[CI] PowerShell startup fails in procargs (errno 5) before scripts on macOS #27119

Apple platform

macOS (CI PowerShell host, not an application test assertion).

Framework version

Other: PowerShell host initialization. No application target framework or selected test SDK is established by these unstarted scripts.

Affected platform version

mac14/x64 Sonoma CI lane. A clock-matched older process report identifies macOS 14.8.9; the current OS patch and PowerShell binary version are not independently established. The current Azure PowerShell task version is 2.281.0, not the PowerShell binary version.

Description

Two independently source-bound tasks across two monitored PRs fail before their PowerShell script bodies execute with the same normalized startup stack:

procargs errno 5 -> ManagedPSEntry.StartupException -> ThrowOnFailure -> AttemptExecPwshLogin.

Classification: CI infrastructure / PowerShell host startup failure. The pre-test and post-test caller phases remain distinct; neither task title establishes a failure inside a disk-usage or directory-removal script. Azure reports the PowerShell exit code as literal null, not 0 or 1. This is not a product test failure, and genuine flakiness or the exclusive physical initiator is not established.

There are two physical task occurrences / two PRs. Two older durable ledger keys refer to the same #27030 task, log and original log hash; they are retained as aliases and counted once, not as a third failure. No old key or charge was deleted or rekeyed.

Four complete open-and-closed issue searches covered the syscall/error, exact exception, task and component. The only candidate, #7305, documents an unrelated 2019 Visual Studio SSH/build-disconnection problem; its full body and non-ignored history do not contain this startup signature. No existing issue was broadened or reopened.

Steps to Reproduce

No deterministic standalone reproduction is available. The two linked CI tasks capture PowerShell failing during host initialization before either script body starts. Their own source resets and exact task identities were verified; repeated template GUIDs in other runs are not additional occurrences.

Did you find any workaround?

No validated workaround or startup-task recovery is established. On #27103, an earlier Run-tests task succeeded before this warning; that does not make the later cleanup script successful. No CI retry, source change, approval, worker probe/reset/repair, credential or security-policy change was performed by the monitor.

Relevant log output

Call to 'procargs' failed with errno 5
Unhandled exception. Microsoft.PowerShell.ManagedPSEntry+StartupException
  at Microsoft.PowerShell.ManagedPSEntry.ThrowOnFailure(...)
  at Microsoft.PowerShell.ManagedPSEntry.AttemptExecPwshLogin(...)
PowerShell exited with code 'null'.

The affected run's own mac14 CrashReports archive contains an older pwsh incident at 2026-10-26 18:07:23.722800 UTC, inside the first task's exact interval, with the source-host association checked privately. It records EXC_CRASH / SIGABRT on macOS 14.8.9. This is bounded evidence for that historical occurrence, not proof of the underlying procargs initiator or a crash belonging to the current failure.

For the current #27103 occurrence, the own crash collector ended 12:02:24.4133333 UTC, before the startup task began 12:02:33.910 UTC. That archive therefore cannot establish a post-failure crash report for the current task. A separate older PowerShell incident in the archive is not added as a monitored occurrence.

Historical raw task logs are no longer retained after authorized cleanup; the earlier verified structured timeline/source/hash evidence remains retained. Original NUnit/TRX, Helix and build-binlog results do not apply to these unstarted scripts. An attributable current native blocked stack and the exclusive procargs failure cause remain unavailable. Raw invocations, environment, credentials, worker identities, addresses and crash payloads are not published. Azure diagnostics are retention-limited.