[CI] xcodebuild -downloadPlatform tvOS hangs until test-job timeout

[dalexsoto]

Failure signature

Provision Xcode and dependencies invokes xcodebuild -downloadPlatform tvOS, which then produces no output for more than 2.5 hours and consumes the test job's 180-minute budget.

Stable signature:

Provision Xcode xcodebuild -downloadPlatform tvOS hangs after invocation for over 2.5 hours and exhausts the 180-minute test-job budget

Confirmed occurrences

PR #26527

• Head: 73d2ac20d31eecde56341c51d7d83b2da3c3ab20
• Build 15181280, T: introspection / Provision Xcode and dependencies
• Worker: AcesShared 182
• Xcode 27 beta 6 command: xcodebuild -downloadPlatform tvOS -architectureVariant arm64
• The command produced no output for 9,376 seconds. Provisioning eventually completed after 9,950 seconds, but only eight minutes remained before Azure canceled the job at 180 minutes; introspection did not complete.

PR #26240

• Head: 69ff5adf1625c166175164e1c040e45d2defca35
• Build 15181530, T: framework / Provision Xcode and dependencies
• Worker: AcesShared 90
• Xcode 26.6 command: xcodebuild -downloadPlatform tvOS -architectureVariant universal
• The command produced no output for 10,442 seconds until Azure canceled the job. Tests never started.

First observed: 2026-09-02T07:40:37Z.
Latest confirmed occurrence: 2026-09-02T11:05:24Z.
Recurrence: 2 jobs across 2 distinct monitored PRs.

Classification and impact

This is a CI infrastructure failure in Xcode platform provisioning, not a product/test assertion or API-diff failure. It reproduces with different Xcode versions, architecture variants, workers, PRs, and test jobs. The silent platform-download process consumes the entire job budget and prevents tests from running or completing.

Investigation performed

• Inspected both Azure timelines, task logs, worker assignments, and exact task intervals.
• Calculated the longest timestamp gaps directly from each retained provisioning log.
• Searched all open and closed dotnet/macios issues separately using the exact command, task name, architecture variants, Finding content, and job-timeout symptoms.
• Rejected [CI] iOS 27 monotouch-test stalls in NSUrlSession redirect tests with simulator daemon crash loops #26221 as unrelated: it tracks an iOS runtime test/NSUrlSession stall after tests launch, while these failures occur during Xcode provisioning.

Workaround

Rerun the failed simulator jobs after the run is terminal and retry/merge gates permit it. The durable fix should bound or cancel the xcodebuild -downloadPlatform subprocess independently so one platform discovery cannot consume the full test-job budget.

Azure task logs are retention-limited.

[dalexsoto]

Retry status for PR #26240 @ 69ff5adf1625c166175164e1c040e45d2defca35:

• After refreshing the unchanged conflict-free head, terminal run, complete attempt history, and zero prior retries, Azure accepted build 15181530 simulator_tests attempt 2 with failed-jobs scope.
• Only T: framework is being rerun for this signature; the job is currently pending.
• A separate required request reruns the full Windows Integration stage for the unrelated VSM-XAM-147 heartbeat failure tracked by [CI] Windows Integration loses VSM-XAM-147 agent heartbeat #26534.
• Retry usage is 2 PR-lifetime / 2 current-head requests across both accepted stage requests.

No equivalent retry will be submitted while attempt 2 is active. The issue body has no Additional info to collect checklist.

[dalexsoto]

Terminal retry outcomes for both confirmed provisioning-hang occurrences:

• PR [msbuild] Add AppManifestEntry build items. Fixes #12788 #26240 @ 69ff5adf1625c166175164e1c040e45d2defca35: build 15181530, simulator_tests attempt 2, T: framework succeeded on AcesShared 4 at 2026-09-02T11:39:04Z; the simulator stage succeeded at 11:39:10Z. Its separate full Windows retry remains active.
• PR [xcode27.0] [msbuild] Bump Messaging to get updated dependencies. #26527 @ 73d2ac20d31eecde56341c51d7d83b2da3c3ab20: build 15181280, simulator_tests attempt 2, T: introspection succeeded on AcesShared 16 at 11:26:07Z. Its separate NSUrlSession retry remains active.

The xcodebuild -downloadPlatform tvOS stall did not recur in either rerun. Canonical count remains 2 occurrences across 2 PRs. The issue body has no Additional info to collect checklist.