Test Where Calls Go When Your 3CX AI Agent Is Unavailable

Use a controlled API-key test to confirm your AI-unavailable backup route works, separately from Human Handoff.

Test your AI-unavailable route on its own before callers depend on it. In V20 Update 10, the AI unavailable setting sends calls to a backup destination when 3CX detects that the AI service cannot respond. This blog shows you how to trigger that condition safely on a test PBX and confirm exactly where those calls go.

Why Human Handoff Does Not Prove Your Backup Route

A successful Human Handoff only proves that the AI can transfer a call while it is working. It does not confirm the route 3CX uses when the AI service cannot respond at all, because the two settings react to different conditions and are configured in different places.

Human Handoff handles a conversation the AI cannot resolve, or a general request to speak to a person without enough detail for more specific routing. The AI is working and can transfer the call. Set this destination in the Customer Service Agent’s Call Routing tab.

AI unavailable handles failures that prevent the AI service from responding, including network connectivity problems and authentication/authorization failures. Set this backup destination in the agent’s Options tab. You can choose Transfer to a configured destination or End Call; this blog uses the transfer option

Because each route has its own trigger, each one needs its own test.

Example: Test Both Routes with Two Different Destinations

Giving each route a different destination makes the result easy to read: whoever answers the call tells you which route it took.

This example uses a Customer Service AI Agent and two human Support colleagues on separate extensions in an isolated test PBX. It compares a normal conversation, Human Handoff and a temporary API-key failure, then checks that normal service returns.

Set Human Handoff to Support colleague A on extension 101 and AI unavailable to Support colleague B on extension 102. These numbers are illustrative; use two different direct human extensions on your test PBX. For technical details, see the AI Customer Service Agent and AI Agent configuration guides.

Prepare the Test

Use an AI Edition test PBX running V20 Update 10 with a separate AI provider configuration. Changing a shared API key can affect other agents that use it, so do not run this test against production credentials. Make sure you can restore the working key securely before you change anything.

Prepare one question with a known answer in the agent’s knowledge sources and one it cannot resolve. Keep specialist Escalation Topics out of these requests. Then call extensions 101 and 102 directly to confirm that both colleagues are available to answer.

Run the Calls

Run the healthy cases first. Then temporarily replace the working provider API key with an invalid key on the test PBX and save it. The key is checked when the provider is used, not when it is saved. Call the AI agent through the same incoming route you used for the healthy calls and check that the detected failure sends the call to colleague B on extension 102. Restore the working key immediately after this case, even if the call fails unexpectedly.

Use these expected outcomes as your test sheet. They are illustrative checks.