Claude Haiku 4.5 vs GPT-5.1 Codex
Side-by-side benchmark comparison across coding, math, reasoning, speed, and pricing.
GPT-5.1 Codex by OpenAI wins on 10 of 15 benchmarks against Claude Haiku 4.5 by Anthropic, which leads on 5. This head-to-head comparison covers coding, math, reasoning, speed, and pricing metrics from our benchmark data.
Category-by-Category Breakdown
General Intelligence: In general intelligence, GPT-5.1 Codex scores 1395 on Chatbot Arena ELO compared to Claude Haiku 4.5's 1220, while GPT-5.1 Codex scores 82.0% on MMLU-Pro compared to Claude Haiku 4.5's 65.0%.
Coding: In coding, GPT-5.1 Codex scores 96.0% on HumanEval+ compared to Claude Haiku 4.5's 78.0%, while GPT-5.1 Codex scores 78.0% on SWE-bench Verified compared to Claude Haiku 4.5's 30.0%, while GPT-5.1 Codex scores 85.0% on LiveCodeBench compared to Claude Haiku 4.5's 35.0%.
Math: In math, GPT-5.1 Codex scores 85.0% on MATH compared to Claude Haiku 4.5's 70.0%, while GPT-5.1 Codex scores 95.0% on GSM8K compared to Claude Haiku 4.5's 88.0%.
Reasoning: In reasoning, GPT-5.1 Codex scores 65.0% on GPQA Diamond compared to Claude Haiku 4.5's 40.0%, while GPT-5.1 Codex scores 52.0% on ARC-AGI compared to Claude Haiku 4.5's 18.0%.
Context: In context, GPT-5.1 Codex scores 400K on Context Length compared to Claude Haiku 4.5's 200K.
Pricing Comparison
Claude Haiku 4.5 costs $1.0/1M input tokens and $5.0/1M output tokens, while GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output. Claude Haiku 4.5 is the more affordable option for API usage.
Speed Comparison
Claude Haiku 4.5 generates output at 180 tok/s compared to GPT-5.1 Codex's 85 tok/s, and the time to first token is 120 ms for Claude Haiku 4.5 versus 400 ms for GPT-5.1 Codex. Claude Haiku 4.5 delivers faster throughput.
Verdict
For developers prioritizing affordability and speed, Claude Haiku 4.5 has the edge. For those who value coding and general intelligence and math, GPT-5.1 Codex is the stronger choice.
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Claude Haiku 4.5 vs GPT-5.1 Codex — FAQ
Which is better, Claude Haiku 4.5 or GPT-5.1 Codex?
GPT-5.1 Codex wins on more benchmarks overall (10 vs 5). However, the best choice depends on your specific needs — each model excels in different areas.
How does Claude Haiku 4.5 compare to GPT-5.1 Codex for coding?
GPT-5.1 Codex is better for coding, scoring 78.0% on SWE-bench Verified compared to 30.0%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is Claude Haiku 4.5 cheaper than GPT-5.1 Codex?
Yes, Claude Haiku 4.5 is cheaper. Claude Haiku 4.5 costs $1.0/1M input and $5.0/1M output tokens. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens.
Which is faster, Claude Haiku 4.5 or GPT-5.1 Codex?
Claude Haiku 4.5 is faster, generating output at 180 tok/s compared to 85 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the Claude Haiku 4.5 vs GPT-5.1 Codex comparison cover?
This comparison covers 15 benchmarks including Chatbot Arena ELO, MMLU-Pro, HumanEval+, MATH, GPQA Diamond, SWE-bench Verified, Output Speed, LiveCodeBench, and more. Metrics span general intelligence, coding, math, reasoning, speed, and cost categories.