feat(traces): OTLP span encoding and client-side validity

[turnipdabeets]

💡 Motivation and Context

Adds the OTLP JSON encoder for spans. AnyValue encoding follows the traces spec: int64 as strings, out-of-range ints and non-finite floats as strings, None values and empty keys dropped, unpaired surrogates replaced with U+FFFD, and a bounded walk that terminates on cycles. Also adds the span record builder (W3C flags byte and OTel remoteness bits), the one-resource/one-scope envelope with service.name always present, and the name and timestamp sanitizers.

Why it matters: one bad value otherwise gets the whole batch rejected by ingestion. Not reachable from the client yet.

Stack (PR 2 of 9, based on traces/01-ids-traceparent):

1. feat(traces): W3C trace context ids and traceparent parsing #949 traces/01-ids-traceparent
2. feat(traces): OTLP span encoding and client-side validity #950 traces/02-otlp-encoding ← this PR
3. feat(traces): span handles #951 traces/03-span-handles
4. feat(traces): span batch transport #952 traces/04-transport
5. feat(traces): span pipeline #953 traces/05-pipeline
6. feat(traces): span export queue with retries #954 traces/06-export
7. feat(traces): per-span limits and exception stacktraces #955 traces/07-span-limits
8. feat(traces): before_span_send hook #956 traces/08-before-span-send
9. feat(traces): wire tracing into the client #957 traces/09-client-wiring

💚 How did you test it?

Unit tests in posthog/test/tracing/test_otlp.py and test_sanitize.py cover each encoding rule, the envelope shape and the sanitizers.

📝 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)

Implemented with Claude Code (Claude Opus 5) against the traces spec, one commit per slice so each PR reviews on its own. Rebased onto main and opened as a stacked draft in a later Claude Code session (Claude Fable 5.1).

🤖 Generated with Claude Code

https://claude.ai/code/session_012o7CtHLfcypjmXL7g9ZGRC

[github-actions]

posthog-python Compliance Report

Date: 2026-09-17 03:42:53 UTC
Duration: 256270ms

✅ All Tests Passed!

111/111 tests passed

---

Capture_V1 Tests

✅ 94/94 tests passed

View Details

Test	Status	Duration
Endpoint And Method.Targets V1 Endpoint	✅	515ms
Endpoint And Method.Does Not Use Legacy Endpoints	✅	511ms
Required Headers.Has Authorization Bearer Header	✅	510ms
Required Headers.Has Content Type Json	✅	510ms
Required Headers.Has Posthog Sdk Info Format	✅	510ms
Required Headers.Has Posthog Attempt Header	✅	510ms
Required Headers.Has Posthog Request Id	✅	510ms
Required Headers.Has Posthog Request Timestamp	✅	510ms
Required Headers.Has User Agent	✅	510ms
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	✅	510ms
Event Format.Event Uuid Is Valid	✅	510ms
Event Format.Event Timestamp Is Rfc3339	✅	510ms
Event Format.Distinct Id Is String	✅	510ms
Event Format.Distinct Id At Root Not Properties	✅	510ms
Event Format.Custom Properties Preserved	✅	510ms
Event Format.Set Properties Preserved	✅	510ms
Event Format.Set Once Properties Preserved	✅	509ms
Event Format.Groups Properties Preserved	✅	510ms
Event Format.Sdk Generates Uuid If Not Provided	✅	510ms
Event Format.Event Has Required Root Fields Batch	✅	514ms
Event Format.Event Uuid Is Valid Batch	✅	513ms
Event Format.Event Timestamp Is Rfc3339 Batch	✅	514ms
Event Format.Distinct Id Is String Batch	✅	513ms
Event Format.Distinct Id At Root Not Properties Batch	✅	514ms
Event Format.Custom Properties Preserved Batch	✅	514ms
Event Format.Set Properties Preserved Batch	✅	513ms
Event Format.Set Once Properties Preserved Batch	✅	513ms
Event Format.Groups Properties Preserved Batch	✅	513ms
Event Format.Sdk Generates Uuid If Not Provided Batch	✅	514ms
Batch Behavior.Multiple Events In Single Batch	✅	516ms
Batch Behavior.Batch Envelope Smoke	✅	516ms
Batch Behavior.Flush With No Events Sends Nothing	✅	506ms
Batch Behavior.Flush At Triggers Batch	✅	1011ms
Batch Behavior.Created At Reflects Batch Creation Time	✅	511ms
Deduplication.Generates Unique Uuids	✅	517ms
Deduplication.Different Events Same Content Different Uuids	✅	513ms
Deduplication.Preserves Uuid On Retry	✅	6519ms
Deduplication.Preserves Timestamp On Retry	✅	6516ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	6522ms
Deduplication.No Duplicate Events In Batch	✅	518ms
Header Behavior On Retry.Attempt Header Starts At One	✅	509ms
Header Behavior On Retry.Attempt Header Increments On Retry	✅	13524ms
Header Behavior On Retry.Request Id Preserved On Retry	✅	6518ms
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	✅	510ms
Response Format Validation.Success Response Has Ok For Each Event	✅	514ms
Response Format Validation.Success No Retry After When All Ok	✅	513ms
Response Format Validation.Success Retry After Present When Retry Events	✅	1515ms
Response Format Validation.Success No Retry After When Drop Only	✅	513ms
Response Format Validation.Response Echoes Request Id	✅	510ms
Retry Behavior.Retries On 408	✅	6515ms
Retry Behavior.Retries On 500	✅	6519ms
Retry Behavior.Retries On 503	✅	8518ms
Retry Behavior.Retries On 504	✅	6516ms
Retry Behavior.Retryable Errors Have Retry After	✅	3517ms
Retry Behavior.Respects Retry After On Retryable Error	✅	11521ms
Retry Behavior.Does Not Retry On 400	✅	2514ms
Retry Behavior.Does Not Retry On 401	✅	2513ms
Retry Behavior.Does Not Retry On 402	✅	2514ms
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	✅	2513ms
Retry Behavior.Implements Backoff	✅	22536ms
Retry Behavior.Max Retries Respected	✅	22524ms
Partial Batch Handling.Handles 200 Full Success	✅	2513ms
Partial Batch Handling.Handles 200 With All Ok	✅	3515ms
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	✅	6520ms
Partial Batch Handling.Retries Only Retry Events From Partial	✅	6519ms
Partial Batch Handling.Partial Retry Preserves Uuids	✅	6521ms
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	✅	8520ms
Partial Batch Handling.Unknown Result Treated As Terminal	✅	3513ms
Partial Batch Handling.Mixed Ok Drop Limited No Retry	✅	3518ms
Compression.Sends Gzip Content Encoding	✅	511ms
Compression.No Content Encoding When Disabled	✅	510ms
Compression.Compressed Body Is Decompressible	✅	511ms
Error Handling.Does Not Retry On Unknown 4Xx	✅	2512ms
Event Options.Cookieless Mode Override	✅	511ms
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	✅	513ms
Geoip And Historical Migration.Geoip Disable Injected Into Properties	✅	510ms
Geoip And Historical Migration.Historical Migration Set In Body	✅	510ms
Geoip And Historical Migration.Historical Migration Absent By Default	✅	510ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	12ms
Request Payload.Flags Request Uses V2 Query Param	✅	8ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	9ms
Request Payload.Flags Request Omits Authorization Header	✅	8ms
Request Payload.Token In Flags Body Matches Init	✅	8ms
Request Payload.Groups Round Trip	✅	9ms
Request Payload.Groups Default To Empty Object	✅	8ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	8ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	8ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	9ms
Request Lifecycle.No Flags Request On Init Alone	✅	3ms
Request Lifecycle.No Flags Request On Normal Capture	✅	508ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	15ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	8ms
Retry Behavior.Retries Flags On 502	✅	313ms
Retry Behavior.Retries Flags On 504	✅	312ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	512ms

[greptile-apps]

Prompt To Fix All With AI

### Issue 1
posthog/tracing/_sanitize.py:81
**Float timestamps can overflow**

A finite float such as `1e308` becomes infinite when multiplied by `1e9`, so `round()` or `int()` raises instead of returning `None`. This crashes span creation rather than falling back to the derived time. Validate the scaled value before converting it.

```suggestion
        scaled = value * 1e9
        if not math.isfinite(scaled):
            return None
        ns = int(round(scaled))
```

### Issue 2
posthog/tracing/_otlp.py:192
**Mapping traversal is unbounded**

`list(attributes.keys())` traverses and retains every key before the item and node limits are checked. A large mapping can consume excessive memory, while a custom non-terminating key iterator can hang encoding. Iterate over keys incrementally so encoding stops when its budget is exhausted.

```suggestion
    for key in attributes.keys():
```

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "feat(traces): OTLP span encoding and cli..." | Re-trigger Greptile}

[greptile-apps]

Prompt To Fix All With AI

### Issue 1
posthog/test/tracing/test_otlp.py:373-478
**Large inline expected payload**

This test embeds the complete nested OTLP payload as a large inline expected value. That violates the repository directive to keep extensive test results in external snapshot files. Move the payload to an external snapshot; this requirement must be satisfied before merging.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (2): Last reviewed commit: "fix(traces): reject a float time whose n..." | Re-trigger Greptile}

[dustinbyrne]

Reviewed 284701863a1bca407428638086ea5ff23568df53 via source inspection and existing CI. No issues found in this staged OTLP encoding/validity slice. Approval covers this slice; #949 precedes it in the stack.

[jzhu13]

Reviewed against traces/01-ids-traceparent. Tests pass at the head, ruff and mypy are clean, and the OTLP/JSON shape checks out (casing, hex ids, decimal-string nanos, intValue as string, NaN/Infinity literals, flags bits, enum ints). No blocking issues. Approving with non-blocking notes; the first two are worth doing before this reaches users.

Non-blocking, recommended

1. posthog/tracing/_otlp.py:199 when the 10000-node budget is exhausted, every remaining span attribute is dropped with only a debug log: no [Truncated] marker and nothing feeds droppedAttributesCount. Arrays do get a marker, so the two container types report truncation differently. Reproduced: one large nested first attribute erased posthogDistinctId. Suggest a marker or a returned dropped count so #955's accounting sees it.
2. posthog/tracing/_otlp.py:162 Decimal, UUID, dataclasses, and bytes fall to str(), while posthog.utils.clean makes them numeric or structured for events. span.set_attribute("order.total", Decimal("1.50")) is a string attribute; the same value on an event is numeric. Consider routing leaves through the same primitives. #955's _limits._truncate stringify fallback must change in step.
3. posthog/metrics_capture.py:89 already has an OTLP AnyValue encoder with different int rules and no cycle handling. Two encoders in one package will drift; worth sharing one.
4. posthog/tracing/_otlp.py:335 host_resource_attributes disagrees with get_os_info: events send Mac OS X and the macOS version, spans send macOS and the Darwin kernel release. Reuse _get_platform_os_info, or document why traces follow posthog-node rather than this SDK's events.
5. Nits: the module docstring says any input yields an acceptable payload, but ids and timestamps pass through unvalidated (#956 is what actually guarantees them); to_resource_key_value_list re-encodes the fixed resource dict on every flush.

Reviewed with Claude Code (Claude Fable 5.1). Behaviors above were reproduced by probe against this branch head.

[turnipdabeets]

Thanks. Done in e4b74a7: item 4 (constant renamed) and the docstring nit.

• 2 and 3: declining for this stack. Spec and Node stringify unknown leaves, and merging with the metrics encoder is its own refactor.
• 1 and the resource re-encode cache: still open.

[turnipdabeets]

Follow-up, a6b6c95:

• 1: when the node budget runs out, the entries it cuts are counted into droppedAttributesCount on the span and on each event. Join keys are written first, so they are encoded before any user value can spend the budget.
• 5: the resource is encoded once per exporter and handed to the payload builder.
  Ready for another look.