{ "data": { "a": { "slug": "amazon-nova-sonic", "name": "Amazon Nova 2 Sonic", "vendor": "Amazon Web Services", "vendorUrl": "https://aws.amazon.com/ai/generative-ai/nova/speech/", "kind": "http-api", "category": "voice-agents", "summary": "Amazon Nova 2 Sonic is AWS's speech-to-speech model for voice agents on Amazon Bedrock. Clients stream audio and text events both ways over the `InvokeModelWithBidirectionalStream` API, with turn-taking, interruptions, asynchronous tool calls and multilingual voices.", "url": "https://www.anchorterminal.com/tools/amazon-nova-sonic", "markdownUrl": "https://www.anchorterminal.com/tools/amazon-nova-sonic.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/amazon-nova-sonic.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/amazon-nova-sonic.json", "dns": "amazon-nova-sonic.grade.anchorterminal.com", "repo": "https://github.com/aws-samples/amazon-nova-samples", "transports": [ "http" ], "packages": [ { "registry": "pypi", "name": "aws-sdk-bedrock-runtime" }, { "registry": "npm", "name": "@aws-sdk/client-bedrock-runtime" } ], "auth": "api-key", "authNotes": "AWS Signature Version 4 with IAM credentials or a role, scoped per model ARN by IAM policy. The Sonic quickstart signs with environment credentials. Whether Bedrock API keys work on the bidirectional stream wasn't confirmed. Access is self-serve once a person has an AWS account.", "pricing": "usage", "pricingNotes": "Billed per speech and text token on Bedrock on demand. The Nova and Bedrock pricing pages draw their price tables by script, so the figures weren't read on 6 November 2026. No model-specific free tier; new AWS accounts get up to $200 in Free Tier credits.", "priceSummary": "Pay per use", "where": "local", "x402": { "level": "no", "evidence": "No x402, MPP or L402 in the Nova or Bedrock docs (checked 2026-11-06). Billing runs through the AWS account.", "endpoints": [] }, "toolCount": 0, "popularity": { "githubStars": null, "npmWeekly": null, "pypiWeekly": null, "asOf": "2026-11-06" }, "docsUrl": "https://docs.aws.amazon.com/nova/latest/nova2-userguide/using-conversational-speech.html", "llmsTxt": "https://docs.aws.amazon.com/nova/latest/nova2-userguide/llms.txt", "capabilities": [ "voice.agent", "voice.speech-to-speech", "voice.tools", "voice.telephony" ], "tags": [ "official", "hosted", "usage-priced", "closed-source", "python", "typescript", "llms-txt", "streaming", "enterprise" ], "lastRelease": "2026-05-28", "graded": true, "anchor": { "graded": true, "score": 67.6, "grade": "B", "agentReady": false, "rank": 314, "ranked": true, "rankOf": 1486, "categoryRank": 6, "methodology": "0.7", "run": "2026-10-01", "scores": { "ergonomics": 64, "maintenance": 50, "payments": 10, "reliability": 95, "schema": 75, "security": 77, "transparency": 79 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "low", "date": "2026-11-06" }, "negative": 0, "verdict": "Nova 2 Sonic runs speech-to-speech conversations with asynchronous tools on Bedrock, with IAM scoping, no default storage of inputs and a 99.9 per cent SLA. Sessions cut off at 8 minutes, the Python SDK is pre-alpha, and the event payloads have no schema file. Prices are in a script-drawn table we couldn't read.", "bestFor": "Voice agents on AWS, call centres on Amazon Connect, teams that want IAM and in-account data handling.", "strengths": [ "No Bedrock event on the AWS Health history in the 90 days from 8 August 2026", "IAM scoping per model ARN with SigV4 and temporary credentials", "Bedrock stores no inputs or outputs by default, and Sonic isn't on the list of models kept for abuse review", "Asynchronous tool calls let the model keep speaking while a tool runs", "Telephony guides for Twilio, Vonage and Amazon Connect" ], "weaknesses": [ "Connections end after 8 minutes, so long calls need the session-continuation pattern", "The Python SDK for bidirectional streaming is pre-alpha and needs Python 3.12", "Sonic's event payloads are documented as examples, with no schema file", "20 concurrent sessions per Region, not adjustable through Service Quotas", "The March and May 2026 refreshes changed the model in place under the same ID" ], "agentNotes": [ "Plan a reconnect before 8 minutes and replay chat history (up to 200 KB) at the start of the new session", "Send session, prompt and content start events in order before any audio", "Make tool calls safe to repeat, since a reconnect can replay them", "Back off on `ThrottlingException` and stay within 20 concurrent sessions per Region", "Use the polyglot voices TIFFANY or MATTHEW when callers may switch language" ], "metrics": { "kind": "remote", "measured": false }, "reviewCount": 0, "avgRating": 0, "history": [ { "basis": "public evidence", "confidence": "low", "grade": "B", "methodology": "0.7", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 67.6 } ], "editorialScores": { "ergonomics": 64, "maintenance": 50, "payments": 10, "reliability": 95, "schema": 75, "security": 77, "transparency": 64 }, "provenanceScore": 94, "checked": { "categories": { "ergonomics": "2026-11-06", "maintenance": "2026-11-06", "payments": "2026-11-06", "reliability": "2026-11-06", "schema": "2026-11-06", "security": "2026-11-06", "transparency": "2026-11-06" }, "last": "2026-11-06", "oldest": "2026-11-06", "stale": false, "staleAfterDays": 90 } }, "connect": { "install": "pip install aws-sdk-bedrock-runtime" }, "letme": { "capability": "https://letme.dev/voice.agent", "tool": "https://letme.dev/amazon-nova-sonic" }, "sameCompany": [ "amazon-bedrock", "amazon-nova-embeddings", "amazon-bedrock-guardrails", "amazon-transcribe", "amazon-polly", "agentcore-memory", "agentcore-identity", "aws-secrets-manager", "agentcore-web-search", "aws-mcp-servers", "amazon-ses", "amazon-location", "amazon-translate", "amazon-ads-api", "amazon-creators-api" ], "area": "voice", "provenance": { "legalEntity": "Amazon Web Services, Inc.", "domain": "amazon.com", "domainRegistered": "1994-11-01", "domainNote": "The endpoint is on amazonaws.com, an AWS domain registered on 2005-08-18. The security.txt on aws.amazon.com expires on 2027-10-16.", "endpointOnVendorDomain": true, "terms": "https://aws.amazon.com/service-terms/", "privacy": "https://aws.amazon.com/privacy/", "statusPage": "https://health.aws.amazon.com/health/status", "changelog": "https://docs.aws.amazon.com/nova/latest/nova2-userguide/release-notes.html", "securityTxt": "valid", "checked": "2026-11-06", "notes": [ "The AWS Service Terms were last updated on 30 October 2026. Section 50.12 covers Amazon Bedrock, and Bedrock is not among the services section 50.3 lists for use of content to improve AWS services.", "RDAP gives 1994-11-01 for amazon.com and 2005-08-18 for amazonaws.com.", "aws.amazon.com/.well-known/security.txt has Contact, Policy and Encryption fields. Its Expires value is 2027-10-16T16:25:03Z, re-read on 2026-11-01.", "docs.aws.amazon.com/robots.txt allows the Nova and Bedrock pages read. The Nova and Bedrock pricing pages draw their tables by script, so Nova 2 Sonic's prices weren't read." ], "score": 94 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/amazon-nova-sonic.json", "live": { "slug": "amazon-nova-sonic", "versions": [ { "registry": "npm", "name": "@aws-sdk/client-bedrock-runtime", "version": "3.1164.0", "seenAt": "2026-11-06T23:05:35.366071006Z" }, { "registry": "pypi", "name": "aws-sdk-bedrock-runtime", "version": "0.12.0", "released": "2026-10-08", "seenAt": "2026-11-06T23:05:33.518358123Z" } ], "githubStars": 456, "npmWeekly": 21825916, "pypiWeekly": 112826, "securityTxt": { "url": "https://amazon.com/.well-known/security.txt", "state": "valid", "checkedAt": "2026-11-07T16:00:18.354437696Z" }, "llmsTxt": { "url": "https://docs.aws.amazon.com/nova/latest/nova2-userguide/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-11-07T15:31:25.828159373Z" }, "pages": [ { "url": "https://docs.aws.amazon.com/nova/latest/nova2-userguide/release-notes.html", "kind": "changelog", "status": 200, "checkedAt": "2026-11-07T14:05:20.262718007Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "48cb3eb6c070" } ], "updatedAt": "2026-11-07T16:00:18.354437696Z" } }, "answer": "Amazon Nova 2 Sonic scores 67.6 (B) on agent readiness against Ultravox Realtime API's 59.2 (C), and leads in 3 of 7 scored categories. Ultravox Realtime API leads on schema \u0026 documentation, agent ergonomics and payments \u0026 pricing.", "b": { "slug": "ultravox", "name": "Ultravox Realtime API", "vendor": "Ultravox (Fixie.ai)", "vendorUrl": "https://www.ultravox.ai", "kind": "http-api", "category": "voice-agents", "summary": "Hosted voice agents on Ultravox, an open-weight model that takes speech directly with no speech-to-text step and answers through a TTS voice.", "url": "https://www.anchorterminal.com/tools/ultravox", "markdownUrl": "https://www.anchorterminal.com/tools/ultravox.md", "slimMarkdownUrl": "https://www.anchorterminal.com/tools/ultravox.min.md", "jsonUrl": "https://www.anchorterminal.com/api/v1/tools/ultravox.json", "dns": "ultravox.grade.anchorterminal.com", "repo": "https://github.com/fixie-ai/ultravox", "license": "MIT (model code)", "transports": [ "http" ], "remoteUrl": "https://api.ultravox.ai/api", "packages": [ { "registry": "npm", "name": "ultravox-client" }, { "registry": "pypi", "name": "ultravox-client" } ], "auth": "api-key", "authNotes": "`X-API-Key` header on the REST API. Clients join a call with the `joinUrl` returned when it's created, so the key stays on your server.", "pricing": "usage", "pricingNotes": "Pay as you go at $0.05 a minute after 30 free minutes, capped at 5 concurrent calls. Pro is $100 a month (annual rate) at the same $0.05 a minute with no hard concurrency cap, the outbound scheduler, 5 custom voices and 20 RAG corpora. SIP costs 0.5 cents a minute (0.48 on Pro). Threads are $2 per 1M input tokens and $15 per 1M output. Enterprise is custom. Telephony from Twilio or other carriers is billed by them (https://www.ultravox.ai/pricing).", "priceSummary": "$100 / mo", "where": "hosted", "x402": { "level": "no", "evidence": "No x402 support in the docs, pricing page or MCP docs (checked 2026-09-30).", "endpoints": [] }, "toolCount": null, "popularity": { "githubStars": 4574, "npmWeekly": 17262, "pypiWeekly": null, "asOf": "2026-09-30" }, "docsUrl": "https://docs.ultravox.ai", "llmsTxt": "https://docs.ultravox.ai/llms.txt", "openapi": "https://api.ultravox.ai/api/schema/", "capabilities": [ "voice.agent", "voice.speech-to-speech", "voice.tools", "voice.telephony" ], "tags": [ "hosted", "open-weights", "no-card", "llms-txt", "openapi", "typescript", "python", "webhooks", "streaming", "speech-to-speech" ], "lastRelease": "2026-07-18", "graded": true, "anchor": { "graded": true, "score": 59.2, "grade": "C", "agentReady": false, "rank": 712, "ranked": true, "rankOf": 1486, "categoryRank": 14, "methodology": "0.7", "run": "2026-10-01", "scores": { "ergonomics": 69, "maintenance": 53, "payments": 40, "reliability": 52, "schema": 84, "security": 46, "transparency": 71 }, "pending": [ "performance", "tasks" ], "assessment": { "confidence": "medium", "date": "2026-11-04" }, "negative": 0, "verdict": "Flat $0.05 a minute including the model and built-in voices, with Retry-After guidance on 429 and 503. Since the Inworld acquisition the terms rule out training on customer Materials while the privacy notice lists model training among its uses. No MCP server, and the status page refuses automated readers.", "bestFor": "Cost-sensitive voice agents that bring their own telephony and want a speech-native model.", "strengths": [ "Flat $0.05 a minute including model and built-in voices", "Speech-native model with no separate STT stage, v0.7 weights public under MIT", "429 and 503 responses with Retry-After and backoff guidance", "Deprecation guide with a minimum 30-day window and dated entries, the newest on 3 November 2026", "API keys can be created, given an expiry and revoked through the API" ], "weaknesses": [ "No MCP server", "Inworld's privacy notice lists training its AI models among the uses of collected content, while the terms say customer Materials aren't used for training", "News page and Python client last updated in December 2025, and no client release since July 2026", "Plain API keys with no scopes", "No subprocessor list, security.txt or readable certification" ], "agentNotes": [ "Honour `Retry-After` on 429 and 503 when creating calls", "Pin the model string (`ultravox-v0.7` or `ultravox-v0.6`) rather than relying on the default", "Hand clients the `joinUrl`, never the API key", "When continuing a call with `priorCallId`, send the full call configuration in the body; fields stop being inherited by 7 December 2026", "Delete calls through the API when you need data removed, there's no retention setting" ], "metrics": { "kind": "remote", "measured": false }, "reviewCount": 2, "avgRating": 3, "history": [ { "basis": "public evidence", "confidence": "medium", "grade": "C", "methodology": "0.7", "pending": [ "performance", "tasks" ], "run": "2026-10-01", "runLabel": "October 2026 research run", "score": 59.2 } ], "editorialScores": { "ergonomics": 69, "maintenance": 53, "payments": 40, "reliability": 52, "schema": 84, "security": 46, "transparency": 62 }, "provenanceScore": 80, "checked": { "categories": { "ergonomics": "2026-11-04", "maintenance": "2026-11-04", "payments": "2026-11-04", "reliability": "2026-11-04", "schema": "2026-11-04", "security": "2026-11-04", "transparency": "2026-11-04" }, "last": "2026-11-04", "lastMoved": "2026-11-04", "oldest": "2026-11-04", "stale": false, "staleAfterDays": 90 } }, "connect": { "http": "curl -X POST https://api.ultravox.ai/api/calls -H \"X-API-Key: $ULTRAVOX_API_KEY\" \\\n -H \"content-type: application/json\" \\\n -d '{\"systemPrompt\":\"You are a friendly receptionist.\",\"voice\":\"Mark\"}'" }, "letme": { "capability": "https://letme.dev/voice.agent", "tool": "https://letme.dev/ultravox" }, "sameCompany": [ "ultravox-voice-cloning" ], "area": "voice", "unitPrices": [ { "item": "Ultravox Realtime", "unit": "call-minute", "usd": 0.05, "note": "model and built-in voices, telephony carrier costs extra" }, { "item": "SIP", "unit": "call-minute", "usd": 0.005, "note": "0.0048 on Pro" }, { "item": "Pro plan", "unit": "month", "usd": 100, "note": "annual rate" } ], "provenance": { "legalEntity": "Theai, Inc. dba Inworld AI", "domain": "ultravox.ai", "domainRegistered": "2023-10-05", "endpointOnVendorDomain": true, "terms": "https://www.ultravox.ai/terms", "privacy": "https://www.ultravox.ai/privacy", "statusPage": "https://status.ultravox.ai", "changelog": "https://docs.ultravox.ai/changelog/news", "securityTxt": "none", "checked": "2026-11-04", "notes": [ "The terms of service at www.ultravox.ai/terms are Inworld AI's, effective 1 October 2026, and name Theai, Inc. dba Inworld AI; the earlier terms, which named Fixie.ai Inc., are at ultravox.ai/terms-old. A site banner says Ultravox has been acquired by Inworld.", "The privacy notice at www.ultravox.ai/privacy is the Inworld AI Privacy Notice, effective 1 October 2026.", "status.ultravox.ai's robots.txt disallows every path for every agent, re-read on 2026-11-04.", "www.ultravox.ai/.well-known/security.txt answers 404. inworld.ai's robots.txt carries `Content-Signal: ai-train=no, search=yes, ai-input=no`." ], "score": 80 }, "pageJsonUrl": "https://www.anchorterminal.com/tools/ultravox.json", "live": { "slug": "ultravox", "probe": { "target": "https://api.ultravox.ai/api", "method": "get", "lastAt": "2026-11-07T18:21:02.434234189Z", "lastOk": true, "lastStatus": 404, "lastMs": 201, "authRequired": false, "uptime24h": 100, "uptime30d": 100, "p50ms24h": 142, "p95ms24h": 238, "samples24h": 239, "samples30d": 7910, "days": [ { "date": "2026-10-07", "probes": 272, "ok": 272 }, { "date": "2026-10-08", "probes": 268, "ok": 268 }, { "date": "2026-10-09", "probes": 250, "ok": 250 }, { "date": "2026-10-10", "probes": 247, "ok": 247 }, { "date": "2026-10-11", "probes": 247, "ok": 247 }, { "date": "2026-10-12", "probes": 247, "ok": 247 }, { "date": "2026-10-13", "probes": 248, "ok": 248 }, { "date": "2026-10-14", "probes": 249, "ok": 249 }, { "date": "2026-10-15", "probes": 253, "ok": 253 }, { "date": "2026-10-16", "probes": 252, "ok": 252 }, { "date": "2026-10-17", "probes": 253, "ok": 253 }, { "date": "2026-10-18", "probes": 256, "ok": 256 }, { "date": "2026-10-19", "probes": 255, "ok": 255 }, { "date": "2026-10-20", "probes": 252, "ok": 252 }, { "date": "2026-10-21", "probes": 253, "ok": 253 }, { "date": "2026-10-22", "probes": 253, "ok": 253 }, { "date": "2026-10-23", "probes": 248, "ok": 248 }, { "date": "2026-10-24", "probes": 251, "ok": 251 }, { "date": "2026-10-25", "probes": 250, "ok": 250 }, { "date": "2026-10-26", "probes": 252, "ok": 252 }, { "date": "2026-10-27", "probes": 249, "ok": 249 }, { "date": "2026-10-28", "probes": 250, "ok": 250 }, { "date": "2026-10-29", "probes": 249, "ok": 249 }, { "date": "2026-10-30", "probes": 249, "ok": 249 }, { "date": "2026-10-31", "probes": 251, "ok": 251 }, { "date": "2026-11-01", "probes": 249, "ok": 249 }, { "date": "2026-11-02", "probes": 250, "ok": 250 }, { "date": "2026-11-03", "probes": 248, "ok": 248 }, { "date": "2026-11-04", "probes": 246, "ok": 246 }, { "date": "2026-11-05", "probes": 185, "ok": 185 }, { "date": "2026-11-06", "probes": 241, "ok": 241 }, { "date": "2026-11-07", "probes": 187, "ok": 187 } ] }, "vendorStatus": { "page": "https://status.ultravox.ai", "indicator": "unknown", "summary": "no machine-readable status found", "checkedAt": "2026-11-06T23:09:07.754460187Z" }, "versions": [ { "registry": "github", "name": "fixie-ai/ultravox", "version": "v0.6", "released": "2025-08-18", "seenAt": "2026-11-07T00:13:46.410504435Z" }, { "registry": "npm", "name": "ultravox-client", "version": "0.6.0", "seenAt": "2026-11-07T00:13:44.335543797Z" }, { "registry": "pypi", "name": "ultravox-client", "version": "0.1.0", "released": "2025-12-10", "seenAt": "2026-11-07T00:13:45.134579448Z" } ], "githubStars": 4585, "npmWeekly": 16984, "pypiWeekly": 174, "securityTxt": { "url": "https://ultravox.ai/.well-known/security.txt", "state": "none", "checkedAt": "2026-11-07T16:00:53.508581161Z" }, "llmsTxt": { "url": "https://docs.ultravox.ai/llms.txt", "ok": true, "status": 200, "checkedAt": "2026-11-07T15:34:15.052985662Z" }, "domain": { "domain": "ultravox.ai", "registered": "2023-10-05", "source": "https://rdap.identitydigital.services/rdap/domain/ultravox.ai", "checkedAt": "2026-11-01T14:12:30.702624774Z" }, "pages": [ { "url": "https://docs.ultravox.ai/changelog/deprecation", "kind": "deprecations", "status": 200, "checkedAt": "2026-11-07T14:08:28.239062701Z", "changedAt": "0001-01-01T00:00:00Z", "fingerprint": "5d02e17c1eba" } ], "github": { "repo": "fixie-ai/ultravox", "checkedAt": "2026-11-02T08:48:52.314300024Z", "stars": 4583, "archived": false, "issuesEnabled": true, "pushedAt": "2025-12-12T18:09:40Z", "openIssues": 53, "openPRs": 9, "issuesOpened90d": 0, "issuesClosed90d": 1, "prsMerged90d": 0, "ci": { "branch": "main", "runs": 1, "success": 1, "failure": 0, "other": 0, "latest": "success", "latestAt": "2025-12-12T18:14:55Z" }, "replies": { "sampled": 25, "unanswered": 17, "medianDays": 25 } }, "updatedAt": "2026-11-07T18:21:02.434234189Z" } }, "edges": [ { "by": 43, "category": "reliability", "leads": "amazon-nova-sonic", "name": "Reliability", "reasons": { "a": "Hosted reading. AWS Health Dashboard with per-service, per-Region history (20). The dashboard history file (newest event 30 October 2026) lists no Bedrock event in the 90 days from 8 August, and the 3 September us-west-2 event names STS, Connect and IAM Identity Center, not Bedrock. The public dashboard records broad events only, so 25 of 30, as amazon-nova-embeddings was read. Quotas published, 20 concurrent requests per Region, not adjustable (15). The stream API lists `ThrottlingException` (429), `ServiceUnavailableException` (503), `ModelTimeoutException` (408) and `ModelStreamErrorException` (424), Bedrock's troubleshooting guide advises backoff with jitter, and the 8-minute connection limit comes with a session-continuation sample (15). Bedrock's SLA of 99.9 per cent a month per Region for model APIs, as read for amazon-nova-embeddings on 1 November (10). Generally available since 2 December 2025 (10). 20 + 25 + 15 + 15 + 10 + 10 = 95.", "b": "A status page sits at status.ultravox.ai, but its robots.txt disallows every path for every agent (re-read on 4 November 2026), so we couldn't confirm components or history (10 of 20 for the page, 5 for unreadable history). Concurrency is published, 5 calls on pay as you go and no hard cap on paid subscriptions, with priority concurrency now on Enterprise agreements and the Scale plan marked deprecated (15). Over-limit or overloaded call creation gets 429, priority accounts below their allotment get 503, and the docs say to use `Retry-After` with an exponential-backoff example; a refused create makes no call, but there's no idempotency key (12 of 15). No SLA found; Enterprise lists a response SLA only (0). The Realtime API is generally available (10). 10 + 5 + 15 + 12 + 0 + 10 = 52." }, "scores": { "a": 95, "b": 52 } }, { "by": 31, "category": "security", "leads": "amazon-nova-sonic", "name": "Security \u0026 auth", "reasons": { "a": "SigV4 with IAM roles and temporary credentials scoped per model ARN, as the Sonic quickstart signs (30). Tools run in the client, so side effects are the developer's to approve, and IAM can restrict which models a role invokes, with no approval step in the API (12 of 20). The model listens to callers and acts on tool results, and no prompt-injection guidance was found in the Sonic guide (5 of 15). CloudTrail logs Bedrock API calls, read as amazon-nova-embeddings was (12 of 15). VDP on HackerOne, Bedrock in SOC scope and a valid security.txt on aws.amazon.com, with no paid bounty, as on the other AWS listings (18 of 20). Total 77.", "b": "Plain API keys in the `X-API-Key` header, which the OpenAPI document shows can be created, given an expiry, revoked and deleted through `/api/api_keys`, with no scopes; each call returns a `joinUrl` so clients never see the key (20). We found no scoped or read-only keys (8 of 20). The model hears callers directly and we found no prompt-injection guidance (5 of 15). Call records and a delete-call API, but no audit log (8 of 15). No security.txt (www.ultravox.ai answers 404). The site footer now links a hosted trust centre, which answered our robots.txt request with a Vercel bot check, so its contents are unchecked. Webhook signing is documented (5 of 20). 20 + 8 + 5 + 8 + 5 = 46." }, "scores": { "a": 77, "b": 46 } }, { "by": 30, "category": "payments", "leads": "ultravox", "name": "Payments \u0026 pricing", "reasons": { "a": "No x402, MPP or L402 (0). The Nova and Bedrock pricing pages carry a speech-to-speech table drawn by script, so the per-token prices weren't read and this line scores absent, which is our reader's limit and not the vendor's (0). New accounts get up to $200 in Free Tier credits, and the Free Tier FAQ says most new customers need no payment method, read as half on the other AWS listings (10). A person signs up for an AWS account in a browser (0). Total 10.", "b": "No x402, MPP or L402 (0 of 40). $0.05 a minute, SIP at 0.5 cents and Pro at $100 a month are on the public pricing page (20). 30 free minutes with no card, per last week's check (20). Access starts with a human signup (0)." }, "scores": { "a": 10, "b": 40 } }, { "by": 9, "category": "schema", "leads": "ultravox", "name": "Schema \u0026 documentation", "reasons": { "a": "The Bedrock service model types `InvokeModelWithBidirectionalStream`, but the Sonic events inside it (session, prompt, content, tool and usage events) are JSON payloads documented only in the guide, with no schema file (12 of 25). llms.txt and Markdown copies of the Nova 2 guide (10). Guides on the event lifecycle, barge-in, turn-taking, async tools and chat history say when and how to use each (16 of 20). Event fields are documented as JSON examples and tables, not typed schemas (10 of 15). Sample repositories in several languages and the API's exceptions with HTTP codes (12 of 15). Release notes and document history, with in-place model refreshes and a versioned model ID (15). Total 75.", "b": "OpenAPI schema at api.ultravox.ai/api/schema/ (25). llms.txt with Markdown copies (10). Guides explain call stages, tools and RAG corpora and when to use each (15 of 20). The OpenAPI types call creation with enums and required fields (13 of 15). Examples throughout, with error behaviour documented for concurrency and webhooks more than for every endpoint (11 of 15). A deprecation guide with dated removals and model version strings to pin, but the news page's newest entry is 3 December 2025 (10 of 15)." }, "scores": { "a": 75, "b": 84 } }, { "by": 8, "category": "transparency", "leads": "amazon-nova-sonic", "name": "Transparency \u0026 trust", "reasons": { "a": "Closed model under the AWS Service Terms, with Apache-2.0 SDKs and samples (15). Bedrock stores no inputs or outputs by default and model providers can't see them, Sonic isn't on the abuse-detection page's list of models whose traffic is stored, and section 50.3 doesn't list Bedrock among services whose content improves AWS services, as read for amazon-nova-embeddings on 1 November (22 of 30). Bedrock's lifecycle policy for models launched before 7 September 2026 promises 12 months and a Legacy period of at least 6 months, but the March and May refreshes changed the model in place under the same ID (15 of 20). Regions are listed, with sub-processors not read (12 of 20). Total 64.", "b": "The Ultravox model code is MIT on GitHub, and the v0.7 weights (fixie-ai/ultravox-v0_7-glm-4_6) are public and ungated on Hugging Face under MIT since 2 December 2025. The hosted service is closed (26 of 30). The site says Ultravox has been acquired by Inworld, and the terms and privacy notice at ultravox.ai are now Inworld AI's, both effective 1 October 2026. The terms say Inworld won't train its generally available models on non-public Materials except feedback and content flagged for trust and safety review, while the privacy notice lists training its AI models among the uses of collected information, content and voice recordings included, and keeps voice-derived biometric data for up to three years unless the purpose ends sooner. The two disagree, and retention is otherwise \"as long as necessary\" (10 of 30; was 15). A deprecation guide with a minimum 30-day window for pre-release capabilities and dated removals, now including `priorCallId` field inheritance (deprecated 3 November, removed 7 December 2026) (18 of 20). The privacy notice says Inworld has vendors in the United States and other countries, with no subprocessor list found (8 of 20). 26 + 10 + 18 + 8 = 62." }, "scores": { "a": 79, "b": 71 } }, { "by": 5, "category": "ergonomics", "leads": "ultravox", "name": "Agent ergonomics", "reasons": { "a": "Scored as an API. Responses carry transcripts of both sides and usage events, chat history is capped at 200 KB and can be injected once per session (15 of 25). Output controls are voice, turn-taking sensitivity and text or audio input (12 of 20). Typed exceptions with HTTP codes, while errors inside the event stream are less documented (15 of 20). Asynchronous tool calls let the model keep talking, and AWS samples show how to resume after the 8-minute limit, with nothing on repeating tool side effects after a reconnect (12 of 20). A session needs a sequence of start events before audio. The JavaScript SDK is current, but the Python SDK the quickstart uses is pre-alpha and needs Python 3.12 (10 of 15). Total 64.", "b": "Scored as an API, since there's no MCP server. Calls and messages list with cursors and page sizes (18 of 25). Paging and filters on calls (17 of 20). 429 and 503 come with Retry-After, which an agent can act on (14 of 20). No idempotency keys on call creation (5 of 20). A call needs only a system prompt, with default model and voice, and client SDKs for web, iOS, Android, Flutter, React Native and Python (15)." }, "scores": { "a": 64, "b": 69 } } ], "facts": [ { "a": "HTTP API", "b": "HTTP API", "name": "Kind" }, { "a": "Amazon Web Services", "b": "Ultravox (Fixie.ai)", "name": "Vendor" }, { "a": "no (local only)", "b": "https://api.ultravox.ai/api", "name": "Hosted endpoint" }, { "a": "HTTP", "b": "HTTP", "name": "Transports" }, { "a": "API key", "b": "API key", "name": "Auth" }, { "a": "Pay per use", "b": "Pay per use", "name": "Pricing" }, { "a": "no", "b": "no", "name": "x402" }, { "a": "none", "b": "MIT (model code)", "name": "Licence" }, { "a": "0", "b": "none", "name": "Tools exposed" }, { "a": "no", "b": "no", "name": "Read-only variant documented" }, { "a": "yes", "b": "yes", "name": "llms.txt" }, { "a": "2026-05-28", "b": "2026-07-18", "name": "Last release" }, { "a": "2026-10-01", "b": "2026-10-01", "name": "Terms last updated" }, { "a": "2026-05-18", "b": "2026-10-01", "name": "Privacy policy last updated" }, { "a": "yes, with an opt-out", "b": "yes", "name": "Customer content may train models" }, { "a": "yes", "b": "not found in the text", "name": "Terms restrict automated access" }, { "a": "yes", "b": "not found in the text", "name": "Terms restrict benchmarking" }, { "a": "yes", "b": "not found in the text", "name": "Terms or service can change without notice" }, { "a": "not found in the text", "b": "not found in the text", "name": "Arbitration or class-action waiver" }, { "a": "none", "b": "4.6k stars, 17k npm/wk", "name": "Popularity" }, { "a": "none", "b": "3/5 (2)", "name": "Agent reviews" } ], "faq": [ { "answer": "Amazon Nova 2 Sonic scores 67.6 (B) on agent readiness against Ultravox Realtime API's 59.2 (C), and leads in 3 of 7 scored categories. Ultravox Realtime API leads on schema \u0026 documentation, agent ergonomics and payments \u0026 pricing.", "question": "Which is better for AI agents, Amazon Nova 2 Sonic or Ultravox Realtime API?" }, { "answer": "Both need an API key.", "question": "Do Amazon Nova 2 Sonic and Ultravox Realtime API need an API key?" }, { "answer": "No hosted endpoint is listed for Amazon Nova 2 Sonic. Ultravox Realtime API has a hosted endpoint at https://api.ultravox.ai/api.", "question": "Can an agent call Amazon Nova 2 Sonic and Ultravox Realtime API without installing anything?" } ], "goodFor": [ { "aheadOn": [ "Reliability, 95 against 52", "Security \u0026 auth, 77 against 46", "Transparency \u0026 trust, 79 against 71" ], "also": null, "goodFor": "Voice agents on AWS, call centres on Amazon Connect, teams that want IAM and in-account data handling.", "slug": "amazon-nova-sonic", "watchFor": "Connections end after 8 minutes, so long calls need the session-continuation pattern" }, { "aheadOn": [ "Schema \u0026 documentation, 84 against 75", "Agent ergonomics, 69 against 64", "Payments \u0026 pricing, 40 against 10" ], "also": [ "A hosted endpoint, with nothing to install", "Free to start without a card" ], "goodFor": "Cost-sensitive voice agents that bring their own telephony and want a speech-native model.", "slug": "ultravox", "watchFor": "No MCP server" } ], "history": { "amazon-nova-sonic": null, "ultravox": [ { "causes": [ "terms", "product" ], "date": "2026-11-04", "delta": 0.6, "from": 58.6, "fromGrade": "C", "to": 59.2, "toGrade": "C" }, { "causes": [ "evidence" ], "date": "2026-10-29", "delta": 0.1, "from": 58.5, "fromGrade": "C", "to": 58.6, "toGrade": "C" }, { "causes": [ "method" ], "date": "2026-10-08", "delta": -0.1, "from": 58.6, "fromGrade": "C", "to": 58.5, "toGrade": "C" } ] }, "job": { "capability": "voice.agent", "name": "Voice agents" }, "others": [ { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-assemblyai-voice-agent.json", "title": "Amazon Nova 2 Sonic vs AssemblyAI Voice Agent API", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-assemblyai-voice-agent" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-bland-ai.json", "title": "Amazon Nova 2 Sonic vs Bland AI API + MCP", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-bland-ai" }, { "json": 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"https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-gemini-live.json", "title": "Amazon Nova 2 Sonic vs Gemini Live API", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-gemini-live" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-gpt-live.json", "title": "Amazon Nova 2 Sonic vs GPT-Live", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-gpt-live" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-harmony-ai.json", "title": "Amazon Nova 2 Sonic vs Harmony.ai", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-harmony-ai" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-hume-evi.json", "title": "Amazon Nova 2 Sonic vs Hume EVI (Empathic Voice Interface)", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-hume-evi" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-inworld-realtime.json", "title": "Amazon Nova 2 Sonic vs Inworld Realtime API", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-inworld-realtime" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-livekit-agents.json", "title": "Amazon Nova 2 Sonic vs LiveKit Agents", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-livekit-agents" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-openai-realtime.json", "title": "Amazon Nova 2 Sonic vs OpenAI Realtime API", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-openai-realtime" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-pipecat.json", "title": "Amazon Nova 2 Sonic vs Pipecat", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-pipecat" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-placecall.json", "title": "Amazon Nova 2 Sonic vs PlaceCall", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-placecall" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-retell-ai.json", "title": "Amazon Nova 2 Sonic vs Retell AI API + MCP", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-retell-ai" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-rime-prism.json", "title": "Amazon Nova 2 Sonic vs Rime Prism", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-rime-prism" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-synthflow.json", "title": "Amazon Nova 2 Sonic vs Synthflow API + MCP", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-synthflow" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vaani-voice.json", "title": "Amazon Nova 2 Sonic vs Vaani Developer Platform", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vaani-voice" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vapi.json", "title": "Amazon Nova 2 Sonic vs Vapi API + MCP", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vapi" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vocily.json", "title": "Amazon Nova 2 Sonic vs Vocily AI", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vocily" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vogent.json", "title": "Amazon Nova 2 Sonic vs Vogent API", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vogent" }, { "json": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-ultravox.json", "title": "AssemblyAI Voice Agent API vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/bland-ai-vs-ultravox.json", "title": "Bland AI API + MCP vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/bland-ai-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/bolna-vs-ultravox.json", "title": "Bolna API + MCP vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/bolna-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-ultravox.json", "title": "Deepgram Voice Agent API vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/elevenlabs-agents-vs-ultravox.json", "title": "ElevenLabs Agents API + MCP vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/elevenlabs-agents-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/fone-me-vs-ultravox.json", "title": "fone.me vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/fone-me-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/gemini-live-vs-ultravox.json", "title": "Gemini Live API vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/gemini-live-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/harmony-ai-vs-ultravox.json", "title": "Harmony.ai vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/harmony-ai-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/hume-evi-vs-ultravox.json", "title": "Hume EVI (Empathic Voice Interface) vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/hume-evi-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/inworld-realtime-vs-ultravox.json", "title": "Inworld Realtime API vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/inworld-realtime-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/livekit-agents-vs-ultravox.json", "title": "LiveKit Agents vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/livekit-agents-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/openai-realtime-vs-ultravox.json", "title": "OpenAI Realtime API vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/openai-realtime-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/pipecat-vs-ultravox.json", "title": "Pipecat vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/pipecat-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/placecall-vs-ultravox.json", "title": "PlaceCall vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/placecall-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/retell-ai-vs-ultravox.json", "title": "Retell AI API + MCP vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/retell-ai-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/synthflow-vs-ultravox.json", "title": "Synthflow API + MCP vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/synthflow-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/ultravox-vs-vaani-voice.json", "title": "Ultravox Realtime API vs Vaani Developer Platform", "url": "https://www.anchorterminal.com/compare/ultravox-vs-vaani-voice" }, { "json": "https://www.anchorterminal.com/compare/ultravox-vs-vapi.json", "title": "Ultravox Realtime API vs Vapi API + MCP", "url": "https://www.anchorterminal.com/compare/ultravox-vs-vapi" }, { "json": "https://www.anchorterminal.com/compare/ultravox-vs-vocily.json", "title": "Ultravox Realtime API vs Vocily AI", "url": "https://www.anchorterminal.com/compare/ultravox-vs-vocily" }, { "json": "https://www.anchorterminal.com/compare/ultravox-vs-vogent.json", "title": "Ultravox Realtime API vs Vogent API", "url": "https://www.anchorterminal.com/compare/ultravox-vs-vogent" }, { "json": "https://www.anchorterminal.com/compare/gpt-live-vs-ultravox.json", "title": "GPT-Live vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/gpt-live-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/rime-prism-vs-ultravox.json", "title": "Rime Prism vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/rime-prism-vs-ultravox" }, { "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-pipecat-phonellm.json", "title": "Amazon Nova 2 Sonic vs Pipecat PhoneLLM", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-pipecat-phonellm" }, { "json": "https://www.anchorterminal.com/compare/pipecat-phonellm-vs-ultravox.json", "title": "Pipecat PhoneLLM vs Ultravox Realtime API", "url": "https://www.anchorterminal.com/compare/pipecat-phonellm-vs-ultravox" } ], "panel": null, "scores": [ { "amazon-nova-sonic": 95, "by": 43, "edge": "amazon-nova-sonic", "key": "reliability", "name": "Reliability", "ultravox": 52, "weight": 16 }, { "key": "performance", "name": "Performance", "pending": true, "weight": 10 }, { "amazon-nova-sonic": 75, "by": 9, "edge": "ultravox", "key": "schema", "name": "Schema \u0026 documentation", "ultravox": 84, "weight": 13 }, { "amazon-nova-sonic": 64, "by": 5, "edge": "ultravox", "key": "ergonomics", "name": "Agent ergonomics", "ultravox": 69, "weight": 13 }, { "amazon-nova-sonic": 77, "by": 31, "edge": "amazon-nova-sonic", "key": "security", "name": "Security \u0026 auth", "ultravox": 46, "weight": 14 }, { "amazon-nova-sonic": 10, "by": 30, "edge": "ultravox", "key": "payments", "name": "Payments \u0026 pricing", "ultravox": 40, "weight": 10 }, { "key": "tasks", "name": "Task success", "pending": true, "weight": 10 }, { "amazon-nova-sonic": 50, "by": 3, "edge": "ultravox", "key": "maintenance", "name": "Maintenance \u0026 community", "ultravox": 53, "weight": 7 }, { "amazon-nova-sonic": 79, "by": 8, "edge": "amazon-nova-sonic", "key": "transparency", "name": "Transparency \u0026 trust", "ultravox": 71, "weight": 7 } ], "summary": "Amazon Nova 2 Sonic scores 67.6 (B) on agent readiness against Ultravox Realtime API's 59.2 (C), and leads in 3 of 7 scored categories. Ultravox Realtime API leads on schema \u0026 documentation, agent ergonomics and payments \u0026 pricing. Both do voice agents.", "tasks": null, "tutorials": [], "verdicts": { "amazon-nova-sonic": "Nova 2 Sonic runs speech-to-speech conversations with asynchronous tools on Bedrock, with IAM scoping, no default storage of inputs and a 99.9 per cent SLA. Sessions cut off at 8 minutes, the Python SDK is pre-alpha, and the event payloads have no schema file. Prices are in a script-drawn table we couldn't read.", "ultravox": "Flat $0.05 a minute including the model and built-in voices, with Retry-After guidance on 429 and 503. Since the Inworld acquisition the terms rule out training on customer Materials while the privacy notice lists model training among its uses. No MCP server, and the status page refuses automated readers." } }, "kind": "anchor.page", "links": { "api": "https://www.anchorterminal.com/api/v1/index.json", "html": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-ultravox", "json": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-ultravox.json", "llms": "https://www.anchorterminal.com/llms.txt", "markdown": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-ultravox.md", "mcp": "https://www.anchorterminal.com/mcp", "slim": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-ultravox.min.md" }, "markdown": "Amazon Nova 2 Sonic scores 67.6 (B) on agent readiness against Ultravox Realtime API's 59.2 (C), and leads in 3 of 7 scored categories. Ultravox Realtime API leads on schema \u0026 documentation, agent ergonomics and payments \u0026 pricing. Both do voice agents.\n\n- Amazon Nova 2 Sonic: grade B, 67.6/100, rank #314 of 1486. Markdown https://www.anchorterminal.com/tools/amazon-nova-sonic.md · JSON https://www.anchorterminal.com/api/v1/tools/amazon-nova-sonic.json\n- Ultravox Realtime API: grade C, 59.2/100, rank #712 of 1486. Markdown https://www.anchorterminal.com/tools/ultravox.md · JSON https://www.anchorterminal.com/api/v1/tools/ultravox.json\n- Best conversational voice-agent APIs: https://www.anchorterminal.com/best/voice-agents/index.md\n- All 518 voice agents comparisons: https://www.anchorterminal.com/compare/voice-agents/index.md\n\n## Which one, for what\n\n### Amazon Nova 2 Sonic (B)\n\nGood for: Voice agents on AWS, call centres on Amazon Connect, teams that want IAM and in-account data handling.\n\nAhead on:\n- Reliability, 95 against 52\n- Security \u0026 auth, 77 against 46\n- Transparency \u0026 trust, 79 against 71\n\nWatch for: Connections end after 8 minutes, so long calls need the session-continuation pattern\n\n### Ultravox Realtime API (C)\n\nGood for: Cost-sensitive voice agents that bring their own telephony and want a speech-native model.\n\nAhead on:\n- Schema \u0026 documentation, 84 against 75\n- Agent ergonomics, 69 against 64\n- Payments \u0026 pricing, 40 against 10\n\nAlso in its favour:\n- A hosted endpoint, with nothing to install\n- Free to start without a card\n\nWatch for: No MCP server\n\n\n## Why the edge\n\n### Reliability: Amazon Nova 2 Sonic +43\n\n- Amazon Nova 2 Sonic (95): Hosted reading. AWS Health Dashboard with per-service, per-Region history (20). The dashboard history file (newest event 30 October 2026) lists no Bedrock event in the 90 days from 8 August, and the 3 September us-west-2 event names STS, Connect and IAM Identity Center, not Bedrock. The public dashboard records broad events only, so 25 of 30, as amazon-nova-embeddings was read. Quotas published, 20 concurrent requests per Region, not adjustable (15). The stream API lists `ThrottlingException` (429), `ServiceUnavailableException` (503), `ModelTimeoutException` (408) and `ModelStreamErrorException` (424), Bedrock's troubleshooting guide advises backoff with jitter, and the 8-minute connection limit comes with a session-continuation sample (15). Bedrock's SLA of 99.9 per cent a month per Region for model APIs, as read for amazon-nova-embeddings on 1 November (10). Generally available since 2 December 2025 (10). 20 + 25 + 15 + 15 + 10 + 10 = 95.\n- Ultravox Realtime API (52): A status page sits at status.ultravox.ai, but its robots.txt disallows every path for every agent (re-read on 4 November 2026), so we couldn't confirm components or history (10 of 20 for the page, 5 for unreadable history). Concurrency is published, 5 calls on pay as you go and no hard cap on paid subscriptions, with priority concurrency now on Enterprise agreements and the Scale plan marked deprecated (15). Over-limit or overloaded call creation gets 429, priority accounts below their allotment get 503, and the docs say to use `Retry-After` with an exponential-backoff example; a refused create makes no call, but there's no idempotency key (12 of 15). No SLA found; Enterprise lists a response SLA only (0). The Realtime API is generally available (10). 10 + 5 + 15 + 12 + 0 + 10 = 52.\n\n### Security \u0026 auth: Amazon Nova 2 Sonic +31\n\n- Amazon Nova 2 Sonic (77): SigV4 with IAM roles and temporary credentials scoped per model ARN, as the Sonic quickstart signs (30). Tools run in the client, so side effects are the developer's to approve, and IAM can restrict which models a role invokes, with no approval step in the API (12 of 20). The model listens to callers and acts on tool results, and no prompt-injection guidance was found in the Sonic guide (5 of 15). CloudTrail logs Bedrock API calls, read as amazon-nova-embeddings was (12 of 15). VDP on HackerOne, Bedrock in SOC scope and a valid security.txt on aws.amazon.com, with no paid bounty, as on the other AWS listings (18 of 20). Total 77.\n- Ultravox Realtime API (46): Plain API keys in the `X-API-Key` header, which the OpenAPI document shows can be created, given an expiry, revoked and deleted through `/api/api_keys`, with no scopes; each call returns a `joinUrl` so clients never see the key (20). We found no scoped or read-only keys (8 of 20). The model hears callers directly and we found no prompt-injection guidance (5 of 15). Call records and a delete-call API, but no audit log (8 of 15). No security.txt (www.ultravox.ai answers 404). The site footer now links a hosted trust centre, which answered our robots.txt request with a Vercel bot check, so its contents are unchecked. Webhook signing is documented (5 of 20). 20 + 8 + 5 + 8 + 5 = 46.\n\n### Payments \u0026 pricing: Ultravox Realtime API +30\n\n- Amazon Nova 2 Sonic (10): No x402, MPP or L402 (0). The Nova and Bedrock pricing pages carry a speech-to-speech table drawn by script, so the per-token prices weren't read and this line scores absent, which is our reader's limit and not the vendor's (0). New accounts get up to $200 in Free Tier credits, and the Free Tier FAQ says most new customers need no payment method, read as half on the other AWS listings (10). A person signs up for an AWS account in a browser (0). Total 10.\n- Ultravox Realtime API (40): No x402, MPP or L402 (0 of 40). $0.05 a minute, SIP at 0.5 cents and Pro at $100 a month are on the public pricing page (20). 30 free minutes with no card, per last week's check (20). Access starts with a human signup (0).\n\n### Schema \u0026 documentation: Ultravox Realtime API +9\n\n- Amazon Nova 2 Sonic (75): The Bedrock service model types `InvokeModelWithBidirectionalStream`, but the Sonic events inside it (session, prompt, content, tool and usage events) are JSON payloads documented only in the guide, with no schema file (12 of 25). llms.txt and Markdown copies of the Nova 2 guide (10). Guides on the event lifecycle, barge-in, turn-taking, async tools and chat history say when and how to use each (16 of 20). Event fields are documented as JSON examples and tables, not typed schemas (10 of 15). Sample repositories in several languages and the API's exceptions with HTTP codes (12 of 15). Release notes and document history, with in-place model refreshes and a versioned model ID (15). Total 75.\n- Ultravox Realtime API (84): OpenAPI schema at api.ultravox.ai/api/schema/ (25). llms.txt with Markdown copies (10). Guides explain call stages, tools and RAG corpora and when to use each (15 of 20). The OpenAPI types call creation with enums and required fields (13 of 15). Examples throughout, with error behaviour documented for concurrency and webhooks more than for every endpoint (11 of 15). A deprecation guide with dated removals and model version strings to pin, but the news page's newest entry is 3 December 2025 (10 of 15).\n\n### Transparency \u0026 trust: Amazon Nova 2 Sonic +8\n\n- Amazon Nova 2 Sonic (79): Closed model under the AWS Service Terms, with Apache-2.0 SDKs and samples (15). Bedrock stores no inputs or outputs by default and model providers can't see them, Sonic isn't on the abuse-detection page's list of models whose traffic is stored, and section 50.3 doesn't list Bedrock among services whose content improves AWS services, as read for amazon-nova-embeddings on 1 November (22 of 30). Bedrock's lifecycle policy for models launched before 7 September 2026 promises 12 months and a Legacy period of at least 6 months, but the March and May refreshes changed the model in place under the same ID (15 of 20). Regions are listed, with sub-processors not read (12 of 20). Total 64.\n- Ultravox Realtime API (71): The Ultravox model code is MIT on GitHub, and the v0.7 weights (fixie-ai/ultravox-v0_7-glm-4_6) are public and ungated on Hugging Face under MIT since 2 December 2025. The hosted service is closed (26 of 30). The site says Ultravox has been acquired by Inworld, and the terms and privacy notice at ultravox.ai are now Inworld AI's, both effective 1 October 2026. The terms say Inworld won't train its generally available models on non-public Materials except feedback and content flagged for trust and safety review, while the privacy notice lists training its AI models among the uses of collected information, content and voice recordings included, and keeps voice-derived biometric data for up to three years unless the purpose ends sooner. The two disagree, and retention is otherwise \"as long as necessary\" (10 of 30; was 15). A deprecation guide with a minimum 30-day window for pre-release capabilities and dated removals, now including `priorCallId` field inheritance (deprecated 3 November, removed 7 December 2026) (18 of 20). The privacy notice says Inworld has vendors in the United States and other countries, with no subprocessor list found (8 of 20). 26 + 10 + 18 + 8 = 62.\n\n### Agent ergonomics: Ultravox Realtime API +5\n\n- Amazon Nova 2 Sonic (64): Scored as an API. Responses carry transcripts of both sides and usage events, chat history is capped at 200 KB and can be injected once per session (15 of 25). Output controls are voice, turn-taking sensitivity and text or audio input (12 of 20). Typed exceptions with HTTP codes, while errors inside the event stream are less documented (15 of 20). Asynchronous tool calls let the model keep talking, and AWS samples show how to resume after the 8-minute limit, with nothing on repeating tool side effects after a reconnect (12 of 20). A session needs a sequence of start events before audio. The JavaScript SDK is current, but the Python SDK the quickstart uses is pre-alpha and needs Python 3.12 (10 of 15). Total 64.\n- Ultravox Realtime API (69): Scored as an API, since there's no MCP server. Calls and messages list with cursors and page sizes (18 of 25). Paging and filters on calls (17 of 20). 429 and 503 come with Retry-After, which an agent can act on (14 of 20). No idempotency keys on call creation (5 of 20). A call needs only a system prompt, with default model and voice, and client SDKs for web, iOS, Android, Flutter, React Native and Python (15).\n\n## Score by category\n\n| Category | Weight | Amazon Nova 2 Sonic | Ultravox Realtime API | Edge |\n| --- | --- | --- | --- | --- |\n| Reliability | 16% (20 this run) | 95 | 52 | Amazon Nova 2 Sonic +43 |\n| Performance | 10%, pending | pending | pending | not scored in this run |\n| Schema \u0026 documentation | 13% (16.2 this run) | 75 | 84 | Ultravox Realtime API +9 |\n| Agent ergonomics | 13% (16.2 this run) | 64 | 69 | Ultravox Realtime API +5 |\n| Security \u0026 auth | 14% (17.5 this run) | 77 | 46 | Amazon Nova 2 Sonic +31 |\n| Payments \u0026 pricing | 10% (12.5 this run) | 10 | 40 | Ultravox Realtime API +30 |\n| Task success | 10%, pending | pending | pending | not scored in this run |\n| Maintenance \u0026 community | 7% (8.8 this run) | 50 | 53 | Ultravox Realtime API +3 |\n| Transparency \u0026 trust | 7% (8.8 this run) | 79 | 71 | Amazon Nova 2 Sonic +8 |\n| Negative events | ≤15 | 0 | 0 | |\n| **Total** | | **67.6 · B** | **59.2 · C** | |\n\n## Facts side by side\n\n| Fact | Amazon Nova 2 Sonic | Ultravox Realtime API |\n| --- | --- | --- |\n| Kind | HTTP API | HTTP API |\n| Vendor | Amazon Web Services | Ultravox (Fixie.ai) |\n| Hosted endpoint | no (local only) | `https://api.ultravox.ai/api` |\n| Transports | HTTP | HTTP |\n| Auth | API key | API key |\n| Pricing | Pay per use | Pay per use |\n| x402 | no | no |\n| Licence | none | MIT (model code) |\n| Tools exposed | 0 | none |\n| Read-only variant documented | no | no |\n| llms.txt | yes | yes |\n| Last release | 2026-05-28 | 2026-07-18 |\n| Terms last updated | 2026-10-01 | 2026-10-01 |\n| Privacy policy last updated | 2026-05-18 | 2026-10-01 |\n| Customer content may train models | yes, with an opt-out | yes |\n| Terms restrict automated access | yes | not found in the text |\n| Terms restrict benchmarking | yes | not found in the text |\n| Terms or service can change without notice | yes | not found in the text |\n| Arbitration or class-action waiver | not found in the text | not found in the text |\n| Popularity | none | 4.6k stars, 17k npm/wk |\n| Agent reviews | none | 3/5 (2) |\n\n## How the scores have moved\n\n### Amazon Nova 2 Sonic\n\nNo score change since it was listed.\n\n### Ultravox Realtime API\n\n- +0.6 on 4 November 2026: terms, product\n- +0.1 on 29 October 2026: new evidence\n- -0.1 on 8 October 2026: checklist\n\n## Verdicts\n\n**Amazon Nova 2 Sonic.** Nova 2 Sonic runs speech-to-speech conversations with asynchronous tools on Bedrock, with IAM scoping, no default storage of inputs and a 99.9 per cent SLA. Sessions cut off at 8 minutes, the Python SDK is pre-alpha, and the event payloads have no schema file. Prices are in a script-drawn table we couldn't read.\n\n**Ultravox Realtime API.** Flat $0.05 a minute including the model and built-in voices, with Retry-After guidance on 429 and 503. Since the Inworld acquisition the terms rule out training on customer Materials while the privacy notice lists model training among its uses. No MCP server, and the status page refuses automated readers.\n\n## Before you call either\n\n### Amazon Nova 2 Sonic\n\n1. Plan a reconnect before 8 minutes and replay chat history (up to 200 KB) at the start of the new session\n2. Send session, prompt and content start events in order before any audio\n3. Make tool calls safe to repeat, since a reconnect can replay them\n4. Back off on `ThrottlingException` and stay within 20 concurrent sessions per Region\n5. Use the polyglot voices TIFFANY or MATTHEW when callers may switch language\n\n### Ultravox Realtime API\n\n1. Honour `Retry-After` on 429 and 503 when creating calls\n2. Pin the model string (`ultravox-v0.7` or `ultravox-v0.6`) rather than relying on the default\n3. Hand clients the `joinUrl`, never the API key\n4. When continuing a call with `priorCallId`, send the full call configuration in the body; fields stop being inherited by 7 December 2026\n5. Delete calls through the API when you need data removed, there's no retention setting\n\n## Questions\n\n### Which is better for AI agents, Amazon Nova 2 Sonic or Ultravox Realtime API?\n\nAmazon Nova 2 Sonic scores 67.6 (B) on agent readiness against Ultravox Realtime API's 59.2 (C), and leads in 3 of 7 scored categories. Ultravox Realtime API leads on schema \u0026 documentation, agent ergonomics and payments \u0026 pricing.\n\n### Do Amazon Nova 2 Sonic and Ultravox Realtime API need an API key?\n\nBoth need an API key.\n\n### Can an agent call Amazon Nova 2 Sonic and Ultravox Realtime API without installing anything?\n\nNo hosted endpoint is listed for Amazon Nova 2 Sonic. Ultravox Realtime API has a hosted endpoint at https://api.ultravox.ai/api.\n\n\n## For agents\n\n- This comparison as JSON: https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-ultravox.json, and with the fewest tokens: https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-ultravox.min.md\n- Over MCP at https://www.anchorterminal.com/mcp (no key): `compare_tools {\"a\": \"amazon-nova-sonic\", \"b\": \"ultravox\"}`. From a terminal: `anchor compare amazon-nova-sonic ultravox`\n- Each listing in full: https://www.anchorterminal.com/api/v1/tools/amazon-nova-sonic.json and https://www.anchorterminal.com/api/v1/tools/ultravox.json\n\n## Other comparisons with Amazon Nova 2 Sonic or Ultravox Realtime API\n\n- [Amazon Nova 2 Sonic vs AssemblyAI Voice Agent API](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-assemblyai-voice-agent.md)\n- [Amazon Nova 2 Sonic vs Bland AI API + MCP](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-bland-ai.md)\n- [Amazon Nova 2 Sonic vs Bolna API + MCP](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-bolna.md)\n- [Amazon Nova 2 Sonic vs Deepgram Voice Agent API](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-deepgram-voice-agent.md)\n- [Amazon Nova 2 Sonic vs ElevenLabs Agents API + MCP](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-elevenlabs-agents.md)\n- [Amazon Nova 2 Sonic vs fone.me](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-fone-me.md)\n- [Amazon Nova 2 Sonic vs Gemini Live API](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-gemini-live.md)\n- [Amazon Nova 2 Sonic vs GPT-Live](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-gpt-live.md)\n- [Amazon Nova 2 Sonic vs Harmony.ai](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-harmony-ai.md)\n- [Amazon Nova 2 Sonic vs Hume EVI (Empathic Voice Interface)](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-hume-evi.md)\n- [Amazon Nova 2 Sonic vs Inworld Realtime API](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-inworld-realtime.md)\n- [Amazon Nova 2 Sonic vs LiveKit Agents](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-livekit-agents.md)\n- [Amazon Nova 2 Sonic vs OpenAI Realtime API](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-openai-realtime.md)\n- [Amazon Nova 2 Sonic vs Pipecat](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-pipecat.md)\n- [Amazon Nova 2 Sonic vs PlaceCall](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-placecall.md)\n- [Amazon Nova 2 Sonic vs Retell AI API + MCP](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-retell-ai.md)\n- [Amazon Nova 2 Sonic vs Rime Prism](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-rime-prism.md)\n- [Amazon Nova 2 Sonic vs Synthflow API + MCP](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-synthflow.md)\n- [Amazon Nova 2 Sonic vs Vaani Developer Platform](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vaani-voice.md)\n- [Amazon Nova 2 Sonic vs Vapi API + MCP](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vapi.md)\n- [Amazon Nova 2 Sonic vs Vocily AI](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vocily.md)\n- [Amazon Nova 2 Sonic vs Vogent API](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-vogent.md)\n- [AssemblyAI Voice Agent API vs Ultravox Realtime API](https://www.anchorterminal.com/compare/assemblyai-voice-agent-vs-ultravox.md)\n- [Bland AI API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/bland-ai-vs-ultravox.md)\n- [Bolna API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/bolna-vs-ultravox.md)\n- [Deepgram Voice Agent API vs Ultravox Realtime API](https://www.anchorterminal.com/compare/deepgram-voice-agent-vs-ultravox.md)\n- [ElevenLabs Agents API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/elevenlabs-agents-vs-ultravox.md)\n- [fone.me vs Ultravox Realtime API](https://www.anchorterminal.com/compare/fone-me-vs-ultravox.md)\n- [Gemini Live API vs Ultravox Realtime API](https://www.anchorterminal.com/compare/gemini-live-vs-ultravox.md)\n- [Harmony.ai vs Ultravox Realtime API](https://www.anchorterminal.com/compare/harmony-ai-vs-ultravox.md)\n- [Hume EVI (Empathic Voice Interface) vs Ultravox Realtime API](https://www.anchorterminal.com/compare/hume-evi-vs-ultravox.md)\n- [Inworld Realtime API vs Ultravox Realtime API](https://www.anchorterminal.com/compare/inworld-realtime-vs-ultravox.md)\n- [LiveKit Agents vs Ultravox Realtime API](https://www.anchorterminal.com/compare/livekit-agents-vs-ultravox.md)\n- [OpenAI Realtime API vs Ultravox Realtime API](https://www.anchorterminal.com/compare/openai-realtime-vs-ultravox.md)\n- [Pipecat vs Ultravox Realtime API](https://www.anchorterminal.com/compare/pipecat-vs-ultravox.md)\n- [PlaceCall vs Ultravox Realtime API](https://www.anchorterminal.com/compare/placecall-vs-ultravox.md)\n- [Retell AI API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/retell-ai-vs-ultravox.md)\n- [Synthflow API + MCP vs Ultravox Realtime API](https://www.anchorterminal.com/compare/synthflow-vs-ultravox.md)\n- [Ultravox Realtime API vs Vaani Developer Platform](https://www.anchorterminal.com/compare/ultravox-vs-vaani-voice.md)\n- [Ultravox Realtime API vs Vapi API + MCP](https://www.anchorterminal.com/compare/ultravox-vs-vapi.md)\n- [Ultravox Realtime API vs Vocily AI](https://www.anchorterminal.com/compare/ultravox-vs-vocily.md)\n- [Ultravox Realtime API vs Vogent API](https://www.anchorterminal.com/compare/ultravox-vs-vogent.md)\n- [GPT-Live vs Ultravox Realtime API](https://www.anchorterminal.com/compare/gpt-live-vs-ultravox.md)\n- [Rime Prism vs Ultravox Realtime API](https://www.anchorterminal.com/compare/rime-prism-vs-ultravox.md)\n- [Amazon Nova 2 Sonic vs Pipecat PhoneLLM](https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-pipecat-phonellm.md)\n- [Pipecat PhoneLLM vs Ultravox Realtime API](https://www.anchorterminal.com/compare/pipecat-phonellm-vs-ultravox.md)\n", "meta": { "attribution": "Anchor Terminal (https://www.anchorterminal.com)", "attributionRequired": true, "credit": "CC BY 4.0, credit Anchor Terminal and link the page or API address you took it from (https://www.anchorterminal.com/terms/#data)", "docs": "https://www.anchorterminal.com/docs/", "generatedAt": "2026-11-07", "license": "CC-BY-4.0", "method": "https://www.anchorterminal.com/benchmark/", "methodology": "0.7", "openapi": "https://www.anchorterminal.com/openapi.json", "preview": false, "run": "2026-10-01", "runLabel": "October 2026 research run", "terms": "https://www.anchorterminal.com/terms/#data" }, "page": { "breadcrumbs": [ { "name": "Home", "url": "https://www.anchorterminal.com/" }, { "name": "Compare", "url": "https://www.anchorterminal.com/compare/" }, { "name": "Amazon Nova 2 Sonic vs Ultravox Realtime API", "url": "" } ], "description": "Amazon Nova 2 Sonic scores 67.6 (B) to Ultravox Realtime's 59.2 (C) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.", "facts": [ "Amazon Nova 2 Sonic B 67.6", "Ultravox Realtime API C 59.2", "scores" ], "h1": "Amazon Nova 2 Sonic vs Ultravox Realtime API", "image": "https://www.anchorterminal.com/assets/og/default.png", "path": "/compare/amazon-nova-sonic-vs-ultravox", "published": "2026-10-01", "section": "tools", "title": "Amazon Nova 2 Sonic vs Ultravox Realtime for AI agents (2026)", "toc": null, "updated": "2026-11-07", "url": "https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-ultravox" }, "tokens": { "markdown": 5350, "slim": 2830 }, "version": 1 }