Claude Fable 5 vs GPT-5.5

The frontier matchup of mid-2026: Anthropic's brand-new Fable 5 against OpenAI's GPT-5.5. Both top their vendors' lineups; here is how they actually compare on the boards and the bill.

The verdict

Claude Fable 5 is the most capable coding model we track, full stop: 72.9% on CursorBench 3.1 at max effort and 64.9 on the Artificial Analysis Intelligence Index, both the best results on our boards. GPT-5.5 sits at 64.3% and 58.9 respectively.

GPT-5.5 answers back on price: $5 per million input tokens versus Fable 5's $10, and $30 output versus $50. For high-volume agent work that gap compounds fast, and GPT-5.5's token efficiency is strong.

The practical split: Fable 5 when the task is hard enough that failure costs more than tokens; GPT-5.5 as the high-end workhorse. Both carry 1M token context windows, so neither wins on fitting your codebase.

The facts, side by side
ClaudeClaude Fable 5OpenAIGPT-5.5
ProviderAnthropicOpenAI
Input price$10/M / 1M tokens$5/M / 1M tokens
Output price$50/M / 1M tokens$30/M / 1M tokens
Context1M tokens1.1M tokens
Open weightsNoNo
Free tierNoNo
ReleasedJun 2026Apr 2026

Prices and context are synced from live provider listings. Deep dives: Claude Fable 5 and GPT-5.5.

Benchmark scores
Claude Fable 5GPT-5.5
SWE-bench Verified95% (Vendor harness)88.7% (Vendor harness)
BrowseComp86.9% (Single agent, web search)84.4% (Browsing)
OSWorld-Verified85% (Vendor harness)78.7% (Vendor harness)
CursorBench 3.172.9% (Max)64.3% (Extra High)
Artificial Analysis Intelligence Index64.9 (Adaptive Reasoning, Max Effort, Opus 4.8 Fallback)60.2 (xhigh)
FrontierCode Main46.3%25.5%
Tau2-Bench Telecom—98%
Terminal-Bench 2.0—84.7% (NexAU-AHE)
DeepSWE—70% (Extra High)
GAIA2—56.4% (xHigh, ReAct baseline)
FrontierCode Diamond—6.3%

Best published configuration per model. Every config and source is on the benchmark leaderboards.

Benchmarks, head to head

Every published configuration for Claude Fable 5 and GPT-5.5 on the benchmarks they share, charted side by side. Only these two models are plotted.

SWE-bench Verified

The most-cited agentic coding benchmark: can a model fix a real GitHub issue in a real repository? 500 human-validated tasks, scored by the repo's own tests. Higher is better.

CursorBench 3.1

Ambiguous, multi-file tasks from real Cursor sessions that test codebase understanding, bugfinding, planning, and code review.

FrontierCode Main

Cognition's test of whether a model writes code maintainers would actually merge, not just code that passes tests. Main is the 100 hardest of 150 tasks. Higher is better.

OSWorld-Verified

The standard computer-use benchmark: agents complete real desktop tasks in a live Ubuntu VM from screenshots, mouse and keyboard, scored by execution-based checks. Higher is better.

BrowseComp

OpenAI's hard web-browsing benchmark: 1,266 questions whose answers are hard to find but easy to verify, requiring persistent multi-step browsing. Higher is better.

Artificial Analysis Intelligence Index

The most-cited composite intelligence score: a 0–100 index combining knowledge, reasoning, math, coding, and agentic evaluations (GPQA Diamond, HLE, IFBench, SciCode, Terminal-Bench Hard, τ²-Bench, and more). Higher is better.

Frequently asked questions
Is Claude Fable 5 better than GPT-5.5?

On the benchmarks we track, yes: Fable 5 leads CursorBench 3.1 (72.9% versus 64.3% at each model's best effort setting) and the Artificial Analysis Intelligence Index (64.9 versus 58.9). GPT-5.5 counters on price at half the per-token cost, so the right pick depends on how hard your tasks are.

Is Claude Fable 5 worth double the price of GPT-5.5?

For hard, multi-step engineering where a failed run wastes an hour, usually yes: the capability gap is the largest at the top of our boards. For everyday coding, GPT-5.5 (or cheaper models like GPT-5.4 and Claude Sonnet 4.6) deliver most of the value at a fraction of the cost. Route by task difficulty rather than picking one.

Which agents can use Fable 5 and GPT-5.5?

Fable 5 runs in Claude Code natively and anywhere the Anthropic API plugs in, including Hermes and OpenClaw. GPT-5.5 runs in Codex on a ChatGPT plan, and through the OpenAI API or OpenRouter in other agents. Our best-models rankings per agent show current recommendations.

More comparisons

Claude Opus 4.8 vs GPT-5.5

The price-matched flagship fight: Claude Opus 4.8 and GPT-5.5 both cost $5 per million input tokens, which makes this the rare comparison where capability is the only question.
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