# Amazon Nova 2 Sonic vs AssemblyAI Voice Agent API (slim)

> Amazon Nova 2 Sonic scores 67.6 (B) to AssemblyAI Voice Agent's 56.4 (C) for voice agents. Prices, MCP, x402, uptime and agent notes side by side.

- Full: https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-assemblyai-voice-agent.md (~6,250 tokens) · this version ~3,430 tokens · JSON https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-assemblyai-voice-agent.json · canonical https://www.anchorterminal.com/compare/amazon-nova-sonic-vs-assemblyai-voice-agent
- Index: https://www.anchorterminal.com/llms.txt · API: https://www.anchorterminal.com/api/v1/index.json · MCP: https://www.anchorterminal.com/mcp · Updated: 2026-11-07
- Licence: CC BY 4.0, credit Anchor Terminal and link this page (https://www.anchorterminal.com/terms/#data)

Amazon Nova 2 Sonic scores 67.6 (B) on agent readiness against AssemblyAI Voice Agent API's 56.4 (C), and leads in 4 of 7 scored categories. AssemblyAI Voice Agent API leads on schema & documentation, agent ergonomics and maintenance & community. Both do voice agents.

- Amazon Nova 2 Sonic: B 67.6, rank #314 of 1486 · https://www.anchorterminal.com/tools/amazon-nova-sonic.min.md
- AssemblyAI Voice Agent API: C 56.4, rank #822 of 1486 · https://www.anchorterminal.com/tools/assemblyai-voice-agent.min.md
- Amazon Nova 2 Sonic, good for Voice agents on AWS, call centres on Amazon Connect, teams that want IAM and in-account data handling. Ahead on Reliability, 95 against 65; Security & auth, 77 against 55; Payments & pricing, 10 against 0; Transparency & trust, 79 against 68. Also No incidents deducted, where AssemblyAI Voice Agent API loses 3 points for them.
- AssemblyAI Voice Agent API, good for A developer who wants one managed pipeline at a flat rate and is content with AssemblyAI's own speech models and voices, with an optional model of their own. Ahead on Schema & documentation, 83 against 75; Agent ergonomics, 72 against 64; Maintenance & community, 64 against 50. Also A hosted endpoint, with nothing to install.

| Category | Amazon Nova 2 Sonic | AssemblyAI Voice Agent API |
| --- | --- | --- |
| Reliability (16%) | 95 | 65 |
| Performance (10%) | pending | pending |
| Schema & documentation (13%) | 75 | 83 |
| Agent ergonomics (13%) | 64 | 72 |
| Security & auth (14%) | 77 | 55 |
| Payments & pricing (10%) | 10 | 0 |
| Task success (10%) | pending | pending |
| Maintenance & community (7%) | 50 | 64 |
| Transparency & trust (7%) | 79 | 68 |

| Fact (where they differ) | Amazon Nova 2 Sonic | AssemblyAI Voice Agent API |
| --- | --- | --- |
| Vendor | Amazon Web Services | AssemblyAI, Inc. |
| Hosted endpoint | no (local only) | `wss://agents.assemblyai.com/v1/ws` |
| Licence | none | Proprietary service under AssemblyAI's Terms of Service. The two starter repositories on GitHub carry no licence file |
| Tools exposed | 0 | none |
| Last release | 2026-05-28 | 2026-09-16 |
| Terms last updated | 2026-10-01 | 2026-07-01 |
| Privacy policy last updated | 2026-05-18 | 2026-05-26 |
| Terms or service can change without notice | yes | not found in the text |
| Agent reviews | none | 3.5/5 (4) |

Why the edge:
- Reliability, Amazon Nova 2 Sonic +30: 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.); AssemblyAI Voice Agent API 65 (Scored with the hosted lines. Statuspage at status.assemblyai.com with component history, read from history.atom on 2 November, but its components are the Asynchronous API, Streaming API and LLM Gateway and none is the Voice Agent API (15 of 20). Thirteen incidents from 4 August to 2 November 2026 (14 August to 28 October) and none names the Voice Agent API. Four touch the realtime speech-to-text it runs on, all partial. New EU streaming sessions were refused for 12 minutes on 19 August, with 30 minutes of added latency on the US endpoint on 25 August, two hours of rejected Universal-3.6 Pro Realtime sessions on the US endpoint on 6 October (the EU endpoint unaffected), and some Real-time sessions failing with 502 after a temporary-token change on 28 October until it was rolled back. Whether agent sessions were affected isn't stated. Read as minor incidents touching the product, as assemblyai-stt reads the same feed (20, was 15, which isn't a checklist value). A per-account concurrent-session limit is enforced and no figure is published for it (0 of 15). The events reference (re-read on 2 November) names `at_capacity`, `concurrency_exceeded` and `internal_error` as the only retryable codes and says to reconnect with backoff, and sessions resume for 30 seconds. Webhooks carry a stable `event_id`. No idempotency key on `POST /v1/agents` (10 of 15). A Service Level Agreement of 99.9 per cent a month with credits, written against an Order Form, per the 9 October check (10). No beta label on the Voice Agent pages (10). 15+20+0+10+10+10 = 65.)
- Security & auth, Amazon Nova 2 Sonic +22: 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.); AssemblyAI Voice Agent API 55 (Plain API keys per project, created and deleted in the dashboard, with no scopes or expiry found (20 of 30). Browser clients pass a token in the `token` query parameter. We took no deduction because the token is one-time and redeemable for at most 600 seconds, which is a judgement call, as for assemblyai-stt. A read-only Reader role exists for dashboard members but not for keys. HTTP tool header values are write-only and encrypted at rest, tool calls go only to public `https` hosts with redirects refused, and the docs show how to gate tools by conversation state. No built-in confirmation step before a tool that writes (10 of 20). Caller speech and tool results reach a model. Tool arguments are drawn only from user turns and tool results since 26 August 2026 and tool responses are capped, but no prompt-injection guidance was found (8 of 15). Sessions keep a timeline with tool calls, webhook deliveries are logged per session, usage is broken down by key, and the dashboard has activity logs (12 of 15). The security page states a SOC 2 Type 2 report (per the 9 October check, not re-read on 2 November), the trust centre is on app.vanta.com, whose robots.txt disallows every path, and no bug bounty, disclosure policy or public advisory was found. www.assemblyai.com's robots.txt closes `/.well-known`, so security.txt is unread. Read as assemblyai-stt on the same evidence, a SOC 2 claim with no disclosure route (5, was 12). 20+10+8+12+5 = 55.)
- Maintenance & community, AssemblyAI Voice Agent API +14: Amazon Nova 2 Sonic 50 (Read as a model. The newest dated change is the May 2026 refresh, completed on 28 May, 162 days before this check (10). No Sonic release note or document history entry in the 90 days from 8 August. The pre-alpha Python SDK shipped 0.9.0, 0.10.0, 0.11.0 and 0.12.0 in the window, counted half (10 of 20). Release notes, document history, re:Post and AWS Support (10 of 15). The JavaScript Bedrock runtime client is current at 3.1163.0, while the Python route is pre-alpha (10 of 15). The SDKs ship on AWS's release train; CI not read (10). Total 50.); AssemblyAI Voice Agent API 64 (The last changelog entry tagged Voice Agent API is Pre-Connect Requests on 16 September 2026 (47 days before 2 November), which the 9 October check didn't count (20). Five tagged entries since 4 August (18 August, three on 26 August, 16 September) (20). A public changelog that records fixes, a support address and a Discord link we did not test (11 of 15 for a closed service). The Python and Node SDKs still have no Voice Agent client (Node 4.42.0 of 26 October added text-to-speech clients), and the two starter repositories were last changed on 16 August 2026 (8 of 15). The starters need no dependencies and have no licence file, tests or CI (5 of 10). 20+20+11+8+5 = 64.)
- Transparency & trust, Amazon Nova 2 Sonic +11: 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.); AssemblyAI Voice Agent API 68 (A closed service with a clear service agreement. The starter repositories have no licence file (15 of 30). The Terms of Service grant a licence to train on Customer Data by default, the opt-out needs a paid plan, and the retention page gives periods for streaming, sync, dictation, asynchronous and LLM Gateway data but none for Voice Agent sessions, which are recorded and stored. A DPA is published and the privacy policy states Data Privacy Framework certification (14 of 30). The changelog dates deprecations ahead of time, such as the 11 July 2026 notice of a change on 7 August, and the terms promise reasonable prior notice of major changes. No written deprecation policy was found (12 of 20). The subprocessor list at /legal/subprocessors redirects to a Vanta trust centre whose robots.txt disallows every path, so it is unread. US and EU endpoints are mentioned, with no EU host named for the Voice Agent API in the pages read (10 of 20). 15+14+12+10 = 51.)
- Payments & pricing, Amazon Nova 2 Sonic +10: 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.); AssemblyAI Voice Agent API 0 (No x402, MPP or L402 (0 of 40). On 2 November the pricing page lists speech-to-text, dictation, text-to-speech and LLM Gateway prices but no Voice Agent API price, and the billing docs have no Voice Agent section. The $4.50 an hour rate the 9 October check read on both is no longer published, and no other price page was found (0, was 20). The billing docs now say new accounts' $50 of credit applies to pre-recorded and real-time speech-to-text, Speech Understanding and Guardrails, without naming the Voice Agent API, where on 9 October they said it was covered (0, was 20). A person has to sign up in a browser to get the first key, and no key-creation API was found (0). 0+0+0+0 = 0.)
- Schema & documentation, AssemblyAI Voice Agent API +8: 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.); AssemblyAI Voice Agent API 83 (An AsyncAPI 3.0 file describes the socket and an OpenAPI 3.0.3 file the token endpoint. No description file was found for the agents, sessions and webhook REST endpoints, and the AsyncAPI file lacks `language_codes`, `voice_focus`, `transcript.agent.delta` and `is_error`, which the docs added on 23 July 2026 (19 of 25). llms.txt, a Markdown copy of each page and a docs MCP server (10). Operations and fields say what they are for and when to use them, such as when to choose `hold` over `interactive` execution (17 of 20). Enums, ranges and defaults on audio encoding, turn detection and timeouts. Tool `parameters` are a JSON Schema the server does not validate at `session.update` (12 of 15). Examples in cURL, Python and JavaScript, and tables of session error codes with close codes (13 of 15). A dated public changelog tagged by product and a `/v1` path, with no written versioning policy found (12 of 15).)