$ diff k2-horizon claude-fable-5-1
K2 Horizon vs Claude Fable 5.1
Values come from K2 Horizon and Claude Fable 5.1, 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.
IfmK2 Horizon
- context
- 524K
- weights
- open
- $/M in
- —
- $/M out
- —
- context
- 1M
- weights
- closed
- $/M in
- $10
- $/M out
- $50
What actually differs
- Context window
- Claude Fable 5.1 takes 1M against 524K — modestly more room in a single request.
- Weights
- K2 Horizon publishes weights (Apache 2.0 (weights and code)); Claude Fable 5.1 is API-only. That decides self-hosting, air-gapped deployment and fine-tuning before any capability question does.
- Recency
- K2 Horizon shipped 2 days after Claude Fable 5.1 (2026-09-03 vs 2026-09-01).
Full spec
| Attribute | K2 Horizon | Claude Fable 5.1 |
|---|---|---|
| Developer | Ifm | Anthropic |
| Released | 2026-09-03 | 2026-09-01 |
| Context window | 524,288 (flagship 375B-A23B, native from midtraining onward) | 1M tokens |
| Pricing | not recorded | $10/M input · $50/M output · cache reads $0.25/M |
| License | Apache 2.0 (weights and code) | proprietary (API-only; no weight release) |
| Availability | Hugging Face (weights, code, checkpoints, training data where redistributable) | Claude API as `claude-fable-5-1`; plan-tier access is disputed — see `## Conflicting Reports` |