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/trystan-sa/postkit/postkit-rendernpx skills add Trystan-SA/postkit --skill postkit-rendergit clone --depth 1 https://github.com/Trystan-SA/postkitWhat 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 | $0.00055 | $0.00554 |
| Opus 5 | $0.00028 | $0.00277 |
| Sonnet 5 | $0.00011 | $0.00111 |
| Haiku 4.5 | $0.00006 | $0.00055 |
Grade A, and why
postkit-render 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 yesterday.
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.
What it actually says
/postkit-render — render slides to PNG
You render posts/<slug>/slide-*.html to PNG at the post's native dimensions.
What to do
-
Figure out which post to render. If the user named one, use it. Otherwise list
posts/and ask, or pick the most recently created if context makes it obvious. -
Sanity-check the post folder. It must contain at least one
slide-*.htmland preferably apost.json. Ifpost.jsonis missing, rendering defaults to9:16. -
Shell out to postkit from the project root:
npx postkit render posts/<slug>Output lands in
posts/<slug>/output/slide-N.png. The command prints each file as it renders. -
Report back with the output directory and the list of rendered files. If the user asked for a different format than
post.jsonspecifies, pass--format 1:1(or whichever) to the same command.
If rendering fails
- "No .html slide files found" → the slug is wrong, or slides weren't
created yet. Offer to run
/postkit-new. - Puppeteer/Chrome launch errors on Linux → suggest the user run the repo's
setup.sh(installs Chromium deps) or use theDockerfile. - Fonts look wrong → the renderer waits 1.5s for web fonts; if a
custom Google Font was added recently, re-render. Persistent issues usually
mean the
@importintheme.cssis missing or typo'd.
Multiple posts at once
If the user asks to render a series, call the command once per post:
npx postkit render posts/series-01
npx postkit render posts/series-02
npx postkit render posts/series-03
Batch the results in a single report at the end.
Important
- Don't edit slide HTML here. If rendering reveals a design problem, say so and
suggest
/postkit-reviewor a targeted edit. - Don't commit or push anything. Rendered PNGs are gitignored by default.
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.
- yesterday First seen · 56 lines · 55 tokens per session scan A 0123a7dc4882
postkit-render is a skill published in the GitHub repository Trystan-SA/postkit (4 stars, last pushed 4mo ago), licensed MIT. It adds 55 tokens to every session and 554 once invoked, about $0.0003 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 2026-08-31.
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