Model comparison
Claude Fable 5 vs GPT-5.1-Codex
Head-to-head evidence from 12 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude Fable 5 #3 (Supported); GPT-5.1-Codex #105 (Estimated). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Fable 5 and GPT-5.1-Codex share 12 comparable benchmark results. 0 of 8 categories are comparable. 22 results are unique to Claude Fable 5; 4 to GPT-5.1-Codex.
Updated July 24, 2026- Shared results
- 12
- Claude Fable 5 only
- 22
- GPT-5.1-Codex only
- 4
- Comparable categories
- 0 / 8
Benchmark data for Claude Fable 5 and GPT-5.1-Codex is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 12 shared benchmark results across 6 evidence categories; 0 of 8 categories currently have scoreable aggregates for both models. Treat the verdict as directional until coverage is more balanced.
Why this result
BenchLM has partial data for these models, but not enough overlapping benchmark coverage to produce a fair score-level comparison yet.
Claude Fable 5 has the larger context window at 1M+, compared with 400K for GPT-5.1-Codex.
Category breakdown
Exact category averages are shown below. Not measured means BenchLM does not have enough sourced public coverage for that model and category.
| Category | Claude Fable 5 | Δ | GPT-5.1-Codex |
|---|---|---|---|
| Agentic | Claude Fable 584.6 | MarginNo overlap | GPT-5.1-CodexNot measured |
| Coding | Claude Fable 589.2 | MarginNo overlap | GPT-5.1-CodexNot measured |
| Multimodal | Claude Fable 557.9 | MarginNo overlap | GPT-5.1-CodexNot measured |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Fable 5 | GPT-5.1-Codex | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Fable 5$10 input / $50 output | GPT-5.1-CodexNot available | A complete price comparison is not available. |
| Generation speedtokens per second | Claude Fable 5Not available | GPT-5.1-CodexNot available | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Fable 5Not available | GPT-5.1-CodexNot available | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Fable 51M+ | GPT-5.1-Codex400K | Claude Fable 5 lists the larger context window. |
Benchmark Deep Dive
Agentic15 benchmarks
| Benchmark | Claude Fable 5 | GPT-5.1-Codex | Result |
|---|---|---|---|
| Terminal-Bench 2.0Source | 84.3% | — | Not comparable |
| OSWorld-VerifiedSource | 85% | — | Not comparable |
| GDPval-AASource | 1747 | — | Not comparable |
| AA Agentic IndexSource | 52.8% | — | Not comparable |
| τ²-bench resultsSource | 98.5% | 83% | Claude Fable 5 leads |
| GDPval-AASource | 62.3% | — | Not comparable |
| AA BriefcaseSource | 1574 | — | Not comparable |
| AA AutomationBenchSource | 48.6% | — | Not comparable |
| AA EnterpriseOps-GymSource | 51.1% | — | Not comparable |
| AA Harvey LABSource | 93.6% | — | Not comparable |
| AA Tau3 BankingSource | 26.8% | — | Not comparable |
| terminalBenchHardSource | 62.9% | — | Not comparable |
| aaTerminalBench21Source | 84.6% | — | Not comparable |
| Gert LabsSource | — | 49.68% | Not comparable |
| JobBenchSource | — | 26.2% | Not comparable |
Coding10 benchmarks
| Benchmark | Claude Fable 5 | GPT-5.1-Codex | Result |
|---|---|---|---|
| SWE-bench VerifiedSource | 95% | — | Not comparable |
| SWE-bench ProSource | 80% | — | Not comparable |
| FrontierCode 1.1 MainSource | 53.5% | — | Not comparable |
| Terminal-Bench 2.0Source | 84.3% | — | Not comparable |
| cursorBench31Source | 70.6% | — | Not comparable |
| cursorBench32Source | 70.5% | — | Not comparable |
| VulcanBench v3Source | 87.0% | — | Not comparable |
| AA Coding IndexSource | 76.5% | — | Not comparable |
| AA-SciCodeSource | 60.2% | 40.2% | Claude Fable 5 leads |
| Vibe Code BenchSource | — | 13.12% | Not comparable |
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | Claude Fable 5 | GPT-5.1-Codex | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 59.9% | 34.7% | Claude Fable 5 leads |
| AA-GPQA DiamondSource | 92.6% | 86.0% | Claude Fable 5 leads |
| AA-HLESource | 53.3% | 23.4% | Claude Fable 5 leads |
| AA-Omniscience IndexSource | 40.2% | -6.0% | Claude Fable 5 leads |
| AA-Omniscience AccuracySource | 61.4% | 39.2% | Claude Fable 5 leads |
| AA-Omniscience Hallucination RateSource | 54.9% | 74.4% | Claude Fable 5 leads |
Multimodal4 benchmarks
Inst. Following1 benchmarks
| Benchmark | Claude Fable 5 | GPT-5.1-Codex | Result |
|---|---|---|---|
| AA-IFBenchSource | 63.5% | 70.0% | GPT-5.1-Codex leads |
Frequently Asked Questions (3)
Can I compare Claude Fable 5 and GPT-5.1-Codex on BenchLM yet?
Not fully yet. BenchLM is tracking both models, but the sourced benchmark breakdown for this comparison is still coming soon.
Why does this comparison show “coming soon”?
BenchLM only shows category winners and benchmark-level calls when we have sourced results that can be compared fairly. For these models, the public benchmark coverage is not complete enough yet.
What data is available for Claude Fable 5 and GPT-5.1-Codex today?
Claude Fable 5: $10.00 input / $50.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.