Origination & termination
| Feature | Yes / How |
|---|---|
| Outbound PSTN dialing | Yes. Originate RPC. E.164 destinations or full SIP URIs. |
| Inbound PSTN handling | Yes. Set the rule per trunk via SetInboundRouting (REJECT / PLAY-AND-HANGUP / NOTIFY-AND-HANGUP / HANDLE-AI). |
| Bulk / predictive dialing | Yes. OriginateBulk reads a CSV, paces calls at the CPS you set, and caps concurrent channels. AbortBulk cancels a campaign mid-flight. |
| Click-to-call | Yes. Originate with default_app=ANSWER and the agent’s softphone as the call_from. |
| Multi-trunk LCR | Yes. Add one trunk per carrier via AddTrunk. The gateway picks the cheapest healthy trunk per destination prefix. |
| Failover / circuit breaker | Yes. The per-trunk circuit breaker trips on consecutive 5xx responses. The state shows in ApiTrunkConfig.is_cb_tripped. |
| Number portability lookups | On request. Availability depends on the carrier integration. |
Call control
| Feature | Yes / How |
|---|---|
| Hangup (any leg) | Terminate RPC. |
| Park | ExecuteDialplan(action=PARK). |
| Music on hold | ExecuteDialplan(action=MUSIC_ON_HOLD, app_args=<url>). |
| Playback prompt | ExecuteDialplan(action=PLAYBACK, app_args=<url>). |
| Unpark | ExecuteDialplan(action=UNPARK_AND_BRIDGE) reattaches a parked call to its bridge partner. |
| Hold / resume | CHANNEL_HOLD / CHANNEL_RESUME events. From the SDK, use ExecuteDialplan(MUSIC_ON_HOLD) then ExecuteDialplan(UNPARK_AND_BRIDGE). |
| Call screening | The inbound rule NOTIFY_AND_HANGUP fires a webhook before the gateway answers. Your app then decides. |
| Barge (AI barge-in) | Barge RPC. The platform’s headline AI-network unblocker. While the AI talks, the gateway watches the inbound leg for the human’s voice (energy / VAD / semantic, set per trunk via auto_bargein_mode). When the human starts to talk, the gateway gates the AI’s outbound audio within barge_in_patience_ms (default 250 ms). The human is then heard immediately. Without barge-in, AI voicebots feel deaf. Trunk knobs: auto_bargein_mode, auto_bargein_aggressiveness. Per-call knobs on OriginateRequest: auto_barge_in, barge_in_patience_ms. |
| Stuck-call cleanup (bucket actions) | GetActiveBuckets / GetBucketCalls / ExecuteBucketAction list the calls that are stuck in a bucket (parked, abandoned, orphaned) and act on them in bulk. The typical action is 0=hangup to clear stuck calls during ops incidents. These RPCs are not a transfer or conferencing primitive. |
| Transfer (blind / attended) | Not supported. This feature is out of scope on this platform. |
| Conference (3+ parties) | Not supported. This feature is out of scope on this platform. |
| Whisper / coach | Not supported. This feature is out of scope on this platform. |
Audio handling
| Feature | Yes / How |
|---|---|
| Codec support | PCMU, PCMA (G.711); PCM16; Opus; G.722. Per-trunk preference list. |
| Transcoding | Automatic on egress (for example, linear16 from the AI → PCMU to the PSTN). A SIMD path inside the C++ core does the work. |
| AEC / AGC / NS | A WebRTC-grade pipeline runs on every WebRTC leg. You can set it per call. |
| VAD-based barge-in | Yes. OriginateRequest.auto_barge_in + barge_in_patience_ms. |
| DTMF (RFC 2833) | Yes. Default. |
| DTMF (SIP INFO) | Yes. The gateway falls back to it when the endpoints do not negotiate RFC 2833. |
| DTMF (in-band) | The gateway detects it. It is not the preferred mode. |
| DTMF masking | For PCI-DSS. The gateway redacts DTMF tones from the recording stream and still passes them to the dialplan. |
| Pre-answer / early media | Pass-through. |
| Comfort noise | The gateway generates it when the far end sends silence. |
| Echo reference | A per-leg AEC reference. The target is ERL > 20 dB. |
AI / agent integration
| Feature | Yes / How |
|---|---|
| AI websocket bridge | OriginateRequest.ai_websocket_url. Audio is bidirectional. Framing follows the AI vendor (OpenAI Realtime, Deepgram, ElevenLabs, etc). |
| AI QUIC bridge | OriginateRequest.ai_quic_url. A lower-latency option for first-party AI services. |
| Inbound AI handoff | SetInboundRouting(rule=HANDLE_AI) + inbound_ai_websocket_url. |
| Agent DAGs | Yes. Multi-step orchestration (TTS → STT → LLM → tool call → branch). Publish DAGs via the admin API. DAGs are versioned. |
| Live transcription | Pipe on_audio_frame to your STT. ClutchCall does not bundle an STT. You pick one. |
| Streaming TTS | Pipe TTS PCM into push_audio. ClutchCall resamples to the trunk codec. |
| Tool / function calling | Your AI drives it. The gateway only moves audio and DTMF. |
| Human-in-the-loop transfer | Yes, mid-call. Pause the AI. Originate a human leg. Bridge the legs. |
Reliability & scale
| Feature | Yes / How |
|---|---|
| Active-active multi-region | The platform supports multi-region deployment. Calls stay pinned to the ingress region. CDRs replicate globally. |
| Per-tenant CPS quotas | Enforced. Excess calls return ERR_RATE_LIMITED. |
| Per-trunk channel caps | AddTrunk.channel_limit. New attempts past the cap fail closed. |
| Circuit-breaker | Per-trunk. It trips on consecutive carrier 5xx responses. |
| Hot certificate reload | ReloadCertificates admin RPC. No connections drop. |
| Zero-downtime upgrades | A single-binary rolling deploy. QUIC connection migration keeps in-flight calls. |
| Rate-limited admin | The gateway throttles admin RPCs separately from call control. |
Compliance & regulation
| Feature | Yes / How |
|---|---|
| STIR/SHAKEN signing | The gateway signs outbound INVITEs with the configured PASSporT cert. You can select attestation A/B/C per trunk. |
| STIR/SHAKEN validation | The gateway checks inbound Identity headers. The result shows in CallEvent.status. |
| P-Asserted-Identity | Set per trunk. |
| PIDF-LO / E911 location | A trunk-default civic address. Override per call via ExecuteDialplan(ANSWER, app_args=<json>). |
| DNC suppression | Upload a list per campaign. The gateway checks it before each Originate. |
| Recording consent prompts | A playback prompt on connect (jurisdiction-dependent). |
| Recording encryption | The gateway writes recordings to your storage encrypted at rest (AES-256). |
| Retention controls | A per-tenant retention window applies to CDRs and recordings. |
| HIPAA | A BAA is available. Recording storage encryption is mandatory. |
| PCI-DSS | DTMF masking + per-stream redaction tags. |
| GDPR / CCPA | For right-to-be-forgotten requests, purge tenant CDRs and recordings older than the retention window. |
| CALEA | The carrier upstream of ClutchCall honours CALEA. It is not a ClutchCall-side feature. |
Observability
| Feature | Yes / How |
|---|---|
| CDRs | The gateway pushes CDRs to ClickHouse. The full schema is in Telemetry. |
| Live event stream | StreamEvents RPC. One CallEvent per state transition. |
| Prometheus metrics | /metrics on every gateway shard. |
| OpenTelemetry traces | OTLP HTTP/gRPC exporter. tenant.id and call.sid are on every span. |
| SIP packet capture | HEPv3 to Homer / heplify. |
| Recording | Per-call. The gateway stores recordings at the trunk-configured URL or in your S3. |
| Audit log | The gateway logs all admin RPCs with the issuing service-account kid. |
WebRTC
This table lists the browser-side and vendor-bridge surface area:| Feature | Yes / How |
|---|---|
| DTLS-SRTP media | Mandatory. The full key exchange uses the standard a=fingerprint SDP attribute. |
| ICE / STUN / TURN | The gateway side is ICE-lite. The platform publishes host and srflx candidates. Clients relay through their own TURN server when needed. |
| Codec negotiation | The gateway offers Opus + PCMU by default. PCMA and G.722 are negotiable. The gateway transcodes to the trunk codec on bridge. |
| Audio processing pipeline | AEC + AGC + NS run on every WebRTC leg, per direction. |
| Browser SDK | TypeScript/WASM. The SDK exposes audio as a standard MediaStreamTrack. |
| LiveKit adapter | It joins as a participant, subscribes to one track, and bridges to the matching call_sid. It authenticates with a JWT. |
| Daily adapter | It uses JSON text-frame signaling and joins as a hidden participant. |
| Chime adapter | It uses AWS SigV4 + a Chime JoinToken. You must create the meeting out-of-band. |
| Twilio Media Streams | PCMU 8 kHz pass-through. The gateway validates the X-Twilio-Signature HMAC. |
| Vapi adapter | Linear16 16 kHz on ingress. The gateway resamples to PCMU on egress. |
| getStats() exposure | Every WebRTC leg’s RTCStats (jitter, loss, ICE candidate type, REMB, NACK rate) shows in the per-leg event stream. |
| simulcast / SVC | N/A. The platform is audio-only. |
| Datachannels | Not exposed. The SDK uses WebTransport for control instead. |
Other transports
| Feature | Yes / How |
|---|---|
| WebTransport | The browser control plane (RPC envelopes). It uses the same QUIC port as native SDKs. |
| QUIC (native SDKs) | Direct binary RPC for Python / Go / Rust / Java / .NET. |
| Generic SIP | Yes. Carrier-agnostic. |
| HTTP/3 fallback | Optional. It is a verification endpoint only, not a media transport. |
Out of scope
The platform deliberately does not implement these capabilities:- Video. The platform is audio-only.
- Fax / T.38. Pass-through only via raw SIP. There is no T.38 stack.
- On-prem PBX replacement. ClutchCall is a gateway/orchestrator. It runs alongside Asterisk / Cisco UCM, not in place of them.
- First-party STT / TTS / LLM. Bring your own. The platform provides the audio pipe and the agent-DAG runner.
- First-party DID procurement. You obtain DIDs from a carrier. You then attach them to a trunk via
AddTrunk. - CRM-side dashboards. The platform emits CDRs and events. Consumers wire them into Salesforce / HubSpot / etc.