fix(ui): normalize line endings in session file diff stats

internal/ui/model/session.go

@@ -136,7 +136,14 @@ func (m *UI) loadSessionFiles(sessionID string) ([]SessionFile, error) {
 			}
 		}
 
-		_, additions, deletions := diff.GenerateDiff(first.Content, last.Content, first.Path)
+		// Normalize line endings so that a CRLF/LF mismatch between
+		// historical versions does not inflate the diff stats. Files
+		// round-tripped through the write tool may end up with different
+		// line endings than the original (the LLM typically emits LF),
+		// which previously caused every line to be reported as changed.
+		firstContent, _ := fsext.ToUnixLineEndings(first.Content)
+		lastContent, _ := fsext.ToUnixLineEndings(last.Content)
+		_, additions, deletions := diff.GenerateDiff(firstContent, lastContent, first.Path)
 
 		sessionFiles = append(sessionFiles, SessionFile{
 			FirstVersion:  first,

internal/ui/model/session_test.go

@@ -1,10 +1,13 @@
 package model
 
 import (
+	"fmt"
 	"strings"
 	"testing"
 
 	"charm.land/lipgloss/v2"
+	"github.com/charmbracelet/crush/internal/diff"
+	"github.com/charmbracelet/crush/internal/fsext"
 	"github.com/charmbracelet/crush/internal/history"
 	"github.com/charmbracelet/crush/internal/ui/styles"
 	"github.com/stretchr/testify/require"
@@ -111,6 +114,47 @@ func TestFileList(t *testing.T) {
 	})
 }
 
+func TestLoadSessionFilesNormalizesLineEndings(t *testing.T) {
+	t.Parallel()
+
+	makeContent := func(sep string) string {
+		var b strings.Builder
+		for i := 0; i < 1000; i++ {
+			b.WriteString(fmt.Sprintf("line %d", i))
+			b.WriteString(sep)
+		}
+		return b.String()
+	}
+
+	t.Run("CRLF vs LF reports the real delta, not the line ending swap", func(t *testing.T) {
+		t.Parallel()
+
+		first := history.File{Path: "main.go", Content: makeContent("\r\n"), Version: 0}
+		last := history.File{Path: "main.go", Content: makeContent("\n") + "added\n", Version: 1}
+
+		firstContent, _ := fsext.ToUnixLineEndings(first.Content)
+		lastContent, _ := fsext.ToUnixLineEndings(last.Content)
+		_, additions, removals := diff.GenerateDiff(firstContent, lastContent, first.Path)
+
+		require.Equal(t, 1, additions, "expected one addition for the appended line, got %d", additions)
+		require.Equal(t, 0, removals, "expected zero removals, got %d", removals)
+	})
+
+	t.Run("identical content with mismatched line endings reports no changes", func(t *testing.T) {
+		t.Parallel()
+
+		first := history.File{Path: "main.go", Content: makeContent("\r\n"), Version: 0}
+		last := history.File{Path: "main.go", Content: makeContent("\n"), Version: 1}
+
+		firstContent, _ := fsext.ToUnixLineEndings(first.Content)
+		lastContent, _ := fsext.ToUnixLineEndings(last.Content)
+		_, additions, removals := diff.GenerateDiff(firstContent, lastContent, first.Path)
+
+		require.Equal(t, 0, additions)
+		require.Equal(t, 0, removals)
+	})
+}
+
 func minimalFileStyles() *styles.Styles {
 	st := styles.CharmtonePantera()
 	st.Files.Path = lipgloss.NewStyle()