@duyanta123/harnessdeck-sdk

Typed, dependency-free feature detection for HarnessDeck Protocol 3. The SDK does not create a privileged channel: it only describes and validates the narrow window.harnessDeck object that Studio injects into pages served by its active loopback Harness.

import { getHarnessDeck, hasHarnessDeckCapability } from '@duyanta123/harnessdeck-sdk'

const desktop = getHarnessDeck(window)
if (desktop) {
  const offer = await desktop.hello()
  if (hasHarnessDeckCapability(offer, 'workspace')) {
    const chosen = await desktop.pick({ mode: 'directory' })
    if (chosen.path) console.log(await desktop.workspace.validate(chosen.path))
  }
}

Use getHarnessDeck() for plugins that also run in an ordinary browser or headless Harness. Use requireHarnessDeck() only when the entire feature is Desktop-specific. Never retain the object across a Harness navigation/restart; feature-detect again in the new page.

The package version follows HarnessDeck while the wire contract has its own integer protocol. A protocol change is intentionally incompatible and must be handled by a new SDK release. See the repository's bilingual plugin contract for the trust boundary and two-phase package policy.

Harness Host plugins

Host plugins can feature-detect the separate, read-only Host Protocol 1. It exposes the active generation's Studio/Harness versions and a bounded Profile roster. It deliberately cannot start commands, access native handles, install packages, or mutate Profiles.

import { getHarnessDeckHost } from '@duyanta123/harnessdeck-sdk'

export const inject = []

export function apply(ctx) {
  const studio = getHarnessDeckHost(ctx)
  if (!studio) return
  ctx.logger.info(
    `running in ${studio.studio.name} ${studio.studio.version} ` +
      `with ${studio.profiles.list().length} profiles`,
  )
}

Use the normal Harness services for agent, model, session, tool, and workspace behavior. Package or Profile changes must continue through Studio's visible, receipt-backed native flows rather than a retained Host reference.