fix: restore the terminal on SIGINT/SIGQUIT (closes #12)

The port installed handlers for SIGHUP and SIGTERM only, so SIGINT and
SIGQUIT killed the process with tcell still holding the tty and dropped
the user into a shell with no echo and a scrambled screen. All four
signals now go to one os/signal channel read by one goroutine, and every
path calls Terminal.Fini before os.Exit(0) -- C's leave(), "leave
quickly but curteously" (main.c).

The save decision, written into the savesOnSignal comment: SIGHUP and
SIGTERM keep autosaving; SIGINT and SIGQUIT restore and exit without
saving. No path in C saves on INT or QUIT (leave() is endwin-and-exit,
quit() confirms/scores/exits, endit() goes through fatal(), and
save.c auto_save is reserved for HUP/TERM), the semantics agree
(involuntary teardown is worth rescuing a game from; a deliberate "stop
now" must not become a one-keystroke checkpoint against an anti-save-scum
save discipline), and it is the safe choice, since AutoSave gob-encodes
live state the main goroutine is still mutating after removing the old
file.

One reader of one signal is also what closes the corruption window: a
second signal arriving while a SIGHUP's AutoSave is mid-write stays
unread in the buffer instead of exiting out from under the writer.

cmd/rogue/main_test.go covers the ordering per signal, the save/no-save
split, the mid-save second-signal interleaving, and real
SIGINT/SIGQUIT/SIGHUP/SIGTERM delivered to the test process through the
same notifySignals wiring the game uses.

Two premises behind the report were wrong and are recorded rather than
silently fixed: leave() is not installed on SIGINT/SIGQUIT during play
(the wiring is in mdport.c; the shipped build calls md_onsignal_default
and installs nothing, and leave() appears only in the endgame paths of
rip.c and main.c), and Ctrl-C never generated SIGINT here anyway, since
tcell's raw mode clears ISIG and the key arrives as byte 0x03 -- as it
did in C, whose setup() calls curses raw(). The real exposure is
kill -INT / kill -QUIT and the window before term.New().

ARCHITECTURE.md section 9 gains rows for SIGTSTP/tstp() (deliberately
dropped: raw mode means Ctrl-Z cannot reach the process, suspending the
screen from the signal goroutine would race the drawing goroutine, and C
armed tstp only after a successful restore(); the ! shell escape covers
the need), for SIGINT not routing to the interactive quit() prompt, and
for auto_save on the fault signals. Section 5.3's claim that tcell
handles SIGTSTP was false -- tcell registers only SIGWINCH -- and is
corrected.

ARCHITECTURE.md

@@ -1513,8 +1513,18 @@ Ported drawing code keeps its structure: `mvaddch(y, x, ch)` →
 buffer, preserving the "screen is a data structure" idiom without touching the
 real terminal. `md_readchar`'s escape decoding is deleted; tcell's `EventKey`
 provides decoded keys and we translate to the byte codes `command()` already
-handles (KeyUp → 'k', etc.). SIGTSTP/resume and resize are handled by tcell;
+handles (KeyUp → 'k', etc.). Resize is handled by tcell, which registers only
-SIGHUP/SIGTERM → `autoSave` via `os/signal`.
+SIGWINCH — SIGTSTP is not among the signals it takes, and is dropped (§9).
+
+Signals are handled in `cmd/rogue/main.go`: one `os/signal` channel read by one
+goroutine that reads exactly one signal, so a second signal can never call
+`os.Exit` out from under an in-flight save. SIGHUP and SIGTERM `AutoSave` on the
+way out (save.c `auto_save`); SIGINT and SIGQUIT restore the terminal and exit
+without saving, matching C — where `auto_save` is reserved for HUP/TERM and
+neither `leave()` nor `quit()` nor `endit()` writes a save file — and keeping a
+deliberate interrupt from becoming a free checkpoint. Every path restores the
+terminal via `Terminal.Fini` before exiting, which is the whole point of C's
+`leave()`, "leave quickly but curteously".
 
 ### 5.4 Messaging
 
@@ -1715,6 +1725,39 @@ exit. Those are the steps referenced above (e.g. "step 5", "step 7").
 | tty dsusp/ltc character juggling                                   | tcell owns the tty         | none                        |
 | shell escape (`!`) setuid dance                                    | no privileges to drop      | plain `os/exec` shell       |
 | curses window save in save file                                    | screen is derivable        | redraw on restore           |
+| `tstp()` SIGTSTP suspend/resume                                    | see below                  | `!` shell escape            |
+| SIGINT → the interactive `quit()` prompt                           | see below                  | `Q`; SIGINT exits cleanly   |
+| `auto_save` on SIGILL/TRAP/FPE/BUS/SEGV/SYS                        | see below                  | none                        |
+
+The three signal rows warrant more than a table cell.
+
+**SIGTSTP / `tstp()`.** Not handled, deliberately. Ctrl-Z cannot reach the game
+as a signal in the first place: tcell puts the tty in raw mode (`term.MakeRaw`
+clears `ISIG`, which is what makes `VSUSP` live), so Ctrl-Z arrives as key byte
+`0x1a`, exactly as it did in C, whose `setup()` calls curses `raw()` for the
+same effect. Only an explicit `kill -TSTP` can deliver it, which is not a player
+action. Handling it properly would mean calling `Screen.Suspend`/`Resume` from
+the signal goroutine while the game goroutine may be inside `Render` or
+`PollEvent` — a data race — so a correct port would have to plumb the signal
+through the input loop and handle it synchronously, a design change well beyond
+a signal-safety fix. C's own wiring here is vestigial: `tstp` is armed only by
+`md_tstpresume()`, which runs after a successful `restore()`, so a freshly
+started C game never had a SIGTSTP handler either. `term.Tcell.ShellEscape` (the
+`!` command) already covers getting to a shell and back, doing the same
+suspend/resume dance synchronously on the game goroutine where it is safe.
+
+**SIGINT → `quit()`.** Under `md_onsignal_autosave` C routed SIGINT into the
+interactive "really quit?" prompt. The port exits instead (after restoring the
+terminal): the handler runs on another goroutine, and re-entering the message
+and input machinery from there would race every screen and state access the main
+goroutine makes. The `Q` command reaches the same prompt from inside the turn
+loop, which is where the player actually quits.
+
+**Fault signals.** `md_onsignal_autosave` also sent SIGILL, SIGTRAP, SIGFPE,
+SIGBUS, SIGSEGV and SIGSYS to `auto_save`. In Go these are runtime panics with
+their own diagnostics, and gob-encoding the state that just faulted would risk
+replacing a good save file with a corrupt one, so they are left alone. SIGHUP
+and SIGTERM still autosave.
 
 ## 10. Testing strategy
 

TODO.md

@@ -34,6 +34,48 @@ wizard commands).
 
 # Completed Steps
 
+- 2026-08-09 Signal-time terminal restore (`sig-leave`, closes #12): the port
+  handled only SIGHUP and SIGTERM, so SIGINT and SIGQUIT killed the process with
+  tcell still holding the tty, leaving the user at a shell with no echo. All
+  four signals now go to one `os/signal` channel read by one goroutine in
+  `cmd/rogue/main.go`, and every path calls `Terminal.Fini` before `os.Exit(0)`
+  — C's `leave()`, "leave quickly but curteously". **The decision** (written
+  into the `savesOnSignal` comment): SIGHUP/SIGTERM keep autosaving,
+  SIGINT/SIGQUIT restore and exit **without** saving. C never saves on INT or
+  QUIT anywhere — `leave()` is endwin-and-exit, `quit()` confirms/scores/exits,
+  `endit()` goes through `fatal()`, and `save.c auto_save` is reserved for
+  HUP/TERM — and the semantics agree: HUP/TERM are involuntary teardown worth
+  rescuing a game from, while INT/QUIT are a deliberate "stop now" that must not
+  become a one-keystroke checkpoint against a save discipline built to be
+  anti-save-scum. It is also the safe choice: `AutoSave` gob-encodes live state
+  that the main goroutine is still mutating, after removing the old file, so on
+  the signals with nothing to rescue the port takes the option with no
+  corruption window. The single-reader design closes the window the issue warned
+  about: a second signal arriving mid-save stays unread in the buffer instead of
+  exiting out from under the writer (`TestLeaveOnSignalIgnoresLaterSignals`
+  reproduces exactly that interleaving). New `cmd/rogue/main_test.go` covers the
+  ordering for each signal, the save/no-save split against `savesOnSignal`, the
+  mid-save-second-signal case, and real SIGINT/SIGQUIT/SIGHUP/SIGTERM delivered
+  to the test process through the same `notifySignals` wiring the game uses; the
+  tty leaving raw mode is the one step not checkable headlessly (it needs a
+  controlling terminal), and `term.Tcell.Fini` is a direct pass-through to
+  tcell's `Screen.Fini` that `myExit` already depends on. Two premises in the
+  issue turned out to be wrong and are recorded in ARCHITECTURE.md: `leave()` is
+  not installed on SIGINT/SIGQUIT during play (the wiring is in `mdport.c`, the
+  shipped build calls `md_onsignal_default()` and installs nothing, and
+  `leave()` appears only in the endgame paths of `rip.c`/`main.c`), and Ctrl-C
+  never generated SIGINT here anyway, since tcell's raw mode clears `ISIG` and
+  the key arrives as byte `0x03` — as it did in C, whose `setup()` calls curses
+  `raw()`. The real exposure is `kill -INT`/`kill -QUIT` and the window before
+  `term.New()`. ARCHITECTURE.md §9 gained rows for SIGTSTP/`tstp()` (dropped:
+  raw mode means Ctrl-Z cannot reach us, a suspend from the signal goroutine
+  would race the drawing goroutine, and C armed `tstp` only after a `restore()`;
+  the `!` shell escape covers the need), for SIGINT not routing to the
+  interactive `quit()` prompt, and for `auto_save` on the fault signals; §5.3's
+  claim that tcell handles SIGTSTP was false — tcell registers only SIGWINCH —
+  and is corrected. `Next Step` deliberately not rotated: out-of-band issue
+  work.
+
 - 2026-08-09 Wizard-create bounds fix (`fix/wizard-which-bounds`, closes #10):
   `createObj` stored the raw `0-f` nibble as `Object.Which` with no bounds
   check, so wizard mode -> `C` -> `/` -> `f` produced a wand numbered 15 against

cmd/rogue/main.go

@@ -69,7 +69,7 @@ func run() int {
 		return 0
 	}
 
-	installAutosave(g, t)
+	installSignalHandlers(g, t)
 
 	g.Run() // does not return: the game ends by exiting the process
 
@@ -101,19 +101,102 @@ func loadParams() game.Params {
 	}
 }
 
-// installAutosave saves the game and exits on SIGHUP/SIGTERM (save.c
+// saver is the autosave half of *game.RogueGame that the signal handler
-// auto_save).
+// needs; an interface so the handler is testable headlessly.
-func installAutosave(g *game.RogueGame, t *term.Tcell) {
+type saver interface {
+	// AutoSave writes the game to its save file, best effort (save.c
+	// auto_save).
+	AutoSave()
+}
+
+// finisher is the terminal-restoring half of game.Terminal that the
+// signal handler needs (curses endwin).
+type finisher interface {
+	// Fini restores the terminal to its pre-game state.
+	Fini()
+}
+
+// handledSignals returns the signals the game leaves on. They split into
+// two groups with deliberately different save behavior; see
+// savesOnSignal.
+func handledSignals() []os.Signal {
+	return []os.Signal{
+		syscall.SIGHUP, syscall.SIGTERM, syscall.SIGINT, syscall.SIGQUIT,
+	}
+}
+
+// savesOnSignal reports whether the game should autosave on its way out
+// for this signal.
+//
+// THE DECISION (issue #12): SIGHUP and SIGTERM save; SIGINT and SIGQUIT
+// restore the terminal and exit WITHOUT saving. This is deliberate, not
+// an oversight, on three grounds.
+//
+// C: no path in the C game saves on INT or QUIT. The shipped build
+// installs no handler at all during play (mach_dep.c setup calls
+// md_onsignal_default), and the only INT handler it ever installs is
+// rip.c/main.c's leave() in the endgame — endwin and exit, explicitly
+// discarding pending output. The build that does wire INT during play
+// (md_onsignal_autosave, mdport.c, compiled only under DUMP) sends it to
+// quit(), which confirms, scores, and exits, again without saving, and
+// sends QUIT to endit() -> fatal() -> endwin + exit. save.c auto_save is
+// reserved for HUP/TERM. Saving on HUP/TERM but not on INT/QUIT is
+// therefore exactly C's split.
+//
+// Semantics: HUP and TERM mean involuntary teardown — the line dropped
+// or the machine is going down — so rescuing the game is right. INT and
+// QUIT are the player deliberately saying "stop now". Rogue scores a
+// deliberate quit, and its save discipline is anti-save-scum by design
+// (restoring consumes the file), so making Ctrl-C a free checkpoint
+// would turn it into a one-keystroke undo for a bad turn: a gameplay
+// change, not a robustness fix.
+//
+// Safety: this runs on a goroutine while the main goroutine is mid-turn
+// mutating game state, and AutoSave removes the save file before
+// gob-encoding that live state. On HUP/TERM that risk is accepted
+// because the process is about to die regardless and a best-effort save
+// beats none. On INT/QUIT there is nothing to rescue, so the right
+// choice is the one with no corruption window at all.
+func savesOnSignal(sig os.Signal) bool {
+	return sig == syscall.SIGHUP || sig == syscall.SIGTERM
+}
+
+// installSignalHandlers arranges for the game to leave the terminal
+// usable when it is signalled: C's leave(), "leave quickly but
+// curteously" (main.c), extended with save.c auto_save on the two
+// signals that warrant it.
+func installSignalHandlers(g saver, t finisher) {
+	go leaveOnSignal(notifySignals(), g, t, os.Exit)
+}
+
+// notifySignals subscribes to the handled signals and returns the
+// channel they arrive on. Split out from installSignalHandlers so tests
+// can drive leaveOnSignal with real signal delivery.
+func notifySignals() chan os.Signal {
+	// Buffered so signal delivery never blocks, and deliberately never
+	// drained past the first signal: see leaveOnSignal.
 	sig := make(chan os.Signal, 1)
 
-	signal.Notify(sig, syscall.SIGHUP, syscall.SIGTERM)
+	signal.Notify(sig, handledSignals()...)
 
-	go func() {
+	return sig
-		<-sig
+}
+
+// leaveOnSignal waits for one signal and takes the game out.
+//
+// Exactly one goroutine reads exactly one signal, which is what makes
+// the exit safe: a second signal (a SIGINT landing while a SIGHUP's
+// AutoSave is still writing, say) stays in the buffer unread and can
+// never call exit out from under an in-flight save. The order within is
+// the same one myExit uses (game/rip.go): save if this signal saves,
+// then restore the terminal, then exit.
+func leaveOnSignal(sig <-chan os.Signal, g saver, t finisher, exit func(int)) {
+	if savesOnSignal(<-sig) {
 		g.AutoSave()
+	}
+
 	t.Fini()
-		os.Exit(0)
+	exit(0)
-	}()
 }
 
 // chooseSeed picks the dungeon number: SEED for reproducible dungeons

cmd/rogue/main_test.go

@@ -0,0 +1,222 @@
+package main
+
+// White-box tests for the signal plumbing. Unlike the game package's test
+// files this one carries no //nolint:testpackage directive: testpackage
+// exempts package main, so nolintlint rejects the directive as unused.
+
+import (
+	"os"
+	"os/signal"
+	"slices"
+	"strings"
+	"sync"
+	"syscall"
+	"testing"
+)
+
+// signalRecorder stands in for the game and the terminal in the signal
+// handler, recording the order of the steps the handler takes. The mutex
+// matters: the handler runs on its own goroutine, so an unguarded slice
+// would be a data race under -race, which is exactly what these tests
+// are meant to rule out.
+type signalRecorder struct {
+	mu    sync.Mutex
+	steps []string
+	code  int
+	done  chan struct{}
+}
+
+func newSignalRecorder() *signalRecorder {
+	return &signalRecorder{done: make(chan struct{})}
+}
+
+// AutoSave records a save attempt (the saver half).
+func (r *signalRecorder) AutoSave() {
+	r.record("save")
+}
+
+// Fini records a terminal restore (the finisher half).
+func (r *signalRecorder) Fini() {
+	r.record("fini")
+}
+
+// exit records the process exit that ends the handler and releases any
+// waiter. It stands in for os.Exit, which cannot be called in a test.
+func (r *signalRecorder) exit(code int) {
+	r.mu.Lock()
+	r.code = code
+	r.steps = append(r.steps, "exit")
+	r.mu.Unlock()
+
+	close(r.done)
+}
+
+// record appends one step.
+func (r *signalRecorder) record(step string) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	r.steps = append(r.steps, step)
+}
+
+// taken returns the recorded steps and the exit code.
+func (r *signalRecorder) taken() ([]string, int) {
+	r.mu.Lock()
+	defer r.mu.Unlock()
+
+	return slices.Clone(r.steps), r.code
+}
+
+// TestLeaveOnSignalRestoresTerminalBeforeExit is the core of issue #12:
+// whatever the signal, the terminal is restored before the process ends,
+// so the player is never dropped into a shell with the tty still in raw
+// mode.
+func TestLeaveOnSignalRestoresTerminalBeforeExit(t *testing.T) {
+	t.Parallel()
+
+	for _, sig := range handledSignals() {
+		rec := newSignalRecorder()
+
+		ch := make(chan os.Signal, 1)
+		ch <- sig
+
+		leaveOnSignal(ch, rec, rec, rec.exit)
+
+		steps, code := rec.taken()
+
+		fini := slices.Index(steps, "fini")
+		exit := slices.Index(steps, "exit")
+
+		if fini < 0 || exit < 0 || fini > exit {
+			t.Errorf("%v: want the terminal restored before exit, got %v",
+				sig, steps)
+		}
+
+		if code != 0 {
+			t.Errorf("%v: exit code = %d, want 0", sig, code)
+		}
+	}
+}
+
+// TestLeaveOnSignalSaveSplit pins the decision recorded on savesOnSignal:
+// SIGHUP/SIGTERM (involuntary teardown) save on the way out, SIGINT and
+// SIGQUIT (a deliberate "stop now" from the player) do not, matching C,
+// where auto_save is reserved for HUP/TERM and neither leave() nor quit()
+// nor endit() writes a save file.
+func TestLeaveOnSignalSaveSplit(t *testing.T) {
+	t.Parallel()
+
+	want := map[os.Signal][]string{
+		syscall.SIGHUP:  {"save", "fini", "exit"},
+		syscall.SIGTERM: {"save", "fini", "exit"},
+		syscall.SIGINT:  {"fini", "exit"},
+		syscall.SIGQUIT: {"fini", "exit"},
+	}
+
+	for _, sig := range handledSignals() {
+		rec := newSignalRecorder()
+
+		ch := make(chan os.Signal, 1)
+		ch <- sig
+
+		leaveOnSignal(ch, rec, rec, rec.exit)
+
+		steps, _ := rec.taken()
+		if !slices.Equal(steps, want[sig]) {
+			t.Errorf("%v: steps = %v, want %v", sig, steps, want[sig])
+		}
+
+		if saved := slices.Contains(steps, "save"); saved != savesOnSignal(sig) {
+			t.Errorf("%v: saved = %v, savesOnSignal = %v",
+				sig, saved, savesOnSignal(sig))
+		}
+	}
+}
+
+// TestLeaveOnSignalIgnoresLaterSignals covers the ordering guarantee in
+// leaveOnSignal's comment: only the first signal is read, so a second one
+// arriving mid-save cannot exit out from under the save and truncate the
+// player's file. The saver here blocks until a second signal has been
+// queued, reproducing that window.
+func TestLeaveOnSignalIgnoresLaterSignals(t *testing.T) {
+	t.Parallel()
+
+	rec := newSignalRecorder()
+
+	ch := make(chan os.Signal, 2)
+	ch <- syscall.SIGHUP
+
+	blocker := &blockingSaver{rec: rec, queue: ch, extra: syscall.SIGINT}
+
+	leaveOnSignal(ch, blocker, rec, rec.exit)
+
+	steps, _ := rec.taken()
+	if !slices.Equal(steps, []string{"save", "fini", "exit"}) {
+		t.Errorf("steps = %v, want one save, one fini, one exit", steps)
+	}
+
+	if len(ch) != 1 {
+		t.Errorf("queued signals left unread = %d, want 1", len(ch))
+	}
+}
+
+// blockingSaver queues another signal while the save is in flight, the
+// race window leaveOnSignal is built to close.
+type blockingSaver struct {
+	rec   *signalRecorder
+	queue chan os.Signal
+	extra os.Signal
+}
+
+// AutoSave delivers the extra signal mid-save, then records the save.
+func (b *blockingSaver) AutoSave() {
+	b.queue <- b.extra
+
+	b.rec.AutoSave()
+}
+
+// TestLeaveOnRealSignal is the deepest headless check available: it
+// delivers real SIGINT/SIGQUIT/SIGHUP/SIGTERM to this process through
+// os/signal, exactly as notifySignals wires them in the game, and
+// verifies each one reaches the handler and restores the terminal before
+// exiting.
+//
+// What cannot be checked here is the tty itself coming back out of raw
+// mode: that needs a controlling terminal and a live tcell screen, which
+// a headless test run does not have. This test covers everything up to
+// the Terminal.Fini call; term.Tcell.Fini is a direct pass-through to
+// tcell's Screen.Fini, which is the same call myExit already relies on.
+func TestLeaveOnRealSignal(t *testing.T) {
+	t.Parallel()
+
+	ch := notifySignals()
+	defer signal.Stop(ch)
+
+	for _, sig := range handledSignals() {
+		rec := newSignalRecorder()
+
+		go leaveOnSignal(ch, rec, rec, rec.exit)
+
+		unix, ok := sig.(syscall.Signal)
+		if !ok {
+			t.Fatalf("%v is not a unix signal", sig)
+		}
+
+		err := syscall.Kill(os.Getpid(), unix)
+		if err != nil {
+			t.Fatalf("kill(%v): %v", sig, err)
+		}
+
+		<-rec.done
+
+		steps, code := rec.taken()
+		if !strings.HasSuffix(strings.Join(steps, ","), "fini,exit") {
+			t.Errorf("%v: steps = %v, want the terminal restored before exit",
+				sig, steps)
+		}
+
+		if code != 0 {
+			t.Errorf("%v: exit code = %d, want 0", sig, code)
+		}
+	}
+}