One Browser Tab Observes Only One Network Perspective
Opening this page tests the network interface used by your current browser. A remote SSH host, cloud VM, or WSL2 instance with NAT networking has its own routing table and DNS.
Record Which Environment Exhibited the Issue
Note whether the failure occurred in "Local Browser Web" or "Remote SSH CLI API" along with the target hostname and timestamp.
LAN Private Addresses Differ from Public NAT Exits
Local RFC 1918 / CGNAT addresses are filtered out by our public IP validator; only routable public IPv4/IPv6 addresses are compared.
Match the Diagnostic Check to the Environment
Use browser and split-routing checks for web issues, dual-stack checks for IPv6 bypasses, and terminal curl/trace checks on remote servers for CLI issues.
Common Real-World Scenario
For example, your local browser may use a residential ISP while your remote SSH box exits through a datacenter ASN—both are accurate for their respective machines.
Repeat checks where requests actually originate
Map the actual execution path: the browser is local, while Claude Code may run in a terminal, WSL, a container, or an SSH host. Each context can have different environment variables, resolvers, and routes. Do not use the local browser's public address as the remote server's measured exit.
In the relevant terminal, check whether proxy variables exist, whether their endpoints are reachable, and which machine localhost refers to. Inside WSL, a container, or an SSH host, loopback does not automatically refer to the desktop proxy. Review the listening scope and documentation without exposing the proxy to untrusted networks.
For example, when the desktop browser works but a remote API call times out, retain DNS, connectivity, and error evidence from the remote environment. Investigate that environment's proxy path first. Change one setting at a time and record execution location, destination, time, and result. Measurements from different contexts are not a controlled before-and-after comparison.
References & Freshness
The above is independent diagnostic guidance with no access to Anthropic internal risk controls. Policies, UIs, and support workflows may change—always verify against official effective dates and your account portal.