diff --git a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerSnapshotBridge.m b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerSnapshotBridge.m
index b224ab7290..771b536857 100644
--- a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerSnapshotBridge.m
+++ b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/RunnerSnapshotBridge.m
@@ -187,7 +187,9 @@ static NSUInteger RunnerSnapshotBridgeBudgetMs(NSDictionary *request)
 static NSTimeInterval RunnerSnapshotBridgeAbandonedAt = 0;
 static const NSTimeInterval RunnerSnapshotBridgeWedgeSeconds = 5;
 
-static dispatch_queue_t RunnerSnapshotBridgeReaderQueue(void)
+// The reader queue and RunnerSnapshotBridgeRead have external linkage so the runner unit bundle can
+// drive them through UnitTests/RunnerSnapshotBridge+Internal.h.
+dispatch_queue_t RunnerSnapshotBridgeReaderQueue(void)
 {
   static dispatch_queue_t queue;
   static dispatch_once_t onceToken;
@@ -207,10 +209,10 @@ @implementation RunnerSnapshotBridgeAnswer
 
 /// Runs one read on the reader queue and waits for it up to `budgetMs`. A read that outlives the budget
 /// is abandoned, not stopped: its answer is dropped when it returns.
-static NSDictionary *RunnerSnapshotBridgeRead(NSDictionary *request,
-                                              NSUInteger budgetMs,
-                                              NSDictionary * (^read)(void),
-                                              NSTimeInterval (^clock)(void))
+NSDictionary *RunnerSnapshotBridgeRead(NSDictionary *request,
+                                       NSUInteger budgetMs,
+                                       NSDictionary * (^read)(void),
+                                       NSTimeInterval (^clock)(void))
 {
   NSUInteger sequence;
   @synchronized (RunnerSnapshotBridgeAnswer.class) {
@@ -252,18 +254,6 @@ @implementation RunnerSnapshotBridgeAnswer
   return answer.value;
 }
 
-#if defined(AGENT_DEVICE_RUNNER_UNIT_TESTS)
-NSDictionary *RunnerSnapshotBridgeReadForTest(NSDictionary *request, NSUInteger budgetMs,
-                                               NSDictionary *(^read)(void), NSTimeInterval now)
-{
-  return RunnerSnapshotBridgeRead(request, budgetMs, read, ^{ return now; });
-}
-void RunnerSnapshotBridgeDrainForTest(void)
-{
-  dispatch_sync(RunnerSnapshotBridgeReaderQueue(), ^{});
-}
-#endif
-
 uint32_t RunnerSnapshotBridgeMaximumFrameBytes(void)
 {
   return kMaximumFrameBytes;
diff --git a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerSnapshotBridge+Internal.h b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerSnapshotBridge+Internal.h
new file mode 100644
index 0000000000..d5c29fcb9b
--- /dev/null
+++ b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerSnapshotBridge+Internal.h
@@ -0,0 +1,19 @@
+#import <Foundation/Foundation.h>
+#import <TargetConditionals.h>
+
+NS_ASSUME_NONNULL_BEGIN
+
+#if TARGET_OS_IOS && TARGET_OS_SIMULATOR
+
+// The snapshot bridge's read admission and reader queue, which RunnerSnapshotBridge.m defines for the
+// runner unit bundle. The packaged runner omits UnitTests/. A read answers with what `read` returns,
+// nil included.
+NSDictionary * _Nullable RunnerSnapshotBridgeRead(NSDictionary *request,
+                                                  NSUInteger budgetMs,
+                                                  NSDictionary * _Nullable (^read)(void),
+                                                  NSTimeInterval (^clock)(void));
+dispatch_queue_t RunnerSnapshotBridgeReaderQueue(void);
+
+#endif
+
+NS_ASSUME_NONNULL_END
diff --git a/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerSnapshotBridgeTesting.m b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerSnapshotBridgeTesting.m
new file mode 100644
index 0000000000..4bb07a35f7
--- /dev/null
+++ b/apple/runner/AgentDeviceRunner/AgentDeviceRunnerUITests/UnitTests/RunnerSnapshotBridgeTesting.m
@@ -0,0 +1,20 @@
+#if defined(AGENT_DEVICE_RUNNER_UNIT_TESTS)
+#import "RunnerSnapshotBridgeTesting.h"
+
+#if TARGET_OS_IOS && TARGET_OS_SIMULATOR
+
+#import "RunnerSnapshotBridge+Internal.h"
+
+NSDictionary *RunnerSnapshotBridgeReadForTest(NSDictionary *request, NSUInteger budgetMs,
+                                               NSDictionary *(^read)(void), NSTimeInterval now)
+{
+  return RunnerSnapshotBridgeRead(request, budgetMs, read, ^{ return now; });
+}
+
+void RunnerSnapshotBridgeDrainForTest(void)
+{
+  dispatch_sync(RunnerSnapshotBridgeReaderQueue(), ^{});
+}
+
+#endif
+#endif