Silo

Tab adornments (CenterDock) ​

Ephemeral chrome on editor, terminal, and panel tabs — leading identity icons, trailing Phosphor indicators, a whole-tab highlight, and host-owned Activity. Uses the adorn metaphor (set / clear / flash / bind), not register*. See ADR 0029 and ADR 0030.

There is no ctx.tabs bag and no shared API with future side-panel tab chrome (RFC 0022).

Surfaces ​

ServiceTarget id
ctx.editorsEditor tab id
ctx.terminalsTerminal session id
ctx.panelsPanel's dockview id — DockPanelRecord.panelId (RFC 0046)

All three expose the same verbs via TabAdornmentMethods.

A panel tab shouldn't paint its own chrome ​

ctx.panels targets a panel by its own id, the same way ctx.editors / ctx.terminals target theirs — ordinary third-party adornment, the same shape registerContextMenuItem({ surface: "panel/tab" }) and registerToolbarItem({ surface: "panel" }) already use to act on a panel by that same id (RFC 0046).

What's still a real anti-pattern: a panel adorning its own tab from inside itself, based on its own internal state. That sits outside whatever settings and policy some other extension owns for that chrome, and two extensions doing it to the same tab collide (at most one highlight wins). Prefer declaring what the panel is showing and letting an ordinary binder reach it from the outside — today that's Agent Sessions:

tsx
function ChatPanel({ api }: DockPanelProps) {
  useEffect(() => {
    // "this tab is that Agent Session" — and nothing more
    api.setAgentSession(sessionId);
    return () => api.setAgentSession(null);
  }, [api, sessionId]);
}

From there ctx.agents.bindActivity / bindIcon — which take an Agent Session id, not a tab id — badge this tab exactly as they badge a terminal tab running the same agent. The declaration is withdrawn automatically on unmount. An extension with no such indirection available — e.g. it's adorning an arbitrary tab a user flagged, regardless of kind — binds on ctx.panels directly by panel id instead, same as it already would for an editor or terminal tab.

Leading icon (ReactNode) ​

ts
ctx.editors.setIcon(editorId, { id: "acme.logo", icon: <Logo /> });
ctx.editors.clearIcon(editorId, "acme.logo");

ctx.subscriptions.push(
  ctx.editors.bindIcon({
    id: "acme.logo",
    provide: (editorId) =>
      acmeStore.hasLogo(editorId) ? { icon: <Logo /> } : null,
  }),
);

Tab highlight ​

Paint a soft tinted highlight across the entire tab — icon, title text, and every other adornment — via optional semantic color. Distinct from the leading icon and trailing indicator, which tint only their own glyph. Contributing one (via set, or a bind whose provide returns non-null) is itself the on/off signal — there's no separate boolean. At most one highlight renders per tab; if multiple extensions contribute one for the same target, the first found (set, then bind, in registration order) wins.

ts
ctx.editors.setHighlight(editorId, { id: "acme.title", color: "warn" });
ctx.editors.clearHighlight(editorId, "acme.title");

ctx.subscriptions.push(
  ctx.terminals.bindHighlight({
    id: "acme.title",
    provide: (terminalId) =>
      acmeStore.isFlagged(terminalId) ? { color: "accent" } : null,
  }),
);

Trailing indicator (static Phosphor) ​

You pick a PhosphorIconName (+ optional filled / chip / color). For busy/ready/warn/error chrome use Activity instead.

ts
ctx.terminals.setIndicator(terminalId, {
  id: "acme.flag",
  icon: "Flag",
  chip: true,
  color: "warn",
});
ctx.terminals.clearIndicator(terminalId, "acme.flag");

Activity (host-owned) ​

Pick an Activity — "working" | "ready" | "warn" | "error". The host owns glyph, color, and motion (same dots as workspace status rows; tabs use a slightly larger size). Do not pass icon or color.

ts
ctx.subscriptions.push(
  ctx.terminals.bindActivity({
    id: "acme.busy",
    provide: (terminalId) =>
      acmeStore.isBusy(terminalId)
        ? { activity: "working", tooltip: "Working" }
        : null,
  }),
);

ctx.editors.flashActivity(editorId, {
  activity: "error",
  durationMs: 800,
});

// After mutating store read by binders:
ctx.terminals.invalidateTabAdornments();

Use the SDK ActivityGlyph in your own panels when you want the same glyph (Design System page).

Deprecated shims ​

ctx.terminals.registerTabDecoration / invalidateTabDecorations / subscribeTabDecorations / getTabDecoration remain as thin deprecated wrappers over bindIndicator / invalidateTabAdornments for extensions that shipped against the older terminal-only API.

Types ​

TabIconAdornment · TabHighlightAdornment · TabIndicatorAdornment · TabActivityAdornment · TabIconBinder · TabHighlightBinder · TabIndicatorBinder · TabActivityBinder · TabAdornmentColor · Activity

See also ​