Show HN: Glass – a see/act/debug loop over any GUI app for agents (MCP)

Give your coding agent hands for the app it's building — launch it, drive it, and verify the result, without burning a screenshot on every step.

A Rust MCP server that gives an AI coding agent a closed build → see → interact → debug loop over external native GUI applications.

glass lets an agent launch a GUI app, capture what is on screen, inject mouse and keyboard input, read the app's logs, and detect visual changes — so a coding agent can build and debug UI applications independently instead of asking the user "does this look right?".

glass drives apps as an external black box, so it works with any native GUI app regardless of toolkit or language. It has two Linux backends (X11 and Wayland), a Windows backend, an Android backend (an AVD emulator, driven over adb

from any host), an iOS backend (native apps in the Simulator over xcrun simctl

, with input and the accessibility tree via idb_companion

; multi-touch gestures excepted), and a macOS backend, behind a platform-agnostic core.

An agent building a GUI app runs it under glass, reproduces a bug from the accessibility tree (no screenshots), fixes the code, and re-verifies — the loop it otherwise can't close on its own. Try it yourself.

Download glass for your platform from the

Releases pageandconnect it to your agent. - Get the example app — clone this repo, or download

(on Linux it needsexamples/tasks_demo.py

sudo apt install python3-gi gir1.2-gtk-4.0

). - Paste this to your agent:

Use glass to run

examples/tasks_demo.py

with accessibility on. There's a bug: clickingAdd doesn't add the typed task. Reproduce it by driving the UI and checking the accessibility tree (don't just screenshot), then find and fix the bug in the code and verify a task actually appears.

Your agent launches the app, reproduces the bug from the accessibility tree, fixes the one-line wiring bug, and confirms the task appears — the whole build → see → interact → debug loop, start to finish. (glass-mcp doctor

checks your environment if anything's off.)

Point an agent at a GUI app and it runs the whole cycle itself. When the app exposes an accessibility tree, the agent drives it semantically — addressing widgets by #id

and confirming each step from text, no per-step screenshot:

glass_start            { "run": ["python3", "app.py"], "a11y": true }   // launch (+ private a11y bus)
glass_a11y_snapshot                        // the tree: role, name, #id, bounds — as text
glass_click_element    { "id": 5 }         // click by #id, not pixels
glass_wait_for_element { "name": "Save", "condition": "enabled" }       // wait on state — no polling
glass_set_value        { "id": 4, "value": "hello" }   // set a field / toggle / dropdown
glass_logs                                 // read the app's stderr

For a canvas or custom-rendered app with no accessibility tree, drive it by pixels instead — glass_screenshot

, glass_click {x,y}

, and glass_diff

, which returns changed_pct

• a bbox

as text, so routine checks between screenshots cost no vision tokens. Why the loop is shaped this way: the build → see → interact → debug loop.

Download the latest build for your platform from the Releases page, then set up your host:

Linux—docs/how-to/setup-linux.md(X11 or Wayland;Xvfb

/sway

• bubblewrap)Windows—docs/how-to/setup-windows.md(a prebuilt.exe

• Sandboxie)macOS—docs/how-to/setup-macos.md(install the notarized.dmg

; no build needed)Android—docs/how-to/setup-android.md(an AVD emulator, from any host)iOS—docs/how-to/setup-ios.md(the Simulator, macOS host only)

Every asset is listed in docs/reference/platforms.md. Prefer to compile, or on an architecture with no published asset? See docs/how-to/build-from-source.md — it is a single cargo build

.

Then connect glass to your agent and run glass-mcp doctor

to check the environment. New here? Follow the tutorial for a guaranteed first success.

glass needs no app integration and no skill to run, but an agent drives it far more reliably with the open glass-drive Agent Skill — it stops the agent spending its first turns rediscovering the verify-cheaply-then-look loop. Installing it is the single highest-leverage thing you can add when pointing an agent at glass.

✓ supported · ◑ partial · – not supported · 🚧 planned.

Full matrix, per-capability detail, and system requirements: docs/reference/platforms.md. Transport is MCP over stdio (default) or network HTTP.

The full docs — tutorial, how-to guides, reference, and explanations — are under . See

docs/

for release notes, and

CHANGELOG.md

Stability and versioningfor what a 1.0 release guarantees.

glass is open core, licensed Apache-2.0 — see LICENSE-APACHE.