Starting with Chrome version 142, users may experience "Failed to initialize Studio" errors with "TypeError: Failed to fetch" when trying to connect LangSmith Studio to their local development server via langgraph dev. This occurs even when the API server at http://127.0.0.1:2024/docs loads successfully.
Root Cause: Chrome 142 fully enforces the Private Network Access (PNA) specification with no fallback, which blocks HTTPS sites (like https://smith.langchain.com) from accessing HTTP localhost servers by default.
Symptoms
Running
langgraph devorlanggraph dev --allow-blockingstarts the server successfullyNavigating to http://127.0.0.1:2024/docs shows the API documentation correctly
LangSmith Studio at https://smith.langchain.com shows: "Failed to initialize Studio - Please verify if the API server is running or accessible from the browser. TypeError: Failed to fetch"
Browser console shows errors like:
Permission was denied for this request to access the 'unknown' address space
Solution
Quick Fix: Allow Local Network Access in Chrome
Open LangSmith Studio at https://smith.langchain.com in Chrome
Click the lock icon (or site information icon) to the left of the address bar
Look for the "Local network access" option in the dropdown
Change the setting from "Ask (default)" or "Block" to "Allow"
Reload the page
The Studio should now connect to your local development server successfully.
Additional Troubleshooting
Check for Browser Extension Conflicts
Browser extensions (especially Ollama Chrome extension or AI model extensions) can interfere with localhost connections:
Disable all browser extensions temporarily
Restart Chrome
Try connecting to Studio again
If it works, re-enable extensions one by one to identify the culprit
Verify Dependencies Are Up to Date
pip install -U "langgraph-cli[inmem]"Clear Browser Cache and Site Data
In Chrome, go to Settings > Privacy and Security > Site Settings
Find https://smith.langchain.com in the list
Click "Clear data"
Restart Chrome and try again