As of: 2026-11-13 13:49 CET.
Researched and written by AI agents (Claude Opus 5.5 in Claude Code), with a human editor. How we work: https://postcutoff.com/about/
Canonical page: https://postcutoff.com/m/claude-sonnet-5-5/

# Claude Sonnet 5.5

Anthropic, Claude 5 family. Status: current. Type: reasoning model. Released: 2026-09-28. Training cutoff: 2026-06.

## How to call it

| Provider | Model id | Endpoint | Docs |
|---|---|---|---|
| Anthropic API (Claude API) | `claude-sonnet-5-5` | https://api.anthropic.com/v1/messages | https://platform.claude.com/docs/en/models/sonnet-5-5/overview |
| AWS Bedrock (Messages API / Mantle) | `anthropic.claude-sonnet-5-5` |  | https://platform.claude.com/docs/en/build-with-claude/claude-in-amazon-bedrock |
| Google Cloud Vertex AI | `claude-sonnet-5-5` |  | https://platform.claude.com/docs/en/build-with-claude/claude-on-vertex-ai |
| Microsoft Foundry (Azure) | `claude-sonnet-5-5` |  | https://platform.claude.com/docs/en/build-with-claude/claude-in-microsoft-foundry |
| Claude Platform on AWS | `claude-sonnet-5-5` |  | https://platform.claude.com/docs/en/build-with-claude/claude-platform-on-aws |
| OpenRouter | `anthropic/claude-sonnet-5.5` |  | https://openrouter.ai/anthropic/claude-sonnet-5.5 |
| Web app |  |  | https://claude.ai |

## Pricing

- Input: $2 per 1M tokens
- Output: $10 per 1M tokens
- Cache read: $0.10 per 1M tokens
- Unit as published: per 1M tokens (USD); Batch API 50% off
- Source: https://platform.claude.com/docs/en/about-claude/pricing
- Last checked: 2026-10-08

## Specs

- Input: text, image, pdf
- Output: text
- Context window: 1,000,000 tokens
- Max output: 128,000 tokens
- Open weights: no
- Licence: proprietary

## What it has not seen

- Published training cutoff: 2026-06 (June 2026).
- AI events after it on Post-Cutoff: 1,795 (409 major, 81 historic), as of 2026-11-13.
- Already missing at launch: 470.
- Briefings of the news since June 2026: https://postcutoff.com/briefings/cutoff-2026-06-s.md (short), https://postcutoff.com/briefings/cutoff-2026-06-m.md (medium), https://postcutoff.com/briefings/cutoff-2026-06.md (full).
- Its card, with five things it has never heard of: https://postcutoff.com/you/claude-sonnet-5-5/
- In our own test, asked without tools, Claude Sonnet 5.5 placed its knowledge far before its published June 2026 cutoff (case 021). https://postcutoff.com/why/021-claude-5x-effective-cutoff-far-before-published/

## What stands out

- Opus-level knowledge work at Sonnet price: Scores nearly level with Opus 5.5 on GDPval-AA (1844 vs 1846 Elo), at $2/$10 per MTok. Source: https://www.anthropic.com/claude-sonnet-5-5
- Large agentic-coding jump: Anthropic reports 70.6% on Terminal-Bench 4.0, up from 10.3% for Sonnet 5, and up to 30% lower cost per task. Source: https://www.anthropic.com/claude-sonnet-5-5
- Beat Pokemon Red from screenshots (first): Anthropic says it is the first Sonnet model to finish Pokemon Red using only screenshots. Source: https://www.anthropic.com/claude-sonnet-5-5
- between_tools thinking mode (first): New thinking type that turns off up-front thinking while still reasoning between tool calls; it replaces thinking: disabled. Source: https://platform.claude.com/docs/en/models/sonnet-5-5/overview
- Token efficiency: A Balyasny test used 121k tokens per task, versus 497k for Sonnet 5. Source: https://www.anthropic.com/claude-sonnet-5-5

## Notes

Best speed/intelligence balance. Adaptive thinking on by default (effort default high); thinking {type: disabled} returns 400, use {type: between_tools} at effort high or below; forced tool_choice any/tool returns 400; non-default temperature/top_p/top_k return 400. Batch $1/$5. Cache-read price cut from $0.20 to $0.10 per MTok on Oct 7, 2026 (5% of base input).

Everyday coding, agents and enterprise workloads at Sonnet pricing; successor to Claude Sonnet 5 at the same price.

```bash
curl https://api.anthropic.com/v1/messages \
 -H "x-api-key: $ANTHROPIC_API_KEY" -H "anthropic-version: 2023-06-01" -H "content-type: application/json" \
 -d '{"model":"claude-sonnet-5-5","max_tokens":16000,"messages":[{"role":"user","content":"Hello"}]}'
```

Sources:
- Model page: https://platform.claude.com/docs/en/models/sonnet-5-5/overview
- Announcement: https://www.anthropic.com/claude-sonnet-5-5
- Pricing: https://platform.claude.com/docs/en/about-claude/pricing
- Models overview: https://platform.claude.com/docs/en/about-claude/models/overview
- Deprecations: https://platform.claude.com/docs/en/about-claude/model-deprecations

Model page: https://postcutoff.com/m/claude-sonnet-5-5/