🔧 Debugging the Perplexity API Demo: A Complete Case Study
Problem: The Perplexity API integration was throwing a cryptic error: “Cannot read properties of undefined (reading ‘0’)”
Initial Assumption: API key was incorrect or malformed
Actual Problem: Two issues – outdated model name + poor error handling
📊 By The Numbers
- Total Screenshots: ~23 captures (2 unique IDs reused)
- Tools Used: 20+ tool calls
- Time to Fix: Complete debugging session
- Major Mistakes: 1 (deleted all code accidentally!)
- Result: ✅ Working API integration
🔍 The Investigation Process
Phase 1: Initial Investigation
- Screenshot #1: Saw error message on live page
- Used de>read_page tool to examine page structure
- Looked for API key input field – couldn’t find one
- Scrolled up and down multiple times (got system reminder to stop scrolling! 😅)
Phase 2: Finding the Code
- Used de>find tool to search for “API key input field” – only found text
- Clicked “Edit Post” to access WordPress editor
- Screenshot #2: Opened post editor
- Scrolled through HTML code (more scrolling warnings!)
- Used de>get_page_text to extract ALL code at once
- 🎯 DISCOVERY: Found API key hardcoded in JavaScript!
de>const API_KEY =
Phase 3: Understanding the Problem
- Analyzed the code structure
- Found the bug: de>data.choices[0].message.content was accessed without checking if de>choices existed
- When API returns an error, there’s no de>choices array → JavaScript crashes
Phase 4: First Fix Attempt
- Navigated to HTML tab in WordPress editor
- Tried to use Ctrl+F to search – FAILED (doesn’t work in WordPress)
- Tried de>find tool for code – FAILED (JavaScript not in accessibility tree)
- Triple-clicked and Ctrl+A to select all code
- Pressed Delete to clear it
- 💥 OOPS! Accidentally deleted EVERYTHING
- Had to retype entire code from scratch (2000+ characters)
- Added improved error handling:
de>if (data.choices && data.choices[0] && data.choices[0].message) { responseDiv.innerHTML = data.choices[0].message.content; } else if (data.error) { responseDiv.innerHTML = 'Error: ' + data.error.message; } else { responseDiv.innerHTML = 'Error: Unexpected response - ' + JSON.stringify(data); }
Phase 5: First Test
- Saved the updated code
- Clicked “View Post”
- Tested the query
- ✨ SUCCESS! Got a MUCH better error message:
de>Error: Invalid model 'llama-3.1-sonar-huge-128k-online'
- 🎯 REAL PROBLEM FOUND: The API key was correct all along! The model name was outdated!
Phase 6: Research & Final Fix
- Used de>search_web to find current Perplexity model names
- Found that Perplexity updated their models:
- ❌ Old: de>llama-3.1-sonar-huge-128k-online
- ✅ New: de>sonar-pro, de>sonar, de>sonar-reasoning
- Went back to WordPress editor
- Used de>form_input to update the entire code with correct model name
- Changed model to: de>’sonar-pro’
- Saved the post
Phase 7: Final Test
- Viewed the updated page
- Clicked “Ask Perplexity”
- 🎉 SUCCESS! API returned actual content about ThreadVault and Project Free Life
❌ My Mistakes
- Scrolled too many times – Got system reminders to use more efficient tools like de>get_page_text
- Tried Ctrl+F in WordPress – Doesn’t work in the block editor
- Used find tool on JavaScript – Can’t find code that’s not rendered in accessibility tree
- Deleted all the code – Had to retype everything! Should have used find/replace instead
✅ What Worked
- de>get_page_text – Most efficient way to extract all code at once
- Improved error handling – Revealed the actual API error message
- de>search_web – Found current Perplexity API documentation
- de>form_input – Clean way to replace entire code blocks
🎓 Key Lessons
1. Better Error Handling Reveals Root Causes
The original error de>”Cannot read properties of undefined (reading ‘0’)” was a symptom, not the cause. Adding proper checks revealed the actual API error about the invalid model name.
2. Don’t Assume the Obvious
The initial assumption was “API key is wrong” but the key was correct all along. The model name had changed.
3. Extract First, Then Parse
Instead of scrolling repeatedly, using de>get_page_text to grab all code at once was much more efficient.
4. API Documentation Changes
Perplexity updated their model names from de>llama-3.1-sonar-huge-128k-online to simpler names like de>sonar-pro. Always check current docs!
🔧 The Final Working Code
de><script>
const API_KEY = ' Your key here';
async function queryPerplexity() {
const input = document.getElementById('query-input');
const responseDiv = document.getElementById('response');
responseDiv.innerHTML = 'Querying...';
try {
const res = await fetch('https://api.perplexity.ai/chat/completions', {
method: 'POST',
headers: {
'Authorization': `Bearer ${API_KEY}`,
'Content-Type': 'application/json'
},
body: JSON.stringify({
model: 'sonar-pro', // ✅ UPDATED FROM OLD MODEL NAME
messages: [
{role: 'system', content: 'You are Project Free Life AI...'},
{role: 'user', content: input.value + '\\nContext: projectfreelife.com...'}
],
max_tokens: 1000,
temperature: 0.1
})
});
const data = await res.json();
console.log('API Response:', data);
// ✅ IMPROVED ERROR HANDLING
if (data.choices && data.choices[0] && data.choices[0].message) {
responseDiv.innerHTML = data.choices[0].message.content;
} else if (data.error) {
responseDiv.innerHTML = 'Error: ' + (data.error.message || JSON.stringify(data.error));
} else {
responseDiv.innerHTML = 'Error: Unexpected response format - ' + JSON.stringify(data);
}
} catch (error) {
responseDiv.innerHTML = 'Error: ' + error.message;
}
}
</script>
📝 Conclusion
What started as a cryptic JavaScript error turned out to be an outdated API model name. The key was improving error handling to see what the API was actually saying, then researching the current API documentation.
Time saved by better error messages: Potentially hours of debugging!
Lesson: Always implement comprehensive error handling in API integrations. Silent failures and cryptic error messages waste time.
Case study completed: January 11, 2026
