$ diff claude-sonnet-5-5 k2-horizon
Claude Sonnet 5.5 vs K2 Horizon
Values come from Claude Sonnet 5.5 and K2 Horizon, where each is cited to its source. This page states no benchmark result and ranks neither model — it puts two published specifications next to each other. Where a lab has not published a figure, the row says so rather than guessing.
AnthropicClaude Sonnet 5.5
- context
- 1M
- weights
- closed
- $/M in
- $2
- $/M out
- $10
- context
- 524K
- weights
- open
- $/M in
- —
- $/M out
- —
What actually differs
- Context window
- Claude Sonnet 5.5 takes 1M against 524K — modestly more room in a single request.
- Weights
- K2 Horizon publishes weights (Apache 2.0 (weights and code)); Claude Sonnet 5.5 is API-only. That decides self-hosting, air-gapped deployment and fine-tuning before any capability question does.
- Recency
- Claude Sonnet 5.5 shipped 25 days after K2 Horizon (2026-09-28 vs 2026-09-03).
Full spec
| Attribute | Claude Sonnet 5.5 | K2 Horizon |
|---|---|---|
| Developer | Anthropic | Ifm |
| Released | 2026-09-28 | 2026-09-03 |
| Context window | 1M tokens | 524,288 (flagship 375B-A23B, native from midtraining onward) |
| Pricing | $2/M input · $10/M output · cache reads 10% of base input | not recorded |
| License | proprietary (API-only; no weight release) | Apache 2.0 (weights and code) |
| Availability | Claude apps, Claude API as `claude-sonnet-5-5`, Amazon Bedrock, Google Cloud Vertex AI, Microsoft Foundry, Claude Platform on AWS | Hugging Face (weights, code, checkpoints, training data where redistributable) |