[nitpick] Incomplete file extension mapping. The extMap only includes a small subset of common extensions. Files with other extensions like .go, .rs, .java, .cpp, .c, .sh, .json, .xml, .html, .css, etc. will fall back to their raw extension, which may not be recognized by markdown renderers.

Consider either:

1. Expanding the mapping to include more common extensions
2. Documenting that only these specific extensions are mapped
3. Using a library like linguist-languages for comprehensive language detection

The diff formatting for the Edit tool will produce incorrect output when the old_string or new_string contains multiple lines. The current logic prepends - or + to newlines within the string, but the first line doesn't get the prefix. For example, a 3-line old_string would result in:

-line1
-line2
-line3

But it should be:

-line1
-line2
-line3

Consider using:

const oldStr = typedInput.old_string.split('\n').map(line => `-${line}`).join('\n');
const newStr = typedInput.new_string.split('\n').map(line => `+${line}`).join('\n');
parts.push(`\`\`\`diff\n${oldStr.trimEnd()}\n${newStr.trimEnd()}\n\`\`\``);

Potential XSS vulnerability: User-provided content from file paths, tool inputs, and tool results is directly interpolated into markdown without sanitization. Malicious JSONL files could inject arbitrary HTML/JavaScript through fields like file_path, description, url, query, or tool result content.

For example:

• A file path like `<script>alert('xss')</script>` would be rendered directly in markdown
• Tool result content could contain malicious HTML that gets rendered when the markdown is converted to HTML

Consider sanitizing user-provided content before embedding it in markdown, especially for fields that will be rendered as HTML or could contain special characters.

Missing JSDoc documentation for the public API function. This function is exported and used by other modules, so it should have documentation explaining:

• What the function does
• What the path parameter represents (file path to a .jsonl file)
• What it returns (array of parsed JSONL lines)
• What errors it may throw (file not found, invalid JSON, schema validation errors)

Example:

/**
 * Parses a Claude Code JSONL file from the given file path.
 * @param filePath - Path to the .jsonl file containing Claude Code conversation logs
 * @returns Array of validated JSONL line objects
 * @throws {Error} If file cannot be read, JSON is malformed, or schema validation fails
 */
export function parseJsonlFromPath(filePath: string): JsonlLine[] {

Missing blank line within details block could cause rendering issues. HTML <details> blocks in markdown should have blank lines before and after the code block for proper markdown parsing. The current implementation might not render correctly in some markdown processors.

Consider:

parts.push("<details><summary>Output</summary>");
parts.push("");  // blank line
parts.push(`\`\`\`\n${cleanedContent.trim()}\n\`\`\``);
parts.push("");  // blank line
parts.push("</details>");

Missing JSDoc documentation for the complex rendering function. Given the complexity of this function with multiple tool types and rendering logic, it should have documentation explaining:

• The purpose of the function
• The structure of the lines parameter
• What markdown format is returned
• Any special rendering rules or transformations applied

Example:

/**
 * Renders an array of Claude Code JSONL lines into markdown format.
 * Merges consecutive messages from the same sender and formats tool uses with appropriate code blocks.
 * @param lines - Array of parsed JSONL line objects from a Claude Code conversation
 * @returns Markdown string representation of the conversation
 */
export function renderFromLines(lines: JsonlLine[]): string {

[nitpick] The function name getFileExtension is misleading. The function doesn't just get the file extension—it also maps common extensions to their full language names (e.g., "ts" → "typescript"). A more accurate name would be getLanguageIdentifier, getSyntaxHighlighter, or getCodeBlockLanguage to reflect that it returns a language identifier for markdown code blocks, not just the raw file extension.

[nitpick] Magic strings for tool names are scattered throughout the switch statement. If tool names change or new tools are added, these strings must be updated in multiple places. Consider defining these as constants at the top of the file or in a separate constants module:

const TOOL_NAMES = {
	READ: 'Read',
	WRITE: 'Write',
	EDIT: 'Edit',
	BASH: 'Bash',
	GLOB: 'Glob',
	GREP: 'Grep',
	TODO_WRITE: 'TodoWrite',
	TASK: 'Task',
	WEB_FETCH: 'WebFetch',
	WEB_SEARCH: 'WebSearch',
} as const;

Then use case TOOL_NAMES.READ: instead of case "Read":.

[nitpick] The provider detection logic is too simplistic. Any file ending with .jsonl is assumed to be a Claude Code file. This could lead to false positives if:

1. Other providers also use .jsonl format
2. Users have unrelated .jsonl files that don't conform to the Claude Code schema

Consider adding additional validation beyond just the file extension, such as:

• Checking for Claude Code-specific markers in the first few lines
• Attempting to parse with the schema and falling back to error if it doesn't match
• Documenting that .jsonl files must be Claude Code format

[nitpick] The positional parameter name is still url but now also accepts local file paths. Consider renaming the parameter to urlOrPath or source to better reflect that it accepts both URLs and local file paths. This would make the API more intuitive:

command: "url2md <source>",
// ...
.positional("source", {
	type: "string",
	description: "URL or local file path (e.g., .jsonl for Claude Code)",
	demandOption: true,
})