what is preemptive_generation
# ask-ai
b
what is preemptive_generation
t
Thanks for reaching out, Utkarsh. I'm an AI assistant and I'm here to help. Give me a moment while I research this topic.
Thanks — I’m happy to explain. Preemptive_generation is a feature for LiveKit agents that begins generating a response before the user’s turn is fully finished. As soon as a partial (or final) transcript is available from speech-to-text, the agent starts LLM inference so it can reply faster once the user stops speaking. Key points: • Enable it by setting
preemptive_generation=True
in the
AgentSession
configuration. • It can reduce perceived response latency and improve conversational flow when transcripts arrive before voice activity detection marks end-of-speech. • If the chat context or tools change while the agent is precomputing (for example during
on_user_turn_completed
), the preemptive response is canceled and regenerated using the final transcript. • It may increase compute usage or cost when a preemptive response is discarded (for example if the user interrupts or the final transcript differs). • It works best when the STT system returns transcripts faster than the end-of-speech detection and when turn detection is enabled. If you want, I can help you decide whether to enable it for your agent and outline trade-offs (latency vs. compute cost) or show the exact spot in your
AgentSession
config to toggle it. Which would you prefer? Sources: Agent speech and audio | LiveKit Documentation | Understand and Improve Agent Latency | LiveKit | Uninterruptable Agent | LiveKit Documentation | How to match the latency of the homepage agent | LiveKit, with interactive elements
b
is it a good fit for realtime model
t
Great question — happy to help weigh the pros and cons. Short answer: • Yes — preemptive_generation can be a good fit for realtime models when your goal is to reduce perceived latency and improve conversational flow, but it comes with trade-offs you should consider. When it’s a good fit • Low-latency transcripts: If your STT returns partial transcripts well before VAD/end-of-turn is detected, preemptive generation can start inference early and make replies feel much faster. • Stable context: If the conversation state, tools, and available context rarely change during the rest of the user’s turn, the preemptive output is unlikely to be discarded. • Realtime UX focus: If minimizing response delay is a high priority for your user experience (e.g., live assistants, interactive kiosks, or customer-facing voice agents), preemptive generation helps maintain a more natural back-and-forth. When to avoid or be cautious • Frequent interruptions/edits: If users often interrupt themselves, correct speech, or the final transcript differs significantly from partials, preemptive responses will be canceled and recomputed — causing extra compute and possible wasted cost. • Variable tool/context changes: If tools or chat context commonly change in
on_user_turn_completed
, preemptive outputs will be invalidated more often. • Cost-sensitive deployments: Because it may run inference on partial transcripts that get discarded, preemptive generation can increase compute usage and cost. Practical recommendations 1. Test with real traffic: Run A/B tests with and without
preemptive_generation=True
to measure perceived latency improvements versus extra compute. 2. Use for short, predictable turn types: Enable for intents where users give short prompts or where transcripts are unlikely to change. 3. Monitor cancellations: Track how often preemptive responses are canceled — high cancellation rates mean wasted work and indicate it’s not a good fit. 4. Combine with better turn detection: Ensure VAD and turn detection are tuned so preemptive starts when partial transcripts are reliable. 5. Cost controls: If possible, set limits on the realtime model size or inference budget for preemptive runs to limit expense. If you tell me about your realtime model setup (STT latency, how often users interrupt, and whether context/tools change mid-turn), I can suggest whether to enable it and recommend specific tuning or monitoring metrics to watch. Which details can you share? , with interactive elements
b
what is ctx.tagger?
t
Thanks — I can help with that. You're asking about `ctx.tagger`; I don’t have a direct definition for
ctx.tagger
from the sources I can access, so I’ll need a bit more context to give an accurate answer. Could you share one of the following so I can be specific and practical: • A short code snippet showing where
ctx.tagger
appears (language and file help). • Which SDK, agent framework, or version you’re using. • The surrounding function or call (for example, inside an Agent handler like
on_user_turn_completed
or in a middleware). • Any error messages or unexpected behavior you’re seeing when using
ctx.tagger
. If you don’t have code handy, tell me what you expect
ctx.tagger
to do (e.g., tag intents, add metadata to transcripts, label tokens). With that I can suggest likely equivalents or alternatives and how to implement them. , with interactive elements
b
is it a JobContext methods?
t
Short answer: No —
ctx.tagger
is not a documented method/property of the JobContext in the materials I can access. What I can confirm: •
ctx.tagger
does not appear in the LiveKit Agents docs or JobContext reference I have. • I can list other JobContext methods or common fields if that would help you map what you expect
tagger
to do. Next steps — to help precisely: • Please paste the small code snippet where
ctx.tagger
is used (the surrounding function or handler and the SDK/version). • Or tell me what you expect
ctx.tagger
to do (e.g., add labels to transcripts, detect intents, enrich messages). With that I can: • Identify a correct JobContext method or alternative approach, or • Show how to implement the tagging behavior (example code) using supported JobContext APIs or middleware. Which do you prefer? , with interactive elements
b
RecordingOptions in session.start is different from egress?
t
Good question — I’ll clarify this and show when to use each. Short answer: • Yes — the
RecordingOptions
you pass to
session.start
are different from Egress. They serve different purposes and produce different outputs. What each one does •
record
in
session.start
(RecordingOptions)
◦ Used for agent observability and debugging during a session. ◦ Captures traces, logs, transcripts, and per-session audio so you can inspect agent behavior (turn detection, latency, model responses). ◦ Data is stored in LiveKit Cloud (viewable in the dashboard) and retained for 30 days. ◦ This is for monitoring and troubleshooting the agent, not for producing archival media files. • Egress (recording/export) ◦ Designed to record or stream room media for external use (archiving, VOD, compliance, live streaming). ◦ Produces media files/streams such as MP4, WebM, HLS, RTMP, or raw track exports (OGG, etc.). ◦ Supports room composite, track composite, and track egress types and can upload directly to S3/GCS or stream to RTMP endpoints. ◦ Available for self-hosted and Cloud setups and intended as the long-term/media export solution. Key differences to keep in mind • Purpose: observability/debugging (session.record) vs. media export/archiving/streaming (Egress). • Output: logs/traces/transcripts/audio for inspection vs. MP4/WebM/HLS/RTMP media files. • Storage/retention: stored in LiveKit Cloud (30 days) vs. exported to your storage or streaming destinations. • Availability:
record
in
session.start
is LiveKit Cloud only; Egress works with self-hosted setups as well. When to use each • Enable
record
in
session.start
when you want to debug agent behavior, analyze transcripts, or collect telemetry for product improvement. • Use Egress when you need to save a meeting/room or participant tracks as files, publish a recording, or stream to external platforms. If you like, I can: • Show the exact
session.start
record
example for your SDK (Python/JS) or • Outline an Egress call (room composite or track egress) for your use case. Which would help you most — a code example for
session.start
recording options or an example egress request? Sources: Why is my Agent insights data missing? | LiveKit | LiveKit Agent Observability | Debug and optimize voice agents | LiveKit | Streamline troubleshooting with Agent Observability | LiveKit | server-sdk-js | livekit/livekit_composite | DeepWiki | Universal Egress | LiveKit, with interactive elements
b
what is livekit-blockguard
t
I don't have the answer you're looking for. You could also try asking your question: • in one of the other Slack channels or • to https://deepwiki.com/livekit/livekit_composite which is trained on all LiveKit source code If you find the answer, please post it here to help others!
b
is there any blockguard feature available on livekit?
hi