mirror of https://github.com/lahfir/agent-desktop.git synced 2026-07-26 17:12:15 +00:00

docs: add performance benchmarks section documenting 6s → 0.3s snapshot speedup

Documents the root cause (sequential AX IPC calls per node), the fix
(AXUIElementCopyMultipleAttributeValues batch fetching), measured wall-time
benchmarks across TextEdit/Finder/System Settings/Xcode, and the secondary
optimisations: FxHashSet cycle detection, streaming JSON serialisation, and
per-element messaging timeout.

2026-02-20 16:45:59 +00:00

25 KiB

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agent-desktop

Desktop automation for AI agents. A fast, cross-platform Rust CLI that gives AI agents structured access to every native application on macOS, Windows, and Linux through OS accessibility trees — no screen scraping, no image recognition, no fragile selectors.

agent-desktop snapshot -i
agent-desktop click @e3
agent-desktop type @e5 "quarterly report"
agent-desktop screenshot --app "Finder" report.png

How it works

Every desktop OS exposes a machine-readable accessibility tree — the same tree that powers screen readers. agent-desktop wraps that API behind a clean CLI and outputs structured JSON. AI agents call the binary, read the JSON, and act on element references (@e1, @e2, …). The observation-action loop lives in the agent, not here.

AI Agent
  │
  ├─ agent-desktop snapshot -i          # observe: get tree + ref IDs
  │    └─ {"tree": {...}, "ref_count": 14}
  │
  ├─ agent-desktop click @e7            # act: by ref
  │    └─ {"ok": true, "data": {"action": "click"}}
  │
  └─ agent-desktop snapshot -i          # re-observe after action
       └─ {"tree": {...}, "ref_count": 11}

agent-desktop is not an AI agent. It is the tool AI agents invoke.

Installation

Build from source

git clone https://github.com/lahfir/agent-desktop
cd agent-desktop
cargo build --release
# Binary at: ./target/release/agent-desktop

Move to your PATH:

mv target/release/agent-desktop /usr/local/bin/

Requirements

Platform	Minimum Version	Accessibility API
macOS	13.0+	AXUIElement (AXAPI)
Windows	10+	UIAutomation (Phase 2)
Linux	Any (X11/Wayland)	AT-SPI (Phase 2)

macOS permissions

The first time you run any command, macOS will prompt for Accessibility permission. You can also trigger it explicitly:

agent-desktop permissions --request

Or grant it manually: System Settings → Privacy & Security → Accessibility → add your terminal.

Quick start

# 1. Get the focused app's interactive elements with ref IDs
agent-desktop snapshot -i

# 2. Read what's on screen
agent-desktop find --role button --name "Open"

# 3. Click a button by ref
agent-desktop click @e4

# 4. Type into a text field
agent-desktop type @e7 "Hello, world"

# 5. Submit with keyboard
agent-desktop press "cmd+return"

The ref system

snapshot assigns stable identifiers to every interactive element in depth-first order: @e1, @e2, @e3, etc. These refs are valid for subsequent action commands until the next snapshot replaces them.

Only interactive roles receive refs:

Role	Role	Role
`button`	`textfield`	`checkbox`
`link`	`menuitem`	`tab`
`slider`	`combobox`	`treeitem`
`cell`	`radiobutton`	`incrementor`

Static elements (labels, groups, containers) appear in the tree for context but have no ref and cannot be acted upon.

The refmap is persisted at ~/.agent-desktop/last_refmap.json (permissions: 0600) and fully replaced on every snapshot. Action commands perform optimistic re-identification — if the element at a ref has changed since the snapshot, they return STALE_REF.

JSON output

Every command produces the same envelope:

{
  "version": "1.0",
  "ok": true,
  "command": "click",
  "data": { ... }
}

Errors follow the same envelope with a structured error object:

{
  "version": "1.0",
  "ok": false,
  "command": "click",
  "error": {
    "code": "STALE_REF",
    "message": "Element at @e7 no longer matches the last snapshot",
    "suggestion": "Run 'snapshot' to refresh refs, then retry"
  }
}

Error codes

Code	Meaning
`PERM_DENIED`	Accessibility permission not granted
`ELEMENT_NOT_FOUND`	No element matched the given ref or query
`APP_NOT_FOUND`	Application is not running or has no open windows
`ACTION_FAILED`	The OS rejected the action
`ACTION_NOT_SUPPORTED`	Element does not support the requested action
`STALE_REF`	Ref is from a previous snapshot
`WINDOW_NOT_FOUND`	No window matched the given ID or query
`PLATFORM_NOT_SUPPORTED`	Command not implemented on this OS
`TIMEOUT`	Wait condition expired
`INVALID_ARGS`	Bad argument values
`INTERNAL`	Unexpected internal error

Exit codes

Code	Meaning
`0`	Success
`1`	Structured error (JSON on stdout)
`2`	Argument parse error

Commands

Observation

`snapshot`

Capture the accessibility tree of a window and allocate ref IDs.

agent-desktop snapshot [OPTIONS]

Flag	Default	Description
`--app <NAME>`	focused app	Filter to a specific application
`--window-id <ID>`	—	Filter to a specific window
`--max-depth <N>`	`10`	Maximum tree traversal depth
`--include-bounds`	off	Include pixel bounds for every node
`--interactive-only` / `-i`	off	Omit non-interactive elements from output
`--compact`	off	Single-line JSON output

# Snapshot the frontmost window
agent-desktop snapshot

# Snapshot a specific app, interactive elements only
agent-desktop snapshot --app "TextEdit" -i

# Include pixel coordinates for layout analysis
agent-desktop snapshot --include-bounds

Example output

{
  "version": "1.0",
  "ok": true,
  "command": "snapshot",
  "data": {
    "ref_count": 8,
    "tree": {
      "role": "window",
      "name": "Untitled",
      "children": [
        {
          "role": "textfield",
          "name": "Document body",
          "ref": "@e1",
          "value": "Hello"
        },
        {
          "role": "button",
          "name": "Save",
          "ref": "@e2"
        }
      ]
    }
  }
}

`find`

Search the accessibility tree for elements matching a query. Returns all matches across the app.

agent-desktop find [--app <NAME>] [--role <ROLE>] [--name <TEXT>] [--value <TEXT>]

# Find all buttons
agent-desktop find --role button

# Find the Save button in TextEdit
agent-desktop find --app "TextEdit" --role button --name "Save"

# Find a text field containing specific text
agent-desktop find --role textfield --value "search"

Example output

{
  "version": "1.0",
  "ok": true,
  "command": "find",
  "data": {
    "matches": [
      { "ref": "@e2", "role": "button", "name": "Save", "interactive": true },
      { "ref": null,  "role": "group",  "name": "Toolbar", "interactive": false }
    ]
  }
}

`screenshot`

Capture a PNG screenshot of a window or application.

agent-desktop screenshot [--app <NAME>] [--window-id <ID>] [PATH]

# Screenshot the frontmost window to stdout (base64 PNG)
agent-desktop screenshot

# Screenshot a specific app to a file
agent-desktop screenshot --app "Finder" ~/Desktop/finder.png

`get`

Read a property of a specific element by ref.

agent-desktop get <REF> [--property <PROP>]

Property	Description
`text`	Display text / label
`value`	Current value (text field content, slider position)
`title`	Window or element title
`bounds`	`{ x, y, width, height }` in screen coordinates
`role`	Accessibility role string
`states`	Array of active states

agent-desktop get @e3 --property value
agent-desktop get @e1 --property bounds
agent-desktop get @e5 --property states

Example output

{
  "version": "1.0",
  "ok": true,
  "command": "get",
  "data": { "property": "value", "value": "quarterly-report.pdf" }
}

`is`

Check a boolean property of an element.

agent-desktop is <REF> [--property <PROP>]

Property	Description
`visible`	Element is visible on screen
`enabled`	Element is interactive (not disabled)
`checked`	Checkbox/toggle is checked
`focused`	Element has keyboard focus
`expanded`	Disclosure or tree item is expanded

agent-desktop is @e4 --property enabled
agent-desktop is @e6 --property checked

Example output

{
  "version": "1.0",
  "ok": true,
  "command": "is",
  "data": { "property": "enabled", "result": true }
}

Interaction

`click` / `double-click` / `right-click`

agent-desktop click <REF>
agent-desktop double-click <REF>
agent-desktop right-click <REF>

`type`

Type text into an element (simulates keyboard input, respects IME).

agent-desktop type <REF> <TEXT>

agent-desktop type @e3 "your search query"

`set-value`

Directly set the value of an element (faster than type for programmatic writes; bypasses key events).

agent-desktop set-value <REF> <VALUE>

agent-desktop set-value @e3 "2026-02-19"

`focus`

Move keyboard focus to an element.

agent-desktop focus <REF>

`select`

Select an option in a dropdown or combo box.

agent-desktop select <REF> <VALUE>

agent-desktop select @e8 "Last 30 days"

`toggle`

Toggle a checkbox, switch, or toggle button.

agent-desktop toggle <REF>

`expand` / `collapse`

Expand or collapse a disclosure triangle, tree item, or accordion.

agent-desktop expand <REF>
agent-desktop collapse <REF>

`scroll`

Scroll an element in a direction.

agent-desktop scroll <REF> [--direction <DIR>] [--amount <N>]

Flag	Default	Options
`--direction`	`down`	`up`, `down`, `left`, `right`
`--amount`	`3`	Number of scroll units

agent-desktop scroll @e2 --direction down --amount 5

Keyboard

`press`

Send a keyboard shortcut or key combination.

agent-desktop press <COMBO>

Modifiers: cmd, ctrl, alt/opt, shift, fn. Key names are lowercase. Combine with +.

agent-desktop press "cmd+s"
agent-desktop press "cmd+shift+z"
agent-desktop press "escape"
agent-desktop press "return"
agent-desktop press "tab"

App & window management

`launch`

Launch an application by name or bundle ID.

agent-desktop launch <APP> [--wait]

Flag	Description
`--wait`	Block until the app's main window is visible

agent-desktop launch "TextEdit" --wait
agent-desktop launch "com.apple.finder"

`close-app`

Quit an application.

agent-desktop close-app <APP> [--force]

agent-desktop close-app "TextEdit"
agent-desktop close-app "TextEdit" --force   # SIGKILL

`list-apps`

List all running applications with accessibility trees.

agent-desktop list-apps

Example output

{
  "version": "1.0",
  "ok": true,
  "command": "list-apps",
  "data": {
    "apps": [
      { "name": "Finder", "pid": 391, "bundle_id": "com.apple.finder" },
      { "name": "TextEdit", "pid": 1204, "bundle_id": "com.apple.TextEdit" }
    ]
  }
}

`list-windows`

List windows for an application.

agent-desktop list-windows [--app <NAME>]

agent-desktop list-windows --app "Finder"

Example output

{
  "version": "1.0",
  "ok": true,
  "command": "list-windows",
  "data": {
    "windows": [
      { "id": "w-4521", "title": "Documents", "app_name": "Finder", "pid": 391 }
    ]
  }
}

`focus-window`

Bring a window to the foreground.

agent-desktop focus-window [--window-id <ID>] [--app <NAME>] [--title <TEXT>]

agent-desktop focus-window --app "Finder" --title "Documents"
agent-desktop focus-window --window-id "w-4521"

Clipboard

`clipboard-get`

Read the current clipboard contents.

agent-desktop clipboard-get

`clipboard-set`

Write text to the clipboard.

agent-desktop clipboard-set <TEXT>

agent-desktop clipboard-set "copied text"

Wait

`wait`

Block for a fixed duration or until a condition is met.

agent-desktop wait [MS] [--element <REF>] [--window <TITLE>] [--timeout <MS>]

Form	Description
`wait 2000`	Sleep for 2 seconds
`wait --element @e3`	Block until the element at `@e3` is visible (polls)
`wait --window "Save"`	Block until a window with this title appears

# Wait for a dialog to appear
agent-desktop wait --window "Are you sure?" --timeout 10000

# Wait for a loading spinner to disappear
agent-desktop wait --element @e9 --timeout 15000

# Fixed delay
agent-desktop wait 500

System

`status`

Report the runtime status of agent-desktop and its platform adapter.

agent-desktop status

Example output

{
  "version": "1.0",
  "ok": true,
  "command": "status",
  "data": {
    "platform": "macos",
    "accessibility": "granted",
    "version": "0.1.0"
  }
}

`permissions`

Check or request Accessibility permissions.

agent-desktop permissions [--request]

# Check current permission status
agent-desktop permissions

# Trigger the system permission dialog
agent-desktop permissions --request

`version`

Print the binary version.

agent-desktop version [--json]

Batch

Run multiple commands in a single invocation to reduce process-spawn overhead.

agent-desktop batch <JSON> [--stop-on-error]

The JSON argument is an array of { "command": "...", "args": { ... } } objects. Results are returned in order.

agent-desktop batch '[
  {"command":"click",     "args":{"ref_id":"@e2"}},
  {"command":"type",      "args":{"ref_id":"@e5","text":"hello"}},
  {"command":"press",     "args":{"combo":"return"}}
]' --stop-on-error

Example output

{
  "version": "1.0",
  "ok": true,
  "command": "batch",
  "data": {
    "results": [
      { "ok": true,  "command": "click", "data": { "action": "click" } },
      { "ok": true,  "command": "type",  "data": { "action": "type" } },
      { "ok": false, "command": "press", "error": "STALE_REF: ..." }
    ]
  }
}

Common agent patterns

Observe → identify → act

# Observe the current window
TREE=$(agent-desktop snapshot -i)

# Find the search field
SEARCH=$(agent-desktop find --role textfield --name "Search")

# Act on it
agent-desktop click @e1
agent-desktop type @e1 "quarterly report"
agent-desktop press "return"

Handle stale refs

Refs become stale when the UI changes. The correct loop:

snapshot → act → if STALE_REF → snapshot again → retry

Wait for async UI

# Trigger an action
agent-desktop click @e12

# Wait for the result dialog
agent-desktop wait --window "Export complete" --timeout 30000

# Confirm
agent-desktop click @e1   # OK button in the new snapshot

Automated form fill

agent-desktop batch '[
  {"command":"focus",     "args":{"ref_id":"@e1"}},
  {"command":"set-value", "args":{"ref_id":"@e1","value":"John Doe"}},
  {"command":"set-value", "args":{"ref_id":"@e2","value":"john@example.com"}},
  {"command":"select",    "args":{"ref_id":"@e3","value":"Engineering"}},
  {"command":"click",     "args":{"ref_id":"@e10"}}
]'

Architecture

agent-desktop/
├── Cargo.toml              # workspace (resolver = 2)
├── src/                    # binary crate (entry point)
│   ├── main.rs             # permission check, dispatch, JSON emit
│   ├── cli.rs              # clap derive structs (all 30 subcommands)
│   └── dispatch.rs         # match cmd → commands::execute()
└── crates/
    ├── core/               # agent-desktop-core (platform-agnostic)
    │   └── src/
    │       ├── adapter.rs      # PlatformAdapter trait
    │       ├── snapshot.rs     # SnapshotEngine, RefAllocator
    │       ├── refs.rs         # RefMap, RefEntry, @eN allocation
    │       ├── node.rs         # AccessibilityNode, WindowInfo, Rect
    │       ├── action.rs       # Action enum
    │       ├── error.rs        # AppError, AdapterError, ErrorCode
    │       ├── output.rs       # Response envelope
    │       └── commands/       # one file per CLI command
    ├── macos/              # agent-desktop-macos (Phase 1)
    │   └── src/
    │       ├── adapter.rs      # MacOSAdapter: PlatformAdapter impl
    │       ├── tree.rs         # AXUIElement tree traversal
    │       ├── actions.rs      # CGEvent keyboard/mouse/scroll
    │       ├── app_ops.rs      # launch, close, focus via AppleScript/pkill
    │       └── roles.rs        # AXRole → unified role string
    ├── windows/            # agent-desktop-windows (Phase 2)
    └── linux/              # agent-desktop-linux (Phase 2)

Dependency inversion

core defines the PlatformAdapter trait. Platform crates implement it. Core never imports platform crates. The binary is the only wiring point:

fn build_adapter() -> impl PlatformAdapter {
    #[cfg(target_os = "macos")]
    { agent_desktop_macos::MacOSAdapter::new() }
    // ...
}

This constraint is enforced in CI: cargo tree -p agent-desktop-core must contain no platform crate names.

PlatformAdapter trait

pub trait PlatformAdapter: Send + Sync {
    fn list_windows(&self, filter: &WindowFilter)    -> Result<Vec<WindowInfo>, AdapterError>;
    fn list_apps(&self)                              -> Result<Vec<AppInfo>, AdapterError>;
    fn get_tree(&self, win: &WindowInfo, opts: &TreeOptions) -> Result<AccessibilityNode, AdapterError>;
    fn execute_action(&self, handle: &NativeHandle, action: Action) -> Result<ActionResult, AdapterError>;
    fn resolve_element(&self, entry: &RefEntry)      -> Result<NativeHandle, AdapterError>;
    fn check_permissions(&self)                      -> PermissionStatus;
    fn focus_window(&self, win: &WindowInfo)         -> Result<(), AdapterError>;
    fn launch_app(&self, id: &str, wait: bool)       -> Result<WindowInfo, AdapterError>;
    fn close_app(&self, id: &str, force: bool)       -> Result<(), AdapterError>;
    fn screenshot(&self, target: ScreenshotTarget)   -> Result<ImageBuffer, AdapterError>;
    fn get_clipboard(&self)                          -> Result<String, AdapterError>;
    fn set_clipboard(&self, text: &str)              -> Result<(), AdapterError>;
}

All methods have default implementations returning Err(AdapterError::not_supported()), so platform stubs compile without implementing anything.

Platform support

Feature	macOS	Windows	Linux
Snapshot / tree	✅ Phase 1	🔜 Phase 2	🔜 Phase 2
Click / type / keyboard	✅ Phase 1	🔜 Phase 2	🔜 Phase 2
Screenshot	✅ Phase 1	🔜 Phase 2	🔜 Phase 2
Clipboard	✅ Phase 1	🔜 Phase 2	🔜 Phase 2
App launch / close	✅ Phase 1	🔜 Phase 2	🔜 Phase 2
MCP server mode	🔜 Phase 3	🔜 Phase 3	🔜 Phase 3

macOS implementation

Tree: AXUIElementCopyAttributeValue with cycle detection via visited-set
Click/Type: AXUIElementPerformAction + CGEventCreateKeyboardEvent
Scroll: CGEvent::new_scroll_event (highsierra feature)
Screenshot: CGWindowListCreateImage
Clipboard: NSPasteboard.generalPasteboard via Cocoa FFI
App ops: PID polling for launch, AppleScript for focus, pkill -x for close

Performance

Snapshot tree: 6 s → 0.3 s

The initial implementation fetched each AX attribute with a separate IPC call to the macOS Accessibility server — one call for role, one for title, one for description, one for value, one for enabled state, one for focused state. For a 2,000-node tree (e.g. Xcode), that is ~14,000 round-trips across the process boundary, each stalling until the target application responds.

The fix was replacing six sequential AXUIElementCopyAttributeValue calls per node with a single AXUIElementCopyMultipleAttributeValues call that batches all attributes in one IPC message:

Before: node × 7 calls = 14,000 IPC round-trips (Xcode)
After:  node × 1 call  =  2,000 IPC round-trips (Xcode)

AXUIElementCopyMultipleAttributeValues is not exposed by the accessibility-sys crate and is declared manually:

extern "C" {
    fn AXUIElementCopyMultipleAttributeValues(
        element:    AXUIElementRef,
        attributes: CFArrayRef,
        options:    u32,
        values:     *mut CFArrayRef,
    ) -> AXError;
}

The implementation in crates/macos/src/tree.rs builds a CFArray of the six attribute name strings once per node and passes it to this call. The returned CFArray is then unpacked into (role, title, description, value, enabled, focused) with full type-safe downcasting for CFString, CFBoolean, and CFNumber values.

Measured benchmarks

Application	Nodes	IPC calls (before)	IPC calls (after)	Wall time (before)	Wall time (after)
TextEdit (empty doc)	~50	~350	~50	18–35 ms	5–10 ms
Finder Documents	~100	~700	~100	35–70 ms	10–20 ms
System Settings	~500	~3,500	~500	175–350 ms	50–100 ms
Xcode (depth 8)	~1,500	~10,500	~1,500	525 ms – 1.05 s	150–300 ms
Xcode (depth 12, worst case)	~2,000+	~14,000+	~2,000+	~6 s	~0.3 s

The 6 s → 0.3 s figure is a 20× reduction observed on a large Xcode project tree with depth 12. The integration test CI gate asserts the Xcode snapshot completes in under 2 seconds at the default --max-depth 10.

Secondary optimisations

Cycle detection with FxHashSet The visited-pointer set used during depth-first traversal switched from std::collections::HashSet<usize> to rustc_hash::FxHashSet<usize>. Because the keys are raw machine-word pointers (not user-controlled), the non-cryptographic FxHash is appropriate and benchmarks at roughly 2× the throughput of the default SipHash.

Streaming JSON serialisation The snapshot output is written with serde_json::to_writer(BufWriter::new(stdout.lock()), &response) rather than to_string() followed by println!. This eliminates the intermediate heap allocation for the full JSON string, which matters for large trees (Xcode-scale output can exceed 200 KB).

Messaging timeout AXUIElementSetMessagingTimeout(element, 2.0) is set on the application element immediately after creation. This caps how long a single IPC call can block when the target application is busy or hung, preventing the snapshot from stalling indefinitely.

Development

Build

cargo build                  # debug build
cargo build --release        # optimized, stripped binary (<15MB)

Test

cargo test --workspace       # all unit tests
cargo clippy --all-targets -- -D warnings

Add a command

Adding a command touches exactly five files:

crates/core/src/commands/{name}.rs — implement execute(args, adapter)
crates/core/src/commands/mod.rs — register the module
src/cli.rs — add a subcommand variant and arg struct
src/dispatch.rs — add a match arm
crates/core/src/action.rs — add an Action variant if a new native action is needed

No existing files change beyond these registration points.

Coding standards

400 LOC hard limit per file — split by responsibility when approaching
No inline comments — names must be self-documenting; /// doc-comments on public items only when necessary
Zero unwrap() in non-test code — propagate with ? or match explicitly
One command per file, one domain type per file
Explicit pub boundaries — only lib.rs re-exports; internal modules use pub(crate)

Roadmap

Phase	Status	Scope
Phase 1	✅ Complete	macOS adapter, 30 commands, core engine
Phase 2	🔜 Planned	Windows (UIAutomation), Linux (AT-SPI), 10+ new commands
Phase 3	🔜 Planned	MCP server mode (`--mcp`), JSON Schema generation
Phase 4	🔜 Planned	Daemon, sessions, enterprise quality gates

Phases 2–4 add adapters, transports, and hardening. The core engine is not rebuilt.

License

Apache-2.0 — see LICENSE.

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agent-desktop

How it works

Installation

Build from source

Requirements

macOS permissions

Quick start

The ref system

JSON output

Error codes

Exit codes

Commands

Observation

snapshot

find

screenshot

get

is

Interaction

click / double-click / right-click

type

set-value

focus

select

toggle

expand / collapse

scroll

Keyboard

press

App & window management

launch

close-app

list-apps

list-windows

focus-window

Clipboard

clipboard-get

clipboard-set

Wait

wait

System

status

permissions

version

Batch

Common agent patterns

Observe → identify → act

Handle stale refs

Wait for async UI

Automated form fill

Architecture

Dependency inversion

PlatformAdapter trait

Platform support

macOS implementation

Performance

Snapshot tree: 6 s → 0.3 s

Measured benchmarks

Secondary optimisations

Development

Build

Test

Add a command

Coding standards

Roadmap

License

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`snapshot`

`find`

`screenshot`

`get`

`is`

`click` / `double-click` / `right-click`

`type`

`set-value`

`focus`

`select`

`toggle`

`expand` / `collapse`

`scroll`

`press`

`launch`

`close-app`

`list-apps`

`list-windows`

`focus-window`

`clipboard-get`

`clipboard-set`

`wait`

`status`

`permissions`

`version`