🆕 Updated June 9: Claude Fable 5 released — 80.3% SWE-bench Pro. The first Mythos-class model available to everyone. Now the definitive #1 for Python coding. SWE-bench Pro IS Python (all 12 repos: Django, Flask, matplotlib, scikit-learn, sympy, pytest). For Django bugs, Flask APIs, and multi-file Python refactors, Fable 5 is the new #1. Test all models on CodingFleet's Python Code Generator.
🆕 Claude Fable 5 — The New Python King
Anthropic's first publicly available Mythos-class model: 80.3% SWE-bench Pro — beating Opus 4.8 (69.2%) by 11.1 points. 88.0% Terminal-Bench 2.1 (#1). 94.5% GPQA Diamond. 56.8% HLE no tools. SWE-bench Pro IS Python (all 12 repos: Django, Flask, matplotlib, scikit-learn, sympy, pytest, sphinx, astropy, xarray, pylint, requests, seaborn). For Django bugs, Flask APIs, NumPy/SciPy, and multi-file Python refactors — Fable 5 is the best model ever released. See full leaderboard →
Ask a developer which benchmark tests Python coding and they'll say HumanEval. They're not wrong — but in 2026, they're not useful. Frontier models now score 91–95% on HumanEval. It's a checkbox, not a comparison tool. So where do you look instead? SWE-bench IS a Python benchmark. All 12 repositories — Django, Flask, scikit-learn, matplotlib, sympy, pytest — are Python projects. When a model fixes a Django bug on SWE-bench, it's doing Python. Here's the real ranking. Generate Python code with all these models on CodingFleet's Python Code Generator or use the Python Code Converter to port between frameworks.
📊 Key Findings
- Claude Fable 5 is the new Python king. 80.3% SWE-bench Pro — 11.1 points ahead of Opus 4.8. The best Python bug-fixer ever released.
- Claude Opus 4.8 is now the budget alternative. 69.2% Pro at $25/1M. Half the price of Fable 5 for high-volume Python work.
- DeepSeek V4 Pro wins competitive programming. 93.5% LiveCodeBench, 3206 Codeforces. Best for algorithmic Python.
- HumanEval is dead for comparison. Every top model scores 91–95%.
- Kimi K2.6 is the open-weight value king. 58.6% Pro at $4.00/1M.
All models analyzed here are available on CodingFleet. Test your Python code with each model →
Why HumanEval Is No Longer Useful
HumanEval — 164 Python function-writing tasks created by OpenAI in 2021 — was the right benchmark for its era. In 2026, it's a checkbox:
| Metric | HumanEval | SWE-bench Pro | SciCode |
|---|---|---|---|
| Task | Write one function from a docstring | Fix a real bug in a production codebase | Solve a scientific computing problem |
| Context | Zero — isolated function stub | Full repository (thousands of files) | Domain knowledge required |
| Top model score | 95% (GPT-5.3 Codex) | 80.3% (Claude Fable 5) | 26.2% (Gemini 3.1 Pro) |
| Verdict | Saturated. Useless. | The Python benchmark. | Scientific Python. |
SWE-bench IS Python: Here's the Proof
SWE-bench Verified is composed entirely of Python repositories: Django (46%), SymPy (15%), Sphinx (9%), Matplotlib (7%), scikit-learn (6%), Astropy + xarray (9%), pytest (4%), plus pylint, requests, seaborn, and Flask. These are real Python codebases with thousands of files.
SWE-bench Pro: The Definitive Python Bug-Fixing Ranking
| Model | SWE-bench Pro | Source |
|---|---|---|
| 🆕 Claude Fable 5 | 80.3% | Anthropic Announcement (Jun 9, 2026) |
| Claude Opus 4.8 | 69.2% | Anthropic system card |
| Kimi K2.6 | 58.6% | DeepSeek V4 Pro comparison table |
| GPT-5.5 | 58.6% | OpenAI announcement |
| DeepSeek V4 Pro | 55.4% | HuggingFace model card |
| Gemini 3.5 Flash | 55.1% | Google announcement |
Competitive Programming & Algorithmic Python
| Metric | DeepSeek V4 Pro | Kimi K2.6 | GPT-5.4 |
|---|---|---|---|
| LiveCodeBench v6 | 93.5% | 89.6% | 70.8% |
| Codeforces Rating | 3206 | — | 3168 |
The Cost of Python Coding
| Model | SWE-bench Pro | Output $/1M | $ per Pro Point |
|---|---|---|---|
| Claude Fable 5 | 80.3% | $50.00 | $0.623 |
| Claude Opus 4.8 | 69.2% | $25.00 | $0.361 |
| DeepSeek V4 Pro | 55.4% | $0.87 | $0.016 |
| GPT-5.5 | 58.6% | $30.00 | $0.512 |
Which Model for Which Python Workload?
| Python Workload | Best Model | Budget Alternative |
|---|---|---|
| Django / Flask backend bugs | Claude Fable 5 | Claude Opus 4.8 ($25) |
| NumPy / SciPy / Pandas | Claude Fable 5 | Gemini 3.1 Pro ($12) |
| Competitive programming | Claude Fable 5 | DeepSeek V4 Pro ($0.87) |
| Cost-sensitive at scale | DeepSeek V4 Pro ($0.87/1M) | Kimi K2.6 ($4.00) |
Updated June 9, 2026. Claude Fable 5 (80.3% Pro) is the undisputed Python king across all workloads. Opus 4.8 becomes the budget alternative. DeepSeek V4 Pro remains best for cost-sensitive Python at scale.