Hermes Desktop Plugins Skill

Write plugins for the Hermes desktop app: statusbar items, layout panes, command-palette commands, keybinds, routes, and themes. A plugin is a single plain-JavaScript ESM file the app loads at runtime — no build step, no repo changes. A plugin can also talk to its own Python backend namespace (ctx.rest/ctx.socket → /api/plugins/<id>); the general Python plugin system (~/.hermes/plugins/) is otherwise documented separately.

Full human reference (every export, area payloads, backend, security): website/docs/developer-guide/desktop-plugin-sdk.md.

When to Use

• The user asks for a new desktop UI element (a pane, a statusbar widget, a dashboard, a command) without modifying the app itself.
• You want to surface data you compute (via gateway RPC) inside the app.

Prerequisites

• The Hermes desktop app (it loads plugins; the CLI/gateway alone does not).
• Write access to $HERMES_HOME/desktop-plugins/ (usually ~/.hermes/desktop-plugins/).

How to Run

1. Create $HERMES_HOME/desktop-plugins/<name>/plugin.js from templates/plugin.js (relative to this skill directory) — that's ~/.hermes/... by default, or ~/.hermes/profiles/<profile>/... under a named profile. Keep <name> equal to the plugin id.
2. The desktop app watches that directory: the plugin loads within a few seconds of the file landing, and every later save hot-reloads it in place. No reload step. (Fallback if it doesn't appear: ⌘K → Reload desktop plugins.)
3. If loading fails the app shows a toast naming the error — fix the file and save again.

Quick Reference

The ONLY import surface is @hermes/plugin-sdk (plus react / react/jsx-runtime, which resolve to the app's own React — write UI with jsx() calls, not JSX syntax; the file is not compiled).

• host.state.* — readonly reactive atoms: activeSessionId, cwd, gateway, model, profile, viewport. Read with .get() in handlers, useValue(atom) in components.
• host.request(method, params) — gateway JSON-RPC (sessions, config, skills, cron — everything the app uses).
• host.onEvent(type, fn) — live gateway events ('*' for all). Returns a disposer.
• host.notify({ kind, message }), host.navigate(path), host.logs(...), host.status(), haptic('tap').
• ctx.register({ id, area, order?, render?, data? }) — contribute UI. Key areas: 'statusBar.right'/'statusBar.left' (chips), 'panes' (layout zones — set title and data: { placement, dock?, width?, height? }; the pane auto-joins a matching zone), PALETTE_AREA (⌘K commands), KEYBINDS_AREA (rebindable actions).
• Pane placement: placement: 'left'|'right'|'bottom'|'main' is the semantic role — the pane stacks (tabs) with existing panes of that role. To land on a specific EDGE instead, add dock: { pane, pos } — the same gesture as dragging onto a pane's drop chip. pane is any pane id (workspace is the main thread; also sessions, terminal, files, review, logs), pos is 'top'|'bottom'|'left'|'right'|'center'. E.g. "below the conversation" = dock: { pane: 'workspace', pos: 'bottom' } — declare a height (e.g. '200px') so it doesn't take half the zone.
• Full PAGES: register area: ROUTES_AREA with data: { path: '/my-page' } and a render — the page mounts in the workspace (main) pane like any built-in view. Make it reachable with a sidebar nav row: ctx.register({ id: 'nav', area: SIDEBAR_NAV_AREA, data: { path: '/my-page', label: 'My Page', codicon: 'project' } }) (renders below Artifacts, lights up at the route) — and/or a PALETTE_AREA command calling host.navigate('/my-page').
• ctx.storage.get/set/remove — persistence namespaced to your plugin.
• ctx.i18n.register({ en, ja, ... }) — ship your OWN locale bundles, scoped to your plugin (never edit core en.ts). Values are literal strings or interpolator functions; nested trees are addressed by dot-path. Read them reactively in components with usePluginI18n(id) returning t('key', ...args) (re-renders on a locale switch), or via ctx.i18n.t in handlers/stores. Resolution follows the app's active locale, then your en, then the raw key.
• Data: useQuery/useMutation/useQueryClient/queryClient (the app's ONE React Query client — cache, dedupe, refetchInterval, invalidate like core; never hand-roll a poll loop), plus atom/computed for plugin-local state.
• Backend: if the plugin ships a Python plugin_api.py (under ~/.hermes/plugins/<id>/dashboard/, manifest "api": "plugin_api.py"), reach it with ctx.rest('/path', { method?, body?, timeoutMs? }) and its live twin ctx.socket('/events', onMessage) — both scoped to /api/plugins/<id> by construction (traversal rejected). ctx.socket is a no-op on OAuth remotes, so always keep a polling fallback. The Python backend is imported only when the plugin is in plugins.enabled in config.yaml (separate from the in-app enable toggle). For gateway-wide data use host.request / host.onEvent instead.
• Contribute (mount-scoped): render jsx(Contribute, { area, id, children }) inside a component so page-owned chrome (e.g. a titlebar control in TITLEBAR_AREAS.center) leaves when the page unmounts — ctx.register is for permanent contributions.
• defaultEnabled: false on the default export ships an opt-in plugin: it inventories in Settings → Plugins, off until the user flips it on.
• Users manage plugins in Settings → Plugins (enable/disable live, reveal folder). A disabled plugin stays disabled across restarts — don't fight it; the user turned you off.
• UI: the app's design language, importable directly — Button, Input, Textarea, Select*, Switch, Checkbox, SegmentedControl, Tabs*, Dialog*, ConfirmDialog, DropdownMenu*, ContextMenu*, Popover*, Tip/Tooltip*, Badge, Kbd/KbdGroup, SearchField, ScrollArea, Separator, Skeleton, GlyphSpinner, EmptyState, ErrorState, CopyButton, StatusDot, LogView, Codicon, DecodeText, plus cn and icons.*. Prefer these over hand-rolled elements so the plugin looks native; style with theme vars, never hardcoded colors.

Procedure

1. Pick a short kebab-case id; the folder name must match.
2. Start from templates/plugin.js; keep the default export shape ({ id, name, register(ctx) }).
3. For a pane, register area: 'panes' with a placement hint and a render returning your component — the app places it into a sensible zone automatically; the user can drag it anywhere afterwards.
4. Fetch data with host.request and/or subscribe with host.onEvent; never poll faster than a few seconds.
5. Write the file with your file tools, then ask the user to run Reload desktop plugins from ⌘K.

Pitfalls

• NEVER hardcode colors or backgrounds (#000, black, rgb(...)). Panes already sit on the app's editor background — leave the background alone and use theme variables for everything else: var(--ui-text-secondary), var(--ui-text-quaternary), var(--ui-stroke-secondary), var(--ui-accent). For canvas drawing, resolve them once with getComputedStyle(canvas).getPropertyValue('--ui-accent').
• Reference only what you imported — a component you forgot to import (e.g. StatusDot) is a ReferenceError at render. Double-check every identifier in your jsx() calls appears in the import line.
• Canvas panes MUST track their container with a ResizeObserver and re-size the canvas (width/height attributes, not just CSS) — panes resize constantly (sash drags, layout switches); a mount-time-only size leaves blank space or blurry scaling.
• JSX syntax will not parse — the file loads uncompiled. Use jsx('div', { children: ... }) from react/jsx-runtime.
• Do not import anything except @hermes/plugin-sdk, react, and react/jsx-runtime; other specifiers fail to resolve.
• Handlers must read state imperatively ($atom.get()), never from render closures — rapid events will otherwise see stale values.
• Keep components small; subscribe (useValue) only in the leaf that renders the value.

Verification

• The plugin's UI appears after Reload desktop plugins.
• No error toast ("Plugin failed to load") appears; if it does, the message names the failure — fix and reload.
• For panes: the new zone is visible and draggable like any core pane.

Public support files

• templates/plugin.js