cua-driver

Orchestrates macOS app automation via cua-driver. Whenever a user asks to drive a native macOS app, follow the loop in this skill rather than calling tools ad-hoc — the snapshot-before-action invariant is not optional and silently breaks if you skip it.

DeepChat MCP mode

When DeepChat auto-pins this skill because the Computer Use MCP server is enabled, use the available Computer Use tools in the current tool list directly. Treat examples such as click({...}) or get_window_state({...}) as calls to the matching MCP tool with the same JSON payload. Shell CLI examples are diagnostic references for shell-based agents.

App-name resolution belongs here. When matching a user request to an app, compare the request with each list_apps name and bundle_id. Consider the user's language, system language, English product names, English brand names, romanized or pinyin variants, and common abbreviations. Treat bundle_id as the strongest identity signal. When the requested app name is ambiguous, localized, translated, abbreviated, or written in another script, call list_apps, resolve the most credible bundle id, then call launch_app with that bundle id.

Sparse visible UI fallback

Many media and Electron apps expose a shallow AX tree while still showing enough pixels to act. Spotify-style snapshots with only AXWindow, title-bar buttons, and a menu bar are still actionable when the screenshot shows a visible, unambiguous target.

For a user-requested non-destructive action, continue within the same turn through the safest visible options:

1. Re-snapshot once if the first tree looks sparse.
2. Use zoom on the relevant screenshot region when the screenshot is

wide, dense, or the target is small.

1. Prefer in-window controls visible in the screenshot: cards, primary

buttons, bottom player controls, search fields, sidebars.

1. Use pixel click({pid, window_id, x, y}) or `click({pid, window_id,

x, y, from_zoom: true})` for visible targets missing from AX.

1. Re-snapshot after each action and look for evidence: selected state,

text changes, playback progress, button icon changes, new panels, highlighted rows, or changed window content.

1. If the first safe click has no observable effect, try the next

visible, semantically related target before asking the user.

Ask for user confirmation only when the visible candidates are ambiguous, the action is destructive, the target is off-screen, or the next step requires foregrounding the app. When the AX tree is weak and the screenshot presents clear controls, continue with the visual fallback steps above.

Menu-bar fallback is valid when the target app is already frontmost and the menu item names match the user's requested action. Inspect menus such as File, Edit, View, Playback, Window, and Help for semantic commands, then dispatch menu actions and re-snapshot. For backgrounded apps, prefer in-window AX or pixel actions.

The no-foreground contract — read this first

The user's frontmost app MUST NOT change. This is the whole reason cua-driver exists. Users pay for the right to keep typing in their editor while an agent drives another app in the background. Violate this rule and every other nice property the driver gives you (no cursor warp, no Space switch, no window raise) stops mattering — you just shipped the Accessibility Inspector with extra steps.

Before running any shell command, ask: "does this raise, activate, foreground, or make-key any app?" If yes, don't run it. Every one of the commands below activates the target on macOS and is therefore forbidden unless the user explicitly asked for frontmost state:

• **Every form of the open CLI — open -a <App>, `open -b

<bundle-id>, open <file>, open <path-to-App.app>, open <url> — always activates.** macOS routes all forms through LaunchServices, which unhides and foregrounds the target regardless of whether you passed an app name, a bundle id, a document, a URL, or the bundle path itself. The activation happens even when the only intent was "start the process." **Never use open for any app launch.** This includes launching a just-built .app from a local build dir (e.g. open build/Build/Products/Debug/MyApp.app) — resolve the CFBundleIdentifier from Info.plist and use launch_app with that id. See "The narrow carve-out" below for why launch_app is safe even when the app internally calls NSApp.activate`.

• osascript -e 'tell application "X" to activate' —

activates by design. Same for ... to open <file>, ... to launch, and anything with activate in the tell block.

• osascript -e 'tell application "System Events" to ... frontmost'

in a mutating form (setting frontmost rather than reading it).

• AppleScript files that invoke activate, launch, or open

against the target app.

• cliclick (moves the user's real cursor to the target coords

before clicking — a focus-steal-equivalent even if the app's window state is unchanged).

• CGEventPost with cghidEventTap targeting a coordinate over

a different app's window (warps the cursor, possibly activates on hit).

• AppleScriptTask, NSAppleScript, Process wrapping osascript

that contains any of the above.

• NSRunningApplication.activate(options:) called from your own

helper binary — same class.

• Dock clicks and any open invocation (see the first bullet —

every form of open goes through LaunchServices which activates, full stop).

• **Keyboard shortcuts that semantically mean "focus here" —

most notably Chrome / Safari / Arc's ⌘L (focus omnibox) and Finder's ⌘⇧G (Go to Folder). These aren't pure key events — the receiving app interprets "user wants to type here" as activation intent and raises its window to be key. Even when delivered to a backgrounded pid via `hotkey`, the downstream app pulls focus. For omnibox navigation specifically**, the correct path is launch_app({bundle_id: "com.google.Chrome", urls: ["https://…"]}) — no omnibox dance, no ⌘L, no focus-steal. Do NOT try set_value on the omnibox: Chrome's commit logic requires a "user-typed" signal that neither an AX value write nor CGEvent.postToPid keystrokes supply from a backgrounded pid — the URL lands in the field but Return fires as a no-op. See WEB_APPS.md → "Navigate to a URL" for the full pattern. The general principle: a shortcut that says "put my cursor inside this app" is a focus-steal; a shortcut that says "do this thing" (copy, save, quit) is fine.

• **Tab-switching shortcuts in browsers (⌘1..⌘9, ⌘], ⌘[,

⌘⇧[, ⌘⇧]) are visibly disruptive even when delivered to a backgrounded pid.** The app's key handler processes the shortcut, the window re-renders the new tab's content, the user sees their tabs flipping. There is no AX-only workaround: page content (HTML, form state, AXWebArea) populates only for the focused tab; inspecting a background tab requires activating it, which is the visible flip. Observed with Dia; the same mechanic applies to every Chromium-family browser (Chrome, Arc, Brave, Edge).

Prefer the windows-over-tabs pattern: for each URL you need to drive backgrounded, use launch_app({bundle_id, urls: [url]}) — browsers open each URL in a new window. Each window has its own window_id, its own AX tree, and can be inspected / interacted with via element_index without activating or switching anything. Tabs are a UX grouping for humans; cua-driver workflows should default to windows. See WEB_APPS.md → "Tabs vs windows" for the full pattern.

Tab-title enumeration (read-only) IS safe — walk a window's toolbar AX tree for AXTab / AXRadioButton children and read their AXTitles. Tab switching (activating one) is not.

Reading frontmost state is fine (osascript -e 'tell application "System Events" to get name of first application process whose frontmost is true'). Mutating it is not.

Corollary — the AXMenuBar rule. AXMenuBarItem + AXPick dispatches at the AX layer regardless of which app is frontmost, but macOS's on-screen menu bar always belongs to the frontmost app. If you drive a backgrounded app's menu bar, the AX call succeeds but the viewer sees the dispatch rendered over the frontmost app's menu bar — confusing in any observed session and routinely a silent no-op too, because action menu items go DISABLED when their owning app isn't the key window. So: only use menu-bar navigation when the target is already frontmost. For backgrounded targets, read state via in-window AX (window title, toolbar AXStaticText) and dispatch via in-window element_index or pixel clicks — both paths are frontmost-insensitive. Full rationale in "Navigating native menu bars" below.

"Open \<app\>" in user speech means launch, not activate. cua-driver launch_app is the one correct path for process startup — it's idempotent (no-op on a running app), returns the pid, and has an internal FocusRestoreGuard that catches NSApp.activate(ignoringOtherApps:) calls the target makes during application(_:open:) and clobbers the frontmost back to what it was before the launch. That guard is why launch_app with urls (e.g. {"bundle_id": "com.colliderli.iina", "urls": ["~/video.mp4"]}) is safe even for apps that normally foreground on media-load (Chrome, Electron, media players).

Defaults — always prefer cua-driver over shell shims

Default transport is the `cua-driver` CLI — Bash shelling out to cua-driver <tool-name> '<JSON-args>'. MCP tools (prefix mcp__cua-driver__*) only when the user explicitly asks for them. CLI wins because it picks up rebuilds instantly, failures are easier to diagnose, and there's no per-tool schema-load overhead.

Every reference to click(...), get_window_state(...) etc. in this skill means cua-driver click '{...}' — translate to MCP form only when MCP is requested.

Intent → tool mapping. If you find yourself reaching for the right column, something has gone wrong — re-read "The no-foreground contract" above:

The narrow carve-out

The only legitimate use of osascript -e 'tell app X to activate' is when the user explicitly asked for frontmost state ("bring Chrome to the front", "make it frontmost", "I want to see X"). Reaching for it because a tool call returned something confusing is wrong — that's the skill's classic foot-in-the-door failure mode and it steals focus every time.

When a cua-driver call surprises you, diagnose cua-driver first:

• Tiny screenshot / empty `tree_markdown`? Check

cua-driver get_config → capture_mode. Default "vision" omits the AX tree (PNG only), "ax" omits the PNG, "som" returns both. If a snapshot lacks a tree, capture_mode is almost certainly "vision" — either reason purely from the PNG or flip to "som" / "ax" via set_config.

• `has_screenshot: false`? The window capture failed (transient

race against a close, or the window has no backing store yet). Re-snapshot; if persistent, pick a different window_id via list_windows.

• `Invalid element_index` / `No cached AX state`? You either

skipped get_window_state this turn or passed a different window_id than the one the snapshot cached against. The cache is keyed on (pid, window_id) — indices don't carry across windows of the same app. Re-snapshot with the same window_id you're about to click in.

• Sparse Chromium AX tree? Retry get_window_state once — the

tree populates on second call.

Only after those are ruled out, and only if the user's action genuinely needs frontmost state, fall through to the activate fallback. Always name the focus steal in your response ("I'll briefly bring Chrome to the front because …").

Self-check pattern

Before every Bash call whose command line touches any macOS app (launching, opening, clicking, typing, scripting, screenshotting), run the self-check:

1. Does this command foreground the target? If yes — stop and

translate to the cua-driver equivalent from the mapping table.

1. Does this command move the user's real cursor? (cliclick,

any CGEventPost at cghidEventTap over another app's window). If yes — stop; use click({pid, x, y}) which routes per-pid via SkyLight and never warps the cursor.

1. Does this command bypass cua-driver entirely? (osascript

mutating GUI state, AppleScript files, external helpers.) If yes — stop; find the cua-driver tool that does the intent.

If all three are "no," the command is safe. If you can't answer, default to stop and ask rather than proceed. A single open -a run by accident kills the demo, the trust, and the user's in-flight editor state.

Prerequisites — check before starting

1. cua-driver is on $PATH (which cua-driver). If not, point the

user at scripts/install-local.sh and stop.

1. Run cua-driver check_permissions (with the daemon up — see step 3).

The default behavior also raises the system permission dialogs for any missing grants, so the user can grant on the spot. If either grant still reads false after that (user dismissed the dialog), tell them to open System Settings → Privacy & Security and grant Accessibility and Screen Recording to DeepChat Computer Use.app, then stop. Pass '{"prompt":false}' for a purely read-only status check that won't steal focus.

1. Start the daemon with open -n -g -a "DeepChat Computer Use" --args serve (the

recommended form — goes through LaunchServices so TCC attributes the process to DeepChat Computer Use.app). cua-driver serve & also works; the CLI auto-relaunches through open -n -g -a "DeepChat Computer Use" when it detects a wrong-TCC context (any IDE-spawned shell: Claude Code, Cursor, VS Code, Conductor). Verify with cua-driver status.

Using cua-driver from the shell

Tool names are snake_case, management subcommands are kebab-case — no ambiguity. Tools invoked as cua-driver <tool-name> '<JSON-args>'. Management subcommands:

• open -n -g -a "DeepChat Computer Use" --args serve — start persistent daemon

(required for element_index workflows; without it each CLI invocation spawns a fresh process and the per-pid element cache dies between calls). cua-driver serve & also works — the CLI auto-relaunches via open when the shell's TCC context is wrong. Pass --no-relaunch / CUA_DRIVER_NO_RELAUNCH=1 to opt out.

• cua-driver stop / status
• cua-driver list-tools, describe <tool>
• cua-driver recording start|stop|status — see RECORDING.md

Canonical multi-step workflow:

open -n -g -a "DeepChat Computer Use" --args serve
cua-driver launch_app '{"bundle_id":"com.apple.calculator"}'
# → {pid: 844, windows: [{window_id: 10725, ...}]}
cua-driver get_window_state '{"pid":844,"window_id":10725}'
cua-driver click '{"pid":844,"window_id":10725,"element_index":14}'
cua-driver stop

Agent cursor overlay

Visual cursor overlay for demos and screen recordings. Default: enabled. Toggle with cua-driver set_agent_cursor_enabled '{"enabled":true|false}'. A triangle pointer Bezier-glides to each click target, ring-ripples on landing, idle-hides after ~1.5s. Motion knobs: set_agent_cursor_motion takes any subset of start_handle, end_handle, arc_size, arc_flow, spring — tuneable at runtime, persisted to config.

Requires an AppKit runloop, which cua-driver serve / mcp bootstraps. One-shot CLI invocations skip the overlay entirely.

The core invariant — snapshot before AND after every action

Every action MUST be bracketed by `get_window_state(pid, window_id)`:

• Before — the pre-action snapshot resolves the element_index

you're about to use. Indices from previous turns are stale; the server replaces the element index map on every snapshot, keyed on (pid, window_id). Indices from turn N don't resolve in turn N+1, and indices from window A don't resolve against window B of the same app. Skip this and element-indexed actions fail with No cached AX state.

• After — the post-action snapshot verifies the action actually

landed. Without it you can't tell a silent no-op from a real effect. The AX tree change (new value, new window, disappeared menu, disabled button, etc.) is your evidence that the action fired. If nothing changed, the action probably failed silently — say so, don't assume success.

This applies to pixel clicks too — re-snapshot after to confirm the click landed on the intended target.

Why window selection is the caller's job now

get_app_state used to pick a window for you via a max-area heuristic that returned the wrong surface on apps with large off-screen utility panels. Concrete reproducer: IINA's OpenSubtitles helper (600×432 off-screen) out-area'd the visible 320×240 player window, so get_app_state(pid) screenshot'd the invisible panel and clicks landed there silently. The new get_window_state(pid, window_id) makes the caller name the window explicitly — the driver validates that the window belongs to the pid and is on the current Space, then snapshots exactly what was asked for. Enumerate candidates via list_windows or read the windows array launch_app already returns.

Behavior matrix

Two orthogonal axes shape what the agent can do.

capture_mode → addressing mode

vision was renamed from screenshot — the old name still decodes as a deprecated alias, so an on-disk "capture_mode": "screenshot" keeps working. Default is som so element_index clicks work the first time a user calls get_window_state; the other modes are opt-in when the caller specifically doesn't want one half of the work. Note the tool named screenshot is separate (raw PNG, no AX walk) and unrelated to the capture mode.

When a snapshot looks wrong (tiny screenshot / empty tree), check cua-driver get_config for capture_mode before anything else.

Pure-vision mode has its own caveats — Claude Code's vision pipeline downsamples dense text aggressively, so pixel grounding takes multiple correction cycles on text-heavy UIs. Read SCREENSHOT.md before driving anything in that mode; it documents the iterate/annotate/verify recipe plus the JPEG-over-PNG finding.

Window state → what works

Critical cell — minimized + keyboard commit. The keystroke reaches the app but AX focus doesn't propagate to renderer focus on a minimized window. Workarounds in order of preference: set_value to write the field's entire value directly, or AX-click a commit-equivalent button (Go, Submit, checkbox). Tell the user the window needs to un-minimize only as a last resort.

The canonical loop

launch_app(target)
  → pick window_id from the returned `windows` array
    (or call list_windows(pid) separately)
  → get_window_state(pid, window_id)
    → [act]  # every action also takes (pid, window_id)
  → get_window_state(pid, window_id) → verify

launch_app now returns a windows array alongside the pid, so the common case collapses to two calls (launch_app → get_window_state) without a separate list_windows hop.

1. Resolve target pid — always via launch_app

Always start with `launch_app`, whether or not the target is already running. It's idempotent (relaunching returns the existing pid with no side effects) and gives you the pid in one call — no list_apps hop.

• launch_app({bundle_id: "com.apple.finder"}) — preferred, unambiguous.
• launch_app({name: "Calculator"}) — when bundle_id isn't known.

launch_app is a hidden-launch primitive by design — that's the entire point of cua-driver: agents drive apps in the background while the user keeps typing in their real foreground app. The target's window is initialized (AX tree fully populated, clickable via element_index, the pid appears in list_apps) but not drawn on screen. The driver never activates or unhides apps on its own; that would violate the no-foreground contract the whole driver exists to protect.

If the user explicitly wants the window visible (usually for a demo or recording), they unhide it themselves — Dock click, Cmd-Tab, or Spotlight. Do not reach for open / osascript activate as a shortcut to make the window visible; those paths break the backgrounded invariant on every call, not just the call that "needed" the foreground. Say out loud what the user needs to do ("click the Todo app in your Dock to bring it forward") and let them do it.

Never shell out to any form of open (including open <path-to-App.app> for a just-built binary — resolve the bundle id from Info.plist and use launch_app with that), osascript 'tell app … to launch/open', or similar. Those paths activate the target, bypass the driver's focus-restore guard, and require a Bash permission prompt the agent loop shouldn't be burning on app launch. See "Prefer cua-driver tools over shell shims" above for the full intent → tool mapping.

list_apps is for app-level discovery (answering "what's installed / running / frontmost?") — not part of the core action loop. Skip it in the loop. For window-level questions — "does this app have a visible window?", "which Space is this window on?", "which of this pid's windows is the main one?" — call list_windows instead; the app record doesn't carry window state on purpose. In the common single-window case you can skip list_windows entirely and read the windows array that launch_app already returned.

2. Snapshot and act by element_index

Call get_window_state({pid, window_id}) with the window_id from launch_app's windows array (or a fresh list_windows({pid}) if you're interacting with a long-lived process). In the default vision capture_mode the response carries only the screenshot — no AX tree — so the canonical loop is list_windows → get_window_state → reason over PNG → pixel click. When you need element_index dispatch (AX-addressable elements, backgrounded clicks), flip to som first: cua-driver set_config '{"key": "capture_mode", "value": "som"}', then call get_window_state again. The rest of this section walks through som mode, which is what you want once you've decided element-indexed addressing is required.

In som mode the response carries:

• tree_markdown — every actionable element tagged [N]. That N

is the element_index. The tree can be very large (Finder is ~1600 elements, ~190 KB); when it exceeds token limits the MCP harness saves it to a file and returns the path. Use Bash + jq -r '.tree_markdown' + grep to pull the section you need.

• screenshot_png_b64 + screenshot_width / _height /

_scale_factor — the window screenshot (actually JPEG-85 despite the _png_ field name, hard-coded in WindowCapture.captureFrontmostWindow). Present in som mode (spliced into the structured JSON alongside the tree). In vision mode the image arrives as a native MCP image content block with no structured wrapper. Omitted when the target has no on-screen window.

• has_screenshot: bool — gate on this before piping the PNG.

Otherwise jq -r '.screenshot_png_b64' emits the literal "null", base64-decodes into 3 bytes of garbage, and downstream vision APIs reject it with an opaque "Could not process image" error.

# canonical, works in every capture mode — writes the image bytes
# wherever you point, stdout stays readable (tree in som, summary
# in vision). stderr warns (exit 0) if the response had no image.
cua-driver get_window_state '{"pid":N,"window_id":W}' --image-out /tmp/shot.png

# som-only legacy path: pull the spliced base64 out of structuredContent.
# Prefer --image-out above — it's one flag vs a probe + pipe.
if [ "$(cua-driver get_window_state '{"pid":N,"window_id":W}' | jq -r '.has_screenshot')" = "true" ]; then
  cua-driver get_window_state '{"pid":N,"window_id":W}' | jq -r '.screenshot_png_b64' | base64 -d > shot.png
fi

Reason over both the tree AND the screenshot — they're complementary, not redundant. In som mode every turn's get_window_state gives you both halves and you should pull signal from each:

• The AX tree tells you what's clickable — roles, labels,

element_index handles, advertised actions, parent-child structure. This is the ground truth for dispatching.

• The screenshot tells you which one — the tree often has

many buttons with similar or empty labels ("Delete", "OK", anonymous UUID-labeled buttons, five AXStaticText = " "), and visual context disambiguates. Captions, colors, layout relationships visible in pixels often don't show up in the AX tree at all (especially in Chromium / Electron / web content).

Canonical AX pattern: look at the screenshot to decide "the blue Subscribe button on the top-right of the video card", then walk the tree to find the matching AXButton and dispatch by its element_index. This is the preferred path when the target is present in the AX tree.

Canonical visual fallback: if the requested control is visible in the screenshot and the AX tree is sparse, generic, or missing that control, click the window-local screenshot coordinates in the same turn. Use click({pid, window_id, x, y}); after a zoom call use click({pid, window_id, x, y, from_zoom: true}). Re-snapshot after the click to verify. Continue without asking for an extra "go ahead" when the user already requested the action and the target is visible and unambiguous. Pause only when the target is visually ambiguous, off-screen, destructive, or would require foregrounding the app.

The actions=[...] list on each element is advisory, not authoritative. cua-driver does not pre-flight check against it — click({pid, element_index}) always attempts AXPress (or the action you pass) and surfaces whatever the target returns. Many apps accept AXPress on elements that don't advertise it — Chrome's omnibox suggestion AXMenuItem is a live example. Try the click first — pivot only on the returned AX error code.

Dispatch table (every row assumes a (pid, window_id) pair from the last get_window_state; window_id is required alongside element_index, ignored on pixel-only forms unless you want to anchor the conversion against a specific window):

All keyboard/text primitives require `pid`. There is no frontmost-routed variant — every key goes to the named target via CGEvent.postToPid, so the driver cannot leak keystrokes into the user's foreground app.

Why `element_index` is the primary path: works on hidden / occluded / off-Space windows, no focus steal, stable across rebuilds, labels tell you what you're clicking. Use pixel coordinates as the active fallback for visible self-drawn controls, canvas/video/WebGL surfaces, and sparse AX trees.

Pixel-coordinate clicks

The pixel path (click({pid, x, y})) is for surfaces the AX tree doesn't reach — canvases, video players, WebGL, custom-drawn controls. Coords are window-local screenshot pixels (same space as the PNG get_window_state returns). Top-left origin, y-down. The driver handles screen-point conversion internally. Passing window_id alongside x, y is optional but recommended — it pins the coordinate conversion to the window whose screenshot produced the pixel, rather than the driver's heuristic choice.

#### Reading coordinates from the PNG

PNGs returned by get_window_state are capped at 1568 px long-side by default (max_image_dimension config), matching Anthropic's multimodal-vision downsampling limit. That means the image the model reasons over and the image the click tool's coordinate system lives in are the same resolution — just look at the PNG, pick a pixel, click at that pixel. No scaling math.

This is the default because the mismatch between "rendered thumbnail" and "native PNG" was a recurring coord-estimation footgun. If you opt out (explicit max_image_dimension=0 for pixel-perfect verification flows), the old rule applies: don't eyeball coords from whatever your client renders — it may be 2-4× smaller than the PNG on disk, and a 2% error in thumbnail space becomes ~80 px in the real image. Use the crosshair recipe below against the full-resolution file in that case.

1. get_window_state({pid, window_id}) returns an image capped

at 1568 long-side (default) plus its dimensions (screenshot_width / screenshot_height). Write the bytes to disk with --image-out <path> in any capture mode — works identically in vision (where it's the only way) and som (where it sidesteps the jq + base64 dance on the spliced screenshot_png_b64 field).

1. You are a multimodal model — look at the PNG. Since the PNG

matches what you see, pick the target pixel directly. No fractional math needed.

1. When precision matters (small targets, dense UIs), draw a

crosshair on the image (do not crop — cropping loses the coordinate system and requires error-prone offset math) and show it before clicking:

from PIL import Image, ImageDraw
img = Image.open('/tmp/shot.png')
draw = ImageDraw.Draw(img)
x, y = <your_coordinate>
r = 18
draw.ellipse([x-r, y-r, x+r, y+r], outline='red', width=4)
draw.line([x-30, y, x+30, y], fill='red', width=3)
draw.line([x, y-30, x, y+30], fill='red', width=3)
img.save('/tmp/shot_annotated.png')

1. Only dispatch the click after the user (or your own re-read of

the annotated image) confirms the crosshair is on target.

#### Addressing variants

• click({pid, x, y}) — single left-click.
• click({pid, x, y, count: 2}) — double-click.
• click({pid, x, y, modifier: ["cmd"]}) — cmd-click. Accepts any

subset of cmd/shift/option/ctrl.

• right_click({pid, x, y}) — also takes modifier.

The pixel path animates the agent cursor overlay but never warps the real cursor. If the pid has no on-screen window the call errors with pid X has no on-screen window — you need a visible window to anchor the conversion.

#### How the pixel click is dispatched

The recipe is the backgrounded "noraise" sequence: yabai's focus-without-raise SLPS event records followed by an off-screen user-activation primer and the real click, all stamped via SLEventPostToPid. The target app becomes AppKit-active for event routing but its window does not rise to the front of the z-stack, and macOS's "switch to Space with windows for app" follow is suppressed. Full mechanics in Sources/CuaDriverCore/Input/MouseInput.swift (clickViaAuthSignedPost) and the companion FocusWithoutRaise.swift.

#### Known limits

• Chromium `<video>` play/pause: pixel click is often rejected

by HTML5's click-to-play handler on some builds. Use keyboard instead: press_key({pid, key: "k"}) (YouTube) or press_key({pid, key: "space"}) (generic). Keyboard events travel through a different auth envelope.

• Pixel right-click on Chromium web content coerces to a

left-click — a known Chromium renderer-IPC limitation that affects every non-HID-tap synthesis path. For context menus on AX-addressable elements (links, buttons, toolbar items), use right_click({pid, element_index}) instead.

Canvases, viewports, games (Blender, Unity, GHOST, Qt, wxWidgets)

Apps whose main surface is an OpenGL / Metal / Qt / wxWidgets viewport expose no useful AX tree — the whole surface is one opaque AXGroup or AXWindow from AX's perspective. Per-pid event paths (SLEventPostToPid, CGEvent.postToPid) are filtered by the viewport's own event-source check and silently dropped — the event loop wants "real HID origin".

The working pattern:

1. Bring the target frontmost (a brief osascript activate is

acceptable here — this is the carve-out the skill's osascript gate allows).

1. CGEvent.post(tap: .cghidEventTap) with a leading mouseMoved

event (~30 ms before the click). cua-driver click when the target is frontmost automatically takes this path.

1. Accept that the real cursor visibly moves — cghidEventTap is

the system HID stream, the cursor warps to the click point.

There is no backgrounded path that reaches these apps today.

Navigating native menu bars (AXMenuBar)

Only drive the menu bar when the target app is frontmost. This is the single most-misused cua-driver capability. If the target is backgrounded, don't reach for AXMenuBarItem + AXPick — use in-window element_index or pixel clicks instead. Two reasons, one functional and one perceptual:

• Functional: menu items that touch document/playback/editor

state go DISABLED when their owning app isn't the key window (Preview rotate, IINA speed change, most editor commands). AXPick + AXPress will dispatch successfully from the driver's side but no-op at the target — you get a silent false-pass.

• **Perceptual (matters for demos, screen recordings, and anything

the user watches live):* macOS's screen-rendered menu bar always belongs to the frontmost* app. AXPick on a backgrounded app's AXMenuBarItem dispatches to that app's per-process menu at the AX layer, but any visible menu render happens over the frontmost app's menu bar — the viewer sees an IINA submenu flashing on top of Chrome's menus, which reads as "the agent clicked the wrong app." The AX call was correct; the frame the user sees is not. For recorded or observed sessions, this is an integrity bug even though it's not a correctness bug.

Good decision rule: if the target is not already frontmost, do not use AXMenuBarItem at all. For reading in-window state, snapshot the window AX tree — most apps expose the same state via an in-window AXStaticText, title bar, or toolbar. For dispatching actions, use in-window element_index (buttons, toolbar items) or pixel clicks on in-window controls — both dispatch via AppKit's window-under-pointer hit-test and are not frontmost-gated.

When the target IS frontmost, the menu-bar flow below is fine and the canonical path for menus.

The two-snapshot pattern (target frontmost only)

Menu contents are a two-snapshot flow. Closed AXMenu subtrees are deliberately skipped during snapshot — otherwise every app's File / Edit / View hierarchy plus every Recent Items macOS has ever seen would inflate the tree 10-100x. But once a menu is open, its AXMenuItem children do receive element_index values so you can click them normally.

1. Find the [N] AXMenuBarItem "<Menu Name>" in the tree.
2. click({pid, element_index: N, action: "pick"}) — menu bar items

implement AXPick ("open my submenu"), not AXPress. Using the default action on an AXMenuBarItem is a no-op.

1. Re-snapshot. The expanded menu's items now appear under the bar

item as [M] AXMenuItem "<Item Name>".

1. Click the target item — most items respond to AXPress (default

action). Submenus nest under the item and are walked the same way.

1. Re-snapshot and verify.

If you ever need to back out without selecting, press_key({pid, key: "escape"}) closes the open menu. Leaving a menu expanded between turns poisons subsequent snapshots for that pid.

Commands gated on the target being frontmost

Some menu items and global shortcuts (Preview's Tools → Rotate Right, ⌘R; anything in the View menu that manipulates the current document; most editor commands) are disabled unless the target app is the key / frontmost window. You'll see it in the AX tree as DISABLED on the menu item even though the user's intent is obviously valid.

Before activating, confirm you're in this narrow case — the menu item still reads DISABLED after a fresh snapshot AND the action the user requested genuinely requires frontmost (Preview rotate, View menu document manipulation, editor commands). If either check fails, don't activate.

When both checks pass, the driver has no activate tool (deliberately — the whole point is backgroundable control), so this is the one legitimate osascript fallback:

osascript -e 'tell application "<App Name>" to activate'

Then re-snapshot — the menu item loses its DISABLED tag — and click({action: "pick"}) the item. Alternatively, a hotkey call delivered to the now-frontmost app works for the shortcut form (⌘R, ⌘+, etc.).

Always name the focus steal in your response so the user isn't surprised — "Briefly activating Preview to enable Tools → Rotate Right" or similar. Don't silently steal focus. You don't need to restore the previous frontmost afterwards unless the user asks — they can cmd-tab back.

Web-rendered apps (browsers, Electron, Tauri)

For Chrome / Edge / Brave / Arc / Safari, Electron apps (Slack, VSCode, Notion, Discord), and Tauri apps — see `WEB_APPS.md`.

Covers: sparse AX tree population (retry-once pattern for Chromium), URL navigation via omnibox suggestions, the set_value workaround for keyboard commits on minimized windows (Return silently no-ops — symptom is a macOS system beep; use set_value or click a clickable equivalent), scrolling via synthetic PageUp/Down keystrokes, in-page clicks, and typing into web inputs.

Chromium web content specifically also coerces right_click back to left — use element_index for AX-addressable targets and accept the limit otherwise.

Browser JS primitives — page tool and get_window_state(javascript=)

When the AX tree doesn't expose the data you need (common in Chromium/Electron — the tree is sparse for web content), use the page tool or the javascript param on get_window_state to query the DOM directly via Apple Events. Requires "Allow JavaScript from Apple Events" to be enabled — see WEB_APPS.md for the setup path.

Three actions on the `page` tool:

• page({pid, window_id, action: "get_text"}) — returns

document.body.innerText. Fastest way to read page content, prices, article text, or any raw text the AX tree truncates or omits.

• `page({pid, window_id, action: "query_dom", css_selector: "a[href]",

attributes: ["href"]}) — runs querySelectorAll` and returns each match's tag, text, and requested attributes as a JSON array. Use for table rows, link hrefs, data attributes, structured page data.

• `page({pid, window_id, action: "execute_javascript", javascript:

"..."}) — raw JS. Wrap in an IIFE with try-catch. Don't use this for elements already indexed by get_window_state — click and set_value` are more reliable there.

Co-located read — `get_window_state` with `javascript`:

get_window_state({pid, window_id, javascript: "document.title"})

Runs the JS and appends the result as a ## JavaScript result section alongside the AX snapshot — one round-trip instead of two. Use this when you need both the element tree (for subsequent clicks) and some page data in the same turn.

Decision rule — AX vs JS:

Supported backends:

Electron sandbox note: SIGUSR1 connects to the Node.js main process. Sandboxed Electron apps (VS Code, Cursor) strip require and Electron APIs there. Useful for: process.env, process.versions, process.cwd(), process.pid. For full DOM/renderer access, launch the app with --remote-debugging-port=9222 — cua-driver will detect and prefer the page target automatically.

Arc returns no values; Firefox has no JS-via-AppleEvents support — see WEB_APPS.md for the full matrix.

3. Re-snapshot and verify — mandatory

Always call get_window_state({pid, window_id}) after the action. This isn't optional verification — it's the second half of the snapshot invariant.

Check the AX tree diff: a changed value, a new element, a new window, or the disappearance of the thing you just clicked (menus collapse after selection, buttons may become disabled, etc.). If nothing changed, the action likely failed silently — tell the user what you attempted and what you observed, don't paper over with "done" language. Agents that skip this step report success on silently-dropped actions — the single most common failure mode.

Recording trajectories

Session-scoped action recording + replay, for demos, regressions, and training data. Only invoke when the user explicitly asks to record a session — the skill does not auto-enable this. CLI surface: cua-driver recording start|stop|status; raw tool: set_recording.

See `RECORDING.md` for the full flow: enable/disable, turn folder contents, replay via replay_trajectory, and the element_index doesn't-survive-across-sessions caveat.

Common error patterns

Things to avoid

• Never reuse an element_index across a re-snapshot of the same pid.
• Never translate screenshot pixels into a click — the screenshot

is for visual disambiguation, not coordinates. Use the element_index.

• Prefer AX over pixels. click({pid, x, y}) works for

canvas / WebView regions, but it lands blindly and skips the agent-cursor overlay. Exhaust AX paths (menu bars, cmd-k palettes, toolbar items, keyboard shortcuts) before dropping to coordinates.

• Never drive destructive actions (delete files, close unsaved

documents, send messages, submit forms) without explicit user intent for that specific destructive step.

• Never launch apps autonomously; confirm with the user first

unless their original request clearly implies the launch.

Example end-to-end task

User: "Open the Downloads folder in Finder."

1. launch_app({bundle_id: "com.apple.finder", urls: ["~/Downloads"]})

→ {pid: 844, windows: [{window_id: 6123, title: "Downloads", ...}]}. Idempotent launch; plus Finder opens a hidden window rooted at ~/Downloads via application(_:open:) — zero activation, no focus steal. The windows array lets you skip a list_windows hop.

1. get_window_state({pid: 844, window_id: 6123}) → verify an

AXWindow whose title contains "Downloads" is present with a populated AX subtree (sidebar, list view, files).

1. Done.

If the user instead asks to navigate within an already-open Finder window, use the menu-bar flow from the "Navigating native menu bars" section above (click Go → pick a menu item → re-snapshot → click it).