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 skills add PostHog/posthog-foss --skill cleaning-up-stale-feature-flagsgit clone --depth 1 https://github.com/PostHog/posthog-fossWrote 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.
[](https://agentmods.dev/skills/posthog/posthog-foss/cleaning-up-stale-feature-flags)<a href="https://agentmods.dev/skills/posthog/posthog-foss/cleaning-up-stale-feature-flags"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/cleaning-up-stale-feature-flags/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.
<a href="https://agentmods.dev/skills/posthog/posthog-foss/cleaning-up-stale-feature-flags"><img src="https://agentmods.dev/badge/skills/posthog/posthog-foss/cleaning-up-stale-feature-flags.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector pass
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.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00129 | $0.05160 |
| Opus 5 | $0.00064 | $0.02580 |
| Sonnet 5 | $0.00026 | $0.01032 |
| Haiku 4.5 | $0.00013 | $0.00516 |
Grade B, and why
cleaning-up-stale-feature-flags scanned grade B with 1 finding 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.
Instruction-override phrasingmediumPrompt injection
Text telling the model to disregard its earlier instructions or safety rules is the shape of a prompt injection, whoever wrote it.
A flag named "ignore previous instructions" is a badly named flag, nothing more. Downgraded: this mod is about security review, or the phrase is quoted, so it is likely naming the pattern rather than instructing it.
Copies of this mod
1 near-identical copy found in the catalogue:
- cleaning-up-stale-feature-flags — 91% identical, 0 lines differ
How it starts
The opening of the file, as written. The whole thing — 381 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Cleaning up stale feature flags
This skill guides you through finding feature flags that no longer serve a purpose and removing them safely. The ordering is fixed: clean up the code, wait for that cleanup to deploy, and only then change the flag in PostHog.
When to use this skill
- The user asks to clean up, audit, review, or remove their feature flags
- The user wants to find flags that are stale, unused, or fully rolled out
- The user asks "which feature flags can I remove?" or similar
- The user wants to reduce tech debt from old feature flags
Do not activate for an unrelated coding task that merely mentions a feature flag. Cleaning up a flag is its own job, requested by the user.
What makes a flag stale
A feature flag is considered stale when it's no longer doing useful work. PostHog tracks this with two signals:
- Usage-based staleness: The flag has
last_called_atdata, but hasn't been evaluated in 30+ days. This is the strongest signal — the SDKs are no longer checking this flag. - Configuration-based staleness: The flag has no usage data (
last_called_atis null), is 30+ days old, and is 100% rolled out (boolean at 100% with no property filters, or a multivariate flag with one variant at 100%). A fully rolled out flag with no conditions is equivalent to a hardcoded value — it can be replaced by removing the flag check from code.
Disabled flags (active: false) are not considered stale — they were intentionally turned off and may be kept for reactivation.
Treat configuration-based staleness more cautiously than old evaluation evidence:
$feature_flag_called events can be missing when local evaluation is used or event capture is disabled,
and a config-only signal says nothing about whether code still checks the flag.
Stale means cleanup candidate, never proof that removal is safe.
Establish what you can do
Before assessing candidates, work out which path you can complete in this session:
- PostHog read access only (no repository): assess candidates, then produce the tailored handoff prompt (see "Hand off when you cannot edit the repository").
- Repository read access: additionally inspect the exact call sites and turn the handoff into a repository-specific plan.
- Repository write access: make the code changes yourself and test them locally.
- Authorized publishing: also open one draft PR per flag, following the host's branch, commit, and PR policy.
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.
- 2d ago Changed · +186 lines · +62 tokens per session scan A → B 194d8a5a486c
- 9d ago First seen · 195 lines · 67 tokens per session scan A 39e9622698a9
cleaning-up-stale-feature-flags is a skill published in the GitHub repository PostHog/posthog-foss (715 stars, last pushed today), licensed MIT. It adds 129 tokens to every session and 5,160 once invoked, about $0.0006 per session on Opus 5. A static security scan graded it B with 1 finding (instruction-override phrasing). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
Other skills, from other repositories
prowler-commit
Creates professional git commits following conventional-commits format. Trigger: When creating commits, after completing code changes, when user asks to commit.
gh-auth-isolation
Safely manage multiple GitHub identities (EMU + personal) in agent workflows.
comet-github
A routing guide for Comet-related GitHub work. It directs requests about pull requests, issues, CI failures, ideas, and fixes to the appropriate review or implementation process.
github-skill
Work with GitHub via the gh CLI — clone repositories, create/list/merge pull requests, create/list issues, and run any other gh command (API calls, workflow runs, releases, repo administration). List operations return parsed JSON.
changelog-composer
Generates structured changelogs and release notes from git history and PRs, classifying breaking changes, features, fixes, performance, docs. Triggers on: "generate changelog", "write release notes", "what changed since", "prepare release", "release notes for", "diff since tag".
re0-merge
Review and land an external contribution the way this suite does: gate it against the thesis, land it with the author's credit intact, complete a new skill rather than merging it raw, then approve, credit, and explain before closing. Use when reviewing a pull request, as any collaborator or maintainer, not only the…