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
@@ -1852,20 +1852,26 @@
     return;
   }
 
+  // Trim the progress message if it exceeds the window's width and print it.
+  std::string message = data->GetMessage();
+  if (data->IsFinite())
+    message = llvm::formatv("[{0}/{1}] {2}", data->GetCompleted(),
+                            data->GetTotal(), message)
+                  .str();
+
+  // Trim the progress message if it exceeds the window's width and print it.
+  const uint32_t term_width = GetTerminalWidth();
+  const uint32_t ellipsis = 3;
+  if (message.size() + ellipsis >= term_width)
+    message = message.substr(0, term_width - ellipsis);
+
   const bool use_color = GetUseColor();
   llvm::StringRef ansi_prefix = GetShowProgressAnsiPrefix();
   if (!ansi_prefix.empty())
     output->Printf(
         "%s", ansi::FormatAnsiTerminalCodes(ansi_prefix, use_color).c_str());
 
-  // Print the progress message.
-  std::string message = data->GetMessage();
-  if (data->GetTotal() != UINT64_MAX) {
-    output->Printf("[%" PRIu64 "/%" PRIu64 "] %s...", data->GetCompleted(),
-                   data->GetTotal(), message.c_str());
-  } else {
-    output->Printf("%s...", message.c_str());
-  }
+  output->Printf("%s...", message.c_str());
 
   llvm::StringRef ansi_suffix = GetShowProgressAnsiSuffix();
   if (!ansi_suffix.empty())
Index: lldb/test/API/functionalities/progress_reporting/TestTrimmedProgressReporting.py
===================================================================
--- /dev/null
+++ lldb/test/API/functionalities/progress_reporting/TestTrimmedProgressReporting.py
@@ -0,0 +1,50 @@
+"""
+Test trimming long progress report in tiny terminal windows
+"""
+
+import os
+import pexpect
+import tempfile
+import re
+
+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__)
+
+    def do_test(self, term_width, pattern_list):
+        self.build()
+        # Start with a small window
+        self.launch(use_colors=True)
+        self.expect("set set show-progress true")
+        self.expect("set show show-progress", substrs=["show-progress (boolean) = true"])
+        self.expect("set set term-width " + str(term_width))
+        self.expect("set show term-width", substrs=["term-width (int) = " + str(term_width)])
+
+        self.child.send("file " + self.getBuildArtifact("a.out") + "\n")
+        self.child.expect(pattern_list)
+
+
+    # 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_trimmed_progress_message(self):
+        self.do_test(19, ['Locating externa...',
+                          'Loading Apple DW...',
+                          'Parsing symbol t...'])
+
+    # 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_long_progress_message(self):
+        self.do_test(80, ['Locating external symbol file for a.out...',
+                          'Loading Apple DWARF index for a.out...',
+                          'Parsing symbol table for dyld...'])