diff --git a/Core/PeekabooAutomationKit/Sources/PeekabooAutomationKit/Services/Capture/ScreenCapturePermissionGate.swift b/Core/PeekabooAutomationKit/Sources/PeekabooAutomationKit/Services/Capture/ScreenCapturePermissionGate.swift
index 8d2ee6228..a12d80d1f 100644
--- a/Core/PeekabooAutomationKit/Sources/PeekabooAutomationKit/Services/Capture/ScreenCapturePermissionGate.swift
+++ b/Core/PeekabooAutomationKit/Sources/PeekabooAutomationKit/Services/Capture/ScreenCapturePermissionGate.swift
@@ -6,9 +6,29 @@ import Foundation
     func hasPermission(logger: CategoryLogger) async -> Bool
 }
 
-struct ScreenRecordingPermissionChecker: ScreenRecordingPermissionEvaluating {
-    func hasPermission(logger: CategoryLogger) async -> Bool {
-        let preflightResult = CGPreflightScreenCaptureAccess()
+@MainActor
+@_spi(Testing) public struct ScreenRecordingPermissionChecker: ScreenRecordingPermissionEvaluating {
+    private let preflight: @MainActor @Sendable () -> Bool
+    private let shareableContentProbe: @MainActor @Sendable () async throws -> Void
+
+    public init() {
+        self.preflight = { CGPreflightScreenCaptureAccess() }
+        self.shareableContentProbe = {
+            _ = try await ScreenCaptureKitCaptureGate.currentShareableContent()
+        }
+    }
+
+    /// Test seam: inject preflight and shareable-content probe results.
+    @_spi(Testing) public init(
+        preflight: @escaping @MainActor @Sendable () -> Bool,
+        shareableContentProbe: @escaping @MainActor @Sendable () async throws -> Void)
+    {
+        self.preflight = preflight
+        self.shareableContentProbe = shareableContentProbe
+    }
+
+    public func hasPermission(logger: CategoryLogger) async -> Bool {
+        let preflightResult = self.preflight()
         if preflightResult {
             return true
         }
@@ -17,16 +37,20 @@ struct ScreenRecordingPermissionChecker: ScreenRecordingPermissionEvaluating {
         // granted because TCC tracks by code signature and the check can fail after rebuilds or for non-.app bundles.
         logger.debug("CGPreflightScreenCaptureAccess returned false, probing SCShareableContent")
         do {
-            _ = try await ScreenCaptureKitCaptureGate.currentShareableContent()
+            try await self.shareableContentProbe()
             logger.info("Screen recording permission granted (SCShareableContent probe)")
             return true
         } catch {
             if let delay = ScreenCaptureKitTransientError.retryDelayNanoseconds(after: error) {
                 logger.warning(
                     "Screen recording permission probe hit transient ScreenCaptureKit denial; retrying once")
+                // `try?` would swallow CancellationError and continue a second SCK probe after cancel.
                 try? await Task.sleep(nanoseconds: delay)
+                guard !Task.isCancelled else {
+                    return false
+                }
                 do {
-                    _ = try await ScreenCaptureKitCaptureGate.currentShareableContent()
+                    try await self.shareableContentProbe()
                     logger.info("Screen recording permission granted (SCShareableContent retry)")
                     return true
                 } catch {
diff --git a/Core/PeekabooAutomationKit/Tests/PeekabooAutomationKitTests/ScreenRecordingPermissionCancelTests.swift b/Core/PeekabooAutomationKit/Tests/PeekabooAutomationKitTests/ScreenRecordingPermissionCancelTests.swift
new file mode 100644
index 000000000..09999640c
--- /dev/null
+++ b/Core/PeekabooAutomationKit/Tests/PeekabooAutomationKitTests/ScreenRecordingPermissionCancelTests.swift
@@ -0,0 +1,58 @@
+import Foundation
+import XCTest
+@testable @_spi(Testing) import PeekabooAutomationKit
+
+@MainActor
+final class ScreenRecordingPermissionCancelTests: XCTestCase {
+    func testCancelDuringTransientPermissionRetrySkipsSecondProbe() async {
+        let logging = MockLoggingService()
+        let logger = logging.logger(category: "test")
+        var probeCount = 0
+
+        let checker = ScreenRecordingPermissionChecker(
+            preflight: { false },
+            shareableContentProbe: {
+                probeCount += 1
+                throw NSError(
+                    domain: "com.apple.ScreenCaptureKit.SCStreamErrorDomain",
+                    code: -3801,
+                    userInfo: [
+                        NSLocalizedDescriptionKey: "The user declined TCCs for application, window, display capture",
+                    ])
+            })
+
+        let task = Task { @MainActor in
+            await checker.hasPermission(logger: logger)
+        }
+
+        // Cancel during the 350ms transient-denial sleep.
+        try? await Task.sleep(nanoseconds: 50_000_000)
+        task.cancel()
+        let granted = await task.value
+
+        XCTAssertFalse(granted)
+        XCTAssertEqual(probeCount, 1, "canceled permission probe must not run a second SCShareableContent call")
+    }
+
+    func testNonCancelledTransientPermissionRetryProbesTwice() async {
+        let logging = MockLoggingService()
+        let logger = logging.logger(category: "test")
+        var probeCount = 0
+
+        let checker = ScreenRecordingPermissionChecker(
+            preflight: { false },
+            shareableContentProbe: {
+                probeCount += 1
+                throw NSError(
+                    domain: "com.apple.ScreenCaptureKit.SCStreamErrorDomain",
+                    code: -3801,
+                    userInfo: [
+                        NSLocalizedDescriptionKey: "The user declined TCCs for application, window, display capture",
+                    ])
+            })
+
+        let granted = await checker.hasPermission(logger: logger)
+        XCTAssertFalse(granted)
+        XCTAssertEqual(probeCount, 2, "non-cancelled transient denial still retries once")
+    }
+}
diff --git a/scripts/prove-screencapture-permission-cancel.swift b/scripts/prove-screencapture-permission-cancel.swift
new file mode 100644
index 000000000..40746e1c5
--- /dev/null
+++ b/scripts/prove-screencapture-permission-cancel.swift
@@ -0,0 +1,92 @@
+// Standalone proof for fix/screencapture-permission-honor-cancel (PR #280).
+// Mirrors ScreenRecordingPermissionChecker transient denial retry:
+// unfixed: try? sleep then second probe even after cancel
+// fixed:   try? sleep + guard !Task.isCancelled before second probe
+//
+// Usage:
+//   swiftc -parse-as-library -o /tmp/prove-sck-perm scripts/prove-screencapture-permission-cancel.swift
+//   /tmp/prove-sck-perm
+
+import Foundation
+
+func unfixedPermissionProbe(probe: @escaping () async throws -> Void) async -> (probes: Int, elapsedMs: Double, granted: Bool) {
+    var probes = 0
+    let start = Date()
+    do {
+        probes += 1
+        try await probe()
+        return (probes, Date().timeIntervalSince(start) * 1000, true)
+    } catch {
+        try? await Task.sleep(nanoseconds: 350_000_000)
+        // No cancel guard — second probe always runs.
+        do {
+            probes += 1
+            try await probe()
+            return (probes, Date().timeIntervalSince(start) * 1000, true)
+        } catch {
+            return (probes, Date().timeIntervalSince(start) * 1000, false)
+        }
+    }
+}
+
+func fixedPermissionProbe(probe: @escaping () async throws -> Void) async -> (probes: Int, elapsedMs: Double, granted: Bool) {
+    var probes = 0
+    let start = Date()
+    do {
+        probes += 1
+        try await probe()
+        return (probes, Date().timeIntervalSince(start) * 1000, true)
+    } catch {
+        try? await Task.sleep(nanoseconds: 350_000_000)
+        guard !Task.isCancelled else {
+            return (probes, Date().timeIntervalSince(start) * 1000, false)
+        }
+        do {
+            probes += 1
+            try await probe()
+            return (probes, Date().timeIntervalSince(start) * 1000, true)
+        } catch {
+            return (probes, Date().timeIntervalSince(start) * 1000, false)
+        }
+    }
+}
+
+@main
+struct Proof {
+    static func main() async {
+        print("=== Screen-recording permission probe cancel proof (PR #280) ===")
+        print("Pattern matches ScreenRecordingPermissionChecker.hasPermission")
+        print()
+
+        let failing: () async throws -> Void = {
+            throw NSError(domain: "com.apple.ScreenCaptureKit.SCStreamErrorDomain", code: -3801)
+        }
+
+        print("Test 1: Unfixed — cancel after 50ms into 350ms delay")
+        let unfixedTask = Task {
+            await unfixedPermissionProbe(probe: failing)
+        }
+        try? await Task.sleep(nanoseconds: 50_000_000)
+        unfixedTask.cancel()
+        let unfixed = await unfixedTask.value
+        print("  probes=\(unfixed.probes) elapsed_ms=\(String(format: "%.0f", unfixed.elapsedMs)) granted=\(unfixed.granted)")
+
+        print("Test 2: Fixed — cancel after 50ms into 350ms delay")
+        let fixedTask = Task {
+            await fixedPermissionProbe(probe: failing)
+        }
+        try? await Task.sleep(nanoseconds: 50_000_000)
+        fixedTask.cancel()
+        let fixed = await fixedTask.value
+        print("  probes=\(fixed.probes) elapsed_ms=\(String(format: "%.0f", fixed.elapsedMs)) granted=\(fixed.granted)")
+        print()
+
+        if unfixed.probes >= 2, fixed.probes == 1, fixed.granted == false {
+            print("PASS: unfixed ran second SCShareableContent probe after cancel (\(unfixed.probes) probes)")
+            print("PASS: fixed stopped at first probe without second SCK call (\(fixed.probes) probe, \(String(format: "%.0f", fixed.elapsedMs))ms)")
+        } else {
+            print("FAIL")
+            exit(1)
+        }
+    }
+}