Claude Fable 5.1 vs K2-Horizon-0.9B
Wins 5 of 5 areas
Coding · Agents · Reasoning · Facts · Long documents
Wins 0 of 5 areas
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Claude Fable 5.1 is the stronger all-rounder.
Scores updated · 12 tests both models report · How we compare
Where each one wins
Tests won in each of the five areas where both have results. Each piece is one test, so a longer bar means more evidence; grey means the two scored within a point of each other.
- AgentsCarrying out multi-step tasks on its own30Claude Fable 5.13 of 3 tests
- ReasoningHard problems that need careful thinking30Claude Fable 5.13 of 3 tests
- FactsGetting facts right instead of making them up20Claude Fable 5.12 of 2 tests
- CodingWriting and fixing software10Claude Fable 5.11 of 1 test
- Long documentsFinding answers in very long texts10Claude Fable 5.11 of 1 test
Coding and long documents rest on a single test each.
What it costs
Prices per million tokens, roughly 750,000 words. The bars show the cost of a million tokens read plus a million written.
The biggest differences
The tests each model wins by the widest margin, up to three each. Scores are out of 100.
Where Claude Fable 5.1 pulls ahead
- Reasons across sets of long documentsAA-LCR+79points ahead
- Graduate-level biology, physics and chemistry questionsGPQA Diamond+64.4points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+60.3points ahead
Where K2-Horizon-0.9B pulls ahead
No clear win on a test scored out of 100.
Every test, side by side
All 12 tests both models report. The winning score is in its model's colour; marks a score checked independently.
AgentsClaude Fable 5.1
- GDPValClaude Fable 5.1 by 62.862.80+62.8
- Terminal-Bench 4.0Claude Fable 5.1 by 52520+52
- τ-Bench V3 · BankingClaude Fable 5.1 by 42.347.24.9+42.3
ReasoningClaude Fable 5.1
- GPQA DiamondClaude Fable 5.1 by 64.493.729.3+64.4
- Humanity's Last ExamClaude Fable 5.1 by 53.759.15.4+53.7
- CritPtClaude Fable 5.1 by 29.729.70+29.7
FactsClaude Fable 5.1
- AA-Omniscience · AccuracyClaude Fable 5.1 by 60.367.26.9+60.3
- AA-Omniscience · Non-hallucinationClaude Fable 5.1 by 13.127.414.3+13.1
Other results2 tests, not counted
Tests outside the eight areas. They are not counted above: several are summary scores built from other tests, or the same test under another name.
- AA-OmniscienceClaude Fable 5.1 by 116.343.5-72.8+116.3
- AA IntelligenceClaude Fable 5.1 by 50.453.43+50.4
Questions people ask
Which is better, Claude Fable 5.1 or K2-Horizon-0.9B?
Claude Fable 5.1 wins all five areas where both have results: coding, agents, reasoning, facts and long documents. K2-Horizon-0.9B wins none.
Which is better for coding?
Claude Fable 5.1. It wins the one coding test both models report.
How do you compare the two?
We use the 12 benchmark tests both models have published scores on. The verdict counts the 10 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 2 are listed but not counted, because several are summary scores or repeat a test. Each score is the one shown on the model's own page.