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 ericrisco/rsc-harness --skill htmxgit clone --depth 1 https://github.com/ericrisco/rsc-harnessWrote 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/ericrisco/rsc-harness/htmx)<a href="https://agentmods.dev/skills/ericrisco/rsc-harness/htmx"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/htmx/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/ericrisco/rsc-harness/htmx"><img src="https://agentmods.dev/badge/skills/ericrisco/rsc-harness/htmx.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00098 | $0.03598 |
| Opus 5.5 | $0.00039 | $0.01439 |
| Sonnet 5.5 | $0.00020 | $0.00720 |
| Haiku 4.5 | $0.00010 | $0.00360 |
Grade C, and why
htmx scanned grade C 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 1mo 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.
Hidden instructionshighPrompt injection
Directives inside HTML comments, invisible characters or bidirectional overrides are read by the model and not by the person reviewing the file.
<!-- Response to POST /cart/add: swap the row in normally... --> How it starts
The opening of the file, as written. The whole thing — 262 lines — stays where its author put it; the contents beside it link to each section on GitHub.
htmx: hypermedia-driven UIs
The server owns all application state and renders HTML. The client is dumb: it swaps server-rendered fragments into the DOM. There is no JSON API for the UI, no client store, no virtual DOM, no client router. If you find yourself returning JSON and rendering it with JavaScript, you have stopped doing htmx and started building an SPA — use a different tool.
The unit of work is one request, described by four attributes on one element:
- a verb —
hx-get/hx-post/hx-put/hx-patch/hx-delete(the URL) hx-target— which DOM node receives the response (CSS selector orthis)hx-swap— how the response is placed (defaultinnerHTML)hx-trigger— on what event (default: natural —clickfor buttons,submitfor forms,changefor inputs)
Versions (verify before pinning). htmx 2.0.x is current stable (2.0.10 latest 2.x line); v1 (1.9.x) is legacy, kept only for IE/old-browser support. htmx v4 is in beta targeting Summer 2026 and changes some defaults (default swap behavior, config) — do not write to v4 yet. Pin to 2.x:
<script src="https://unpkg.com/[email protected]" crossorigin="anonymous"></script>
When to use
- Adding interactivity to a server-rendered app without a JS framework.
- Wiring a verb +
hx-target+hx-swap+hx-triggerto update a page region. - Returning partials/fragments — full page on direct navigation, fragment on htmx request
(branch on the
HX-Requestheader). - Out-of-band updates (
hx-swap-oob) when one response must refresh several regions. - Trigger-driven UX: active search, infinite scroll, inline edit, click-to-load, polling,
revealed,intersect, debounced input. - Server-driven control flow via response headers (
HX-Trigger,HX-Redirect, …).
When NOT to use — route elsewhere
- A client-state-heavy SPA (offline, optimistic UI everywhere, complex client routing) →
react,vue-nuxt,svelte,solid-js,angular, or ../nextjs/SKILL.md. htmx is the anti-SPA; do not fight it. - How to structure the server framework itself (routers, ORM, controllers) → ../fastapi/SKILL.md,
django,rails,laravel. This skill owns the htmx contract (which fragment, which header, which swap), not framework internals. Cross-link, do not duplicate. - Generic XSS/CSP/auth theory → ../secure-coding/SKILL.md. Keep only the htmx-specific notes here.
- Focus management and ARIA live regions after a swap →
accessibility. - Browser E2E of swaps →
testing-web/e2e-testing. - Purely-client state (Alpine, vanilla sprinkles) → out of scope; htmx is for server round-trips.
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.
- 1mo ago First seen · 262 lines · 98 tokens per session scan C e49d1cc50b8b
htmx is a skill published in the GitHub repository ericrisco/rsc-harness (340 stars, last pushed today), licensed MIT. It adds 98 tokens to every session and 3,598 once invoked, about $0.0004 per session on Opus 5.5. A static security scan graded it C with 1 finding (hidden instructions). No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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