Thanks — you're asking how to subscribe to SIP events like the example you shared (callId, callStatus, sip.* attributes). I’ll explain what you can and can’t subscribe to, and the recommended ways to receive the SIP lifecycle updates you need. Short answer • You cannot subscribe to raw SIP signaling messages (INVITE, 486 Busy Here, full SIP dumps). That low-level SIP traffic is internal to LiveKit’s SFU. • You can reliably receive SIP lifecycle and status information via: ◦ Webhooks for join/leave/room lifecycle events, and ◦ Participant attribute updates (e.g.,

sip.callStatus

,

sip.callID

) via client/agent event listeners or by polling the server SDK (list participants). How to get the SIP events you care about 1) Webhooks — for call start / end and room lifecycle • Configure a webhook URL for your LiveKit project or deployment. LiveKit sends events like

participant_joined

,

participant_left

,

room_started

, and

room_finished

. • Use

participant_joined

and

participant_left

to detect when a SIP caller enters or leaves a room. • Webhooks include participant attributes so you’ll get

sip.*

attributes available on the participant payload. • Verify webhook signatures (HMAC-SHA256) before processing. When to use: Good for asynchronous notifications (e.g., logging, ticketing, billing, or triggering backend workflows when SIP calls connect/disconnect). 2) Participant attributes / event listeners — for real-time status changes • The

Participant

object exposes attributes such as

sip.callStatus

,

sip.phoneNumber

,

sip.callID

, etc. • Listen for attribute-change events in your LiveKit client or agent. Example events are

participant_attributes_changed

(or SDK-equivalent). • Typical flow:

dialing

→

ringing

→

active

→

hangup

(or

error

). Your handler can read

changed_attributes['sip.callStatus']

and react immediately. When to use: Real-time UI updates, call-state driven logic, or routing decisions while the call is in progress. 3) Server SDK snapshot (read-only) • Use the server SDK

ListParticipants

/

Room

API to read current participants and their attributes. This provides a snapshot of SIP state (e.g.,

sip.callID

,

sip.callStatus

) at query time. • Use this when you need to poll for current state or perform server-side reconciliation. When to use: Periodic checks, administrative dashboards, or if you missed a webhook and need current state. What you cannot get • Raw SIP message streams (INVITE, BYE, status lines, SIP-level debugging messages) are not exposed as a subscription. You will not receive SIP protocol dumps or the internal INVITE failure trace directly. • Instead, you get the resulting state (e.g.,

callStatus: "SCS_ERROR"

and participant left events). Extra: passing data back to the SIP side • If you need to provide data back to the SIP trunk/IVR (for example to include in a BYE), map participant attributes to SIP headers via

attributes_to_headers

on trunk config and set attributes with

update_participant

. Those mapped headers are sent on BYE or other trunk interactions. Example flows (high level) • To detect an outbound call error (like your example with "486 Busy Here"): a. Receive

participant_joined

for the SIP participant (or

participant_attributes_changed

). b. Watch

sip.callStatus

attribute changes; when it becomes an error state or you receive

participant_left

, record the error reason from attributes (e.g.,

sip.callStatus

/

callStatusCode

fields). c. Optionally fetch room participants via the server SDK if you need a snapshot. If you’d like, I can help with: • Example webhook payload and a small webhook handler in the language you prefer. • Example client/agent code to listen for

participant_attributes_changed

in the SDK you use (Web, Node, Python, Ruby, etc.). • How to map

attributes_to_headers

for your trunk so IVR receives routing attributes on BYE. Which would you like next, and which SDK/language are you using? Sources: server-sdk-ruby | livekit/livekit_composite | DeepWiki | SIP Lifecycle Management Agent | LiveKit Documentation | sip | livekit/livekit_composite | DeepWiki | How to do call transfers with Five9 | LiveKit | server-sdk-kotlin | livekit/livekit_composite | DeepWiki