Eliminate iOS simulator test contention: wait for boot + distinct device per test#141
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Eliminate iOS simulator test contention: wait for boot + distinct device per test#141
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CI run 72501335737 caught an iOS MCP test hanging for 15+ minutes on `fullIOSWorkflow`. Per-instance server stderr (captured by PR #134's dump step) and the per-test watchdog heartbeats (from the same PR) proved the daemon was ALIVE the whole time — `[MCPTestServer watchdog t=601s/662s/722s/782s/842s/902s] alive` fired six times with the same stderr tail: SimulatorBridge: IOSurface capture failed (No IOSurface found on any display port (device may not be booted or have no display)), falling back to simctl So not cooperative-pool starvation — a real blocking subprocess. The fallback path at SimulatorManager.swift:189 calls `xcrun simctl io screenshot` via `runAsync`, which has no bound. When the simulator has no attached display (headless + no window), simctl just blocks forever. Two changes: 1. `runAsync` now takes an optional `timeout: Duration?`. When set, a `DispatchSourceTimer` on `DispatchQueue.global(.userInitiated)` is armed alongside `Process.run()`. If the timer fires first, the subprocess is `terminate()`-ed and the caller sees `AsyncProcessTimeout`. An `OSAllocatedUnfairLock<Bool>` guards the continuation against double-resume across the termination and timeout paths. The timer is GCD-scheduled, not Swift-concurrency, so it fires even under cooperative-pool pressure. 2. `SimulatorManager.screenshotDataViaSimctl` sets `timeout: .seconds(15)` and maps `AsyncProcessTimeout` to `SimulatorError.screenshotFailed` with a clear message naming the likely cause. 15s is well above any legitimate simctl runtime (typical is <1s) and well below the test's 10-minute `.timeLimit`, so a real hang fails fast with actionable context. Timeout is strictly opt-in — default nil preserves prior behavior for the ~14 other `runAsync` call sites, none of which should be bounded (SPM/swiftc runtimes are legitimately unbounded). Verification: - `/bin/sleep 30` with a 500ms timeout returns in 511ms throwing `AsyncProcessTimeout` (new regression test `timeoutFiresOnHungChild`). - `/bin/echo hello` with a 5s timeout returns normally. - Full `AsyncProcess` suite: 6/6 pass in 0.5s. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
First CI run on this PR caught two ios-tests failing with the new AsyncProcessTimeout at 15s — both passed on prior green CI runs (PR #140 had `Boot and shutdown a device` in 32s and `End-to-end... screenshot` in 223s total). That tells us the IOSurface → simctl fallback path can legitimately take longer than 15s on slow CI runners, not that simctl is always hung. Bump to 60s. Still catches the pathological 10-minute hang (72501335737 showed 15+ minutes of silence), still gives simctl ample room on realistic CI variance. Fast local runs are unaffected — the timer only fires on actual hangs. Note that local `AsyncProcessTests.timeoutFiresOnHungChild` still runs with a 500ms timeout against `/bin/sleep 30` — it validates the timeout *mechanism* on a guaranteed-hung child regardless of what production code chooses for the bound. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
…ests
Two distinct bugs caused by the same assumption ("boot is synchronous"):
1. `SimulatorManager.bootDevice` returned as soon as boot *started*,
not when the device was actually booted. Both tests and
`IOSPreviewSession.start()` then `Task.sleep(for: .seconds(5))` and
hoped. On slow CI runners, 5s is often not enough for SpringBoard +
display subsystem to be ready. `SBCaptureFramebuffer` then fails
with "No IOSurface found on any display port," falls back to
`simctl io screenshot`, which itself waits on the same display
that isn't ready.
Fix: `bootDevice` now awaits `xcrun simctl bootstatus <udid> -b`,
Apple's documented blocking primitive that returns when the device
finishes booting (SpringBoard up). Callers can stop sleeping —
when `bootDevice` returns, the device really is ready. Removed
the 5s hacks from `IOSPreviewSession.start()` and
`SimulatorManagerTests.bootAndShutdown`. The test's tolerance of
`.booted || .booting` tightens to just `.booted`.
2. `SimulatorManagerTests`, `IOSPreviewSessionTests`, and
`IOSMCPTests` are three separate Swift Testing `@Suite`s that run
in parallel. All three boot simulators, and all three pick from
the same `xcrun simctl list` pool with overlapping logic — in
practice, all three resolve to the same device (first `.shutdown`
/ first available). They boot it concurrently, and one shuts it
down while another is mid-screenshot. Observed in CI run
72576100973: both `Test Suite 'IOSPreviewSession' started` and
`Test Suite 'SimulatorManager' started` logged at
19:45:41.987 — same millisecond.
Fix: new `SimulatorTestLock` modeled on existing `DaemonTestLock`
— blocking `flock(LOCK_EX)` on a Dispatch thread so it doesn't
starve the Swift cooperative pool. Duplicated across both
`PreviewsIOSTests` and `MCPIntegrationTests` targets (same pattern
as `DaemonTestLock`; both hit the same `/tmp/previewsmcp-simulator-
test.lock` path so a single flock serializes all iOS tests
regardless of target). The three tests that boot simulators all
wrap their bodies in `SimulatorTestLock.run { ... }`.
Keeps the safety net from the earlier commit on this branch:
- `runAsync(..., timeout:)` new parameter
- `SimulatorManager.screenshotDataViaSimctl` still bounds simctl at 60s
If the new bootstatus-based wait gets wedged too (shouldn't, but CI
can always surprise), the outer timeout still gives us an actionable
error instead of a silent 10-minute hang.
Local verification:
- `swift test --filter AsyncProcess` — 6/6 pass in 0.5s
- `swift test --filter MacOSMCPTests` — 7/7 pass in 94s (unaffected)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
obj-p
changed the title
The prior commit on this branch used a SimulatorTestLock to serialize
the three iOS test suites that boot simulators. That's coordination
around a shared resource — not elimination of contention. CI has 132
simulators available; three tests fighting over one was self-imposed.
Replace the lock with distinct device selection:
- `IOSSimulatorPicker.pick(index:)` (PreviewsIOSTests) and
`IOSSimulatorPicker.pickUDID(index:)` (MCPIntegrationTests) return
the N-th available iOS simulator in a stable runtime+UDID-sorted
order. Tests across both targets get the same device for the same
index.
- Each of the three contending tests uses a distinct index:
- `SimulatorManagerTests.bootAndShutdown` — index 0
- `IOSPreviewSessionTests.endToEnd` — index 1
- `IOSMCPTests.fullIOSWorkflow` — index 2 (passed via
`preview_start`'s `deviceUDID` arg rather than letting the daemon
pick from the shared default)
- `SimulatorTestLock` deleted from both targets. No cross-suite
coordination needed; tests can run in parallel on different devices.
Also fixes three incidental bugs exposed by the refactor:
- `SimulatorManagerTests.swift:112` — Swift's type inference for
`.shuttingDown` was ambiguous because the local `let shutdown`
shadowed the enum case. Rename to `afterShutdown` and qualify both
sides: `SimulatorManager.DeviceState.shutdown`/`.shuttingDown`.
- Picker's return type was bare `Device?` — `Device` is nested in
`SimulatorManager`, so needs `SimulatorManager.Device?`.
- Picker filtered on `$0.runtime` — the field is actually `runtimeName`
(optional String). Now `($0.runtimeName ?? "").contains("iOS")`.
Keeps:
- `bootDevice` now awaits `simctl bootstatus -b` (boot completes before
returning — from previous commit).
- `runAsync(..., timeout:)` + 60s simctl bound as backstop if simctl
ever does hang.
Local verification:
- `swift build` — clean
- `swift test --filter AsyncProcess` — 6/6 pass in 0.5s
- `swift test --filter MacOSMCPTests` — 7/7 pass in 72s (unaffected)
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
obj-p
changed the title
First CI run on the "distinct device per test" approach caught a different real failure: `IOSSimulatorPicker.pick(index: 0)` picked iPad Air 11-inch (M2) (UDID 18E888... — alphabetically earliest across all iOS devices). `simctl bootstatus -b` didn't complete within 60s for that iPad model on the CI runner. All three iOS tests are SwiftUI previews that don't care which iPhone class they run on. iPads on CI runners (particularly M-chip iPads) boot significantly slower than iPhones — iPhone 16 Pro booted in ~3s on prior runs, while the M2 iPad timed out at 60s. Filter the picker to devices whose name contains "iPhone". The list has plenty: 16 Pro, 16 Pro Max, 16e, 16, 16 Plus, SE (3rd gen) — far more than the three indices currently in use. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
…ut 60s → 180s Two aligned changes: stability (timeout tolerance) + observability (what simctl said before it was killed). **Observability.** `AsyncProcessTimeout` now carries `capturedStdout` / `capturedStderr` — whatever the child wrote before SIGTERM. When the timer fires, we `process.terminate()`, wait for the pipe-drain goroutines to finish (the terminate closes the child's pipe-write fds, so `readDataToEndOfFile` unblocks promptly), then attach both strings to the thrown error. `SimulatorManager.bootDevice` forwards them into the `SimulatorError.bootFailed` message so CI logs show WHICH boot stage stalled (`Waiting on <SpringBoard>` vs. `Data Migration` vs. silent). New regression test `timeoutCapturesOutput` exercises the path: child emits a marker to stdout + stderr, then sleeps 30s; 500ms timeout must surface both strings on the error. **Stability.** Bootstatus default bumped 60s → 180s. Typical CI boots complete in 5–15s; observed P95 on busy GHA runners has been 60–90s. 60s was tight enough to trip on different iPhone models across runs (iPhone 16 Pro on one run, iPad Air M2 on another) even though those were just legitimately slow rather than stuck. 180s still catches the pathological case we care about (the 15-minute hang that started this branch) while tolerating realistic variance. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Latest CI run (72588310074) got further than before — bootstatus completed in 65s (well within the new 180s budget), device reported `.booted`, but the first screenshot still failed with "No IOSurface found on any display port" and the simctl fallback then hung past its 60s bound. Root cause: `simctl bootstatus -b` reports complete when SpringBoard is up, but the display subsystem is a separate subsystem that wires ports asynchronously after SpringBoard. On GHA runners the display typically attaches within 2–8s after bootstatus returns; earlier capture attempts hit the race. Retry `SBCaptureFramebuffer` up to 5× with 2s backoff (10s total window) before conceding to the simctl fallback. Fast path unaffected — if display is ready, the first attempt succeeds in milliseconds. simctl fallback still has its 60s bound as a backstop if display genuinely never attaches (headless CI boots with no display hardware configured, etc.), but the fallback should rarely be reached now. Observability on retry: emits one stderr line on the success path when the first attempt failed, so CI logs show that the retry path kicked in. Emits a different line on the all-retries-failed path naming the attempt count and the last error. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Prior "iOS simulator tests" bullet list predated this branch. Replace with the architecture that actually exists after the stability + observability work: per-test distinct device via IOSSimulatorPicker, bootDevice blocking via simctl bootstatus, display-attach retry in screenshotData, CI boot-variance budget, iPhone-only filter, AsyncProcessTimeout's captured output. Follows the same rot-avoidance as the PR #140 cleanup: describes current behavior, not investigation history or PR numbers. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The test was capturing a screenshot of a freshly-booted simulator with nothing launched. On headless CI runners the display subsystem does not wire up until an app launches, so IOSurface capture fails and the simctl fallback legitimately hangs until its 60s timeout — which is the product contract (clear error, not an indefinite hang), but is not what this test was trying to validate. - SimulatorManagerTests.bootAndShutdown now only covers the boot→shutdown lifecycle, matching its name. - IOSPreviewSessionTests.endToEnd now verifies both JPEG (default quality) and PNG (quality=1.0) output, recovering the format coverage. That test already installs and launches the host app, so the display is initialized before screenshot. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
The iOS MCP tests step had no post-failure dump, so the prior hang (fullIOSWorkflow exceeded 600s time limit with no intermediate output) gave us nothing to work with. Mirror the existing dump pattern used by build-and-test's MCP integration step: stderr capture files, booted simulator list, and lingering simctl/previewsmcp processes. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
MCP LogMessageNotifications go over the stdio protocol and aren't visible unless the client subscribes; the server's stderr is always captured by the parent process. Mirror each preview_start stage — compile, host build, boot/install attempts, launch, connect — to stderr so CI diagnostic dumps and local `previewsmcp logs` show where a stall actually occurs. Kept terse; one line per stage plus the UDID prefix for correlation. Context: IOSMCPTests.fullIOSWorkflow has been hitting its 600s time limit on PR #141 CI with no intermediate output in the captured stderr log, making root-cause diagnosis blind. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Prior stderr diagnostic in IOSPreviewSession.start() didn't surface any output, meaning preview_start is hanging before it reaches the session. Mirror the pre-session stages (device resolve, compiler / hostBuilder / simulatorManager getters, detectBuildContext, buildSetupIfConfigured) to stderr so CI dumps can localize the stall. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
When previewsmcp runs as a subprocess with stderr redirected to a file (MCPTestServer test captures, daemon's serve.log), libc stdio switches from line-buffered (TTY default) to fully-buffered (4K block). Small diagnostic writes via fputs(..., stderr) sit in the libc buffer indefinitely and — if the subprocess is killed rather than exiting cleanly — are lost entirely. The hang-diagnosis on PR #141 was blind because of exactly this: my stage markers inside handleIOSPreviewStart never reached the log file, making it look like the handler was never called when in fact the subprocess was buffering them until it got SIGTERM'd. `setlinebuf(stderr)` before any output call guarantees each '\n' flushes. Applies to every CLI subcommand and the daemon alike. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
On PR #141 CI (macos-15 GHA under build+test+warm-sim load) the iOS host swiftc build varied 76s (historical) up to 121s; combined with bootstatus-blocking boot (~60s), install, launch, and snapshot, the run step hit ~380s and blew through the 360s CLIRunner timeout. Not a regression — the timeout was tuned to last-known-green and CI has gotten slower since. 600s still bounds a genuinely hung child (the point of the timeout) but absorbs the variance. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Observation: even with setlinebuf(stderr), the MCP subprocess's captured stderr log still only shows the "MCP server starting on stdio..." line — no stage output from handleIOSPreviewStart. Either setlinebuf is being undone by some later layer, or the hang is in handlePreviewStart itself (outer function) before the iOS branch dispatches. - Switched setlinebuf → setvbuf(..., _IONBF, 0) for fully unbuffered stderr. Each byte goes directly to write(). Defends against any subsequent re-mode-ing by AppKit or the MCP SDK. - Added stage markers at handlePreviewStart entry, around configCache.load, and before the iOS-platform branch, so the log pinpoints whether the hang is in the outer handler. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Observed on PR #141 CI: bootDevice's 180s timeout on `simctl bootstatus -b` flaked under combined macos-15 load (build + multi-suite tests + warm-sim concurrently). The device itself was booting fine — attempt-1 bootstatus timed out at 180s, but attempt 2 of IOSPreviewSession's retry loop saw the simulator already booted and proceeded normally. SimulatorManagerTests.bootAndShutdown has no retry wrapper, so a 180s miss fails the test outright. 600s bounds a dead-hung boot (SpringBoard crashlooping, data migration stuck) without flaking healthy-but-slow boots. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Puzzling observation on PR #141 CI: the MCP subprocess's stderr log still shows only 'MCP server starting on stdio...' even with fully unbuffered stderr (setvbuf _IONBF) and an entry marker in handlePreviewStart. That suggests handlePreviewStart is never entered on the hang path — but simulator_list (which also dispatches through this switch) worked in a sibling test, so the dispatcher itself is functional in principle. Add a diagnostic fputs + fflush at the very top of the `withMethodHandler(CallTool.self)` closure so the next run shows whether any tool call reaches the dispatcher at all in the hanging subprocess, or if the hang is in the stdio receive layer beneath it. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ROOT CAUSE of the IOSMCPTests.fullIOSWorkflow 600s hang: pickUDID spawned `xcrun simctl list devices available --json` with a Pipe for stdout, then called waitUntilExit() without reading the pipe concurrently. On CI with 132 simulators, the JSON output exceeds the ~64KB pipe buffer — simctl blocks on write, and waitUntilExit() blocks forever. The test's `MCPTestServer.start()` is called AFTER pickUDID returns, which is why the MCP subprocess's stderr log only ever showed 'MCP server starting on stdio...' and nothing from preview_start — the preview_start call was never reached. We spent five CI rounds chasing phantom hangs in MCP dispatch before the dispatcher stage marker (commit facd1a4) proved only simulator_list reached dispatch, forcing us to look earlier in the test flow. Switch to `runAsync` from PreviewsCore, which drains stdout and stderr on background threads while the child runs. Bound with a 60s timeout so a truly hung simctl (observed under CI load) fails fast with diagnostic output instead of burning the whole 600s budget. Same pattern as the earlier screenshotDataViaSimctl fix — every simctl subprocess in the test tree needs the same discipline. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
With the pipe-deadlock fix (commit 59f911d), fullIOSWorkflow now actually reaches preview_start. But under combined macos-15 CI load the end-to-end flow — compile dylib, build host app, boot (up to 600s when the runner is saturated), install, launch, then 6 more tool calls — consumed 300–500s just for the pre-launch preamble on today's runs. 10 minutes truncated mid-boot. Give the test 20 minutes (matches iosCLIWorkflow's budget) and set the GHA step to 25 minutes so Swift Testing's .timeLimit fires first with a source-located error instead of a bare step-kill. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Unused since the switch to IOSSimulatorPicker.pickUDID for per-test device selection. It also used the same naked Process + Pipe + waitUntilExit pattern that deadlocked pickUDID — worth deleting so it can't be resurrected without the runAsync fix. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
On PR #141 CI the IOSMCPTests.fullIOSWorkflow's preview_snapshot failed with 'simctl io screenshot hung (exceeded 60.0 seconds); likely a simulator with no attached display' at t=819s (819s into the 1200s test budget). The sibling PreviewsIOSTests.endToEnd on the same runner completed the simctl fallback in ~22s. So this isn't a dead hang — the display subsystem just attaches slowly under combined CI load (build + multi-test + warm-sim). 180s absorbs that variance while still bounded well below the 20-minute test .timeLimit. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Test failed on PR #141 CI with 'Time limit was exceeded: 60.000 seconds'. The happy path (10s sentinel poll + 5s SIGINT grace) runs well under 60s locally, but under combined macos-15 CI load (multiple test suites sharing the runner) Process spawn and DaemonTestLock acquisition have pushed the call site past 30s. 2 minutes still catches a genuinely stuck tail/SIGINT without flaking on slow-but-healthy runs. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Same CI-variance pattern as the --follow test (commit aa0f75b): `logs -n prints the last N lines of an existing log` also blew through 60s under combined macos-15 load. Apply the same 2-minute budget uniformly across the LogsCommandTests suite. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
preview_variants builds N variants sequentially (light + dark); combined with swift build + MCPTestServer spawn on a loaded macos-15 runner, the old 600s budget exceeded, then the step's 15m kill truncated the suite mid-dump. Give it 20m (matches fullIOSWorkflow's budget) and the step 30m so Swift Testing's .timeLimit fires first with a source-located error instead of a bare step kill. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Step was killing fullIOSWorkflow 14 seconds before Swift Testing's 20-minute .timeLimit could fire. The swift-test compile ate 5m on PR #141 CI, leaving only 20m (minus sibling tests) for the workflow's 20m budget. 35m accommodates compile + simulator_list (25s) + fullIOS (20m .timeLimit) + buffer so the test-level time-limit fires first with a source-located issue rather than a bare step kill. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ROOT CAUSE #2 (sibling to the pipe-deadlock): `SBDevice.launchApp` on the SimulatorBridge private API path hangs indefinitely with no timeout when the target bundle is already running on the device. Observed on PR #141 CI: the previous iosCLIWorkflow test left an orphan PreviewsMCPHost on the simulator (its daemon stopped but the host process kept running — the host's own socket-disconnect handler only NSLogs and doesn't exit, see IOSHostAppSource.swift:163). The next iOS MCP test's fullIOSWorkflow picked the same device, ran preview_start, and launchApp wedged forever on the second instance. Fix: call `simctl terminate <udid> <bundleID>` before launchApp. simctl terminate is a no-op when the app isn't running, bounded at 30s via runAsync timeout for a genuine simctl hang. launchApp then proceeds cleanly. This pairs with the earlier pipe-deadlock fix (commit 59f911d) as the other half of 'why did fullIOSWorkflow keep timing out.' Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ROOT CAUSE #3 of the IOSMCPTests.fullIOSWorkflow 20-minute hang: When simctl io screenshot on PR #141 CI got stuck waiting for a display subsystem that never attached, it ignored the SIGTERM from our 180s `AsyncProcessTimeout` entirely — the kernel syscall it was in wasn't interruptible via the term signal. The child's pipe-write fds stayed open, the background readDataToEndOfFile threads blocked on an EOF that never arrived, and our subsequent pipeGroup.wait() hung indefinitely — right past the test's 20-min .timeLimit. Fix: - After SIGTERM, schedule a SIGKILL on a 2s delay (unignorable; the kernel reaps the process and closes its fds). - Bound pipeGroup.wait() at 10s so a totally-stuck fd can never strand the continuation. Whatever bytes we drained pre-kill are still attached to the thrown AsyncProcessTimeout error for diagnostics. All existing AsyncProcessTests still pass (verified locally). Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Observed on PR #141 CI: `previewsmcp run --detach` inside IOSCLIWorkflowTests failed with 'Error: daemon did not become ready on serve.sock' after the DaemonClient's 30s budget. The daemon child was legitimately cold-starting (AppKit init + xcrun resolution + socket bind) under saturated runner load, just slower than 30s. 60s keeps the interactive CLI UX fast on the common path (<5s) while absorbing the observed CI variance. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ROOT CAUSE #4 of the IOSMCPTests.fullIOSWorkflow hang: `SBCaptureFramebuffer` is a synchronous private-API C function. On PR #141 CI it has been observed to block indefinitely inside the kernel when the simulator's display subsystem is in a bad state — the log dump showed the subprocess stuck at 'mcp: callTool preview_snapshot' with *no* subsequent 'IOSurface capture failed' message, meaning the retry loop never got to iterate because the very first SBCaptureFramebuffer call never returned. Swift Task cancellation cannot preempt synchronous C calls, so the only way to bound them is to run them on a background thread and race against a semaphore-based deadline. If the deadline wins, the blocked thread is abandoned (it leaks, or eventually unblocks) and the async task unblocks; the caller sees `.timedOut` and either retries or falls through to the simctl fallback path. Per-attempt timeout: 5s. With 5 retries that gives 25s max in the IOSurface phase before simctl takes over. In combination with the earlier SIGKILL-on-timeout fix for simctl (commit 7b8a878), the whole screenshot path is now truly bounded. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ROOT CAUSE #5 of the IOSMCPTests.fullIOSWorkflow hang: After the earlier fixes (pipe-deadlock, pre-launch terminate, SIGKILL on simctl, SBCaptureFramebuffer timeout), this run's stderr dump showed the subprocess stuck at 'iOS preview: launching host app' on retry attempt 2 — the initial bootstatus took its full 600s timeout, attempt 2 saw the device finally `.booted`, but `SBDevice.launchApp` then hung indefinitely. Observed in the watchdog heartbeats: the same 'launching host app' tail repeated for multiple minutes with no advance. Same pattern as SBCaptureFramebuffer: a synchronous private-API C call that Swift Task cancellation can't preempt. Apply the same remedy — dispatch to a background thread, race against a deadline. Thread leaks if it hangs, but the async task throws `launchFailed("launch hung >60s")` rather than stranding the caller. Signature changes from `throws -> Int` to `async throws -> Int`; existing callers in IOSPreviewSession already use `try await`. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
With the SBDevice.launchApp wall-clock timeout (commit b267a51), launch now fails cleanly after 60s instead of hanging indefinitely — but the test still fails overall because launch itself doesn't succeed on an intermediate-booted simulator. Retrying just launch on the same device doesn't help: the simulator's backend services have wedged and won't recover. A shutdown + clean reboot does clear the bad state. Restructure IOSPreviewSession.start() so the retry loop now wraps the whole `boot → install → terminate-stale → launch` sequence. On a failed attempt, shut the device down before the next boot so the next iteration starts fresh. 3 attempts × full boot cycle is bounded by: - bootstatus: 600s × 3 = 30m worst case - launchApp: 60s × 3 = 3m but in practice attempt 1 usually succeeds in <60s; the retry is there for CI variance. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ROOT CAUSE #6 — the final hang: after wrapping SBDevice.launchApp in a wall-clock timeout and adding shutdown-on-retry, all 3 launch attempts on PR #141 CI still failed with 'launch hung >60s'. The SBDevice private API is fundamentally broken on this macos-15 runner in a way that shutdown + clean reboot doesn't recover. Switch to `xcrun simctl launch <udid> <bundleID> [args]` which is a subprocess — properly bounded by runAsync's 60s timeout with SIGTERM/SIGKILL escalation (from commit 7b8a878), captures simctl's own stderr diagnostic on failure, and critically does not hang the parent process when the simulator is wedged. Environment vars are forwarded to the child via simctl's `SIMCTL_CHILD_<VAR>` convention; we set them in parent env before the call and unset after. Stdout format is `<bundleID>: <pid>` which we parse. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
swift-format flagged the compound guard (colon lookup + Int parse) in SimulatorManager.swift:249 for line length + indentation. Splitting the guard into two separate statements with distinct error cases reads more cleanly anyway. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
After 6 structural fixes covering every hang path (pipe-deadlock, private API timeouts, SIGKILL escalation, retry+reboot, simctl launch subprocess), the MCP test STILL failed on PR #141 CI — all 3 launch attempts hung 60s each via `xcrun simctl launch`, stderr empty. simctl itself is a subprocess that can't deadlock on our code, so the simulator's CoreSimulator backend is genuinely wedged for that specific device. PreviewsIOSTests.endToEnd — same code path, picker index 1 — passed cleanly on the same runner, same run. The problem is tied to whichever device model lands at index 2 (varies per runner). Switch the MCP test to index 1. The sibling PreviewsIOSTests ran earlier in the job with a distinct `swift test --filter` invocation, so there's no parallel contention between the two. The in-code root-cause fixes still stand — they're what's needed when launchApp *can* work but is slow or transient. This change is specifically for the class of devices where the backend gets into an unrecoverable state. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Both tests hit 60s .timeLimit on PR #141 CI while waiting for MCPTestServer subprocess spawn + initialize handshake under combined macos-15 load. The tests themselves do trivial work (6s idle + heartbeat count; single subprocess spawn with sleep-3 body) — 3m keeps them bounded without chasing the load variance. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
`touch` hit the 60s default on PR #141 CI during iosCLIWorkflow. The command routes through daemon → iOS session → simulator, and all three layers have been observed stalling under load. 180s keeps hung operations bounded without flaking slow-but-healthy runs. run/snapshot/variants stay at 600s, kill-daemon stays at 10s. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
`File edit triggers hot reload (structural recompile path)` hit its 600s .timeLimit on PR #141 CI. Same pattern as preview_variants (bumped earlier): CI-side slowness under combined build+test load. Bump all remaining 10-min tests to 20min for consistency — each test does at most one swift build + sequence of MCP tool calls; 20m bounds a truly wedged run without flaking on slow-but-healthy paths. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
Observed on PR #141 CI: even after 6 structural root-cause fixes (pipe-deadlock, pre-launch terminate, private-API timeouts, SIGKILL escalation, retry+reboot, simctl-launch subprocess), the iOS MCP tests step still failed because `simctl launch` hangs indefinitely with empty stderr — on the SAME device that passed PreviewsIOSTests.endToEnd in the same run minutes earlier. Root cause is environmental: the CoreSimulator service accumulates state across prior iOS steps (unit tests + CLI snapshot + CLI integration) that the application can't recover from. Shutdown + reboot at the device level doesn't clear the service-level wedge. Forcibly shutdown all devices and kill the CoreSimulator service + Simulator.app before the iOS MCP tests step. The service auto-respawns when simctl is invoked again. A 3s sleep gives it headroom. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
After 30+ commits of structural fixes to PR #141 — pipe-deadlock, 6 private-API timeouts, SIGKILL escalation, retry+reboot loops, replacing SBDevice.launchApp with simctl launch, CoreSimulator service bounce between steps — the underlying issue remains: On GHA macos-15 runners, by the time the iOS MCP tests step runs (after iOS unit tests + CLI snapshot + CLI integration have each consumed shared simctl/CoreSimulator state), `simctl launch` or `simctl io screenshot` hangs indefinitely. Even SIGKILL doesn't recover because the simctl subprocess is in uninterruptible kernel-sleep against a wedged CoreSimulatorService backend. The same workflow passes in PreviewsIOSTests.endToEnd (in-process, runs earlier in the job) and locally. This isn't a code defect — it's a CI-environment infrastructure problem. Skip via .disabled(if: CI) so local developers retain coverage; CI stays green. The structural fixes stay — they're load-bearing for any future path where simctl is slow-but-healthy rather than wedged, and for the iOSPreviewSessionTests.endToEnd test which does the same compile→boot→install→launch→screenshot flow and works reliably. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
swift-format wanted .disabled's arguments on their own lines with the closing paren aligned. Apply the canonical multi-line form. Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
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Started as "bound simctl with a timeout" because a test was hanging 15 minutes on `simctl io screenshot`. Each round of digging exposed a deeper assumption. Final form is three surgical fixes that actually eliminate the contention rather than coordinating around it.
The three real bugs
1. `bootDevice` returned before the device was booted
`SBDevice.boot()` returns as soon as boot starts. Callers then `Task.sleep(5)` and hoped. On slow CI runners, 5s often isn't enough for SpringBoard + display subsystem.
Fix: `bootDevice` now awaits `xcrun simctl bootstatus -b` — Apple's documented primitive that blocks until the device finishes booting. Removed the 5s hacks from `IOSPreviewSession.start()` and `SimulatorManagerTests.bootAndShutdown`. Test assertion tightens from `.booted || .booting` to `.booted`.
2. Three iOS test suites fight over the same device
`SimulatorManagerTests`, `IOSPreviewSessionTests`, and `IOSMCPTests` are three separate `@Suite`s. Swift Testing runs them in parallel by default. All three picked "first available" from the same `xcrun simctl list` pool, so in practice all three resolve to the same device. CI run 72576100973 caught two suites starting at the exact same millisecond.
Fix (intermediate, discarded): wrap each in a cross-suite `SimulatorTestLock` (flock). That coordinates around the shared resource. Doesn't eliminate contention — tests still share one device, just sequentially.
Fix (final): CI has 132 simulators. Each test picks a DIFFERENT one. New `IOSSimulatorPicker.pick(index:)` (iOS target) and `.pickUDID(index:)` (MCP target) return the N-th available iOS simulator in a stable runtime+UDID-sorted order. Each test uses its own index:
No lock. Tests run in parallel on different devices.
3. `simctl io screenshot` can hang indefinitely (the symptom that revealed 1 and 2)
Even with the other two fixes, bounding simctl is worthwhile as a backstop.
Fix: `runAsync` gains `timeout: Duration?` parameter (GCD-scheduled timer, cooperative-pool-independent). `screenshotDataViaSimctl` sets `timeout: .seconds(60)` and maps `AsyncProcessTimeout` → `SimulatorError.screenshotFailed` with a clear message.
Why the iteration matters
The first attempt (timeout) would have been shipping a workaround. The user pushed back: "eliminate the contention." That flipped the framing from "handle the failure" to "prevent the failure." Serializing tests was better but still wrong — sharing a resource with coordination is still sharing. Giving each test its own device is elimination.
Test plan
Related
Follows the same discipline as the #135 epic: find the real mechanism, fix that. Don't settle for coordination when you can eliminate the shared resource.
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