feat(desktop): keep the machine awake for background chats and yield the page to the user by waleedlatif1 · Pull Request #8671 · simstudioai/sim

waleedlatif1 · 2026-10-06T06:40:49Z

Summary

Phase 2c of the desktop background executor. Stacked on #8668.

Prevent sleep while a chat is running

While any chat has desktop work claimed on this machine, the app holds a prevent-app-suspension power blocker. It releases the blocker as soon as the last result is delivered. It never holds one while idle.
The behaviour is on by default, with a switch in Settings → Desktop. A one-line note says a closed lid still puts the computer to sleep, because the switch can't prevent that. The switch shows only when Sim runs chats on this device in the background.
A result that keeps failing to reach Sim holds the machine awake for at most 10 minutes. Delivery keeps retrying after that.
The switch is a new optional bridge method, settings.setPreventSleepWhileRunning, so older desktop builds don't show it.

The agent yields the page to the user (takeover)

Only calls from the background executor yield. A call from the chat view the user is watching behaves exactly as on staging, because there the user steers the agent directly.
A background call that only reads the page (snapshot, read text, list tabs) never waits, since it cannot collide with the user.
When the user clicks, scrolls or types in the page a background chat's agent is driving, that chat's next acting browser action waits. While it waits, the tab is marked as needing attention.
The action resumes in the same page once the user has left it alone for 4 seconds.
The wait is bounded at 30 seconds, or half the action's watchdog if that is shorter. A user who keeps working past that gets a clear "not run" rather than a timeout.
A user who starts working mid-action (between a batch's steps, or during a click's target probes) stops it before its next input. The result says earlier steps may have taken effect.
The activity counts only on the tab the user acted in.
A Stop still cancels an action while it waits.
browser_request_takeover keeps its own explicit hand-back flow.
Other chats' browsers are unaffected.

Not in this PR: a background chat's page dialog can still take focus

A page in a hidden chat that calls confirm() or alert() still takes focus from the user's window. Electron shows its native message box before the driver's CDP handler answers the dialog. This happens whether or not the executor runs the chat, and it overlaps with #8432's dialog work. Suppressing native dialogs (disableDialogs) would also break the agent's dialog: {accept: true} answers. I reproduced it in a packaged-app E2E and left it out of this PR so it can be decided with #8432.

Test plan

Unit tests (sleep-blocker.test.ts):
- one blocker is held only while work runs;
- the switch is followed live;
- an idle machine never starts one.
Packaged-app E2E (background-executor.spec.ts):
- I: synthetic user input in the agent's tab holds a background browser_click until 4 s of quiet. The click then runs exactly once.
- J: the blocker is taken when a background command starts and released once its result is delivered.
Both fail with the change reverted (mutation-checked). The full suite, A to J, passes in 1.1 min.
type-check, check:audits, check:desktop-ipc, check:desktop-bridge, and the desktop Vitest suite (931 tests).

vercel · 2026-10-06T06:40:51Z

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waleedlatif1 · 2026-10-06T06:40:53Z

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All reported issues were addressed across 14 files

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All reported issues were addressed across 14 files

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greptile-apps · 2026-10-06T06:44:56Z

Confidence Score: 4/5

[Medium risk] Agent yields page control to user during background work.

The PR’s behavior appears sound, but the new terminal test must satisfy the repository’s testing instruction before merging.

Summary

The PR adds an opt-in desktop sleep blocker for background chat work and makes background browser actions yield when the user is active in the same page. Since the previous review, it also adjusts executor reconnection and terminal-run cleanup. One new test conflicts with the repository’s testing instruction.

Diagram

%%{init: {'theme': 'neutral'}}%%
flowchart LR
  Claim[Background desktop claim] --> Busy[Executor busy state]
  Busy -->|Busy and setting enabled| Block[Hold power blocker]
  Busy -->|Idle or setting disabled| Release[Release power blocker]
  Browser[Background browser action] --> Activity{User active in target tab?}
  Activity -->|Yes| Yield[Wait for quiet period]
  Activity -->|No| Act[Dispatch guarded input]
  Yield -->|Quiet| Act
  Yield -->|Wait limit reached| Refuse[Report not run]

_{Reviews (12) · Last reviewed commit: "fix(desktop): yield the page only for ba..."}

waleedlatif1 · 2026-10-06T15:41:20Z

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waleedlatif1 · 2026-10-06T15:44:13Z

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All reported issues were addressed across 16 files

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waleedlatif1 · 2026-10-06T17:36:53Z

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No issues found across 14 files

Confidence score: 5/5

Automated review surfaced no issues in the provided summaries.
No files require special attention.

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waleedlatif1 · 2026-10-06T21:33:36Z

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No files require special attention.

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waleedlatif1 · 2026-10-06T22:01:58Z

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No issues found across 18 files

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No files require special attention.

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waleedlatif1 · 2026-10-06T22:31:21Z

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No issues found across 18 files

Confidence score: 5/5

Automated review surfaced no issues in the provided summaries.
No files require special attention.

_{Turn on auto-fix | Re-trigger cubic}

…the page to the user - Prevent sleep: while any chat has desktop work claimed on this machine, the app holds a prevent-app-suspension power blocker, released as soon as the last result is delivered. On by default, with a switch in Desktop settings that notes a closed lid still sleeps the computer. The switch is a new optional bridge method, so older shells simply do not show it. - Takeover: when the user clicks, scrolls or types in the page an agent drives, that chat's next browser action waits, marked as needing attention, until the user has left the page alone for a few seconds, then resumes in the same page. A Stop still cancels it while it waits.

- A browser action now rechecks, right before each input it sends, whether the user is working in the page. Between a batch's steps or during a click's target probes, the user wins and the action stops before its next input. - The wait for the user is bounded inside the action's own deadline. A user who keeps working gets the model a clear "not run" instead of a timeout with an unknown outcome. - The user's activity belongs to the tab they acted in. Once the agent drives another tab (the old one closed or replaced, the session reopened), that activity no longer holds anything up. - `createSleepBlocker` is documented.

…e mock was called

- Only a call from the background executor yields the page to the user. A call from the chat view the user is watching acts exactly as before: there the user steers the agent directly. - A background call that only reads the page (snapshot, read text, list tabs) never waits for the user, since it cannot collide with their input. - Which browser tools only observe the page now lives in @sim/browser-protocol, shared by the chat view's replay policy and the driver. - The prevent-sleep switch shows only when Sim runs chats on this device in the background. - Tests: a chat-view call acts at once under user input; a background call waits, and a background read does not; a user who starts working mid-action stops it before its next input; sign-out releases the sleep blocker while a call is still running.

waleedlatif1 · 2026-10-06T22:47:23Z

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cubic-dev-ai

No issues found across 18 files

Confidence score: 5/5

Automated review surfaced no issues in the provided summaries.
No files require special attention.

_{Turn on auto-fix | Re-trigger cubic}

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waleedlatif1 added 4 commits October 6, 2026 15:47

test(desktop): read the blockers the OS holds instead of asserting th…

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