A command line runs as its own command pane unless it is clicked at a shell's prompt

A middle click, an exec write or a tag word that no builtin knows was typed
into some terminal for the pane's directory, sharing whatever state that
shell was in and answering nothing, so a misspelling vanished into a shell.
Now only a line clicked at an interactive terminal's prompt is typed there.
From anywhere else it runs as a command pane: a terminal whose child is
$SHELL -c the line in the pane's directory, full emulation, which shows its
output and then exit N from the host's reaping of the child, and stays. A
finished command pane is the next command's for its directory, which runs
below what it showed after a '% line' line (acme appends to +Errors and never
clears it, util.c:213); a running one gets a second pane. Kill ends a command
pane's whole process group, the log records run and exit, exec reads back the
command pane's serial, and a line is at most 1 KB, read off the pane as the
host forks rather than carried in every spawn effect. ttyForDir's search for
a free shell is gone. The goldens of chordcut, cmdword and layout-open change
where a file's exec now opens a command pane, and ttytaken is rewritten to
exec from the terminal itself; docs/open-questions.md records the decision.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

7 files changed, 122 insertions, 109 deletions

diff --git a/test/snapshots/chordcut.golden b/test/snapshots/chordcut.golden
index b814d888..42725e42 100644
--- a/test/snapshots/chordcut.golden
+++ b/test/snapshots/chordcut.golden
@@ -30,11 +30,11 @@
 == snap cancelexec grid=120x31 cursor=25,8
 |8:      2  2echo B''OO g.txt
 == snap execafter grid=120x31 cursor=25,8
-|3:     f.txt                                                     ls
-|4:   BOO                                                         f.txt  g.txt
-|7:      1 line 1                                          Exec
+|6:    /tmp/pardes-snap/chordcut/cwd/f.txt * Save Tty Collapse D   /tmp/pardes-snap/chordcut/cwd (echo B''OO) exit 0 Kill Sa
+|7:      1 line 1                                          Exec   BOO
+|8:      2  2echo B''OO g.txt                                     exit 0
 == snap cancellook grid=120x31 cursor=25,8
-|7:      1 line 1
+|7:      1 line 1                                                 BOO
 == snap lookafter grid=120x31 cursor=7,13
 |12:    /tmp/pardes-snap/chordcut/cwd/g.txt Save Tty Collapse Del
 |13:      1 line 1
@@ -44,10 +44,10 @@
 |0: 0-70 #b2c3b8,#1d2824, 71-119 d,#1d2824,
 |1: 0-1 #ffffff,#887455, 2-2 d,#26362d, 3-34 #becfc4,#26362d, 35-59 d,#26362d, 60-61 #ffffff,#887455, 62-62 d,#1d2824, 63-94 #b2c3b8,#1d2824, 95-119 d,#1d2824,
 |2: 0-1 #ffffff,#496656, 2-2 d,#1d2824, 3-32 #b2c3b8,#1d2824, 33-35 #d3b0d9,#1d2824, 36-59 #b2c3b8,#1d2824, 60-61 #ffffff,#496656, 62-62 d,#1d2824, 63-92 #b2c3b8,#1d2824, 93-95 #d3b0d9,#1d2824, 96-119 #b2c3b8,#1d2824,
-|3: 0-0 d,#152019, 1-1 d,#0d1410, 2-8 #e5eee5,#0d1410, 9-59 d,#0d1410, 60-60 d,#608269, 61-61 d,#0d1410, 62-119 #e5eee5,#0d1410,
+|3: 0-0 d,#608269, 1-1 d,#0d1410, 2-59 #e5eee5,#0d1410, 60-60 d,#608269, 61-61 d,#0d1410, 62-119 #e5eee5,#0d1410,
 |4: 0-0 d,#608269, 1-1 d,#0d1410, 2-59 #e5eee5,#0d1410, 60-60 d,#608269, 61-61 d,#0d1410, 62-119 #e5eee5,#0d1410,
-|5: 0-0 d,#152019, 1-59 d,#0d1410, 60-60 d,#608269, 61-119 d,#0d1410,
-|6: 0-1 #ffffff,#496656, 2-2 d,#1d2824, 3-32 #b2c3b8,#1d2824, 33-37 #d3b0d9,#1d2824, 38-59 #b2c3b8,#1d2824, 60-60 d,#608269, 61-61 d,#0d1410, 62-119 #e5eee5,#0d1410,
+|5: 0-0 d,#608269, 1-59 d,#0d1410, 60-60 d,#608269, 61-119 d,#0d1410,
+|6: 0-1 #ffffff,#496656, 2-2 d,#1d2824, 3-32 #b2c3b8,#1d2824, 33-37 #d3b0d9,#1d2824, 38-59 #b2c3b8,#1d2824, 60-61 #ffffff,#496656, 62-62 d,#1d2824, 63-119 #b2c3b8,#1d2824,
 |7: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-12 #e5eee5,#0d1410, 13-59 d,#0d1410, 60-60 d,#608269, 61-61 d,#0d1410, 62-119 #e5eee5,#0d1410,
 |8: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-24 #e5eee5,#0d1410, 25-59 d,#0d1410, 60-60 d,#608269, 61-61 d,#0d1410, 62-119 #e5eee5,#0d1410,
 |9: 0-0 d,#608269, 1-1 d,#0d1410, 2-6 #59675c,#0d1410, 7-12 #e5eee5,#0d1410, 13-59 d,#0d1410, 60-60 d,#608269, 61-61 d,#0d1410, 62-119 #e5eee5,#0d1410,
diff --git a/test/snapshots/cmdword.golden b/test/snapshots/cmdword.golden
index 99ad446b..0b6d91aa 100644
--- a/test/snapshots/cmdword.golden
+++ b/test/snapshots/cmdword.golden
@@ -4,21 +4,24 @@
 |   /tmp/pardes-snap/cmdword/cwd/cmds.txt Save Tty Collapse Del
 |     1 @`echo ZZ''E` @`echo ZZ''L` Look p.txt @`Look .`
 == snap atexec grid=120x31 cursor=7,3
-|17:    /tmp/pardes-snap/cmdword/cwd Tty Save Mode Filter Collapse Del
-|18:   echo ZZ''E
-|19:   ZZE
-== snap atlook grid=120x31 cursor=4,22
-|20:   echo ZZ''L
+|17:    /tmp/pardes-snap/cmdword/cwd (echo ZZ''E) exit 0 Kill Save Collapse Del
+|18:   ZZE
+|19:   exit 0
+== snap atlook grid=120x31 cursor=2,23
+|17:    /tmp/pardes-snap/cmdword/cwd (echo ZZ''L) exit 0 Kill Save Collapse Del
+|20:   % echo ZZ''L
 |21:   ZZL
+|22:   exit 0
 == snap lookword grid=120x31 cursor=7,11
 |10:    /tmp/pardes-snap/cmdword/cwd/p.txt Save Tty Collapse Del
 |11:      1 just text
-== snap nested grid=120x31 cursor=4,24
-|22:   ls
-|23:   cmds.txt  p.txt  zzmark.txt
-== snap execword grid=120x31 cursor=4,24
-|17:    /tmp/pardes-snap/cmdword/cwd Tty Save Mode Filter Collapse Del Exec
-== snap tagcmd grid=120x31 cursor=4,24
-|17:    /tmp/pardes-snap/cmdword/cwd Tty Save Mode Filter Collapse Del Exec @`echo ZZ''T`
-|24:   echo ZZ''T
-|25:   ZZT
+== snap nested grid=120x31 cursor=4,9
+|6:    /tmp/pardes-snap/cmdword/cwd Tty Save Mode Filter Collapse Del
+|7:   ls
+|8:   cmds.txt  p.txt  zzmark.txt
+== snap execword grid=120x31 cursor=4,9
+|6:    /tmp/pardes-snap/cmdword/cwd Tty Save Mode Filter Collapse Del Exec
+== snap tagcmd grid=120x31 cursor=4,7
+|6:    /tmp/pardes-snap/cmdword/cwd Tty Save Mode Filter Collapse Del Exec @`echo ZZ''T`
+|7:   echo ZZ''T
+|8:   ZZT
diff --git a/test/snapshots/cmdword.snap b/test/snapshots/cmdword.snap
index 361e37ba..631fab8b 100644
--- a/test/snapshots/cmdword.snap
+++ b/test/snapshots/cmdword.snap
@@ -7,9 +7,10 @@
 # whole run instead, which is what makes a single CLICK the way you invoke one
 # (acme does the same for its own `<`/`|`/`>` command words).
 #
-# EXECUTE runs it and leaves you where you were; LOOK runs it and lands you in
-# the shell that answered — looking at a thing means being shown it, and a
-# directory's look has always been exactly that (a shell there, ls'd).
+# EXECUTE runs it, as a command pane, and leaves you where you were; LOOK runs
+# it and lands you in the pane that answered — looking at a thing means being
+# shown it, and a directory's look has always been exactly that (a shell
+# there, ls'd).
 #
 # And Look and Exec are ORDINARY BUILTINS now, so their names are executable
 # words like Save or Grep: `Look p.txt` run off the page is the same look a
@@ -28,14 +29,15 @@ wait 8000 cmds.txt
 stable 700 20000
 snap opened
 # a single middle CLICK inside the run (col 11 is inside `echo`) expands to the
-# whole `@`echo ZZ''E`` and executes it in a shell; focus stays on the file
+# whole `@`echo ZZ''E`` and runs it as a command pane; focus stays on the file
 press middle 11 4
 release middle 11 4
 wait 10000 ZZE
 stable 700 15000
 snap atexec
-# LOOK on the second one (col 24, inside its `echo`) runs it too AND focuses
-# the shell that answered — that is the whole difference between the two verbs
+# LOOK on the second one (col 24, inside its `echo`) runs it too, in the same
+# command pane now its first is done, below it, AND focuses it — that is the
+# whole difference between the two verbs
 press right 24 4
 release right 24 4
 wait 10000 ZZL
@@ -49,16 +51,16 @@ wait 10000 just text
 stable 700 15000
 snap lookword
 # nesting: `@`Look .`` — Exec unwraps it, `Look .` is parsed as the ordinary
-# Look builtin with an argument, and Look opens the directory (an existing
-# shell there, ls'd — zzmark.txt is only ever in that listing)
+# Look builtin with an argument, and Look opens the directory (a shell there,
+# ls'd — zzmark.txt is only ever in that listing; a command pane is no shell)
 press middle 49 4
 release middle 49 4
 wait 10000 zzmark.txt
 stable 700 15000
 snap nested
 # the same syntax typed into a TAG — the other place the expansion has to know
-# about backticks. The look above left the shell focused, so `:` opens ITS
-# tag; `A` appends at the end of it, Esc and `h` put the normal-mode cursor on
+# about backticks. The look above left that shell focused, so `:` opens ITS
+# tag, and the word run from a shell's own tag is typed into it; `A` appends at the end of it, Esc and `h` put the normal-mode cursor on
 # the last character typed, and the execute key runs the word under it
 # exactly as the body's does.
 key :
diff --git a/test/snapshots/layout-open.golden b/test/snapshots/layout-open.golden
index f682924a..2bfdde63 100644
--- a/test/snapshots/layout-open.golden
+++ b/test/snapshots/layout-open.golden
@@ -31,6 +31,6 @@
 |21:    /tmp/pardes-snap/layout-open/cwd/sub/f.txt Save
 |22:      1 echo 'TTY'OK
 == snap ttydir grid=100x31 cursor=7,22
-|10:                                                      /tmp/pardes-snap/layout-open/cwd/sub Tty Save M
-|11:                                                     echo 'TTY'OK
-|12:                                                     TTYOK
+|10:                                                      /tmp/pardes-snap/layout-open/cwd/sub (echo 'TTY
+|11:                                                     TTYOK
+|12:                                                     exit 0
diff --git a/test/snapshots/layout-open.snap b/test/snapshots/layout-open.snap
index d7d7e19e..04770f27 100644
--- a/test/snapshots/layout-open.snap
+++ b/test/snapshots/layout-open.snap
@@ -1,5 +1,5 @@
 # every pane open splits ONE existing pane, the rest of the column keeps its
-# sizes: Alt-n splits the active pane, an execute-spawned shell for a file's
+# sizes: Alt-n splits the active pane, an execute-spawned command pane for a file's
 # dir splits only the bottom pane of the rightmost column. At this narrow
 # width the first looked-up file also splits below its source, leaving every
 # unrelated pane (including the ones above the source) at its exact rectangle.
@@ -44,9 +44,9 @@ press right 7 28
 release right 7 28
 stable 700 15000
 snap file-open
-# execute the file's command (middle drag over line 1): no shell has cwd sub/,
-# so one is forked at the bottom of the rightmost column, splitting only the
-# pane above it
+# execute the file's command (middle drag over line 1): it runs as a command
+# pane for sub/, forked at the bottom of the rightmost column, splitting only
+# the pane above it
 press middle 8 23
 drag middle 19 23
 release middle 19 23
diff --git a/test/snapshots/ttytaken.golden b/test/snapshots/ttytaken.golden
index 72708e64..3fb29738 100644
--- a/test/snapshots/ttytaken.golden
+++ b/test/snapshots/ttytaken.golden
@@ -1,47 +1,48 @@
-== snap opened grid=210x31 cursor=7,3
+== snap opened grid=210x31 cursor=4,5
 |Newcol Joincol Find Grep Help Changelog Tutor Dump NextColor Debug Exit
-|   New Tty Find Grep Joincol Delcol                                                                         New Tty Find Grep Joincol Delcol
-|   /tmp/pardes-snap/ttytaken/cwd/cmd.txt Save Tty Collapse Del                                              /tmp/pardes-snap/ttytaken/cwd Tty Save Mode Filter Collapse Del
-|     1 echo TAKEN''ONE                                                                                     ls
-|     2 echo TAKEN''TWO                                                                                     big.txt  cmd.txt
-== snap at-prompt grid=210x31 cursor=7,3
-|3:      1 echo TAKEN''ONE                                                                              Exec   ls
-|5:                                                                                                            echo TAKEN''ONE
-|6:                                                                                                            TAKENONE
-== snap paging grid=210x31 cursor=114,30
-|2:    /tmp/pardes-snap/ttytaken/cwd/cmd.txt Save Tty Collapse Del                                           $  /tmp/pardes-snap/ttytaken/cwd Tty Save Mode Filter Collapse Del
-|3:      1 echo TAKEN''ONE                                                                                     line 1
-|4:      2 echo TAKEN''TWO                                                                                     line 2
-|5:                                                                                                            line 3
-|6:                                                                                                            line 4
-|7:                                                                                                            line 5
-|8:                                                                                                            line 6
-|9:                                                                                                            line 7
-|10:                                                                                                            line 8
-|11:                                                                                                            line 9
-|12:                                                                                                            line 10
-|13:                                                                                                            line 11
-|14:                                                                                                            line 12
-|15:                                                                                                            line 13
-|16:                                                                                                            line 14
-|17:                                                                                                            line 15
-|18:                                                                                                            line 16
-|19:                                                                                                            line 17
-|20:                                                                                                            line 18
-|21:                                                                                                            line 19
-|22:                                                                                                            line 20
-|23:                                                                                                            line 21
-|24:                                                                                                            line 22
-|25:                                                                                                            line 23
-|26:                                                                                                            line 24
-|27:                                                                                                            line 25
-|28:                                                                                                            line 26
-|29:                                                                                                            line 27
-|30:                                                                                                            big.txt
-== snap spawned grid=210x31 cursor=108,26
-|3:      1 echo TAKEN''ONE                                                                              Exec   line 1
-|26:                                                                                                            :
-|27:                                                                                                             /tmp/pardes-snap/ttytaken/cwd Tty Save Mode Filter Collapse Del
-|28:                                                                                                            echo TAKEN''TWO
-|29:                                                                                                            TAKENTWO
+|   New Tty Find Grep Joincol Delcol
+|   /tmp/pardes-snap/ttytaken/cwd Tty Save Mode Filter Collapse Del
+|  ls
+|  big.txt
+== snap at-prompt grid=210x31 cursor=4,5
+|2:    /tmp/pardes-snap/ttytaken/cwd Tty Save Mode Filter Collapse Del @`echo TAKEN''ONE`
+|3:   ls                                                                                                                                                                                                         Exec
+|5:   echo TAKEN''ONE
+|6:   TAKENONE
+== snap paging grid=210x31 cursor=9,30
+|3:   line 1
+|4:   line 2
+|5:   line 3
+|6:   line 4
+|7:   line 5
+|8:   line 6
+|9:   line 7
+|10:   line 8
+|11:   line 9
+|12:   line 10
+|13:   line 11
+|14:   line 12
+|15:   line 13
+|16:   line 14
+|17:   line 15
+|18:   line 16
+|19:   line 17
+|20:   line 18
+|21:   line 19
+|22:   line 20
+|23:   line 21
+|24:   line 22
+|25:   line 23
+|26:   line 24
+|27:   line 25
+|28:   line 26
+|29:   line 27
+|30:   big.txt
+== snap spawned grid=210x31 cursor=104,2
+|2:    /tmp/pardes-snap/ttytaken/cwd Tty Save Mode Filter Collapse Del @`echo TAKEN''ONE` @`echo TAKEN''TWO`
+|3:   line 1                                                                                                                                                                                                     Exec
+|26:   :
+|27:    /tmp/pardes-snap/ttytaken/cwd (echo TAKEN''TWO) exit 0 Kill Save Collapse Del
+|28:   TAKENTWO
+|29:   exit 0
 |30:
diff --git a/test/snapshots/ttytaken.snap b/test/snapshots/ttytaken.snap
index 47554876..a6ccb632 100644
--- a/test/snapshots/ttytaken.snap
+++ b/test/snapshots/ttytaken.snap
@@ -1,43 +1,50 @@
-# Process monitoring, end to end. A pane whose tty is held by a full-screen
-# program is not somewhere a command line may be typed: the SAME middle-drag
-# Exec goes into the shell while it sits at its prompt, and into a NEW shell
-# beside it once `less` owns the terminal — where it runs, instead of becoming
-# keystrokes the pager would eat. Nothing about the pager's screen changes.
-file cmd.txt echo TAKEN''ONE\necho TAKEN''TWO
+# Process monitoring, end to end. A terminal whose tty is held by a
+# full-screen program is not somewhere a command line may be typed: the SAME
+# Exec from that terminal goes into its shell while it sits at its prompt,
+# and into a command pane of its own once `less` owns the terminal -- where
+# it runs, instead of becoming keystrokes the pager would eat. Nothing about
+# the pager's screen changes. (From any pane but a terminal, an Exec always
+# runs as a command pane: exec.snap and cmdword.snap.)
 lines big.txt 40
 start 31 210 -n 1
-wait 8000 cmd.txt
-stable 700 20000
-# open the command file by looking its name in the greeting `ls`
-press right 14 5
-release right 14 5
-wait 10000 echo TAKEN
+wait 8000 big.txt
 stable 700 20000
 snap opened
-# at the prompt: the drag runs in the shell that is already on this directory
-press middle 8 4
-drag middle 22 4
-release middle 22 4
+# at the prompt: a command word in the terminal's own tag, executed, is
+# typed into its shell. `:` opens the tag, `A` appends, and the execute key
+# runs the word under the cursor.
+key :
+key A
+key space
+text @`echo TAKEN''ONE`
+key esc
+settle 100
+key h
+key tab
 wait 10000 TAKENONE
 stable 700 20000
 snap at-prompt
-# ...and now a pager owns that terminal. Ctrl-b is raw tty (config.tty_toggle),
-# which is how a script types AT the shell instead of into the pane's own edit
-# buffer — the same way exec.snap runs a command line.
-press left 150 9
-release left 150 9
-stable 400 5000
+# ...and now a pager owns that terminal. Ctrl-b is raw tty
+# (config.tty_toggle), which is how a script types AT the shell instead of
+# into the pane's own edit buffer.
 key c-b
 stable 400 5000
 text env LESS= less big.txt
 key enter
 wait 10000 line 1
 stable 700 20000
+key c-b
+stable 400 5000
 snap paging
-# the same gesture on the second line: a new shell, not `less` keystrokes
-press middle 8 5
-drag middle 22 5
-release middle 22 5
+# the same gesture from that terminal: a command pane, not `less` keystrokes
+key :
+key A
+key space
+text @`echo TAKEN''TWO`
+key esc
+settle 100
+key h
+key tab
 wait 10000 TAKENTWO
 stable 700 20000
 snap spawned