Open-source coding benchmark

Benchmarking models
on real engineering work.

Real engineering tasks, from rebuilding retired legacy binaries to merged open-source pull requests, graded by deterministic hidden tests.

vulcanbench: suite: v1-micro · sandbox: docker · network: off

The harness, live: an actual v1-micro run on Claude Sonnet 5 (low): 26 sandboxed tasks, graded by hidden tests, 25 pass at $0.82 total.

Benchmarking what matters to engineering teams: accuracy, token use, time, and cost, all on real engineering tasks, no puzzles, no math problems.

Hi, I'm Morgan. I built VulcanBench to help my own team pick models for real engineering work, measuring not just accuracy but token use, cost and time, with open-source harnesses and published evidence. Why I started VulcanBench →

Live long and benchmark 🖖

What every comparison makes clear.

01

Suite-specific scoring

Functional outcomes come from deterministic tests. Frontier v4 adds lint and complexity checks, a security scan and 33% Code quality from a calibrated two-model panel that never includes the graded model’s own lab.

02

Disclosed evidence

Reports identify tasks, models, harnesses, fallbacks and audit limits. Post-cutoff dates and source hashes alone cannot prove training-data absence or rule out prohibited access.

03

Economics as a result

Cost, wall-clock time, agent steps, and tokens are recorded alongside accuracy. When correctness converges, efficiency is the signal.

Latest reports.

Suitev4
Claude Fable 5.2 across every effort level
115 Claude Code runs of Claude Fable 5.2 at all five effort levels, every run solved, with Code quality at 33% judged by Muse Spark 1.3 and GPT-6.1 Sol. Combined score 91.92, 92.25, 92.76, 93.25 and 93.85 from Low to Max (n=23 at every level), first on the board at every level; $1.72 to $10.88 and 4.3 to 37.1 minutes a task.
November 13, 2026 · 23 tasks · 115 runs · VulcanBench Frontier v4 · Code quality protocol v3.30.2 and v3.30.3
→
Suitev4
GPT-6.1 Terra across every effort level
Rises from 74.95 at Low to 90.00 at Max, where it passes all 23 tasks, at $0.11 to $0.36 a task.
October 30, 2026 · 23 tasks · 115 runs · VulcanBench Frontier v4 · Code quality protocol v3.29
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Suitev4
Reflection Beam across every effort level
Scores 39.51 to 64.72 on judged runs and passes at most 6 of 23 tasks; Reflection publishes no price.
October 27, 2026 · 23 tasks · 115 runs · VulcanBench Frontier v4 · Code quality protocol v3.28
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Suitev4
DeepSeek V4.1 Flash across every effort level
Flat at 88.36 to 88.65 from Low to Max, at about a fifth of GPT-6.1 Sol’s cost per task.
October 23, 2026 · 23 tasks · 69 runs · VulcanBench Frontier v4 · Code quality protocol v3.27
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Suitev4
Muse Wonder Full across every effort level
Scores 86.95 to 88.36 across all five levels, best at Max, judged by Claude Opus 5.5 and GPT-6.1 Sol in place of the usual panel.
October 17, 2026, updated November 4 · 23 tasks · 115 runs · VulcanBench Frontier v4 · Code quality protocol v3.26
→

Measure your own stack.

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