callstack · thymikee · Jun 28, 2026
diff --git a/ios-runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Models.swift b/ios-runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Models.swift
@@ -207,6 +207,7 @@ struct DataPayload: Codable {
   let nodes: [SnapshotNode]?
   let truncated: Bool?
   let snapshotQuality: SnapshotQuality?
+  var snapshotTiming: SnapshotTiming?
   let gestureStartUptimeMs: Double?
   let gestureEndUptimeMs: Double?
   let x: Double?
@@ -245,6 +246,7 @@ struct DataPayload: Codable {
     nodes: [SnapshotNode]? = nil,
     truncated: Bool? = nil,
     snapshotQuality: SnapshotQuality? = nil,
+    snapshotTiming: SnapshotTiming? = nil,
     gestureStartUptimeMs: Double? = nil,
     gestureEndUptimeMs: Double? = nil,
     x: Double? = nil,
@@ -282,6 +284,7 @@ struct DataPayload: Codable {
     self.nodes = nodes
     self.truncated = truncated
     self.snapshotQuality = snapshotQuality
+    self.snapshotTiming = snapshotTiming
     self.gestureStartUptimeMs = gestureStartUptimeMs
     self.gestureEndUptimeMs = gestureEndUptimeMs
     self.x = x
@@ -314,6 +317,13 @@ struct DataPayload: Codable {
   }
 }
 
+struct SnapshotTiming: Codable {
+  let totalMs: Double
+  let phases: [String: Double]?
+  let backends: [String: Double]?
+  let selectedBackend: String?
+}
+
 struct ErrorPayload: Codable {
   let code: String?
   let message: String

diff --git a/ios-runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Snapshot.swift b/ios-runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Snapshot.swift
@@ -102,15 +102,21 @@ extension RunnerTests {
   private static let flatInteractiveFallbackBudget: TimeInterval = 1.0
 
   func snapshotFast(app: XCUIApplication, options: SnapshotOptions) throws -> DataPayload {
+    let timing = SnapshotTimingRecorder()
     if let blocking = blockingSystemAlertSnapshot() {
-      return blocking
+      var payload = blocking
+      payload.snapshotTiming = timing.payload()
+      return payload
     }
-    return try runSnapshotCapturePlan(
+    var payload = try runSnapshotCapturePlan(
       Self.regularVisiblePlan,
       app: app,
       options: options,
-      terminal: .sparseWithFatalOnAXFailure
+      terminal: .sparseWithFatalOnAXFailure,
+      timing: timing
     )
+    payload.snapshotTiming = timing.payload()
+    return payload
   }
 
   func recursiveTreeSnapshotPayload(
@@ -246,15 +252,21 @@ extension RunnerTests {
   }
 
   func snapshotRaw(app: XCUIApplication, options: SnapshotOptions) throws -> DataPayload {
+    let timing = SnapshotTimingRecorder()
     if let blocking = blockingSystemAlertSnapshot() {
-      return blocking
+      var payload = blocking
+      payload.snapshotTiming = timing.payload()
+      return payload
     }
-    return try runSnapshotCapturePlan(
+    var payload = try runSnapshotCapturePlan(
       Self.rawDiagnosticPlan,
       app: app,
       options: options,
-      terminal: .throwOnAXFailure
+      terminal: .throwOnAXFailure,
+      timing: timing
     )
+    payload.snapshotTiming = timing.payload()
+    return payload
   }
 
   func rawTreeSnapshotPayload(
@@ -302,7 +314,11 @@ extension RunnerTests {
     return DataPayload(nodes: nodes, truncated: false)
   }
 
-  func snapshotFlatInteractive(app: XCUIApplication, options: SnapshotOptions) -> DataPayload {
+  func snapshotFlatInteractive(
+    app: XCUIApplication,
+    options: SnapshotOptions,
+    timing: SnapshotTimingRecorder? = nil
+  ) -> DataPayload {
     var nodes: [SnapshotNode] = [
       interactiveRootNode(rect: .zero)
     ]
@@ -313,39 +329,45 @@ extension RunnerTests {
     let deadline = options.interactiveOnly
       ? Date().addingTimeInterval(Self.flatInteractiveFallbackBudget)
       : Date.distantFuture
-    let viewport = safeSnapshotViewport(app: app)
+    let viewport = measureSnapshotPhase(timing, "query_sweep_viewport") {
+      safeSnapshotViewport(app: app)
+    }
     var seen = Set<String>()
     var candidates: [SnapshotNode] = []
-    let flatElements = flatInteractiveElements(app: app, deadline: deadline)
-    var truncated = flatElements.truncated
-    for element in flatElements.elements {
-      if Date() >= deadline {
-        NSLog("AGENT_DEVICE_RUNNER_SNAPSHOT_FLAT_FALLBACK_DEADLINE")
-        truncated = true
-        break
-      }
-      guard let node = flatSnapshotNode(
-        element: element,
-        index: 0,
-        parentIndex: 0,
-        viewport: viewport,
-        options: options
-      ) else {
-        continue
-      }
-      let key = "\(node.type)-\(node.label ?? "")-\(node.identifier ?? "")-\(node.value ?? "")-\(node.rect.x)-\(node.rect.y)-\(node.rect.width)-\(node.rect.height)"
-      if seen.contains(key) { continue }
-      seen.insert(key)
-      candidates.append(node)
+    let flatElements = measureSnapshotPhase(timing, "query_sweep_elements") {
+      flatInteractiveElements(app: app, deadline: deadline)
     }
-    candidates.sort { left, right in
-      if left.rect.y != right.rect.y {
-        return left.rect.y < right.rect.y
+    var truncated = flatElements.truncated
+    measureSnapshotPhase(timing, "query_sweep_shape") {
+      for element in flatElements.elements {
+        if Date() >= deadline {
+          NSLog("AGENT_DEVICE_RUNNER_SNAPSHOT_FLAT_FALLBACK_DEADLINE")
+          truncated = true
+          break
+        }
+        guard let node = flatSnapshotNode(
+          element: element,
+          index: 0,
+          parentIndex: 0,
+          viewport: viewport,
+          options: options
+        ) else {
+          continue
+        }
+        let key = "\(node.type)-\(node.label ?? "")-\(node.identifier ?? "")-\(node.value ?? "")-\(node.rect.x)-\(node.rect.y)-\(node.rect.width)-\(node.rect.height)"
+        if seen.contains(key) { continue }
+        seen.insert(key)
+        candidates.append(node)
       }
-      if left.rect.x != right.rect.x {
-        return left.rect.x < right.rect.x
+      candidates.sort { left, right in
+        if left.rect.y != right.rect.y {
+          return left.rect.y < right.rect.y
+        }
+        if left.rect.x != right.rect.x {
+          return left.rect.x < right.rect.x
+        }
+        return left.type < right.type
       }
-      return left.type < right.type
     }
 
     // The synthetic root doubles as the daemon's viewport (find.ts prefers on-screen matches
@@ -560,16 +582,26 @@ extension RunnerTests {
 
   func makeSnapshotTraversalContext(
     app: XCUIApplication,
-    options: SnapshotOptions
+    options: SnapshotOptions,
+    timing: SnapshotTimingRecorder? = nil
   ) throws -> SnapshotTraversalContext? {
-    let viewport = safeSnapshotViewport(app: app)
-    let queryRoot = options.scope.flatMap { findScopeElement(app: app, scope: $0) } ?? app
+    let viewport = measureSnapshotPhase(timing, "viewport") {
+      safeSnapshotViewport(app: app)
+    }
+    let queryRoot = measureSnapshotPhase(timing, "scope_resolve") {
+      options.scope.flatMap { findScopeElement(app: app, scope: $0) } ?? app
+    }
 
-    guard let rootSnapshot = try captureSnapshotRoot(queryRoot) else {
+    let maybeRootSnapshot = try measureSnapshotPhase(timing, "xctest_root_snapshot") {
+      try captureSnapshotRoot(queryRoot)
+    }
+    guard let rootSnapshot = maybeRootSnapshot else {
       return nil
     }
 
-    let (flatSnapshots, snapshotRanges) = flattenedSnapshots(rootSnapshot)
+    let (flatSnapshots, snapshotRanges) = measureSnapshotPhase(timing, "flatten_tree") {
+      flattenedSnapshots(rootSnapshot)
+    }
     return SnapshotTraversalContext(
       queryRoot: queryRoot,
       rootSnapshot: rootSnapshot,

diff --git a/ios-runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+SnapshotCapturePlan.swift b/ios-runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+SnapshotCapturePlan.swift
@@ -46,6 +46,69 @@ struct SnapshotBackendCapture {
   let effectiveDepth: Int?
 }
 
+final class SnapshotTimingRecorder {
+  private let startedAt = Date()
+  private(set) var phases: [String: Double] = [:]
+  private(set) var backends: [String: Double] = [:]
+  private var selectedBackend: SnapshotBackendKind?
+
+  @discardableResult
+  func measure<T>(_ phase: String, _ work: () throws -> T) rethrows -> T {
+    let started = Date()
+    defer { phases[phase] = roundedElapsedMs(since: started) }
+    return try work()
+  }
+
+  @discardableResult
+  func measureBackend<T>(_ backend: SnapshotBackendKind, _ work: () throws -> T) rethrows -> T {
+    let started = Date()
+    defer { backends[backend.rawValue] = roundedElapsedMs(since: started) }
+    return try work()
+  }
+
+  func selectBackend(_ backend: SnapshotBackendKind) {
+    selectedBackend = backend
+  }
+
+  func payload() -> SnapshotTiming {
+    SnapshotTiming(
+      totalMs: roundedElapsedMs(since: startedAt),
+      phases: phases.isEmpty ? nil : phases,
+      backends: backends.isEmpty ? nil : backends,
+      selectedBackend: selectedBackend?.rawValue
+    )
+  }
+
+  private func roundedElapsedMs(since started: Date) -> Double {
+    let elapsed = Date().timeIntervalSince(started) * 1000
+    return (elapsed * 10).rounded() / 10
+  }
+}
+
+@discardableResult
+func measureSnapshotPhase<T>(
+  _ timing: SnapshotTimingRecorder?,
+  _ phase: String,
+  _ work: () throws -> T
+) rethrows -> T {
+  if let timing {
+    return try timing.measure(phase, work)
+  }
+  return try work()
+}
+
+@discardableResult
+func measureSnapshotBackend<T>(
+  _ timing: SnapshotTimingRecorder?,
+  _ backend: SnapshotBackendKind,
+  _ work: () throws -> T
+) rethrows -> T {
+  if let timing {
+    return try timing.measureBackend(backend, work)
+  }
+  return try work()
+}
+
 extension RunnerTests {
   static let sparseRecoveryTruncatedNodeThreshold = 8
   /// Umbrella wall-clock budget for one capture plan. Individual backends bound themselves,
@@ -69,7 +132,8 @@ extension RunnerTests {
     _ plan: [SnapshotBackendKind],
     app: XCUIApplication,
     options: SnapshotOptions,
-    terminal: SnapshotCaptureTerminalPolicy
+    terminal: SnapshotCaptureTerminalPolicy,
+    timing: SnapshotTimingRecorder? = nil
   ) throws -> DataPayload {
     var best: (kind: SnapshotBackendKind, capture: SnapshotBackendCapture)?
     var firstFailure: (reason: String, code: String)?
@@ -86,7 +150,7 @@ extension RunnerTests {
       }
       let capture: SnapshotBackendCapture
       do {
-        guard let result = try captureWithBackend(kind, app: app, options: options) else {
+        guard let result = try captureWithBackend(kind, app: app, options: options, timing: timing) else {
           continue
         }
         capture = result
@@ -119,6 +183,7 @@ extension RunnerTests {
           firstFailure?.reason ?? "sparse tree"
         )
       }
+      timing?.selectBackend(kind)
       return stampedSnapshotPayload(
         capture,
         backend: kind,
@@ -147,7 +212,10 @@ extension RunnerTests {
     }
 
     let fallbackPayload =
-      best.map { stampedSnapshotPayload($0.capture, backend: $0.kind, state: "sparse", reason: firstFailure) }
+      best.map {
+        timing?.selectBackend($0.kind)
+        return stampedSnapshotPayload($0.capture, backend: $0.kind, state: "sparse", reason: firstFailure)
+      }
       ?? stampedSnapshotPayload(
         SnapshotBackendCapture(payload: sparseTruncatedSnapshotPayload(), effectiveDepth: nil),
         backend: plan.last ?? .recursiveTree,
@@ -160,24 +228,31 @@ extension RunnerTests {
   private func captureWithBackend(
     _ kind: SnapshotBackendKind,
     app: XCUIApplication,
-    options: SnapshotOptions
+    options: SnapshotOptions,
+    timing: SnapshotTimingRecorder?
   ) throws -> SnapshotBackendCapture? {
-    switch kind {
-    case .recursiveTree:
-      guard let context = try makeSnapshotTraversalContext(app: app, options: options) else {
-        return nil
+    try measureSnapshotBackend(timing, kind) {
+      switch kind {
+      case .recursiveTree:
+        guard let context = try makeSnapshotTraversalContext(app: app, options: options, timing: timing) else {
+          return nil
+        }
+        let payload = options.raw
+          ? try measureSnapshotPhase(timing, "raw_tree_shape") {
+              try rawTreeSnapshotPayload(context: context, options: options)
+            }
+          : measureSnapshotPhase(timing, "visible_tree_shape") {
+              recursiveTreeSnapshotPayload(context: context, options: options)
+            }
+        return SnapshotBackendCapture(payload: payload, effectiveDepth: nil)
+      case .querySweep:
+        return SnapshotBackendCapture(
+          payload: snapshotFlatInteractive(app: app, options: options, timing: timing),
+          effectiveDepth: nil
+        )
+      case .privateAX:
+        return privateAXSnapshotCapture(app: app, options: options)
       }
-      let payload = options.raw
-        ? try rawTreeSnapshotPayload(context: context, options: options)
-        : recursiveTreeSnapshotPayload(context: context, options: options)
-      return SnapshotBackendCapture(payload: payload, effectiveDepth: nil)
-    case .querySweep:
-      return SnapshotBackendCapture(
-        payload: snapshotFlatInteractive(app: app, options: options),
-        effectiveDepth: nil
-      )
-    case .privateAX:
-      return privateAXSnapshotCapture(app: app, options: options)
     }
   }