Browser Automation

Browser Automation

CRITICAL RULES — VIOLATIONS WILL BREAK THE WORKFLOW:

1. Never run midscene commands in the background. Each command must run synchronously so you can read its output (especially screenshots) before deciding the next action. Background execution breaks the screenshot-analyze-act loop.
2. Run only one midscene command at a time. Wait for the previous command to finish, read the screenshot, then decide the next action. Never chain multiple commands together.
3. Allow enough time for each command to complete. Midscene commands involve AI inference and screen interaction, which can take longer than typical shell commands. A typical command needs about 1 minute; complex act commands may need even longer.
4. Always report task results before finishing. After completing the automation task, you MUST proactively summarize the results to the user — including key data found, actions completed, screenshots taken, and any relevant findings. Never silently end after the last automation step; the user expects a complete response in a single interaction.

Automate web browsing using npx @midscene/web@1. Launches a headless Chrome via Puppeteer that persists across CLI calls — no session loss between commands. Each CLI command maps directly to an MCP tool — you (the AI agent) act as the brain, deciding which actions to take based on screenshots.

When to Use

Use this skill when:

• The user wants to browse or navigate to a specific URL
• You need to scrape, extract, or collect data from websites
• You want to verify or test frontend UI behavior
• The user wants screenshots of web pages

If you need to preserve login sessions or work with the user's existing browser tabs, use the Chrome Bridge Automation skill instead.

Prerequisites

Midscene requires models with strong visual grounding capabilities. The following environment variables must be configured — either as system environment variables or in a .env file in the current working directory (Midscene loads .env automatically):

MIDSCENE_MODEL_API_KEY="your-api-key"
MIDSCENE_MODEL_NAME="model-name"
MIDSCENE_MODEL_BASE_URL="https://..."
MIDSCENE_MODEL_FAMILY="family-identifier"

Example: Gemini (Gemini-3-Flash)

MIDSCENE_MODEL_API_KEY="your-google-api-key"
MIDSCENE_MODEL_NAME="gemini-3-flash"
MIDSCENE_MODEL_BASE_URL="https://generativelanguage.googleapis.com/v1beta/openai/"
MIDSCENE_MODEL_FAMILY="gemini"

Example: Qwen 3.5

MIDSCENE_MODEL_API_KEY="your-aliyun-api-key"
MIDSCENE_MODEL_NAME="qwen3.5-plus"
MIDSCENE_MODEL_BASE_URL="https://dashscope.aliyuncs.com/compatible-mode/v1"
MIDSCENE_MODEL_FAMILY="qwen3.5"
MIDSCENE_MODEL_REASONING_ENABLED="false"
# If using OpenRouter, set:
# MIDSCENE_MODEL_API_KEY="your-openrouter-api-key"
# MIDSCENE_MODEL_NAME="qwen/qwen3.5-plus"
# MIDSCENE_MODEL_BASE_URL="https://openrouter.ai/api/v1"

Example: Doubao Seed 2.0 Lite

MIDSCENE_MODEL_API_KEY="your-doubao-api-key"
MIDSCENE_MODEL_NAME="doubao-seed-2-0-lite"
MIDSCENE_MODEL_BASE_URL="https://ark.cn-beijing.volces.com/api/v3"
MIDSCENE_MODEL_FAMILY="doubao-seed"

Commonly used models: Doubao Seed 2.0 Lite, Qwen 3.5, Zhipu GLM-4.6V, Gemini-3-Pro, Gemini-3-Flash.

If the model is not configured, ask the user to set it up. See Model Configuration for supported providers.

Commands

Connect to a Web Page

npx @midscene/web@1 connect --url https://example.com

Take Screenshot

npx @midscene/web@1 take_screenshot

After taking a screenshot, read the saved image file to understand the current page state before deciding the next action.

Perform Action

Use act to interact with the page and get the result. It autonomously handles all UI interactions internally — clicking, typing, scrolling, hovering, waiting, and navigating — so you should give it complex, high-level tasks as a whole rather than breaking them into small steps. Describe what you want to do and the desired effect in natural language:

# specific instructions
npx @midscene/web@1 act --prompt "click the Login button and fill in the email field with 'user@example.com'"
npx @midscene/web@1 act --prompt "scroll down and click the Submit button"

# or target-driven instructions
npx @midscene/web@1 act --prompt "click the country dropdown and select Japan"

Disconnect

Disconnect from the page but keep the browser running:

npx @midscene/web@1 disconnect

Close Browser

Close the browser completely when finished:

npx @midscene/web@1 close

Workflow Pattern

The browser persists across CLI calls via a background Chrome process. Follow this pattern:

1. Connect to a URL to open a new tab
2. Take screenshot to see the current state, make sure the page is loaded.
3. Execute action using act to perform the desired action or target-driven instructions.
4. Close the browser when done (or disconnect to keep it for later)
5. Report results — summarize what was accomplished, present key findings and data extracted during the task, and list any generated files (screenshots, logs, etc.) with their paths

Best Practices

1. Always connect first: Navigate to the target URL with connect --url before any interaction.
2. Be specific about UI elements: Instead of "the button", say "the blue Submit button in the contact form".
3. Use natural language: Describe what you see on the page, not CSS selectors. Say "the red Buy Now button" instead of "#buy-btn".
4. Handle loading states: After navigation or actions that trigger page loads, take a screenshot to verify the page has loaded.
5. Close when done: Use close to shut down the browser and free resources.
6. Never run in background: Every midscene command must run synchronously — background execution breaks the screenshot-analyze-act loop.
7. Batch related operations into a single act command: When performing consecutive operations within the same page, combine them into one act prompt instead of splitting them into separate commands. For example, "fill in the email and password fields, then click the Login button" should be a single act call, not three. This reduces round-trips, avoids unnecessary screenshot-analyze cycles, and is significantly faster.
8. Always report results after completion: After finishing the automation task, you MUST proactively present the results to the user without waiting for them to ask. This includes: (1) the answer to the user's original question or the outcome of the requested task, (2) key data extracted or observed during execution, (3) screenshots and other generated files with their paths, (4) a brief summary of steps taken. Do NOT silently finish after the last automation command — the user expects complete results in a single interaction.

Example — Dropdown selection:

npx @midscene/web@1 act --prompt "click the country dropdown and select Japan"
npx @midscene/web@1 take_screenshot

Example — Form interaction:

npx @midscene/web@1 act --prompt "fill in the email field with 'user@example.com' and the password field with 'pass123', then click the Log In button"
npx @midscene/web@1 take_screenshot

Troubleshooting

Connection Failures

• Ensure Chrome/Chromium is installed on the system (Puppeteer downloads its own by default).
• Check that no firewall blocks local Chrome debugging ports.

API Key Errors

• Check .env file contains MIDSCENE_MODEL_API_KEY=<your-key>.
• Verify the key is valid for the configured model provider.

Timeouts

• Web pages may take time to load. After connecting, take a screenshot to verify readiness before interacting.
• For slow pages, wait briefly between steps.

Screenshots Not Displaying

• The screenshot path is an absolute path to a local file. Use the Read tool to view it.