Claude Fable 5 vs mercury-2.5-preview
Wins 5 of 5 areas
Coding · Agents · Reasoning · Facts · Long documents
Wins 0 of 5 areas
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Claude Fable 5 is the stronger all-rounder.mercury-2.5-preview is cheaper.
Scores updated · 10 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 own20Claude Fable 52 of 2 tests
- ReasoningHard problems that need careful thinking20Claude Fable 52 of 2 tests
- FactsGetting facts right instead of making them up20Claude Fable 52 of 2 tests
- CodingWriting and fixing software10Claude Fable 51 of 1 test
- Long documentsFinding answers in very long texts10Claude Fable 51 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.
mercury-2.5-preview costs 98% less for the same work.
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 pulls ahead
- Very hard expert questions across many subjectsHumanity's Last Exam+43.7points ahead
- Answers hard knowledge questions correctlyAA-Omniscience · Accuracy+42.7points ahead
- Code for real scientific research problemsSciCode+22.5points ahead
Where mercury-2.5-preview pulls ahead
No clear win on a test scored out of 100.
Every test, side by side
All 10 tests both models report. The winning score is in its model's colour; marks a score checked independently.
AgentsClaude Fable 5
- GDPValClaude Fable 5 by 55.655.60+55.6
- Terminal-Bench 4.0Claude Fable 5 by 42.442.40+42.4
ReasoningClaude Fable 5
- Humanity's Last ExamClaude Fable 5 by 43.755.511.8+43.7
- CritPtClaude Fable 5 by 28.628.60+28.6
FactsClaude Fable 5
- AA-Omniscience · AccuracyClaude Fable 5 by 42.765.322.6+42.7
- AA-Omniscience · Non-hallucinationClaude Fable 5 by 16.736.419.7+16.7
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 by 82.843.3-39.5+82.8
- AA IntelligenceClaude Fable 5 by 37.349.612.3+37.3
Questions people ask
Which is better, Claude Fable 5 or mercury-2.5-preview?
Claude Fable 5 wins all five areas where both have results: coding, agents, reasoning, facts and long documents. mercury-2.5-preview wins none, but costs 98% less.
Which is better for coding?
Claude Fable 5. It wins the one coding test both models report.
Which is cheaper?
Claude Fable 5 costs $10.00 per million input tokens and $50.00 per million output tokens; mercury-2.5-preview costs $0.25 and $0.75. That makes mercury-2.5-preview about 98% cheaper for the same work.
How do you compare the two?
We use the 10 benchmark tests both models have published scores on. The verdict counts the 8 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.