Lens Inspect

Inspect and interact with a live web application through Stave's built-in browser panel.

What is Lens?

Lens is a per-workspace embedded browser backed by Electron's WebContentsView. AI agents can use it hidden through MCP, while users can reveal the same session in a workspace tab when interaction or visual confirmation is needed.

Session Behavior

• MCP tools reuse the visible or most recently used Lens tab for the workspace.
• If no session exists, any operational tool creates a hidden default session automatically. Calling stave_lens_open_session first is optional.
• Stave applies the user's Agent Activity setting when visual inspection or page interaction starts: show beside the task, add a background tab, or let the agent decide.
• Automatic presentation is limited to screenshot, inspect/measure, click/type, live style edit, and saved-account fill. Navigation, redirects, snapshots, DOM/log reads, and generic evaluation do not reveal a hidden session by themselves.
• If a click navigates, the click is the presentation boundary. Continue in the same session; do not explicitly present it again just because the URL changed.
• Use stave_lens_present_session only when the user must immediately interact with the page, sign in, or explicitly asks to see the result.
• Revealing a hidden session preserves its URL, history, cookies, and page state.
• Users can also open Lens with the Globe icon or the Command Palette action Show Lens.

MCP Tools

All tools require a workspaceId parameter.

Element Picker

The crosshair button in the address bar activates the element picker.

1. Hover over elements to highlight them with a blue overlay.
2. Click an element to capture its info.
3. Press Escape to cancel.

Captured data is inserted into the active task's prompt draft:

• CSS selector, tag, ID, classes
• Bounding box and computed styles
• Truncated outerHTML and textContent
• Source search hints (AI-friendly grep patterns)
• React _debugSource file:line (when enabled in Settings)

Source Code Mapping

Configure in Settings > Lens > Source Code Mapping.

Heuristic Search (default: on)

The AI uses distinctive class names, text content, IDs, and component-style class patterns from the picked element to search your codebase with grep or file-search tools. Works with any framework.

React _debugSource (default: off)

When your application runs in React dev mode with @babel/plugin-transform-react-jsx-source (enabled by default in Vite React plugin, CRA, and Next.js dev), the picker extracts the exact fileName:lineNumber from React fiber internals. This gives 100% accurate source location when available, with automatic fallback to heuristic search.

Figma Design Comparison Workflow

Combine Lens with a Figma MCP server for design-to-code verification:

1. figma-mcp: read design spec (colors, spacing, layout)
2. stave_lens_navigate("http://localhost:3000/page")
3. stave_lens_screenshot()
4. Compare rendered output to Figma spec
5. Modify code to fix discrepancies
6. Repeat from step 2

Tips

• Console/network logs are ring-buffered at 200 entries each. Check them early if debugging.
• Full-page screenshots use CDP Page.getLayoutMetrics to capture beyond the viewport.
• Accessibility snapshots (stave_lens_snapshot) give a compact page structure summary — useful when full HTML is too verbose.
• Element picker works best on non-minified, dev-build pages where class names are meaningful.
• Session persists across panel switches. Switching to Explorer and back to Lens keeps your browsing state.
• The default project profile shares cookies and storage across a project's workspaces. The workspace profile setting provides isolation when needed.

Avoid

• Don't use file:// or chrome:// protocols — they are blocked for security.
• Don't rely on _debugSource in production builds — it's only available in dev mode.
• Don't screenshot without navigating first — about:blank yields an empty image.