[CI] iOS 16 simulator runtime downloads fail with connection reset by peer

[dalexsoto]

Failure signature

During Provision system dependencies, the required iOS 16.0 simulator is unavailable through xcodebuild, so provisioning falls back to Apple's downloadable simulator index. The runtime download then fails with:

curl: (56) Recv failure: Connection reset by peer
Failed to download the iOS 16.0 simulator runtime.
The iOS 16.0 simulator is not installed, and it couldn't be downloaded.

Confirmed occurrences

PR / head	Build attempt / job	Worker
#26274 / c6514d837dbf5f878369ed1176979040e1d2ab93	14753211 attempt 1 - dotnettests_ios / Provision system dependencies	AcesShared 61
#26274 / c6514d837dbf5f878369ed1176979040e1d2ab93	14753211 attempt 1 - monotouch_maccatalyst / Provision system dependencies	AcesShared 73
#26279 / 84d989d3c2e6b0423d061fa59431d104157c895d	14753669 attempt 1 - interdependent-binding-projects / Provision system dependencies	AcesShared 103

Total: 3 jobs across 2 distinct monitored PRs.

First observed: 2026-07-24 00:07 UTC. Latest observed: 2026-07-24 01:04 UTC.

Classification and impact

This is a CI infrastructure/network failure, not a source build or test failure:

• It reproduces on unrelated PRs and three different workers.
• The failure occurs before repository tests start.
• Later missing TestSummary, HtmlReport, and drop artifacts are cascading errors caused by provisioning not completing.

Investigation performed

• Inspected each Azure timeline and selected the first failed task in each job.
• Verified the exact simulator asset and normalized curl error in the provisioning task logs.
• Searched all open and closed dotnet/macios issues using the exact exception, simulator runtime name, task name, and downloadable-index fallback; no matching issue existed.
• Kept this separate from Xcode archive transport failures because the affected asset and provisioning phase differ.

Retry status and workaround

Both affected builds are still active, so no retry has been submitted. Once each run is terminal, refresh the PR head and mergeability, reconcile retry budgets, confirm no equivalent attempt is active, then rerun failed jobs.

Azure task logs have limited retention.

[dalexsoto]

Retry update for #26274 @ c6514d837dbf5f878369ed1176979040e1d2ab93: build 14753211 simulator_tests attempt 2 was accepted using failed-jobs semantics. It is rerunning the two iOS 16 simulator connection-reset jobs (dotnettests_ios and monotouch_maccatalyst) together with the separately classified linker_ios launch failure.

Retry budget usage: 1 lifetime / 1 current-head request. The recurrence count remains 3 jobs across 2 monitored PRs.

[dalexsoto]

Retry outcomes for the iOS 16 simulator download-reset signature:

• [SafariServices] Update bindings up to Xcode 27.0 Beta 3 #26274 @ c6514d837dbf5f878369ed1176979040e1d2ab93: build 14753211 attempt 2 passed both affected jobs (dotnettests_ios and monotouch_maccatalyst). The independent linker_ios launch failure reproduced and is now rerunning alone in attempt 3. Budget: 2 lifetime/current-head requests.
• [CoreSpotlight] Update bindings up to Xcode 27.0 Beta 4 #26279 @ 84d989d3c2e6b0423d061fa59431d104157c895d: build 14753669 attempt 2 was accepted and is rerunning interdependent-binding-projects together with the separately classified monotouch_ios failures. Budget: 1 lifetime/current-head request.

The recurrence count remains 3 jobs across 2 monitored PRs.

[dalexsoto]

New simulator-runtime connection-reset occurrence on #26283 @ 7c632842dbc9d22d3f4c8f584d4273453ebcdff1: build 14755388 attempt 1 — msbuild / Provision system dependencies on AcesShared 46.

This occurrence is the tvOS 16.0 runtime rather than iOS 16.0, but uses the same fallback downloadable-index path and terminates with the identical stable transport signature:

curl: (56) Recv failure: Connection reset by peer
Failed to download the tvOS 16.0 simulator runtime.

The generalized Apple simulator-runtime signature now covers 4 jobs across 3 monitored PRs. Build 14755388 remains active, so no retry has been submitted yet.

[dalexsoto]

Retry update for #26283 @ 7c632842dbc9d22d3f4c8f584d4273453ebcdff1: build 14755388 simulator_tests attempt 2 was accepted using failed-jobs semantics. It is rerunning the tvOS 16 runtime-reset-affected msbuild job together with the two jobs canceled by attempt 1 (framework and monotouch_ios). Retry budget usage: 1 lifetime / 1 current head. The generalized simulator-runtime connection-reset count remains 4 jobs across 3 monitored PRs.

[dalexsoto]

New occurrence on #26280 @ 0a02e7f9 — and the first recorded tvOS 16.0 variant of this signature (previous occurrences were all iOS 16.0):

PR / head	Build attempt / job	Runtime	Worker
#26280 / 0a02e7f9	14779562 attempt 1 — T: introspection / Provision system dependencies	tvOS 16.0	AcesShared 70

Same task and same normalized error, with the identical xcodebuild → downloadable-index fallback path:

tvOS 16.0 is not available for download.
Failed to install the tvOS 16.0 simulator using xcodebuild; falling back to Apple's downloadable simulator index...
    Downloading the tvOS 16.0 simulator runtime from https://download.developer.apple.com/Developer_Tools/tvOS_16_Simulator_Runtime/tvOS_16_Simulator_Runtime.dmg...
curl: (56) Recv failure: Connection reset by peer
    Failed to download the tvOS 16.0 simulator runtime.
    The tvOS 16.0 simulator is not installed, and it couldn't be downloaded.
System check failed

Worth noting for diagnosis: the iOS 16.0 runtime downloaded and installed successfully on this same worker moments earlier (23:09:25 → 23:12:17, FB40208E-… iOS (16.0 - 20A360) (Ready)), and the tvOS transfer was reset after only 17 seconds (23:12:19 → 23:12:36). So this is not sustained worker-wide loss of connectivity to Apple's CDN, and it is not the slow/stalled-transfer profile — it is an early per-connection reset.

That 17-second reset is what distinguishes this from #26223, which records the same curl: (56) family but with the different normalized error Recv failure: Operation timed out after 11-12 minutes. Neither issue references the other as a duplicate, and the exact error string here matches this issue, so it is recorded here.

Classification: CI infrastructure/network failure. The job never reached introspection test execution, and #26280 only changes ScreenCaptureKit bindings.

Retry: none submitted — build 14779562 is still in progress, so it is not yet terminal and no retry is permitted. Retry accounting for #26280 remains 2 lifetime / 0 current-head requests. This will continue to be monitored to a terminal state.

Issue-specific diagnostic checklist: none — this issue has no Additional info to collect section.