Web Infra Dev Midscene Skills Harmonyos Device Automation

HarmonyOS Device 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.

Automate HarmonyOS NEXT devices using npx -y @midscene/harmony@1. 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.

What act Can Do

Inside a single act call on HarmonyOS, Midscene can tap, double-tap, long-press, type, clear text, scroll, drag items, press keys, and use system navigation such as Back, Home, or recent apps while working from the current visible screen. Two-finger zoom is not available because the underlying HarmonyOS automation layer does not expose multi-touch input.

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.

HDC Setup

HDC (HarmonyOS Device Connector) must be installed and accessible. Common setup:

• Install via DevEco Studio
• Or set HDC_HOME environment variable to point to the HDC directory

Verify HDC is working:

hdc version
hdc list targets

Commands

Connect to Device

npx -y @midscene/harmony@1 connect
npx -y @midscene/harmony@1 connect --deviceId 0123456789ABCDEF

Launch an App or URL

Use the dedicated launch step when you want a deterministic starting point before the rest of the task:

npx -y @midscene/harmony@1 launch --uri com.huawei.hmos.settings
npx -y @midscene/harmony@1 launch --uri com.huawei.hmos.camera
npx -y @midscene/harmony@1 launch --uri https://www.example.com

Run a Raw HarmonyOS Shell Command

Use this when the task needs lower-level device control that is not best expressed as a visible UI interaction:

npx -y @midscene/harmony@1 runhdcshell --command "hidumper -s RenderService -a screen"

This is forwarded to hdc shell on the connected device. In practice, the underlying command is hdc -t <deviceId> shell hidumper -s RenderService -a screen.

Take Screenshot

npx -y @midscene/harmony@1 take_screenshot

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

Perform Action

Use act to interact with the device and get the result. It autonomously handles all UI interactions internally — tapping, typing, scrolling, swiping, 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 -y @midscene/harmony@1 act --prompt "type hello world in the search field and press Enter"
npx -y @midscene/harmony@1 act --prompt "long press the message bubble and tap Delete in the popup menu"

# or target-driven instructions
npx -y @midscene/harmony@1 act --prompt "open Settings and navigate to Wi-Fi settings, tell me the connected network name"

Assert Current Screen State

Use assert to verify that the current screen satisfies a natural language condition. It does not perform UI actions; it checks the visible screen state and passes only when the assertion is true. Use this for validation, QA checks, and final state verification after act.

npx -y @midscene/harmony@1 assert --prompt "there is a login button visible"
npx -y @midscene/harmony@1 assert --prompt "the settings screen shows Wi-Fi and Bluetooth options"
npx -y @midscene/harmony@1 assert --deviceId 0123456789ABCDEF --prompt "the app shows a successful login message"

Use a Reference Image for Precise Targeting

When the user provides a screenshot, icon, logo, or reference image and wants an exact visual match, prefer tap --locate instead of a generic act --prompt. Pass --locate as JSON. The prompt describes the target, images supplies named reference images, and convertHttpImage2Base64: true is useful when the image URL may not be directly accessible to the model.

npx -y @midscene/harmony@1 tap --locate '{
  "prompt": "tap the area contains the image",
  "images": [
    {
      "name": "target image",
      "url": "https://github.githubassets.com/assets/GitHub-Mark-ea2971cee799.png"
    }
  ],
  "convertHttpImage2Base64": true
}'

The same locate JSON shape also works for other commands that accept a locate parameter.

Disconnect

npx -y @midscene/harmony@1 disconnect

Consume Report Files

The generated HTML report is recommended for human reading first. It includes step-by-step execution details and replay videos for each operation, which makes it much easier to understand what happened and troubleshoot problems.

If another skill or tool needs to consume the report, first convert it with report-tool from the same platform CLI package. Prefer Markdown for LLM-based workflows. Use JSON when the report needs to be processed programmatically.

npx -y @midscene/harmony@1 report-tool --action to-markdown --htmlPath ./midscene_run/report/.../index.html --outputDir ./output-markdown
npx -y @midscene/harmony@1 report-tool --action split --htmlPath ./midscene_run/report/.../index.html --outputDir ./output-data

Workflow Pattern

Since CLI commands are stateless between invocations, follow this pattern:

1. Connect to establish a session
2. Launch the target app and take screenshot to see the current state, make sure the app is launched and visible on the screen.
3. Execute action using act to perform the desired action or target-driven instructions, and use assert when you need to verify the resulting screen state.
4. Disconnect when done

Best Practices

1. Bring the target app to the foreground before using this skill: For best efficiency, launch the app using HDC (e.g., hdc shell aa start -a EntryAbility -b <bundleName>) before invoking any midscene commands. Then take a screenshot to confirm the app is actually in the foreground. Only after visual confirmation should you proceed with UI automation using this skill. HDC commands are significantly faster than using midscene to navigate to and open apps.
2. Be specific about UI elements: Instead of vague descriptions, provide clear, specific details. Say "the Wi-Fi toggle switch on the right side" instead of "the toggle".
3. Describe locations when possible: Help target elements by describing their position (e.g., "the search icon at the top right", "the third item in the list").
4. Never run in background: Every midscene command must run synchronously — background execution breaks the screenshot-analyze-act loop.
5. Batch related operations into a single act command: When performing consecutive operations within the same app, combine them into one act prompt instead of splitting them into separate commands. For example, "open Settings, tap Wi-Fi, and toggle it on" should be a single act call, not three. This reduces round-trips, avoids unnecessary screenshot-analyze cycles, and is significantly faster.
6. Use assert for verification: When the goal is to confirm that a screen state is true, use assert --prompt "..." instead of an act prompt. Keep assertions observable and specific, such as "the permission dialog is visible" or "the Save button is disabled".
7. Summarize report files after completion: After finishing the automation task, collect and summarize all report files (screenshots, logs, output files, etc.) for the user. Present a clear summary of what was accomplished, what files were generated, and where they are located, making it easy for the user to review the results.
8. Prefer tap --locate when a reference image is provided: If the user shares a screenshot, icon, or logo and wants that exact visual target, use tap --locate with a multimodal locate JSON object such as { "prompt": "...", "images": [...] } instead of relying only on act --prompt.

Example — App launch and interaction:

hdc shell aa start -a EntryAbility -b com.huawei.hmos.settings
npx -y @midscene/harmony@1 connect
npx -y @midscene/harmony@1 take_screenshot
npx -y @midscene/harmony@1 act --prompt "scroll down the settings list and tap About device"
npx -y @midscene/harmony@1 take_screenshot
npx -y @midscene/harmony@1 disconnect

Example — Form interaction:

npx -y @midscene/harmony@1 act --prompt "fill in the username field with 'testuser' and the password field with 'pass123', then tap the Login button"
npx -y @midscene/harmony@1 take_screenshot

Common HarmonyOS Bundle Names

Troubleshooting

Source: web-infra-dev/midscene-skills — distributed by TomeVault.