posthog-foss: Skill for Claude Code

.agents/skills/querying-tophog/SKILL.md

querying-tophog is a skill for Claude Code, Codex from PostHog/posthog-foss. It costs 120 tokens per session (2,080 once invoked), scanned A, original, MIT.

A query guide for finding the people, teams, sessions, or data partitions causing heavy processing in an ingestion pipeline. It uses Tophog, a ClickHouse data store that records aggregated workload details for 30 days.

In plain words
What is it for?
Use it during ingestion lag, Kafka partition, expensive processing, or merge-storm investigations. Queries are run through the company’s internal Metabase service.
Why use it?
Fleet-wide monitoring can show that processing is slow but not which actor is responsible. This helps narrow incident investigations to specific high-volume or expensive sources.

Skill for Claude CodeCodex

Written for no agent in particular: nothing here depends on one. Also seen: installed under .agents/ (shared by several agents).

This is PostHog/posthog-foss's own configuration. It tells Claude Code and Codex how to work on posthog-foss itself, so it is not a mod to install elsewhere. Copy it as a starting point and replace the rules that are about this project. Everything posthog-foss configures →

Reuse

Borrowing it

Nothing to install: this file belongs to PostHog/posthog-foss. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.

Copy the file
curl -O https://raw.githubusercontent.com/PostHog/posthog-foss/master/.agents/skills/querying-tophog/SKILL.md
Clone the repo
git clone --depth 1 https://github.com/PostHog/posthog-foss

Made for: Claude Code, Codex.

Wrote this? Show the measurements

A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.

agentmods badge for querying-tophog

README.md
[![agentmods](https://agentmods.dev/badge/skills/posthog/posthog-foss/querying-tophog/github.svg)](https://agentmods.dev/skills/posthog/posthog-foss/querying-tophog)
Your own site
<a href="https://agentmods.dev/skills/posthog/posthog-foss/querying-tophog"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/querying-tophog/github.svg" alt="Measured on agentmods" height="20"></a>

Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.

agentmods 80×15 button for querying-tophog

Your own site · 80×15
<a href="https://agentmods.dev/skills/posthog/posthog-foss/querying-tophog"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/querying-tophog.svg" alt="Reviewed on agentmods" width="80" height="20"></a>
Per session 120 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,080 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. A grade says what 26 rules found in the file — not that it is safe. Third-party audits
  • NVIDIA SkillSpector warn 7 Sept 2026
SkillSpector: 5 findings, up to medium

These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →

  • medium Prompt Injection · line 65
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 62
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 70
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 72
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
  • medium Prompt Injection · line 128
    Large whitespace padding was detected (a block of blank lines or a long run of spaces). This can push injected instructions below or to the right of the visible area so a human reviewer never sees them while the agent still reads them. Manual review of the hidden content is recommended.
    Fix: Remove the large whitespace padding (blank-line blocks or long space runs) and review any content hidden below or to the right of it. Keep skill files compact and reviewable so no instructions can be
How audits are shown
Origin original No closer match found in the catalogue.
Token cost

What it costs to keep this loaded

Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.

ModelPer sessionOnce invoked
Fable 5.1 $0.00120 $0.02080
Opus 5 $0.00060 $0.01040
Sonnet 5 $0.00024 $0.00416
Haiku 4.5 $0.00012 $0.00208

Measured 2d ago against content hash 80b5db640876, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-10, from the pricing page.

Security

Grade A, and why

querying-tophog scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 2d ago.

A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.

Nothing flagged

None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.

.agents/skills/querying-tophog/SKILL.md · 216 lines

How it starts

The opening of the file, as written. The whole thing — 216 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Querying tophog

tophog is the ingestion pipeline's heavy-hitter tracker: workers accumulate per-key aggregates (counts, timers) in memory and periodically flush them to the tophog ClickHouse table via Kafka (clickhouse_tophog topic). It answers "which actor is responsible" questions that fleet-level Prometheus metrics cannot — per-metric label cardinality is unbounded (distinct_id, session_id), so this data lives only in ClickHouse. Retention is 30 days.

The staff-only Django admin has a dashboard over it, but for agent-driven triage query it directly through the internal Metabase.

Access — internal Metabase, never Grafana

The production ClickHouse clusters hold customer data, so there is deliberately no ClickHouse datasource for agents in Grafana. The sanctioned path is the internal Metabase using the engineer's own SSO session — per-person identity, attributable in Metabase's query history, no standing credential. General mechanics live in the querying-production-databases-via-metabase skill; the short version:

  1. The user must run login themselves (the agent shell cannot access the Keychain): hogli metabase:login --region eu (or us). macOS will prompt about "Chrome Safe Storage" — that's browser_cookie3 decrypting the browser's cookie store to capture the SSO session; one-time Allow is the right choice.

  2. Discover the database id — it is not stable across Metabase rebuilds:

    hogli metabase:databases --region eu
    

    Pick "PostHog ClickHouse PROD Data Tier" (the data tier, not the query tier — tophog lives with the events data).

  3. Run queries; the cookie is read internally and never enters the transcript:

    hogli metabase:query --region eu --database-id <id> <<'SQL'
    SELECT ...
    SQL
    

Schema

Table tophog (Distributed over sharded_tophog), ordered by (pipeline, lane, metric, timestamp, key), partitioned by day:

Column Type Notes
timestamp DateTime64(6) Flush-window time; always bound it (daily partitions)
metric LowCardinality(String) See inventory below
type LowCardinality(String) Aggregation semantics: sum (default), max, avg
key Map(String, String) The actor: access as key['team_id'], key['distinct_id'], key['partition'], key['session_id']
value Float64 The aggregated value for this flush window
count UInt64 Observations in the window
pipeline LowCardinality(String) e.g. analytics
lane LowCardinality(String) main, overflow, historical, async, turbo
labels Map(String, String) Extra non-key labels

Read the full file on GitHub · 216 lines

Changes

What this file has done since we first saw it

Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.

  1. 2d ago Changed 80b5db640876
  2. 11d ago First seen · 216 lines · 120 tokens per session scan A 52123974a6a5

Subscribe to this mod's changes

querying-tophog is a skill published in the GitHub repository PostHog/posthog-foss (715 stars, last pushed today), licensed MIT. It adds 120 tokens to every session and 2,080 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.

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