Novel compiler task (Anthropic)
Agents build a compiler for an unusual programming language from a specification and test cases.
In-house Anthropic evaluation. The tasks are not public.
- Made by
- Anthropic
- Released
- May 2025
- Kind
- Machine learning engineering
- Level
- Expert
- Scored
- Checked automatically
- Answers
- Code
- Tasks
- Kept private
- Strongest model tested
- Claude Opus 5 #10 on the capability index
- Last in a system card
- July 2026
- Last model added
- July 2026
Claude Opus 5 leads with 80.9% among models released by July 2026
Best score per model as labs report them in their own cards. Labs pick their own settings, so these compare less cleanly than independent runs.
The newest model with a score here came out in July 2026, and nobody has reported a newer one. Among the 20 highest-ranked models on the capability index, these have no score yet:
- Claude Fable 5.2
-
Gemini 4 Carbon - GPT-6 Astra
- Claude Opus 5.5
- and 15 more
- 1 Claude Opus 5 80.9%
- 2 Claude Mythos Preview 77.2%
- 3 Claude Sonnet 5 76.1%
- 4 Claude Opus 4.7 71.1%
Source: Labs’ model cards
| # | Model | Score | Setting | Date | Source |
|---|---|---|---|---|---|
| 1 | Claude Opus 5 | 80.9% | Jul 2026 | Lab model card | |
| 2 | Claude Mythos Preview | 77.2% | Apr 2026 | Lab model card | |
| 3 | Claude Sonnet 5 | 76.1% | Jun 2026 | Lab model card | |
| 4 | Claude Opus 4.7 | 71.1% | Apr 2026 | Lab model card |
2 models have held number one in labs’ own numbers since its release in May 2025
Lab claims count from the day the card came out, independent runs from the model’s release.
Source: Labs’ model cards
Scores over time
All the scores we have, one dot each, so a model tested at several settings appears more than once.
Source: Labs’ model cards
Labs report it only in system cards
We read the headline results of 522 launch posts from 52 labs, and none of them list this benchmark. Some system cards do, below.
11 system cards report it, from 1 lab
Besides launch posts, we read the system cards, model cards and technical reports labs publish with a release. They report far more, including safety and frontier-risk tests.
| Date | Document | Score | As the document writes it | Section |
|---|---|---|---|---|
| Jul 24, 2026 | Claude Opus 5 system card | 80.9 | Novel Compiler, pass rate on complex tests (Table 2.3.5.A) | AI R&D risk |
| Jun 30, 2026 | Claude Sonnet 5 system card | 76.1 | Novel Compiler, pass rate on complex tests 76.1% (Table 2.3.3.A) | AI R&D risk |
| Apr 16, 2026 | Claude Opus 4.7 system card | 71.1 | Novel Compiler, pass rate on complex tests (Table 2.3.4.A) | AI R&D risk |
| Apr 7, 2026 | Claude Mythos Preview system card | 77.2 | Novel Compiler, pass rate on complex tests 77.2% (Table 2.3.3.A) | AI R&D risk |
| Feb 17, 2026 | Claude Sonnet 4.6 system card | Novel compiler, 93.7 of basic tests and 67.27 of complex tests passed, no overall (6.3.3.6) | AI R&D risk | |
| Feb 5, 2026 | Claude Opus 4.6 system card | Novel compiler, two test sets with no overall: 98.2% of basic tests and 65.83% of complex tests passed, threshold 90% on complex tests (8.3.3.6) | AI R&D risk | |
| Nov 24, 2025 | Claude Opus 4.5 system card | Novel compiler, two test sets with no overall: 93.7% of basic tests and 69.37% of complex tests passed, threshold 90% on complex tests (7.3.2.6) | AI R&D risk | |
| Sep 29, 2025 | Claude Sonnet 4.5 system card | Novel compiler, two test sets with no overall: mean pass rate 81.7% on basic tests and 29.7% on advanced tests, threshold 90% (9.3.3.6) | AI R&D risk | |
| Aug 5, 2025 | Claude Opus 4.1 system card addendum | Novel compiler, no overall: mean pass rate 74.4% on basic tests and 6.81% on advanced tests (6.4.1) | AI R&D risk | |
| May 22, 2025 | Claude Sonnet 4 system card | Novel compiler, no overall: mean pass rate 50.00% on basic tests and 17.08% on advanced tests. The 7.3 summary says 52.96% on basic tests (7.3.3.6) | AI R&D risk | |
| May 22, 2025 | Claude Opus 4 system card | Novel compiler, no overall: mean pass rate 64.44% on basic tests and 9.44% on advanced tests (7.3.3.6) | AI R&D risk |
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