feat: add configurable user agent support

[stickerdaniel]

Summary

• Add --user-agent CLI argument and USER_AGENT environment variable support
• Implement platform-specific default user agents (Windows, macOS, Linux)
• Update configuration schema and loaders to support user agent customization
• Add user agent documentation to readme

Addresses Issues

• Closes [FEATURE] Option to set useragent #27: Option to set useragent
• Should help with [BUG] Cookie authentication fails with "cookie may be expired or invalid" on Windows #26: Cookie authentication fails on Windows

Changes

• Configuration: Added user_agent field to ChromeConfig schema
• CLI: Added --user-agent argument with help text
• Environment: Added USER_AGENT environment variable support
• Platform Detection: Automatic platform-specific user agents to reduce fingerprinting
• Documentation: Updated README.md

[claude]

Claude finished @stickerdaniel's task —— View job

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Code Review Complete ✅

I've thoroughly reviewed the configurable user agent support implementation. Overall, this is a well-implemented feature that follows the existing codebase patterns and addresses the stated requirements effectively.

✅ Strengths

Clean Architecture

• Follows established configuration layering pattern (CLI → ENV → defaults)
• Consistent with existing code style and naming conventions
• Proper separation of concerns across modules

Platform-Aware Design

• Smart platform-specific default user agents to reduce fingerprinting
• Helps address anti-scraping measures LinkedIn may employ
• Good fallback strategy (custom → platform default)

Configuration Flexibility

• Multiple input methods: --user-agent CLI arg and USER_AGENT env variable
• Well-integrated into existing configuration system
• Proper precedence handling

⚠️ Areas for Improvement

1. Hardcoded Chrome Version drivers/chrome.py:38-42

# Current implementation has fixed version numbers
"Chrome/137.0.0.0 Safari/537.36"

Issue: Chrome version 137.0.0.0 will become outdated quickly, potentially making the user agent less effective against anti-bot detection.

Recommendation: Consider using a more dynamic approach or documenting the need for periodic updates.

2. Input Validation Missing config/loaders.py:274-275

if args.user_agent:
    config.chrome.user_agent = args.user_agent  # No validation

Issue: No validation on user-provided user agent strings.

Recommendation: Add basic validation to ensure the user agent string doesn't contain potentially problematic characters or is excessively long.

3. Minor Performance Optimization drivers/chrome.py:88

user_agent = config.chrome.user_agent or get_default_user_agent()

Issue: get_default_user_agent() is called every time create_chrome_options() runs, even though platform doesn't change.

Recommendation: Consider caching the default user agent since platform detection is static during execution.

🔒 Security Assessment

• Low Risk: User agent strings are passed as Chrome arguments, which provides good isolation
• Input Sanitization: Consider basic validation, though Chrome argument handling provides some protection
• Anti-Detection: Platform-specific defaults are a good security practice

🧪 Test Coverage Recommendations

The PR lacks test coverage for the new functionality. Consider adding tests for:

1. Platform Detection Logic

   def test_get_default_user_agent_by_platform()

2. Configuration Precedence

   def test_user_agent_precedence_cli_over_env()
   def test_user_agent_precedence_env_over_default()

3. Edge Cases

   def test_empty_user_agent_string()
   def test_very_long_user_agent_string()

📝 Minor Suggestions

1. Documentation: Consider adding an example user agent string in the CLI help text
2. Constants: The Chrome version numbers could be extracted to constants for easier maintenance
3. Logging: Consider adding debug logging when custom user agents are applied

🎯 Overall Assessment

This is a solid implementation that:

• ✅ Addresses the stated requirements (issues [FEATURE] Option to set useragent #27 and [BUG] Cookie authentication fails with "cookie may be expired or invalid" on Windows #26)
• ✅ Maintains code quality standards
• ✅ Follows established patterns
• ✅ Provides meaningful functionality for anti-detection

The identified issues are minor and don't block the functionality. The feature works as intended and provides good value for users dealing with LinkedIn's anti-scraping measures.

Recommendation: ✅ Approve with minor suggestions - The implementation is ready for merge, with the suggested improvements being candidates for future enhancements rather than blocking issues.

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