fix(tui): address FILES sidebar review findings

Review fixes for the FILES panel / drill-in / git sweep:

- touchedFiles: split multi-file diffs per file (perFileDiffStats) so an
  apply_patch spanning several files no longer charges the whole patch's
  +/- totals to every file it touched; order by lastRowIndex descending
  so a re-touched file lists first (reversing first-seen order kept it in
  its original slot).
- sidebarFileLines: filter the live-writing row out before computing the
  "+N more" trailer so the skipped entry no longer inflates the count.
- git sweep: run `git diff --numstat -z` and parse the NUL-terminated
  rename records (counts + preimage + postimage) — plain --numstat
  brace-mangles renamed paths ("src/{old => new}"), so their diffstat
  never matched a porcelain path and renamed files stayed at 0/0;
  gitTouchedFiles now yields newest detection first to match the
  roster's ordering.
- file view: stream the full-mode read and stop at fileViewMaxLines
  (os.ReadFile loaded a multi-GB file wholesale before truncating — the
  exact freeze the cap exists to prevent); re-opening the file already
  being viewed is a no-op so a stray re-click can't bounce full mode
  back to diff or reset scroll; skip sub-4-char lines in the changed-line
  markers so common braces/returns don't mark unrelated occurrences.
- keys: gate the drill-in's d/f and Esc handling on noBlockingModal so a
  permission prompt / ask-user / wizard keeps its own key handling.
- sidebar: a live in-flight write counts as content, so the FILES pulse
  shows for the session's first mutation.
- tests: numstat test now feeds real -z record shapes and asserts the
  rename postimage key; new coverage for per-file stats, re-touch
  ordering, live-row overflow, same-file reopen, truncation, modal
  gating, live-write content, and a real-repo rename sweep.

internal/tui/file_view.go

@@ -0,0 +1,251 @@
+// file_view.go is the drill-in view for a touched file, opened from the FILES
+// sidebar section (files_panel.go). It reuses the subchat pattern: while
+// active, the chat column's body swaps to this file's content — the sidebar,
+// composer, and scroll engine keep working unchanged (transcriptBodyItems is
+// the single source the viewport, renderer, and hit-testers all read, so
+// swapping there keeps every consumer consistent). Two modes:
+//
+//	diff (default) — the file's edit cards from this session, full-depth
+//	full           — the file as it stands on disk, syntax highlighted, with
+//	                 gutter markers on the lines this session's diffs added
+//
+// d/f switch modes (with an empty composer), Esc returns to the chat at the
+// scroll position it was left at.
+package tui
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+)
+
+// fileViewMaxLines caps the full-file mode so a giant generated file can't
+// freeze a render; the tail collapses into a "… N more lines" trailer.
+const fileViewMaxLines = 4000
+
+const (
+	fileViewDiff = iota
+	fileViewFull
+)
+
+// fileViewState manages the drill-in view for a touched file. When active, the
+// transcript body swaps to the file's diff/content instead of the chat rows.
+type fileViewState struct {
+	active bool
+	path   string // workspace-relative, as carried by changedFiles
+	mode   int    // fileViewDiff | fileViewFull
+	// parentScrollOffset preserves the chat scroll position so closing the view
+	// returns to the same spot (mirrors subchatState).
+	parentScrollOffset int
+}
+
+// openFileView activates the drill-in for path in diff mode. Opening from an
+// already-open view (clicking another FILES row) keeps the original saved chat
+// scroll position rather than saving the file view's own offset as "parent".
+// Re-opening the file that is ALREADY being viewed is a no-op: a stray
+// re-click must not bounce the user from full mode back to diff or reset
+// their scroll position.
+func (m model) openFileView(path string) model {
+	if m.fileView.active && m.fileView.path == path {
+		return m
+	}
+	if !m.fileView.active {
+		m.fileView.parentScrollOffset = m.chatScrollOffset
+	}
+	m.fileView.active = true
+	m.fileView.path = path
+	m.fileView.mode = fileViewDiff
+	// A file only the git sweep knows about (bash/subagent mutation) has no edit
+	// cards to stack — open straight on the full file instead of a placeholder.
+	if len(m.fileViewResultRows()) == 0 {
+		m.fileView.mode = fileViewFull
+	}
+	m.chatScrollOffset = 0
+	m = m.clearHover() // bodyY numbering differs between the file body and the chat
+	return m
+}
+
+// exitFileView deactivates the view and restores the chat scroll position.
+func (m model) exitFileView() model {
+	if !m.fileView.active {
+		return m
+	}
+	m.chatScrollOffset = m.fileView.parentScrollOffset
+	m.fileView = fileViewState{}
+	m = m.clearHover()
+	return m
+}
+
+// setFileViewMode switches diff/full, resetting the scroll to the bottom-anchored
+// start since the two bodies have unrelated heights.
+func (m model) setFileViewMode(mode int) model {
+	if !m.fileView.active || m.fileView.mode == mode {
+		return m
+	}
+	m.fileView.mode = mode
+	m.chatScrollOffset = 0
+	return m
+}
+
+// fileViewNavBar renders the single-line header shown in place of the pinned
+// title bar while the view is active: the path plus the key hints. One line
+// exactly, so every scrollableTranscriptFrame computed against it agrees with
+// the title bar's geometry.
+func (m model) fileViewNavBar(width int) string {
+	mode := "diff"
+	other := "f full"
+	if m.fileView.mode == fileViewFull {
+		mode = "full"
+		other = "d diff"
+	}
+	left := zeroTheme.accent.Render("← "+truncatePathLeft(m.fileView.path, maxInt(8, width/2))) +
+		zeroTheme.faint.Render("  ·  "+mode)
+	right := zeroTheme.faint.Render(other + " · esc back")
+	return fitStyledLine(joinHeaderLine(left, right, width), width)
+}
+
+// fileViewBodyItems builds the body items the transcript machinery renders
+// while the view is active — one pre-rendered block, so scrolling and height
+// accounting flow through the exact same path as chat rows.
+func (m model) fileViewBodyItems(width int) []transcriptBodyItem {
+	var block string
+	if m.fileView.mode == fileViewFull {
+		block = m.renderFileViewFull(width)
+	} else {
+		block = m.renderFileViewDiff(width)
+	}
+	return []transcriptBodyItem{transcriptBlockBodyItem(transcriptBodyItemRow, -1, block)}
+}
+
+// fileViewResultRows returns the transcript's tool-result rows that touched the
+// viewed file, in chronological order.
+func (m model) fileViewResultRows() []transcriptRow {
+	var rows []transcriptRow
+	for _, row := range m.transcript {
+		if row.kind != rowToolResult {
+			continue
+		}
+		for _, p := range row.changedFiles {
+			if p == m.fileView.path {
+				rows = append(rows, row)
+				break
+			}
+		}
+	}
+	return rows
+}
+
+// renderFileViewDiff renders the session's edits to the file as its full-depth
+// tool cards (bodyCap 0, the detailed-view depth), stacked chronologically —
+// the same cards the chat shows, so the diffs read identically in both places.
+func (m model) renderFileViewDiff(width int) string {
+	rows := m.fileViewResultRows()
+	if len(rows) == 0 {
+		return zeroTheme.faint.Render("No recorded edits for this file in this session.")
+	}
+	rc := buildRowContext(m.transcript)
+	opts := cardRenderOptions{bodyCap: 0, cwd: m.cwd}
+	var b strings.Builder
+	for i, row := range rows {
+		if i > 0 {
+			b.WriteString("\n\n")
+		}
+		if len(rows) > 1 {
+			b.WriteString(zeroTheme.faint.Render(fmt.Sprintf("edit %d of %d", i+1, len(rows))))
+			b.WriteString("\n")
+		}
+		b.WriteString(m.renderRowModeUncached(row, width, rc, opts))
+	}
+	return b.String()
+}
+
+// renderFileViewFull renders the file as it currently stands on disk, syntax
+// highlighted, with a line-number gutter and an accent ▎ marker on the lines
+// this session's diffs added (matched by exact text — an approximation that
+// tolerates later drift; a stale marker just doesn't highlight).
+func (m model) renderFileViewFull(width int) string {
+	target := m.fileView.path
+	if !filepath.IsAbs(target) {
+		target = filepath.Join(m.cwd, target)
+	}
+	// Stream the read and stop at the cap: os.ReadFile would load a multi-GB
+	// file wholesale before any truncation, which is the exact render freeze
+	// fileViewMaxLines exists to prevent.
+	file, err := os.Open(target)
+	if err != nil {
+		return zeroTheme.faint.Render("Could not read file: " + err.Error())
+	}
+	defer file.Close()
+	var lines []string
+	truncated := false
+	scanner := bufio.NewScanner(file)
+	scanner.Buffer(make([]byte, 0, 64*1024), 16*1024*1024)
+	for scanner.Scan() {
+		if len(lines) == fileViewMaxLines {
+			truncated = true
+			break
+		}
+		lines = append(lines, scanner.Text())
+	}
+	if err := scanner.Err(); err != nil {
+		if len(lines) == 0 {
+			return zeroTheme.faint.Render("Could not read file: " + err.Error())
+		}
+		truncated = true // e.g. a single over-long line mid-file: show what we have
+	}
+
+	changed := m.fileViewChangedLines()
+	gutterW := len(fmt.Sprintf("%d", len(lines)))
+	textBudget := maxInt(8, width-gutterW-3) // gutter + space + marker column
+	// Highlight with an effectively-infinite measure so the highlighter never
+	// wraps — output lines stay 1:1 with file lines and the gutter numbering
+	// can't desync. Each line is then truncated to the column budget below.
+	display, ok := highlightCodeForPath(lines, m.fileView.path, 1<<20, nil)
+	if !ok || len(display) != len(lines) {
+		display = lines // no lexer for this path: render plain
+	}
+
+	var b strings.Builder
+	for i, line := range display {
+		line = fitStyledLine(line, textBudget)
+		if i > 0 {
+			b.WriteString("\n")
+		}
+		marker := " "
+		if changed[strings.TrimSpace(lines[i])] {
+			marker = zeroTheme.accent.Render("▎")
+		}
+		b.WriteString(zeroTheme.faintest.Render(fmt.Sprintf("%*d ", gutterW, i+1)))
+		b.WriteString(marker)
+		b.WriteString(line)
+	}
+	if truncated {
+		// No exact remaining-line count: computing one would require reading the
+		// rest of the file, defeating the bounded read above.
+		b.WriteString("\n")
+		b.WriteString(zeroTheme.faint.Render(fmt.Sprintf("… more lines (file truncated at %d for display)", len(lines))))
+	}
+	return b.String()
+}
+
+// fileViewChangedLines collects the trimmed text of every line the session's
+// diffs ADDED to the viewed file, for the full-mode gutter markers. Very short
+// lines ("}", "return", ")") are skipped: text-matching them would mark every
+// unrelated occurrence across the file, which misleads far more than a missing
+// marker on a brace line ever could.
+func (m model) fileViewChangedLines() map[string]bool {
+	changed := map[string]bool{}
+	for _, row := range m.fileViewResultRows() {
+		for _, line := range strings.Split(row.detail, "\n") {
+			if !strings.HasPrefix(line, "+") || strings.HasPrefix(line, "+++") {
+				continue
+			}
+			if text := strings.TrimSpace(strings.TrimPrefix(line, "+")); len(text) >= 4 {
+				changed[text] = true
+			}
+		}
+	}
+	return changed
+}

internal/tui/file_view_test.go

@@ -0,0 +1,288 @@
+package tui
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"path/filepath"
+	"strings"
+	"testing"
+
+	tea "charm.land/bubbletea/v2"
+
+	"github.com/Gitlawb/zero/internal/agent"
+	"github.com/Gitlawb/zero/internal/sessions"
+	"github.com/Gitlawb/zero/internal/tools"
+)
+
+// TestFileViewOpenExitRestoresScroll: opening saves the chat scroll position,
+// resets it for the file body, and Esc restores it; switching files while open
+// keeps the ORIGINAL saved position (not the file view's own).
+func TestFileViewOpenExitRestoresScroll(t *testing.T) {
+	m := filesPanelTestModel()
+	m.chatScrollOffset = 12
+
+	m = m.openFileView("web/app.js")
+	if !m.fileView.active || m.fileView.mode != fileViewDiff {
+		t.Fatalf("open should activate in diff mode: %+v", m.fileView)
+	}
+	if m.chatScrollOffset != 0 || m.fileView.parentScrollOffset != 12 {
+		t.Fatalf("open should reset scroll and save the parent offset: offset=%d saved=%d", m.chatScrollOffset, m.fileView.parentScrollOffset)
+	}
+
+	m.chatScrollOffset = 5 // scrolled within the file body
+	m = m.openFileView("internal/tui/sidebar.go")
+	if m.fileView.parentScrollOffset != 12 {
+		t.Fatalf("switching files must keep the original parent offset, got %d", m.fileView.parentScrollOffset)
+	}
+
+	m = m.exitFileView()
+	if m.fileView.active || m.chatScrollOffset != 12 {
+		t.Fatalf("exit should restore the chat scroll: active=%v offset=%d", m.fileView.active, m.chatScrollOffset)
+	}
+}
+
+// TestFileViewEscAndModeKeys: Esc exits the view via the model's key handler;
+// d/f switch modes while the composer is empty and never while typing.
+func TestFileViewEscAndModeKeys(t *testing.T) {
+	m := filesPanelTestModel()
+	m = m.openFileView("web/app.js")
+
+	updated, _ := m.Update(tea.KeyPressMsg{Code: 'f', Text: "f"})
+	m = updated.(model)
+	if m.fileView.mode != fileViewFull {
+		t.Fatal("f should switch to full mode")
+	}
+	updated, _ = m.Update(tea.KeyPressMsg{Code: 'd', Text: "d"})
+	m = updated.(model)
+	if m.fileView.mode != fileViewDiff {
+		t.Fatal("d should switch back to diff mode")
+	}
+
+	// With text in the composer, d/f type as normal characters.
+	m.input.SetValue("say")
+	updated, _ = m.Update(tea.KeyPressMsg{Code: 'f', Text: "f"})
+	m = updated.(model)
+	if m.fileView.mode != fileViewDiff {
+		t.Fatal("f while typing must not hijack the composer")
+	}
+	m.input.SetValue("")
+
+	updated, _ = m.Update(tea.KeyPressMsg{Code: tea.KeyEsc})
+	m = updated.(model)
+	if m.fileView.active {
+		t.Fatal("Esc should exit the file view")
+	}
+}
+
+// TestFileViewDiffBody: diff mode stacks the file's edit cards chronologically
+// with "edit N of M" labels; a file with no recorded edits shows the quiet
+// placeholder.
+func TestFileViewDiffBody(t *testing.T) {
+	m := filesPanelTestModel()
+	m = m.openFileView("internal/tui/sidebar.go")
+	body := plainRender(t, m.renderFileViewDiff(78))
+	if !strings.Contains(body, "edit 1 of 2") || !strings.Contains(body, "edit 2 of 2") {
+		t.Fatalf("expected chronological edit labels:\n%s", body)
+	}
+	if !strings.Contains(body, "added one") || !strings.Contains(body, "three") {
+		t.Errorf("expected both diffs' content:\n%s", body)
+	}
+
+	m.fileView.path = "never/touched.go"
+	if got := plainRender(t, m.renderFileViewDiff(78)); !strings.Contains(got, "No recorded edits") {
+		t.Errorf("untouched file should show the placeholder, got:\n%s", got)
+	}
+}
+
+// TestFileViewFullBody: full mode shows the on-disk content with line numbers
+// and marks session-added lines with the gutter marker; a missing file degrades
+// to a readable error line.
+func TestFileViewFullBody(t *testing.T) {
+	dir := t.TempDir()
+	if err := os.WriteFile(filepath.Join(dir, "app.js"), []byte("let a = 1\nlet untouched = 0\n"), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	m := filesPanelTestModel()
+	m.cwd = dir
+	m.transcript = append(m.transcript, transcriptRow{
+		kind: rowToolResult, tool: "write_file", id: "w9", status: tools.StatusOK,
+		detail:       "+let a = 1",
+		changedFiles: []string{"app.js"},
+	})
+	m = m.openFileView("app.js")
+	m = m.setFileViewMode(fileViewFull)
+
+	body := m.renderFileViewFull(78)
+	plain := plainRender(t, body)
+	if !strings.Contains(plain, "1 ") || !strings.Contains(plain, "let untouched = 0") {
+		t.Fatalf("full view should show numbered file content:\n%s", plain)
+	}
+	lines := strings.Split(plain, "\n")
+	if len(lines) != 2 {
+		t.Fatalf("one rendered line per file line, got %d:\n%s", len(lines), plain)
+	}
+	if !strings.Contains(lines[0], "▎") {
+		t.Errorf("session-added line should carry the gutter marker: %q", lines[0])
+	}
+	if strings.Contains(lines[1], "▎") {
+		t.Errorf("untouched line must not carry the marker: %q", lines[1])
+	}
+
+	m.fileView.path = "gone.js"
+	if got := plainRender(t, m.renderFileViewFull(78)); !strings.Contains(got, "Could not read file") {
+		t.Errorf("missing file should degrade to an error line, got:\n%s", got)
+	}
+}
+
+// TestFileViewSwapsTranscriptBody: while active, transcriptBodyItems returns
+// the file body (a single block) instead of the chat rows, and the pinned
+// title bar swaps to the one-line nav bar — the geometry every frame consumer
+// relies on.
+func TestFileViewSwapsTranscriptBody(t *testing.T) {
+	m := filesPanelTestModel()
+	m = m.openFileView("internal/tui/sidebar.go")
+
+	items := m.transcriptBodyItems(m.chatColumnWidth(), "")
+	if len(items) != 1 {
+		t.Fatalf("file view should swap the body to a single block item, got %d items", len(items))
+	}
+	nav := plainRender(t, m.pinnedTitleBar(m.chatColumnWidth()))
+	if !strings.Contains(nav, "sidebar.go") || !strings.Contains(nav, "esc back") {
+		t.Fatalf("nav bar should show the path and key hints: %q", nav)
+	}
+	if lines := len(viewLines(m.fileViewNavBar(m.chatColumnWidth()))); lines != 1 {
+		t.Fatalf("nav bar must be exactly one line (title-bar geometry), got %d", lines)
+	}
+
+	// The whole view renders without panicking in both modes and shows the nav.
+	if view := plainRender(t, m.transcriptView()); !strings.Contains(view, "esc back") {
+		t.Fatal("transcript view should carry the file nav bar")
+	}
+}
+
+// TestSubchatEntryClosesFileView: drilling into an AGENTS row while a file view
+// is open closes the file view first (the subchat owns the single-column view).
+func TestSubchatEntryClosesFileView(t *testing.T) {
+	store := sessions.NewStore(sessions.StoreOptions{RootDir: t.TempDir()})
+	if _, err := store.Create(sessions.CreateInput{SessionID: "sess-1"}); err != nil {
+		t.Fatal(err)
+	}
+	m := filesPanelTestModel()
+	m.sessionStore = store
+	m.swarmSessionMap = map[string]string{"subagent-1": "sess-1"}
+	m.transcript = append(m.transcript,
+		transcriptRow{kind: rowToolCall, tool: "swarm_spawn", detail: "build it", runID: 1},
+		transcriptRow{kind: rowToolResult, tool: "swarm_spawn", detail: "Spawned subagent as task subagent-1 on team default.", runID: 1},
+	)
+	m.activeRunID = 1
+	m = m.openFileView("web/app.js")
+
+	width := sidebarWidth(m.width)
+	agents := m.sidebarAgentSelectables(width)
+	if len(agents) == 0 {
+		t.Fatal("expected a clickable agent row")
+	}
+	click := testMouseClick(tea.MouseLeft, m.chatColumnWidth()+3, agents[0].lineOffset)
+	updated, _, handled := m.handleTranscriptSelectionMouse(click)
+	if !handled {
+		t.Fatal("agent row click should be handled")
+	}
+	if updated.fileView.active {
+		t.Fatal("entering the subchat should close the file view")
+	}
+	if !updated.subchat.active {
+		t.Fatal("subchat should be active")
+	}
+}
+
+// TestChangedFilesRehydration: a persisted tool-result payload's changedFiles
+// restores onto the rehydrated transcript row, so the FILES panel survives
+// /resume.
+func TestChangedFilesRehydration(t *testing.T) {
+	events := []sessions.Event{{
+		Type:    sessions.EventToolResult,
+		Payload: json.RawMessage(`{"toolCallId":"t1","name":"edit_file","status":"ok","output":"+x","changedFiles":["pkg/a.go","pkg/b.go"]}`),
+	}}
+	rows := transcriptRowsFromSessionEvents(events)
+	if len(rows) != 1 {
+		t.Fatalf("expected 1 row, got %d", len(rows))
+	}
+	got := rows[0].changedFiles
+	if len(got) != 2 || got[0] != "pkg/a.go" || got[1] != "pkg/b.go" {
+		t.Fatalf("changedFiles not rehydrated: %v", got)
+	}
+}
+
+// TestOpenFileViewSamePathIsNoOp: re-clicking the FILES row of the file already
+// being viewed must not clobber the user's mode or scroll — the old
+// unconditional openFileView bounced full mode back to diff and reset scroll.
+func TestOpenFileViewSamePathIsNoOp(t *testing.T) {
+	m := filesPanelTestModel()
+	m = m.openFileView("web/app.js")
+	m = m.setFileViewMode(fileViewFull)
+	m.chatScrollOffset = 7 // scrolled within the file body
+
+	m = m.openFileView("web/app.js")
+	if m.fileView.mode != fileViewFull {
+		t.Fatal("re-opening the same file must keep full mode")
+	}
+	if m.chatScrollOffset != 7 {
+		t.Fatalf("re-opening the same file must keep the scroll, got %d", m.chatScrollOffset)
+	}
+	// A DIFFERENT file still switches (and resets to diff mode as documented).
+	m = m.openFileView("internal/tui/sidebar.go")
+	if m.fileView.path != "internal/tui/sidebar.go" || m.fileView.mode != fileViewDiff {
+		t.Fatalf("opening another file should switch views: %+v", m.fileView)
+	}
+}
+
+// TestFileViewFullBodyTruncatesLongFile: the full view stops reading at
+// fileViewMaxLines (bounded read — a giant file must not be loaded wholesale)
+// and appends the truncation trailer.
+func TestFileViewFullBodyTruncatesLongFile(t *testing.T) {
+	dir := t.TempDir()
+	var b strings.Builder
+	for i := 0; i < fileViewMaxLines+50; i++ {
+		fmt.Fprintf(&b, "line %d\n", i)
+	}
+	if err := os.WriteFile(filepath.Join(dir, "big.txt"), []byte(b.String()), 0o644); err != nil {
+		t.Fatal(err)
+	}
+	m := filesPanelTestModel()
+	m.cwd = dir
+	m.gitTouched = []gitSweepFile{{path: "big.txt"}}
+	m = m.openFileView("big.txt")
+
+	plain := plainRender(t, m.renderFileViewFull(80))
+	lines := strings.Split(plain, "\n")
+	if len(lines) != fileViewMaxLines+1 { // capped content + the trailer line
+		t.Fatalf("rendered %d lines, want %d content lines + 1 trailer", len(lines), fileViewMaxLines)
+	}
+	if !strings.Contains(lines[len(lines)-1], "truncated") {
+		t.Fatalf("expected the truncation trailer, got %q", lines[len(lines)-1])
+	}
+}
+
+// TestFileViewKeysDeferToBlockingModal: with a permission prompt up, Esc and
+// the d/f shortcuts belong to the prompt — the drill-in must not swallow them
+// (Esc exiting the view instead of reaching the prompt's deny handling).
+func TestFileViewKeysDeferToBlockingModal(t *testing.T) {
+	m := filesPanelTestModel()
+	m = m.openFileView("web/app.js")
+	m.pendingPermission = &pendingPermissionPrompt{
+		request: agent.PermissionRequest{ToolName: "write_file"},
+		decide:  func(agent.PermissionDecision) {},
+	}
+
+	updated, _ := m.Update(tea.KeyPressMsg{Code: 'f', Text: "f"})
+	m = updated.(model)
+	if m.fileView.mode != fileViewDiff {
+		t.Fatal("f with a permission prompt up must not switch file-view modes")
+	}
+	updated, _ = m.Update(tea.KeyPressMsg{Code: tea.KeyEsc})
+	m = updated.(model)
+	if !m.fileView.active {
+		t.Fatal("Esc with a permission prompt up must not exit the file view")
+	}
+}

internal/tui/files_git_sweep.go

@@ -0,0 +1,237 @@
+// files_git_sweep.go fills the FILES sidebar's blind spot: mutations that
+// bypass the file tools entirely — bash/exec_command scaffolding (npm create,
+// go generate, heredoc writes) and subagents editing the shared workspace. None
+// of those produce a changedFiles-carrying tool result, so the transcript-derived
+// roster (files_panel.go) never sees them. The sweep asks git instead: a
+// baseline `git status --porcelain` snapshot is taken at startup (Init), and a
+// re-run after each command tool result / turn end reports any NEWLY dirty
+// paths, which merge into the roster with a diffstat from `git diff --numstat`.
+// Pre-existing dirty state stays in the baseline and never shows; a non-git
+// workspace fails the first command and the sweep silently stays off.
+package tui
+
+import (
+	"context"
+	"strconv"
+	"strings"
+	"time"
+
+	tea "charm.land/bubbletea/v2"
+)
+
+// gitSweepTimeout bounds each background git invocation so a hung index lock
+// can never stall message delivery (the command runs off the update goroutine).
+const gitSweepTimeout = 3 * time.Second
+
+// gitSweepFile is one workspace file git reports as dirty: workspace-relative
+// path (git's own output convention, matching changedFiles), whether it is new
+// (untracked/added), and the tracked diffstat when known (0/0 for untracked).
+type gitSweepFile struct {
+	path    string
+	created bool
+	adds    int
+	dels    int
+}
+
+// gitSweepMsg carries one sweep's result. baseline marks the startup snapshot
+// (recorded as "pre-existing, never show") vs a live re-check (merged into the
+// roster). ok is false when git failed (not a repo, no git binary) — the
+// handler then marks the sweep unavailable rather than retrying every turn.
+type gitSweepMsg struct {
+	baseline bool
+	ok       bool
+	files    []gitSweepFile
+}
+
+// gitSweepCmd runs the status+numstat pair off the update goroutine. cwd is the
+// workspace root the TUI resolves paths against.
+func gitSweepCmd(parent context.Context, cwd string, baseline bool) tea.Cmd {
+	return func() tea.Msg {
+		if parent == nil {
+			parent = context.Background()
+		}
+		ctx, cancel := context.WithTimeout(parent, gitSweepTimeout)
+		defer cancel()
+		// --untracked-files=all enumerates files inside new directories; plain
+		// porcelain collapses them to "dir/", which is useless as a FILES row.
+		status, err := defaultPRCommandRunner(ctx, cwd, "git", "status", "--porcelain", "--untracked-files=all")
+		if err != nil {
+			return gitSweepMsg{baseline: baseline, ok: false}
+		}
+		files := parseGitPorcelain(status)
+		// Diffstat for tracked modifications; untracked files have no diff to
+		// stat. -z makes the output machine-parseable: NUL-terminated records, no
+		// path quoting, and renames as explicit preimage/postimage fields instead
+		// of the brace-mangled "src/{old => new}" a plain --numstat emits (which
+		// would never match a porcelain path). Best-effort: a failure (e.g. unborn
+		// HEAD in a fresh repo) keeps the file list with zero counts rather than
+		// dropping the sweep.
+		if numstat, err := defaultPRCommandRunner(ctx, cwd, "git", "diff", "HEAD", "--numstat", "-z"); err == nil {
+			stats := parseGitNumstat(numstat)
+			for i := range files {
+				if counts, ok := stats[files[i].path]; ok {
+					files[i].adds, files[i].dels = counts[0], counts[1]
+				}
+			}
+		}
+		return gitSweepMsg{baseline: baseline, ok: true, files: files}
+	}
+}
+
+// parseGitPorcelain parses `git status --porcelain` v1 output into sweep files.
+// Format: two status columns, a space, then the path ("XY path"); renames show
+// "old -> new" (keep the new side); untracked entries are "?? path".
+func parseGitPorcelain(out string) []gitSweepFile {
+	var files []gitSweepFile
+	for _, line := range strings.Split(out, "\n") {
+		if len(line) < 4 {
+			continue
+		}
+		code, path := line[:2], strings.TrimSpace(line[3:])
+		if to, _, found := cutRename(path); found {
+			path = to
+		}
+		path = unquoteGitPath(path)
+		if path == "" {
+			continue
+		}
+		files = append(files, gitSweepFile{
+			path:    path,
+			created: code == "??" || strings.Contains(code, "A"),
+		})
+	}
+	return files
+}
+
+// cutRename splits a porcelain rename value "old -> new", returning the new
+// path. found is false for ordinary (non-rename) paths.
+func cutRename(path string) (string, string, bool) {
+	if idx := strings.Index(path, " -> "); idx >= 0 {
+		return path[idx+4:], path[:idx], true
+	}
+	return "", "", false
+}
+
+// unquoteGitPath strips the quotes git wraps around paths with special
+// characters ("web/my file.js"). Escapes inside are left as-is — such a path
+// still identifies the file well enough for a sidebar row.
+func unquoteGitPath(path string) string {
+	if len(path) >= 2 && strings.HasPrefix(path, `"`) && strings.HasSuffix(path, `"`) {
+		return path[1 : len(path)-1]
+	}
+	return path
+}
+
+// parseGitNumstat parses `git diff --numstat -z` output into path → [added,
+// deleted]. -z records are NUL-terminated "added\tdeleted\tpath"; a rename/copy
+// instead ends the counts record with an EMPTY path ("added\tdeleted\t") and
+// appends two more NUL-terminated fields, preimage then postimage — the stats
+// key is the postimage (the path porcelain/changedFiles report). Paths are
+// never quoted or brace-mangled in -z mode. Binary files report "-" counts and
+// are skipped.
+func parseGitNumstat(out string) map[string][2]int {
+	stats := map[string][2]int{}
+	fields := strings.Split(out, "\x00")
+	for i := 0; i < len(fields); i++ {
+		parts := strings.SplitN(fields[i], "\t", 3)
+		if len(parts) != 3 {
+			continue
+		}
+		adds, errA := strconv.Atoi(parts[0])
+		dels, errD := strconv.Atoi(parts[1])
+		if errA != nil || errD != nil {
+			continue
+		}
+		path := parts[2]
+		if path == "" {
+			// Rename/copy record: the next two fields are preimage, postimage.
+			if i+2 >= len(fields) {
+				break // truncated output — drop the partial record
+			}
+			path = fields[i+2]
+			i += 2
+		}
+		if path != "" {
+			stats[path] = [2]int{adds, dels}
+		}
+	}
+	return stats
+}
+
+// handleGitSweepMsg folds a sweep result into the model: the baseline snapshot
+// records what was already dirty before this TUI session (those paths never
+// show), a live sweep upserts newly dirty paths into gitTouched in first-seen
+// order. A failed sweep marks git unavailable so no further sweeps are issued.
+func (m model) handleGitSweepMsg(msg gitSweepMsg) model {
+	m.gitSweepInFlight = false
+	if !msg.ok {
+		m.gitSweepUnavailable = true
+		if m.gitFileBaseline == nil {
+			m.gitFileBaseline = map[string]bool{}
+		}
+		return m
+	}
+	if msg.baseline {
+		baseline := make(map[string]bool, len(msg.files))
+		for _, f := range msg.files {
+			baseline[f.path] = true
+		}
+		m.gitFileBaseline = baseline
+		return m
+	}
+	for _, f := range msg.files {
+		if m.gitFileBaseline[f.path] {
+			continue
+		}
+		found := false
+		for i := range m.gitTouched {
+			if m.gitTouched[i].path == f.path {
+				m.gitTouched[i] = f
+				found = true
+				break
+			}
+		}
+		if !found {
+			// Copy-on-append: model copies share the backing array, so an in-place
+			// append from two update branches could alias. Rebuilding is cheap at
+			// sidebar scale.
+			m.gitTouched = append(append([]gitSweepFile(nil), m.gitTouched...), f)
+		}
+	}
+	return m
+}
+
+// maybeGitSweep issues a live sweep when one is useful and none is running:
+// the baseline exists (Init's snapshot answered), git works here, and the
+// workspace is known. Returns the (possibly nil) command to batch.
+func (m model) maybeGitSweep() (model, tea.Cmd) {
+	if m.gitSweepInFlight || m.gitSweepUnavailable || m.gitFileBaseline == nil || strings.TrimSpace(m.cwd) == "" {
+		return m, nil
+	}
+	m.gitSweepInFlight = true
+	return m, gitSweepCmd(m.ctx, m.cwd, false)
+}
+
+// gitTouchedFiles adapts the sweep results to the roster's touchedFile shape,
+// for merging under the transcript-derived entries (files_panel.go), newest
+// detection first — gitTouched upserts in first-seen order, so iterating it in
+// reverse keeps the merged FILES tail consistent with the roster's
+// newest-first ordering. No transcript row backs them (lastRowIndex -1), so
+// selecting one skips the scroll/tint and the drill-in opens on the full file.
+func (m model) gitTouchedFiles() []touchedFile {
+	if len(m.gitTouched) == 0 {
+		return nil
+	}
+	files := make([]touchedFile, 0, len(m.gitTouched))
+	for i := len(m.gitTouched) - 1; i >= 0; i-- {
+		f := m.gitTouched[i]
+		files = append(files, touchedFile{
+			path:         f.path,
+			created:      f.created,
+			adds:         f.adds,
+			dels:         f.dels,
+			lastRowIndex: -1,
+		})
+	}
+	return files
+}

internal/tui/files_git_sweep_test.go

@@ -0,0 +1,243 @@
+package tui
+
+import (
+	"os"
+	"os/exec"
+	"path/filepath"
+	"testing"
+)
+
+func TestParseGitPorcelain(t *testing.T) {
+	out := " M web/app.js\n?? web/new.css\nA  docs/added.md\nR  old.go -> pkg/new.go\n?? \"web/my file.js\"\n\n"
+	files := parseGitPorcelain(out)
+	if len(files) != 5 {
+		t.Fatalf("expected 5 entries, got %d: %+v", len(files), files)
+	}
+	byPath := map[string]gitSweepFile{}
+	for _, f := range files {
+		byPath[f.path] = f
+	}
+	if f := byPath["web/app.js"]; f.created {
+		t.Error("modified file must not read as created")
+	}
+	if f := byPath["web/new.css"]; !f.created {
+		t.Error("untracked file should read as created")
+	}
+	if f := byPath["docs/added.md"]; !f.created {
+		t.Error("index-added file should read as created")
+	}
+	if _, ok := byPath["pkg/new.go"]; !ok {
+		t.Errorf("rename should keep the new path: %+v", files)
+	}
+	if _, ok := byPath["web/my file.js"]; !ok {
+		t.Errorf("quoted path should unquote: %+v", files)
+	}
+}
+
+// TestParseGitNumstat feeds the exact `git diff --numstat -z` record shapes:
+// plain "added\tdeleted\tpath\0", binary "-\t-\tpath\0", and the rename form
+// "added\tdeleted\t\0preimage\0postimage\0" — the stats must key the postimage
+// (the path porcelain/changedFiles report), which the old newline parser lost
+// (plain --numstat brace-mangles renames, so they never matched a roster path).
+func TestParseGitNumstat(t *testing.T) {
+	out := "12\t3\tweb/app.js\x00" +
+		"-\t-\tassets/logo.png\x00" +
+		"4\t0\t\x00old.go\x00pkg/new.go\x00" +
+		"1\t1\tweb/my file.js\x00" // -z paths are never quoted
+	stats := parseGitNumstat(out)
+	if got := stats["web/app.js"]; got != [2]int{12, 3} {
+		t.Errorf("web/app.js = %v, want [12 3]", got)
+	}
+	if _, ok := stats["assets/logo.png"]; ok {
+		t.Error("binary '-' entries must be skipped")
+	}
+	if got := stats["pkg/new.go"]; got != [2]int{4, 0} {
+		t.Errorf("renamed file must key the postimage path = %v, want [4 0]", got)
+	}
+	if _, ok := stats["old.go"]; ok {
+		t.Error("the rename preimage must not appear as its own entry")
+	}
+	if got := stats["web/my file.js"]; got != [2]int{1, 1} {
+		t.Errorf("path with spaces = %v, want [1 1] (no quoting in -z mode)", got)
+	}
+	// Truncated rename record (missing postimage) must not panic or mis-key.
+	if got := parseGitNumstat("4\t0\t\x00old.go"); len(got) != 0 {
+		t.Errorf("truncated rename record should be dropped, got %v", got)
+	}
+}
+
+// TestGitSweepMergeAndBaseline: the baseline snapshot hides pre-existing dirty
+// paths; live sweeps upsert only new ones; a failed sweep latches unavailable.
+func TestGitSweepMergeAndBaseline(t *testing.T) {
+	m := model{}
+	m = m.handleGitSweepMsg(gitSweepMsg{baseline: true, ok: true, files: []gitSweepFile{{path: "dirty-before.go"}}})
+	if !m.gitFileBaseline["dirty-before.go"] {
+		t.Fatal("baseline should record pre-existing dirty paths")
+	}
+
+	m = m.handleGitSweepMsg(gitSweepMsg{ok: true, files: []gitSweepFile{
+		{path: "dirty-before.go", adds: 9},
+		{path: "kanban/board.tsx", created: true, adds: 120},
+	}})
+	if len(m.gitTouched) != 1 || m.gitTouched[0].path != "kanban/board.tsx" {
+		t.Fatalf("only newly dirty paths should merge: %+v", m.gitTouched)
+	}
+
+	// Re-sweep updates stats in place, no duplicate.
+	m = m.handleGitSweepMsg(gitSweepMsg{ok: true, files: []gitSweepFile{{path: "kanban/board.tsx", created: true, adds: 150, dels: 2}}})
+	if len(m.gitTouched) != 1 || m.gitTouched[0].adds != 150 {
+		t.Fatalf("re-sweep should upsert stats: %+v", m.gitTouched)
+	}
+
+	failed := model{}
+	failed = failed.handleGitSweepMsg(gitSweepMsg{baseline: true, ok: false})
+	if !failed.gitSweepUnavailable {
+		t.Fatal("a failed sweep should latch unavailable")
+	}
+	if _, cmd := failed.maybeGitSweep(); cmd != nil {
+		t.Fatal("no further sweeps once unavailable")
+	}
+}
+
+// TestMaybeGitSweepGating: no sweep before the baseline answers, none while one
+// is in flight, and the in-flight flag sets when one is issued.
+func TestMaybeGitSweepGating(t *testing.T) {
+	m := model{cwd: "/tmp"}
+	if _, cmd := m.maybeGitSweep(); cmd != nil {
+		t.Fatal("no baseline yet: sweep must not run")
+	}
+	m.gitFileBaseline = map[string]bool{}
+	next, cmd := m.maybeGitSweep()
+	if cmd == nil || !next.gitSweepInFlight {
+		t.Fatal("with a baseline, a sweep should be issued and marked in flight")
+	}
+	if _, again := next.maybeGitSweep(); again != nil {
+		t.Fatal("single-flight: no second sweep while one runs")
+	}
+}
+
+// TestTouchedFilesMergesGitSweep: git-discovered files append below the
+// transcript-derived entries, deduped by path (a tool-result entry wins).
+func TestTouchedFilesMergesGitSweep(t *testing.T) {
+	m := filesPanelTestModel()
+	m.gitTouched = []gitSweepFile{
+		{path: "kanban/board.tsx", created: true, adds: 120},
+		{path: "web/app.js", adds: 999}, // duplicate of a transcript entry
+	}
+	files := m.touchedFiles()
+	var kanban *touchedFile
+	appCount := 0
+	for i := range files {
+		if files[i].path == "kanban/board.tsx" {
+			kanban = &files[i]
+		}
+		if files[i].path == "web/app.js" {
+			appCount++
+			if files[i].adds == 999 {
+				t.Error("transcript-derived entry should win over the git duplicate")
+			}
+		}
+	}
+	if kanban == nil || !kanban.created || kanban.lastRowIndex != -1 {
+		t.Fatalf("git-only file should merge with created badge and no row anchor: %+v", files)
+	}
+	if appCount != 1 {
+		t.Fatalf("web/app.js should appear exactly once, got %d", appCount)
+	}
+}
+
+// TestOpenFileViewGitOnlyFallsBackToFull: a file with no edit cards (git sweep
+// discovery) opens straight on the full-file view instead of an empty diff.
+func TestOpenFileViewGitOnlyFallsBackToFull(t *testing.T) {
+	m := filesPanelTestModel()
+	m.gitTouched = []gitSweepFile{{path: "kanban/board.tsx", created: true}}
+	m = m.openFileView("kanban/board.tsx")
+	if m.fileView.mode != fileViewFull {
+		t.Fatal("git-only file should open in full mode")
+	}
+	m = m.exitFileView()
+	m = m.openFileView("web/app.js")
+	if m.fileView.mode != fileViewDiff {
+		t.Fatal("a file with edit cards still opens in diff mode")
+	}
+}
+
+// TestGitSweepCmdAgainstRealRepo: end-to-end against a real git repo — the
+// baseline sees pre-existing dirt, a post-mutation sweep reports the new file
+// as created and the modified file with its numstat.
+func TestGitSweepCmdAgainstRealRepo(t *testing.T) {
+	if _, err := exec.LookPath("git"); err != nil {
+		t.Skip("git not installed")
+	}
+	dir := t.TempDir()
+	run := func(args ...string) {
+		t.Helper()
+		cmd := exec.Command("git", args...)
+		cmd.Dir = dir
+		cmd.Env = append(os.Environ(),
+			"GIT_AUTHOR_NAME=t", "GIT_AUTHOR_EMAIL=t@t", "GIT_COMMITTER_NAME=t", "GIT_COMMITTER_EMAIL=t@t")
+		if out, err := cmd.CombinedOutput(); err != nil {
+			t.Fatalf("git %v: %v\n%s", args, err, out)
+		}
+	}
+	write := func(name, content string) {
+		t.Helper()
+		if err := os.WriteFile(filepath.Join(dir, name), []byte(content), 0o644); err != nil {
+			t.Fatal(err)
+		}
+	}
+	run("init", "-q")
+	write("tracked.txt", "one\ntwo\n")
+	run("add", ".")
+	run("commit", "-q", "-m", "seed")
+	write("pre-existing.txt", "dirt\n") // dirty BEFORE the TUI "opens"
+
+	baseline := gitSweepCmd(nil, dir, true)().(gitSweepMsg)
+	if !baseline.ok || len(baseline.files) != 1 || baseline.files[0].path != "pre-existing.txt" {
+		t.Fatalf("baseline should see only the pre-existing dirt: %+v", baseline)
+	}
+
+	// The "agent" now scaffolds via the shell.
+	write("scaffolded.txt", "hello\n")
+	write("tracked.txt", "one\ntwo\nthree\nfour\n")
+
+	sweep := gitSweepCmd(nil, dir, false)().(gitSweepMsg)
+	if !sweep.ok {
+		t.Fatal("sweep failed")
+	}
+	byPath := map[string]gitSweepFile{}
+	for _, f := range sweep.files {
+		byPath[f.path] = f
+	}
+	if f, ok := byPath["scaffolded.txt"]; !ok || !f.created {
+		t.Fatalf("scaffolded file should report created: %+v", sweep.files)
+	}
+	if f := byPath["tracked.txt"]; f.adds != 2 || f.dels != 0 {
+		t.Fatalf("tracked.txt numstat = +%d −%d, want +2 −0", f.adds, f.dels)
+	}
+
+	// A rename WITH edits: porcelain reports the new path, and the -z numstat
+	// rename record must resolve to the same (postimage) path so the diffstat
+	// actually attaches — the plain --numstat form brace-mangles the path and
+	// the counts were silently lost.
+	run("add", ".")
+	run("commit", "-q", "-m", "second")
+	run("mv", "tracked.txt", "renamed.txt")
+	write("renamed.txt", "one\ntwo\nthree\nfour\nfive\n")
+	renameSweep := gitSweepCmd(nil, dir, false)().(gitSweepMsg)
+	if !renameSweep.ok {
+		t.Fatal("rename sweep failed")
+	}
+	renamed := map[string]gitSweepFile{}
+	for _, f := range renameSweep.files {
+		renamed[f.path] = f
+	}
+	if f, ok := renamed["renamed.txt"]; !ok || f.adds != 1 {
+		t.Fatalf("renamed file should carry its numstat under the new path, got %+v", renameSweep.files)
+	}
+
+	// Not-a-repo → ok=false (the sweep latches off).
+	if msg := gitSweepCmd(nil, t.TempDir(), false)().(gitSweepMsg); msg.ok {
+		t.Fatal("a non-repo should report ok=false")
+	}
+}

internal/tui/files_panel.go

@@ -0,0 +1,416 @@
+// files_panel.go renders the FILES section of the right context sidebar: the
+// workspace files this session has touched, newest first, with an A/M badge and
+// a +added/−removed diffstat per file, plus a pulsing row for the file whose
+// write is streaming right now. Like the swarm roster (sidebar.go), the touched
+// set is not separate model state — it is recovered on demand from the
+// transcript's tool-result rows (their changedFiles), so it survives resume for
+// free and can never drift from what the chat shows.
+//
+// Interaction (see handleTranscriptSelectionMouse): the first click on a row
+// SELECTS the file — its edit cards tint in the chat and the transcript scrolls
+// to the most recent one; a second click (or a click while the drill-in is
+// already open) opens the file view (file_view.go). Esc clears the selection.
+package tui
+
+import (
+	"fmt"
+	"sort"
+	"strings"
+
+	tea "charm.land/bubbletea/v2"
+
+	"github.com/Gitlawb/zero/internal/tools"
+)
+
+// maxSidebarFiles caps the FILES rows so the section stays a glanceable set,
+// not a scrolling log; older files collapse into a "+N more" trailer.
+const maxSidebarFiles = 6
+
+// touchedFile is one workspace file the session has mutated, aggregated across
+// every tool-result row that touched it.
+type touchedFile struct {
+	path         string
+	adds         int  // total added lines across its diffs
+	dels         int  // total removed lines across its diffs
+	edits        int  // number of mutations
+	created      bool // first touch created the file (write_file "Created …")
+	failed       bool // the latest touch errored
+	lastRowIndex int  // transcript index of the most recent result touching it
+}
+
+// touchedFiles recovers the session's touched-file roster from the transcript,
+// most recently touched first. Recomputed on demand (the value-receiver model
+// can't persist a registry from View), mirroring swarmSpawnedAgents; the scan is
+// a single pass over the transcript per render, same order as the sidebar's
+// other sections.
+func (m model) touchedFiles() []touchedFile {
+	var files []touchedFile
+	index := map[string]int{}
+	for i, row := range m.transcript {
+		if row.kind != rowToolResult || len(row.changedFiles) == 0 {
+			continue
+		}
+		adds, dels := planDiffStat(row.detail)
+		// A multi-file result (apply_patch spanning several files) must not charge
+		// the WHOLE patch's totals to every file it touched — split the diff by its
+		// per-file headers and attribute each file its own counts.
+		var perFile map[string][2]int
+		if len(row.changedFiles) > 1 {
+			perFile = perFileDiffStats(row.detail)
+		}
+		for _, path := range row.changedFiles {
+			if path == "" {
+				continue
+			}
+			at, seen := index[path]
+			if !seen {
+				index[path] = len(files)
+				files = append(files, touchedFile{
+					path:         path,
+					created:      resultRowCreatedFile(row),
+					lastRowIndex: i,
+				})
+				at = len(files) - 1
+			}
+			fileAdds, fileDels := adds, dels
+			if perFile != nil {
+				// Headers were found: use this file's own counts. A path the split
+				// couldn't attribute shows 0/0 rather than the inflated patch totals.
+				counts := perFile[path]
+				fileAdds, fileDels = counts[0], counts[1]
+			}
+			files[at].adds += fileAdds
+			files[at].dels += fileDels
+			files[at].edits++
+			files[at].failed = row.status == tools.StatusError
+			files[at].lastRowIndex = i
+		}
+	}
+	// Most recently touched first: the file being worked on now belongs at the
+	// top, like the sidebar's ACTIVITY feed. Sorted by last touch (not reversed
+	// first-seen order): a file touched early and touched again last must list
+	// first. Stable, so same-row files keep their changedFiles order.
+	sort.SliceStable(files, func(i, j int) bool {
+		return files[i].lastRowIndex > files[j].lastRowIndex
+	})
+	// Merge the git sweep's discoveries (bash/subagent mutations that carry no
+	// changedFiles — files_git_sweep.go) below the transcript-derived entries,
+	// skipping paths a tool result already reported.
+	for _, f := range m.gitTouchedFiles() {
+		if _, seen := index[f.path]; seen {
+			continue
+		}
+		files = append(files, f)
+	}
+	return files
+}
+
+// perFileDiffStats splits a (possibly multi-file) unified diff into per-path
+// +added/−removed counts, keyed by the workspace-relative path from each
+// section's "+++ b/…" header (the "--- a/…" old side when the new side is
+// /dev/null, i.e. a deletion). Returns nil when the detail carries no file
+// headers at all (write_file/edit_file previews may be bare hunks) — the caller
+// then falls back to whole-detail totals, which are correct for a single file.
+func perFileDiffStats(detail string) map[string][2]int {
+	stats := map[string][2]int{}
+	current, oldPath := "", ""
+	normalize := func(line string, prefix string) string {
+		path := strings.TrimSpace(line[4:])
+		if tab := strings.IndexByte(path, '\t'); tab >= 0 {
+			path = path[:tab] // unified-diff convention: optional timestamp after a tab
+		}
+		path = unquoteGitPath(path)
+		if path == "/dev/null" {
+			return ""
+		}
+		return strings.TrimPrefix(path, prefix)
+	}
+	for _, line := range strings.Split(detail, "\n") {
+		switch {
+		case strings.HasPrefix(line, "--- "):
+			oldPath = normalize(line, "a/")
+		case strings.HasPrefix(line, "+++ "):
+			current = normalize(line, "b/")
+			if current == "" {
+				current = oldPath // deletion: charge the removed lines to the old path
+			}
+		case current == "":
+			// Lines before the first header (or in an unattributable section).
+		case strings.HasPrefix(line, "+"):
+			counts := stats[current]
+			counts[0]++
+			stats[current] = counts
+		case strings.HasPrefix(line, "-"):
+			counts := stats[current]
+			counts[1]++
+			stats[current] = counts
+		}
+	}
+	if len(stats) == 0 {
+		return nil
+	}
+	return stats
+}
+
+// resultRowCreatedFile reports whether a tool-result row reads as a file
+// creation ("tool result: write_file ok Created x (…)"), so the FILES row can
+// badge it A rather than M. Heuristic on the confirmation text write_file
+// already emits; a miss just shows M, never breaks anything.
+func resultRowCreatedFile(row transcriptRow) bool {
+	return strings.Contains(row.text, " Created ")
+}
+
+// liveEditingPath is the path of the file whose mutating tool call is streaming
+// its arguments RIGHT NOW (the same live write streamingToolCallView previews),
+// or "" when no mutation is in flight. It renders as a pulsing row pinned atop
+// the FILES section.
+func (m model) liveEditingPath() string {
+	if m.streamCallDecoder == nil {
+		return ""
+	}
+	switch m.streamCallName {
+	case "write_file", "edit_file", "apply_patch":
+		return m.streamCallDecoder.path
+	}
+	return ""
+}
+
+// fileHit marks a rendered FILES row (by its ABSOLUTE index inside the rendered
+// sidebar) that is clickable, carrying the file it refers to.
+type fileHit struct {
+	lineOffset int
+	path       string
+}
+
+// sidebarFilesHeader renders the FILES section header with the touched count.
+func (m model) sidebarFilesHeader(width int) string {
+	n := len(m.touchedFiles())
+	if n == 0 {
+		return sidebarHeader("FILES", width)
+	}
+	return sidebarHeaderWithCount("FILES", fmt.Sprintf("%d", n), zeroTheme.muted, width)
+}
+
+// sidebarFileLines renders the FILES section body: the live "writing" pulse row
+// first, then the touched files newest-first, capped at maxSidebarFiles with a
+// "+N more" trailer. Returns nil when the session has touched nothing (the
+// caller shows a placeholder). The paired hits slice records each clickable
+// row's index WITHIN the returned lines.
+func (m model) sidebarFileLines(width int) ([]string, []fileHit) {
+	files := m.touchedFiles()
+	live := m.liveEditingPath()
+	if len(files) == 0 && live == "" {
+		return nil, nil
+	}
+	room := maxInt(4, width-3)
+	var lines []string
+	var hits []fileHit
+
+	// The file being written this instant: an accent pulse, not yet clickable
+	// (its result row — the diff — doesn't exist until the call completes).
+	if live != "" {
+		lines = append(lines, " "+zeroTheme.accent.Render("●")+" "+
+			zeroTheme.ink.Render(truncatePathLeft(live, room)))
+	}
+
+	// Filter the live row out FIRST so the "+N more" trailer counts only rows
+	// that could actually render — counting the skipped live entry would inflate
+	// the overflow by one.
+	visible := files[:0:0]
+	for _, f := range files {
+		if f.path != live {
+			visible = append(visible, f)
+		}
+	}
+	shown := 0
+	for _, f := range visible {
+		if shown >= maxSidebarFiles {
+			lines = append(lines, "   "+zeroTheme.faint.Render(fmt.Sprintf("+%d more", len(visible)-shown)))
+			break
+		}
+		shown++
+		hits = append(hits, fileHit{lineOffset: len(lines), path: f.path})
+		lines = append(lines, m.renderFileRow(f, room))
+	}
+	return lines, hits
+}
+
+// renderFileRow renders one touched file: status badge, left-truncated path,
+// and the +/− diffstat, with the selected file carrying an accent marker so the
+// selection reads in the sidebar as well as in the chat tint.
+func (m model) renderFileRow(f touchedFile, room int) string {
+	badge := zeroTheme.muted.Render("M")
+	switch {
+	case f.failed:
+		badge = zeroTheme.red.Render("✗")
+	case f.created:
+		badge = zeroTheme.green.Render("A")
+	}
+	// Reserve the diffstat's width so the path truncates around it.
+	stat := ""
+	if f.adds > 0 || f.dels > 0 {
+		stat = fmt.Sprintf(" +%d −%d", f.adds, f.dels)
+	}
+	pathRoom := maxInt(4, room-len(stat))
+	pathStyle := zeroTheme.muted
+	lead := " "
+	if m.selectedFile == f.path {
+		lead = zeroTheme.accent.Render("▸")
+		pathStyle = zeroTheme.ink
+	}
+	line := lead + badge + " " + pathStyle.Render(truncatePathLeft(f.path, pathRoom))
+	if stat != "" {
+		line += zeroTheme.faintest.Render(stat)
+	}
+	return line
+}
+
+// sidebarFileSelectables returns the clickable FILES rows with their ABSOLUTE
+// index inside the rendered sidebar. The FILES section renders after PLAN in
+// renderContextSidebar: AGENTS header + body, blank + PLAN header + body, then
+// blank + FILES header, then the file rows. The offset accounting mirrors
+// sidebarPlanSelectables exactly, extended one section down.
+func (m model) sidebarFileSelectables(width int) []fileHit {
+	lines, hits := m.sidebarFileLines(width)
+	if len(lines) == 0 {
+		return nil
+	}
+	agentBody := len(m.sidebarAgentLines(width))
+	if agentBody == 0 {
+		agentBody = 1 // the "no agents spawned" placeholder occupies one line
+	}
+	planBody := len(m.sidebarPlanLines(width))
+	if planBody == 0 {
+		planBody = 1 // the "no active plan" placeholder occupies one line
+	}
+	base := 1 + agentBody + 2 + planBody + 2 // sections above + (blank + FILES header)
+	for i := range hits {
+		hits[i].lineOffset += base
+	}
+	return hits
+}
+
+// fileRowAtMouse maps a left-click in the context sidebar to a touched file,
+// mirroring planStepAtMouse's column/x gate. Rows truncated away by the
+// sidebar's height budget (or colliding with the token floor line) never match.
+func (m model) fileRowAtMouse(msg tea.MouseMsg) (string, bool) {
+	if !m.sidebarActive() {
+		return "", false
+	}
+	if m.setup.visible || m.providerWizard != nil || m.mcpAddWizard != nil || m.mcpManager != nil || m.picker != nil || m.suggestionsActive() {
+		return "", false
+	}
+	sidebarW := sidebarWidth(m.width)
+	if sidebarW <= 0 {
+		return "", false
+	}
+	x0 := m.chatColumnWidth() + 3 // " │ " divider between the columns
+	x, y := mouseX(msg), mouseY(msg)
+	if x < x0 || x >= x0+sidebarW {
+		return "", false
+	}
+	for _, hit := range m.sidebarFileSelectables(sidebarW) {
+		if hit.lineOffset == y && hit.lineOffset < m.height-1 && hit.path != "" {
+			return hit.path, true
+		}
+	}
+	return "", false
+}
+
+// rowTouchesSelectedFile reports whether a transcript row's mutation touched
+// the currently selected file, so its card renders with the selection tint.
+func (m model) rowTouchesSelectedFile(row transcriptRow) bool {
+	if m.selectedFile == "" || row.kind != rowToolResult {
+		return false
+	}
+	for _, path := range row.changedFiles {
+		if path == m.selectedFile {
+			return true
+		}
+	}
+	return false
+}
+
+// lastRowIndexForFile returns the transcript index of the most recent
+// tool-result row that touched path, or -1.
+func (m model) lastRowIndexForFile(path string) int {
+	for i := len(m.transcript) - 1; i >= 0; i-- {
+		row := m.transcript[i]
+		if row.kind != rowToolResult {
+			continue
+		}
+		for _, p := range row.changedFiles {
+			if p == path {
+				return i
+			}
+		}
+	}
+	return -1
+}
+
+// selectFile marks path as the selected file and scrolls the transcript so its
+// most recent edit card is in view; the card tint comes from the renderers
+// reading selectedFile (rowTouchesSelectedFile).
+func (m model) selectFile(path string) model {
+	m.selectedFile = path
+	if offset, ok := m.scrollOffsetForTranscriptRow(m.lastRowIndexForFile(path)); ok {
+		m.chatScrollOffset = offset
+		if offset == 0 {
+			m.chatBodyLines = 0
+		}
+	}
+	return m
+}
+
+// scrollOffsetForTranscriptRow computes the chatScrollOffset that places the
+// given transcript row's first rendered line at the top of the viewport (with
+// one line of breathing room), using the same layout metrics the scroll engine
+// itself uses. ok is false outside alt-screen or when the row isn't rendered
+// (e.g. skipped/collapsed).
+func (m model) scrollOffsetForTranscriptRow(rowIndex int) (int, bool) {
+	if rowIndex < 0 || !m.altScreen || m.height <= 0 {
+		return 0, false
+	}
+	width := m.chatColumnWidth()
+	items := m.transcriptBodyItems(width, "")
+	metrics := measureTranscriptBodyItems(items, m.transcriptBodyHeights)
+	startY := -1
+	for _, span := range metrics.spans {
+		if span.kind == transcriptBodyItemRow && span.rowIndex == rowIndex {
+			startY = span.startY
+			break
+		}
+	}
+	if startY < 0 {
+		return 0, false
+	}
+	frame := m.scrollableTranscriptFrame(m.pinnedTitleBar(width), m.footerView(width))
+	viewport := transcriptViewportForLayout(metrics, frame, m.chatScrollOffset)
+	// The offset counts lines below the fold: window.start == total-height-offset,
+	// so placing startY at the window top (minus one context line) means
+	// offset = total - height - (startY - 1), clamped to the scroll range.
+	offset := metrics.totalLines() - frame.bodyRect.height - (startY - 1)
+	return clampInt(offset, 0, viewport.maxOffset()), true
+}
+
+// truncatePathLeft fits a path into room cells by dropping leading components
+// ("internal/tui/sidebar.go" → "…/tui/sidebar.go"), keeping the filename — the
+// part that identifies the file — intact for as long as possible.
+func truncatePathLeft(path string, room int) string {
+	if room <= 0 {
+		return ""
+	}
+	if len(path) <= room {
+		return path
+	}
+	const ellipsis = "…/"
+	parts := strings.Split(path, "/")
+	for start := 1; start < len(parts); start++ {
+		candidate := ellipsis + strings.Join(parts[start:], "/")
+		if len(candidate) <= room {
+			return candidate
+		}
+	}
+	// Even "…/name" overflows: fall back to a right-truncated basename.
+	return truncateRunes(ellipsis+parts[len(parts)-1], room)
+}

internal/tui/files_panel_test.go

@@ -0,0 +1,317 @@
+package tui
+
+import (
+	"strings"
+	"testing"
+
+	tea "charm.land/bubbletea/v2"
+
+	"github.com/Gitlawb/zero/internal/tools"
+)
+
+// filesPanelTestModel is sidebarTestModel plus a couple of touched files: one
+// created, one edited twice (the second touch most recent).
+func filesPanelTestModel() model {
+	m := sidebarTestModel()
+	m.transcript = append(m.transcript,
+		transcriptRow{kind: rowToolResult, tool: "write_file", id: "f1", status: tools.StatusOK,
+			text:         "tool result: write_file ok Created web/app.js (10 lines).",
+			detail:       "+let a = 1\n+let b = 2",
+			changedFiles: []string{"web/app.js"}},
+		transcriptRow{kind: rowToolResult, tool: "edit_file", id: "f2", status: tools.StatusOK,
+			text:         "tool result: edit_file ok Edited internal/tui/sidebar.go.",
+			detail:       "+added one\n-removed one",
+			changedFiles: []string{"internal/tui/sidebar.go"}},
+		transcriptRow{kind: rowToolResult, tool: "edit_file", id: "f3", status: tools.StatusOK,
+			text:         "tool result: edit_file ok Edited internal/tui/sidebar.go.",
+			detail:       "+two\n+three\n-gone",
+			changedFiles: []string{"internal/tui/sidebar.go"}},
+	)
+	return m
+}
+
+// TestTouchedFilesAggregates: the roster is recovered from tool-result rows,
+// newest-touch first, with per-file diffstat totals, edit counts, and the
+// created badge from write_file's confirmation text.
+func TestTouchedFilesAggregates(t *testing.T) {
+	m := filesPanelTestModel()
+	files := m.touchedFiles()
+	if len(files) != 2 {
+		t.Fatalf("expected 2 touched files, got %d: %+v", len(files), files)
+	}
+	// sidebar.go was touched last, so it lists first.
+	if files[0].path != "internal/tui/sidebar.go" {
+		t.Fatalf("most recently touched file should list first, got %q", files[0].path)
+	}
+	if files[0].adds != 3 || files[0].dels != 2 || files[0].edits != 2 {
+		t.Errorf("sidebar.go diffstat = +%d −%d over %d edits, want +3 −2 over 2", files[0].adds, files[0].dels, files[0].edits)
+	}
+	if files[0].created {
+		t.Error("edited file must not read as created")
+	}
+	if !files[1].created {
+		t.Error("write_file 'Created …' result should mark the file created")
+	}
+	if files[0].lastRowIndex != len(m.transcript)-1 {
+		t.Errorf("lastRowIndex = %d, want the final transcript row", files[0].lastRowIndex)
+	}
+}
+
+// TestSidebarFileLinesRenderAndOverflow: rows carry the badge + left-truncated
+// path + diffstat; beyond maxSidebarFiles the tail collapses into "+N more";
+// hits index only real file rows.
+func TestSidebarFileLinesRenderAndOverflow(t *testing.T) {
+	m := filesPanelTestModel()
+	lines, hits := m.sidebarFileLines(34)
+	joined := plainRender(t, strings.Join(lines, "\n"))
+	if !strings.Contains(joined, "sidebar.go") || !strings.Contains(joined, "app.js") {
+		t.Fatalf("file rows missing paths:\n%s", joined)
+	}
+	if !strings.Contains(joined, "+3 −2") {
+		t.Errorf("expected aggregated diffstat +3 −2:\n%s", joined)
+	}
+	if !strings.Contains(joined, "A") || !strings.Contains(joined, "M") {
+		t.Errorf("expected A and M badges:\n%s", joined)
+	}
+	if len(hits) != 2 {
+		t.Fatalf("expected 2 clickable hits, got %d", len(hits))
+	}
+	if hits[0].path != "internal/tui/sidebar.go" {
+		t.Errorf("first hit should be the newest file, got %q", hits[0].path)
+	}
+
+	// Overflow: 8 distinct files -> maxSidebarFiles rows + a "+2 more" trailer.
+	over := sidebarTestModel()
+	for _, name := range []string{"a", "b", "c", "d", "e", "f", "g", "h"} {
+		over.transcript = append(over.transcript, transcriptRow{
+			kind: rowToolResult, tool: "edit_file", id: name, status: tools.StatusOK,
+			changedFiles: []string{name + ".go"},
+		})
+	}
+	overLines, overHits := over.sidebarFileLines(34)
+	if len(overHits) != maxSidebarFiles {
+		t.Fatalf("expected %d clickable rows, got %d", maxSidebarFiles, len(overHits))
+	}
+	if got := plainRender(t, overLines[len(overLines)-1]); !strings.Contains(got, "+2 more") {
+		t.Errorf("expected '+2 more' trailer, got %q", got)
+	}
+}
+
+// TestSidebarFilesLivePulseRow: while a mutating tool call streams its args,
+// the file it is writing shows as a pinned (unclickable) pulse row.
+func TestSidebarFilesLivePulseRow(t *testing.T) {
+	m := filesPanelTestModel()
+	m.streamCallName = "write_file"
+	m.streamCallDecoder = newStreamingDecoder()
+	m.streamCallDecoder.feed(`{"path":"web/new.css","content":"body{}`)
+
+	lines, hits := m.sidebarFileLines(34)
+	if got := plainRender(t, lines[0]); !strings.Contains(got, "web/new.css") {
+		t.Fatalf("live write should pin its path atop FILES, got %q", got)
+	}
+	for _, hit := range hits {
+		if hit.path == "web/new.css" {
+			t.Error("the live row must not be clickable (no result exists yet)")
+		}
+	}
+	// A non-mutating streaming call shows no pulse row.
+	m.streamCallName = "read_file"
+	if m.liveEditingPath() != "" {
+		t.Error("read_file must not read as a live edit")
+	}
+}
+
+// TestSidebarFileSelectablesMatchRenderedRows: the hit offsets computed by
+// sidebarFileSelectables must land exactly on the rendered FILES rows in
+// renderContextSidebar's output — the same invariant the mouse hit-test relies
+// on. Asserted against the real render, not a re-derivation of the math.
+func TestSidebarFileSelectablesMatchRenderedRows(t *testing.T) {
+	m := filesPanelTestModel()
+	width := sidebarWidth(m.width)
+	rendered := m.renderContextSidebar(width, m.height)
+	hits := m.sidebarFileSelectables(width)
+	if len(hits) == 0 {
+		t.Fatal("expected clickable FILES rows")
+	}
+	for _, hit := range hits {
+		if hit.lineOffset >= len(rendered) {
+			t.Fatalf("hit offset %d beyond rendered sidebar (%d lines)", hit.lineOffset, len(rendered))
+		}
+		line := plainRender(t, rendered[hit.lineOffset])
+		base := hit.path[strings.LastIndex(hit.path, "/")+1:]
+		if !strings.Contains(line, base) {
+			t.Errorf("hit for %q points at line %d which reads %q", hit.path, hit.lineOffset, line)
+		}
+	}
+}
+
+// TestFileRowClickSelectsThenOpens: the first sidebar click on a file selects
+// it (tint + scroll state, no view swap); the second click on the same file
+// opens the drill-in; clicking another file while the view is open switches it.
+func TestFileRowClickSelectsThenOpens(t *testing.T) {
+	m := filesPanelTestModel()
+	width := sidebarWidth(m.width)
+	hits := m.sidebarFileSelectables(width)
+	if len(hits) < 2 {
+		t.Fatal("expected two clickable FILES rows")
+	}
+	x := m.chatColumnWidth() + 3
+	click := func(hit fileHit) tea.MouseMsg { return testMouseClick(tea.MouseLeft, x, hit.lineOffset) }
+
+	m1, _, handled := m.handleTranscriptSelectionMouse(click(hits[0]))
+	if !handled {
+		t.Fatal("FILES row click should be handled")
+	}
+	if m1.selectedFile != hits[0].path || m1.fileView.active {
+		t.Fatalf("first click should select (not open): selected=%q active=%v", m1.selectedFile, m1.fileView.active)
+	}
+
+	m2, _, _ := m1.handleTranscriptSelectionMouse(click(hits[0]))
+	if !m2.fileView.active || m2.fileView.path != hits[0].path {
+		t.Fatalf("second click should open the file view: %+v", m2.fileView)
+	}
+
+	m3, _, _ := m2.handleTranscriptSelectionMouse(click(hits[1]))
+	if !m3.fileView.active || m3.fileView.path != hits[1].path {
+		t.Fatalf("clicking another file with the view open should switch it: %+v", m3.fileView)
+	}
+	if m3.selectedFile != hits[1].path {
+		t.Errorf("switching the view should move the selection too, got %q", m3.selectedFile)
+	}
+}
+
+// TestRowTouchesSelectedFileTint: only tool-result rows whose changedFiles
+// carry the selected path tint, and the render cache key differs across
+// selection states so the tint can't be served stale.
+func TestRowTouchesSelectedFileTint(t *testing.T) {
+	m := filesPanelTestModel()
+	row := m.transcript[len(m.transcript)-1]
+	if m.rowTouchesSelectedFile(row) {
+		t.Fatal("nothing selected: no row should tint")
+	}
+	m.selectedFile = "internal/tui/sidebar.go"
+	if !m.rowTouchesSelectedFile(row) {
+		t.Fatal("selected file's edit row should tint")
+	}
+	other := m.transcript[len(m.transcript)-3] // web/app.js
+	if m.rowTouchesSelectedFile(other) {
+		t.Fatal("an unrelated file's row must not tint")
+	}
+
+	rc := buildRowContext(m.transcript)
+	opts := cardRenderOptions{bodyCap: cardBodyMaxLines, cwd: m.cwd}
+	selectedKey, _ := m.renderRowCacheKey(row, 80, rc, opts, false)
+	m.selectedFile = ""
+	plainKey, _ := m.renderRowCacheKey(row, 80, rc, opts, false)
+	if selectedKey == plainKey {
+		t.Error("render cache key must change with the selection state")
+	}
+}
+
+// TestEscClearsFileSelectionThenNothing: Esc drops an active file selection
+// (before any run-level action) and is consumed doing so.
+func TestEscClearsFileSelectionThenNothing(t *testing.T) {
+	m := filesPanelTestModel()
+	m.selectedFile = "web/app.js"
+	updated, _ := m.Update(tea.KeyPressMsg{Code: tea.KeyEsc})
+	if got := updated.(model).selectedFile; got != "" {
+		t.Fatalf("Esc should clear the file selection, still %q", got)
+	}
+}
+
+func TestTruncatePathLeft(t *testing.T) {
+	if got := truncatePathLeft("internal/tui/sidebar.go", 40); got != "internal/tui/sidebar.go" {
+		t.Errorf("short path should pass through, got %q", got)
+	}
+	if got := truncatePathLeft("internal/tui/sidebar.go", 18); got != "…/tui/sidebar.go" {
+		t.Errorf("want …/tui/sidebar.go, got %q", got)
+	}
+	if got := truncatePathLeft("internal/tui/sidebar.go", 14); got != "…/sidebar.go" {
+		t.Errorf("want …/sidebar.go, got %q", got)
+	}
+}
+
+// TestTouchedFilesPerFileDiffStat: a multi-file result (apply_patch spanning
+// several files) must charge each file its OWN +/- counts from the per-file
+// diff sections — not the whole patch's totals to every file it touched.
+func TestTouchedFilesPerFileDiffStat(t *testing.T) {
+	m := sidebarTestModel()
+	patch := "diff --git a/web/one.js b/web/one.js\n" +
+		"--- a/web/one.js\n+++ b/web/one.js\n@@ -1,1 +1,2 @@\n+added one\n+added two\n" +
+		"diff --git a/web/two.js b/web/two.js\n" +
+		"--- a/web/two.js\n+++ b/web/two.js\n@@ -1,2 +1,1 @@\n-gone one\n-gone two\n-gone three\n"
+	m.transcript = append(m.transcript, transcriptRow{
+		kind: rowToolResult, tool: "apply_patch", id: "p1", status: tools.StatusOK,
+		detail:       patch,
+		changedFiles: []string{"web/one.js", "web/two.js"},
+	})
+	byPath := map[string]touchedFile{}
+	for _, f := range m.touchedFiles() {
+		byPath[f.path] = f
+	}
+	if f := byPath["web/one.js"]; f.adds != 2 || f.dels != 0 {
+		t.Errorf("web/one.js = +%d −%d, want its own +2 −0 (not the patch totals)", f.adds, f.dels)
+	}
+	if f := byPath["web/two.js"]; f.adds != 0 || f.dels != 3 {
+		t.Errorf("web/two.js = +%d −%d, want its own +0 −3 (not the patch totals)", f.adds, f.dels)
+	}
+}
+
+// TestTouchedFilesRetouchOrdersByLastTouch: touch a, then b, then a again — a
+// must list first. The old "reverse first-seen order" put b first because a's
+// slot kept its original position.
+func TestTouchedFilesRetouchOrdersByLastTouch(t *testing.T) {
+	m := sidebarTestModel()
+	for _, step := range []struct{ id, path string }{
+		{"r1", "a.go"}, {"r2", "b.go"}, {"r3", "a.go"},
+	} {
+		m.transcript = append(m.transcript, transcriptRow{
+			kind: rowToolResult, tool: "edit_file", id: step.id, status: tools.StatusOK,
+			changedFiles: []string{step.path},
+		})
+	}
+	files := m.touchedFiles()
+	if len(files) != 2 || files[0].path != "a.go" {
+		t.Fatalf("the re-touched file must list first, got %+v", files)
+	}
+}
+
+// TestSidebarFileLinesOverflowExcludesLiveRow: when the live-writing file is
+// also a touched file, it renders as the pulse row and is skipped from the
+// list — the "+N more" trailer must not count that skipped entry.
+func TestSidebarFileLinesOverflowExcludesLiveRow(t *testing.T) {
+	m := sidebarTestModel()
+	for _, name := range []string{"a", "b", "c", "d", "e", "f", "g", "h"} {
+		m.transcript = append(m.transcript, transcriptRow{
+			kind: rowToolResult, tool: "edit_file", id: name, status: tools.StatusOK,
+			changedFiles: []string{name + ".go"},
+		})
+	}
+	// h.go (a touched file) is ALSO the live write: 7 listable files remain,
+	// 6 render, so the trailer is +1 — not +2 (which counted the skipped live row).
+	m.streamCallName = "edit_file"
+	m.streamCallDecoder = newStreamingDecoder()
+	m.streamCallDecoder.feed(`{"path":"h.go","content":"x`)
+
+	lines, _ := m.sidebarFileLines(34)
+	trailer := plainRender(t, lines[len(lines)-1])
+	if !strings.Contains(trailer, "+1 more") {
+		t.Fatalf("overflow must exclude the live row from the count, got %q", trailer)
+	}
+}
+
+// TestSidebarHasContentForLiveWrite: the sidebar counts an in-flight first
+// write as content, so the FILES pulse is visible before any result row lands.
+func TestSidebarHasContentForLiveWrite(t *testing.T) {
+	m := sidebarTestModel()
+	m.plan.steps = nil // drop the helper's seeded plan: no agents/plan/files now
+	if m.sidebarHasContent() {
+		t.Fatal("session without agents/plan/files should have no sidebar content")
+	}
+	m.streamCallName = "write_file"
+	m.streamCallDecoder = newStreamingDecoder()
+	m.streamCallDecoder.feed(`{"path":"web/new.css","content":"body{}`)
+	if !m.sidebarHasContent() {
+		t.Fatal("a live in-flight write must count as sidebar content")
+	}
+}

internal/tui/hover.go

@@ -15,6 +15,9 @@ const (
 	// hoverPlanStep: a plan step row in the sidebar's PLAN section, identified by
 	// step index.
 	hoverPlanStep
+	// hoverFileRow: a touched-file row in the sidebar's FILES section, identified
+	// by path.
+	hoverFileRow
 )
 
 // hoverTarget identifies the single clickable row (if any) currently under the
@@ -34,6 +37,7 @@ type hoverTarget struct {
 	bodyY     int    // hoverTranscript
 	sessionID string // hoverSidebarAgent
 	stepIndex int    // hoverPlanStep
+	filePath  string // hoverFileRow
 }
 
 // mouseHover reports whether msg is a plain cursor-movement event with NO button
@@ -59,6 +63,9 @@ func (m model) updateHoverTarget(msg tea.MouseMsg) model {
 	if stepIndex, ok := m.planStepAtMouse(msg); ok {
 		return m.withHover(hoverTarget{kind: hoverPlanStep, stepIndex: stepIndex})
 	}
+	if path, ok := m.fileRowAtMouse(msg); ok {
+		return m.withHover(hoverTarget{kind: hoverFileRow, filePath: path})
+	}
 	if line, ok := m.transcriptLineAtMouse(msg); ok {
 		// A permission option reuses its OWN existing keyboard-cursor highlight
 		// (see hoverPermissionOption) rather than the m.hover mechanism, so there's

internal/tui/model.go

@@ -211,6 +211,22 @@ type model struct {
 	// sidebar; when set, the chat reflows to full width. Distinct from the
 	// availability conditions in sidebarAvailable (geometry / mode / overlays).
 	sidebarHidden bool
+	// selectedFile is the touched file selected by clicking its FILES sidebar
+	// row: its edit cards tint in the chat (rowTouchesSelectedFile) and a second
+	// click opens the drill-in file view. "" when nothing is selected; Esc clears.
+	selectedFile string
+	// fileView is the drill-in view for a touched file (file_view.go): while
+	// active the chat column's body shows the file's diff/content instead of the
+	// transcript, mirroring the subchat drill-in.
+	fileView fileViewState
+	// Git-sweep state (files_git_sweep.go): the startup snapshot of already-dirty
+	// paths (nil until Init's sweep answers), the newly dirty files discovered by
+	// live sweeps (bash/subagent mutations that carry no changedFiles), the
+	// single-flight guard, and the "not a git repo / no git" latch.
+	gitFileBaseline     map[string]bool
+	gitTouched          []gitSweepFile
+	gitSweepInFlight    bool
+	gitSweepUnavailable bool
 	// swarmDoneAt records when each swarm member was first seen finished (done/
 	// failed) in a swarm_status report, so the sidebar can linger it briefly with a
 	// fading ✓ before dropping it (a smooth exit, not an abrupt pop). Stamped in the
@@ -803,6 +819,12 @@ func (m model) Init() tea.Cmd {
 	// terminal's unprompted push — mirrors the RequestBackgroundColor request
 	// below for the same reason.
 	cmds = append(cmds, tea.RequestWindowSize)
+	// Baseline git snapshot for the FILES sidebar sweep: whatever is already
+	// dirty when the TUI opens is pre-existing state, not this session's work
+	// (files_git_sweep.go). Async; a non-git workspace just disables the sweep.
+	if strings.TrimSpace(m.cwd) != "" {
+		cmds = append(cmds, gitSweepCmd(m.ctx, m.cwd, true))
+	}
 	// In auto mode, ask the terminal for its background color; the reply arrives
 	// as tea.BackgroundColorMsg and selects light vs dark (see updateModel).
 	if m.themeMode == themeAuto {
@@ -1058,6 +1080,14 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 			return m.handleCtrlC()
 		case keyCtrl(msg, 'o'):
 			return m.toggleDetailedTranscript(), nil
+		case m.fileView.active && m.noBlockingModal() && m.composerValue() == "" && (keyText(msg) == "d" || keyText(msg) == "f"):
+			// Mode toggle for the file drill-in, only while the composer is empty
+			// (so mid-sentence typing is never hijacked) and no modal is up (so a
+			// permission prompt / ask-user / wizard keeps its own key handling).
+			if keyText(msg) == "f" {
+				return m.setFileViewMode(fileViewFull), nil
+			}
+			return m.setFileViewMode(fileViewDiff), nil
 		case keyCtrl(msg, 'e'):
 			// Release/recapture the mouse so the user can drag-select and copy text
 			// natively (mouse capture otherwise intercepts terminal selection).
@@ -1082,6 +1112,14 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 				m = m.clearHover() // bodyY numbering differs between subchat and the parent transcript
 				return m, nil
 			}
+			// File drill-in exits on Esc (returns to the chat at its saved scroll
+			// position); the file stays selected so a second Esc clears that. Only
+			// with no blocking modal up: Esc on a permission prompt / ask-user /
+			// wizard must reach THAT surface's deny/cancel handling below, not
+			// silently close the drill-in behind it.
+			if m.fileView.active && m.noBlockingModal() {
+				return m.exitFileView(), nil
+			}
 			if m.mcpCommandCancel != nil {
 				m.cancelMCPCommand()
 				if m.mcpAddWizard != nil {
@@ -1138,6 +1176,13 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 			if m.suggestionsActive() {
 				return m.dismissSuggestions(), nil
 			}
+			// A selected FILES row clears before anything run-related: the
+			// selection is a passive highlight, so Esc dropping it is cheap and
+			// expected (mirrors how editors clear selection on Esc).
+			if m.selectedFile != "" {
+				m.selectedFile = ""
+				return m, nil
+			}
 			if m.hasQueuedMessage() {
 				return m.clearQueuedMessage(), nil
 			}
@@ -1812,8 +1857,13 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 			}
 			m, recapCmd = m.maybeRecapTurn(msg.runID, finalAnswer)
 		}
+		// End-of-turn git sweep: catch file mutations the tool stream couldn't
+		// report (bash scaffolding, subagent edits) so the FILES sidebar is
+		// complete once the turn settles.
+		var sweepCmd tea.Cmd
+		m, sweepCmd = m.maybeGitSweep()
 		next, queuedCmd := m.launchQueuedMessageIfReady()
-		return next, tea.Batch(titleCmd, recapCmd, queuedCmd)
+		return next, tea.Batch(titleCmd, recapCmd, sweepCmd, queuedCmd)
 	case sessionTitleGeneratedMsg:
 		return m.handleSessionTitleGenerated(msg)
 	case recapGeneratedMsg:
@@ -1964,6 +2014,14 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 		m.transcript = collapseRepeatedStatusCard(m.transcript, msg.row)
 		m.transcript = appendTranscriptRow(m.transcript, msg.row)
 		m = m.captureStepWork(msg.row)
+		// A finished command tool may have mutated files git can see but no
+		// changedFiles reports (npm create, heredoc writes, subagent edits) —
+		// re-sweep so the FILES sidebar picks them up mid-turn.
+		if msg.row.kind == rowToolResult && isPlanCommandTool(msg.row.tool) {
+			var sweep tea.Cmd
+			m, sweep = m.maybeGitSweep()
+			return m, sweep
+		}
 		return m, nil
 	case swarmSessionsMsg:
 		// Merge completed swarm members' session ids so their AGENTS sidebar rows
@@ -1994,6 +2052,8 @@ func (m model) updateModel(msg tea.Msg) (tea.Model, tea.Cmd) {
 	case prStateMsg:
 		m.prState = msg.state
 		return m, nil
+	case gitSweepMsg:
+		return m.handleGitSweepMsg(msg), nil
 	case prWatcherStartedMsg:
 		if msg.stop == nil {
 			return m, nil
@@ -2198,6 +2258,12 @@ func (m model) pinnedTitleBar(width int) string {
 	if !m.altScreen || m.height <= 0 {
 		return ""
 	}
+	// The file drill-in replaces the title bar with its nav line (path + key
+	// hints). Both are exactly one line, and every frame computation routes
+	// through here, so the swap never desyncs the viewport geometry.
+	if m.fileView.active {
+		return m.fileViewNavBar(width)
+	}
 	return m.titleBar(width)
 }
 
@@ -4298,13 +4364,14 @@ func (m model) runAgentWithOptions(runID int, runCtx context.Context, prompt str
 				}
 			}
 			row := transcriptRow{
-				kind:   rowToolResult,
-				id:     effectiveToolRowID(result.ToolCallID, callSeq[result.ToolCallID]),
-				text:   toolResultRowText(result),
-				tool:   result.Name,
-				status: result.Status,
-				detail: toolResultDetail(result),
-				runID:  runID,
+				kind:         rowToolResult,
+				id:           effectiveToolRowID(result.ToolCallID, callSeq[result.ToolCallID]),
+				text:         toolResultRowText(result),
+				tool:         result.Name,
+				status:       result.Status,
+				detail:       toolResultDetail(result),
+				runID:        runID,
+				changedFiles: result.ChangedFiles,
 			}
 			// A Task result is shown by the specialist card, and update_plan by the
 			// plan panel/sidebar, so skip both redundant transcript rows.

internal/tui/render_cache.go

@@ -164,6 +164,9 @@ func (m model) renderRowCacheKey(row transcriptRow, width int, rc rowContext, op
 	appendRenderCacheField(&b, strconv.FormatBool(row.final))
 	appendRenderCacheField(&b, strconv.Itoa(row.turnTools))
 	appendRenderCacheField(&b, strconv.FormatInt(int64(row.turnElapsed), 10))
+	// The FILES selection tints this row's card border, so selecting/deselecting
+	// a file must miss the cache entry rendered under the other state.
+	appendRenderCacheField(&b, strconv.FormatBool(m.rowTouchesSelectedFile(row)))
 
 	key := rcKey(row.runID, row.id)
 	appendRenderCacheField(&b, rc.hints[key])

internal/tui/rendering.go

@@ -167,6 +167,10 @@ type cardRenderOptions struct {
 	bodyCap  int
 	cwd      string
 	expanded bool
+	// fileSelected marks a tool-result card whose mutation touched the file
+	// selected in the FILES sidebar; the card border tints accent so the
+	// selection reads in the transcript.
+	fileSelected bool
 }
 
 // flushCardBodyMaxLines is the body cap for cards flushed to scrollback. The
@@ -210,6 +214,10 @@ func (m model) renderRowMode(row transcriptRow, width int, rc rowContext, flush
 }
 
 func (m model) renderRowModeUncached(row transcriptRow, width int, rc rowContext, opts cardRenderOptions) string {
+	// Resolved per-row (not at the opts construction sites) so every render
+	// path — live, flush, detailed — carries the FILES selection tint; the
+	// cache key includes the same predicate (renderRowCacheKey).
+	opts.fileSelected = m.rowTouchesSelectedFile(row)
 	switch row.kind {
 	case rowUser:
 		return renderUserRow(row, width)
@@ -1390,6 +1398,11 @@ func renderToolResultCard(row transcriptRow, width int, rc rowContext, opts card
 	glyph := zeroTheme.green.Render("•")
 	nameStyle := zeroTheme.green
 	borderStyle := zeroTheme.line
+	if opts.fileSelected {
+		// The selected FILES row's edit card: accent border, same as the
+		// sidebar's ▸ marker, so click → highlight reads as one gesture.
+		borderStyle = zeroTheme.accent
+	}
 	if failed {
 		glyph = zeroTheme.red.Render("•")
 		nameStyle = zeroTheme.red

internal/tui/session.go

@@ -444,12 +444,13 @@ func transcriptRowsFromSessionEvents(events []sessions.Event) []transcriptRow {
 			}
 			output := payloadString(payload, "output")
 			rows = append(rows, transcriptRow{
-				kind:   rowToolResult,
-				id:     effectiveToolRowID(id, callSeq[id]),
-				text:   fmt.Sprintf("tool result: %s %s %s", name, status, truncateTUIOutput(output, tuiToolOutputLimit)),
-				tool:   name,
-				status: status,
-				detail: output,
+				kind:         rowToolResult,
+				id:           effectiveToolRowID(id, callSeq[id]),
+				text:         fmt.Sprintf("tool result: %s %s %s", name, status, truncateTUIOutput(output, tuiToolOutputLimit)),
+				tool:         name,
+				status:       status,
+				detail:       output,
+				changedFiles: payloadStringSlice(payload, "changedFiles"),
 			})
 		case sessions.EventError:
 			if message := payloadString(payload, "message"); message != "" {
@@ -619,6 +620,28 @@ func payloadString(payload map[string]any, key string) string {
 	}
 }
 
+// payloadStringSlice reads a []string persisted into a session payload (JSON
+// round-trips it as []any), skipping non-string entries. Nil when absent.
+func payloadStringSlice(payload map[string]any, key string) []string {
+	switch typed := payload[key].(type) {
+	case []string:
+		return typed
+	case []any:
+		out := make([]string, 0, len(typed))
+		for _, v := range typed {
+			if s, ok := v.(string); ok && s != "" {
+				out = append(out, s)
+			}
+		}
+		if len(out) == 0 {
+			return nil
+		}
+		return out
+	default:
+		return nil
+	}
+}
+
 func payloadBool(payload map[string]any, key string) bool {
 	value := payload[key]
 	switch typed := value.(type) {

internal/tui/sidebar.go

@@ -97,6 +97,11 @@ func (m model) sidebarHasContent() bool {
 	if len(m.sidebarSpecialists()) > 0 || len(m.swarmSpawnedAgents()) > 0 {
 		return true
 	}
+	if len(m.touchedFiles()) > 0 || m.liveEditingPath() != "" {
+		// A live in-flight write counts before its result row exists, so the
+		// FILES pulse for the session's first mutation isn't hidden.
+		return true
+	}
 	return !m.plan.isEmpty()
 }
 
@@ -587,6 +592,19 @@ func (m model) renderContextSidebar(width, height int) []string {
 		lines = append(lines, planLines...)
 	}
 
+	// FILES section: the files this session has touched (files_panel.go).
+	// Rendered BELOW the plan steps so it never shifts sidebarPlanSelectables'
+	// click offsets; its own hits (sidebarFileSelectables) account for the
+	// sections above it.
+	add("")
+	add(m.sidebarFilesHeader(width))
+	fileLines, _ := m.sidebarFileLines(width)
+	if len(fileLines) == 0 {
+		add(sidebarPlaceholder("no files touched", width))
+	} else {
+		lines = append(lines, fileLines...)
+	}
+
 	// ACTIVITY section: recent completed work + a live "generating…" pulse. Shown
 	// BELOW the plan steps so it never shifts sidebarPlanSelectables' click offsets,
 	// and budgeted (height-1 minus what's used) so it clips ITSELF from the bottom
@@ -651,6 +669,12 @@ func (m model) hoveredSidebarLineOffset(width int) (int, bool) {
 				return hit.lineOffset, true
 			}
 		}
+	case hoverFileRow:
+		for _, hit := range m.sidebarFileSelectables(width) {
+			if hit.path == m.hover.filePath {
+				return hit.lineOffset, true
+			}
+		}
 	}
 	return 0, false
 }

internal/tui/transcript.go

@@ -41,6 +41,11 @@ type transcriptRow struct {
 	askUser    *agent.AskUserRequest
 	expanded   bool // collapsible transcript rows, e.g. provider thoughts
 
+	// changedFiles lists the workspace-relative paths a mutating tool result
+	// wrote (from tools.Result.ChangedFiles; restored from the session payload on
+	// resume). The sidebar FILES section derives its roster from these.
+	changedFiles []string
+
 	// specialistInfo holds the specialist card data for rowSpecialist rows.
 	// Nil for all other row kinds.
 	specialistInfo *specialistInfo

internal/tui/transcript_selection.go

@@ -211,6 +211,12 @@ func (m model) renderHoverHighlight(rendered string, selectable []transcriptSele
 }
 
 func (m model) transcriptBodyItems(width int, emptyOverlay string) []transcriptBodyItem {
+	// File drill-in: the chat column's body swaps to the viewed file's
+	// diff/content. Swapping HERE (the single source every consumer reads) keeps
+	// the viewport, scroll engine, renderer, and mouse hit-tests consistent.
+	if m.fileView.active {
+		return m.fileViewBodyItems(width)
+	}
 	items := []transcriptBodyItem{}
 	// Transcript ROWS render at the full chat width; row/status glyphs provide
 	// structure without adding another body margin. Block items (title bar, empty
@@ -1242,6 +1248,9 @@ func (m model) handleTranscriptSelectionMouse(msg tea.MouseMsg) (model, tea.Cmd,
 		// session, reusing the specialist-card subchat path. Checked before the
 		// transcript hit-test since the sidebar is outside the chat column.
 		if hit, ok := m.sidebarLineAtMouse(msg); ok {
+			// The subchat drill-in owns the whole (single-column) view; a file
+			// drill-in can't meaningfully stay open behind it.
+			m = m.exitFileView()
 			if errMsg := m.subchat.enter(m.sessionStore, hit.sessionID, hit.title, m.chatScrollOffset); errMsg != "" {
 				m = m.appendSystemNotice(errMsg)
 			}
@@ -1252,10 +1261,24 @@ func (m model) handleTranscriptSelectionMouse(msg tea.MouseMsg) (model, tea.Cmd,
 		// A click on a PLAN step row drops a transcript card listing the file
 		// changes captured while that step was in progress.
 		if stepIndex, ok := m.planStepAtMouse(msg); ok {
+			// The card lands in the chat transcript; close the file drill-in so
+			// it isn't appended invisibly behind the swapped body.
+			m = m.exitFileView()
 			var cmd tea.Cmd
 			m, cmd = m.openPlanStepDetail(stepIndex)
 			return m, cmd, true
 		}
+		// A click on a FILES row: first click selects the file (its edit cards
+		// tint and the chat scrolls to the most recent one); a click on the
+		// already-selected file — or any FILES click while the drill-in is open —
+		// opens/switches the file view.
+		if path, ok := m.fileRowAtMouse(msg); ok {
+			if m.fileView.active || m.selectedFile == path {
+				m.selectedFile = path
+				return m.openFileView(path), nil, true
+			}
+			return m.selectFile(path), nil, true
+		}
 		line, ok := m.transcriptLineAtMouse(msg)
 		if !ok {
 			if m.transcriptSelection.active {