Claude Fable 5 vs Claude Sonnet 5.5 (Adaptive Reasoning, Low Effort, Default Fallback)
Wins 4 of 5 areas
Coding · Agents · Reasoning · Long documents
Wins 0 of 5 areas
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Claude Fable 5 is the stronger all-rounder.Claude Sonnet 5.5 (Adaptive Reasoning, Low Effort, Default Fallback) 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
- CodingWriting and fixing software10Claude Fable 51 of 1 test
- Long documentsFinding answers in very long texts10Claude Fable 51 of 1 test
- FactsGetting facts right instead of making them up11Even1 each
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.
Claude Sonnet 5.5 (Adaptive Reasoning, Low Effort, Default Fallback) costs 80% 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
- Real work tasks from 44 professionsGDPVal+21.7points ahead
- Complex command-line tasks across many fieldsTerminal-Bench 4.0+21.7points ahead
- Very hard expert questions across many subjectsHumanity's Last Exam+19.3points ahead
Where Claude Sonnet 5.5 (Adaptive Reasoning, Low Effort, Default Fallback) pulls ahead
- Avoids making up answers it doesn't knowAA-Omniscience · Non-hallucination+13.4points ahead
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 21.755.633.9+21.7
- Terminal-Bench 4.0Claude Fable 5 by 21.742.420.7+21.7
ReasoningClaude Fable 5
- Humanity's Last ExamClaude Fable 5 by 19.355.536.2+19.3
- CritPtClaude Fable 5 by 17.228.611.4+17.2
FactsEven
- AA-Omniscience · AccuracyClaude Fable 5 by 19.165.346.3+19.1
- AA-Omniscience · Non-hallucinationClaude Sonnet 5.5 (Adaptive Reasoning, Low Effort, Default Fallback) by 13.436.449.8+13.4
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 23.943.319.4+23.9
- AA IntelligenceClaude Fable 5 by 13.749.635.9+13.7
Questions people ask
Which is better, Claude Fable 5 or Claude Sonnet 5.5 (Adaptive Reasoning, Low Effort, Default Fallback)?
Claude Fable 5 wins four of the five areas where both have results: coding, agents, reasoning and long documents. Claude Sonnet 5.5 (Adaptive Reasoning, Low Effort, Default Fallback) wins none, but costs 80% less. They are level on facts.
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; Claude Sonnet 5.5 (Adaptive Reasoning, Low Effort, Default Fallback) costs $2.00 and $10.00. That makes Claude Sonnet 5.5 (Adaptive Reasoning, Low Effort, Default Fallback) about 80% 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.