fix(cua-driver-rs)(windows): skip cua-driver-uia spawn at High IL (suppresses AIS error dialog)

[f-trycua]

Summary

Since PR #1630 the autostart task runs the main daemon at `RunLevel=Highest` — full High IL, full UWP UIA access. The sibling `cua-driver-uia.exe` worker is redundant in that mode, and attempting to ShellExecute the unsigned uiAccess'd worker from a High-IL parent pops a Windows AIS error dialog ("A referral was returned from the server" = AIS refusing to elevate unsigned uiAccess).

This patch gates the worker spawn on three conditions:

1. Main daemon NOT already at High IL (PS check via `WindowsPrincipal.IsInRole(Administrator)`)
2. `CUA_DRIVER_RS_SPAWN_UIA_WORKER=1` opt-in env var set
3. Worker binary present on disk

Common case (Highest autostart task per #1630) trips condition 1 → no spawn → no dialog → no regression (High-IL daemon already does what the worker would).

Repro of the dialog

# As a normal admin user (non-RID-500, UAC-split-token):
irm https://raw.githubusercontent.com/trycua/cua/main/libs/cua-driver/scripts/install.ps1 | iex
cua-driver autostart enable    # self-elevates, registers task at Highest
cua-driver autostart kick      # daemon starts at High IL
# ← Windows dialog appears: cua-driver-uia.exe + "A referral was returned from the server"

After this patch: same flow, no dialog. Daemon serves requests, UWP automation works (already verified by the cuademo dogfood for Calculator).

Future EV-cert flow

When the worker is EV-signed and properly elevates to UIAccess, set `CUA_DRIVER_RS_SPAWN_UIA_WORKER=1` to engage it. Default-off keeps the rollout honest — explicit opt-in during the signed-binary transition.

Surfaced

cuademo's fresh-install dogfood right after v0.2.11 — `autostart kick` brought up the daemon and immediately popped the AIS dialog.

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes

  • Windows: Improved daemon process handling with stricter Administrator privilege checks. Worker process spawning now skips when already running at elevated privilege level and requires environment variable opt-in under other scenarios.

• Documentation

  • Updated documentation for Windows daemon behavior regarding worker process spawning and environment variable configuration.

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1 Skipped Deployment

Project	Deployment	Actions	Updated (UTC)
docs	Ignored	Preview	May 21, 2026 4:59pm

[coderabbitai]

Caution

Review failed

The pull request is closed.

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: a729f8ee-7f92-462c-8016-18b55fc0e396

📥 Commits

Reviewing files that changed from the base of the PR and between 46f0203 and b42d9b6.

📒 Files selected for processing (1)

• libs/cua-driver-rs/crates/cua-driver/src/serve.rs

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📝 Walkthrough

Walkthrough

The Windows daemon's UIA worker spawning is now gated by privilege level and environment variable. A new is_self_at_high_il() helper detects Administrator status via PowerShell, and maybe_spawn_uia_worker() skips spawning when already privileged or when the opt-in environment variable is not set.

Changes

UIA Worker Spawning Controls

Layer / File(s)	Summary
UIA worker privilege-level gating libs/cua-driver-rs/crates/cua-driver/src/serve.rs	New is_self_at_high_il() helper checks whether the process runs as Administrator by executing PowerShell and parsing the result. The maybe_spawn_uia_worker() function is enhanced with documentation and gating: it returns early when already at High IL, and otherwise skips by default unless CUA_DRIVER_RS_SPAWN_UIA_WORKER is set to a truthy value. A comment block near the spawn logic is removed.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• trycua/cua#1604: Refines the daemon startup auto-spawning logic for cua-driver-uia.exe that was introduced in #1604, adding privilege-level and environment variable gating to the worker spawning behavior.

Poem

A rabbit guards the daemon's door,
Checking privileges forevermore,
"Are you High IL?" it whispers low,
"Then spawn the UIA worker, go!
(But only if you ask, you know!)" 🐰✨

✨ Finishing Touches

📝 Generate docstrings

• Create stacked PR
• Commit on current branch

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Commit unit tests in branch fix/cua-driver-rs-skip-uia-worker-at-high-il

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