C# code review: which models catch the bugs

Of the 17 models ranked on C# code, Claude Opus 5.5 caught the most known bugs: 100%. 10 of the other 16 models have 95% intervals that overlap its own. Gemini 3.5 Flash-Lite caught the fewest, 0%. Together they caught 51% of known bugs in C# code, against 60% for the same 17 across the whole benchmark.

Updated 2026-11-04Full leaderboard Methodology

Results

Known defects caught, with 95% intervals. The tick is the model's recall over every bug.

C# code review: which models catch the bugs
Model	Caught here	Every bug	Difference
Claude Opus 5.5	100%	90%	+10 pts
GPT-6.1 Sol	89%[67%–100%]	89%	0 pts
Gemini 4 Argon	89%[67%–100%]	82%	+7 pts
Gemini 3.8 Flash	78%[33%–100%]	68%	+10 pts
Claude Haiku 5.5	67%[0%–100%]	64%	+3 pts
DeepSeek V4 Pro (Workers AI)	59%[0%–100%]	54%	+5 pts
Claude Sonnet 5.5	56%[0%–100%]	77%	−21 pts
GPT-5.6 Sol	56%[0%–100%]	72%	−16 pts
GPT-6 Luna	56%[0%–100%]	67%	−11 pts
Gemini 3.1 Pro	56%[0%–100%]	67%	−11 pts
GLM-5.3 (Workers AI)	48%[0%–78%]	61%	−13 pts
GPT-OSS 120B (Workers AI)	41%[0%–100%]	40%	+1 pt
GLM-5.3 Flash (Workers AI)	30%[0%–67%]	61%	−31 pts
DeepSeek V4 Flash (Workers AI)	22%[0%–67%]	49%	−27 pts
Kimi K2.7 Code (Workers AI)	19%[0%–50%]	38%	−19 pts
Gemma 4 26B A4B (Workers AI)	7%[0%–22%]	26%	−19 pts
Gemini 3.5 Flash-Lite	0%	11%	−11 pts

Against the rest of the benchmark

C# was the third-hardest of the 12 languages for these models.

Claude Opus 5.5 gains the most here: 100%, against 90% over every bug.

GLM-5.3 Flash drops the most: 30%, against 61% over every bug.

A test PR that split the models

The change “fix(serialization): cap codec allocations” in dotnet/orleans, a change of 100 to 300 lines that landed in August 2026, introduced a logic bug that a later upstream commit fixed.

Claude Opus 5.5, GPT-6.1 Sol, Gemini 4 Argon and Gemini 3.8 Flash caught it; Claude Sonnet 5.5, GPT-5.6 Sol, GPT-6 Luna, Claude Haiku 5.5, Gemini 3.1 Pro, GLM-5.3 Flash, GLM-5.3, DeepSeek V4 Pro (Workers AI), DeepSeek V4 Flash (Workers AI), GPT-OSS 120B (Workers AI), Kimi K2.7 Code (Workers AI), Gemma 4 26B A4B and Gemini 3.5 Flash-Lite missed it.