Instruction file imported from 3b3ziz/not-to-disappear-extension (.cursor/rules/extension-development.mdc). Copyright stays with the author.

Chrome Extension Development Guidelines

Content Script Patterns

• DOM Observation: Use MutationObserver with debouncing for ChatGPT's dynamic content
• Streaming Detection: Only check for ChatGPT's "Stop generating" button - avoid text-based heuristics
• Button Injection: Wait for action buttons container with proper flex layout detection
• PostMessage Bridge: Secure communication between web app and extension

Storage Patterns

• Local Only: Use chrome.storage.local for all data persistence
• No External APIs: Never send data to external servers
• User Privacy: All data stays on user's device

Performance Considerations

• Debouncing: Use timeouts to prevent excessive DOM processing
• Efficient Selectors: Use specific selectors to avoid false positives
• Minimal DOM Queries: Cache results and avoid repeated queries

Error Handling

• Graceful Degradation: Extension should work even if some features fail
• User Feedback: Provide clear error messages and success indicators
• Console Logging: Use consistent logging patterns for debugging

Security

• No Hardcoded Secrets: All API keys and URLs should be empty for local-only operation
• Content Security: Sanitize user input and escape HTML
• PostMessage Validation: Only accept messages from same origin