Darbot Browser MCP

The independent validation pass over the HTML audit report, why Playwright could not perform it, and the driver limitation that shaped how it was done.

Why a second driver

The audit deliverable is coral-ui-audit.html — a single self-contained report with four tabs, a hash router, an embedded gallery, and inlined JSON datasets. It is meant to be opened from disk, with no web server.

Playwright blocks file:// URLs. Validating the report through Playwright would therefore have required standing up an HTTP server, which validates a different artifact than the one shipped: it proves the report works when served, not that it works as a local file.

@darbotlabs/darbot-browser-mcp@1.3.0 permits file://, so it was driven directly through the MCP SDK over stdio to validate the real artifact in its real delivery mode.

The pass

Run 2026-06-07, Sunday PM PDT. Result: PASS on load, console, network, and render.

Check	Tool	Result
Loads via file://	browser_navigate	Page loaded directly from disk, no server
Page title	browser_analyze_context	Coral UI Audit — Raybot, correct
Console errors, Overview tab	browser_console_messages	0 errors
Console errors, Elements tab	browser_console_messages	0 errors
Console errors, API Map tab	browser_console_messages	0 errors
Console errors, Gallery tab	browser_console_messages	0 errors
Prior APIMAP['$meta'] bug	console	Gone. No APIMAP, undefined, or syntax errors
Gallery images	browser_network_requests	38 of 38 screenshots/*.png returned HTTP 200
Tab deep-linking	browser_navigate to #overview, #elements, #api, #gallery	All four tabs activate through the hash router
Per-tab render capture	browser_pdf_save	4 of 4 saved

The only console message anywhere was a benign Edge INFO notice about lazily loaded images being replaced with placeholders. Not an error.

Four PDFs were produced and are the authoritative darbot-native capture: darbot-overview.pdf, darbot-elements.pdf, darbot-api.pdf, and darbot-gallery.pdf — the last around 5 MB because it embeds the screenshots.

The driver limitation

In this environment, three tools fail under darbot-browser-mcp@1.3.0:

browser_take_screenshot
browser_snapshot
browser_click

All three raise:

page._snapshotForAI is not a function

This is a Playwright-version mismatch in the bundled driver. It is a property of the driver build, not of the report and not of the MCP protocol.

The practical consequence is that this driver can observe but cannot interact. Navigation, console reading, network reading, context analysis, and PDF export all work. Anything that needs the accessibility snapshot — including every click — does not.

Validation was therefore completed entirely through the observational tools. Deep-linking was exercised by navigating to each hash rather than clicking each tab, which happens to be a stronger test of the hash router than clicking would have been.

The 01-overview.png through 04-gallery.png PNGs in the validation folder were captured separately, over a local HTTP server with the Chromium engine, and are supplementary flat previews only. The PDFs are the darbot-native proof.

What this validation does and does not establish

Establishes. The shipped HTML file loads from disk in a Chromium-family browser with no console errors, resolves all 38 gallery image references, and routes correctly across all four tabs.

Does not establish. That the report is correct. This is a rendering and integrity check, not a content audit. The correctness of the underlying numbers rests on the ground-truth methodology and the confidence model, not on this pass.

Does not establish. That the report works in non-Chromium engines. Only Edge was exercised.

Note on image counts

This pass verified 38 gallery images on 2026-06-07. screenshot-map.md covers 41 curated captures, and gallery.json now holds 95. Three different numbers, all defensible in their own context - 95 is the total capture count across all phases as of 2026-06-19, 41 is the curated canonical set from Phases 1 through 6, and 38 is what the report's gallery tab actually referenced at validation time, twelve days before the showcase captures existed. The scoping is recorded in the errata.