the public API snapshot by this PR and appears in public function signatures, but it is imported without the explicit `X as X` re-export form. Under strict Pyright with `reportPrivateImportUsage: error` (which the new smoke-test config enforces), `from posthog import ID_TYPES` would still fail. The PR fixed exactly this pattern for `FlagValue` (`FlagValue as FlagValue`) and `FeatureFlag` (`FeatureFlag as FeatureFlag`), so `ID_TYPES` should receive the same treatment. Note that the smoke-test only checks `from posthog import FlagValue, Posthog`, so this gap is not currently caught by CI.

```suggestion
from posthog.args import ID_TYPES as ID_TYPES, ExceptionArg, OptionalCaptureArgs, OptionalSetArgs
```

### Issue 2 of 2
.github/scripts/check_strict_types.sh:10
`pyright` is installed at its latest released version on every CI run. A new pyright release with tighter checks (or changed defaults) can silently break the job or, conversely, loosen it. Pinning to a known-good version keeps the check stable and makes upgrades a deliberate action. The version can be reviewed and bumped periodically.

```suggestion
"$tmp/.venv/bin/python" -m pip install --quiet . "pyright==1.1.399"
```

_{Reviews (2): Last reviewed commit: "address pr review feedback" | Re-trigger Greptile}