Noometry

Model comparison

Claude Opus 5.5 vs GPT-5.1-Codex-mini

Claude Opus 5.5 has enough public results to be ranked (#3); GPT-5.1-Codex-mini does not yet, so treat this comparison as directional.

Last verified . 1 shared benchmarks.

Claude Opus 5.5 Anthropic

68.6

Rank #3 Confirmed

GPT-5.1-Codex-mini OpenAI

37.3

Unranked Sparse

Summary

  • They share 1 benchmark with published results for both. Claude Opus 5.5 scores higher in 2 categories and GPT-5.1-Codex-mini in 0 categories; 2 gaps are clear of the uncertainty.
  • The widest gap is in coding, where Claude Opus 5.5 leads 71.9 to 31.6.
  • GPT-5.1-Codex-mini is cheaper at $0.25 / $2 per million input/output tokens, against $4 / $20 for Claude Opus 5.5.
  • Claude Opus 5.5 accepts more context: 1M tokens versus 400K.

Side by side

Claude Opus 5.5GPT-5.1-Codex-mini
ProviderAnthropicOpenAI
Noometry Index68.637.3
Released2026-09-222025-11-12
WeightsProprietaryProprietary
Context window1M400K
Max output128K128K
Input $ / M tokens$4$0.25
Output $ / M tokens$20$2
Results tracked442

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Category by category

Coding Claude Opus 5.5 leads

Claude Opus 5.5: 71.9 (#3), GPT-5.1-Codex-mini: 31.6

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
LMArena WebDev18131244
FrontierCode54.6%—
CursorBench57.8%—
FrontierSWE62.3%—
SciCode66.9%—
LMArena Coding1547—
MirrorCode77.4%—
ALE-Bench2,147—

Agentic & Tool Use Claude Opus 5.5 leads

Claude Opus 5.5: 45.3 (#15), GPT-5.1-Codex-mini: 38.5

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
Terminal-Bench—61.6%
APEX-Agents73.5%—
GDP.pdf30.6%—
Vending-Bench 29,235—

Reasoning Not comparable

Claude Opus 5.5: 80.2 (#3), GPT-5.1-Codex-mini: —

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
ARC-AGI-293.3%—
NYT Connections (extended)88.5%—
ARC-AGI-198.5%—
CritPt31.7%—
EBR-Bench71.4%—
LMArena Hard Prompts1535—
Mystery Game Puzzles71%—
DTBench98.9%—
LMCA68.2%—
Epoch Capabilities Index167.33—

Math Not comparable

Claude Opus 5.5: 91.8 (#3), GPT-5.1-Codex-mini: —

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
FrontierMath (Tiers 1-3)91.2%—
FrontierMath Tier 495%—
OTIS Mock AIME 2024-2025100%—
ProofBench100%—
LMArena Math1506—
FrontierMath Erdős2.9%—

Knowledge Not comparable

Claude Opus 5.5: 66.4 (#10), GPT-5.1-Codex-mini: —

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
GPQA Diamond90.6%—
SimpleQA Verified72.2%—
LMArena Expert1547—

Multimodal Not comparable

Claude Opus 5.5: 57.8 (#1), GPT-5.1-Codex-mini: —

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
LMArena Vision1321—
Blueprint-Bench 251.2%—
Furniture Assembly83.3%—

Multilingual Not comparable

Claude Opus 5.5: 59.1 (#2), GPT-5.1-Codex-mini: —

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
LMArena Non-English1507—
LMArena Chinese1588—
LMArena French1514—
LMArena Russian1520—
LMArena Spanish1507—

Instruction Following Not comparable

Claude Opus 5.5: 80.0 (#3), GPT-5.1-Codex-mini: —

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
LMArena Instruction Following1537—

Long Context Not comparable

Claude Opus 5.5: 47.1 (#19), GPT-5.1-Codex-mini: —

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
LMArena Longer Query1532—

Writing & Preference Not comparable

Claude Opus 5.5: 78.2 (#3), GPT-5.1-Codex-mini: —

BenchmarkClaude Opus 5.5GPT-5.1-Codex-mini
LMArena Text1515—
LMArena Creative Writing1533—
EQ-Bench Creative Writing2050—
LMArena Multi-Turn1499—

Frequently asked questions

Is Claude Opus 5.5 better than GPT-5.1-Codex-mini?

Claude Opus 5.5 has enough public results to be ranked (#3); GPT-5.1-Codex-mini does not yet, so treat this comparison as directional.

Which is cheaper, Claude Opus 5.5 or GPT-5.1-Codex-mini?

GPT-5.1-Codex-mini is cheaper. It lists at $0.25 per million input tokens and $2 per million output tokens; Claude Opus 5.5 lists at $4 and $20.

Is Claude Opus 5.5 or GPT-5.1-Codex-mini better for coding?

Claude Opus 5.5 scores higher on coding benchmarks: 71.9 versus 31.6 in the Noometry coding category.

Which has the bigger context window?

Claude Opus 5.5 does, with 1M tokens against 400K.

How many benchmarks do Claude Opus 5.5 and GPT-5.1-Codex-mini share?

1 benchmark has published results for both models. Claude Opus 5.5 has 44 scored results on Noometry and GPT-5.1-Codex-mini has 2.

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