[Harsh23Kashyap]

Fixes #1078.

When an event property holds a non-finite float (inf, -inf, nan), the SDK serializes batches with json.dumps(..., cls=DatetimeSerializer) under the default allow_nan=True. That emits the bare tokens Infinity and NaN, which are not valid JSON, so strict-parsing ingestion and intermediaries (Go's encoding/json, most load balancers) reject the whole batch and the events are lost. posthog-js does not hit this because JSON.stringify converts non-finite numbers to null.

Change: DatetimeSerializer.encode now routes the payload through a small recursive helper that replaces non-finite floats with None before encoding, mirroring JSON.stringify. Every ingestion serialization site (sync post, capture v1, async v0 and flags bodies) goes through this encoder, so the one change covers all of them. Finite values, datetimes and other types are unchanged.

Tests:

• New test sends a batch with inf, -inf and nan properties through post() and asserts the request body parses under a strict JSON parser (parse_constant raises) and the values arrive as null.
• Control test pins that finite values round-trip unchanged.
• The new test fails twice before the fix (strict parse rejects the body) and passes twice after it. Full posthog/test/test_request.py (68 passed) and test_capture_v1.py pass; ruff format --check and ruff check show no new findings on the touched files.

[turnipdabeets]

Thanks @Harsh23Kashyap! Heads up that #1052 handles the same problem on the v8 branch differently so we probably need alignment.

Cc @eli-r-ph @dustinbyrne

[Harsh23Kashyap]

Thanks @turnipdabeets. Happy to align with #1052. Which behavior would you like on main: drop only the invalid event, or something else? I can adapt this PR to match whichever you pick.

[turnipdabeets]

Thanks @turnipdabeets. Happy to align with #1052. Which behavior would you like on main: drop only the invalid event, or something else? I can adapt this PR to match whichever you pick.

I’ll let @eli-r-ph or @dustinbyrne answer which they prefer

[marandaneto]

Automated advisory code review.

[marandaneto]

Commits must have verified signatures.

pls sign your commits @Harsh23Kashyap

[marandaneto]

The code looks good; no qualifying findings. Verdict: correct.

[marandaneto]

All three current commits now have verified GitHub signatures, and the encoder override is included in the public API snapshot. The requested behavior for this fix is to preserve events by serializing numeric NaN and infinities as JSON null, rather than rejecting the event or batch. This PR already implements that behavior.