Claude Sonnet 4 vs K2 Think V2
Wins 5 of 6 areas
Coding · Agents · Reasoning · Facts · Long documents
Wins 1 of 6 areas
Following instructions
Claude Sonnet 4 is the stronger all-rounder.K2 Think V2 is better at following instructions.
Scores updated · 17 tests both models report · How we compare
Where each one wins
Tests won in each of the six 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.
- CodingWriting and fixing software30Claude Sonnet 43 of 3 tests
- AgentsCarrying out multi-step tasks on its own20Claude Sonnet 42 of 2 tests
- FactsGetting facts right instead of making them up20Claude Sonnet 42 of 2 tests
- ReasoningHard problems that need careful thinking10Claude Sonnet 41 of 3 tests · 2 ties
- Long documentsFinding answers in very long texts10Claude Sonnet 41 of 1 test
- Following instructionsDoing exactly what it is asked01K2 Think V21 of 1 test
Long documents and following instructions 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 Sonnet 4 pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+42.1points ahead
- Hard command-line tasks in a real terminalTerminal-Bench Hard+24.3points ahead
- Command-line tasks in a real terminalTerminal-Bench 2.1+21.3points ahead
Where K2 Think V2 pulls ahead
- Follows unfamiliar, precisely checkable instructionsIFBench+8.1points ahead
Every test, side by side
All 17 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Sonnet 4
- Terminal-Bench HardClaude Sonnet 4 by 24.331.16.8+24.3
- Terminal-Bench 2.1Claude Sonnet 4 by 21.336.315+21.3
- SciCodeClaude Sonnet 4 by 74033+7
AgentsClaude Sonnet 4
- τ-Bench V3 · BankingClaude Sonnet 4 by 11.316.75.4+11.3
- GDPValClaude Sonnet 4 by 9.79.70+9.7
ReasoningClaude Sonnet 4
- GPQA DiamondClaude Sonnet 4 by 6.477.771.3+6.4
- Humanity's Last Examtie10.710.1tie
- CritPttie0.30tie
FactsClaude Sonnet 4
- AA-Omniscience · Non-hallucinationClaude Sonnet 4 by 42.170.928.8+42.1
- AA-Omniscience · AccuracyClaude Sonnet 4 by 4.722.718+4.7
Following instructionsK2 Think V2
- IFBenchK2 Think V2 by 8.154.762.8+8.1
Other results5 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 Sonnet 4 by 40.50.2-40.3+40.5
- τ²-Bench Telecom (AA run)Claude Sonnet 4 by 39.264.625.4+39.2
- Artificial Analysis Coding IndexClaude Sonnet 4 by 16.637.621+16.6
- AA Agentic IndexClaude Sonnet 4 by 15.817.61.8+15.8
- AA IntelligenceClaude Sonnet 4 by 7.418.911.5+7.4
Questions people ask
Which is better, Claude Sonnet 4 or K2 Think V2?
Claude Sonnet 4 wins five of the six areas where both have results: coding, agents, reasoning, facts and long documents. K2 Think V2 wins following instructions.
Which is better for coding?
Claude Sonnet 4. It wins 3 of the 3 coding tests both models report; K2 Think V2 wins none.
How do you compare the two?
We use the 17 benchmark tests both models have published scores on. The verdict counts the 12 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 5 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.