Argus Qa

Argus MCP server

Argus Panoptes — the all-seeing giant of Greek mythology with a hundred eyes who never slept.

Automated browser testing pipeline that catches bugs, compares environments, and sends rich reports to Slack (or generates a self-contained HTML dashboard when Slack is not configured) — powered by Chrome DevTools MCP and Claude Code.

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MCP Quick Start

Add both servers to your .mcp.json:

{
  "mcpServers": {
    "chrome-devtools": {
      "command": "npx",
      "args": ["-y", "chrome-devtools-mcp@latest"]
    },
    "argus": {
      "command": "npx",
      "args": ["-y", "argusqa-os"]
    }
  }
}

Or register via the Claude Code CLI:

claude mcp add chrome-devtools -- npx -y chrome-devtools-mcp@latest
claude mcp add argus -- npx -y argusqa-os

Set your target URL and start Chrome with remote debugging:

# .env
TARGET_DEV_URL=http://localhost:3000

# Start Chrome (required — Argus drives this instance via CDP)
# macOS:   open -a "Google Chrome" --args --remote-debugging-port=9222 --headless=new
# Windows: "C:\Program Files\Google\Chrome\Application\chrome.exe" --remote-debugging-port=9222 --headless=new
# Linux:   google-chrome --remote-debugging-port=9222 --headless=new --no-sandbox

Then ask Claude (or any MCP client):

Run argus_audit on http://localhost:3000

Six tools are exposed:

Tool	What it does
argus_audit	Fast QA pass — JS errors, network failures, accessibility, SEO, security, CSS, content
argus_audit_full	Deep QA pass — adds Lighthouse scoring, responsive layout checks across 4 viewports, memory leak detection, hover-state bug detection, and accessibility tree snapshot
argus_compare	Diff dev vs staging side-by-side — screenshots, findings delta, environment regressions
argus_last_report	Return the last saved JSON report without re-running a scan
argus_watch_snapshot	Snapshot the currently open Chrome tab without navigating — raw console + network capture
argus_get_context	Capture everything broken on the open tab, formatted as a diagnostic context for Claude to diagnose and suggest fixes

Requires: Node.js ≥ 20.19, Chrome (desktop or headless), and the chrome-devtools-mcp server registered alongside Argus (shown above).

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The landing/ directory contains the product landing page (React + Vite + Tailwind + Framer Motion) with Supabase-backed waitlist and enterprise contact forms. Live at argus-qa.com (deployed via Cloudflare Pages; background video served from Cloudflare R2). See landing/README.md for setup.

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What Argus Catches

Argus runs 24 analysis engines per run and detects 114 distinct issue types across JavaScript runtime, network, CSS, performance, accessibility, SEO, security, content quality, responsive layout, memory, runtime anti-patterns, hover-state interactions, accessibility tree snapshots, keyboard focus, and Chrome DevTools issues panel — plus flakiness detection, historical baselines, user flow assertions, and environment comparison as cross-cutting layers. Every finding is classified by severity (critical / warning / info) and routed to the right Slack channel — or rendered as a local report.html when Slack is not configured.

JavaScript Runtime

Severity	Bug / Issue	Detection Method
🔴 Critical	Uncaught exceptions — TypeError, ReferenceError, etc.	window.onerror listener injected before page load
🔴 Critical	Unhandled Promise rejections	unhandledrejection event listener injected into the page
🟡 Warning	console.error calls (on non-critical routes)	Chrome DevTools list_console_messages
🔴 Critical	console.error calls (on critical routes)	Chrome DevTools list_console_messages
🔵 Info	console.warn deprecation notices and warnings	Chrome DevTools list_console_messages

Network & API

Severity	Bug / Issue	Detection Method
🔴 Critical	HTTP 5xx server errors on any request	list_network_requests → status ≥ 500
🔴 Critical	401 / 403 auth failures — user is being kicked out	list_network_requests → status 401 or 403
🔴 Critical	API endpoint called 5+ times in one page load — likely an infinite loop	Network frequency grouping by normalized URL + method
🟡 Warning	HTTP 4xx client errors (404, 422, 429, etc.)	list_network_requests → status 400–499 (non-auth)
🟡 Warning	API endpoint called 3–4 times — likely a double-fetch bug	Frequency grouping → 3 ≤ count ≤ 4 (check useEffect deps)
🔵 Info	API endpoint called twice — may be intentional prefetch	Frequency grouping → count = 2
🔵 Info	API call summary per page load (total calls, unique endpoints, duplicates)	Aggregated network analysis
🟡 Warning	Redirect chain longer than 2 hops — extra round-trips inflate load time	Navigation Timing redirectCount read after page settle
🟡 Warning	Broken internal link — <a href> target returns HTTP 404	<a> elements harvested via evaluate_script, each verified against list_network_requests

Page Health

Severity	Bug / Issue	Detection Method
🔴 Critical	Blank or near-empty page — less than 50 characters of body text	document.body.innerText length check after navigation
🟡 Warning	Expected element never appeared — page may have crashed mid-load	waitFor selector timeout after 10 seconds

CSS & Styling

Severity	Bug / Issue	Detection Method
🟡 Warning	!important cascade conflict — forced override fighting another rule	CSS rule walk: property declared with !important on same element
🟡 Warning	Component style leak — BEM selector found in the wrong stylesheet	.block__element selector in a file whose name doesn't match block
🟡 Warning	React inline style overriding a stylesheet declaration on the same element	style="" attribute vs. matching CSS rule, __reactFiber presence confirmed
🔵 Info	CSS property declared by multiple rules on the same element (cascade override)	Computed style walk across all matched rules per key element
🔵 Info	Unused CSS rules — selectors matching no element on the page (> 10 flagged)	querySelectorAll(selector).length === 0 for every rule
🔵 Info	CSS Modules detected — hashed class names found on DOM elements	Pattern _ComponentName_class_hash matched on live DOM
🔵 Info	SCSS source map found — compiled CSS traced back to .scss origin file	sourceMappingURL comment in <style> tags

Performance

Severity	Bug / Issue	Detection Method
🟡 Warning	LCP > 2500ms — largest element took too long to paint	Chrome performance trace → performance_analyze_insight
🟡 Warning	CLS > 0.1 — layout shifted significantly after initial render	Chrome performance trace
🟡 Warning	FID / TBT > 100ms — main thread was blocked during interaction	Chrome performance trace
🟡 Warning	TTFB > 800ms — server took too long to send the first byte	Chrome performance trace

Accessibility

Severity	Bug / Issue	Detection Method
🔴 Critical	Lighthouse accessibility score below 50 / 100	Lighthouse audit via lighthouse_audit
🟡 Warning	Lighthouse accessibility score 50–89 / 100	Lighthouse audit
🟡 Warning	Missing alt text on images	Individual Lighthouse audit check
🟡 Warning	Insufficient color contrast ratio	Individual Lighthouse audit check
🟡 Warning	Missing ARIA labels on interactive elements	Individual Lighthouse audit check
🟡 Warning	Keyboard navigation broken or unreachable elements	Individual Lighthouse audit check

SEO

Severity	Bug / Issue	Detection Method
🟡 Warning	Missing <meta name="description">	DOM inspection via evaluate_script
🟡 Warning	Missing Open Graph tags (og:title, og:description, og:image)	DOM inspection via evaluate_script
🟡 Warning	og:image URL is relative — Open Graph requires an absolute URL	DOM inspection + URL prefix check (http:// / https://)
🟡 Warning	Multiple <h1> tags on one page	DOM inspection — querySelectorAll('h1').length > 1
🟡 Warning	Zero <h1> tags — page has no primary heading	DOM inspection — querySelectorAll('h1').length === 0
🟡 Warning	Generic page title (less than 10 characters, or default placeholder)	DOM inspection + length check
🟡 Warning	Missing <link rel="canonical">	DOM inspection via evaluate_script
🟡 Warning	Missing <meta name="viewport">	DOM inspection via evaluate_script

Security

Severity	Bug / Issue	Detection Method
🔴 Critical	Auth token found in localStorage or sessionStorage	evaluate_script walks storage keys for token patterns
🔴 Critical	Sensitive token in the page URL (query param or hash)	URL pattern match against current window.location.href
🔴 Critical	eval() call detected in page scripts	evaluate_script AST-style text scan of inline <script> tags
🔴 Critical	CSP violation — inline script or external resource blocked by Content-Security-Policy	Chrome DevTools Issues panel (list_console_messages({ types: ['issue'] }))
🟡 Warning	Sensitive data (password, token, secret) logged to the console	list_console_messages + keyword match
🟡 Warning	Missing Content-Security-Policy response header	fetch(location.href) inside the page → response headers check
🟡 Warning	Missing X-Frame-Options response header	Same headers fetch
🟡 Warning	Cross-origin <iframe> without sandbox attribute — enables form submission, parent navigation, cookie access	evaluate_script checks iframe[src] elements for missing sandbox attribute
🟡 Warning	Page served over plain HTTP with no HTTPS upgrade redirect	URL protocol check (http:// + non-localhost)
🔵 Info	Cookie present without HttpOnly flag (limited detection — JS-visible cookies only)	document.cookie inspection
🔵 Info	Deprecated browser API usage (e.g. document.domain, DOMSubtreeModified)	Chrome DevTools Issues panel

Content Quality

Severity	Bug / Issue	Detection Method
🟡 Warning	null or undefined rendered as visible text	DOM text scan for literal "null" / "undefined" strings
🟡 Warning	Lorem ipsum / placeholder copy still in production	DOM text scan for "lorem ipsum" and common placeholder strings
🟡 Warning	Broken image (404 or failed to load)	evaluate_script checks img.naturalWidth === 0 on all images
🔵 Info	Empty data list — <ul>, <ol>, or <select> with no children	DOM structure check

Responsive / Mobile

Severity	Bug / Issue	Detection Method
🔴 Critical	Horizontal overflow at mobile / tablet viewport (≤ 768px)	emulate at 375px and 768px → document.documentElement.scrollWidth > clientWidth
🟡 Warning	Touch target smaller than 44×44 px at mobile or tablet viewport	CSS computed size check on interactive elements at 375px and 768px
🔵 Info	Responsive screenshot grid — snapshots at 375 / 768 / 1024 / 1440px	emulate at 4 breakpoints, screenshots dispatched to Slack

Network Performance

Severity	Bug / Issue	Detection Method
🔴 Critical	API response time > 3000ms	PerformanceObserver entries for fetch / XHR calls
🟡 Warning	API response time > 1000ms	Same observer, lower threshold
🔴 Critical	API response payload > 2 MB	list_network_requests → response body size
🟡 Warning	API response payload > 500 KB	Same, lower threshold
🟡 Warning	Cross-origin (third-party) script TTFB > 2000ms — blocking render or late interactivity	HAR timing.wait field from list_network_requests HAR data; cross-origin requests only

Network Request Origin Tagging

All network findings carry an origin field ('first-party' / 'third-party') so operators can triage critical first-party failures separately from third-party noise.

Lighthouse Audits

Severity	Bug / Issue	Detection Method
🔴 Critical	Lighthouse accessibility score < 50 / 100	lighthouse_audit (accessibility category)
🟡 Warning	Lighthouse accessibility score 50–89 / 100	lighthouse_audit
🟡 Warning	Lighthouse performance score < 90 / 100	lighthouse_audit (performance category)
🟡 Warning	Lighthouse SEO score < 90 / 100	lighthouse_audit (seo category)
🟡 Warning	Lighthouse best-practices score < 90 / 100	lighthouse_audit (best-practices category)
🟡 Warning	Individual failing Lighthouse audit items	Surfaced per-audit from the full Lighthouse report

Memory Leaks

Severity	Bug / Issue	Detection Method
🔴 Critical	> 100 detached DOM nodes in V8 heap — severe leak	take_memory_snapshot → parse flat nodes array for "Detached Xxx" names
🟡 Warning	> 10 detached DOM nodes in V8 heap — probable leak	Same snapshot parse, lower threshold
🟡 Warning	Heap grew > 2 MB after navigate-away + navigate-back — probable per-load leak	performance.memory.usedJSHeapSize delta across round-trip (soft — GC-dependent)

Runtime Anti-Patterns

Severity	Bug / Issue	Detection Method
🟡 Warning	Synchronous XMLHttpRequest — blocks the main thread until the server responds	XMLHttpRequest.open patched via addScriptToEvaluateOnNewDocument; async === false calls recorded
🟡 Warning	document.write / document.writeln called — can erase the page or block parsing	document.write and document.writeln patched before page load; calls recorded with method + content
🟡 Warning	Long task > 50ms on the main thread — blocks user interaction	PerformanceObserver with entryTypes: ['longtask'] injected before page load
🔴 Critical	CORS policy violation — cross-origin fetch blocked by the browser	list_console_messages + pattern match for "has been blocked by CORS policy"
🟡 Warning	Service worker registration failure — SW script returns 4xx or is invalid	navigator.serviceWorker.register patched before page load; .catch() records failing script URL
🔵 Info	Same-origin static asset (.js, .css, .png, .woff2, etc.) served without Cache-Control or ETag — browsers cannot cache it efficiently	evaluate_script reads performance.getEntriesByType('resource'), HEAD-fetches each unique same-origin asset, checks response headers

Historical Baselines & Trends

Severity	Bug / Issue	Detection Method
🔴 Critical	New critical finding not present in the saved baseline — regression introduced since last run	applyBaseline compares finding keys (type::message[:100]::status) against reports/baselines/<branch>.json (D7.2 per-branch)
🟡 Warning	New warning finding not present in the baseline	Same key comparison, warning severity
🔵 Info	Pre-existing finding still present — no change since last run	Suppressed from real-time alerts; included in info digest only
🔵 Info	Run trend summary — new vs resolved counts, saved per run	Appended to reports/baselines/<branch>-trends.json; surfaced as a trend line in Slack digest

Hover-State Bugs

Severity	Bug / Issue	Detection Method
🟡 Warning / 🔴 Critical	[aria-haspopup] element whose controlled popup does not become visible after hover — aria-expanded stays false and popup remains display:none / visibility:hidden / opacity:0	hover dispatches mousemove; evaluate_script checks aria-expanded + getComputedStyle on the controlled element; critical on routes marked critical: true
🟡 Warning	[data-tooltip] element whose [role="tooltip"] is not visible in the DOM after hover — not found or opacity ≤ 0.05	Same hover + evaluate_script checks tooltip opacity, display, visibility, and offsetHeight

Accessibility Snapshot Analysis

Severity	Bug / Issue	Detection Method
🟡 Warning	Interactive element (<button>, <a>, [role="button"], [role="link"]) with no accessible name — no text content, aria-label, aria-labelledby, title, or alt	take_snapshot captures DOM/AX state; evaluate_script queries each visible interactive element for accessible name sources
🟡 Warning	Form control (<input>, <select>, <textarea>) with no associated label — no <label for="...">, aria-label, or aria-labelledby (placeholder is intentionally excluded — not a valid accessible name per WCAG 2.1 §3.3.2)	evaluate_script checks label[for], ancestor <label>, aria-label, and aria-labelledby for each visible control
🟡 Warning	Landmark role appearing more than once without distinct aria-label / aria-labelledby — screen readers cannot differentiate them	evaluate_script counts [role=X] instances and checks for unique label values across: main, banner, contentinfo, navigation, search, complementary, form, region
🟡 Warning	Heading level skip — h1→h3 or h4→h6 jumps more than one level, breaking WCAG 1.3.1 document outline	DOM walk of h1–h6 elements; detects gaps > 1 between consecutive heading levels
🟡 Warning	aria-expanded button/control has no aria-controls attribute or references a non-existent element	evaluate_script checks [aria-expanded] elements for missing or broken aria-controls pointer

Keyboard Accessibility

Severity	Bug / Issue	Detection Method
🟡 Warning	Button or focusable element has outline:0 with no box-shadow fallback — no visible focus ring	press_key({ key: 'Tab' }) walk + evaluate_script reads document.activeElement computed style for outline/box-shadow

Flakiness Detection

Severity	Bug / Issue	Detection Method
original	Confirmed finding — present in both crawl runs	mergeRunResults finds the key in both run1 and run2 (type::message[:100]::status scheme); original severity kept
🔵 Info	Flaky finding — appeared in only one of two crawl runs	Present in run1 or run2 but not both; downgraded to severity: 'info', labelled :zap: _flaky_ in Slack digest

User Flow Assertions

Severity	Bug / Issue	Detection Method
🔴 Critical	Flow step failed — navigate/fill/click/waitFor threw mid-flow (page state unknown)	flow-runner.js wraps every step; any throw emits flow_step_failed and halts the flow
🔴 Critical	element_visible assert — expected selector absent within timeout	Polled via evaluate_script + document.querySelector (MCP wait_for doesn't reliably throw on timeout)
🟡 Warning	no_console_errors assert — console errors recorded during this flow (baseline-sliced, not session-wide)	Baseline snapshot of list_console_messages at flow start; only messages after that offset count
🟡 Warning	no_network_errors assert — 4xx/5xx request during this flow (baseline-sliced)	Baseline snapshot of list_network_requests at flow start; status ≥ 400 after offset
🟡 Warning	url_contains assert — URL does not include expected substring after flow completes	evaluate_script reads window.location.href
🟡 Warning	element_not_visible assert — selector unexpectedly present in DOM	evaluate_script → !document.querySelector(...)
🔴 Critical	no_js_errors assert — uncaught exceptions captured in window.__argusErrors during flow	Script parses the injected error buffer

Environment Regressions (dev vs staging)

Severity	Bug / Issue	Detection Method
🔴 Critical	API status regressed — request that returned 2xx in dev now returns 5xx in staging	Network diff between both environments
🟡 Warning	Visual change > 0.5% pixels different between dev and staging screenshots	pixelmatch pixel-level comparison + diff overlay image
🟡 Warning	New console error in staging that doesn't exist in dev	Console message diff
🟡 Warning	New network request in staging — unexpected endpoint appeared	Network request URL diff
🟡 Warning	Request present in dev is missing in staging — endpoint removed or broken	Network request URL diff
🟡 Warning	API status changed between environments (any non-5xx change)	Network status diff
🔵 Info	DOM structural change — element count differs between dev and staging	HTML tag count comparison across snapshots

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What It Does

Argus watches your running application and automatically surfaces issues that test suites miss: visual regressions, API loops, CSS drift, console noise, and accessibility failures — all with screenshots delivered directly to Slack.

Feature	Description
Error Detection	Crawls your app's routes; captures JS exceptions, console errors, failed API calls, redirect chains, and broken internal links
Environment Comparison	Diffs dev vs staging: screenshots, DOM structure, network requests, console errors
CSS Analysis	Detects cascade overrides, component style leaks, unused rules, React inline style conflicts
API Frequency Analysis	Flags endpoints called more than once per page load (double-fetch, missing useEffect deps, infinite loops)
Network Performance	slow_api > 1s/3s and large_payload > 500KB/2MB per API call
SEO Checks	Missing meta description, OG tags, canonical, viewport, h1 — DOM-inspected on every route
Security Checks	localStorage tokens, token-in-URL, eval(), sensitive console output, missing CSP/X-Frame-Options
Content Quality	null/undefined rendered text, lorem ipsum, broken images, empty data lists
Responsive Analysis	Overflow + touch target checks at 375/768px; screenshot grid at 4 breakpoints dispatched to Slack
Memory Leak Detection	V8 heap snapshot → detached DOM node count; heap growth across navigate-away + navigate-back
Runtime Anti-Patterns	Synchronous XHR, document.write, long tasks > 50ms, CORS violations, service worker registration failures, and missing cache headers on static assets — detected via script injection and post-load HEAD checks
Hover-State Bug Detection	Fires hover on every [aria-haspopup] and [data-tooltip] element; detects broken dropdowns and invisible tooltips that CSS :hover was supposed to reveal
Accessibility Snapshot Analysis	Calls take_snapshot then evaluate_script; flags interactive elements missing accessible names, unlabelled form controls, duplicate landmark regions, heading level skips, and aria-expanded buttons with missing/broken aria-controls
Keyboard Focus Analysis	Tab-walks every focusable element (up to 20 steps); detects focus_visible_missing (button/link with outline:0 and no box-shadow fallback — keyboard users cannot see where focus is)
Chrome DevTools Issues Panel	Queries list_console_messages({ types: ['issue'] }) for the Issues panel namespace, which is entirely separate from console.error; catches CSP violations and deprecated API usage (verified) — additional Chrome-surfaced types (CORS blocks, mixed content, cookie misconfiguration, low-contrast) are classified when present
Mobile CPU Throttling	Applies 4× CPU throttle (emulate_cpu({ throttlingRate: 4 })) during ≤768px responsive breakpoints — finds layout reflow and animation jank that only manifests under realistic mobile CPU pressure
Origin-Tagged Network Findings	All network error and timing findings carry origin: 'first-party' | 'third-party' so operators can triage critical first-party failures without digging through third-party CDN noise
Historical Baselines	Saves finding keys after each run; subsequent runs only alert on new issues; trend summary in Slack digest
Flakiness Detection	Crawls each route twice per run; findings in both runs are confirmed (original severity); findings in only one run are marked flaky (severity: info, :zap: _flaky_ label)
User Flow Assertions	Named multi-step flows (navigate/fill/click/press_key/drag/upload_file/waitFor/sleep/handle_dialog/assert) with baseline-sliced no_console_errors, no_network_errors, element_visible, url_contains, no_js_errors asserts — runs end-to-end user journeys without writing Playwright specs · Use typing: true on a fill step to dispatch real keyboard events via mcp.type_text (triggers input-event validation) · Use drag step to fire dragstart→dragover→drop sequences · Use upload_file step to deliver a local file to a file input via CDP ({ action: 'upload_file', selector: 'input[type=file]', filePath: '/path/to/file' })
API Contract Validation	Define apiContracts[] in targets.js with inline schema or schemaFile; validates captured response bodies against JSON Schema (type, required, properties, items) — emits api_contract_violation warnings when shapes diverge from spec
Severity Policy Overrides	Define severityOverrides in targets.js ({ finding_type: 'info' | 'warning' | 'critical' | 'suppress' }); applied before Slack routing — remap or silence specific detections without touching analyzer code
Auth Token Refresh	refreshSession() is called before each route; re-runs the login flow when the saved session has less than sessionRefreshWindowMs (default 5 min) remaining — prevents long crawls from failing mid-run when the auth cookie expires
Slack-optional mode	When SLACK_BOT_TOKEN is not configured, Argus skips Slack entirely and auto-generates a local report.html (all findings + inline screenshots) and opens it in the default browser — zero setup required to start using Argus
Codebase Cross-Reference	Points ARGUS_SOURCE_DIR at your app source to detect: missing env vars (process.env.X used in code but absent from .env), feature flag leakage (conditional env var that is falsy/unset), console error stack traces resolved to file:line, and internal links that return 404 — all without opening a browser
GitHub PR Integration	Posts a structured Markdown findings table as a PR comment (updates in-place — one comment per PR, no spam); sets an argus-qa commit status check (failure when new criticals exist, success otherwise) — blocks merge via branch protection when regressions are introduced. Requires GITHUB_TOKEN + GITHUB_REPOSITORY env vars
Auto Route Discovery	Augments manual routes[] with paths from three sources: fetches /sitemap.xml (follows one sitemap-index level, 10s timeout), scans Next.js pages/ (Next 12) and app/ (Next 13+) directories stripping route groups (auth), and greps JS/TS source for React Router <Route path> declarations. Dynamic [param] segments are skipped — no concrete URL to crawl. Manual route config (critical, waitFor) always takes precedence.
argus init Setup Wizard	npm run init (or npx argus init) guides first-time setup: collects target URLs, detects the app framework (Next.js / React Router / unknown) from the source directory's package.json, runs C3 route discovery against the dev URL, prompts for optional Slack tokens and GitHub credentials, then writes a populated .env and a pre-filled src/config/targets.js — zero manual config editing required.
Watch Mode	npm run watch attaches to whatever Chrome tab is open and polls list_console_messages + list_network_requests every 1 s (configurable via ARGUS_WATCH_INTERVAL_MS). Reports new console errors, network failures (4xx/5xx), CORS blocks, and auth failures in real time — without navigating. Starts a live web dashboard at http://localhost:3002 (configurable via ARGUS_WATCH_UI_PORT). On Ctrl+C, generates a final reports/report.html. No route config needed.
Full Lighthouse Suite	All 4 Lighthouse categories (performance, SEO, best-practices, accessibility) with per-audit items
Performance Budgets	Enforces LCP < 2500ms, CLS < 0.1, FID < 100ms, TTFB < 800ms per route
Slack Notifications	Rich Block Kit reports with inline screenshots routed to #bugs-critical, #bugs-warnings, #bugs-digest
Slash Command	/argus-retest <url> triggers an on-demand test from any Slack channel
CI Integration	GitHub Actions workflow runs daily at 6 AM UTC and on every push to main
MCP Server (AI-callable Argus)	Register Argus as an MCP server via .mcp.json; Claude (or any MCP client) can call argus_audit, argus_audit_full, argus_compare, argus_last_report, argus_watch_snapshot, and argus_get_context directly from a conversation — no CLI, no terminal required. Published to npm as argusqa-os — add via { "command": "npx", "args": ["-y", "argusqa-os"] } in .mcp.json

Works with React + SCSS, CSS Modules, CSS-in-JS (styled-components / emotion), and plain HTML/CSS apps.

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How It Works

Three components run against the same Chrome instance:

Claude Code (Terminal / VS Code)
  ├── MCP Protocol → Chrome DevTools MCP Server → Chrome
  └── Writes → Orchestration Layer → Slack Bot API

• Chrome DevTools MCP Server — programmatic access to Chrome: network traffic, console, screenshots, DOM, performance traces
• Claude Code — orchestration hub: reads codebase, drives the MCP tools, classifies findings, posts to Slack
• Slack Bot (BugBot) — receives reports, exposes /argus-retest slash command, handles Acknowledge / Retest button actions

In interactive mode (running from Claude Code), MCP tools are called natively. In CI mode (GitHub Actions), src/utils/mcp-client.js spawns chrome-devtools-mcp as a child process and communicates via JSON-RPC over stdio.

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Prerequisites

Requirement	Version	Notes
Node.js	v20.19+	Required by Chrome DevTools MCP
Chrome	Stable (current)	Must be installed
Claude Code	Latest	npm install -g @anthropic-ai/claude-code
Slack workspace	—	Optional — only needed if you want Slack reports. Without it, Argus generates a local report.html instead

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One-Time Setup

Option A — MCP Server (Claude Code / any MCP client)

No local install required. npx auto-downloads argusqa-os on first use.

1. Register both MCP servers

Add to .mcp.json in your project root:

{
  "mcpServers": {
    "chrome-devtools": {
      "command": "npx",
      "args": ["-y", "chrome-devtools-mcp@latest"]
    },
    "argus": {
      "command": "npx",
      "args": ["-y", "argusqa-os"]
    }
  }
}

Or via Claude Code CLI:

claude mcp add chrome-devtools -- npx -y chrome-devtools-mcp@latest
claude mcp add argus -- npx -y argusqa-os

2. Environment variables

Create a .env file in your project root:

TARGET_DEV_URL=http://localhost:3000
TARGET_STAGING_URL=https://staging.yourapp.com   # optional — enables argus_compare

3. Start Chrome with remote debugging

# macOS
open -a "Google Chrome" --args --remote-debugging-port=9222 --headless=new

# Windows
"C:\Program Files\Google\Chrome\Application\chrome.exe" --remote-debugging-port=9222 --headless=new --no-sandbox --disable-gpu

# Linux
google-chrome --remote-debugging-port=9222 --headless=new --no-sandbox

4. Slack notifications (optional)

Skip to use local report.html mode — Argus generates a self-contained HTML report when Slack is not configured.

1. api.slack.com/apps → Create New App → name it BugBot
2. OAuth & Permissions → Bot Token Scopes: chat:write, files:write, files:read
3. Install to workspace → copy Bot User OAuth Token (xoxb-...) to .env as SLACK_BOT_TOKEN
4. Create #bugs-critical, #bugs-warnings, #bugs-digest and /invite @BugBot in each

SLACK_BOT_TOKEN=xoxb-...
SLACK_CHANNEL_CRITICAL=C0000000000
SLACK_CHANNEL_WARNINGS=C0000000001
SLACK_CHANNEL_DIGEST=C0000000002

---

Option B — npm Package (dev dependency / CI/CD)

1. Install

npm install --save-dev argusqa-os

2. Environment variables

Run the interactive wizard to auto-generate .env and src/config/targets.js:

npx argus

The wizard detects your framework (Next.js / React Router), discovers routes from sitemap.xml and your file structure, and optionally collects Slack and GitHub credentials.

Alternative — manual setup: Create a .env with TARGET_DEV_URL and optionally TARGET_STAGING_URL.

3. Start Chrome with remote debugging

Same as Option A — see above.

4. Slack notifications (optional)

Same as Option A — see above.

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Option C — Clone the Repository (full source / contributors)

1. Clone and install

git clone https://github.com/ironclawdevs27/Argus.git
cd Argus
npm install
npm run setup   # creates reports/ directory

2. Environment variables

Recommended — use the interactive setup wizard:

npm run init

Alternative — manual setup:

cp .env.example .env

Open .env and fill in:

TARGET_DEV_URL=http://localhost:3000
TARGET_STAGING_URL=https://staging.yourapp.com   # leave blank → CSS-only analysis mode

# Slack — OPTIONAL. Omit to get a local report.html instead.
# SLACK_BOT_TOKEN=xoxb-...
# SLACK_SIGNING_SECRET=...
# SLACK_CHANNEL_CRITICAL=C0000000000
# SLACK_CHANNEL_WARNINGS=C0000000001
# SLACK_CHANNEL_DIGEST=C0000000002

3. Configure routes

If you ran npm run init — skip this step.

Otherwise, edit src/config/targets.js:

export const routes = [
  { path: '/',          name: 'Home',      critical: true,  waitFor: 'main' },
  { path: '/login',     name: 'Login',     critical: true,  waitFor: 'form' },
  { path: '/dashboard', name: 'Dashboard', critical: true,  waitFor: '[data-testid="dashboard"]' },
  { path: '/settings',  name: 'Settings',  critical: false, waitFor: null },
];

• critical: true — errors on this route go to #bugs-critical
• waitFor — CSS selector Argus waits for before capturing (signals the page is ready)

4. Connect Chrome DevTools MCP to Claude Code

claude mcp add chrome-devtools -- npx chrome-devtools-mcp@latest

Verify — ask Claude: "List all open Chrome pages" — you should see your tabs.

5. Start Chrome with remote debugging

Same as Option A — see above.

6. Slack notifications (optional)

Same as Option A — see above.

---

Running Argus

Option A — Via MCP (Claude Code / any MCP client)

Ask Claude directly — no terminal needed.

Available tools:

Tool	What it does
argus_audit	Fast QA pass — JS errors, network failures, accessibility, SEO, security, CSS, content
argus_audit_full	Deep QA pass — adds Lighthouse, responsive layout checks across 4 viewports, memory leak detection, hover-state bug detection, and accessibility tree snapshot
argus_compare	Diff dev vs staging — screenshots, findings delta, environment regressions
argus_last_report	Return the last saved JSON report without re-running a scan
argus_watch_snapshot	Snapshot the currently open Chrome tab without navigating — raw console + network capture
argus_get_context	Capture everything broken on the open tab, formatted as a diagnostic context for Claude to diagnose and suggest fixes

argus_audit — fast audit of any URL:

Run argus_audit on http://localhost:3000/checkout
Run argus_audit on http://localhost:3000/login with critical: true

argus_audit_full — deep audit with Lighthouse + memory + responsive checks:

Run argus_audit_full on http://localhost:3000/dashboard

argus_compare — dev vs staging diff (reads TARGET_DEV_URL and TARGET_STAGING_URL from .env):

Run argus_compare

argus_last_report — retrieve last audit without re-running Chrome:

Run argus_last_report

argus_watch_snapshot — snapshot the currently open tab without navigating. Useful when the page is in an authenticated or post-interaction state that navigation would reset:

Run argus_watch_snapshot
Run argus_watch_snapshot with url: http://localhost:3000

argus_get_context — when your app is stuck or throwing errors, run this to capture everything that's broken and feed it to Claude for diagnosis:

Run argus_get_context

Then follow with: "Here's the context — what's causing these errors and how do I fix them?"

---

Option B & C — Via CLI / npm scripts

Available commands:

Command	What it does
npm run crawl	Multi-page batch audit of all routes in targets.js
npm run compare	Dev vs staging diff (or CSS analysis if no TARGET_STAGING_URL)
npm run watch	Passive monitor — polls the open Chrome tab every 1s, no navigation
npm run report:html	Generate reports/report.html from the latest JSON audit
npm run server	Start the Slack slash command + interaction server (port 3001)
npm run init	Interactive setup wizard — generates .env + targets.js
npm run test:unit	Run 61 unit tests (no Chrome required)
npm run test:harness	Run 82-block correctness harness (requires Chrome)

npm run crawl — full audit of all configured routes:

npm run crawl

Reports are saved to reports/ as JSON files. Run npm run report:html after any crawl for a portable reports/report.html with all screenshots inlined — useful for sharing with designers or reviewing offline.

npm run compare — dev vs staging diff:

npm run compare

When TARGET_STAGING_URL is not set, automatically switches to CSS analysis mode — cascade overrides, component style leaks, unused rules, and React inline style conflicts on the dev environment only.

npm run watch — passive monitoring (polls every 1s, no navigation):

Attaches to whatever Chrome tab is open and reports new issues in real time without navigating anywhere. Use this while developing.

Requires 2 terminals:
  Terminal 1 — your app (npm start / npm run dev)
  Terminal 2 — npm run watch

Steps:

1. Open Chrome and navigate to your app
2. Terminal 1: start your application
3. Terminal 2: npm run watch — Argus begins polling
4. Develop normally — console errors, network failures (4xx/5xx), CORS blocks, and auth failures print in real time
5. Ctrl+C — stops the monitor and writes reports/report.html

# Attribute findings to a specific URL:
npm run watch http://localhost:4000

Variable	Default	Description
ARGUS_WATCH_INTERVAL_MS	1000	Poll interval in milliseconds
TARGET_DEV_URL	http://localhost:3000	URL attributed to findings when none passed

npm run report:html — generate HTML dashboard from last audit:

npm run report:html
# → reports/report.html (all findings + inline screenshots, portable, no server needed)

---

Option D — From Slack (on-demand)

/argus-retest https://staging.yourapp.com/checkout

BugBot responds immediately, runs the test, and posts results back. Detailed bug reports go to #bugs-critical. See Slack Slash Command Setup for configuration.

---

CSS Analysis Mode

When TARGET_STAGING_URL is not set in .env, npm run compare automatically switches to CSS analysis mode instead of comparing two environments.

What it analyzes on your dev environment:

Check	What it catches
Cascade overrides	Same CSS property declared multiple times on an element; !important flagged as warning
Component style leaks	BEM selector (.card__title) found in a stylesheet that doesn't belong to that component
Unused rules	CSS selectors that match no element on the current page
CSS Modules	Detects hashed class names; extracts readable component names (Button, Card, etc.)
React inline style conflicts	style="" attribute overriding a stylesheet declaration on the same element
SCSS source maps	Traces compiled CSS back to original .scss files where source maps are available

API frequency analysis also runs automatically:

Call count	Severity	Likely cause
2 calls	info	Possible prefetch + actual — verify intentional
3–4 calls	warning	Double-fetch — check useEffect deps or component re-mounts
5+ calls	critical	Runaway loop — missing cleanup, infinite re-render

---

Performance Budgets

Argus enforces these thresholds on every crawl:

Metric	Threshold	Severity
LCP (Largest Contentful Paint)	< 2500ms	warning
CLS (Cumulative Layout Shift)	< 0.1	warning
FID / TBT (interaction latency)	< 100ms	warning
TTFB (Time to First Byte)	< 800ms	warning

Violations are reported as individual warning bugs with the measured value.

---

Lighthouse Suite

Runs all four Lighthouse categories on every route:

• Accessibility — score < 50 → critical; score < 90 → warning
• Performance — score < 90 → warning
• SEO — score < 90 → warning
• Best Practices — score < 90 → warning

Individual failing audit items (e.g., missing alt text, low contrast, render-blocking resources) are surfaced as separate findings alongside the category score.

---

Slack Channel Routing

Slack is optional. When SLACK_BOT_TOKEN is not set, Argus skips Slack entirely and auto-generates a local report.html (all findings + inline screenshots) and opens it in the default browser. No Slack setup needed to start using Argus.

When Slack is configured, findings are routed by severity:

Severity	Channel	When
critical	#bugs-critical	JS exceptions, HTTP 5xx, blank page, auth failure, API called 5+ times, Lighthouse accessibility < 50, auth token in storage/URL, responsive overflow, slow API > 3s, payload > 2MB, > 100 detached DOM nodes, CORS policy violations, debugger; statements in production code, blocked mixed content (HTTP resource on HTTPS page)
warning	#bugs-warnings	Visual regression > 0.5%, HTTP 4xx, CSS overrides with !important, API called 3–4×, Lighthouse scores < 90, missing SEO/OG tags, missing security headers, placeholder content, touch targets too small, slow API > 1s, payload > 500KB, > 10 detached DOM nodes, redirect chains > 2 hops, broken links, sync XHR, document.write, long tasks > 50ms, SW registration failures, duplicate id attributes, passive mixed content (images/audio on HTTPS page)
info	#bugs-digest	Console warnings, unused CSS rules, API summaries, CSS Modules detection, empty data lists, responsive screenshot grid, missing cache headers on static assets

Each message includes:

• Severity badge + affected URL + timestamp
• AI-generated description
• Inline screenshot (uploaded directly to Slack — no external hosting)
• View Page, Acknowledge, and Retest action buttons

---

Slack Slash Command Setup

To use /argus-retest from Slack, you need to expose the Argus server publicly.

Step 1 — Start the server

npm run server

Server runs on port 3001.

Step 2 — Expose with Cloudflare Tunnel

Download cloudflared (free, no account needed), then:

cloudflared tunnel --url http://localhost:3001

Alternatively, with no install at all (SSH tunnel):

ssh -R 80:localhost:3001 [email protected]

Copy the public HTTPS URL that appears.

Step 3 — Configure Slack App

1. api.slack.com/apps → BugBot → Slash Commands → Create New Command:

   • Command: /argus-retest
   • Request URL: https://your-public-url/slack/commands
   • Description: Run Argus regression test on a URL
   • Usage hint: <url>

2. Interactivity & Shortcuts → Enable → Request URL: https://your-public-url/slack/interactions

3. OAuth & Permissions → Reinstall to Workspace

Step 4 — Test

/argus-retest http://localhost:3000

BugBot should reply within 3 seconds with a "running" acknowledgement, then post results.

---

GitHub Actions CI Setup

Add secrets to your repository

Go to GitHub repo → Settings → Secrets and variables → Actions → add:

Secret name	Required	Value
SLACK_BOT_TOKEN	No	Your xoxb-... token. Omit entirely to use Slack-optional mode — Argus generates report.html instead
SLACK_SIGNING_SECRET	No*	From Slack App → Basic Information (only needed for /argus-retest slash command)
SLACK_CHANNEL_CRITICAL	No*	Channel ID (required when Slack is configured)
SLACK_CHANNEL_WARNINGS	No*	Channel ID (required when Slack is configured)
SLACK_CHANNEL_DIGEST	No*	Channel ID (required when Slack is configured)
TARGET_STAGING_URL	Yes	Your staging base URL
GITHUB_TOKEN	No	For C2 PR integration — auto-injected by GitHub Actions as secrets.GITHUB_TOKEN
GITHUB_REPOSITORY	No	For C2 PR integration — owner/repo format (e.g., acme/my-app)

C2 PR integration: when GITHUB_TOKEN and GITHUB_REPOSITORY are set, Argus posts a PR comment and commit status check for every crawl. GITHUB_PR_NUMBER is injected automatically by the workflow from github.event.pull_request.number. The included workflow does not wire these up by default — add them to the env: block in .github/workflows/argus.yml if you want PR-level comments.

The workflow at .github/workflows/argus.yml runs:

• On every push to main / master
• Daily at 6 AM UTC (before the team starts work)
• Manually via Actions → Run workflow (with optional URL override)

If critical issues are found, the pipeline fails — preventing silent regressions from being missed.

---

Project Structure

argus/
├── .env                              # Your secrets (never commit this)
├── .env.example                      # Template — copy to .env
├── .gitignore
├── package.json
├── README.md
├── .claude/
│   └── settings.json                 # Claude Code permission config (auto-approve node/npm/reports)
├── .github/
│   └── workflows/
│       └── argus.yml                 # CI pipeline
├── .vscode/
│   └── mcp.json                      # Chrome DevTools MCP config for VS Code
├── .mcp.json                         # Argus MCP server registration — exposes argus_audit/argus_audit_full/argus_compare/argus_last_report to Claude
├── src/
│   ├── argus.js                      # Single-page audit entry point
│   ├── batch-runner.js               # Multi-page batch audit
│   ├── mcp-server.js                 # Argus MCP server — argus_audit / argus_audit_full / argus_compare / argus_last_report
│   ├── adapters/
│   │   └── browser.js                # CdpBrowserAdapter — facade over all chrome-devtools-mcp calls
│   ├── domain/
│   │   └── finding.js                # createFinding() factory — canonical finding shape
│   ├── registry.js                   # Analyzer plugin registry — registerExpensive/getCheap/getExpensive
│   ├── config/
│   │   ├── targets.js                # Routes to test, thresholds, config
│   │   └── schema.js                 # Zod validation schema; validateConfig() called inside runCrawl()
│   ├── orchestration/
│   │   ├── crawl-and-report.js       # Backward-compat re-export shell → orchestrator + report-processor + dispatcher
│   │   ├── orchestrator.js           # Crawl loop, route/flow crawl, runCrawl()
│   │   ├── report-processor.js       # Dedup → severity overrides → baseline → JSON write
│   │   ├── dispatcher.js             # Slack / GitHub / HTML dispatch
│   │   ├── env-comparison.js         # Dev vs staging diff + CSS analysis mode
│   │   ├── watch-mode.js             # Passive browser monitoring (WatchSession + runWatchMode)
│   │   └── slack-notifier.js         # Slack Block Kit dispatcher
│   ├── server/
│   │   ├── index.js                  # Express server (port 3001)
│   │   ├── slash-command-handler.js  # /argus-retest handler
│   │   └── interaction-handler.js    # Acknowledge + Retest button handler
│   ├── utils/
│   │   ├── css-analyzer.js           # CSS analysis script injected into the browser
│   │   ├── seo-analyzer.js           # SEO checks: meta, OG tags, h1, canonical, viewport
│   │   ├── security-analyzer.js      # Security: localStorage tokens, eval(), headers, cookies
│   │   ├── content-analyzer.js       # Content quality: null text, placeholders, broken images
│   │   ├── responsive-analyzer.js    # Responsive: overflow + touch targets at 4 breakpoints
│   │   ├── memory-analyzer.js        # Memory leaks: V8 heap snapshot + heap growth
│   │   ├── logger.js                 # Pino structured logger — childLogger(module)│   │   ├── retry.js                  # withRetry() exponential backoff — navigate/fill only; Number.isFinite guard│   │   ├── telemetry.js              # OTel tracing + metrics — startSpan() / recordFinding() / recordFlaky() / recordNewFindings(); no-op default│   │   ├── session-manager.js        # Auth: backward-compat re-export barrel│   │   ├── session-persistence.js    # Auth: saveSession (mkdirSync+atomic write), restoreSession, hasSession, clearSession│   │   ├── login-orchestrator.js     # Auth: runLoginFlow, refreshSession + lock file│   │   ├── baseline-manager.js       # Baselines: loadBaseline, saveBaseline, applyBaseline, appendTrend
│   │   ├── flakiness-detector.js     # Flakiness: mergeRunResults — confirmed vs flaky per double-crawl
│   │   ├── flow-runner.js            # User flow assertions: runFlow / runAllFlows — assert DSL
│   │   ├── html-reporter.js          # HTML dashboard: generateHtmlReport() + npm run report:html (D7.1 / D7.7)
│   │   ├── parallel-crawler.js       # chunkArray sharding utility (ARGUS_CONCURRENCY=N parallel crawl)
│   │   ├── contract-validator.js     # API contract validation: validateSchema, matchesContract (D7.4)
│   │   ├── severity-overrides.js     # Severity policy overrides: applyOverrides (D7.5)
│   │   ├── slack-guard.js            # Slack-optional guard: isSlackConfigured() (D7.7)
│   │   ├── hover-analyzer.js         # Hover-state bug detection — aria-haspopup + data-tooltip (D8.1)
│   │   ├── snapshot-analyzer.js      # Accessibility tree snapshot — missing names, labels, landmarks, heading hierarchy, ARIA state (D8.2 + v6)
│   │   ├── issues-analyzer.js        # Chrome DevTools Issues panel — CSP/deprecated/cookie issues
│   │   ├── network-timing-analyzer.js # HAR timing analysis — slow third-party detection
│   │   ├── keyboard-analyzer.js      # Keyboard Tab-walk — focus_visible_missing, focus_lost
│   │   ├── codebase-analyzer.js      # Codebase cross-reference — env vars, feature flags, dead routes (C1)
│   │   ├── github-reporter.js        # GitHub PR comment + commit status integration (C2)
│   │   ├── route-discoverer.js       # Auto route discovery — sitemap + Next.js + React Router (C3)
│   │   ├── diff.js                   # pixelmatch screenshot + DOM/network diff utilities
│   │   ├── mcp-parsers.js            # Text-format parsers for list_console_messages + list_network_requests (v9)
│   │   └── mcp-client.js             # Headless JSON-RPC MCP client for CI mode
│   └── cli/
│       └── init.js                   # argus init setup wizard — detect framework, discover routes, write .env + targets.js (C4)
├── test/
│   └── unit/                         # Vitest unit tests — no Chrome required
│       ├── finding.test.js           # createFinding() — fields, throws, frozen, extra fields (8 tests)
│       ├── config-schema.test.js     # validateConfig() + ConfigSchema.safeParse (8 tests)
│       ├── report-processor.test.js  # deduplicateFindings + rebuildSummary (11 tests)
│       ├── flakiness-detector.test.js # findingKey normalization + mergeRunResults (13 tests)
│       ├── baseline-manager.test.js  # loadBaseline/saveBaseline/applyBaseline (9 tests)
│       └── flow-runner.test.js       # normalizeArray (pure) + runFlow mock browser (11 tests)
├── landing/                          # Product landing page (React 18 + Vite + Tailwind + Framer Motion)
│   ├── src/
│   │   ├── App.jsx                   # Single-page app — hero, features, comparison, waitlist + enterprise modals
│   │   └── supabase.js               # Supabase client factory (null-safe when env vars missing)
│   ├── public/
│   │   ├── favicon.svg               # SVG favicon — purple ring + dot
│   │   ├── argus-poster.png          # Video poster fallback (1918×1078)
│   │   ├── og-image-v2.jpg           # OG social card — 1200×630 JPEG, branded overlay, black-outlined stat numbers
│   │   ├── robots.txt                # Allows all crawlers; Sitemap reference
│   │   └── sitemap.xml               # Canonical URL for argus-qa.com/
│   ├── index.html                    # Vite entry; OG/Twitter/JSON-LD SEO tags; canonical; favicon
│   ├── package.json
│   ├── .env.example                  # VITE_SUPABASE_URL + VITE_SUPABASE_ANON_KEY template
│   └── README.md                     # Setup guide, Supabase SQL schema, env vars, deployment
├── scripts/
│   └── dispatch-report.js            # Standalone Slack re-dispatch script (re-posts last report.json to Slack)
├── test-harness/                     # Fixture server + test runner (83 blocks, 360 hard assertions, 54 fixture pages)
│   ├── README.md
│   ├── server.js                     # Express fixture server (ports 3100 dev / 3101 staging)
│   ├── harness-config.js             # Route definitions + expected findings
│   ├── validate.js                   # Test runner — 83 numbered blocks ([80] MCP server, [81] createFinding, [82] withRetry, [83] watch dashboard)
│   ├── pages/                        # 54 fixture pages (one per detection category)
│   ├── nextjs-fixture/               # Next.js app structure for C3 discovery tests (10 files)
│   ├── source-fixture/               # Minimal app.js for C1 codebase-analyzer tests (env var audit)
│   └── static/
│       └── button-styles.css         # BEM card selectors in button file → component leak
└── reports/                          # Output: JSON reports + screenshots (gitignored)
    ├── baselines/
    │   ├── <branch>.json             # Per-route finding keys — per git branch (D7.2)
    │   └── <branch>-trends.json      # Append-only run history per branch (D7.2)
    └── .gitkeep

---

Key Technical Decisions

Decision	Choice	Reason
Screenshot comparison	pixelmatch + AI classification	pixelmatch is fast and deterministic; Claude removes false positives from anti-aliasing and dynamic content
Slack API	Bot API, not Incoming Webhooks	Bot API supports file uploads, message updates, interactive buttons, and threads
File uploads	files.getUploadURLExternal + PUT + files.completeUploadExternal	files.upload is deprecated; pre-signed URL requires PUT — POST silently produces broken files
CSS analysis	Script injected via evaluate_script	Runs in page context so it sees the live computed styles, CSS Modules hashes, and React fiber properties
Responsive viewport	emulate (not resize_page)	resize_page only resizes the browser window and does not update CSS viewport width — emulate is the correct API
Viewport width measurement	document.documentElement.clientWidth	After emulate with mobile flag, window.innerWidth returns the legacy layout viewport (~952px), not the device width
V8 heap snapshot	take_memory_snapshot({ filePath }) → read from disk	The MCP tool writes JSON to disk (not inline); parse with JSON.parse(fs.readFileSync(filePath)) then delete the temp file
Detached DOM detection	Walk flat nodes array for "Detached " prefix in strings table	Chrome serializes detached elements as "Detached HTMLDivElement" etc.; secondary check on detachedness === 2 (Chrome 90+)
Baseline finding key	type::message[:100]::status	Excludes timestamps and dynamic URL path IDs; message truncated to 100 chars to handle slight wording variations; ::status suffix only added when non-null
Baseline alert filter	isNew === true (strict)	Only findings explicitly marked new by applyBaseline are dispatched to Slack — prevents stale re-dispatch if baseline-manager is not called (fails silently rather than spamming)
Flakiness routing	severity: 'info' for flaky findings	Downgrading severity means existing dispatchToSlack routing sends them to the info digest with zero routing changes — only the :zap: _flaky_ label needed
Private findingKey per module	Each of baseline-manager.js and flakiness-detector.js has its own copy	Avoids coupling two independently-useful modules via a shared export for a trivial 3-line function
Runtime anti-pattern injection	addScriptToEvaluateOnNewDocument via MCP	Scripts registered this way run in the new page context before any page script — intercepts XMLHttpRequest.open, document.write, and navigator.serviceWorker.register before the page can call them
CORS error detection	list_console_messages + text match, not in-page intercept	CORS errors are generated by the browser itself, not by page JS — console.error patcher misses them; the MCP console log captures them
Long task detection	PerformanceObserver({ entryTypes: ['longtask'] }) injected before load	Only the duration is included in the finding message (not startTime) — ensures identical tasks on two crawl runs produce the same dedup key
CI MCP client	JSON-RPC over stdio	In CI there's no Claude Code agent — the headless client replaces it with the same API surface
Node.js	v20.19+	Minimum required by Chrome DevTools MCP

---

Known MCP Tool Limitations

The Chrome DevTools MCP behavioral constraints below cause 3 permanent test failures in the harness (357/360 pass). These are MCP-layer restrictions — they cannot be fixed in Argus code.

type_text clarification: type_text does fire DOM input events when the element is properly focused first with mcp.click({ uid }). Always use uid-based focus — passing { selector } to mcp.click silently does nothing.

Tool	Constraint	Impact
drag	Uses mouse simulation, not HTML5 DnD API	dragstart/dragover/drop events never fire
list_console_messages({ types: ['issue'] })	Issues panel returns empty even when violations exist	CSP and deprecated-API detection is unreliable

These constraints are documented with workarounds in SKILL.md §10.

---

Environment Variables Reference

Variable	Required	Description
SLACK_BOT_TOKEN	No	xoxb-... Bot User OAuth Token. Omit to enable Slack-optional mode — Argus generates report.html and opens it in the browser instead
SLACK_SIGNING_SECRET	No*	Verifies slash command / interaction requests from Slack (required only when using /argus-retest)
SLACK_CHANNEL_CRITICAL	No*	Channel ID for critical bugs (required when Slack is configured)
SLACK_CHANNEL_WARNINGS	No*	Channel ID for warnings (required when Slack is configured)
SLACK_CHANNEL_DIGEST	No*	Channel ID for info / daily digest (required when Slack is configured)
TARGET_DEV_URL	Yes	Base URL of your dev environment
TARGET_STAGING_URL	No	Base URL of staging. If blank → CSS analysis mode
SCREENSHOT_DIFF_THRESHOLD	No	Pixel diff % to flag (default: 0.5)
REPORT_OUTPUT_DIR	No	Where to write reports (default: ./reports)
ARGUS_CONCURRENCY	No	Number of parallel MCP clients for route crawling (default: 1 = sequential)
PORT	No	Server port (default: 3001)
ARGUS_LOG_LEVEL	No	Pino log level — trace, debug, info, warn, error, fatal (default: info)
ARGUS_LOG_PRETTY	No	Set to 1 for human-readable log output instead of JSON (dev mode)
ARGUS_RETRY_ATTEMPTS	No	Max retry attempts for navigate/fill MCP calls (default: 3)
OTEL_EXPORTER_OTLP_ENDPOINT	No	OTLP collector endpoint — enables span/metric export to Jaeger, Grafana Tempo, Datadog, etc.
ARGUS_OTEL_CONSOLE	No	Set to 1 to print OTel spans to stdout without an OTLP endpoint (dev tracing)
ARGUS_WATCH_INTERVAL_MS	No	Watch mode poll interval in milliseconds (default: 1000)
ARGUS_SOURCE_DIR	No	Path to your app's source directory — enables codebase cross-reference (env var detection, feature flag leakage, dead routes)
ARGUS_ENV_FILE	No	Path to your app's .env file — C1 cross-references env vars used in source code against this file to detect missing declarations
GITHUB_TOKEN	No	GitHub personal access token — required for PR comment + commit status integration
GITHUB_REPOSITORY	No	Repository in owner/repo format — required for GitHub PR integration
GITHUB_SHA	No	Commit SHA for the commit status check — injected automatically by GitHub Actions (${{ github.sha }})
GITHUB_PR_NUMBER	No	PR number for comment targeting — set via ${{ github.event.pull_request.number }} in your workflow
ARGUS_REPORT_URL	No	Full URL to the hosted HTML report — linked from the GitHub commit status check

---

Troubleshooting

Chrome DevTools MCP not connecting

claude mcp add chrome-devtools -- npx chrome-devtools-mcp@latest
# Then restart Claude Code

Slack messages not posting

• Confirm SLACK_BOT_TOKEN starts with xoxb- (not xoxp-, xoxe-, or xapp-)
• Verify BugBot is invited to each channel: /invite @BugBot
• Check token scopes: chat:write, files:write, files:read

Screenshots not appearing in Slack messages

• The upload uses a pre-signed URL that requires PUT, not POST — if you see a broken image, check that the Slack token has files:write scope and the channel is correct

Slash command returns "dispatch_failed"

• Your tunnel URL has changed (Cloudflare Tunnel / localhost.run URLs change on restart)
• Update the Request URL in Slack App → Slash Commands and reinstall

CSS analysis returns empty results

• Page may be behind auth — make sure you're logged in on the Chrome instance Argus is controlling
• Cross-origin stylesheets (CDN fonts, third-party widgets) can't be read due to browser security restrictions — this is expected

Screenshots are blank

• Page hasn't finished loading — increase pageSettleMs in src/config/targets.js
• Add a waitFor selector for that route

CI pipeline fails immediately

• Chrome may not be starting fast enough — increase the sleep 3 after Chrome launch to sleep 5 in .github/workflows/argus.yml

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How Argus Differs From Playwright / Cypress

Argus is not a replacement for unit or E2E tests. It's a complementary layer:

	Playwright / Cypress	Argus
Tests	Your logic and API contracts	What the user actually sees
Catches	Regression in behaviour	CSS drift, visual regressions, API redundancy, console noise, perf budgets
Runs	In your test suite	Continuously, on the live running app
Setup	Write test files	Configure routes in targets.js
Output	Pass / fail	Structured Slack reports with screenshots and action buttons

They complement each other — Argus catches what test suites miss.