fix(ui): stop the install progress bar from garbling non-scroll-region terminals

docs/HARNESS.md

@@ -109,11 +109,16 @@ it survives doc rot.
   the in-session loop (Step 8), the sensor became dead code and was
   removed. If `--auto` ever comes back, the sensor needs to come back
   with it.
-- **No archtest rule for scroll-region usage.** `internal/ui/scrollregion.go`
-  detects support at runtime (`TERM`, TTY, terminal height) and falls back
-  to the inline `\r\033[K` renderer when unavailable. A static rule can't
-  see runtime terminal capabilities, so this stays a runtime concern. The
-  fallback is covered by `TestStickyProgressFallsBackWhenScrollRegionUnsupported`.
+- **No terminal scroll-region rendering.** StickyProgress once reserved the
+  bottom rows via a DECSTBM scroll region (`internal/ui/scrollregion.go`,
+  since removed) to keep a "sticky" status bar frozen while the log scrolled.
+  It rendered correctly only on terminals that fully honour scroll regions;
+  on ones that report a normal `TERM` but don't (e.g. some GPU/block
+  terminals), the reserved bar was dragged into the log and reprinted on
+  every tick, so the install read as garbage. Runtime detection couldn't tell
+  the two apart from `TERM`/TTY/height alone. It now draws a plain in-place
+  `\r\033[K` status line that trails top-to-bottom output on every terminal.
+  Don't reintroduce the scroll region.
 - **L4 runs on GitHub Actions, not a self-hosted runner.** `macos-14`
   runners are Apple Silicon VMs — each job gets a fresh clean macOS
   environment, which is exactly what L4 needs. Tart is no longer required.

internal/ui/AGENTS.md

@@ -8,9 +8,8 @@ live in the `tui/` subpackage.
 | File | Lines | Purpose |
 |------|-------|---------|
 | `ui.go` | 247 | Base styles, color helpers, output helpers (Header/Success/Error/Info/Warn/Muted/DryRun*), huh form wrappers (InputGitConfig, SelectPreset, Confirm, SelectOption, Input) |
-| `progress.go` | 246 | StickyProgress: per-package timing, succeeded/failed/skipped counters |
+| `progress.go` | 245 | StickyProgress: per-package timing, succeeded/failed/skipped counters, in-place status line |
 | `scanprogress.go` | 221 | ScanProgress: step timing, overall counter `[3/8]` |
-| `scrollregion.go` | 143 | ANSI scroll-region plumbing for StickyProgress |
 
 ## FILES (internal/ui/tui/)
 

internal/ui/progress.go

@@ -39,9 +39,6 @@ type StickyProgress struct {
 	succeeded  int
 	failed     int
 	skipped    int
-
-	// Scroll region rendering (nil when terminal doesn't support it).
-	region *ScrollRegion
 }
 
 var spinnerFrames = []string{"⠋", "⠙", "⠹", "⠸", "⠼", "⠴", "⠦", "⠧", "⠇", "⠏"}
@@ -58,10 +55,6 @@ func (sp *StickyProgress) Start() {
 	sp.mu.Lock()
 	sp.active = true
 	sp.startTime = time.Now()
-	if IsScrollRegionSupported() {
-		sp.region = NewScrollRegion(2)
-		sp.region.Start()
-	}
 	sp.mu.Unlock()
 
 	signal.Stop(sp.sigCh)
@@ -90,16 +83,19 @@ func (sp *StickyProgress) Start() {
 	}()
 }
 
+// render draws the live status line in place: carriage-return to the start of
+// the current line, clear it, then write the spinner, progress count, current
+// package, and elapsed time. It writes no newline, so PrintLine's completed
+// rows scroll above it and this line trails the output.
+//
+// This deliberately does NOT reserve a "sticky" bottom bar via a terminal
+// scroll region (DECSTBM). That looked nicer where it worked, but it silently
+// corrupted on terminals that report a normal TERM yet don't honour scroll
+// regions — the reserved bar got dragged into the log and reprinted on every
+// tick, so the install read as garbage. A plain in-place status line renders
+// top-to-bottom on every terminal, which is the property that matters for a
+// one-shot install log. Don't reintroduce the scroll region.
 func (sp *StickyProgress) render() {
-	if sp.region != nil {
-		sp.region.DrawBottom(sp.formatLines())
-		return
-	}
-	sp.renderInline()
-}
-
-// renderInline is the fallback renderer used when scroll region is unavailable.
-func (sp *StickyProgress) renderInline() {
 	spinner := spinnerFrames[sp.spinnerIdx]
 	pkg := truncate(sp.currentPkg, 20)
 	elapsed := sp.pkgElapsed()
@@ -111,27 +107,6 @@ func (sp *StickyProgress) renderInline() {
 		etaStyle.Render(elapsed))
 }
 
-// formatLines returns the two strings to render in the bottom-reserved scroll
-// region: a divider and a status line.
-func (sp *StickyProgress) formatLines() []string {
-	cols := 80
-	if sp.region != nil {
-		cols = sp.region.Cols()
-	}
-
-	spinner := spinnerFrames[sp.spinnerIdx]
-	pkg := truncate(sp.currentPkg, 20)
-	elapsed := sp.pkgElapsed()
-
-	divider := strings.Repeat("─", cols)
-	status := fmt.Sprintf("%s %s %s   %s",
-		spinner,
-		progressTextStyle.Render(fmt.Sprintf("[%d/%d]", sp.completed+1, sp.total)),
-		currentPkgStyle.Render(pkg),
-		etaStyle.Render(elapsed))
-	return []string{divider, status}
-}
-
 // pkgElapsed returns elapsed seconds for the current package, or "" if not yet started.
 func (sp *StickyProgress) pkgElapsed() string {
 	if sp.pkgStart.IsZero() {
@@ -217,12 +192,7 @@ func (sp *StickyProgress) onInterrupt() (force bool) {
 	}
 	sp.aborting = true
 	sp.active = false
-	if sp.region != nil {
-		sp.region.Stop()
-		sp.region = nil
-	} else {
-		fmt.Printf("\r\033[K")
-	}
+	fmt.Printf("\r\033[K")
 	fmt.Println(mutedStyle.Render("  aborting — waiting for the current step to stop · ctrl+c again to force quit"))
 	return false
 }
@@ -233,12 +203,7 @@ func (sp *StickyProgress) Finish() {
 	sp.mu.Lock()
 	defer sp.mu.Unlock()
 	sp.active = false
-	if sp.region != nil {
-		sp.region.Stop()
-		sp.region = nil
-	} else {
-		fmt.Printf("\r\033[K")
-	}
+	fmt.Printf("\r\033[K")
 
 	elapsed := time.Since(sp.startTime)
 

internal/ui/progress_test.go

@@ -159,16 +159,18 @@ func TestStickyProgressPkgElapsed(t *testing.T) {
 	assert.Contains(t, elapsed, "s")
 }
 
-func TestStickyProgressFallsBackWhenScrollRegionUnsupported(t *testing.T) {
+func TestStickyProgressStartFinishDoNotPanic(t *testing.T) {
+	// The renderer no longer reserves a scroll region — it draws a plain
+	// in-place status line that works on every terminal. Start/Finish must run
+	// cleanly regardless of TERM (here a dumb terminal that supports nothing).
 	t.Setenv("TERM", "dumb")
 	sp := NewStickyProgress(3)
-	sp.Start()
-	defer sp.Finish()
-	// Region should NOT have been attached.
-	sp.mu.Lock()
-	hasRegion := sp.region != nil
-	sp.mu.Unlock()
-	assert.False(t, hasRegion, "scroll region should be disabled on dumb TERM")
+	assert.NotPanics(t, func() {
+		sp.Start()
+		sp.SetCurrent("wget")
+		sp.IncrementWithStatus(true)
+		sp.Finish()
+	})
 }
 
 // Ctrl+C during a linear install must not exit from the progress goroutine: