posthog-foss: Skill for Claude Code

.agents/skills/adding-ingestion-warnings/SKILL.md

adding-ingestion-warnings is a skill for Claude Code, Codex from PostHog/posthog-foss. It costs 150 tokens per session (3,406 once invoked), scanned A, original, MIT.

An engineering guide for adding warnings to PostHog's event ingestion pipeline, the system that receives and processes customer events. It explains warning registration, categories, severity, serialization, and the Kafka and ClickHouse destinations.

In plain words
What is it for?
Use it when adding an ingestion warning, category, severity, or warning-producing behavior in the Node.js ingestion code.
Why use it?
It keeps warning types consistent and prevents unregistered or mismatched warning details from reaching stored ingestion data.

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/adding-ingestion-warnings/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 adding-ingestion-warnings

README.md
[![agentmods](https://agentmods.dev/badge/skills/posthog/posthog-foss/adding-ingestion-warnings.svg)](https://agentmods.dev/skills/posthog/posthog-foss/adding-ingestion-warnings)
Your own site
<a href="https://agentmods.dev/skills/posthog/posthog-foss/adding-ingestion-warnings"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/adding-ingestion-warnings.svg" alt="Measured on agentmods" height="20"></a>
Per session 150 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 3,406 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: 3 findings, up to high

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 →

  • high Anti-Refusal · line 98
    Skill instructs the agent to omit warnings, disclaimers, or ethical commentary. Stripping safety caveats hides risk from the user and is a common jailbreak preamble.
    Fix: Remove instructions that suppress warnings, disclaimers, or ethical commentary. Let the agent surface safety-relevant caveats to the user.
  • high Anti-Refusal · line 100
    Skill attempts to nullify the agent's safety policies or restrictions ('you have no restrictions', 'ignore your guidelines', 'do anything now'). This is a direct jailbreak that disables guardrails.
    Fix: Remove jailbreak framing that nullifies safety policies or restrictions. Skill content must not instruct the agent to ignore its guidelines or operate without guardrails.
  • medium Agent Snooping · line 117
    Skill enumerates or reads other installed skills. Access to other skills' SKILL.md files or the skills directory reveals prompt instructions, capabilities, and secrets that should be invisible to peer skills.
    Fix: Remove all code or instructions that list or read other skills' files or directories. Skills should operate independently; cross-skill access is a privilege escalation.
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 $0.00150 $0.03406
Opus 5 $0.00075 $0.01703
Sonnet 5 $0.00030 $0.00681
Haiku 4.5 $0.00015 $0.00341

Measured 8d ago against content hash 190af6a79605, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-08, from the pricing page.

Security

Grade A, and why

adding-ingestion-warnings 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 8d 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/adding-ingestion-warnings/SKILL.md · 120 lines

How it starts

The opening of the file, as written. The whole thing — 120 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Adding ingestion warnings

Ingestion warnings tell customers their events were ingested with problems (or dropped). They are produced to the clickhouse_ingestion_warnings Kafka topic and land in two ClickHouse tables: v1 (ingestion_warnings) and v2 (ingestion_warnings_v2, which materializes structured columns from the details JSON).

The registry is the source of truth

Every warning type must be registered in INGESTION_WARNING_TYPES in nodejs/src/ingestion/common/ingestion-warning-types.ts (a dependency-free leaf, re-exported from ingestion-warnings.ts, so codegen and its test can import it cheaply). The registry fixes the type's category and severity; they are resolved at serialization time, so callsites cannot drift or forget them. An unregistered type is a compile error (IngestionWarningType is the registry's key union).

To add a new warning:

  1. Register the type in INGESTION_WARNING_TYPES, inside the matching group comment block. Pick:
    • category — one of size, merge, event, quota, transformation, replay. Extend IngestionWarningCategory only when the warning genuinely doesn't fit an existing group; new categories flow into API filters and agent-facing docs, so keep the vocabulary small.
    • severity — follow the convention: error = the event or message was dropped, warning = ingested but modified or partially rejected, info = informational or an intentional, team-configured drop.
  2. Emit it (see below), passing only per-occurrence fields: details, pipelineStep, optional key / alwaysSend.
  3. Update downstream surfaces (see checklist).

Emitting

Two paths, both end at serializeIngestionWarning:

  • Pipeline steps (preferred): return warnings on the result — ok(value, sideEffects, warnings) or drop(reason, [], warnings). They accumulate in context.warnings and are sent by handleIngestionWarnings(), which requires a teamAware() block. See the framework doc test 09-ingestion-warnings.
  • Direct emit: emitIngestionWarning(outputs, teamId, warning) (outputs-based, preferred) or captureIngestionWarning(kafkaProducer, teamId, warning) (legacy) for code outside the pipeline result flow.

Read the full file on GitHub · 120 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. 8d ago First seen · 120 lines · 150 tokens per session scan A 190af6a79605

Subscribe to this mod's changes

adding-ingestion-warnings is a skill published in the GitHub repository PostHog/posthog-foss (714 stars, last pushed today), licensed MIT. It adds 150 tokens to every session and 3,406 once invoked, about $0.0007 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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