Model comparison
Claude Fable 5 vs GPT-OSS 20B
Head-to-head evidence from 16 shared benchmark results across 6 categories. Overall scores shown here use the public BenchAlign v5 ranking lane.
Public leaderboard positions: Claude Fable 5 #2 (Supported); GPT-OSS 20B #159 (Supported). Intervals and evidence labels describe ranking uncertainty, not a guarantee for a specific workload.
Evidence parity. Claude Fable 5 and GPT-OSS 20B share 16 comparable benchmark results. 0 of 8 categories are comparable. 18 results are unique to Claude Fable 5; 2 to GPT-OSS 20B.
Updated July 23, 2026- Shared results
- 16
- Claude Fable 5 only
- 18
- GPT-OSS 20B only
- 2
- Comparable categories
- 0 / 8
Benchmark data for Claude Fable 5 and GPT-OSS 20B is coming soon on BenchLM.
Confidence note. This is a partial-evidence comparison with 16 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 is priced at $10.00 input / $50.00 output per 1M tokens, versus $0.00 input / $0.00 output per 1M tokens for GPT-OSS 20B. Claude Fable 5 has the larger context window at 1M+, compared with 128K for GPT-OSS 20B.
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-OSS 20B |
|---|---|---|---|
| Agentic | Claude Fable 584.6 | MarginNo overlap | GPT-OSS 20BNot measured |
| Coding | Claude Fable 589.2 | MarginNo overlap | GPT-OSS 20BNot measured |
| Multimodal | Claude Fable 557.9 | MarginNo overlap | GPT-OSS 20BNot measured |
Operational comparison
Runtime and commercial metrics are compared only when both models have a complete sourced value.
| Metric | Claude Fable 5 | GPT-OSS 20B | Comparison |
|---|---|---|---|
| Input / output priceUSD per 1M tokens | Claude Fable 5$10 input / $50 output | GPT-OSS 20B$0 input / $0 output | GPT-OSS 20B has the lower combined listed price. |
| Generation speedtokens per second | Claude Fable 5Not available | GPT-OSS 20B313 tok/s | A complete speed comparison is not available. |
| First-answer latencyseconds to first token | Claude Fable 5Not available | GPT-OSS 20B0.65 s | A complete latency comparison is not available. |
| Context windowmaximum listed tokens | Claude Fable 51M+ | GPT-OSS 20B128K | Claude Fable 5 lists the larger context window. |
Benchmark Deep Dive
Agentic14 benchmarks
| Benchmark | Claude Fable 5 | GPT-OSS 20B | Result |
|---|---|---|---|
| Terminal-Bench 2.0Source | 84.3% | — | Not comparable |
| OSWorld-VerifiedSource | 85% | — | Not comparable |
| GDPval-AASource | 1748 | 559 | Claude Fable 5 leads |
| AA Agentic IndexSource | 52.8% | 3.1% | Claude Fable 5 leads |
| τ²-bench resultsSource | 98.5% | 60.2% | Claude Fable 5 leads |
| GDPval-AASource | 62.4% | 3.0% | Claude Fable 5 leads |
| 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 |
| APEX-Agents-AASource | — | 0.7% | Not comparable |
Coding10 benchmarks
| Benchmark | Claude Fable 5 | GPT-OSS 20B | 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% | 20.7% | Claude Fable 5 leads |
| AA-SciCodeSource | 60.2% | 34.4% | Claude Fable 5 leads |
| React Native EvalsSource | — | 71% | Not comparable |
Reasoning2 benchmarks
Knowledge6 benchmarks
| Benchmark | Claude Fable 5 | GPT-OSS 20B | Result |
|---|---|---|---|
| Artificial Analysis Intelligence IndexSource | 59.9% | 14.9% | Claude Fable 5 leads |
| AA-GPQA DiamondSource | 92.6% | 68.8% | Claude Fable 5 leads |
| AA-HLESource | 53.3% | 9.8% | Claude Fable 5 leads |
| AA-Omniscience IndexSource | 40.2% | -63.9% | Claude Fable 5 leads |
| AA-Omniscience AccuracySource | 61.4% | 15.5% | Claude Fable 5 leads |
| AA-Omniscience Hallucination RateSource | 54.9% | 94.1% | Claude Fable 5 leads |
Multimodal3 benchmarks
Inst. Following1 benchmarks
| Benchmark | Claude Fable 5 | GPT-OSS 20B | Result |
|---|---|---|---|
| AA-IFBenchSource | 63.5% | 65.1% | GPT-OSS 20B leads |
Frequently Asked Questions (3)
Can I compare Claude Fable 5 and GPT-OSS 20B 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-OSS 20B today?
Claude Fable 5: $10.00 input / $50.00 output per 1M tokens GPT-OSS 20B: $0.00 input / $0.00 output per 1M tokens Both model pages still include creator, context window, reasoning mode, and other metadata while benchmark coverage fills in.
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