perf: reduce []byte/string conversions and add ASCII fast paths

- bytes.NewReader instead of strings.NewReader(string(...)) in web search
- Consolidate multiple string(body) calls into single variable
- sb.Write(paramsJSON) instead of string conversion in CLI provider
- ASCII fast paths in Truncate/wrapLine before []rune conversion
- Byte-length truncation for ASCII-only branch names
- Extract runeDisplayWidth to avoid per-rune string(r) in wrap loop

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pkg/channels/telegram.go

@@ -1036,28 +1036,32 @@ func formatMarkdownTable(lines []string) string {
 	return strings.TrimRight(b.String(), "\n")
 }
 
+func runeDisplayWidth(r rune) int {
+	switch {
+	case r == '\u200d' || r == '\u200c' || r == '\ufe0f':
+		return 0
+	case unicode.Is(unicode.Mn, r):
+		return 0
+	case isEmojiRune(r):
+		return 3
+	case unicode.In(r,
+		unicode.Han,
+		unicode.Hiragana,
+		unicode.Katakana,
+		unicode.Hangul):
+		return 2
+	case (r >= 0x3000 && r <= 0x303F) || (r >= 0xFF00 && r <= 0xFFEF):
+		// CJK symbols/punctuation and half/fullwidth forms.
+		return 2
+	default:
+		return 1
+	}
+}
+
 func displayWidth(s string) int {
 	w := 0
 	for _, r := range s {
-		switch {
-		case r == '\u200d' || r == '\u200c' || r == '\ufe0f':
-			continue
-		case unicode.Is(unicode.Mn, r):
-			continue
-		case isEmojiRune(r):
-			w += 3
-		case unicode.In(r,
-			unicode.Han,
-			unicode.Hiragana,
-			unicode.Katakana,
-			unicode.Hangul):
-			w += 2
-		case (r >= 0x3000 && r <= 0x303F) || (r >= 0xFF00 && r <= 0xFFEF):
-			// CJK symbols/punctuation and half/fullwidth forms.
-			w += 2
-		default:
-			w++
-		}
+		w += runeDisplayWidth(r)
 	}
 	return w
 }
@@ -1092,7 +1096,7 @@ func wrapByDisplayWidth(s string, maxWidth int) []string {
 			flush()
 			continue
 		}
-		rw := displayWidth(string(r))
+		rw := runeDisplayWidth(r)
 		if rw == 0 {
 			cur.WriteRune(r)
 			continue

pkg/git/worktree.go

@@ -67,12 +67,11 @@ func SanitizeBranchName(task string) string {
 		s = "worktree"
 	}
 
-	// Truncate to 40 chars
-	runes := []rune(s)
-	if len(runes) > 40 {
-		runes = runes[:40]
+	// Truncate to 40 chars (ASCII fast path: branch names are ASCII after sanitization)
+	if len(s) > 40 {
+		s = s[:40]
 	}
-	s = strings.TrimRight(string(runes), "-")
+	s = strings.TrimRight(s, "-")
 
 	return "plan/" + s
 }

pkg/providers/claude_cli_provider.go

@@ -130,7 +130,9 @@ func (p *ClaudeCliProvider) buildToolsPrompt(tools []ToolDefinition) string {
 		}
 		if len(tool.Function.Parameters) > 0 {
 			paramsJSON, _ := json.Marshal(tool.Function.Parameters)
-			sb.WriteString(fmt.Sprintf("Parameters:\n```json\n%s\n```\n", string(paramsJSON)))
+			sb.WriteString("Parameters:\n```json\n")
+			sb.Write(paramsJSON)
+			sb.WriteString("\n```\n")
 		}
 		sb.WriteString("\n")
 	}

pkg/tools/web.go

@@ -278,7 +278,7 @@ func (p *PerplexitySearchProvider) Search(ctx context.Context, query string, cou
 		return "", fmt.Errorf("failed to marshal request: %w", err)
 	}
 
-	req, err := http.NewRequestWithContext(ctx, "POST", searchURL, strings.NewReader(string(payloadBytes)))
+	req, err := http.NewRequestWithContext(ctx, "POST", searchURL, bytes.NewReader(payloadBytes))
 	if err != nil {
 		return "", fmt.Errorf("failed to create request: %w", err)
 	}
@@ -534,6 +534,7 @@ func (t *WebFetchTool) Execute(ctx context.Context, args map[string]any) *ToolRe
 
 	var text, extractor string
 
+	bodyStr := string(body)
 	if strings.Contains(contentType, "application/json") {
 		var jsonData any
 		if err := json.Unmarshal(body, &jsonData); err == nil {
@@ -541,15 +542,15 @@ func (t *WebFetchTool) Execute(ctx context.Context, args map[string]any) *ToolRe
 			text = string(formatted)
 			extractor = "json"
 		} else {
-			text = string(body)
+			text = bodyStr
 			extractor = "raw"
 		}
 	} else if strings.Contains(contentType, "text/html") || len(body) > 0 &&
-		(strings.HasPrefix(string(body), "<!DOCTYPE") || strings.HasPrefix(strings.ToLower(string(body)), "<html")) {
-		text = t.extractText(string(body))
+		(strings.HasPrefix(bodyStr, "<!DOCTYPE") || strings.HasPrefix(strings.ToLower(bodyStr), "<html")) {
+		text = t.extractText(bodyStr)
 		extractor = "text"
 	} else {
-		text = string(body)
+		text = bodyStr
 		extractor = "raw"
 	}
 

pkg/utils/string.go

@@ -47,6 +47,10 @@ func TailPad(s string, n, wrapWidth int) string {
 // wrapLine splits a single line into segments of at most width runes.
 // An empty line produces one empty string (preserving blank lines).
 func wrapLine(line string, width int) []string {
+	// ASCII fast path: byte length == rune length for pure ASCII
+	if len(line) <= width {
+		return []string{line}
+	}
 	runes := []rune(line)
 	if len(runes) <= width {
 		return []string{line}
@@ -97,6 +101,10 @@ func Truncate(s string, maxLen int) string {
 	if maxLen <= 0 {
 		return ""
 	}
+	// ASCII fast path: byte length == rune length for pure ASCII
+	if len(s) <= maxLen {
+		return s
+	}
 	runes := []rune(s)
 	if len(runes) <= maxLen {
 		return s