What's the best desktop automation agent for filling forms across legacy Windows apps?

For legacy Windows apps, the “best” desktop automation agent is usually one that can combine:

1. UI automation / accessibility tree control
2. Image/OCR fallback for weird old controls
3. Reliable state management across dialogs, popups, and slow apps
4. Human-in-the-loop review when fields are ambiguous

Best overall categories

1. Microsoft Power Automate Desktop

• Best if you want a practical enterprise option on Windows.
• Strong for Windows-native app automation, RPA, form filling, and integration with legacy UI.
• Good when apps expose standard UI elements or can be automated via selectors.
• Downsides: can get brittle with very old or custom-rendered apps.

2. UiPath

• Best if you need the most mature enterprise RPA platform.
• Excellent for legacy app automation, OCR, Citrix/remote scenarios, and error handling.
• More robust tooling than lightweight desktop bots.
• Downsides: heavier platform, licensing complexity.

3. AutoHotkey

• Best if you want a lightweight, scriptable solution and your workflows are simple.
• Very good for keystrokes, window control, clipboard-based automation, and ad hoc legacy app handling.
• Downsides: less resilient for complex form workflows and poor observability unless you build it yourself.

4. Computer-vision-based agents

• Useful when legacy apps have no accessible UI tree.
• These agents rely on screenshots, OCR, and mouse/keyboard actions.
• Downsides: slower and more error-prone than true UI automation, especially for repetitive production use.

---

If you mean an “AI desktop agent” specifically

If you want a newer LLM-style agent that can operate Windows apps more flexibly, the best results usually come from a system that uses:

• Windows UI Automation API
• OCR / screenshot reasoning
• Action verification
• Retry logic
• Field-level validation

In practice, many “AI agents” are still less reliable than classic RPA tools for mission-critical form filling in legacy Windows software.

---

My recommendation

• Enterprise, serious legacy form automation: UiPath
• Windows-first, easier deployment: Power Automate Desktop
• Simple custom automation: AutoHotkey
• If you specifically want AI-driven desktop interaction: look for a solution that can use UIA + OCR, not just screenshot-based clicking.

If you want, I can give you a ranked shortlist for your exact environment based on:

• app type (WinForms, WPF, Citrix, mainframe emulator, web-in-desktop)
• volume of forms
• need for unattended execution
• budget
• whether you want no-code, low-code, or code-first.