Claude Fable 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 5 of 8 benchmarks against Claude Fable 5 by Anthropic, which leads on 3. This head-to-head comparison covers coding, math, reasoning, speed, and pricing metrics from our benchmark data.
Category-by-Category Breakdown
Coding: In coding, Claude Fable 5 scores 95.0% on SWE-bench Verified compared to GPT-5.1 Codex's 78.0%.
Reasoning: In reasoning, Claude Fable 5 scores 92.6% on GPQA Diamond compared to GPT-5.1 Codex's 65.0%.
Context: In context, Claude Fable 5 scores 1.0M on Context Length compared to GPT-5.1 Codex's 400K.
Pricing Comparison
Claude Fable 5 costs $10.0/1M input tokens and $50.0/1M output tokens, while GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output. GPT-5.1 Codex is the more affordable option for API usage.
Speed Comparison
Claude Fable 5 generates output at 60 tok/s compared to GPT-5.1 Codex's 85 tok/s, and the time to first token is 81680 ms for Claude Fable 5 versus 400 ms for GPT-5.1 Codex. GPT-5.1 Codex delivers faster throughput.
Verdict
For developers prioritizing coding, Claude Fable 5 has the edge. For those who value affordability and speed, GPT-5.1 Codex is the stronger choice.
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Claude Fable 5 vs GPT-5.1 Codex — FAQ
Which is better, Claude Fable 5 or GPT-5.1 Codex?
GPT-5.1 Codex wins on more benchmarks overall (5 vs 3). However, the best choice depends on your specific needs — each model excels in different areas.
How does Claude Fable 5 compare to GPT-5.1 Codex for coding?
Claude Fable 5 is better for coding, scoring 95.0% on SWE-bench Verified compared to 78.0%. SWE-bench tests real-world software engineering by resolving actual GitHub issues.
Is Claude Fable 5 cheaper than GPT-5.1 Codex?
Yes, GPT-5.1 Codex is cheaper. Claude Fable 5 costs $10.0/1M input and $50.0/1M output tokens. GPT-5.1 Codex costs $1.3/1M input and $10.0/1M output tokens.
Which is faster, Claude Fable 5 or GPT-5.1 Codex?
GPT-5.1 Codex is faster, generating output at 85 tok/s compared to 60 tok/s. Faster output speed means shorter wait times for API responses.
What benchmarks does the Claude Fable 5 vs GPT-5.1 Codex comparison cover?
This comparison covers 8 benchmarks including GPQA Diamond, SWE-bench Verified, Output Speed, Time to First Token, Input Cost, Output Cost, Context Length, Cached Input Cost. Metrics span general intelligence, coding, math, reasoning, speed, and cost categories.