Absolute Telnet RC22 -- Scrollback Duplication Follow-Up
========================================================

Date: 2026-03-25
Version: Absolute Telnet 13.16 RC22


SUMMARY

A second RC22 test session was captured. The scrollback duplication issue
is still present.

The pattern differs from the RC21 behavior: smaller repeated blocks
but more copies of them, with a nested duplication pattern and two
different renderings of the same Write operation.


ENVIRONMENT

  SSH Client:          Absolute Telnet 13.16 RC22
  Remote Application:  Claude Code (Anthropic CLI), running over SSH
                       on a Raspberry Pi (Linux 6.12, bash)
  Session Type:        Interactive AI-assisted coding session
                       (magicJack .eml-to-.wav extraction script)
  Captured output:     1942 lines


OBSERVED BEHAVIOR

The scrollback capture contains 4 copies of a 116-line base block
(the session start through the Claude Code banner), plus a 36-line
summary block that appears twice. Additionally, the same Write
operation appears in two different renderings (expanded and collapsed).


Block structure in the captured text:

  Region                Lines       Size     Content
  ------                -----       ----     -------
  Shell prompt          1           1        claude --resume command
  Block 1 (original)    2-118       117      Banner + initial session
  Block 2 (DUPLICATE)   119-235     117      Exact copy of lines 2-118
  Block 3a (DUPLICATE)  236-351     116      Exact copy of lines 2-117
  Block 3b (unique)     352-625     274      v1.0 completion + expanded
                                             Write diff dialog
  Block 4a (DUPLICATE)  626-741     116      Exact copy of lines 2-117
  Block 4b (DUPLICATE)  742-777     36       Exact copy of lines 352-387
                                             (summary through user prompt)
  Block 4c (unique)     778-1072    295      Collapsed Write diff +
                                             v1.1 results
  Remainder (unique)    1073-1942   870      Rest of session


Duplication totals:

  Exact duplicated lines:              384 (19.8% of file)
  Including near-duplicate rendering:  ~622 (~32% of file)
  Unique content:                      ~1557 lines


TRIGGER POINTS

Every base-block repetition is triggered at the same point: the
line reading:

  "All 30 .eml files produced 31 .wav files (one is the duplicate
  from the first test run that incremented the counter to -002).
  Let me also"

This is an incomplete sentence where Claude Code was mid-output.
The ANSI cursor movement sequences used to update the display caused
the scrollback to replay the entire visible buffer from the top.

The 4th copy (line 626) has a different trigger -- it appears mid-way
through the expanded diff output from the Write dialog, suggesting
the diff rendering itself triggered another full-screen redraw.


NOTABLE CHARACTERISTICS

1. Nested duplication:
   Block 4 contains both a copy of the base block (lines 2-117) AND
   a copy of the summary content from block 3 (lines 352-387). This
   is a layered pattern not seen in RC21.

2. Two renderings of the same Write operation:
   Block 3b (lines 388-625) shows the v1.1 Write as an expanded
   "Overwrite file" dialog with the full inline diff.
   Block 4c (lines 778-1060) shows the same Write operation in
   collapsed form ("Added 126 lines, removed 39 lines").
   These are NOT byte-identical but represent the same content
   rendered two different ways, suggesting the scrollback captured
   the content both before and after Claude Code's collapse event.

3. Mid-sentence trigger:
   All duplications occur at points where Claude Code was in the
   middle of outputting text, consistent with TUI redraw events
   being captured as duplicate scrollback content.


COMPARISON WITH RC21

  Metric                RC21                This file (RC22)
  ------                ----                ----------------
  Total lines           3960                1942
  Repeated block size   497 lines           116 lines (primary)
  Number of copies      6                   4 (of primary block)
  Exact duplication %   ~75%                ~20%
  With near-duplicates  ~75%                ~32%
  Pattern               Same base repeated  Smaller base repeated
                        6 times with        4 times, plus nested
                        growing new         duplication and dual
                        content after each  rendering of same op
  Trigger               Mid-diff display    Mid-sentence output


CONCLUSION

RC22 reduced the severity compared to RC21 (exact duplication down
from ~75% to ~20%), but the root cause remains. The duplication
pattern in this session is more complex than RC21, featuring:

  - Multiple small-block repeats instead of fewer large-block repeats
  - Nested duplication (a repeat containing a repeat)
  - The same operation captured in both expanded and collapsed form

This suggests the scrollback buffer is still being replayed when
Claude Code performs certain ANSI cursor movement operations,
particularly during mid-output TUI redraws and Write tool output
collapse/expand transitions.