What SLNG does
The LLM router sits between Vapi and your model
Fewer model calls per conversation.
Simple turns
Confirmations, greetings, consent speech, hold responses handled locally.
Complex turns
Reasoning, decision-making, ambiguous input go to your model as normal.
The result
Fewer LLM calls. Lower cost. Same output quality.
One change in your agent config
Same voice. Same agent logic. Same plan.
1"custom_llm": {
2 "url": "{region}.llm-router.slng.ai"
3}
Adaptive Execution layer
Keep your pipeline. Add the execution layer
The perfect execution path for every turn.
LLM routing
Per-turn model selection and cost optimization.
PII redaction
Personally identifiable data stripped before it leaves the hub.
TTS smart caching
Repeated TTS responses served from cache. Provider never gets called.
Compliance and security
Getting started
Live instantly. Results within 24hrs
Swap the URL in your agent config. We show you the numbers against your current LLM costs.
1. Get your SLNG key
Sign up at app.slng.ai. Get your API key.
2. Update your Vapi config
Assistant config → Custom LLM → set the endpoint to SLNG + your key
3. See the results
Give it 24 hours. Your dashboard shows LLM cost, latency, and quality vs. baseline.
How does the LLM router reduce cost?
Most turns are simple. The router handles those locally without calling your LLM. Complex turns go to your model as normal. Fewer calls per conversation.
How do I connect SLNG to Vapi?
Assistant config → Custom LLM → set the endpoint to {region}.llm-router.slng.ai + your SLNG key.
Do I need to change my Vapi plan?
No. SLNG is a separate service. No changes to your Vapi setup.
How much does it cost?
US$ 0.0033 per agent minute. No contracts. No minimums. Your voice platform billing is separate.
Is my data safe?
PII redaction built in. ISO 27001 certified. HIPAA compliant. GDPR compliant. SOC 2 Type II in audit.
How does latency improve?
Simple turns skip the LLM round-trip entirely. 39% less turn latency on average.
Can SLNG handle STT and TTS too?
Yes. 30+ models across STT and TTS, running in 11 regions. https://docs.slng.ai/models
Stay in the loop
Unmuted.
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