diff --git a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+CommandExecution.swift b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+CommandExecution.swift
index 1f8477482b..6be914e7cc 100644
--- a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+CommandExecution.swift
+++ b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+CommandExecution.swift
@@ -1576,10 +1576,10 @@ extension RunnerTests {
         if let bundleId = requestedBundleId {
           activeApp = activateTarget(bundleId: bundleId, reason: "missing_after_wait")
           guard activeApp.waitForExistence(timeout: appExistenceTimeout) else {
-            return .response(Response(ok: false, error: ErrorPayload(message: "app '\(bundleId)' is not available")))
+            return .response(Response(ok: false, error: .targetAppUnavailable(bundleId: bundleId)))
           }
         } else {
-          return .response(Response(ok: false, error: ErrorPayload(message: "runner app is not available")))
+          return .response(Response(ok: false, error: .targetAppUnavailable(bundleId: nil)))
         }
       }
 
@@ -1595,10 +1595,9 @@ extension RunnerTests {
           requestedBundleId: requestedBundleId
         )
         if !skipInteractionExistenceWait && !activeApp.waitForExistence(timeout: 2) {
-          if let bundleId = requestedBundleId {
-            return .response(Response(ok: false, error: ErrorPayload(message: "app '\(bundleId)' is not available")))
-          }
-          return .response(Response(ok: false, error: ErrorPayload(message: "runner app is not available")))
+          return .response(
+            Response(ok: false, error: .targetAppUnavailable(bundleId: requestedBundleId))
+          )
         }
         applyInteractionStabilizationIfNeeded()
       }
diff --git a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Lifecycle.swift b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Lifecycle.swift
index 57bde60d26..57e4467cd3 100644
--- a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Lifecycle.swift
+++ b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Lifecycle.swift
@@ -431,17 +431,8 @@ extension RunnerTests {
 
   func shouldRetryException(_ command: Command, message: String) -> Bool {
     guard shouldRetryCommand(command) else { return false }
-    let normalized = message.lowercased()
-    if normalized.contains("kaxerrorservernotfound") {
-      return true
-    }
-    if normalized.contains("main thread execution timed out") {
-      return true
-    }
-    if normalized.contains("timed out") && command.command == .snapshot {
-      return true
-    }
-    return false
+    // XCTest raises this AX error as an ObjC exception whose reason is the only handle on it.
+    return message.lowercased().contains("kaxerrorservernotfound")
   }
 
   // MARK: - Command Classification
@@ -460,8 +451,7 @@ extension RunnerTests {
 
   func shouldRetryResponse(_ response: Response) -> Bool {
     guard response.ok == false else { return false }
-    guard let message = response.error?.message.lowercased() else { return false }
-    return message.contains("is not available")
+    return response.error?.retryableFailure != nil
   }
 
   func isInteractionCommand(_ command: CommandType) -> Bool {
diff --git a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Models.swift b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Models.swift
index 4ddd306b16..2a4b84de27 100644
--- a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Models.swift
+++ b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Models.swift
@@ -385,8 +385,30 @@ struct SnapshotQualityPayload: Codable {
   }
 }
 
+/// A runner failure the read-only retry may recover from by re-resolving the target.
+enum RetryableResponseFailure: Equatable {
+  case targetAppUnavailable
+}
+
 struct ErrorPayload: Codable {
   var code: String?
   let message: String
   var hint: String?
+  /// Runner-internal: read by `shouldRetryResponse` and never encoded, so the host's decoding of
+  /// the error is unchanged.
+  var retryableFailure: RetryableResponseFailure? = nil
+
+  private enum CodingKeys: String, CodingKey {
+    case code
+    case message
+    case hint
+  }
+
+  static func targetAppUnavailable(bundleId: String?) -> ErrorPayload {
+    let subject = bundleId.map { "app '\($0)'" } ?? "runner app"
+    return ErrorPayload(
+      message: "\(subject) is not available",
+      retryableFailure: .targetAppUnavailable
+    )
+  }
 }
diff --git a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Snapshot.swift b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Snapshot.swift
index 04e83a38f3..83686731cf 100644
--- a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Snapshot.swift
+++ b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerTests+Snapshot.swift
@@ -764,7 +764,7 @@ extension RunnerTests {
       Command.self,
       from: Data(#"{"command":"snapshot","commandId":"recovery-guard"}"#.utf8)
     )
-    let recovered = Response(ok: false, error: ErrorPayload(message: "target is not available"))
+    let recovered = Response(ok: false, error: .targetAppUnavailable(bundleId: nil))
 
     setAbandonedMainThreadWork(1)
     defer { setAbandonedMainThreadWork(0) }
diff --git a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerTests+LifecycleTests.swift b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerTests+LifecycleTests.swift
index c9c14b436d..cba532f03b 100644
--- a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerTests+LifecycleTests.swift
+++ b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerTests+LifecycleTests.swift
@@ -28,6 +28,37 @@ extension RunnerTests {
     }
   }
 
+  func testTargetAppUnavailableResponseIsRetried() {
+    for bundleId in ["com.example.app", nil] as [String?] {
+      let response = Response(ok: false, error: .targetAppUnavailable(bundleId: bundleId))
+      XCTAssertTrue(shouldRetryResponse(response), String(describing: bundleId))
+    }
+    let reworded = ErrorPayload(message: "target vanished", retryableFailure: .targetAppUnavailable)
+    XCTAssertTrue(shouldRetryResponse(Response(ok: false, error: reworded)))
+  }
+
+  func testUntypedUnavailableMessageIsNotRetried() {
+    for message in ["app 'com.example.app' is not available", "runner app is not available"] {
+      let response = Response(ok: false, error: ErrorPayload(message: message))
+      XCTAssertFalse(shouldRetryResponse(response), message)
+    }
+    let succeeded = Response(ok: true, error: .targetAppUnavailable(bundleId: nil))
+    XCTAssertFalse(shouldRetryResponse(succeeded))
+  }
+
+  func testExceptionRetryIsLimitedToTheAxServerNotFoundReadOnlyCase() throws {
+    let readText = try runnerCommandFixture(#"{"command":"readText"}"#)
+    let snapshot = try runnerCommandFixture(#"{"command":"snapshot"}"#)
+    let tap = try runnerCommandFixture(#"{"command":"tap"}"#)
+    let axServerNotFound = "NSException: Error kAXErrorServerNotFound"
+    XCTAssertTrue(shouldRetryException(readText, message: axServerNotFound))
+    XCTAssertFalse(shouldRetryException(tap, message: axServerNotFound))
+    XCTAssertFalse(
+      shouldRetryException(readText, message: "NSException: main thread execution timed out")
+    )
+    XCTAssertFalse(shouldRetryException(snapshot, message: "NSException: query timed out"))
+  }
+
   func testInlineScreenshotResponseKeepsDisplayFactsBesideTheImage() throws {
     let pngData = Data([0x89, 0x50, 0x4E, 0x47])
     let response = screenshotResponse(
diff --git a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerTests+ModelsTests.swift b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerTests+ModelsTests.swift
new file mode 100644
index 0000000000..d0079bf728
--- /dev/null
+++ b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerTests+ModelsTests.swift
@@ -0,0 +1,32 @@
+import Foundation
+import XCTest
+
+#if AGENT_DEVICE_RUNNER_UNIT_TESTS
+extension RunnerTests {
+  func testErrorPayloadEncodesEveryFieldButTheRunnerInternalRetryableFailure() throws {
+    let payload = ErrorPayload(
+      code: "CODE",
+      message: "message",
+      hint: "hint",
+      retryableFailure: .targetAppUnavailable
+    )
+    let encoded = try JSONEncoder().encode(payload)
+    let object = try XCTUnwrap(JSONSerialization.jsonObject(with: encoded) as? [String: Any])
+    let storedFields = Set(Mirror(reflecting: payload).children.compactMap(\.label))
+    XCTAssertEqual(Set(object.keys), storedFields.subtracting(["retryableFailure"]))
+  }
+
+  func testTargetAppUnavailableErrorKeepsItsWireShape() throws {
+    let encoded = try JSONEncoder().encode(
+      ErrorPayload.targetAppUnavailable(bundleId: "com.example.app")
+    )
+    let object = try XCTUnwrap(JSONSerialization.jsonObject(with: encoded) as? [String: Any])
+    XCTAssertEqual(Array(object.keys), ["message"])
+    XCTAssertEqual(object["message"] as? String, "app 'com.example.app' is not available")
+    XCTAssertEqual(
+      ErrorPayload.targetAppUnavailable(bundleId: nil).message,
+      "runner app is not available"
+    )
+  }
+}
+#endif