Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/AtlasOmnia/donna-starternpx agentmods add skills/atlasomnia/donna-starter/inspecting-hermes-desktop-domWrote 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/atlasomnia/donna-starter/inspecting-hermes-desktop-dom)<a href="https://agentmods.dev/skills/atlasomnia/donna-starter/inspecting-hermes-desktop-dom"><img src="https://agentmods.dev/badge/skills/atlasomnia/donna-starter/inspecting-hermes-desktop-dom/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/atlasomnia/donna-starter/inspecting-hermes-desktop-dom"><img src="https://agentmods.dev/badge/skills/atlasomnia/donna-starter/inspecting-hermes-desktop-dom.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 | $0.00028 | $0.01601 |
| Opus 5 | $0.00014 | $0.00800 |
| Sonnet 5 | $0.00006 | $0.00320 |
| Haiku 4.5 | $0.00003 | $0.00160 |
Grade A, and why
inspecting-hermes-desktop-dom scanned grade A with 1 finding against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 7d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Makes network callslowCapability
Not a fault in itself. Listed so you know the mod talks to something, and to what.
curl -s --max-time 3 http://127.0.0.1:${HERMES_DESKTOP_CDP_PORT:-9222}/json/version This is a copy
94% identical to inspecting-hermes-desktop-dom — 70 lines differ, which has more behind it and is treated as the original. This page carries a canonical link to it rather than competing with it.
How it starts
The opening of the file, as written. The whole thing — 170 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Inspecting the live Hermes desktop DOM
Overview
When you are developing apps/desktop and the user is running that same app
(hgui / npm run dev), you can read the live rendered DOM of the window
they are looking at — computed styles, geometry, which CSS rule actually won,
console output — instead of inferring it from .tsx and being wrong.
Dev-server runs open a Chrome DevTools Protocol port on 127.0.0.1:9222
automatically. The renderer is a Chromium page, so everything DevTools can read,
a script can read.
This does not replace looking at it. CDP answers factual questions ("what is the computed padding", "did this element render", "which selector matches"). It cannot tell you whether the result looks good. Colour balance, spacing feel, and "is this ugly" still need the user's eyes or a screenshot. Answer facts with CDP; hand aesthetics to the user.
When to Use
- Verifying a UI change actually took effect in the running app
- "Why is this element still X?" — find the winning rule before editing anything
- Locating a stable selector for a component you're about to change
- Checking a design token's computed value on a real node
- Reading renderer console errors the user mentions but can't copy out
Don't use for: perf profiling or heap work (node-inspect-debugger,
debugging-hermes-desktop), or anything where the real question is "does this
look right".
The port
Open on 127.0.0.1:9222 for any dev-server run. Closed in exactly two cases
(apps/desktop/electron/dev-cdp.ts):
- packaged builds — always, and no environment value overrides it;
- no
HERMES_DESKTOP_DEV_SERVER— an unpackagedelectron .againstdist/is how the packaged app gets smoke tested, so it behaves like one.
HERMES_DESKTOP_CDP_PORT moves the port (=9333) or disables it (=off).
Check before doing anything else:
curl -s --max-time 3 http://127.0.0.1:${HERMES_DESKTOP_CDP_PORT:-9222}/json/version
Empty → no port. Do not guess another port silently.
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.
- 7d ago First seen · 170 lines · 28 tokens per session scan A a8df81a0c20e
inspecting-hermes-desktop-dom is a skill published in the GitHub repository AtlasOmnia/donna-starter (111 stars, last pushed 12d ago), licensed MIT. It adds 28 tokens to every session and 1,601 once invoked, about $0.0001 per session on Opus 5. A static security scan graded it A with 1 finding (makes network calls). It is 94% identical to inspecting-hermes-desktop-dom, differing in 70 lines, and is treated as a copy.
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frontend-visual-verification
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inspecting-hermes-desktop-dom
When you are developing apps/desktop and the user is running that same app (hgui / npm run dev), you can read the live rendered DOM of the window they are looking at — computed styles, geometry, which CSS rule actually won, console output — instead of inferring it from .tsx and being wrong.
playground
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frontend-design
Guidance for distinctive, intentional visual design when building new UI or reshaping an existing one. Helps with aesthetic direction, typography, and making choices that don't read as templated defaults.
fixing-motion-performance
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