dsh-cdp-browser

Zero-spawn browser automation + pixel-level visual verification as a DeepSeek Harness plugin. Drives an already-running Chrome/Edge over CDP using Node built-ins only: global fetch + global WebSocket (Node ≥ 22) + zlib PNG decode. No child_process, no npm dependencies, no per-use approval.

Why zero-spawn

Plugins that spawn an engine and pipe its stdio (e.g. modlens) collide with the harness sandbox's pipe ban (EPERM/EINVAL) on every call. Connecting to a browser the user started themselves is plain network I/O — allowed in confined mode. The one manual step (launching the browser) happens outside the harness, so the model never needs approval again for visual checks.

Setup (once)

1. Install into the profile (done via dsh plugin --profile web add file:<path>).

2. Start your browser with CDP (the provided edge-debug.cmd does this):

   msedge.exe --remote-debugging-port=9222 --remote-allow-origins=* --user-data-dir=<dir> <url>
   

3. Restart the Web GUI. The cdp_* tools appear in the next session.

Tools

Tool	What it does
cdp_status	List tabs/targets of the CDP browser + browser version
cdp_open	Open (or reuse) a tab for a url; returns target id
cdp_eval	Evaluate JS in a page (awaitPromise, returnByValue)
cdp_shot	Navigate + PNG screenshot, saved to an absolute path
cdp_assert	Scripted interaction + deterministic checks (pixel / css / dom / js) with a pass/fail report

cdp_assert check shapes

checks: [
  { type: 'pixel', x: 0.5, y: 0.96, color: '#245edb', tolerance: 16 },  // relative coords 0..1 or absolute px
  { type: 'css', selector: '#taskbar', property: 'background-color', equals: 'rgb(36, 94, 219)' },
  { type: 'css', selector: '.xp-window', property: 'border-radius', matches: '^\\d+px' },
  { type: 'dom', selector: '.xp-desk-icon', text: 'My Computer' },
  { type: 'js', expression: 'window.__XP.selfTest()', equals: { ok: true } },
]
// every check accepts click: '#start-btn' | { selector } | { x, y } and waitMs

Development

node plugins/dsh-cdp-browser/test/e2e.mjs   # needs dev server + CDP Edge, starts nothing

Determinism notes (learned from the XP app's first plugin e2e):

• Reload the page per test run. A long-lived tab accumulates state across scripted sweeps (windows, dialogs, menus) and can wedge openApp; a fresh navigate + skipBoot per suite is deterministic. probe-apps.mjs bisects per-app hangs when an app regresses.
• Synthetic clicks toggle state. el.click() runs the real handlers — clicking a toggle twice flips it twice. One click per assertion.
• Gradient surfaces need stop-aware sampling. Sample where a gradient stop dominates (flat zones or edges), not mid-gradient blends, or use tolerance-aware nearColor against computed-style values.

The package exposes ./cdp (targets, openTarget, withPage, Cdp, decodePng, samplePixel, nearColor, runChecks, savePng) for reuse outside the harness.