Marketplace scan. https://plugins.omarchy.org/catalog.json is the full catalog (the site's registry.json is a 404; the GitHub registry.json holds only repo URLs). Grep ids, names, descriptions. Confirm the idea is not already there and the id you want is free. Shallow-clone the 3 to 5 nearest plugins and write down what each puts in the bar, what the panel shows, how it polls, and what to steal.
Reference implementations. Read references/quattro-facts.md, then the shipped panels in /usr/share/omarchy/shell/plugins/panels/ (power, network, bluetooth, audio) and plugins/dev-gallery/GalleryPanel.qml, the live catalogue of every shared component.
Data spike. Run the real CLI (--json where it exists) and paste the fields the widget can show. Design only from data that exists.

Phase 2: Prototype in HTML before any QML

The user is visual. Words about a panel mean nothing; a rendered panel means everything. Do this in one pass, one voice, no agent fan-out.

Three directions as option-a/b/c.html plus an index.html that iframes them side by side. Same data in all three. Each page: a mock bar strip showing every widget state, then the panel, a light/dark toggle. Read the user's theme from ~/.config/omarchy/themes/*/colors.toml and default to it. Use a monospace stack ("JetBrainsMono Nerd Font", ui-monospace) and the panel geometry from references/design-language.md.
Screenshot each with headless Chromium and look at the PNG yourself before showing anything.
Serve them (tiny Python HTTP server on a fixed port, webbrowser.open) and open the browser for the user. State your pick and why, briefly.
After a direction is chosen: design-<x>-full.html with every state (healthy, running, failed, stale/warn, not set up, settings) each in its own card with a one-paragraph "why" under it, and the notification mocked inline. Every string is a sentence with a next step. Get a yes on this page.
Only then write the spec.

Phase 3: Start the repo

Two ways to get a template. Use the second when a previous plugin of your own exists; it already has the service/widget split, tests and CI.

Built-in as template. omarchy plugin clone omarchy.clock --edit copies the shipped plugin into ~/.config/omarchy/plugins/omarchy.clock-copy/ (omarchy plugin list --json shows the ids; omarchy.clock is the smallest bar-widget + panel, omarchy.power a good status panel). Move that folder to ~/src/<repo>, rename the id in manifest.json, git init, then install it back the real way (below). The clone stays in the config folder until you omarchy plugin remove it.
Own plugin as template. Copy the skeleton from the last plugin built (for example github.com/steveclarke/omarchy-headroom): manifest.json, BarWidget.qml, Service.qml, CollectorProcess.qml, TintedIcon.qml, Model.js, tests/, tools/, CI workflow and LICENSE. Strip the domain logic, keep the plumbing. Do not copy agent-instruction files (see Install the real way).

Either way: gh repo create <user>/<repo> --public --source=. --push, then omarchy plugin add https://github.com/<user>/<repo> --enable and omarchy-restart-shell. From then on: edit in ~/src, commit, push, omarchy plugin update.

Phase 4: Build

Order matters. Each step ends with a screenshot the user can see.

Manifest + BarWidget.qml with the glyph visible in the bar. First hour. implicitWidth/implicitHeight on the root or the slot is 0x0.
Model.js pure functions with node tests: parsing, state machine, relative time, error-class mapping. Pick the cases from references/testing.md.
Service.qml singleton with a watchdogged Process wrapper (copy Headroom's CollectorProcess.qml), stub binaries under test/stub/ so tests never touch real hardware or real repositories.
Panel.qml healthy state from first-party parts only (PanelHero, PanelSectionHeader, PanelSeparator, CursorSurface, PanelActionButton). Compare the grim capture to the prototype side by side.
Every other state, forced through a debug IPC (omarchy-shell <id> debugState failed), captured, compared.
SettingsView.qml via manifest barWidget.schema, saved with shell.updateEntryInline.
Notifications: notify-send -u critical -A key=Label, one per event, deduplicated by the event's timestamp.
Design audit: three or four read-only agents, one lens each (first-party comparison, cold read plus copy table, flow plus robustness). Apply in one pass, recapture every state, ask again. Done when the user says so. Preview: crop to the panel border exactly (sample edge pixels with magick ... -format "%[pixel:p{x,y}]"), pad on a neutral colour, zoom all four corners.
Security pass before submitting: run the omarchy-plugin-security skill (grep audit, then the marketplace scanner locally on the pushed commit) and fix every hit. Each review round costs a day and reviewers re-read the whole tree after every push.
preview.png (check all four edges at zoom, stand-in names only), then the release sequence in references/release.md (version, green CI, annotated tag, GitHub release), then the marketplace issue per references/marketplace.md.

Verify without touching the user's mouse

omarchy-shell <id> open, omarchy-shell shell toggle <id>, then grim -g on the panel's geometry from omarchy-shell shell debugBarGeometry. Hover via hyprctl eval 'hl.dispatch(hl.dsp.cursor.move({x=..,y=..}))' after saving hyprctl -j cursorpos and restoring it in a finally. Never ask the user to click something to tell you what happened.

When the widget does not load

Walk references/debugging.md top down (files, schema, discovery, enablement, load, lifecycle, IPC, process, interaction) and stop at the first layer that fails. Do not guess at QML while the manifest is still invalid.

Install the real way

Source lives in ~/src/<repo>. omarchy plugin add <git url> --enable clones into ~/.config/omarchy/plugins/<id>/; never edit there. Commit, push, omarchy plugin update, omarchy-restart-shell after any manifest, glyph or IPC change. No symlinks in a plugin folder. Nothing personal in the repo, fixtures, screenshots or history.

No agent-instruction files in the plugin repo. No AGENTS.md, CLAUDE.md, GEMINI.md, .claude/, .cursor/, SKILL.md or similar anywhere in the tree: omarchy plugin add copies the repo into a path coding agents auto-discover, and marketplace review blocks it. Contributor guidance goes in docs/CONTRIBUTING.md. Copy tools/check-agent-files from github.com/steveclarke/omarchy-headroom into bin/check and CI from the first commit.

Screenshots are crops of the panel border, never whole grabs. A grab of the panel's region also captures whatever window sits behind it (a terminal transcript went into a public repo's history this way).

References

references/quattro-facts.md: the non-obvious Quickshell / Quattro facts that cost hours each.
references/design-language.md: geometry, tokens, component vocabulary, state-colour rules, copy rules.
references/testing.md: state cases, live lifecycle checks, evidence record.
references/debugging.md: the failure ladder and the read-only commands.
references/release.md: version, CI, annotated tag, compatibility statement.
references/marketplace.md: submission body, validator quirks, review rounds.

omarchy-plugin

Omarchy plugin

Phase 1: Research (agents, read-only, parallel)