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PostHog
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investigating-error-issue

Investigates a PostHog error tracking issue end-to-end with metrics, breakdowns, and replays.

713|118|Updated Aug 11, 2020
Search Tags:#feature flags#Debugging#Root Cause Analysis#error tracking#session replay#PostHog#clickhouse sql
One-click install
npx skills add https://github.com/PostHog/posthog-foss --skill investigating-error-issue
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: investigating-error-issue
Source: https://github.com/PostHog/posthog-foss/tree/main/products/error_tracking/skills/investigating-error-issue
Command: npx skills add https://github.com/PostHog/posthog-foss --skill investigating-error-issue

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve?

When an error tracking issue appears in PostHog, understanding who it affects, what triggers it, and whether a release or feature flag caused it requires manually assembling data from many queries. This Skill automates that investigation in one pass, producing a hypothesis-grade summary.

Core Features & Use Cases

  • Issue Baseline & Sparkline: Fetches compact issue details (status, assignee, top frame, occurrences, users, sessions) plus a volume sparkline to classify the error's shape (spike, ramp, steady, bursts).
  • Segment Breakdowns via SQL: Runs targeted breakdowns by app version, release, browser, OS, URL, or feature flag variant to isolate the cause, with correct handling of $app_version vs $lib_version vs $exception_releases.
  • Context Reconstruction: Pulls surrounding session events, session-replay console logs, and OTEL server logs around the exception timestamp, and links representative session recordings.
  • Use Case: A user pastes an issue URL like /error_tracking/<id> and asks "what's going on with this error?" — the Skill returns what the error is, who it affects, when it started, the likely cause, and a concrete next step.

Quick Start

Investigate this PostHog error tracking issue and tell me who it affects, when it started, and the likely cause: /error_tracking/<issue_id>.

Frequently Asked Questions about investigating-error-issue

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I investigate a PostHog error tracking issue?▼

Provide the issue ID or paste the issue URL, and the Skill fetches the issue baseline with a volume sparkline, samples exception events, runs breakdowns by version or browser, and synthesizes a summary with likely cause and next step.

How to find which app version introduced an error in PostHog?▼

Run a SQL breakdown grouping $exception events by properties.$app_version and compare each version's first_seen to the issue's overall first_seen. On web and server projects $app_version must be set manually; fall back to $exception_releases or a per-day timeline.

What is the difference between $app_version and $lib_version in PostHog?▼

$app_version is the user's deployed app version, auto-captured on iOS and React Native and set manually elsewhere. $lib_version is the PostHog SDK library version present on every event, so it only answers whether an SDK upgrade caused the error.

Can I check if a feature flag correlates with an error?▼

Yes. Query the per-flag value column properties.$feature/<flag-key> grouped by variant and compare the split against overall flag exposure. Enumerating $active_feature_flags only shows which flags were evaluated, not which correlates with the error.

Why does my error breakdown return all NULL app versions?▼

Web, server, Node, Java, and Python SDKs do not auto-capture $app_version, so the customer must set it via register or a context provider. The Skill flags this in the synthesis and falls back to release metadata or a timestamp timeline.

Why does arrayJoin on $active_feature_flags fail in ClickHouse?▼

The property is a Nullable(String) JSON-encoded column, so arrayJoin fails directly and JSONExtract refuses nullable input at query planning. Wrap it in ifNull(toString(...), '[]') before calling JSONExtract with Array(String).

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