Index: lldb/include/lldb/Core/DebuggerEvents.h
===================================================================
--- lldb/include/lldb/Core/DebuggerEvents.h
+++ lldb/include/lldb/Core/DebuggerEvents.h
@@ -32,6 +32,7 @@
 
   static const ProgressEventData *GetEventDataFromEvent(const Event *event_ptr);
   uint64_t GetID() const { return m_id; }
+  bool IsFinite() const { return m_total != UINT64_MAX; }
   uint64_t GetCompleted() const { return m_completed; }
   uint64_t GetTotal() const { return m_total; }
   const std::string &GetMessage() const { return m_message; }
Index: lldb/source/Core/Debugger.cpp
===================================================================
--- lldb/source/Core/Debugger.cpp
+++ lldb/source/Core/Debugger.cpp
@@ -1857,11 +1857,26 @@
     output->Printf(
         "%s", ansi::FormatAnsiTerminalCodes(ansi_prefix, use_color).c_str());
 
-  // Print the progress message.
+  // Trim the progress message if it exceeds the window's width and print it.
   std::string message = data->GetMessage();
-  if (data->GetTotal() != UINT64_MAX) {
+  uint64_t progress_total = data->GetTotal();
+  uint32_t term_width = GetTerminalWidth();
+
+  size_t prefix_width = 0;
+  if (data->IsFinite()) {
+    prefix_width += 4; // '[%PRIu64/%PRIu64] %s'
+    prefix_width += std::to_string(progress_total).size() * 2;
+  }
+
+  const size_t suffix_width = 3; // %s...
+
+  if (message.size() + prefix_width + suffix_width >= term_width)
+    message.erase(message.begin() + term_width - prefix_width - suffix_width,
+                  message.end());
+
+  if (data->IsFinite()) {
     output->Printf("[%" PRIu64 "/%" PRIu64 "] %s...", data->GetCompleted(),
-                   data->GetTotal(), message.c_str());
+                   progress_total, message.c_str());
   } else {
     output->Printf("%s...", message.c_str());
   }
Index: lldb/test/API/functionalities/progress_reporting/TestTrimmedProgressReporting.py
===================================================================
--- /dev/null
+++ lldb/test/API/functionalities/progress_reporting/TestTrimmedProgressReporting.py
@@ -0,0 +1,38 @@
+"""
+Test resizing in our IOHandlers.
+"""
+
+import os
+import pexpect
+
+import lldb
+from lldbsuite.test.decorators import *
+from lldbsuite.test.lldbtest import *
+from lldbsuite.test.lldbpexpect import PExpectTest
+
+class TestTrimmedProgressReporting(PExpectTest):
+
+    mydir = TestBase.compute_mydir(__file__)
+
+    # PExpect uses many timeouts internally and doesn't play well
+    # under ASAN on a loaded machine..
+    @skipIfAsan
+    @skipIfEditlineSupportMissing
+    @skipIf(oslist=["linux"], archs=["arm", "aarch64"])
+    def test_resize(self):
+        self.build()
+        # Start with a small window
+        self.launch(executable=self.getBuildArtifact("a.out"),
+                    dimensions=(5,5), timeout=1)
+
+        # Now resize to something bigger
+        self.child.setwinsize(100,500)
+
+        patterns = ['Locating external symbol file for',
+                    'Parsing symbol table for', pexpect.EOF, pexpect.TIMEOUT]
+
+        match_index = self.child.expect(patterns)
+
+        self.quit()
+
+        self.assertTrue(match_index, len(patterns) - 1) # match TIMEOUT