From 5275faa7d32ead6c4da931629adb511a32bc042d Mon Sep 17 00:00:00 2001
From: JoelTowell <joeltowell@hotmail.com>
Date: Tue, 1 Sep 2026 01:45:24 +1000
Subject: [PATCH 1/4] Add regression test for TERM=dumb TTY readline output

---
 test/reline/test_reline.rb | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/test/reline/test_reline.rb b/test/reline/test_reline.rb
index 49c736eb4a..a0a8861e49 100644
--- a/test/reline/test_reline.rb
+++ b/test/reline/test_reline.rb
@@ -428,6 +428,26 @@ def test_readline_returns_nil_on_piped_stdin_eof
     assert_include(out, { result: nil }.inspect)
   end
 
+  def test_dumb_tty_buffered_output_keeps_first_and_finished_renders
+    input = StringIO.new
+    output = StringIO.new
+
+    [input, output].each do |io|
+      def io.tty?
+        true
+      end
+    end
+    io_gate = Reline::Dumb.new
+    io_gate.input = input
+    io_gate.output = output
+
+    io_gate.buffered_output { io_gate.write("first render") }
+    io_gate.buffered_output { io_gate.write("rerender") }
+    io_gate.buffered_output { io_gate.write("finished render\n") }
+
+    assert_equal("first renderfinished render\n", output.string)
+  end
+
   def test_read_eof_returns_input
     pend if win?
     lib = File.expand_path("../../lib", __dir__)

From 8a1a7650ff3be8451fac9f13459af816c6d965fb Mon Sep 17 00:00:00 2001
From: JoelTowell <joeltowell@hotmail.com>
Date: Tue, 1 Sep 2026 01:47:33 +1000
Subject: [PATCH 2/4] Avoid repeated readline renders with TERM=dumb

---
 lib/reline/io/dumb.rb | 18 +++++++++++++++++-
 1 file changed, 17 insertions(+), 1 deletion(-)

diff --git a/lib/reline/io/dumb.rb b/lib/reline/io/dumb.rb
index 0c04c755d2..dd1c31b478 100644
--- a/lib/reline/io/dumb.rb
+++ b/lib/reline/io/dumb.rb
@@ -9,9 +9,11 @@ def initialize(encoding: nil)
     @input = STDIN
     @output = STDOUT
     @buf = []
+    @output_buffer = nil
     @pasting = false
     @encoding = encoding
     @screen_size = [24, 80]
+    @first_render = true
   end
 
   def dumb?
@@ -43,11 +45,24 @@ def with_raw_input
   end
 
   def write(string)
-    @output.write(string)
+    if @output_buffer
+      @output_buffer << string
+    else
+      @output.write(string)
+    end
   end
 
   def buffered_output
+    return yield unless @input.respond_to?(:tty?) && @input.tty? && @output.respond_to?(:tty?) && @output.tty?
+
+    @output_buffer = +''
     yield
+    if @first_render
+      @output.write(@output_buffer)
+      @first_render = false
+    end
+  ensure
+    @output_buffer = nil
   end
 
   def getc(_timeout_second)
@@ -113,6 +128,7 @@ def in_pasting?
   end
 
   def prep
+    @first_render = true
   end
 
   def deprep(otio)

From 0098229a03760fbd3b253232df5de07a6cf605b1 Mon Sep 17 00:00:00 2001
From: JoelTowell <joeltowell@hotmail.com>
Date: Wed, 2 Sep 2026 00:08:13 +1000
Subject: [PATCH 3/4] Drop incomplete dumb TTY redraws

---
 lib/reline/io/dumb.rb | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/lib/reline/io/dumb.rb b/lib/reline/io/dumb.rb
index dd1c31b478..d389def4a7 100644
--- a/lib/reline/io/dumb.rb
+++ b/lib/reline/io/dumb.rb
@@ -53,11 +53,13 @@ def write(string)
   end
 
   def buffered_output
-    return yield unless @input.respond_to?(:tty?) && @input.tty? && @output.respond_to?(:tty?) && @output.tty?
+    return yield unless tty?
 
     @output_buffer = +''
     yield
-    if @first_render
+    # render_finished writes complete transcript lines ending in CRLF. Keep those
+    # while dropping redraws that this IO gate cannot apply in place.
+    if @first_render || @output_buffer.end_with?("\n")
       @output.write(@output_buffer)
       @first_render = false
     end
@@ -65,6 +67,10 @@ def buffered_output
     @output_buffer = nil
   end
 
+  private def tty?
+    @input.respond_to?(:tty?) && @input.tty? && @output.respond_to?(:tty?) && @output.tty?
+  end
+
   def getc(_timeout_second)
     unless @buf.empty?
       return @buf.shift

From 1bed023494663b3db6527a1dafe9cb26ba40d7df Mon Sep 17 00:00:00 2001
From: JoelTowell <joeltowell@hotmail.com>
Date: Wed, 2 Sep 2026 00:16:35 +1000
Subject: [PATCH 4/4] slight cleanup

---
 lib/reline/io/dumb.rb | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/lib/reline/io/dumb.rb b/lib/reline/io/dumb.rb
index d389def4a7..59e1630d7e 100644
--- a/lib/reline/io/dumb.rb
+++ b/lib/reline/io/dumb.rb
@@ -57,8 +57,7 @@ def buffered_output
 
     @output_buffer = +''
     yield
-    # render_finished writes complete transcript lines ending in CRLF. Keep those
-    # while dropping redraws that this IO gate cannot apply in place.
+
     if @first_render || @output_buffer.end_with?("\n")
       @output.write(@output_buffer)
       @first_render = false