jev-desktop

Drive a desktop application from one plain-language goal, or resolve one intent at a time, without ever reading the accessibility tree. Use when automating a desktop app and you want to keep a 150-element JSON tree out of your context. Hand run.mjs a whole goal and it observes, decides and acts until the goal is met; hand act.mjs a single step when you want to keep the plan yourself. Covers which element, which operation, when to look deeper, and when to stop.

Two entry points over the same screen reading. run.mjs takes a goal and drives until it is met. act.mjs takes one step and hands the plan back to you. Neither puts the tree in your context.

The loop

sh

node scripts/jev/run.mjs --app Finder "open the Applications folder"
node scripts/jev/run.mjs --app TextEdit --cursor --text "A line to write." "write the supplied sentence into the document"

Each turn reads the screen, asks for one operation and a target for that operation in the same request, carries it out, and reads again. It prints one JSON line per turn and one when it stops.

json

{"turn":{"step":1,"operation":"CLICK","target":"treeitem \"Applications\"",
         "confidence":1,"ok":true,"delivery":"delivered_verified","changed":true}}
{"stop":"done","confidence":0.96}

The operations are CLICK, TYPE_TEXT, CHECK, UNCHECK, EXPAND, COLLAPSE, SCROLL, DRILL, WIDEN, WAIT, DONE and BLOCKED. Only the ones something on screen can receive are offered.

The target is asked once per operation. click_target is chosen from the elements that advertise Click, type_text_target from those that advertise SetValue, and so on. Only the head matching the chosen operation is read, so a target can never be incompatible with the verb that acts on it. That is the whole reason the loop does not need to correct itself afterwards.

Looking is an operation. A window is read with --skeleton first, so a document holding four thousand elements costs the same first look as a panel holding thirty. A region that was cut off reports how much it holds, and DRILL pins it as the root for later turns. WIDEN gives the whole window back.

CHECK and UNCHECK instead of a toggle. Both are idempotent, so a box already in the wanted state stays there and the policy never reasons about the current one.

You supply the text. Nothing here writes a value, so a run never puts a string on screen that you did not choose. Pass --text once per value and they are consumed in order, or pass a function as the text option and it is asked for each field with that field's description. When there is no value left to give, TYPE_TEXT is not offered at all, so the run stops rather than inventing one.

Text goes in by whichever route the application accepts. A direct value write is one verified call; applications that refuse it say so, and only then does the value go through the clipboard and a paste. The clipboard is put back when the run ends. One key press per character is never used: it drops characters and loses capitals.

What leaves the machine. Every turn posts a description of the screen to api.typesafe.ai: each element's role, its accessible name or description, up to sixty characters of the value it holds, its state, the window title, and the recent actions. That is enough to send the contents of a private document or a filled form. Secure text fields are already withheld by agent-desktop and never reach the request. Pass --no-values to withhold what every other field holds as well; targeting gets harder, because a value is often the only thing that tells two unnamed rows apart. Decide this before pointing a run at something confidential.

A step that is hard to undo is not taken quietly. The same request asks how hard the step would be to reverse. An ordinary step needs 0.70 confidence in its target, one rated destructive needs 0.90, and below 0.55 nothing runs. When the bar is not met the run stops and names the candidate it would have acted on, so you decide instead of it.

--cursor makes the run watchable. It starts a session, shows a cursor that travels to each element before the operation lands, and turns it off at the end. The cursor is drawn where the element is, so bring the application in front of your terminal or it arrives behind it.

It stops on DONE, on BLOCKED, on a confidence too low for the risk, after 40 actions, after 80 model calls, or after three turns that changed nothing.

A screen with more actionable elements than a choice can carry says so, in the request and in the turn it reports, and the policy is told to look inside a region rather than call the goal impossible.

--root @ref starts inside a region when you already know which one.

One step at a time

You keep the goal, the plan and the memory. You send one sentence. You get back one small object. The tree never enters your context.

sh

node scripts/jev/act.mjs --app TextEdit --execute \
  --text "Morning over the dock." "type this text into the main writing area"

json

{
  "ok": true,
  "app": "TextEdit", "window": "Untitled 3", "surface": "sheet",
  "element": { "ref": "@s1:e139", "role": "textfield", "name": "Save As:",
               "where": "sheet \"save\" > group" },
  "command": "set-value",
  "argv": ["set-value", "@s1:e139", "poem.txt"],
  "decision": "act",
  "confidence": { "target": 0.99, "command": 0.88 },
  "gates": { "present": 0.94, "destructive": 0.31, "needs_text": 0.87 },
  "runner_up": [{ "ref": "@s1:e137", "what": "textfield", "p": 0.02 }],
  "notes": [],
  "executed": { "ok": true, "delivery": "delivered_verified" }
}

Calling it

Flag	Meaning
--app <name>	Required.
--execute	Run the command when decision is act. Without it, nothing runs.
--text "…"	Text the intent needs. Jev returns choices, never strings.
--root @ref	Resolve inside one container instead of the whole window.
--bin <path>	agent-desktop binary. Defaults to the release build, then PATH.

Phrase the intent as an action, not as an element. "type this text into the main writing area" resolves to type. "the main writing area" names no operation and resolved to focus in testing. Describe the target the way a person would — "the field holding the name the file will be saved under" — not the way the tree names it.

Reading decision

decision	What it means	What you do
act	One element clearly matches and the confidence clears the bar for this action's risk.	Nothing. With --execute it already ran.
confirm	The match is plausible but under the bar.	Ask the user, or re-phrase the intent and call again.
abstain	Jev answered none, the element is probably not on this screen, or two elements fit equally.	The screen is not where you think. Open the surface you need, then call again.
needs_text	The command takes text and none was supplied.	Call again with --text.

why always carries the reason in one sentence. runner_up shows what else it considered, which is usually enough to tell a wrong screen from a vague intent.

What the script decides, not Jev

• Risk sets the bar. The answer says what; confidence says whether to act. An ordinary action needs 0.70. One that Jev rates destructive at 0.50 or more needs 0.90 — writing a file, deleting, sending, confirming a warning. Below 0.55 nothing acts at all.
• The command is reconciled against the element. Both questions are answered in parallel and neither sees the other, so code checks the chosen verb against the element's advertised actions. A readonly combobox gets click, never set-value. A --text payload with a non-text verb corrects the verb, because the caller supplying text is evidence Jev does not have.
• An open surface wins. When a sheet, alert, menu or popover is up, the script reads that surface instead of the window. In the window tree those elements carry offscreen and would all be dropped.
• Disabled and hidden elements are never offered. Everything else is, including unnamed rows — a row is told apart by the value it holds, and a Choice does better with the full list than with a shortlist.

How the request is shaped

One call carries five questions. They are answered in parallel, so the speculative ones cost tokens and no latency.

Question	Type	Asks
target	choice	Which element the intent refers to, plus none.
command	choice	Which of the 16 interaction verbs it asks for.
present	noul	Is the thing on this screen at all?
destructive	noul	Would this be hard to undo?
needs_text	noul	Does this need text from the caller?

A Choice accepts 255 options, so up to 254 elements go in one pass. When the first pass lands under 0.70 the top five are re-asked with richer descriptions. A screen with more than 254 elements says so in notes; use --root @ref.

Known limits

• One snapshot per call, about 3 s on a dense app. --root is far cheaper.
• No retry and no backoff. A 429 ends the call.
• Held input is unavailable, so no sustained key and no drag with hold. See crates/core/src/commands/input_hold_policy.rs.
• press is not resolved here. It needs no element, so send it directly.

Files

File	Holds
scripts/jev/policy.mjs	The operations, how a screen is described, and when to stop. No application is touched here.
scripts/jev/desktop.mjs	The only code that speaks to agent-desktop.
scripts/jev/run.mjs	The loop and its command line.
scripts/jev/act.mjs	The single-step resolver.

Checks

sh

node scripts/jev/act.test.mjs
node scripts/jev/run.test.mjs