I have an outbound caller. I need it to delay its greeting by 2 seconds after tha particpant connects to the call.

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I want to agent to immediately talk if someone does say something within those two seconds. Otherwise, the agent should wait two seconds.

Thanks — that makes sense. You want the agent to wait up to 2 seconds before playing its greeting, but if the participant speaks during that window the agent should cancel the wait and respond immediately. I can help you implement that. Quick clarifying questions so I give the exact code you need: • Which runtime are you using: Python or Node.js? • Is VAD (voice activity detection) already enabled for this session, or do you need instructions to enable it? • Is the greeting TTS generated at runtime or a pre-recorded audio file you want played? High-level approach (what I’ll implement once you confirm language and VAD): 1. Start a 2-second timer right after the participant connects or the call is answered. 2. Subscribe to the user-speaking event (VAD /

user_started_speaking

/

user_state_changed

). 3. If the user speaks within 2 seconds: ◦ Cancel the timer and immediately call your reply/send-greeting routine. 1. If the timer completes without speech: ◦ Play or generate the greeting. If you want, I can provide: • A complete Python example using asyncio and

user_state_changed

. • A Node.js example using Promises and the equivalent speaking event. • Extra detail on enabling VAD and making sure only one response plays (race/cancel handling). Tell me which language and whether VAD is available, and I’ll send the tailored code snippet. Sources: Turns overview | LiveKit Documentation | Agent Builder | LiveKit Documentation | Agent speech and audio | LiveKit Documentation | How does LiveKit Agents compare to Pipecat? | LiveKit | Agents telephony integration | LiveKit Documentation

I am using Python and have vad set up already. The greeting is generated at runtime

Thanks — great details. Since you’re using Python, have VAD enabled, and generate the greeting at runtime (TTS), here’s a concise, ready-to-use pattern you can drop into your agent session. It: • Starts a 2-second timer after the participant connects/answer. • Listens for the user-speaking VAD event. • Cancels the timer and responds immediately if the user speaks within 2 seconds. • Otherwise, runs the 2-second delay and then generates the greeting. Example (Python, asyncio):

import asyncio

# Assume session is your AgentSession with VAD enabled and TTS available.
# This function runs after call is answered / participant connected.

async def conditional_greeting(session):
    delay = 2.0
    delay_task = None

    async def delayed_greet():
        try:
            await asyncio.sleep(delay)
            # No user speech detected within 2s -> generate greeting
            await session.generate_reply(instructions="Hello! How can I help you today?")
        except asyncio.CancelledError:
            # Delay cancelled because user spoke
            return

    # Handler for VAD/user speaking event
    @session.on("user_state_changed")
    async def _on_user_state_changed(ev):
        nonlocal delay_task
        # Adjust the speaking-state check to match your event shape
        if getattr(ev, "new_state", None) == "speaking":
            # User started speaking within the window -> cancel delay and reply now
            if delay_task and not delay_task.done():
                delay_task.cancel()
            # Immediately respond to the user's input; avoid awaiting here
            # to keep event loop responsive, create a task for the reply
            asyncio.create_task(
                session.generate_reply(instructions="Respond to user's speech immediately.")
            )

    # Start the delayed greeting
    delay_task = asyncio.create_task(delayed_greet())

    # Optionally: await session lifecycle if needed, or return so caller continues.
    # If you need to wait until the greeting or reply finishes, you can await delay_task.

Notes and tips • Use

asyncio.create_task

for immediate replies so the event handler returns quickly and the loop stays responsive. • The

user_state_changed

event above expects

ev.new_state == "speaking"

. If your VAD event uses a different field or event name (e.g.,

user_started_speaking

), adjust accordingly. • If you want the immediate reply to take the user’s utterance into account (e.g., include recently captured audio for context), ensure your STT pipeline captures the user audio and is available to

session.generate_reply

. • To avoid duplicate replies in edge cases, check whether a reply is already in progress (for example, track a boolean

reply_in_progress

) before starting another

generate_reply

. If you’d like, I can: • Adapt this snippet to your exact event object shape (paste a sample

user_state_changed

event structure). • Show how to include the user’s immediate audio/text as context in

session.generate_reply

.

The issue is for outbound calls, the caller may take a while to accept the call; however the conditional greeting starts when the session starts

Thanks — that clarification helps. You’re right: for outbound SIP calls you should start the 2‑second conditional greeting only after the call is actually answered / the participant is connected, not when the session starts. Below is a focused Python pattern you can drop into your outbound flow. Key points: • Wait until the SIP participant is answered/connected (use

wait_until_answered=True

when creating the SIP participant or listen for the participant-connected event). • Start the 2s conditional timer only after you detect the participant is connected/answered. • Listen for VAD

user_state_changed

(speaking) during that 2s window and cancel the delay if the user speaks. • Generate the greeting immediately if speech is detected, otherwise generate it when the timer completes. Example (Python, asyncio) — adapt names to your codebase:

import asyncio

async def place_outbound_and_conditional_greet(ctx, phone_number, session):
    # Create outbound SIP participant and wait until it's answered
    await ctx.api.sip.create_sip_participant(
        api.CreateSIPParticipantRequest(
            room_name=ctx.room.name,
            sip_trunk_id='your-trunk-id',
            sip_call_to=phone_number,
            participant_identity=phone_number,
            wait_until_answered=True  # ensures this call returns after answer
        )
    )

    # At this point the remote participant has answered / connected.
    # Start the conditional greeting logic now.
    delay = 2.0
    delay_task = None
    greeting_sent = False
    reply_lock = asyncio.Lock()  # prevent duplicate replies

    async def delayed_greet():
        nonlocal greeting_sent
        try:
            await asyncio.sleep(delay)
            async with reply_lock:
                if not greeting_sent:
                    greeting_sent = True
                    await session.generate_reply(instructions="Hello! How can I help you today?")
        except asyncio.CancelledError:
            return

    @session.on("user_state_changed")
    async def _on_user_state_changed(ev):
        nonlocal delay_task, greeting_sent
        # adjust this check if your event uses a different field
        if getattr(ev, "new_state", None) == "speaking":
            # User spoke within the window -> cancel delay and reply immediately
            if delay_task and not delay_task.done():
                delay_task.cancel()
            async with reply_lock:
                if not greeting_sent:
                    greeting_sent = True
                    # If you want the reply to use captured user audio/text, include it here
                    asyncio.create_task(
                        session.generate_reply(instructions="Respond to the user's speech right away.")
                    )

    # Start the delayed greeting after the call was answered
    delay_task = asyncio.create_task(delayed_greet())

    # Optionally await the greeting to finish or return so other session work continues
    # await delay_task

If you cannot or do not want to use

wait_until_answered=True

, instead: • Create the SIP participant without waiting. • Subscribe to the participant-connected event for that participant (or to room

participant_connected

) and start the conditional greeting from that event handler when you see the specific outbound participant connect. Would you like the version that starts from a participant-connected event instead of

wait_until_answered

? If so, paste the shape of your participant connected event (or the field that identifies your outbound participant) and I’ll adapt the handler to start the 2s window only for that participant.

wait_until_answered still has participant_connected when the dial goes out not when the call is accepted.

Thanks — that’s a helpful clarification. You’re correct: for outbound SIP the room-level

participant_connected

can happen when the dial starts, so you must start the 2‑second conditional greeting only when the SIP call is actually answered (when

sip.callStatus

becomes

active

). Below is a focused Python pattern you can drop into your outbound flow. It assumes: • You have VAD enabled and the

user_state_changed

event is fired when the remote participant starts speaking. • Your code can observe

participant_attributes_changed

(or similar) and inspect

sip.callStatus

. • Greetings are generated at runtime with

session.generate_reply()

. What it does • Listens for

participant_attributes_changed

for SIP participants and starts the 2s window only when

sip.callStatus == "active"

. • Starts a 2s timer that will send the greeting if no speech is detected. • Cancels the timer and responds immediately if VAD signals the participant started speaking within the window. • Uses a lock/flag to avoid duplicate replies. Example (Python, asyncio):

import asyncio

async def outbound_conditional_greeting(ctx, phone_number, session):
    # Create SIP participant (no assumptions about wait_until_answered)
    await ctx.api.sip.create_sip_participant(
        api.CreateSIPParticipantRequest(
            room_name=ctx.room.name,
            sip_trunk_id='your-trunk-id',
            sip_call_to=phone_number,
            participant_identity=phone_number,
            # you can set wait_until_answered=False or True depending on flow;
            # this example relies on sip.callStatus updates instead of wait_until_answered
        )
    )

    greeting_delay = 2.0
    greeting_sent = False
    greeting_task: asyncio.Task | None = None
    reply_lock = asyncio.Lock()

    async def delayed_greet():
        nonlocal greeting_sent
        try:
            await asyncio.sleep(greeting_delay)
            async with reply_lock:
                if not greeting_sent:
                    greeting_sent = True
                    await session.generate_reply(instructions="Hello! How can I help you today?")
        except asyncio.CancelledError:
            return

    @session.on("user_state_changed")
    async def on_user_state_changed(ev):
        nonlocal greeting_sent, greeting_task
        # adapt field name if your event uses a different attribute
        if getattr(ev, "new_state", None) == "speaking":
            # User spoke during the window -> cancel timer and respond immediately
            if greeting_task and not greeting_task.done():
                greeting_task.cancel()
            async with reply_lock:
                if not greeting_sent:
                    greeting_sent = True
                    # Use create_task so the handler returns quickly
                    asyncio.create_task(
                        session.generate_reply(instructions="Responding to your question right away.")
                    )

    # Room-level handler: look for sip.callStatus -> "active"
    @ctx.room.on("participant_attributes_changed")
    async def on_participant_attributes_changed(participant, attributes):
        nonlocal greeting_task, greeting_sent
        # Only care about SIP participants (adjust check to your participant object)
        if getattr(participant, "kind", None) != "sip":
            return

        new_status = attributes.get("sip.callStatus")
        # When status becomes "active", start the 2-second conditional window
        if new_status == "active" and not greeting_sent:
            # Start the timer only when call is truly answered (sip.callStatus == "active")
            greeting_task = asyncio.create_task(delayed_greet())

Notes and tips • If your SDK represents participant kind or events differently, replace

"sip"

and event argument shapes with your actual objects/fields. • If you want to include the user’s immediate speech content in the immediate reply, ensure your STT buffer is accessible to

session.generate_reply()

and include that transcription in the request. • Keep the event handler lightweight; use

asyncio.create_task

for longer operations so the event loop stays responsive. • Use the reply lock and

greeting_sent

flag to avoid duplicate replies in race scenarios. If you’d like, I can: • Adapt this snippet to the exact shapes your SDK returns (paste a real

participant_attributes_changed

payload and the

user_state_changed

event object). • Show an alternate flow that uses

wait_until_answered=True

plus attribute polling if you prefer that pattern. Sources: SIP Lifecycle Management Agent | LiveKit Documentation