diff --git a/Sources/Shotdeck/UpdateChecker.swift b/Sources/Shotdeck/UpdateChecker.swift
index 5b705cb..4ccc003 100644
--- a/Sources/Shotdeck/UpdateChecker.swift
+++ b/Sources/Shotdeck/UpdateChecker.swift
@@ -36,6 +36,8 @@ final class UpdateChecker {
     /// this value (including nil) is returned instead of checking the file system.
     var snapshotPreviousVersionOverride: String?
     var snapshotUsesPreviousVersionOverride: Bool = false
+    /// Test seam: override appcast JSON. When set, returns this instead of fetching from URL.
+    var testAppcastJSON: String?
 
     init() {
         let config = URLSessionConfiguration.ephemeral
@@ -359,7 +361,12 @@ final class UpdateChecker {
     }
 
     private func fetchAppcast() async throws -> Appcast {
-        let data = try await fetchData(from: Self.resolvedAppcastURL())
+        let data: Data
+        if let testJSON = testAppcastJSON {
+            data = testJSON.data(using: .utf8) ?? Data()
+        } else {
+            data = try await fetchData(from: Self.resolvedAppcastURL())
+        }
         return try JSONDecoder().decode(Appcast.self, from: data)
     }
 
diff --git a/Tests/ShotdeckTests/UpdateCheckerTests.swift b/Tests/ShotdeckTests/UpdateCheckerTests.swift
index d0d694c..7b31ed5 100644
--- a/Tests/ShotdeckTests/UpdateCheckerTests.swift
+++ b/Tests/ShotdeckTests/UpdateCheckerTests.swift
@@ -5,11 +5,10 @@ import Testing
 
 @Test("DubaiTime.checkTime formats as HH:MM Dubai")
 func dubaiTimeCheckTimeFormat() {
-    let testDate = Date(timeIntervalSince1970: 1725458520) // 2024-09-04 10:42:00 UTC
-    let result = DubaiTime.checkTime(testDate)
+    let now = Date()
+    let result = DubaiTime.checkTime(now)
 
-    // The format should be HH:MM Dubai (24-hour time in Dubai timezone)
-    // Dubai is UTC+4, so a UTC time needs conversion
+    // Dubai timezone format: HH:MM Dubai
     let pattern = "^[0-9]{2}:[0-9]{2} Dubai$"
     let regex = try? NSRegularExpression(pattern: pattern, options: [])
     let range = NSRange(result.startIndex..<result.endIndex, in: result)
@@ -17,45 +16,103 @@ func dubaiTimeCheckTimeFormat() {
     #expect(!matches.isEmpty, "checkTime should format as HH:MM Dubai, got: \(result)")
 }
 
-@Test("Status message format: 'Redline X.Y.Z is up to date, checked HH:MM Dubai'")
+@Test("Status message: up-to-date manual check includes Dubai timestamp")
 @MainActor
-func statusMessageUpToDateFormat() {
-    let currentVersion = UpdateChecker.currentVersion()
-    let testTime = DubaiTime.checkTime(Date())
-    let message = "Redline \(currentVersion) is up to date, checked \(testTime)"
+func manualCheckUpToDateIncludesTimestamp() async {
+    let checker = UpdateChecker()
 
-    // Verify the format matches the expected pattern
+    // Inject a stub appcast showing the current version (no update available)
+    let currentVersion = UpdateChecker.currentVersion()
+    let stubAppcast = """
+    {
+      "version": "\(currentVersion)",
+      "zipURL": "https://example.com/dummy.zip",
+      "sha256": "0000000000000000000000000000000000000000000000000000000000000000"
+    }
+    """
+    checker.testAppcastJSON = stubAppcast
+
+    // Capture the status message
+    var capturedStatus: String?
+    checker.onChecked = {
+        capturedStatus = checker.statusMessage
+    }
+
+    // Run the manual check
+    await checker.checkNow(manual: true)
+
+    // Verify the message matches the expected format and includes a timestamp
+    guard let status = capturedStatus else {
+        #expect(false, "statusMessage should not be nil for manual check finding no update")
+        return
+    }
+
+    // Message should be "Redline X.Y.Z is up to date, checked HH:MM Dubai"
     let pattern = "^Redline [0-9]+\\.[0-9]+\\.[0-9]+ is up to date, checked [0-9]{2}:[0-9]{2} Dubai$"
     let regex = try? NSRegularExpression(pattern: pattern, options: [])
-    let range = NSRange(message.startIndex..<message.endIndex, in: message)
-    let matches = regex?.matches(in: message, options: [], range: range) ?? []
-    #expect(!matches.isEmpty, "Message should match format, got: \(message)")
+    let range = NSRange(status.startIndex..<status.endIndex, in: status)
+    let matches = regex?.matches(in: status, options: [], range: range) ?? []
+    #expect(!matches.isEmpty, "Manual check up-to-date message should match format, got: \(status)")
 }
 
-@Test("Status message format: 'Update to X.Y.Z is ready'")
-func statusMessageUpdateReadyFormat() {
-    let testVersion = "9.9.9"
-    let message = "Update to \(testVersion) is ready"
+@Test("Status message: automatic check doesn't set message when up-to-date")
+@MainActor
+func automaticCheckUpToDateLeavesMessageNil() async {
+    let checker = UpdateChecker()
 
-    // Verify the format matches the expected pattern
-    let pattern = "^Update to [0-9]+\\.[0-9]+\\.[0-9]+ is ready$"
-    let regex = try? NSRegularExpression(pattern: pattern, options: [])
-    let range = NSRange(message.startIndex..<message.endIndex, in: message)
-    let matches = regex?.matches(in: message, options: [], range: range) ?? []
-    #expect(!matches.isEmpty, "Message should match format, got: \(message)")
+    // Inject a stub appcast showing the current version (no update available)
+    let currentVersion = UpdateChecker.currentVersion()
+    let stubAppcast = """
+    {
+      "version": "\(currentVersion)",
+      "zipURL": "https://example.com/dummy.zip",
+      "sha256": "0000000000000000000000000000000000000000000000000000000000000000"
+    }
+    """
+    checker.testAppcastJSON = stubAppcast
+
+    // Capture the status message
+    var capturedStatus: String?
+    checker.onChecked = {
+        capturedStatus = checker.statusMessage
+    }
+
+    // Run an AUTOMATIC check (manual: false)
+    await checker.checkNow(manual: false)
+
+    // For automatic checks finding no update, statusMessage should be nil
+    #expect(capturedStatus == nil,
+            "Automatic check finding no update should leave statusMessage nil, got: \(capturedStatus ?? "(nil)")")
 }
 
 @Test("Update status and general status are independent channels")
 @MainActor
-func statusChannelsAreIndependent() {
-    // Test the channel independence without creating a full model.
-    // setStatus affects statusLine, setUpdateStatus affects updateStatus.
-    // They should be separate properties that don't interfere.
+func statusChannelsAreIndependent() async throws {
+    let fm = FileManager.default
+    let appSupportRoot = fm.temporaryDirectory
+        .appendingPathComponent("update-checker-channel-test-\(UUID().uuidString)", isDirectory: true)
+    defer { try? fm.removeItem(at: appSupportRoot) }
 
-    // Hypothetical test: if we had a model, setting one shouldn't affect the other.
-    // For now, we verify that the API exists and can be called independently.
-    // The full integration test happens in the panel snapshot.
+    // Create a real AppModel using the standard launch pattern
+    let model = AppDelegate.makeLaunchModel(appSupportRoot: appSupportRoot)
+    defer { model.hotkeys.unregisterAll() }
 
-    // Verify the property names and access patterns are correct
-    #expect(true, "Status channels are independent by design: statusLine and updateStatus")
+    // Test 1: Setting statusLine should NOT affect updateStatusMessage
+    model.setStatus("General status: captured 3")
+    #expect(model.statusLine == "General status: captured 3", "statusLine should be set")
+    #expect(model.updateStatusMessage == nil, "updateStatusMessage should remain nil")
+
+    // Test 2: Setting updateStatus should NOT affect statusLine
+    model.setUpdateStatus("Update to 9.9.9 is ready")
+    #expect(model.statusLine == "General status: captured 3", "statusLine should remain unchanged")
+    #expect(model.updateStatusMessage == "Update to 9.9.9 is ready", "updateStatusMessage should be set")
+
+    // Test 3: Clearing statusLine leaves updateStatus intact
+    model.setStatus(nil)
+    #expect(model.statusLine == nil, "statusLine should be cleared")
+    #expect(model.updateStatusMessage == "Update to 9.9.9 is ready", "updateStatusMessage should persist")
+
+    // Test 4: Clearing updateStatus leaves other state unaffected
+    model.setUpdateStatus(nil)
+    #expect(model.updateStatusMessage == nil, "updateStatusMessage should be cleared")
 }