feat(c5): prune old tmux logs and share pipe-pane helper

Extract the tmux pipe-pane setup into functions/_tmux_pipe_log.fish,
called by both conf.d/tmux-logging.fish (startup) and
__fish_config_sync_logging (C5 re-enable). The helper prunes the oldest
tmux_*.log files by mtime to stay within SCROLLBACK_HISTORY_MAX_FILES,
matching the paru/yay wrappers.

Uses 'command ls' to bypass the eza ls shadow, which injects OSC-8
hyperlink escapes into paths and corrupted the filenames passed to rm.

conf.d/tmux-logging.fish

@@ -11,10 +11,4 @@ status is-interactive; or exit
 type -q tmux; or exit
 set -q TMUX; or exit
 
-set -l log_dir (set -q SCROLLBACK_HISTORY_DIR; and echo $SCROLLBACK_HISTORY_DIR; or echo "$HOME/.terminal_history")
-set -l pane_id (tmux display-message -p '#{session_name}-w#{window_index}-p#{pane_index}' 2>/dev/null)
-set -l timestamp (date "+%Y-%m-%d_%H-%M-%S")
-set -l log_file "$log_dir/tmux_"$pane_id"_"$timestamp".log"
-
-mkdir -p $log_dir
-tmux pipe-pane "cat >> $log_file" 2>/dev/null
+_tmux_pipe_log

docs/fish-config.md

@@ -1697,7 +1697,9 @@ The tmux capture starts automatically when fish launches inside any tmux
 pane ($TMUX is set). It uses tmux's native pipe-pane to stream all pane
 output directly to disk without an intermediate process. Each fish shell
 session gets its own log file; a new log is created on each shell start
-(including exec fish and new splits).
+(including exec fish and new splits). Before each new log, the oldest
+tmux_*.log files are pruned (by modification time) to keep the total within
+SCROLLBACK_HISTORY_MAX_FILES, matching the paru/yay wrapper behaviour.
 
 Logging coordination via sentinel file
 

functions/__fish_config_sync_logging.fish

@@ -34,14 +34,7 @@ function __fish_config_sync_logging --description 'Sync C5 logging state: sentin
         rm -f $sentinel
 
         # Restart tmux pipe-pane for the current pane if inside tmux
-        if set -q TMUX
-            set -l log_dir (set -q SCROLLBACK_HISTORY_DIR; and echo $SCROLLBACK_HISTORY_DIR; or echo "$HOME/.terminal_history")
-            set -l pane_id (tmux display-message -p '#{session_name}-w#{window_index}-p#{pane_index}' 2>/dev/null)
-            set -l timestamp (date "+%Y-%m-%d_%H-%M-%S")
-            set -l log_file "$log_dir/tmux_"$pane_id"_"$timestamp".log"
-            mkdir -p $log_dir
-            tmux pipe-pane "cat >> $log_file" 2>/dev/null
-        end
+        _tmux_pipe_log
 
         if test -x /usr/bin/paru
             mkdir -p (dirname $paru_wrapper)

functions/_tmux_pipe_log.fish

@@ -0,0 +1,45 @@
+# Copyright (C) 2026 Rootiest
+# SPDX-License-Identifier: AGPL-3.0-or-later
+
+# SYNOPSIS
+#   _tmux_pipe_log
+#
+# DESCRIPTION
+#   Starts tmux pipe-pane capture for the current pane, streaming its output
+#   to a timestamped log in SCROLLBACK_HISTORY_DIR (default ~/.terminal_history).
+#   Before starting, prunes the oldest tmux_*.log files so that the total stays
+#   within SCROLLBACK_HISTORY_MAX_FILES (default 100), leaving room for the new
+#   log. No-op when not inside a tmux session ($TMUX unset) or tmux is missing.
+#   Shared by conf.d/tmux-logging.fish (shell startup) and
+#   __fish_config_sync_logging (C5 re-enable) so both stay in sync.
+#
+# RETURNS
+#   0  Always
+#
+# EXAMPLE
+#   _tmux_pipe_log
+function _tmux_pipe_log --description 'Start tmux pipe-pane capture for the current pane, with pruning'
+    set -q TMUX; or return 0
+    type -q tmux; or return 0
+
+    set -l log_dir (set -q SCROLLBACK_HISTORY_DIR; and echo $SCROLLBACK_HISTORY_DIR; or echo "$HOME/.terminal_history")
+    set -l max_files (set -q SCROLLBACK_HISTORY_MAX_FILES; and echo $SCROLLBACK_HISTORY_MAX_FILES; or echo 100)
+    set -l pane_id (tmux display-message -p '#{session_name}-w#{window_index}-p#{pane_index}' 2>/dev/null)
+    set -l timestamp (date "+%Y-%m-%d_%H-%M-%S")
+    set -l log_file "$log_dir/tmux_"$pane_id"_"$timestamp".log"
+
+    mkdir -p $log_dir
+
+    # Prune oldest logs, leaving room for the one we're about to create.
+    # Names carry a per-pane prefix, so sort by mtime (command ls -tr = oldest
+    # first). Use `command ls`: the bare `ls` is shadowed by the eza wrapper,
+    # which injects OSC-8 escapes into paths and corrupts the filenames.
+    set -l keep (math max 0, $max_files - 1)
+    set -l logs (command ls -1tr $log_dir/tmux_*.log 2>/dev/null)
+    if test (count $logs) -gt $keep
+        set -l excess (math (count $logs) - $keep)
+        command rm -f $logs[1..$excess]
+    end
+
+    tmux pipe-pane "cat >> $log_file" 2>/dev/null
+end