OpenCLI Browser — Browser Automation for AI Agents

Control Chrome step-by-step via CLI. Reuses existing login sessions — no passwords needed.

Prerequisites

opencli doctor    # Verify extension + daemon connectivity

Requires: Chrome running + OpenCLI Browser Bridge extension installed.

Critical Rules

1. ALWAYS use state to inspect the page, NEVER use screenshot — state returns structured DOM with [N] element indices, is instant and costs zero tokens. screenshot requires vision processing and is slow. Only use screenshot when the user explicitly asks to save a visual.
2. ALWAYS use click/type/select for interaction, NEVER use eval to click or type — eval "el.click()" bypasses scrollIntoView and CDP click pipeline, causing failures on off-screen elements. Use state to find the [N] index, then click <N>.
3. Verify inputs with get value, not screenshots — after type, run get value <index> to confirm.
4. Run state after every page change — after open, click (on links), scroll, always run state to see the new elements and their indices. Never guess indices.
5. Chain commands aggressively with && — combine open + state, multiple type calls, and type + get value into single && chains. Each tool call has overhead; chaining cuts it.
6. eval is read-only — use eval ONLY for data extraction (JSON.stringify(...)), never for clicking, typing, or navigating. Always wrap in IIFE to avoid variable conflicts: eval "(function(){ const x = ...; return JSON.stringify(x); })()".
7. Minimize total tool calls — plan your sequence before acting. A good task completion uses 3-5 tool calls, not 15-20. Combine open + state as one call. Combine type + type + click as one call. Only run state separately when you need to discover new indices.
8. Prefer network to discover APIs — most sites have JSON APIs. API-based adapters are more reliable than DOM scraping.

Command Cost Guide

Cost	Commands	When to use
Free & instant	state, get *, eval, network, scroll, keys	Default — use these
Free but changes page	open, click, type, select, back	Interaction — run state after
Expensive (vision tokens)	screenshot	ONLY when user needs a saved image

Action Chaining Rules

Commands can be chained with &&. The browser persists via daemon, so chaining is safe.

Always chain when possible — fewer tool calls = faster completion:

# GOOD: open + inspect in one call (saves 1 round trip)
opencli browser open https://example.com && opencli browser state

# GOOD: fill form in one call (saves 2 round trips)
opencli browser type 3 "hello" && opencli browser type 4 "world" && opencli browser click 7

# GOOD: type + verify in one call
opencli browser type 5 "test@example.com" && opencli browser get value 5

# GOOD: click + wait + state in one call (for page-changing clicks)
opencli browser click 12 && opencli browser wait time 1 && opencli browser state

# BAD: separate calls for each action (wasteful)
opencli browser type 3 "hello"    # Don't do this
opencli browser type 4 "world"    # when you can chain
opencli browser click 7            # all three together

Page-changing — always put last in a chain (subsequent commands see stale indices):

• open <url>, back, click <link/button that navigates>

Rule: Chain when you already know the indices. Run state separately when you need to discover indices first.

Core Workflow

1. Navigate: opencli browser open <url>
2. Inspect: opencli browser state → elements with [N] indices
3. Interact: use indices — click, type, select, keys
4. Wait (if needed): opencli browser wait selector ".loaded" or wait text "Success"
5. Verify: opencli browser state or opencli browser get value <N>
6. Repeat: browser stays open between commands
7. Save: write a TS adapter to ~/.opencli/clis/<site>/<command>.ts

Commands

Navigation

opencli browser open <url>              # Open URL (page-changing)
opencli browser back                    # Go back (page-changing)
opencli browser scroll down             # Scroll (up/down, --amount N)
opencli browser scroll up --amount 1000

Inspect (free & instant)

opencli browser state                   # Structured DOM with [N] indices — PRIMARY tool
opencli browser screenshot [path.png]   # Save visual to file — ONLY for user deliverables

Get (free & instant)

opencli browser get title               # Page title
opencli browser get url                 # Current URL
opencli browser get text <index>        # Element text content
opencli browser get value <index>       # Input/textarea value (use to verify after type)
opencli browser get html                # Full page HTML
opencli browser get html --selector "h1" # Scoped HTML
opencli browser get attributes <index>  # Element attributes

Interact

opencli browser click <index>           # Click element [N]
opencli browser type <index> "text"     # Type into element [N]
opencli browser select <index> "option" # Select dropdown
opencli browser keys "Enter"            # Press key (Enter, Escape, Tab, Control+a)

Wait

Three variants — use the right one for the situation:

opencli browser wait time 3                       # Wait N seconds (fixed delay)
opencli browser wait selector ".loaded"            # Wait until element appears in DOM
opencli browser wait selector ".spinner" --timeout 5000  # With timeout (default 30s)
opencli browser wait text "Success"                # Wait until text appears on page

When to wait: After open on SPAs, after click that triggers async loading, before eval on dynamically rendered content.

Extract (free & instant, read-only)

Use eval ONLY for reading data. Never use it to click, type, or navigate.

opencli browser eval "document.title"
opencli browser eval "JSON.stringify([...document.querySelectorAll('h2')].map(e => e.textContent))"

# IMPORTANT: wrap complex logic in IIFE to avoid "already declared" errors
opencli browser eval "(function(){ const items = [...document.querySelectorAll('.item')]; return JSON.stringify(items.map(e => e.textContent)); })()"

Selector safety: Always use fallback selectors — querySelector returns null on miss:

# BAD: crashes if selector misses
opencli browser eval "document.querySelector('.title').textContent"

# GOOD: fallback with || or ?.
opencli browser eval "(document.querySelector('.title') || document.querySelector('h1') || {textContent:''}).textContent"
opencli browser eval "document.querySelector('.title')?.textContent ?? 'not found'"

Network (API Discovery)

opencli browser network                  # Show captured API requests (auto-captured since open)
opencli browser network --detail 3       # Show full response body of request #3
opencli browser network --all            # Include static resources

Sedimentation (Save as CLI)

opencli browser init hn/top              # Generate adapter scaffold at ~/.opencli/clis/hn/top.ts
opencli browser verify hn/top            # Test the adapter (adds --limit 3 only if `limit` arg is defined)

• init auto-detects the domain from the active browser session (no need to specify it)
• init creates the file + populates site, name, domain, and columns from current page
• verify runs the adapter end-to-end and prints output; if no limit arg exists in the adapter, it won't pass --limit 3

Session

opencli browser close                   # Close automation window

Example: Extract HN Stories

opencli browser open https://news.ycombinator.com
opencli browser state                   # See [1] a "Story 1", [2] a "Story 2"...
opencli browser eval "JSON.stringify([...document.querySelectorAll('.titleline a')].slice(0,5).map(a => ({title: a.textContent, url: a.href})))"
opencli browser close

Example: Fill a Form

opencli browser open https://httpbin.org/forms/post
opencli browser state                   # See [3] input "Customer Name", [4] input "Telephone"
opencli browser type 3 "OpenCLI" && opencli browser type 4 "555-0100"
opencli browser get value 3             # Verify: "OpenCLI"
opencli browser close

Saving as Reusable CLI — Complete Workflow

Step-by-step sedimentation flow:

# 1. Explore the website
opencli browser open https://news.ycombinator.com
opencli browser state                          # Understand DOM structure

# 2. Discover APIs (crucial for high-quality adapters)
opencli browser eval "fetch('/api/...').then(r=>r.json())"   # Trigger API calls
opencli browser network                        # See captured API requests
opencli browser network --detail 0             # Inspect response body

# 3. Generate scaffold
opencli browser init hn/top                    # Creates ~/.opencli/clis/hn/top.ts

# 4. Edit the adapter (fill in func logic)
# - If API found: use fetch() directly (Strategy.PUBLIC or COOKIE)
# - If no API: use page.evaluate() for DOM extraction (Strategy.UI)

# 5. Verify
opencli browser verify hn/top                  # Runs the adapter and shows output

# 6. If verify fails, edit and retry
# 7. Close when done
opencli browser close

Example adapter:

// ~/.opencli/clis/hn/top.ts
import { cli, Strategy } from '@jackwener/opencli/registry';

cli({
  site: 'hn',
  name: 'top',
  description: 'Top Hacker News stories',
  domain: 'news.ycombinator.com',
  strategy: Strategy.PUBLIC,
  browser: false,
  args: [{ name: 'limit', type: 'int', default: 5 }],
  columns: ['rank', 'title', 'score', 'url'],
  func: async (_page, kwargs) => {
    const limit = Math.min(Math.max(1, kwargs.limit ?? 5), 50);
    const resp = await fetch('https://hacker-news.firebaseio.com/v0/topstories.json');
    const ids = await resp.json();
    return Promise.all(
      ids.slice(0, limit).map(async (id: number, i: number) => {
        const item = await (await fetch(`https://hacker-news.firebaseio.com/v0/item/${id}.json`)).json();
        return { rank: i + 1, title: item.title, score: item.score, url: item.url ?? '' };
      })
    );
  },
});

Save to ~/.opencli/clis/<site>/<command>.ts → immediately available as opencli <site> <command>.

Strategy Guide

Strategy	When	browser:
Strategy.PUBLIC	Public API, no auth	false
Strategy.COOKIE	Needs login cookies	true
Strategy.UI	Direct DOM interaction	true

Always prefer API over UI — if you discovered an API during browsing, use fetch() directly.

Tips

1. Always state first — never guess element indices, always inspect first
2. Sessions persist — browser stays open between commands, no need to re-open
3. Use eval for data extraction — eval "JSON.stringify(...)" is faster than multiple get calls
4. Use network to find APIs — JSON APIs are more reliable than DOM scraping
5. Alias: opencli op is shorthand for opencli browser

Common Pitfalls

1. form.submit() fails in automation — Don't use form.submit() or eval to submit forms. Navigate directly to the search URL instead:

   # BAD: form.submit() often silently fails
   opencli browser eval "document.querySelector('form').submit()"
   # GOOD: construct the URL and navigate
   opencli browser open "https://github.com/search?q=opencli&type=repositories"
   

2. GitHub DOM changes frequently — Prefer data-testid attributes when available; they are more stable than class names or tag structure.

3. SPA pages need wait before extraction — After open or click on single-page apps, the DOM isn't ready immediately. Always wait selector or wait text before eval.

4. Use state before clicking — Run opencli browser state to inspect available interactive elements and their indices. Never guess indices from memory.

5. evaluate runs in browser context — page.evaluate() in adapters executes inside the browser. Node.js APIs (fs, path, process) are NOT available. Use fetch() for network calls, DOM APIs for page data.

6. Backticks in page.evaluate break JSON storage — When writing adapters that will be stored/transported as JSON, avoid template literals inside page.evaluate. Use string concatenation or function-style evaluate:

   // BAD: template literal backticks break when adapter is in JSON
   page.evaluate(`document.querySelector("${selector}")`)
   // GOOD: function-style evaluate
   page.evaluate((sel) => document.querySelector(sel), selector)
   

Troubleshooting

Error	Fix
"Browser not connected"	Run opencli doctor
"attach failed: chrome-extension://"	Disable 1Password temporarily
Element not found	opencli browser scroll down && opencli browser state
Stale indices after page change	Run opencli browser state again to get fresh indices