Windows Computer Use (UI Automation)

Reads a Windows window as text - roles, labels, values, states, rectangles - through UI Automation, and performs actions on named elements through their UIA patterns. It ships with Ouroboros and is on by default on Windows only (os: win32); macOS and Linux use the bundled unix_computer_use. It deliberately does not take screenshots, click at coordinates or send general keystrokes, so surfaces that expose no UI Automation elements (canvas-drawn apps, remote desktops, some games) read as empty or partial.

Ported from Yegor Kosyrev's Praxis/Hélène uia.rs/element.rs, keeping its contracts. See NOTICE for source links, the upstream Apache-2.0 licence and attribution; the contribution's licensing is a separate matter.

Tools

• window_list - visible top-level windows that have a title (hwnd, title, class, pid, rect, foreground flag), front to back; untitled windows are left out. It stops at limit (default 100, at most 500, echoed back); a listing cut there says truncated_by: [limit] and total_known: false. Use it to pick an hwnd for the other tools.
• window_read - the whole window (or the one hwnd names) as a tree/flat list of elements: role, name, value, automation_id, class, rect with center, and a state block whose missing keys mean the element does not expose them - not false. Limits (max_nodes, max_depth, max_children_per_node, max_text_chars, timeout_ms) come back in the answer with their ceilings; every cut is named in truncated_by and notes, including result_size when a large reading is cut to what the host relays. backend=win32 forces the plain Win32 reader (classic child windows only); auto uses UIA then Win32, naming fallback_reason. Each reader has its timeout_ms budget; the host allows 50 seconds for both plus setup.
• element_find - search the tree by selector (automation_id, role, name, name_contains, value_contains; AND semantics), returning every match up to limit. timeout_ms=0 (default) means "look now"; a positive value waits for the first match.
• element_act - do something to the element a selector names: invoke | set_value | toggle | expand | collapse | select | scroll_into_view | focus. The action goes through the element's UIA pattern - there is no fallback to clicking at coordinates; if the element lacks the pattern the refusal lists the patterns it does support. set_value needs text as a string: "" clears the field, null is refused.

Selector contract (the important part)

• All given fields must match at once ("and", not "or"). automation_id is exact and case-sensitive; role/name fold case (Cyrillic included).
• Two matches without select.nth is a refusal with the match count and candidates (a display prefix if too large); the tool never picks for you.
• Supplied selector text fields must be non-blank strings. A number or null is rejected, not dropped; matching keeps the full original strings and whitespace.
• "Not found", "didn't finish reading the window" and "an element did not answer a field the selector names" are different answers (searched_whole_window, reason, unreadable_candidates) and are never confused: an unreadable candidate makes element_act refuse. On element_act, stopped_before_timeout_ms and last_walk_ms disclose an early wait stop.
• Ids index one answer only; re-find elements by automation_id/hwnd.

Honesty rules

• Receipts say what was invoked and what the element looks like after; whether the goal was achieved stays your judgment. action_outcome=completed means the call returned, not that the goal succeeded. Failed after-reads retain that outcome with after_read=partial|unavailable and named unread fields. An exception inside an action is action_outcome=unknown, distinct from a pre-call refusal; a worker that did not answer in time also leaves action_call_made=unknown. A host timeout/kill may prevent that receipt entirely; it proves no outcome. Check the window before retrying, never retry blindly.
• A completed mutating act (all but focus and scroll_into_view) carries observed_effect: true: its pattern call returned on that window, which is not proof that the goal was met; unknown outcomes and refusals never carry it. delivered_to names that window (hwnd, title, pid) whenever the call was made.
• A field the window failed to report is listed in the node's unread, not shown as missing.
• All four tools fit the host's JSON-string relay. Oversized displays name result_size, list shown/omitted counts and per-object clipped_fields (original/shown UTF-16 units); these are display cuts, not unread fields. Text is capped at 4000 UTF-16 units only when the answer is too large, then lists keep a fitting prefix. A document's text in receipts and candidates shows its first 4000 units (text_truncated when longer); value_contains matches the whole text. Narrow the selector or read/filter an inner window for more; action facts and original match counts are never discarded.
• A hung window normally produces a partial answer or named fallback; a slow child setup or host stop can instead return a host error. The skill runs as an isolated-dependency extension: every call executes in a short-lived child process the host can kill. The host installs tested comtypes==1.4.17 into the skill's own environment while the skill is on (at boot, or when it is turned on); a failed install stays the skill's dependency state and is retried at boot.

Scope and safety

Windows-only, in the interactive session Ouroboros runs in: windows of elevated processes may refuse an unelevated Ouroboros, and the secure desktop is out of reach. All actions are meant for supervised, low-risk workflows under human observation; prefer semantic application APIs when they exist, and ask before destructive or sensitive UI actions. focus and scroll_into_view are view-only (non-mutating); the rest change the target window. The owner can turn the skill off on the Skills page; updates keep that choice.