Starting a silent listen with the blind_monitor API

Supervisors regularly want to quietly listen in on a live call to coach or to spot-check quality. The blind_monitor function on the VICIdial Non-agent API does this: it calls a phone you choose and places it into a live Agent session as a silent listener. It is served by non_agent_api.php and is the API path to Call monitoring without sitting in the admin UI. For the bigger map of every endpoint, see the VICIdial API and AGI overview.

When you'd use it

Reach for it from a supervisor dashboard that has a "listen" button next to each live agent. The same call also supports stepping up from silent listening to talking — joining the call so both the agent and the customer hear you, which is how you turn a quiet listen into Whisper coaching or a full Barge-in. Because it dials a real phone, the listener can be on a desk handset, a softphone, or any number your dialplan can reach.

How the call works

sequenceDiagram
  participant App
  participant API as non_agent_api.php
  participant V as VICIdial
  participant Sup as Supervisor phone
  App->>API: blind_monitor (phone_login, session_id)
  API->>V: launch monitor into session
  V->>Sup: dial supervisor phone
  Sup-->>V: answers and listens
  V-->>App: SUCCESS launched

You tell it which phone to ring and which session to join. VICIdial dials that phone and bridges it into the target agent's live call in the stage you requested. A SUCCESS line confirms the launch — for example SUCCESS: blind_monitor HAS BEEN LAUNCHED followed by the phone and session details.

Parameters

Required fields:

• phone_login — the listening phone's login, alpha-numeric, no spaces or special characters
• session_id — the target agent's session, all numbers, 7 digits
• server_ip — the server's IP, all numbers and dots, max 15 characters
• source — a short description of what made the call, maximum 20 characters
• stage — MONITOR, BARGE (or BARGESWAP) or HIJACK; default is MONITOR (HIJACK is not currently functional)

An example call

http://server/vicidial/non_agent_api.php?source=test&user=6666&pass=1234&function=blind_monitor&phone_login=350a&session_id=8600051&server_ip=10.10.10.16&stage=MONITOR

That dials phone 350a and drops it silently into session 8600051. Set stage to BARGE to be heard by both parties, or BARGESWAP to swap audio so you talk to the agent. Leave it at MONITOR for a true silent listen. On success you get the LAUNCHED line; common errors are INVALID PHONE LOGIN if the phone login is wrong and INVALID SESSION ID if the agent's session number is off by a digit.

Permissions and a gotcha

The api user must have user_level 7 or higher, or you get NO PERMISSION TO BLIND MONITOR — the same requirement laid out in VICIdial API user-level permissions. The detail that trips people up is the session_id: it is the agent's live 7-digit session, not their user id and not their phone extension — so you usually fetch it first with the agent_status function, which returns that exact session_id. Also note HIJACK is accepted as a stage but is not currently functional, so do not build a workflow around it. And monitoring a live call has legal weight — make sure your call recording and consent posture matches the two-party rules where your customers are.

A scripted silent-listen button turns quality monitoring from a chore into a click. If you would rather not run the VICIdial box behind these endpoints, our managed servers are ready in under 40 seconds — see our pricing — or read the companion you will likely call first, reading one agent's live status.