Index: lldb/include/lldb/Core/Debugger.h
===================================================================
--- lldb/include/lldb/Core/Debugger.h
+++ lldb/include/lldb/Core/Debugger.h
@@ -128,6 +128,9 @@
                                         const ExecutionContext *exe_ctx,
                                         const Address *addr, Stream &s);
 
+  static void AssertCallback(std::string message, std::string backtrace,
+                             std::string prompt);
+
   void Clear();
 
   bool GetAsyncExecution();
@@ -395,7 +398,6 @@
   /// Since the two checks are mutually exclusive, however, it's also convenient
   /// to have just one function to check the interrupt state.
 
-
   /// Bump the "interrupt requested" count on the debugger to support
   /// cooperative interruption.  If this is non-zero, InterruptRequested will
   /// return true.  Interruptible operations are expected to query the
Index: lldb/include/lldb/Utility/LLDBAssert.h
===================================================================
--- lldb/include/lldb/Utility/LLDBAssert.h
+++ lldb/include/lldb/Utility/LLDBAssert.h
@@ -9,6 +9,8 @@
 #ifndef LLDB_UTILITY_LLDBASSERT_H
 #define LLDB_UTILITY_LLDBASSERT_H
 
+#include <string>
+
 #ifndef NDEBUG
 #define lldbassert(x) assert(x)
 #else
@@ -29,6 +31,11 @@
 namespace lldb_private {
 void lldb_assert(bool expression, const char *expr_text, const char *func,
                  const char *file, unsigned int line);
+
+typedef void (*LLDBAssertCallback)(std::string message, std::string backtrace,
+                                   std::string prompt);
+
+void SetLLDBAssertCallback(LLDBAssertCallback callback);
 } // namespace lldb_private
 
 #endif // LLDB_UTILITY_LLDBASSERT_H
Index: lldb/source/API/SystemInitializerFull.cpp
===================================================================
--- lldb/source/API/SystemInitializerFull.cpp
+++ lldb/source/API/SystemInitializerFull.cpp
@@ -78,6 +78,9 @@
   // Settings must be initialized AFTER PluginManager::Initialize is called.
   Debugger::SettingsInitialize();
 
+  // Use the Debugger's LLDBAssert callback.
+  SetLLDBAssertCallback(Debugger::AssertCallback);
+
   return llvm::Error::success();
 }
 
Index: lldb/source/Core/Debugger.cpp
===================================================================
--- lldb/source/Core/Debugger.cpp
+++ lldb/source/Core/Debugger.cpp
@@ -1352,6 +1352,11 @@
                               function_changed, initial_function);
 }
 
+void Debugger::AssertCallback(std::string message, std::string backtrace,
+                              std::string prompt) {
+  Debugger::ReportError(message + "\n" + backtrace + prompt);
+}
+
 void Debugger::SetLoggingCallback(lldb::LogOutputCallback log_callback,
                                   void *baton) {
   // For simplicity's sake, I am not going to deal with how to close down any
Index: lldb/source/Utility/LLDBAssert.cpp
===================================================================
--- lldb/source/Utility/LLDBAssert.cpp
+++ lldb/source/Utility/LLDBAssert.cpp
@@ -8,7 +8,7 @@
 
 #include "lldb/Utility/LLDBAssert.h"
 #include "llvm/Config/llvm-config.h"
-#include "llvm/Support/Format.h"
+#include "llvm/Support/FormatVariadic.h"
 #include "llvm/Support/Signals.h"
 #include "llvm/Support/raw_ostream.h"
 
@@ -16,12 +16,21 @@
 #include <os/log.h>
 #endif
 
-using namespace llvm;
-using namespace lldb_private;
+namespace lldb_private {
 
-void lldb_private::lldb_assert(bool expression, const char *expr_text,
-                               const char *func, const char *file,
-                               unsigned int line) {
+static void DefaultLLDBAssertCallback(std::string message,
+                                      std::string backtrace,
+                                      std::string prompt) {
+  llvm::errs() << message << '\n';
+  llvm::errs() << backtrace; // Backtrace includes a newline.
+  llvm::errs() << prompt << '\n';
+}
+
+static std::atomic<LLDBAssertCallback> g_lldb_assert_callback =
+    &DefaultLLDBAssertCallback;
+
+void lldb_assert(bool expression, const char *expr_text, const char *func,
+                 const char *file, unsigned int line) {
   if (LLVM_LIKELY(expression))
     return;
 
@@ -35,10 +44,21 @@
 
   // Print a warning and encourage the user to file a bug report, similar to
   // LLVM’s crash handler, and then return execution.
-  errs() << format("Assertion failed: (%s), function %s, file %s, line %u\n",
-                   expr_text, func, file, line);
-  errs() << "backtrace leading to the failure:\n";
-  llvm::sys::PrintStackTrace(errs());
-  errs() << "please file a bug report against lldb reporting this failure "
-            "log, and as many details as possible\n";
+  std::string buffer;
+  llvm::raw_string_ostream backtrace(buffer);
+  llvm::sys::PrintStackTrace(backtrace);
+
+  (*g_lldb_assert_callback.load())(
+      llvm::formatv("Assertion failed: ({0}), function {1}, file {2}, line {3}",
+                    expr_text, func, file, line)
+          .str(),
+      backtrace.str(),
+      "Please file a bug report against lldb reporting this failure log, and "
+      "as many details as possible");
 }
+
+void SetLLDBAssertCallback(LLDBAssertCallback callback) {
+  g_lldb_assert_callback.exchange(callback);
+}
+
+} // namespace lldb_private