Side-by-side benchmark comparison across agentic, coding, multimodal, knowledge, reasoning, and math workflows.
GPT-5.3 Instant has the cleaner overall profile here, landing at 87 versus 84. It is a real lead, but still close enough that category-level strengths matter more than the headline number.
GPT-5.3 Instant's sharpest advantage is in knowledge, where it averages 80.8 against 72.6. The single biggest benchmark swing on the page is HLE, 44 to 27. GPT-5.1-Codex-Max does hit back in agentic, so the answer changes if that is the part of the workload you care about most.
GPT-5.3 Instant is also the more expensive model on tokens at $1.75 input / $14.00 output per 1M tokens, versus $2.00 input / $8.00 output per 1M tokens for GPT-5.1-Codex-Max. GPT-5.1-Codex-Max gives you the larger context window at 400K, compared with 128K for GPT-5.3 Instant.
Pick GPT-5.3 Instant if you want the stronger benchmark profile. GPT-5.1-Codex-Max only becomes the better choice if agentic is the priority or you want the cheaper token bill.
GPT-5.3 Instant
82.9
GPT-5.1-Codex-Max
86
GPT-5.3 Instant
78.7
GPT-5.1-Codex-Max
75.5
GPT-5.3 Instant
95
GPT-5.1-Codex-Max
88.2
GPT-5.3 Instant
94.2
GPT-5.1-Codex-Max
92.1
GPT-5.3 Instant
80.8
GPT-5.1-Codex-Max
72.6
GPT-5.3 Instant
96
GPT-5.1-Codex-Max
91
GPT-5.3 Instant
93.4
GPT-5.1-Codex-Max
87.7
GPT-5.3 Instant
97.2
GPT-5.1-Codex-Max
94.9
GPT-5.3 Instant is ahead overall, 87 to 84. The biggest single separator in this matchup is HLE, where the scores are 44 and 27.
GPT-5.3 Instant has the edge for knowledge tasks in this comparison, averaging 80.8 versus 72.6. Inside this category, HLE is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for coding in this comparison, averaging 78.7 versus 75.5. Inside this category, LiveCodeBench is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for math in this comparison, averaging 97.2 versus 94.9. Inside this category, MATH-500 is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for reasoning in this comparison, averaging 94.2 versus 92.1. Inside this category, BBH is the benchmark that creates the most daylight between them.
GPT-5.1-Codex-Max has the edge for agentic tasks in this comparison, averaging 86 versus 82.9. Inside this category, Terminal-Bench 2.0 is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for multimodal and grounded tasks in this comparison, averaging 95 versus 88.2. Inside this category, MMMU-Pro is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for instruction following in this comparison, averaging 96 versus 91. Inside this category, IFEval is the benchmark that creates the most daylight between them.
GPT-5.3 Instant has the edge for multilingual tasks in this comparison, averaging 93.4 versus 87.7. Inside this category, MGSM is the benchmark that creates the most daylight between them.
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