Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/posthog/posthog-foss/modifying-taxonomic-filternpx skills add PostHog/posthog-foss --skill modifying-taxonomic-filtergit clone --depth 1 https://github.com/PostHog/posthog-fossWhat 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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5 | $0.00134 | $0.02610 |
| Opus 5 | $0.00067 | $0.01305 |
| Sonnet 5 | $0.00027 | $0.00522 |
| Haiku 4.5 | $0.00013 | $0.00261 |
Grade A, and why
modifying-taxonomic-filter 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 today.
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.
How it starts
The opening of the file, as written. The whole thing — 201 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Modifying the TaxonomicFilter
The TaxonomicFilter is the picker users hit to choose any "thing PostHog
knows about" — events, properties, actions, cohorts, groups. It's the
on-ramp into almost every analytics and replay configuration. Code lives
in frontend/src/lib/components/TaxonomicFilter/.
Two unbreakable rules:
- Changes that demote items users actually pick are regressions, even with all tests passing. Read "Product reality" before deciding any change is safe. Ordering, promotion, or position-0 changes need explicit human sign-off — don't let an agent decide alone.
- There are three live variants behind two feature flags, and the rebuild is a parallel reimplementation of the legacy data + group layer — not a skin over it. A behaviour change usually has to land in both the legacy code and the rebuild, or the two arms of the experiment diverge. Read "Three variants" and "Mirroring changes" before assuming one edit is enough.
Product reality (last refreshed 2026-05-02, 90-day window)
Ratios from production telemetry. Re-run via references/refreshing-product-reality.md when older than ~3 months.
How users pick
- Top three rows carry ~80% of selections (position 0: ~56%, position 1: ~15%, position 2: ~8%). Demoting a popular item out of the top three is a real-user regression.
- ~34% selection rate. Two of every three opens close without a pick. p50 dwell ~7s, p90 ~53s — most opens are quick glances.
- Selection paths: ~65% via search, ~19% browsed-no-search, ~16% from recents, <1% from pinned items.
What users select
| Source group type | Share |
|---|---|
events |
~40% |
event_properties |
~30% |
person_properties |
~14% |
cohorts |
~2% |
email_addresses |
~2% |
actions |
~2% |
pageview_urls |
~1% |
| everything else | <1% |
What users search for (share of top-8 terms)
What ships with it
5 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
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.
- today Changed · +6 lines eb348eb49a96
- yesterday First seen · 195 lines · 134 tokens per session scan A 5ab01ffbf1c4
modifying-taxonomic-filter is a skill published in the GitHub repository PostHog/posthog-foss (713 stars, last pushed today), licensed MIT. It adds 134 tokens to every session and 2,610 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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