feat(tui): add syntax highlighting for code snippets in log view

Use Chroma library with Tokyo Night theme to highlight code from Read
tool results. Detects language from file extension and strips line
number prefixes from output before highlighting.

Author: MiniCodeMonkey

go.mod

@@ -10,11 +10,13 @@ require (
 )
 
 require (
+	github.com/alecthomas/chroma/v2 v2.23.1 // indirect
 	github.com/aymanbagabas/go-osc52/v2 v2.0.1 // indirect
 	github.com/charmbracelet/colorprofile v0.2.3-0.20250311203215-f60798e515dc // indirect
 	github.com/charmbracelet/x/ansi v0.10.1 // indirect
 	github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd // indirect
 	github.com/charmbracelet/x/term v0.2.1 // indirect
+	github.com/dlclark/regexp2 v1.11.5 // indirect
 	github.com/ebitengine/purego v0.4.1 // indirect
 	github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f // indirect
 	github.com/lucasb-eyer/go-colorful v1.2.0 // indirect

go.sum

@@ -1,3 +1,5 @@
+github.com/alecthomas/chroma/v2 v2.23.1 h1:nv2AVZdTyClGbVQkIzlDm/rnhk1E9bU9nXwmZ/Vk/iY=
+github.com/alecthomas/chroma/v2 v2.23.1/go.mod h1:NqVhfBR0lte5Ouh3DcthuUCTUpDC9cxBOfyMbMQPs3o=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1 h1:HwpRHbFMcZLEVr42D4p7XBqjyuxQH5SMiErDT4WkJ2k=
 github.com/aymanbagabas/go-osc52/v2 v2.0.1/go.mod h1:uYgXzlJ7ZpABp8OJ+exZzJJhRNQ2ASbcXHWsFqH8hp8=
 github.com/charmbracelet/bubbletea v1.3.10 h1:otUDHWMMzQSB0Pkc87rm691KZ3SWa4KUlvF9nRvCICw=
@@ -12,6 +14,8 @@ github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd h1:vy0G
 github.com/charmbracelet/x/cellbuf v0.0.13-0.20250311204145-2c3ea96c31dd/go.mod h1:xe0nKWGd3eJgtqZRaN9RjMtK7xUYchjzPr7q6kcvCCs=
 github.com/charmbracelet/x/term v0.2.1 h1:AQeHeLZ1OqSXhrAWpYUtZyX1T3zVxfpZuEQMIQaGIAQ=
 github.com/charmbracelet/x/term v0.2.1/go.mod h1:oQ4enTYFV7QN4m0i9mzHrViD7TQKvNEEkHUMCmsxdUg=
+github.com/dlclark/regexp2 v1.11.5 h1:Q/sSnsKerHeCkc/jSTNq1oCm7KiVgUMZRDUoRu0JQZQ=
+github.com/dlclark/regexp2 v1.11.5/go.mod h1:DHkYz0B9wPfa6wondMfaivmHpzrQ3v9q8cnmRbL6yW8=
 github.com/ebitengine/purego v0.4.1 h1:atcZEBdukuoClmy7TI89amtqAsJUzDQyY/JU7HaK+io=
 github.com/ebitengine/purego v0.4.1/go.mod h1:ah1In8AOtksoNK6yk5z1HTJeUkC1Ez4Wk2idgGslMwQ=
 github.com/erikgeiser/coninput v0.0.0-20211004153227-1c3628e74d0f h1:Y/CXytFA4m6baUTXGLOoWe4PQhGxaX0KpnayAqC48p4=

internal/tui/log.go

@@ -1,9 +1,15 @@
 package tui
 
 import (
+	"bytes"
 	"fmt"
+	"path/filepath"
 	"strings"
 
+	"github.com/alecthomas/chroma/v2"
+	"github.com/alecthomas/chroma/v2/formatters"
+	"github.com/alecthomas/chroma/v2/lexers"
+	"github.com/alecthomas/chroma/v2/styles"
 	"github.com/charmbracelet/lipgloss"
 	"github.com/minicodemonkey/chief/internal/loop"
 )
@@ -15,15 +21,17 @@ type LogEntry struct {
 	Tool      string
 	ToolInput map[string]interface{}
 	StoryID   string
+	FilePath  string // For Read tool results, stores the file path for syntax highlighting
 }
 
 // LogViewer manages the log viewport state.
 type LogViewer struct {
-	entries    []LogEntry
-	scrollPos  int  // Current scroll position (top line index)
-	height     int  // Viewport height (lines)
-	width      int  // Viewport width
-	autoScroll bool // Auto-scroll to bottom when new content arrives
+	entries          []LogEntry
+	scrollPos        int    // Current scroll position (top line index)
+	height           int    // Viewport height (lines)
+	width            int    // Viewport width
+	autoScroll       bool   // Auto-scroll to bottom when new content arrives
+	lastReadFilePath string // Track the last Read tool's file path for syntax highlighting
 }
 
 // NewLogViewer creates a new log viewer.
@@ -45,6 +53,19 @@ func (l *LogViewer) AddEvent(event loop.Event) {
 		StoryID:   event.StoryID,
 	}
 
+	// Track Read tool file paths for syntax highlighting
+	if event.Type == loop.EventToolStart && event.Tool == "Read" {
+		if filePath, ok := event.ToolInput["file_path"].(string); ok {
+			l.lastReadFilePath = filePath
+		}
+	}
+
+	// For tool results, attach the file path from the preceding Read tool
+	if event.Type == loop.EventToolResult && l.lastReadFilePath != "" {
+		entry.FilePath = l.lastReadFilePath
+		l.lastReadFilePath = "" // Clear after consuming
+	}
+
 	// Filter out events we don't want to display
 	switch event.Type {
 	case loop.EventAssistantText, loop.EventToolStart, loop.EventToolResult,
@@ -378,20 +399,139 @@ func (l *LogViewer) renderToolResult(entry LogEntry) []string {
 	resultStyle := lipgloss.NewStyle().Foreground(MutedColor)
 	checkStyle := lipgloss.NewStyle().Foreground(SuccessColor)
 
-	// Show a compact result indicator, truncate to available width
 	text := entry.Text
-	maxLen := l.width - 8 // Account for "  ↳ " prefix and padding
+	if text == "" {
+		return []string{resultStyle.Render(checkStyle.Render("  ↳ ") + "(no output)")}
+	}
+
+	// If this is a Read result with a file path, apply syntax highlighting
+	if entry.FilePath != "" {
+		highlighted := l.highlightCode(text, entry.FilePath)
+		if highlighted != "" {
+			lines := strings.Split(highlighted, "\n")
+			var result []string
+			result = append(result, checkStyle.Render("  ↳ ")) // Result indicator
+			// Limit to 20 lines to keep the log view manageable
+			maxLines := 20
+			for i, line := range lines {
+				if i >= maxLines {
+					result = append(result, resultStyle.Render(fmt.Sprintf("    ... (%d more lines)", len(lines)-maxLines)))
+					break
+				}
+				result = append(result, "    "+line)
+			}
+			return result
+		}
+	}
+
+	// Fallback: show a compact single-line result
+	maxLen := l.width - 8
 	if maxLen < 20 {
 		maxLen = 20
 	}
 	if len(text) > maxLen {
 		text = text[:maxLen-3] + "..."
 	}
-	if text == "" {
-		text = "(no output)"
+	return []string{resultStyle.Render(checkStyle.Render("  ↳ ") + text)}
+}
+
+// highlightCode applies syntax highlighting to code based on file extension.
+func (l *LogViewer) highlightCode(code, filePath string) string {
+	// Strip line number prefixes from Read tool output (format: "   1→" or "   1\t")
+	code = stripLineNumbers(code)
+
+	// Get lexer based on file extension
+	ext := filepath.Ext(filePath)
+	lexer := lexers.Match(filePath)
+	if lexer == nil {
+		lexer = lexers.Get(ext)
+	}
+	if lexer == nil {
+		lexer = lexers.Fallback
 	}
+	lexer = chroma.Coalesce(lexer)
 
-	return []string{resultStyle.Render(checkStyle.Render("  ↳ ") + text)}
+	// Use Tokyo Night theme for syntax highlighting
+	style := styles.Get("tokyonight-night")
+	if style == nil {
+		style = styles.Fallback
+	}
+
+	// Use terminal256 formatter for ANSI color output
+	formatter := formatters.Get("terminal256")
+	if formatter == nil {
+		formatter = formatters.Fallback
+	}
+
+	// Tokenize and format
+	iterator, err := lexer.Tokenise(nil, code)
+	if err != nil {
+		return ""
+	}
+
+	var buf bytes.Buffer
+	if err := formatter.Format(&buf, style, iterator); err != nil {
+		return ""
+	}
+
+	return buf.String()
+}
+
+// stripLineNumbers removes line number prefixes from Read tool output.
+// The format is: optional spaces + line number + → or tab + content
+func stripLineNumbers(code string) string {
+	lines := strings.Split(code, "\n")
+	var result []string
+
+	for _, line := range lines {
+		// Look for patterns like "   1→", "  10→", "   1\t", etc.
+		stripped := line
+
+		// Find the arrow or tab after the line number
+		arrowIdx := strings.Index(line, "→")
+		tabIdx := strings.Index(line, "\t")
+
+		idx := -1
+		if arrowIdx != -1 && tabIdx != -1 {
+			if arrowIdx < tabIdx {
+				idx = arrowIdx
+			} else {
+				idx = tabIdx
+			}
+		} else if arrowIdx != -1 {
+			idx = arrowIdx
+		} else if tabIdx != -1 {
+			idx = tabIdx
+		}
+
+		if idx > 0 && idx < 10 { // Line number prefix is typically short
+			// Check if everything before is spaces and digits
+			prefix := line[:idx]
+			isLineNum := true
+			hasDigit := false
+			for _, ch := range prefix {
+				if ch >= '0' && ch <= '9' {
+					hasDigit = true
+				} else if ch != ' ' {
+					isLineNum = false
+					break
+				}
+			}
+			if isLineNum && hasDigit {
+				// Skip the arrow/tab character (→ is multi-byte)
+				if line[idx] == '\t' {
+					stripped = line[idx+1:]
+				} else {
+					// → is 3 bytes in UTF-8
+					stripped = line[idx+3:]
+				}
+			}
+		}
+
+		result = append(result, stripped)
+	}
+
+	return strings.Join(result, "\n")
 }
 
 // renderStoryStarted renders a story started marker.

internal/tui/log_test.go

@@ -171,3 +171,46 @@ func TestLogViewer_IsAutoScrolling(t *testing.T) {
 		t.Error("Expected IsAutoScrolling to remain true when at top")
 	}
 }
+
+func TestStripLineNumbers(t *testing.T) {
+	tests := []struct {
+		name     string
+		input    string
+		expected string
+	}{
+		{
+			name:     "arrow format",
+			input:    "   1→<?php\n   2→\n   3→use App\\Models;",
+			expected: "<?php\n\nuse App\\Models;",
+		},
+		{
+			name:     "tab format",
+			input:    "   1\t<?php\n   2\t\n   3\tuse App\\Models;",
+			expected: "<?php\n\nuse App\\Models;",
+		},
+		{
+			name:     "double digit line numbers",
+			input:    "  10→function test() {\n  11→    return true;\n  12→}",
+			expected: "function test() {\n    return true;\n}",
+		},
+		{
+			name:     "no line numbers",
+			input:    "<?php\nuse App\\Models;",
+			expected: "<?php\nuse App\\Models;",
+		},
+		{
+			name:     "empty string",
+			input:    "",
+			expected: "",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			result := stripLineNumbers(tt.input)
+			if result != tt.expected {
+				t.Errorf("stripLineNumbers() =\n%q\nwant:\n%q", result, tt.expected)
+			}
+		})
+	}
+}