Voice Agent Troubleshooting: Complete Diagnostic Checklist

TL;DR: Troubleshoot voice agent failures using this symptom-to-diagnosis approach:

Start at the infrastructure layer. Move up only when that layer is verified working. Most issues (50%+) are in telephony or audio—don't jump to LLM debugging first.

Methodology Note: Diagnostic frameworks and thresholds in this guide are derived from Hamming's analysis of 4M+ production voice agent calls and incident response patterns across 10K+ voice agents (2025-2026).

Related Guides:

• Voice Agent Incident Response Runbook — 4-Stack framework for production outages
• Debug WebRTC Voice Agents — ICE, RTP, and pipeline debugging
• How to Evaluate and Test Voice Agents — 4-Layer QA Framework
• Voice Agent Observability — 4-Layer Observability Framework
• Voice AI Latency Guide — Latency benchmarks and optimization
• Debugging Voice Agents: Logs, Missed Intents & Error Dashboards — Real-time log analysis, error dashboards, and continuous improvement loops

If You're Debugging an AI Voice Agent...

AI voice agents add complexity layers on top of traditional VoIP infrastructure. Before debugging ASR, LLM, or TTS issues, verify your network and telephony stack is healthy. Most AI voice agent problems trace back to underlying VoIP issues.

Bottom line: If your VoIP layer has problems, your AI pipeline will magnify them. A 2% packet loss that's "acceptable" for human calls causes 10-15% ASR word error rate increases for voice agents.

→ Skip to: VoIP Call Quality Checklist if you suspect network issues

Why Do Voice Agents Fail?

Voice agents fail across multiple interdependent layers: telephony, ASR, LLM orchestration, tool execution, and TTS. Single component failures cascade through subsequent decisions, making root cause diagnosis difficult. Systematic troubleshooting requires isolating whether issues stem from audio quality, semantic understanding, model failures, API integrations, or synthesis latency.

What you'll learn:

• How to identify which component (ASR, LLM, tool execution, TTS) causes specific failure patterns
• Diagnostic techniques using logs, traces, and component-level testing to isolate root causes
• Production monitoring strategies to catch issues before they impact users

Quick filter: If you're restarting services before understanding which layer failed, you're wasting time.

What Are the Common Voice Agent Failure Categories?

Voice agents combine STT (speech-to-text), NLU (natural language understanding), decision logic, response generation, and TTS. Each layer depends on previous outputs: ASR errors corrupt LLM inputs, causing downstream tool execution failures.

Failure Category Reference Table

How Do Failures Cascade Across Layers?

Single root-cause ASR errors propagate: incorrect transcription leads to misclassified intent, which triggers wrong tool selection. External service failures cascade when slow CRM responses delay agent replies beyond user tolerance (1-2 seconds).

How Do You Troubleshoot ASR (Speech Recognition) Failures?

ASR Error Types and Patterns

ASR Diagnostic Checklist

• Audio reaching server? Check for audio frames in logs, verify WebRTC connection
• Codec negotiated correctly? Expected: Opus (WebRTC) or PCMU/PCMA (SIP)
• ASR returning transcripts? Empty transcripts = no audio or VAD issue
• Confidence scores acceptable? Target >0.85, investigate <0.7
• WER within threshold? Target <5% clean audio, <10% with noise
• Provider status? Check Deepgram, AssemblyAI, Google STT status pages

ASR-Specific Fixes

• Incorporate diverse training data: accented audio, noisy environments, varied speech patterns from real production calls
• Implement noise-canceling technologies: beamforming microphones, suppression algorithms, acoustic models trained on real-world audio
• Apply LLM-guided refinement to ASR output: use language models to correct transcription errors using conversational context
• Deploy hardware-accelerated VAD (voice activity detection) to filter background noise before ASR processing

For detailed ASR failure patterns, see Seven Voice Agent ASR Failure Modes in Production.

How Do You Debug LLM and Intent Recognition Failures?

LLM Failure Mode Reference

LLM Diagnostic Checklist

• LLM endpoint responding? Direct API test, check provider status
• Rate limiting? Look for 429 errors, check tokens per minute
• Prompt changes? Review recent deployments, check for injection
• Context window? Calculate tokens per conversation, approaching limit?
• Tool calls working? Check function call logs, tool timeout errors
• Response quality? Compare to baseline, check for hallucinations

Mitigation Strategies

• Ground with verified data: integrate agents with reliable, up-to-date databases (CRM, knowledge bases, APIs)
• Implement prompt engineering: design prompts that constrain model outputs to factual, verified responses
• Set appropriate model configurations: lower temperature (0.3-0.5) for factual tasks, restrict token generation length
• Add validation checkpoints: verify critical information before executing irreversible actions

How Do You Fix Tool Execution and API Integration Failures?

Tool Call Failure Patterns

Tool Integration Diagnostic Steps

• Navigate to API Logs to monitor all requests/responses, check authentication errors, verify request payload structure
• Check webhook logs to verify deliveries, server response codes, timing, monitor event delivery failures
• Track tool execution results and errors through trace views showing input parameters and returned data
• Test tool integrations independently before end-to-end testing: verify API calls work outside agent context
• Measure API response latency to identify slow external services creating conversation pauses

Tool Execution Fixes

• Implement fallback logic for when external services fail or respond slowly: retry with exponential backoff
• Cache frequently used data to avoid unnecessary database lookups mid-conversation
• Set timeout thresholds for external API calls (500-1000ms) to prevent indefinite waiting
• Build circuit breakers to prevent small failures from cascading into system-wide problems

How Do You Optimize TTS Latency and Quality?

TTS Performance Benchmarks

TTS Diagnostic Methods

• Measure total latency including time-to-first-byte (TTFB) and complete audio synthesis duration
• Track component-level breakdowns to isolate delays between STT, LLM inference, and TTS generation
• Monitor tail latencies (p99) as users remember worst experiences, not average performance
• Log synthesis quality metrics: audio artifacts, volume consistency, unnatural pauses in generated speech

Optimizing TTS Performance

• Use dual streaming TTS: accepts text incrementally (token by token), begins speaking while LLM generates remaining response
• Pre-connect and reuse SpeechSynthesizer to avoid connection latency on each request
• Implement text streaming via websocket v2 endpoints for real-time synthesis as text arrives
• Chunk long outputs at punctuation marks, stream incrementally to accelerate multi-sentence replies

For detailed latency optimization, see Voice AI Latency: What's Fast, What's Slow, and How to Fix It.

Why Are Customers Hanging Up on My Voice Bot?

Audio Quality Degradation Patterns

Call Drop Root Causes

• Insufficient internet speed for VoIP bandwidth requirements (minimum 100 kbps per call)
• Network overload when multiple applications compete for bandwidth during voice calls
• Weak or disrupted Wi-Fi signals cause packet loss, forcing call termination
• Application conflicts when other apps request microphone access, breaking audio connection

Audio Quality Fixes

• Upgrade internet connection to meet VoIP requirements: minimum 100 kbps upload/download per concurrent call
• Use wired Ethernet connections for critical calls instead of Wi-Fi to reduce packet loss
• Optimize Quality of Service (QoS) settings to prioritize voice traffic over other network activity
• Implement jitter buffers to smooth packet arrival timing and reduce audio stuttering

VoIP Call Quality (Jitter/Packet Loss/MOS) Checklist

This section covers traditional VoIP diagnostics that directly impact AI voice agent performance. Fix these first before debugging ASR/LLM/TTS.

Network Quality Metrics Reference

VoIP Diagnostic Checklist

Network & Bandwidth:

• Sufficient bandwidth? Minimum 100 kbps per concurrent call (G.711), 30 kbps (Opus)
• QoS configured? Voice traffic prioritized (DSCP 46/EF marking)
• Packet loss under threshold? Use ping -c 100 or VoIP quality tools
• Jitter acceptable? Check with iperf3 or RTP stream analysis
• No bandwidth contention? Other applications competing during calls

NAT & Firewall:

• SIP ALG disabled? Router SIP ALG causes registration failures, one-way audio
• UDP ports open? SIP: 5060/5061, RTP: 10000-20000 (varies by provider)
• STUN/TURN configured? Required for WebRTC NAT traversal
• Symmetric NAT handled? May require TURN relay server
• Firewall allowing RTP? Stateful inspection may block return packets

SIP & Signaling:

• SIP registration successful? Check for 401/403/408 errors
• Correct SIP trunk credentials? Authentication failures = no calls
• DNS SRV records resolving? SIP often uses SRV lookups
• TLS/SRTP configured? Encryption may be required by provider
• SIP timers appropriate? Session timers, registration refresh

Codec & Audio:

• Codec negotiated correctly? Check SDP in SIP INVITE/200 OK
• Codec priority set? Opus > G.722 > G.711 (for quality)
• Sample rate matched? Mismatch causes audio distortion
• Echo cancellation enabled? AEC required for full-duplex
• Comfort noise configured? Prevents "dead air" during silence

Common VoIP Issues and Fixes

WebRTC-Specific Diagnostics

For browser-based voice agents using WebRTC:

chrome://webrtc-internals (Chrome)
about:webrtc (Firefox)

Key metrics to check:

• ICE connection state: Should be "connected" or "completed"
• DTLS state: Should be "connected"
• Packets lost: Incoming/outgoing RTP packet loss
• Jitter buffer: Current delay and target delay
• Audio level: Verify audio is flowing (not 0)

RTP Stream Analysis

For deep packet inspection when standard tools don't reveal issues:

Capture RTP traffic:

tcpdump -i any -w voip_capture.pcap udp portrange 10000-20000

Analyze in Wireshark:

1. Navigate to: Telephony → RTP → RTP Streams
2. Check for packet loss percentage, jitter, delta (inter-packet timing)
3. Look for sequence number gaps indicating lost packets

Key RTP metrics:

MOS Score Interpretation

Mean Opinion Score (MOS) predicts perceived call quality:

For AI voice agents: Target MOS >4.0. Below 3.5, ASR accuracy drops significantly.

What Logging and Tracing Do You Need for Voice Agent Debugging?

Essential Logging Schema

Turn-level data (per exchange):

{
  "call_id": "call_abc123",
  "turn_index": 3,
  "timestamp": "2026-01-26",
  "user_transcript": "I need to reschedule my appointment",
  "asr_confidence": 0.94,
  "intent": {"name": "reschedule_appointment", "confidence": 0.91},
  "latency_ms": {"stt": 180, "llm": 420, "tts": 150, "total": 750},
  "tool_calls": [{"name": "get_appointments", "success": true, "latency_ms": 85}],
  "agent_response": "I can help you reschedule..."
}

Production Monitoring Essentials

Tracing Voice Agent Workflows

Tracing captures every call step: audio input, ASR output, semantic interpretation, internal prompts, model generations, tool calls, TTS output. Use OpenTelemetry for metrics, logs, traces to keep data portable across observability tools.

For detailed observability implementation, see Voice Agent Observability: The Missing Discipline.

How Do You Fix Conversation Flow and Turn-Taking Issues?

Context Loss and Memory Issues

Agents hit context window limits (4k-32k tokens), causing "forgetting" of important earlier conversation details. As conversations grow, critical information gets pushed out, leading to contradictions or lost problem tracking.

How Do You Prevent Agents from Interrupting Users?

• Implement dynamic silence thresholds: 300ms for quick exchanges, 800ms for slower speakers
• Use hardware-accelerated Voice Activity Detection (VAD) that handles interruptions gracefully
• Move beyond Voice Activity Detection to consider semantics, context, tone, conversational cues
• Tune VAD sensitivity based on use case: customer service needs longer thresholds than quick commands

Fixing Conversation Flow Issues

• Use hybrid context management: full server-side history for high-stakes sessions, lightweight vector summaries for general chat
• Implement explicit context anchoring: have users restate critical constraints every 3-4 turns
• Test conversation state management: verify handling of interruptions, corrections, topic changes
• Implement conversation summarization at regular intervals to maintain context within token limits

How Do You Build Error Handling and Recovery Patterns?

Resilience Design Patterns

User-Facing Error Recovery

• Provide clear, actionable feedback: "I'm having trouble accessing our product database. Let me try a different approach" instead of "Error 500"
• Build fallback logic into customer journeys: "Press 0 to speak to a live representative" when agent reaches capability limits
• Acknowledge errors transparently: "I missed that, could you repeat?" rather than guessing at misheard inputs

Continuous Improvement from Failures

• Feed production failures back into offline evaluation datasets to create continuous improvement loops
• Convert any live conversation into replayable test case with caller audio, ASR text, expected intent
• When production call fails, convert to regression test with one click, preserving original audio and timing
• Track failure resolution rates: measure time from issue identification to deployed fix

What Testing and Evaluation Strategies Work for Voice Agents?

Automated Testing Approaches

• Auto-generate test cases from agent prompts and documentation to ensure coverage
• Run 1000+ concurrent calls with real-world conditions: accents, background noise, interruptions, edge cases
• Test agents in multiple languages, simulate global accents and real-world noise environments
• Implement synthetic user simulation: generate varied conversation paths to stress-test agent logic

Evaluation Metrics That Matter

CI/CD Integration for Voice Agents

• Integrate testing into GitHub Actions, Jenkins, or CI/CD pipeline to trigger tests and block bad prompts automatically
• After each build, send predefined prompts to agent; if more than 5% responses differ from baseline, deployment halts
• Version control agent configurations (prompts, tools, models) alongside code for reproducible deployments

For comprehensive testing methodology, see How to Evaluate and Test Voice Agents.

Summary and Next Steps

Systematic troubleshooting requires component-level isolation: test ASR, LLM, tool execution, TTS independently before end-to-end diagnosis. Production monitoring with comprehensive logging, tracing, and observability catches issues before they impact users.

Next steps:

• Implement structured logging capturing every component's inputs, outputs, latency, confidence scores
• Set up production monitoring with alerts for latency spikes, error rate increases, quality degradation
• Build automated testing pipelines that run diverse scenarios before deployment to catch failures early

How Hamming Helps with Voice Agent Troubleshooting

Hamming provides the observability and testing layer that makes troubleshooting faster:

• 4-Layer Visibility: Unified dashboards showing health across Telephony, Audio, Intelligence, and Output
• Instant Root Cause: One-click from alert to transcript, audio, and model logs
• Session Replay: Full audio playback with transcripts and component traces
• Regression Detection: Automated alerts when metrics deviate from baseline
• Scenario Generation: Auto-generate test cases from prompts, execute in <10 minutes

Instead of manually debugging across multiple dashboards, get automated visibility into every layer of your voice agent stack.

Debug your voice agents with Hamming →

Related Guides:

• Voice Agent Drop-Off Analysis — Funnel analysis and abandonment metrics with remediation playbook
• Slack Alerts for Voice Agents — Alert templates for latency, ASR drift, jitter, and prompt regressions
• Voice Agent Monitoring KPIs — 10 production metrics with formulas and benchmarks
• Voice Agent Incident Response Runbook — Systematic debugging framework for production outages
• Voice Agent Monitoring Platform Guide — 4-Layer monitoring architecture
• Debugging Voice Agents: Logs, Missed Intents & Error Dashboards — Real-time log analysis, error dashboards, and continuous improvement loops
• Voice Agent SEV Playbook & Postmortem Template — Severity classification, response checklists, and postmortem framework for voice AI incidents