Claude Fable 5 vs GPT-5.5 Instant
Wins 7 of 8 areas
Coding · Agents · Reasoning · Facts · Images and charts · Math · Long documents
Wins 1 of 8 areas
Following instructions
Claude Fable 5 is the stronger all-rounder.GPT-5.5 Instant is cheaper and better at following instructions.
Scores updated · 24 tests both models report · How we compare
Where each one wins
Tests won in each of the eight areas we test. 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 Fable 53 of 3 tests
- AgentsCarrying out multi-step tasks on its own30Claude Fable 53 of 3 tests
- ReasoningHard problems that need careful thinking30Claude Fable 53 of 3 tests
- FactsGetting facts right instead of making them up30Claude Fable 53 of 3 tests
- Images and chartsUnderstanding pictures, charts and video20Claude Fable 52 of 2 tests
- MathCompetition and research-level math20Claude Fable 52 of 2 tests
- Long documentsFinding answers in very long texts10Claude Fable 51 of 1 test
- Following instructionsDoing exactly what it is asked01GPT-5.5 Instant1 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.
GPT-5.5 Instant costs 42% 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
- Extremely hard research-level math problemsFrontierMath Tier 4+87.8points ahead
- Unpublished advanced math problemsFrontierMath Tiers 1-3 (v2)+60.7points ahead
- Command-line tasks in a real terminalTerminal-Bench 2.1+49.8points ahead
Where GPT-5.5 Instant pulls ahead
- Follows unfamiliar, precisely checkable instructionsIFBench+8points ahead
Every test, side by side
All 24 tests both models report. The winning score is in its model's colour; marks a score checked independently.
CodingClaude Fable 5
- Terminal-Bench 2.1Claude Fable 5 by 49.884.634.8+49.8
- Terminal-Bench HardClaude Fable 5 by 20.562.942.4+20.5
- SciCodeClaude Fable 5 by 8.56152.5+8.5
AgentsClaude Fable 5
- GDPValClaude Fable 5 by 55.655.60+55.6
- Terminal-Bench 4.0Claude Fable 5 by 29.842.412.6+29.8
- τ-Bench V3 · BankingClaude Fable 5 by 26.338.111.8+26.3
ReasoningClaude Fable 5
- Humanity's Last ExamClaude Fable 5 by 33.955.521.6+33.9
- CritPtClaude Fable 5 by 2628.62.6+26
- GPQA DiamondClaude Fable 5 by 892.684.6+8
FactsClaude Fable 5
- SimpleQA VerifiedClaude Fable 5 by 32.770.738+32.7
- AA-Omniscience · AccuracyClaude Fable 5 by 19.165.346.3+19.1
- AA-Omniscience · Non-hallucinationClaude Fable 5 by 1.736.434.7+1.7
Images and chartsClaude Fable 5
- MMMU-ProClaude Fable 5 by 8.284.276+8.2
- LMArena · VisionClaude Fable 5 by 75 rating points13251250+75 rating
MathClaude Fable 5
- FrontierMath Tier 4Claude Fable 5 by 87.890.22.4+87.8
- FrontierMath Tiers 1-3 (v2)Claude Fable 5 by 60.78726.3+60.7
Following instructionsGPT-5.5 Instant
- IFBenchGPT-5.5 Instant by 863.571.5+8
Other results6 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.
- τ²-Bench Telecom (AA run)Claude Fable 5 by 49.198.549.4+49.1
- Artificial Analysis Coding IndexClaude Fable 5 by 37.176.539.4+37.1
- AA-OmniscienceClaude Fable 5 by 32.143.311.2+32.1
- AA Agentic IndexClaude Fable 5 by 31.85119.2+31.8
- HealthBench ProfessionalClaude Fable 5 by 27.66638.4+27.6
- AA IntelligenceClaude Fable 5 by 26.949.622.7+26.9
Questions people ask
Which is better, Claude Fable 5 or GPT-5.5 Instant?
Claude Fable 5 wins seven of the eight areas we test: coding, agents, reasoning, facts, images and charts, math and long documents. GPT-5.5 Instant wins following instructions, and costs 42% less.
Which is better for coding?
Claude Fable 5. It wins 3 of the 3 coding tests both models report; GPT-5.5 Instant wins none.
Which is cheaper?
Claude Fable 5 costs $10.00 per million input tokens and $50.00 per million output tokens; GPT-5.5 Instant costs $5.00 and $30.00. That makes GPT-5.5 Instant about 42% cheaper for the same work.
How do you compare the two?
We use the 24 benchmark tests both models have published scores on. The verdict counts the 18 tests in the eight capability areas, and a gap under one point (ten on rating-style scales) counts as a tie. The other 6 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.