fix(tui): paste protection for Termux char-by-char paste

internal/tui/model.go

@@ -192,6 +192,12 @@ type model struct {
 	// renders the live elapsed time from it so a long or stalled turn never looks
 	// like a frozen terminal (for ANY provider, not just slow ones). Zero = idle.
 	turnStartedAt time.Time
+	// lastCharTime tracks when the last non-Enter key was received, for paste detection.
+	lastCharTime time.Time
+	// lastKeyTime tracks every keypress timestamp for burst calculation.
+	lastKeyTime time.Time
+	// burstCount counts consecutive keypresses within 100ms (paste mode).
+	burstCount    int
 	queuedMessage string
 	// loops holds the session's active /loop definitions (see loop.go). activeLoopID
 	// tags the in-flight run when it is a loop iteration (empty = a user turn), so the
@@ -1175,6 +1181,18 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 		}
 		return m, nil
 	case tea.KeyPressMsg:
+		// Paste-detection timing trackers. MUST run before any early return
+		// so burst counting stays accurate regardless of which branch fires.
+		now := m.now()
+		if !m.lastKeyTime.IsZero() && now.Sub(m.lastKeyTime) < 100*time.Millisecond {
+			m.burstCount++
+		} else {
+			m.burstCount = 0
+		}
+		m.lastKeyTime = now
+		if !keyIs(msg, tea.KeyEnter) {
+			m.lastCharTime = now
+		}
 		if m.setup.visible {
 			return m.handleSetupKey(msg)
 		}
@@ -1202,6 +1220,7 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 			if keyText(msg) == "?" || keyText(msg) == "q" || keyIs(msg, tea.KeyEsc) || keyIs(msg, tea.KeyEnter) || keyCtrl(msg, 'c') {
 				m.helpOverlay = false
 			}
+			m.burstCount = 0
 			return m, nil
 		}
 		switch {
@@ -1286,6 +1305,7 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				return m.escapeAskUser()
 			}
 			if m.pendingSpecReview != nil {
+				m.burstCount = 0
 				return m.cancelSpecReview()
 			}
 			if m.pendingPermission != nil && m.pendingPermission.request.ToolName == tools.RequestPermissionsToolName {
@@ -1362,24 +1382,31 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 			if m.pendingPermission != nil {
 				// Enter confirms the highlighted option (default: allow once); the
 				// a/y/d hotkeys and a click still resolve directly.
+				m.burstCount = 0
 				return m.confirmPermissionCursor()
 			}
 			if m.pendingAskUser != nil {
+				m.burstCount = 0
 				return m.confirmAskUser()
 			}
 			if m.pendingSpecReview != nil {
+				m.burstCount = 0
 				return m, nil
 			}
 			if m.providerWizard != nil {
+				m.burstCount = 0
 				return m.handleProviderWizardKey(msg)
 			}
 			if m.mcpAddWizard != nil {
+				m.burstCount = 0
 				return m.handleMCPAddWizardKey(msg)
 			}
 			if m.mcpManager != nil {
+				m.burstCount = 0
 				return m.handleMCPManagerKey(msg)
 			}
 			if m.picker != nil {
+				m.burstCount = 0
 				return m.choosePicker()
 			}
 			if keyAlt(msg) || keyShift(msg) {
@@ -1394,6 +1421,32 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 			if m.suggestionsActive() {
 				return m.chooseSuggestion()
 			}
+			// Timing-based paste protection: under Termux, context-menu paste
+			// injects characters one at a time (including newlines as raw
+			// KeyEnter events). A sustained burst of 3+ keys within 100ms
+			// means we are inside a char-by-char paste — insert newline
+			// instead of submitting. Gated to Termux so fast desktop typing
+			// (which can reach similar inter-key intervals) is never affected.
+			if os.Getenv("TERMUX_VERSION") != "" && m.burstCount > 2 {
+				state := m.currentComposerState()
+				m = m.insertComposerTextWithPastePreview(state, "\n", "")
+				m.clearSuggestions()
+				return m, nil
+			}
+
+			// Composer-based paste protection: when the composer already has
+			// multiline text (e.g. pasted via bracketed paste / Ctrl+Shift+V),
+			// plain Enter inserts a newline instead of submitting so each
+			// pasted \n does not trigger a premature submit. Uses the same
+			// burstCount > 2 threshold as the Termux path so a single fast
+			// key + Enter on a multiline prompt still submits.
+			if m.composerActive && m.burstCount > 2 && strings.Contains(m.composer.text, "\n") {
+				state := m.currentComposerState()
+				m = m.insertComposerTextWithPastePreview(state, "\n", "")
+				m.clearSuggestions()
+				return m, nil
+			}
+			m.burstCount = 0
 			return m.handleSubmit()
 		case keyIs(msg, tea.KeyTab) && keyShift(msg):
 			if m.transcriptDetailed {
@@ -1494,12 +1547,15 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				return m.moveAskUserTab(1), nil
 			}
 			if m.providerWizard != nil {
+				m.burstCount = 0
 				return m.handleProviderWizardKey(msg)
 			}
 			if m.mcpAddWizard != nil {
+				m.burstCount = 0
 				return m.handleMCPAddWizardKey(msg)
 			}
 			if m.mcpManager != nil {
+				m.burstCount = 0
 				return m.handleMCPManagerKey(msg)
 			}
 			if m.picker == nil && m.suggestionsActive() {
@@ -1525,12 +1581,15 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				return m.moveAskUserCursor(-1), nil
 			}
 			if m.providerWizard != nil {
+				m.burstCount = 0
 				return m.handleProviderWizardKey(msg)
 			}
 			if m.mcpAddWizard != nil {
+				m.burstCount = 0
 				return m.handleMCPAddWizardKey(msg)
 			}
 			if m.mcpManager != nil {
+				m.burstCount = 0
 				return m.handleMCPManagerKey(msg)
 			}
 			if m.picker != nil {
@@ -1561,12 +1620,15 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				return m.moveAskUserCursor(1), nil
 			}
 			if m.providerWizard != nil {
+				m.burstCount = 0
 				return m.handleProviderWizardKey(msg)
 			}
 			if m.mcpAddWizard != nil {
+				m.burstCount = 0
 				return m.handleMCPAddWizardKey(msg)
 			}
 			if m.mcpManager != nil {
+				m.burstCount = 0
 				return m.handleMCPManagerKey(msg)
 			}
 			if m.picker != nil {
@@ -1596,12 +1658,15 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				return m.moveAskUserCursor(1), nil
 			}
 			if m.providerWizard != nil {
+				m.burstCount = 0
 				return m.handleProviderWizardKey(msg)
 			}
 			if m.mcpAddWizard != nil {
+				m.burstCount = 0
 				return m.handleMCPAddWizardKey(msg)
 			}
 			if m.mcpManager != nil {
+				m.burstCount = 0
 				return m.handleMCPManagerKey(msg)
 			}
 			if m.picker != nil {
@@ -1639,12 +1704,15 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				return m.moveAskUserCursor(-1), nil
 			}
 			if m.providerWizard != nil {
+				m.burstCount = 0
 				return m.handleProviderWizardKey(msg)
 			}
 			if m.mcpAddWizard != nil {
+				m.burstCount = 0
 				return m.handleMCPAddWizardKey(msg)
 			}
 			if m.mcpManager != nil {
+				m.burstCount = 0
 				return m.handleMCPManagerKey(msg)
 			}
 			if m.picker != nil {
@@ -1730,18 +1798,23 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 			return m, nil // picker mode: non-navigation keys do nothing
 		}
 		if m.pendingSpecReview != nil {
+			m.burstCount = 0
 			return m.handleSpecReviewKey(msg)
 		}
 		if m.pendingPermission != nil {
+			m.burstCount = 0
 			return m.handlePermissionKey(msg)
 		}
 		if m.providerWizard != nil {
+			m.burstCount = 0
 			return m.handleProviderWizardKey(msg)
 		}
 		if m.mcpAddWizard != nil {
+			m.burstCount = 0
 			return m.handleMCPAddWizardKey(msg)
 		}
 		if m.mcpManager != nil {
+			m.burstCount = 0
 			return m.handleMCPManagerKey(msg)
 		}
 		// An open picker is modal over the input: swallow remaining keys so they

internal/tui/model_test.go

@@ -123,6 +123,7 @@ func TestPromptSubmitStoresReasoningSeparatelyFromAnswer(t *testing.T) {
 	})
 	base := time.Date(2026, 6, 14, 10, 0, 0, 0, time.UTC)
 	times := []time.Time{
+		base, // burst tracker on Enter keypress (timing-based paste guard)
 		base, // run start: consumed by turnStartedAt (the working-line elapsed clock)
 		base,
 		base.Add(1 * time.Second),
@@ -2675,3 +2676,139 @@ func TestOverlayViewportLinesCompositesAndPreservesBackdropText(t *testing.T) {
 		t.Fatalf("overlaid row should keep backdrop margin text alongside the panel, got %q", panelRow)
 	}
 }
+
+// burstTestModel creates a model with fake provider, advancing clock (60ms/tick),
+// and empty composer for burst/paste testing. termuxVersion controls the env var.
+func burstTestModel(t *testing.T, termuxVersion string) model {
+	t.Setenv("XDG_DATA_HOME", t.TempDir())
+	t.Setenv("TERMUX_VERSION", termuxVersion)
+	provider := &fakeProvider{events: []zeroruntime.StreamEvent{
+		{Type: zeroruntime.StreamEventText, Content: "ok"},
+		{Type: zeroruntime.StreamEventDone},
+	}}
+	m := newModel(context.Background(), Options{
+		Cwd:          t.TempDir(),
+		ProviderName: "tokenrouter",
+		ModelName:    "MiniMax-M3",
+		Provider:     provider,
+		Registry:     tools.NewRegistry(),
+	})
+	base := time.Date(2026, 7, 7, 12, 0, 0, 0, time.UTC)
+	tick := 0
+	m.now = func() time.Time {
+		tick++
+		return base.Add(time.Duration(tick) * 60 * time.Millisecond)
+	}
+	m.input.SetValue("")
+	m.width = 100
+	m.height = 30
+	return m
+}
+
+// typeKeys simulates rapid keypresses into the model, returning the final state.
+func typeKeys(m model, keys string) model {
+	for _, ch := range keys {
+		updated, _ := m.Update(testKeyText(string(ch)))
+		m = updated.(model)
+	}
+	return m
+}
+
+// TestTermuxBurstInsertsNewline: under Termux, 3+ rapid chars + Enter inserts newline.
+func TestTermuxBurstInsertsNewline(t *testing.T) {
+	m := burstTestModel(t, "v0.118.0")
+	m = typeKeys(m, "abc")
+	updated, _ := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if m.pending {
+		t.Fatal("burst should insert newline, not submit")
+	}
+	if !strings.Contains(m.composerValue(), "\n") {
+		t.Fatalf("burst should insert newline into composer, got %q", m.composerValue())
+	}
+}
+
+// TestTermuxFastTypingSubmits: under Termux, 2 fast chars + Enter still submits.
+func TestTermuxFastTypingSubmits(t *testing.T) {
+	m := burstTestModel(t, "v0.118.0")
+	m = typeKeys(m, "ab")
+	updated, cmd := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if !m.pending {
+		t.Fatal("fast typing should be pending after submit")
+	}
+	if cmd == nil {
+		t.Fatal("fast typing should submit, got nil cmd")
+	}
+}
+
+// TestDesktopBurstNotAffected: on desktop (no TERMUX_VERSION), 3 fast chars + Enter submits.
+func TestDesktopBurstNotAffected(t *testing.T) {
+	m := burstTestModel(t, "")
+	m = typeKeys(m, "abc")
+	updated, cmd := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if !m.pending {
+		t.Fatal("desktop burst should be pending after submit")
+	}
+	if cmd == nil {
+		t.Fatal("desktop burst should submit, got nil cmd")
+	}
+}
+
+// TestBurstResetAfterSubmit: after submit, burstCount is reset so normal
+// typing (2 chars + Enter) still submits without false newline insertion.
+func TestBurstResetAfterSubmit(t *testing.T) {
+	m := burstTestModel(t, "v0.118.0")
+	// Type and submit normally
+	m = typeKeys(m, "hi")
+	updated, cmd := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if cmd == nil {
+		t.Fatal("first submit should start a run")
+	}
+	// Process the agent response so the model is no longer pending
+	resp, _ := m.Update(execCmd(cmd))
+	m = resp.(model)
+	if m.pending {
+		t.Fatal("model should not be pending after agent response")
+	}
+
+	// Reset lastKeyTime so the burst tracker sees a clean gap before the
+	// second round of typing — avoids coupling to fake-clock progression.
+	m.lastKeyTime = time.Time{}
+
+	// After reset, 2 fast chars + Enter should still submit (burstCount < 3)
+	m = typeKeys(m, "ok")
+	updated, cmd = m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if !m.pending {
+		t.Fatal("after burst reset, fast typing should submit")
+	}
+	if cmd == nil {
+		t.Fatal("after burst reset, got nil cmd")
+	}
+}
+
+// TestMultilineBurstSubmits: with a \n already in the composer, a 2-char
+// burst + Enter on desktop should still submit (burstCount < 3), not
+// insert another newline.
+func TestMultilineBurstSubmits(t *testing.T) {
+	m := burstTestModel(t, "")
+	// Seed the composer with multiline text via applyComposerKey
+	m.composerActive = true
+	m.composer.text = "hello\nwor"
+	m.composer.cursor = len([]rune(m.composer.text))
+	m.input.SetValue(m.composer.text)
+
+	// Type "ld" fast (2 chars) then Enter
+	m = typeKeys(m, "ld")
+	updated, cmd := m.Update(testKey(tea.KeyEnter))
+	m = updated.(model)
+	if !m.pending {
+		t.Fatal("multiline burst should submit, not insert newline")
+	}
+	if cmd == nil {
+		t.Fatal("multiline burst got nil cmd")
+	}
+}