Model comparison
Claude Haiku 4.5 vs GPT-5.1-Codex
Claude Haiku 4.5 and GPT-5.1-Codex score almost the same on the Noometry Index (39.5 vs 38.6), so choose on price, context window or the category you care about most.
Last verified . 4 shared benchmarks.
Summary
- They share 4 benchmarks with published results for both. Claude Haiku 4.5 scores higher in 2 categories and GPT-5.1-Codex in 1 category; 3 gaps are clear of the uncertainty.
- The widest gap is in math, where Claude Haiku 4.5 leads 44.9 to 30.3.
- The biggest single-benchmark swing is Terminal-Bench: 35.5% for Claude Haiku 4.5 and 60.4% for GPT-5.1-Codex.
- Claude Haiku 4.5 is cheaper at $1 / $5 per million input/output tokens, against $1.25 / $10 for GPT-5.1-Codex.
- GPT-5.1-Codex accepts more context: 400K tokens versus 200K.
Side by side
| Claude Haiku 4.5 | GPT-5.1-Codex | |
|---|---|---|
| Provider | Anthropic | OpenAI |
| Noometry Index | 39.5 | 38.6 |
| Released | 2025-10-15 | 2025-11-12 |
| Weights | Proprietary | Proprietary |
| Context window | 200K | 400K |
| Max output | 64K | 128K |
| Input $ / M tokens | $1 | $1.25 |
| Output $ / M tokens | $5 | $10 |
| Results tracked | 53 | 6 |
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Category by category
Coding Claude Haiku 4.5 leads
Claude Haiku 4.5: 44.0 (#78), GPT-5.1-Codex: 41.9 (#116)
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| SWE-bench Verified (bash only) | 66.6% | 66% |
| LMArena WebDev | 1330 | 1337 |
| ALE-Bench | 653.48 | 1,245 |
| SWE-bench Multilingual | 64.7% | — |
| SciCode | 43.3% | — |
| WeirdML | 45.4% | — |
| LMArena Coding | 1453 | — |
Agentic & Tool Use GPT-5.1-Codex leads
Claude Haiku 4.5: 33.6 (#52), GPT-5.1-Codex: 38.0 (#33)
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| Terminal-Bench | 35.5% | 60.4% |
| Berkeley Function Calling Leaderboard | 68.7% | — |
| DeepResearch Bench | 45.5% | — |
| BALROG | 31.2% | — |
| ExploitBench | 13.7% | — |
| METR Time Horizons | — | 70.8% |
| Vending-Bench 2 | 458.89 | — |
Reasoning Not comparable
Claude Haiku 4.5: 15.1 (#320), GPT-5.1-Codex: —
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| ARC-AGI-2 | 4% | — |
| NYT Connections (extended) | 14.3% | — |
| ARC-AGI-1 | 47.7% | — |
| CritPt | 0% | — |
| Chess Puzzles | 8% | — |
| LMArena Hard Prompts | 1420 | — |
| DTBench | 73.6% | — |
| LMCA | 30.9% | — |
| Epoch Capabilities Index | 142.41 | — |
| ForecastBench | 61.4 | — |
Math Claude Haiku 4.5 leads
Claude Haiku 4.5: 44.9 (#78), GPT-5.1-Codex: 30.3 (#235)
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| OTIS Mock AIME 2024-2025 | 66.7% | — |
| ProofBench | — | 9% |
| Omni-MATH | 56.1% | — |
| LMArena Math | 1396 | — |
| MATH Level 5 | 96.4% | — |
| FrontierMath (Feb 2025 set) | 5.9% | — |
| FrontierMath Tier 4 (v1) | 2.1% | — |
Knowledge Not comparable
Claude Haiku 4.5: 37.7 (#153), GPT-5.1-Codex: —
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| GPQA Diamond | 71.2% | — |
| SimpleQA Verified | 13.2% | — |
| MMLU-Pro | 77.7% | — |
| Vectara Hallucination Rate | 9.8% | — |
| GPQA (HELM) | 60.5% | — |
| LMArena Expert | 1442 | — |
Multimodal Not comparable
Claude Haiku 4.5: 26.8 (#118), GPT-5.1-Codex: —
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| Blueprint-Bench 2 | 0% | — |
| LMArena Document | 1420 | — |
Multilingual Not comparable
Claude Haiku 4.5: 49.9 (#129), GPT-5.1-Codex: —
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Non-English | 1377 | — |
| LMArena Chinese | 1417 | — |
| LMArena French | 1408 | — |
| LMArena German | 1375 | — |
| LMArena Japanese | 1339 | — |
| LMArena Korean | 1347 | — |
| LMArena Russian | 1381 | — |
| LMArena Spanish | 1420 | — |
Instruction Following Not comparable
Claude Haiku 4.5: 71.4 (#149), GPT-5.1-Codex: —
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| IFEval | 80.1% | — |
| LMArena Instruction Following | 1414 | — |
Long Context Not comparable
Claude Haiku 4.5: 43.6 (#92), GPT-5.1-Codex: —
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Longer Query | 1427 | — |
Writing & Preference Not comparable
Claude Haiku 4.5: 57.9 (#123), GPT-5.1-Codex: —
| Benchmark | Claude Haiku 4.5 | GPT-5.1-Codex |
|---|---|---|
| LMArena Text | 1396 | — |
| LMArena Creative Writing | 1372 | — |
| WildBench | 83.9% | — |
| EQ-Bench 4 | 1064 | — |
| LMArena Multi-Turn | 1409 | — |
Frequently asked questions
Is Claude Haiku 4.5 better than GPT-5.1-Codex?
Claude Haiku 4.5 and GPT-5.1-Codex score almost the same on the Noometry Index (39.5 vs 38.6), so choose on price, context window or the category you care about most.
Which is cheaper, Claude Haiku 4.5 or GPT-5.1-Codex?
Claude Haiku 4.5 is cheaper. It lists at $1 per million input tokens and $5 per million output tokens; GPT-5.1-Codex lists at $1.25 and $10.
Is Claude Haiku 4.5 or GPT-5.1-Codex better for coding?
Claude Haiku 4.5 scores higher on coding benchmarks: 44.0 versus 41.9 in the Noometry coding category.
Which has the bigger context window?
GPT-5.1-Codex does, with 400K tokens against 200K.
How many benchmarks do Claude Haiku 4.5 and GPT-5.1-Codex share?
4 benchmarks have published results for both models. Claude Haiku 4.5 has 53 scored results on Noometry and GPT-5.1-Codex has 6.